Relationship of Maastrichtian–Thanetian benthic foraminiferal species diversity, palaeooxygenation and palaeoproductivity in shallow waters of Western Desert, Egypt

doi:10.21203/rs.3.rs-2213323/v1

Download PDF

Research Article

Relationship of Maastrichtian–Thanetian benthic foraminiferal species diversity, palaeooxygenation and palaeoproductivity in shallow waters of Western Desert, Egypt

https://doi.org/10.21203/rs.3.rs-2213323/v1

This work is licensed under a CC BY 4.0 License

Journal Publication

published 01 Feb, 2023

Read the published version in Geo-Marine Letters →

You are reading this latest preprint version

Benthic foraminiferal analysis (315 samples, 16,271 specimens) of the shallow water (< 100 m) Maastrichtian–Thanetian rocks from the Dakhla Oasis (Western Desert, Egypt) were studied to infer the inter–relationships between species diversity, palaeooxygenation, palaeoproductivity, and palaeodepth and changes at the Cretaceous–Paleogene (K/Pg) boundary. Positive and significant correlations are noted between these proxies, suggesting a well–oxygenated oligotrophic environment. However, a brief interval (mid– lower Maastrichtian) of increased palaeoproductivity with reduced diversity and oxygenation (ventilation) is noted (a characteristic of mesotrophic–eutrophic settings) that coincides with very shallow waters during a Highstand System Tract (HST), and dominated by the dysoxic agglutinated species Ammobaculites khargaensis. The diversity index, Fisher’s α (< 5) and paleodepth proxy (foraminiferal wall structure types) also suggests a shallow neritic (largely littoral) depth for the entire study interval. At the bottom of the study section (Planktic Foraminiferal Zones CF8b-CF7), species diversity, palaeooxygenation, and palaeoproductivity are high. From the K/Pg boundary to the post K/Pg period, these variables are low and fluctuating with moderate species dominance. According to the available data, a 40% total extinction rate was seen after the K/Pg hiatus, with 38% of agglutinated species and 40% of calcareous extinct species. The period immediately following the K/Pg boundary is characterised by increased basinal ventilation and decreased palaeoproductivity, which are attributable to changes in sea level and concurrent regional subsidence. However, as stable as the community structure was (at or just after K/Pg), the changes in species composition (assemblage) were dramatic marked by a change from a pre–K/Pg agglutinated–dominated fauna (Haplophragmoides–Ammobaculites) to a post–K/Pg calcareous assemblage (Cibicodoides–Cibicides–Anomalinoides).

Egypt

Maastrichtian–Thanetian

Species diversity

Palaeooxygenation

Palaeoproductivity

Palaeodepth

Benthic foraminifera

The benthic foraminiferal species assemblage, distribution, and community structure are a result of the interaction between productivity (the organic–flux to the sea floor) and pore waters and oxygenation of the bottom (Van der Zwaan et al., 1999; Jorissen et al., 2007). However, in the deep sea environment, oxygen availability is frequently and not a limiting factor, where the characteristics of individual species or assemblages (or the composition of an assemblage) are frequently good flux-indicators. In shallower waters, it is difficult to distinguish between the individual effects of oxygen and organic-flux (Van der Zwaan et al., 1999; Jorissen et al., 2007). In modern oceans, the quantity, quality and periodicity of organic–flux to the sea floor define the distribution of benthic foraminiferal fauna; although, there is still “a great deal of uncertainty about the downward flux of organic carbon” to the sea floor and the estimates of primary production (see review by Murray, 2001).

The Upper Cretaceous-Lower Paleogene interval has been extensively studied in order to better understand the response of benthic foraminifera (their vertical and spatial distribution, changes in community structure, and assemblage) to the end Cretaceous bolide impact. One of the few groups of creatures, benthic foraminifera, has been reported to have experienced no major extinction above background levels at the end of the Cretaceous (Culver, 2003), making them a good proxy for biota-based paleoenvironmental reconstructions. Hence, they have extensively been used as proxies to better understand the variability in export productivity (the flux of organic matter from the surface to the seafloor), paleooxygenation (prevailing oxic and dysoxic conditions), community structure (species diversity), assemblages and changes in their isotope signals across the K/Pg boundary (Hsü and McKenzie, 1985; Culver, 2003; d'Hondt, 2005; Alegret and Thomas, 2005; Coxall et al., 2006; Alegret, 2007; Alegret and Ortiz, 2007; Alegret and Thomas, 2009; Alegret et al., 2012). The changes in their isotope signal in all sedimentary records of the K/Pg boundary, are marked by a dramatic collapse of the carbon isotope gradients between surface and deep–sea carbonates (d'Hondt, 2005; Alegret et al., 2012), largely attributed to a long–term interruption of primary productivity or export productivity (as explained by the Strangelove Ocean and Living Ocean models; Hsü and McKenzie, 1985; d'Hondt et al., 1998; d'Hondt, 2005; Coxall et al., 2006). However, this dramatic breakdown contradicts the fact that the benthic foraminifera did not experience any major extinction during this interval (Culver, 2003; Alegret et al., 2012). Hence, an alternate explanation was put forward to explain this collapse that the extinction of the carriers of this isotope signal (the Maastrichtian calcareous nannoplankton and planktic foraminifera), were replaced by taxa with a much lighter carbon isotope signature in the early Danian (Alegret et al., 2012; Birch et al., 2012, 2016). Assessing this is beyond the resolution of the present study which restricts itself in documenting changes in benthic foraminiferal inferred palaeoproductivity, palaeooxygenation, species diversity and assemblage and their changes at the K/Pg boundary from the Maastrichtian–Thanetian succession exposed at the Dakhla Oasis (at Gharb El–Mawohb at the main escarpment; 26°01'02" N, 28°13'18"E; Western Desert, Egypt) (Fig. 1a–c). This succession provides an excellent exposure (Figs. 1d–e) and represents a transitional area between the middle to outer neritic Farafra Facies and the inner neritic Garra Al–Arbain facies (Fig. 2).

The originality of this study lies in the scarcity of comparative Upper Cretaceous-Lower Paleogene neritic (100 m) benthic foraminiferal records that document changes in palaeooxygenation, palaeoproductivity, and species diversity over a longer time period, not just from the southern Tethys margins but also globally (Culver, 2003). Those that deal with these changes tend to only do so during the K/Pg border event or are from the Tunisian regions of El Kef, Elles, and Ain Settara (Speijer and van der Zwaan, 1996; Widmark and Speijer, 1997; Li et al., 1999; Peryt et al., 2002, 2004; Coccioni and Marsili, 2007). Although these records provide a high-resolution window into changes in the benthic-pelagic coupling, they only do so across a very short K/Pg boundary. Rare records are from Egypt, but then, these (Orabi and Khalil, 2014; Farouk and Jain, 2016; Jain and Farouk, 2017), only have passing remarks with respect to changes in palaeoproductivity, palaeooxygenation, species diversity, and morphogroup analysis (Orabi and Khalil, 2014; infaunal/epifaunal analysis only) or changes at the K/Pg boundary interval. Thus, the present contribution is an attempt to bridge this gap, in addition to providing a more comprehensive analysis of the changes in the benthic ecosystem vis–à–vis the interplay of global eustasy and regional tectonics during the Upper Cretaceous–Lower Paleogene interval in Egypt.

The Western Desert, part of the northeastern continental margin of Africa (Fig. 1a–c), due to the breakup of the Pangea initiated two NW–SE trending intrashelf basins in central Egypt, namely Dakhla and Assiut; the southern and central Western Desert constitutes the Dakhla Basin (Hendriks et al., 1987; Flexer and Reyment, 1989; Dercourt et al., 1993; El–Deeb, 1995). Dakhla Oasis is located in the central Western Desert of the major sedimentary basin, the Dakhla basin (Fig. 1a). The largest oasis in Egypt's Western Desert, Dakhla Oasis is made up of an extremely thick and well-exposed Upper Cretaceous-Lower Paleogene sequence. It is distinguished by two facies types, the Nile Valley and Garra El-Arbain Facies, which reflect lateral and vertical facies variation (Issawi, 1972; Fig. 2a–b). It is located between longitudes 28°15'-29°40' E and latitudes 25°00'-26°00' N, 120 km west of the Kharga Oasis, about 300 km west of the Nile Valley, and roughly 300 km southeast of the Farafra Oasis (Fig. 1).

[INSERT HERE – FIGURE 1]

It must be noted right away that there are two competing theories on whether there was a gap (hiatus) or continuous sedimentation in Egypt based on data derived from planktonic foraminifera, benthic foraminifera, and calcareous nannofossils. Beckmann et al., (1969) stated that most sections in Egypt show a clear hiatus at the K/Pg boundary and this has been corroborated by others too in the Western Desert (Abdel–Kireem and Samir, 1995; Tantawy et al., 2001; Khalil and Al Sawy, 2014; Orabi and Khalil, 2014; Farouk and Faris, 2012; Farouk, 2016), in the Nile Valley (Faris et al., 1985), in the Eastern Desert (Scheibner et al., 2003; Galal and Kamel, 2007), and in Sinai (Ayyad et al., 2003). However, El–Bassiouni et al., (2003) and Obaidalla (2005) have advocated a continuous sedimentation. But, studies overwhelmingly suggests that the upper part of calcareous nannofossil Micula murus subzone and the earliest Danian NP1 and NP2 zones are missing (equivalent to the interval between CF2 to P1c planktonic foraminifera zones; see Farouk, 2016; Farouk and Jain, 2016). This hiatus is linked to both tectonic activity and irregular palaeotopography associated with low sedimentation rate (El–Azabi and El–Araby, 2000; Jain and Farouk, 2017). The other gap is marked by the Danian/Selandian unconformity and is associated with a sharp lithological break represented by extensive reworking of older Danian faunas (Farouk and El–Sorogy, 2015; Jain and Farouk, 2017). During the Selandian/Thanetian transition widespread changes in the pattern of sedimentation is noted (= the so–called “Velascoensis Event” by Strougo, 1986) that resulted in subaerial exposure (erosion), and coupled with global sea–level fall, resulted in the absence of the calcareous nannofossil Zone NP6 near the base of the Tarawan Formation in different parts of Egypt (Farouk, 2016). Both boundary events have been dealt with in detail by Jain and Farouk (2017) and will not be dealt further.

[INSERT HERE – FIGURE 2]

A brief mention of the barren intervals (for benthic and planktic foraminifera) noted in this study is warranted. As regards the occurrence of benthic foraminifera, samples 156 to 194 (spanning Assemblages 8–10; 8 and 10 in part; with few productive samples in between, 164, 182–184) are barren (Fig. 3). This upper Maastrichtian interval is marked by the erosive HST 2 (Fig. 3; for a more detailed sequence stratigraphic framework see Farouk and Jain, 2016; Jain and Farouk, 2017) and the near dominance of agglutinated taxa Trochammina and Ammobaculites (T. rainwateri and A. subcretaceous, respectively) with a single calcareous taxa, Insculptarenula texana. Similar assemblages dominated by agglutinated taxa with an extremely small calcareous component have been documented in brackish to littoral settings (Nagy et al., 1990, 2010; Farouk and Jain, 2016; Jain and Farouk, 2017). Such shallow depths would explain the absence of planktic foraminifera as also during Assemblages 2 to 7 (see Fig. 3) that are also marked by impoverished benthic foraminiferal counts (see also Farouk and Jain, 2016; Jain and Farouk, 2017). A concomitant regional uplift has also been well–documented for this interval (see El–Azabi and El–Araby, 2000; Tantawy et al., 2001).

[INSERT HERE – FIGURE 3]

Three previous studies have been conducted on the same section, Farouk and Jain (2016, 2017) and Jain and Farouk (2017). Farouk and Jain (2016, 2017) have used the benthic foraminiferal abundance pattern to build 19 assemblages (13 and 6, respectively; the framework for the present study) to construct a sea level curve for the Maastrichtian–Thanetian duration vis–à–vis sequence stratigraphy. Jain and Farouk (2017) extended this study and used only the distribution (abundance pattern) of agglutinated benthic foraminifera and analyzed diversity fluctuations for the prevailing Maastrichtian–Thanetian duration environment. They suggested that the abundance distribution of agglutinated benthic foraminifera also faithfully reflects the prevailing paleoenvironment as its well-studied calcareous counterpart, at least for shallow waters (Jain and Farouk, 2017). The present study, however, is related to understanding the inter–relationships between diversity, palaeooxygenation, palaeoproductivity, and palaeodepth. Hence, the only commonality with previous studies is the use of diversity index, Fisher’s α. But, then, in previous studies, Fisher’s α was used as a proxy for accessing the community structure (in conjunction other diversity indices, Shannon H, Dominance, Equitability and Evenness), here, only Fisher’s α is used and as an indirect proxy for accessing organic–flux to the sea floor and paleoxygenation.

The Maastrichtian–Thanetian strata exposed at the Dakhla Oasis is investigated to infer the inter–relationships between diversity, palaeooxygenation, palaeoproductivity, and palaeodepth. The proxies for diversity (Fisher’s α) (see Fig. 4), palaeooxygenation (ventilation) of the sea floor – BFOI (Benthic Foraminifera Oxygen Index) and % Oxiphilic taxa (see Fig. 4); for organic–flux to the sea floor (palaeoproductivity) include: percentage abundances of High organic–flux species (% HOFS; Fig. 4) and infaunal taxa; and benthic foraminiferal morphogroups (Figs. 5–6; Table 1) for reflecting the state of the benthic ecosystem. These approaches are then inferred in combination with the presence of characteristic benthic foraminiferal species and genera and paleodepth (Fig. 7).

[INSERT HERE – FIGURE 4]

One gram of sediment weight was used to pick benthic foraminifers that were soaked in the Na₂CO₃ solution before sieving them over 630, 125 and 63 μm mesh size, respectively. The 63–125 μm fraction size was used and identified under a binocular zoom stereomicroscope. A total of 315 samples (16,271 specimens) were analyzed. Of them, 195 were productive from the 315 m thick Maastrichtian–Thanetian succession exposed at the main escarpment of Gharb El–Mawohb (26° 01' 02" N, 28° 13' 18"E; Western Desert, Egypt) (see Farouk and Jain, 2016; Jain and Farouk, 2017).

However, the present study does have a one undeniable flaw that the specimen size (16,271 specimens from 315 samples, 195 being productive) is small. But, considering that there is still a large representation of diverse taxa (150 species), even in only 2 gram of sediment analyzed for this study, and the fact that a large number of samples were analyzed (315) (see Appendix–Tables 1–2), we believe that simple analysis and distribution patterns will reveal trends that will not be flawed. Owning to small specimen size, no rigorous analysis can be conducted such as Cluster Analysis, Factor Analysis and/or Principal Component Analysis, etc., as they require a minimum of 300 specimens per sample and as is the norm in most micropaleontological studies. Hence, here, a very basic correlation analysis (see Appendix–Tables 3–6) is conducted and vertical distribution trends are considered. The emphasis of the study, however, remains on assemblage analysis, corroborated by results of correlation analysis. This is also a reason why several proxies are considered for paleoenvironmental interpretation in addition to filed observations, P%, etc. Based on this, a tentative model is proposed for their inferred distribution (Fig. 8). The benthic foraminiferal changes at the Cretaceous/Paleogene (K/Pg) boundary are also analyzed (see Figs. 9–11, Tables 2-3; Appendix–Tables 7–8). Important benthic foraminiferal species are illustrated in Fig. 12 using scanning electron microscopy of the Geological Survey of Egypt.

[INSERT HERE – FIGURES 6-8, TABLE 1]

5.2. The Proxies

5.2.1. Diversity proxy

Fisher's α is used as a proxy for representing diversity (Fig. 4) as the latter and Shannon H are statistically significant (0.949, 0.000; correlation significant at the 0.01 level; 2–tailed). Fisher’s α, a within–habitat diversity index and a preferable proxy for species diversity, considers both evenness and richness. However, other species abundance models consider only evenness (Buzas and Gibson, 1969).

5.2.2. Oxygenation proxies

Two proxies are used to estimate the availability of oxygen within the sediment column (or to assess bottom waters as well as pore water oxygenation). These are Benthic Foraminiferal Oxygen Index (BFOI), and the percentage of Oxyphilic taxa (Fig. 4). It must be mentioned, in most continental slope and margin environments (as the present one), the depth of the oxic sediment layer rarely exceeds 5 cm and is mostly confined to the top cm of the sediment column (Corliss, 1985; Jorissen et al., 1998; Fontanier et al., 2002).

5.2.2.1. Benthic Foraminiferal Oxygen Index (BFOI)

Kaiho (1991), based on studies by Phleger and Soutar (1973), Bernhard (1986), Koutsoukos et al., (1990) and Perez–Cruz and Machain–Castillo (1990), developed an empirical ratio of oxic and dysoxic benthic foraminiferal morphotypes called the Benthic Foraminiferal Oxygen Index (BFOI). Based on benthic foraminiferal test morphology data from DSDP cores from the Pacific, South Atlantic and Indian oceans, Kaiho (1991) categorized them into three morphogroups, Oxic (O), Suboxic (S) and Dysoxic (D) (see Appendix–Table 1) and defined the index as [O/(O+D) x 100], where O is the number of oxic species and D the number of dysoxic species. When O = 0 and D+S >0 (S is the number of suboxic indicators), then the BFOI value is given by [(S/(S+D)–1] x 50 (Fig. 2). Later (Kaiho, 1994) calibrated modern values of the BFOI to levels of dissolved oxygen in bottom waters in the modern ocean (for details also Kaminski et al., 2002).

5.2.2.2. % Oxyphilic taxa

Jannink et al., (2001) proposed a transfer function (Oxygen content µMol/lt = 7.9602 + 5.95 x % oxyphilic taxa) to estimate the oxygen content within the sediment column (Fig. 4). Those taxa that occur in the topmost cm of the sediment column are considered oxiphylic, and their cumulative percentage is considered a proxy for bottom water oxygenation. The rationale being that, with increasing bottom water oxygenation, the availability of oxygen in the sediment also increases, resulting in an increased volume of the niche potentially occupied by oxiphylic taxa. In the present study, the epifaunal taxa (see Appendix–Table 1) are considered oxyphylic. The transitory epifaunal to shallow infaunal taxa are not included in the calculations as also species of Lenticulina and Osangularia. Lenticulina, an opportunistic epifaunal species, is an r–type strategist that thrives in slightly better oxygenation conditions with sufficient food availability, and displays a varied epifaunal to deep infaunal microhabitat preference (Tyszka, 1994; Jorissen et al., 1992; Reolid et al., 2008, 2012; Jurassic–Cretaceous). Whereas, representatives of the genus Osangularia (here: O. expanse and O. plummarae) have been noted to behaved opportunistically (Alegret et al., 2009). This is corroborated in the present study as they occur in Assemblage 8 (sample 152) and then suddenly appear just after the K/Pg event in Assemblage 11 (samples 203–211) and then disappear in the succeeding Assemblage 12 (sample 232) (Fig. 4).

Although, both BFOI and % Oxyphilic index employ % epifaunal taxa (= the Oxic (O) taxa used in BFOI; see Appendix–Table 1), however, BFOI also incorporates the presence of Suboxic (S) and Dysoxic (D) taxa not used in the % Oxyphilic index. Hence, BFOI considers a much broader community approach.

5.2.3. Palaeoproductivity proxies

Two palaeoproductivity proxies are used in this study – the percentages of benthic foraminiferal high organic–flux species (%HOFS) and infaunal taxa (Fig. 4).

5.2.1.1. High organic–flux species (% HOFS)

The following species are considered as high–organic–flux species in this study – Anomalinoides aegyptiacus, Bolivina cretosa, Bulimina prolixa, Nonionella africana, N. insect, Praebulimina kikapoensis, P. russi, Pyramidulina affinis, P. distans, P. semispinosa, P. vertebralis, P. zippei and Reussella aegyptiaca (see also Sen Gupta and Machain–Castillo, 1993; Sen Gupta, 1999; Fontanier et al., 2002; Gebhardt et al., 2004; Friedrich and Erbacher, 2006; Jorissen et al., 2007; Friedrich et al., 2009; Alegret and Thomas, 2013; Sprong et al., 2013) (see Fig. 4).

5.2.1.2. Percent infaunal taxa

The species are grouped under epifaunal and infaunal (shallow and deep infaunal with an undifferentiated group as infaunal) with a transitory group of epifaunal to shallow infaunal taxa (see Appendix–Table 1) (Fig. 4). The latter are not included in the infaunal group calculations. Data from various studies (Sliter, 1968; Sliter and Baker, 1972; Corliss, 1985; Jones and Charnock, 1985; Corliss and Chen, 1988; Bernhard, 1986; Langer, 1993; Rathburn and Corliss, 1994; Severin and Erskian, 1981; Jorissen, 1988; Linke, 1992; Sjoerdsma and Van der Zwaan, 1992; Jorissen et al., 1992; Linke and Lutze, 1993; Jorissen, 1988; Corliss and Emerson, 1990; Sjoerdsma and Van der Zwaan, 1992; Kaminski and Gradstein, 2005) have been used to construct Appendix–Table 2.

5.2.4. Morphogroups and subgroups

Regardless of taxonomy, the groupings of similar shapes or growth patterns of benthic foraminiferal tests reflect a particular type of environment, and hence, are good proxies for the prevailing palaeoenvironment, particularly for well–oxygenated temperate environments (Chamney, 1976; Jones and Charnock, 1985; Nagy, 1992; Kaminski et al., 1995; Nagy et al., 1995; Jones, 1999; Preece et al., 1999; van der Akker et al., 2000; Jones et al., 2005; Kender et al., 2008a, b; Cetean et al., 2011, Murray et al., 2011). In the present study (Figs. 6–7; Table 1), the benthic foraminiferal morphogroup assignment is after Koutsoukos and Hart (1990) (Table 1) as more recent schemes provide somewhat less differentiation (Nagy, 1992; Tyszka, 1994; Nagy et al., 1995; van der Akker et al., 2000; Reolid et al., 2008; Nagy et al., 2009; Cetean et al., 2011; Chan et al., 2017). Most of these aforementioned studies are either from the Jurassics (Nagy, 1992; Tyszka, 1994; Nagy et al., 1995; Nagy et al., 2009) or from a different time period (Cetean et al., 2011, Santonian–Campanian; Chan et al., 2017, Tertiary) and thus, have fewer common species to correctly interpret morphotypes. Those that are from a similar period (van der Akker et al., 2000, Campanian–Maastrichtian) are largely from bathyal settings, contrary to the neritic one in the present study and hence, have fewer common species for comparison. The closest comparative account is either that of Tyszka (1994) or of Koutsoukos and Hart (1990). The latter have the maximum number of common species with detailed explanation of their habitat preferences. Thus, based on this latter dataset, the species from the present study are interpreted for their microhabitat assignment. The differentiation of morphological categories (Table 1) is based on three criteria: (a) test morphology, comprising general outline, number of chambers, chamber arrangement and architecture; (b) life habitat, characterized as epifaunal, shallow infaunal and deep infaunal (few are transitional – epifaunal to shallow infaunal); and (c) their supposed feeding strategies, characterized as suspension feeders, deposit feeders, herbivores or bacterial scavengers.

5.2.5. Wall structure (proxy for Palaeodepth)

To infer bathymetry, the agglutinated foraminiferal dataset is grouped based on their preference for palaeodepth i.e. into simple–walled arenaceous agglutinated foraminifera assemblage (representing littoral environment with fresh water supply), complex–walled arenaceous agglutinated foraminifera assemblage (representing deeper littoral environment with normal marine water), and calcareous agglutinated foraminifera assemblage (representing shelf environment) (see also Berggren, 1974; Luger, 1985, 1988; Cherif and Hewaidy, 1986; Orabi, 1995, 2000) (Fig. 7). This is further corroborated with bathymetry inferred from %Planktic foraminifera (%P), total calcareous benthic foraminifera and characteristic species (Fig. 7).

All the above mentioned proxies are subjected to basic statistical analysis (Pearson correlation) (Appendices Tables 3-6) and evaluated based on the framework of the 19 benthic foraminiferal assemblages (species abundance pattern) as established by Farouk and Jain (2016, 2017) and Jain and Farouk (2017) (see Fig. 7).

6.1. Species diversity

The correlation between Fisher’s α and Shannon H is positive and statistically significant (0.949, 0.000, significant at the 0.01 level, 2–tailed); hence, hereafter, Fisher’s α is used as a proxy for species diversity (Fig. 4). Fisher’s α displays high values at the bottom of the studied section (planktic foraminiferal zones CF8b–CF7; samples 1–17), low and fluctuating values until the K/Pg boundary (samples 18–200) and then moderate to high values for the post K/Pg interval (samples 201–315) (Fig. 4). Diversity is low just prior to the K/Pg boundary but gradually increases for the post K/Pg planktic foraminiferal zone P1c (see Fig. 4). The beginning of P2 planktic foraminiferal zone registers high values as also the interval between P2–P3a zones, whereas the post–P3a to P4 interval has consistently low values, coincident with low %P.

6.2. Palaeoproductivity proxies

6.2.1. High organic–flux species (% HOFS)

On an average, the high organic–flux species (% HOFS) do not constitute a major fraction of the assemblage throughout the studied section (largely ranging from 0 to 12% for an assemblage) except in Assemblage 19 where they make up 27% (Fig. 4). Individually, there are four data points that register appreciable higher values: sample nos. 97 (35.3%), 112 (42.9%), 240 (44.4%) and 306 (41.7%) belonging to Assemblages 5, 6, 13 and 19, respectively (see Fig. 8 for assemblages). At the K/Pg boundary (between Assemblages 10 and 11; see Fig. 7) there is no appreciable change, the proxy remains low (< 5%) (Fig. 4). Higher values are only noted at the lower part of planktic foraminiferal zone P3a (sample nos. 238–254) and in P4 (sample nos. 306–315) and moderate values for Assemblages 5–8 (see Fig. 4).

6.2.2. Percent Infaunal

The infaunal species make up 35% of the total benthic foraminiferal dataset (6,351 specimens), epifaunal make up 52% (8,419 specimens), and the transitory epifaunal to shallow infaunal make up 11% (1,789 specimens) (Fig. 4). There is dominance of infaunal taxa throughout the pre–K/Pg boundary interval and particularly during the middle of the lower Maastrichtian (between samples 58 to 73) (Fig. 4). A dominance of epifaunal forms is noted at the bottom of the section in planktic foraminiferal zones CF8b–CF7 (sample nos. 1–17), then, just after the K/Pg boundary (between samples 201 to 226) and somewhat in planktic foraminiferal zones P3a–P4 (sample nos. 238–315) (Fig. 4). As regards to sequence stratigraphy (as established by Farouk and Jain, 2016, 2017 and Jain and Farouk, 2017), the Transgressive System Tracts (TST) display higher abundances of the epifaunal taxa (and of %P) and the High System Tracts (HST) of infaunal forms (Fig. 4).

6.3. Oxygenation proxies

6.3.1. % Oxyphilic taxa

As with Diversity, and BFOI, the % Oxyphilic taxa also follow the same pattern; high values at the bottom of the section (planktic foraminiferal zones CF8b–CF7; samples 1–17), fluctuating values until the K/Pg boundary (samples 18–200) and then consistently high values for the post K/Pg interval (samples 201–315) (Fig. 4).

6.4. Morphogroups and subgroups

Following Koutsoukos and Hart (1990), for the Agglutinated (AG) morphotypes, three morphogroups (AG–A, AG–B and AG–C) and two submorphogroups of AG–B (AG–B.1 and AG–B.2) are identified (see Figs. 5–6; Table 1; Appendix–Table 1). For the Calcareous–Hyaline (CH) morphotypes, two morphogroups (CH–A and CH–B) with six submorphogroups of CH–A (CH–A.1, CH–A.2, CH–A.3, CH–A.4, CH–A.5 and CH–A.6) and five submorphogroups of CH–B (CH–B.1, CH–B.2, CH–B.3, CH–B.4 and CH–B.5) are identified (see Figs. 5–6; Table 1; Appendix–Table 1). Two morohogroups, CH–B.1 and CP–A8 constitutes only one species (and in negligible numbers), Globulina lacrima and Quinquloculina gussensis, respectively. The former occurs in sample 154 only (Assemblage 8) whereas the latter occurs in two samples (246 and 299; Assemblages 13 and 18, respectively) and hence, are not shown (Fig. 5).

Of the 16 identified submorphogroups (14 shown in Fig. 5) only five (CH–A.4, CH–B.4, CH–B.5, AG–A and AG–B.2; 34%, 12%, 12%, 9% and 8%, respectively) dominate (Fig. 6–7). For the pre– K/Pg interval, for the calcareous forms, CH–A4 and for the agglutinated, AG–A and AG–B.2 dominate (Fig. 6) and for the post–K/Pg interval, CH–A4 and AG–B.2 dominate, respectively (Fig. 6). The deeper portions of the section are largely characterized by the dominance of CH–A4 (coincident with high %P values; see Fig. 6), whereas the shallower ones are either dominated by the agglutinated morphotypes AG–A and AG–B.2 (Fig. 6).

6.5. Wall structure

Of the palaeodepth indicators (littoral, deeper littoral and shelf), the littoral dominates the section (Fig. 7); the deeper littoral proxy dominates at the base of the section (CF8b–CF7 planktic foraminiferal zone) and shelf forms dominate within the CF3 and at the end of P4 planktic foraminiferal zones (Fig. 7). The abundance of planktic foraminifera (%P; Fig. 3) correlates well with higher values of the deeper littoral and shelf indicators (Fig. 8; see also Appendix–Table 4).

6.6. Statistical analysis

All aforementioned proxies (Fischer's α, BFOI, % Oxiphylic, % HOFS and % Infaunal) are significantly and positively correlated (see Appendix–Table 3). The brief interval of high palaeoproductivity and low diversity and oxygenation, during the mid–lower Maastrichtian (between samples 58 to 73), was also subjected to statistical analysis (Pearson Correlation) and has returned with negative and statistically significant values for the palaeoproductivity proxies, especially the % infaunal taxa (Appendix–Table 3b). A more high resolution data set is likely to yield the same for the other palaeoproductivity proxy, % HOFS (Appendix–Table 3b). Statistical analysis was again performed after deleting the samples for this brief interval (16 samples). The results have yielded the same positive and significant relationship between all proxies (Appendix–Table 3c). The relationship between the % P and test wall type (palaeodepth indicators; Fig. 7) was also analysed; the shelf indicators correlate positively and statistically significantly with % P (Appendix–Table 4). Statistical analysis was also performed between the dominant morphogroups and all proxies and have yielded positive and statistically significant relationships (Appendix–Table 5), corroborating the relationships noted for oligotrophic settings (Jain et al., 2007).

6.7. Changes at the K/Pg boundary

6.7.1. Comparative accounts

Most benthic foraminiferal records that address changes at the K/Pg boundary or for the intervening interval (Late Maastrichtian–Early Paleogene) are from the deep sea (Late Maastrichtian: Widmark and Speijer, 1997; Widmark, 2000; Early Maastrichtian: Friedrich et al., 2005; Friedrich and Hemleben, 2007; K/Pg boundary: Keller, 1988; Speijer and Van der Zwaan, 1996; Culver, 2003; Palaeocene (mostly about the transition between the Palaeocene/Eocene boundary; PETM): Miller et al., 1987, Thomas and Shackleton, 1996; Alegret and Ortiz, 2006, Giusberti et al., 2009). There are very few records (see Culver, 2003 for a review) that address changes at shallow water settings (i.e. neritic, < 200 m water depth) (Sikora, 1984; Huber, 1988; Keller, 1992; Schmitz et al., 1992; Olsson et al., 1996; Keller et al., 1998). The classic ones being those by Plummer (1927) on the Midway (Palaeocene) and Cretaceous foraminifera from Texas (North America), and by Olsson (1960) on the latest Cretaceous and earliest Paleogene foraminifera from New Jersey (North America).

For shallow neritic waters, in Texas (North America), 16% of benthic foraminiferal species do not cross the K/Pg boundary (Plummer, 1927); at the Brazos River (Texas), ~ 50% disappear / emigrate (but temporarily) (Keller, 1992); in New Jersey (North America), 32% do not cross the boundary (Olsson, 1960); at Seymour Island, Antarctica, 64% do not cross the boundary (Huber, 1988); and at Seldja (Tunisia), 13% of “common” species are restricted to the upper Maastrichtian (Keller et al., 1998). However, Culver (2003) noted that if the percentage data are taken as published and averaged, then the numbers are: at shallow depths – 40% disappear; intermediate – 35% (using maximum figures), or 29% (using minimum figures) disappear; and for deep waters – 32% (maximum) or 22% (minimum). Culver (2003) further noted that although there is a weak trend of decreasing values with increasing depth, the pattern of one third disappearance / extinction / turnover, is regardless of bathymetry, and does not strongly support the notion that shallow–water benthic foraminifera were more severely affected by environmental events across the K/Pg boundary than the intermediate– or deepwater faunas.

Globally, at shallow water neritic depths there are only four data points available for comparison. At Brazos River (Texas, North America), the faunas are almost entirely infaunal on both sides of the boundary (Keller, 1992). At Millers Ferry (Alabama, North America), the fauna changes from infaunal in the Maastrichtian to epifaunal in the Danian (Olsson et al., 1996). Closer home, at Aïn Settara (Tunisia), the Danian sediment similarly contain low–diversity assemblages dominated by epifaunal morphogroups, indicative of extreme oligotrophic conditions (Peyrt et al., 2002). At El Kef, just 50 km to the north, similar low diversity and low dominance fauna have been attributed to the prevailing low–oxygen conditions, an interpretation based on the presence of laminated sediments resulting from the lack of burrowing macrofauna (Keller, 1988; Speijer and van der Zwaan, 1996). However, Peyrt et al. (2002) pointed out that there is no geochemical indication of low–oxygen conditions (see also Tribovillard et al., 2000) and that the lack of burrowing could simply be related to the K/Pg mass extinction of burrowing invertebrates. Peyrt et al. (2002) argued that the low–diversity assemblages immediately above the K/Pg boundary may have been caused by environmental stress resulting from changes in the nature of the phytoplankton flux to the seafloor (see also Culver, 2003). The calcareous nannofossils, a major Late Cretaceous primary producer, suffered a major extinction (Romein and Smit, 1981) and so the early Danian benthic foraminifera were left with a changed food supply composed mainly of dinofagellates, a group that did not experience mass extinction (Brinkhuis et al., 1998). Thus, this general pattern of infaunal disappearance and epifaunal dominance in the early Danian is explained by a sudden decline of primary productivity at the K/Pg boundary, and, a cessation of the organic carbon flux to the seafloor (Thomas, 1990; Widmark and Malmgren, 1992; Alegret et al., 2001; Peyrt et al., 2002). This would have led to the eventual decline in abundance of the infaunal taxa that were typically adapted to low–oxygen conditions and/ or high food supply. Therefore, food, and related oxygen availability, are seen as prime ecological factors in controlling changes in benthic foraminiferal assemblages across the K/Pg boundary (see also Culver, 2003). In context of the present study, this interplay of food and oxygen is elaborated further under Discussion.

6.7.2. Present data

Seven scenarios (Table 2) are explored to access neritic benthic foraminiferal changes at the K/Pg boundary ranging from an analysis of an assemblage below and above the boundary (scenario “a”, Assemblages 10 and 11, 26 samples; the boundary is drawn between samples 200 and 201; see Farouk and Jain, 2016) to a more extended interval (scenarios “f” and “g”; scenario “f” – incorporating data from Assemblages 9 to 18, 294 samples; Upper Maastrichtian to the Thanetian interval and scenario “g” – substage data, Upper Maastrichtian–Lower Paleocene). A sample–by–sample approach analysis is not undertaken as at the top of Assemblage 10 and following the K/Pg boundary, there is a regional hiatus (of missing CF2 to P1b planktic foraminiferal zones; see Farouk, 2016; Farouk and Jain, 2016). Hence, we have used an assemblage approach as it gives a broader and better picture of the prevailing benthic ecosystem. The logic for using an extended time interval (scenario f; Table 2) is to make sure that the temporary disappearance / reappearance of species do not affect the dataset and the interpretation, thereof (see Culver, 2003). Hence, for all analysis (scenarios a–e; Table 2), the term “disappearance” is used and “extinction” is used only for scenarios “f” and “g” (Table 2; see also Figs. 9–11), as the latter two analyses incorporates an extended time period (“extinction” is used with caution; only three Lazarus taxa are noted in this study, namely Cibicides beaumontianus, Praebulimina kikapoensis and Praebulimina russi). Scenario “f” (Fig. 9 with abundances > 5%) spans from Assemblages 9 to 18 (see Fig. 7) and Scenario “g” (Table 2; see also Figs. 10–11 with abundances > 5%) deals with the comparison between substages, Upper Maastrichtian and Lower Palaeocene. Table 3 summarizes the changes of proxies (before and after the K/Pg boundary) both at the level of individual samples and assemblage (10 and 11) (see also Fig. 7).

[INSERT HERE – FIGURES 9–11, Tables 2–3]

This contribution bears out six fundamental points:

Species diversity, Palaeoproductivity and palaeooxygenation are correlated positively and significantly, a characteristic feature of an oligotrophic environment. But a very brief interval (the mid–lower Maastrichtian; samples 58–73) of increased palaeoproductivity with reduced diversity and oxygenation (reduced ventilation) yields a negative and significant correlation characteristic of a mesotrophic–eutrophic setting.

Test wall–based palaeodepth indicators suggest littoral depths throughout the studied interval, punctuated briefly by deeper littoral depths at the base of the section (planktic foraminifera zones CF8b–CF7), and shelf environment for CF3 and at the end of P4 planktic foraminiferal zones. The abundance of planktic foraminifera (%P) correlates with higher values for the deeper littoral and shelf indicators, being positive and significant with the shelf indicator.

Seven (a–g) scenarios are explored to access changes at the K/Pg boundary. The “long term” data for the substage (Upper Maastrichtian–Lower Palaeocene) suggests that 38% of the agglutinated and 40% of the calcareous species became extinct after the K/Pg boundary with an overall 40% “extinction”. The data for the short term (i.e. samples before and after the K/Pg; termed “disappearances”) are 10%, 36% and 25%, respectively.

As regards benthic foraminiferal changes across the K/Pg boundary, in this study as with other global ones, the dominance of epifaunal taxa in the early Danian is marked.

In an oligotrophic setting like this, the effects noted across the K/Pg are more dramatic with respect to a shift in species composition (assemblage), a shift from a pre–K/Pg agglutinated–dominated assemblage (Haplophragmoides–Ammobaculites) to a post– K/Pg calcareous one (Cibicodoides–Cibicides–Anomalinoides), rather than in the community structure, itself (i.e. species diversity – Fisher’s α).

This contribution reaffirms that palaeoproductivity, palaeooxygenation, and species diversity are closely interlinked (Fig. 4; Appendix–Table 5) (see also Mackensen et al., 1990, 1995; Thomas and Gooday, 1996; Schmiedl et al., 1997; van der Zwaan et al., 1999; Levin et al., 2001; Gooday, 2003; Jorissen et al., 2007; Jain et al., 2007; Alegret and Thomas, 2009). In oligotrophic settings, a positive relationship is noted between benthic foraminiferal diversity and palaeoproductivity (Arctic: Wollenburg and Mackensen, 1998; Wollenburg and Kuhnt, 2000; Eastern Central Atlantic: Heinz et al., 2004; South China Sea: Hess and Kuhnt, 2005; Caribbean: Jain et al., 2007), whereas a negative one is observed in mesotrophic–eutrophic environments such as in the Arabian Sea (Den Dulk et al., 1988; Gooday et al., 1998). In oligotrophic settings, such as the ice–covered Arctic (the least productive area of the world), Wollenburg and Mackensen (1998) noted that the benthic foraminiferal associations are mainly controlled by the availability and competition for food. In seasonally ice–free periods, high aundance and high benthic foraminiferal diversities reflect increased primary production rates; both increase with increasing food supply (Wollenburg and Mackensen, 1998). This positive relationship is also noted for the low latitude sites in the Neogene Caribbean (Jain et al., 2007; Jain and Collins, 2007; Jain, 2011) as well as in the present study, spanning the Upper Cretaceous–Lower Paleogene interval (Fig. 8).

However, a very brief interval within the mid–lower Maastrichtian (samples 58–73 only; Assemblage 3) reflects a period of increased palaeoproductivity with reduced species diversity and ventilation (reduced oxygenation), consistent with mesotrophic–eutrophic settings (Fig. 4). This interval coincides with shallow littoral depths (HST1; Figs. 4 and 8), high % of infaunal taxa (Fig. 4), and the dominance of the agglutinated morphogroups AG–A (infaunal) and AG–B.2 (infaunal to shallow infaunal) (Figs. 5–6). This brief interval (Assemblage 3; see Fig. 8) is also marked by the abundance of Ammobaculites khargaensis, a species that disappeared after the K/Pg boundary when the environment became more oxygenated (Figs. 4 and 9a) suggesting a preference of this species for low oxygen content in shallow to deep infaunal microhabitats. However, for this brief interval, moderate diversity values and moderate dominance (Fig. 4) suggests that oxygen was not a limiting factor, in spite of increased palaeoproductivity (food availability), possibly made available due to increased runoff in a brackish/lagoonal setting (as evidenced by reduced values of the diversity index Fisher’s α; <5) (see Fig. 4).

The samples 58–73 (Assemblage 3) are barren of planktic foraminifers but most likely encompass the middle part of lower Maastrichtian, the planktic foraminifera Zone CF6 (see also Tantawy et al., 2001; Farouk and Jain, 2016) (se Fig. 3). For this interval, cooler climates and lower sea level (the latter is also noted in the present study; see Fig. 4) are well–documented (Li et al., 1999, 2000; Haq, 2014). It is likely that in such a shallow setting, possibly there was an upwelling of cooler waters (and aided by increased runoff) resulted in increased food supply, but not beyond a threshold so as to result in oxygen being a limiting factor.

The mid Maastrichtian is also an interval that is globally marked by a positive δ¹³C values (a plateau–like high) called the Mid Maastrichtian Event (MME) (Voigt et al., 2012) and has recently been identified (in part) at Gebel Matulla (west–central Sinai, Egypt; Farouk, 2014) encompassing the top of planktic foraminiferal zone CF5 and broadly corresponds to the top of HST1 (= present work Assemblages 5 and 6; samples 86–127; see Fig. 4). Since the duration is barren of planktic foraminifera (Fig. 3), the placement of MME is tentative but follows the same pattern – HST, marked by low species diversity, neritic depth, higher percentages of infaunal taxa and % HOFS (Fig. 4) as noted in the Gebel Matulla section in Sinai, Egypt (Farouk, 2014: CF7–CF5 = Coryphostoma incrassata, Gavelinella limbata, Nonionella cretacea, N. robusta, and Osangularia expansa; = middle to outer neritic). As in the present study, the influence of sea level coupled with tectonic uplift (to shallower depths) is the main causal mechanism. Assemblage 5 and 6 in the present work (see Fig. 7) are also marked by, but, with somewhat more shallower–water taxa (inner to ?middle neritic) including the calcareous Discorbis pseudoscopus and Valvalbamina depressa and agglutinated Ammobaculites khargaensis and Trochammina rainwateri (Fig. 7).

The distribution of morphogroups, in the present study, also reflects the influence of the availability of food (palaeoproductivity), oxygenation and palaeodepth (Fig. 6; Appendix–Table 5). The TST’s are marked by the dominance of the epifaunal calcareous morphogroup CH–A4 and the HST’s by the agglutinated morphogroups of AG–A and AG–B.2, infaunal and epifaunal to shallow infaunal forms, respectively (Fig. 6). Palaeoproductivity never reached the threshold, where one would expect negative relationship, characteristic of meso– to eutrophic environment (Appendix–Table 5). The influence of palaeodepth (Fig. 7) seems remarkable as the calcareous morphogroups CH–A4, CH–B4 and CH–A5 do not correlate with the shallower depth proxies (littoral and deeper littoral) but positively and significantly with the deeper shelf indicator (Appendix–Table 5).

This study also demonstrates (both qualitatively and quantitatively; Figs. 4, 5–7, Table 1; Appendix–Tables 3–6, respectively) that in a shallow water setting, the distribution of benthic foraminifera are not just governed by the availability of organic–flux to the sea floor (palaeoproductivity), and oxygen content (palaeooxygenation), but also palaeodepth. But, for now, the individual influence of these three to the distribution of benthic foraminifera are hard to discern but it appears that in a well–oxygenated setting, the availability of food was a function of depth and, its downward movement was governed by the availability of oxygen. Diversity clearly shows depth–dependency, with significant positive correlations increasing in strength with increasing depth (least for littoral depths; see Appendix–Table 6).

The relationship of palaeoproductivity, palaeooxygenation and species diversity for the present study duration can be explained using a combination of the TROX model (the trophic condition and oxygen concentration of Jorissen et al., 1995; also Jorissen, 1999) and the parabolic curve of Levin et al., (2001) (see also Gooday, 2003; Jain et al., 2007) (Fig. 8). Species diversity is low and thus incapable of sustaining large number of species in highly oligotrophic areas where food supply (flux of organic carbon to the seafloor = productivity) is very low but is maximized in well–oxygenated settings (even at bathyal and abyssal depths) (also Gooday et al., 1998) (the left hand–side of Fig. 8). In highly mesotrophic–eutrophic areas such as the Oxygen Minimum Zone (OMZ), species diversity again records lower values, where stress caused by the abundance of species leads to reduced diversity (the right hand–side of Fig. 8). The abundance of food and reduced predation facilitates increases diversities. However, when oxygen becomes limiting, diversities fall (see Fig. 8). Samples 1–57 and 74–315 represents the left hand–side of Fig. 8, whereas, samples 58–73 represent the top right hand–side of Fig. 8.

As regards benthic foraminiferal changes across the K/Pg boundary, it is apparent from the present data that depending upon the calculated interval, the “disappearance” and “extinctions” vary considerably (see Figs. 9–11; Table 2–3). But, by only considering the short term interval data (i.e. across the K/Pg boundary; samples 200/201; scenario “a”; Table 3), the picture may not be complete due to the hiatus that is ubiquitous across Egypt, from the planktic foraminiferal zones CF2 to P1c (see Farouk, 2016; Jain and Farouk, 2017). Hence, scenarios “b–e” (the Assemblage approach) gives a somewhat better picture but on a coarser timescale (see Table 2). However, the latter is the best option for understanding changes at the K/Pg boundary in Egypt, for now. Interestingly, the results of this “long–term” approach (see Figs. 9–11; Table 2–3) is also consistent with the “pattern of approximately one third disappearance / extinction / turnover” noted in other exposures, globally (Culver, 2003) (see also Table 2).

The other point of commonality in the present study with other global ones (Culver, 2003) is the general pattern of the dominance of epifaunal taxa in the early Danian (see Fig. 4). This shift is also corroborated by the morphogroup analysis where a sudden increase in the epifaunal morphogroup CH–A4 is noted (see Figs. 4 and 6). Both these changes (dominance of epifaunal taxa and epifaunal morphogroup) also coincide with improved ventilation (higher BFOI and % Oxiphylic values; see Fig. 4) suggesting that in shallow largely oligotrophic waters, as this one (< 100m), the breakdown of productivity (surface and bottom) and the subsequent decrease in food supply due to the bolide impact, may not have had a dramatic effect on the larger benthic environment (represented by the cumulative proxies such as species diversity, palaeoproductivity and palaeooxygenation) that were already well adapted to a lowered food supply (oligotrophy). Hence, in such oligotrophic settings, the effects noted are more dramatic with respect to a shift in species composition (assemblage) (see Figs. 9–11) and a shift from a pre–K/Pg agglutinated–dominated assemblage (Haplophragmoides–Ammobaculites) to a post–K/Pg calcareous one (Cibicodoides–Cibicides–Anomalinoides), rather than in the community structure (species diversity), itself (see also Fig. 4). Even, from the prospective of the morphogroup analysis, the shift occurs from a largely agglutinated AG–A morphogroup (infaunal, deposit feeders) to a dominantly CH.A4 morphogroup (epifaunal, deposit feeders and passive herbivores; browsers), across the K/Pg boundary (see Figs. 5–6). The other ubiquitous agglutinated morphogroup, AG–B.2 (epifaunal/shallow infaunal, deposit feeders), successfully transgresses, albeit a bit diminished, across the boundary event (see Figs. 5–6); both emphasizing the preferential survivorship of epifaunal forms or that the neritic species may have been more adapted to environmental variability, as compared to bathyal forms (Alegret and Thomas, 2013).

Globally, this shift of the dominance of epifaunal taxa in the early Danian is also reflected (directly or indirectly) by other proxies, such as (a) the collapse in carbon isotope values, (b) the interruption of primary productivity or export productivity and (c) the geographical heterogeneity of the latter. Globally, the sedimentary records of the K/Pg boundary attests to a collapse of carbon isotope gradients between surface and deep sea carbonates (Alegret et al., 2003; d'Hondt, 2005; Alegret et al., 2012; Alegret and Thomas, 2013) and has been interpreted as the result of a long–term interruption of primary productivity or export productivity (the Strangelove Ocean and Living Ocean models; Hsü and McKenzie, 1985; d'Hondt et al., 1998; d'Hondt, 2005; Coxall et al., 2006). But the lack of correspondingly significant extinction in benthic foraminifera (Alegret et al., 2012), whose species abundance and diversity is a function of the export of organic matter from surface ocean productivity down to the sea floor, the bentho–pelagic coupling (Gooday, 2003; Jorissen et al., 2007), suggests otherwise. Three probable explanations have been put forward to explain this contradiction: (a) the oceanic primary productivity probably recovered very quickly after the K/Pg event, (b) the collapse in carbon isotope values (highly negative) is but a reflection of the effect of the extinction of the carriers of the isotope signal, the calcareous nannoplankton and planktic foraminifera, that were eventually replaced by taxa with a much lighter carbon isotope signature than their Maastrichtian predecessors (Alegret et al., 2012; Birch et al., 2012), and (c) there exists geographical heterogeneity with increased export productivity in some areas (Pacific Ocean, New Zealand), and decreased in others such as the Indian Ocean, Tethys, and some Atlantic sections (Hollis et al., 2003; Alegret and Thomas, 2005, 2009; Alegret, 2007; Hull and Norris, 2011; Alegret et al., 2012; Sibert et al., 2014; Esmeray–Senlet et al., 2015; Birch et al., 2016). Recently it has been documented (Birch et al., 2016) that the last scenario (“c”) is a more viable option being operated in three stages: an initial stage (stage 1), from the K/Pg boundary to ~ 300 k.y., is marked by planktic to benthic Δδ¹³C values that are close to zero or negative with very low bulk δ¹³C and carbonate accumulation rates. By stage 2, the planktic–benthic Δδ¹³C begins to return to pre–extinction levels and the bulk δ¹³C and carbonate accumulation rates also increase. The final recovery (stage 3), ~ 2.5 m.y. after the event, marks the return of differences between mixed–layer and thermocline planktic foraminifera. Our data is too coarse to corroborate or evaluate this heterogeneity model but rather points towards a much larger role of sea level. The rising sea level near the end of the Maastrichtian and across the K/Pg boundary (see Li et al., 1999, 2000; Haq, 2014; Farouk and Jain, 2016), would have brought in warm waters to the largely shallow (deeper littoral; see Figs. 4 and 7) oligotrophic setting (Fig. 4), thereby providing an already thriving epifaunal community newer niches to exploit further and diversify. A gradually increasing diversity indices with consistently moderate to high values after the K/Pg boundary (Fig. 4) would have also meant that oxygen was not limiting, which is normally what one would expect from a transgressive event. This marine incursion also possibly coincided with subsidence (regional tectonic) as noted by a sudden increase in %P, from 0 to 63 (see Table 3) as well as by changes in benthic foraminiferal assemblage and paleodepth proxies (see Fig. 7).

[INSERT HERE – FIGURE 12]

This multi–proxy approach enables to better understand the palaeoenvironmental changes and the inter–relationships between palaeooxygenation, palaeoproductivity, species diversity and palaeodepth for the shallow water Maastrichtian–Thanetian rocks exposed at the Dakhla Oasis (Western Desert, Egypt).

Data suggests a positive and statistically significant correlation between species diversity, palaeooxygenation and palaeoproductivity consistent with a well–oxygenated oligotrophic setting. A brief interval (mid–lower Maastrichtian) of increased palaeoproductivity with reduced diversity and oxygenation show negative and significant correlation, consistent with mesotrophic–eutrophic settings. This interval also coincides with very shallow waters during a Highstand System Tract (HST), and is dominated by the dysoxic agglutinated taxa Ammobaculites khargaensis.
Species diversity (Fisher’s α) displays high values at the bottom of the studied section (planktic foraminiferal zones CF8b–CF7), low and fluctuating values until the K/Pg boundary and then moderate to high values for the post K/Pg interval.
On an average, the high organic–flux species (% HOFS) do not constitute a major fraction of the assemblage except in Assemblage 19 where they make up 27%. At the K/Pg boundary (between Assemblages 10 and 11) there is no appreciable change, the proxy remains low (< 5%).
The infaunal species make up 35% of the total benthic foraminiferal dataset. A dominance of epifaunal forms is noted at the bottom of the section in planktic foraminiferal zones CF8b–CF7, then, just after the K/Pg boundary and somewhat for planktic foraminiferal zones P3a–P4. The Transgressive System Tracts (TST) display higher abundances of the epifaunal taxa (and of %P) whereas the High System Tracts (HST) are marked by an increase in infaunal taxa.
The BFOI, the % Oxyphilic taxa follow the diversity pattern (Fisher’s α); high values at the bottom of the section, fluctuating values until the K/Pg boundary and then consistently high values for the post K/Pg interval.
Of the 16 identified submorphogroups only five (CH–A.4, CH–B.4, CH–B.5, AG–A and AG–B.2) dominate. For the pre– K/Pg interval, for the calcareous forms, CH–A4 and for the agglutinated, AG–A and AG–B.2 dominate and for the post–K/Pg interval, CH–A4 and AG–B.2 dominate, respectively. The deeper portions of the section are largely characterized by the dominance of CH–A4 (coincident with high %P values), whereas the shallower ones are either dominated by the agglutinated morphotypes AG–A and AG–B.2.
Of the palaeodepth indicators (littoral, deeper littoral and shelf), the littoral dominates the entire studied section; the deeper littoral proxy dominates at the base of the section (CF8b–CF7 planktic foraminiferal zone) and shelf forms dominate within the CF3 and at the end of P4 planktic foraminiferal zones.
Seven scenarios were explored to access neritic benthic foraminiferal changes at the K/Pg boundary ranging from an analysis of an assemblage below and above the boundary (Assemblages 9 and 10) to a more extended interval incorporating data from Assemblages 9 to 18 (Upper Maastrichtian–Thanetian interval). The “long term” data (Upper Maastrichtian–Lower Palaeocene) suggests 38% agglutinated and 40% calcareous species became extinct after the K/Pg boundary with an overall 40% “extinction”. The data for the short term (i.e. samples before and after K/Pg; “disappearances”) is 10%, 36% and 25%, respectively.
In an oligotrophic setting like this, the effects noted across the K/Pg are more dramatic with respect to a shift in species composition (assemblage), a shift from a pre–K/Pg agglutinated–dominated assemblage (Haplophragmoides–Ammobaculites) to a post– K/Pg calcareous one (Cibicodoides–Cibicides–Anomalinoides), rather than in the community structure, itself (represented by Fisher’s α).
All changes in benthic foraminifera (proxies, diversity, morphogroup and assemblage) is a function of changes in the sea level exacerbated by regional tectonics, whenever they work in tandem such as during the K/Pg boundary interval where sudden deepening provided newer niches to the already thriving (oligotrophic) epifaunal community.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships

that could have appeared to influence the work reported in this paper.

Data Availability Statement

The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.

Author Contributions

Sherif Farouk: Ideas; filed works; formulation and evolution of overarching research goals and aims, preparation and writing the initial draft. Management and coordination responsibility for the research activity planning and execution.

Sreepat Jain: Writing and idea of the initial paper, preparation, creation and presentation the data

Khaled Al-Kahtany, design the idea of the initial paper, preparation, creation, foraminiferal examination

Fayez Ahmad: performing the experiments and data collection

Ahmed Abdeldaim: Discussion, preparation, and creation

Funding

Filed study and laboratory works funding is provided King Saud University.

Acknowledgements

Research Supporting Project number (RSP-2021/139), King Saud University, Riyadh, Saudi Arabia.

Abdel–Kireem, M.R., Samir, A.M. 1995. Biostratigraphic implications of the Maastrichtian–Lower Eocene sequence at the North Gunna section, Farafra Oasis, Western Desert, Egypt. Marine Micropalaeontology 26, 329–340.
Alegret, L. 2007. Recovery of the deep-sea floor after the Cretaceous/Paleogene boundary event: the benthic foraminiferal record in the Basque–Cantabrian basin and in South-eastern Spain. Palaeogeography, Palaeoclimatology, Palaeoecology 255, 181–194.
Alegret, L., Molina, E., Thomas, E. 2001. Benthic foraminifera at the Cretaceous/Tertiary boundary around the Gulf of Mexico. Geology 29, 891–894.
Alegret, L., Molina, E., Thomas, E. 2003. Benthic foraminiferal turnover across the Cretaceous/Paleogene boundary at Agost (southeastern Spain): palaeoenvironmental inferences. Marine Micropalaeontology 48, 251–279.
Alegret, L., Ortiz, S. 2006. Global extinction event in benthic foraminifera across the Paleocene/Eocene boundary at the Dababiya Stratotype section. Micropaleontology 52, 433–447.
Alegret, L., Ortiz, S. 2007. Global extinction event in benthic foraminifera, Paleocene/Eocene boundary, Dababiya Stratotype section. Micropaleontology 52, 433–447.
Alegret, L., Ortiz, S., Molina, E. 2009. Extinction and recovery of benthic foraminifera across the Paleocene–Eocene Thermal Maximum at the Alamedilla section (southern Spain). Palaeogeography, Palaeoclimatology, Palaeoecology 279, 186–200.
Alegret, L., Thomas, E. 2005. Cretaceous/Paleogene boundary bathyal palaeo–environments in the central North Pacific (DSDP Site 465), the Northwestern Atlantic (ODP Site 1049), the Gulf of Mexico and the Tethys: the benthic foraminiferal record. Palaeogeography, Palaeoclimatology, Palaeoecology 224, 53–82.
Alegret, L., Thomas, E. 2009. Food supply to the seafloor in the Pacific Ocean after the Cretaceous/Paleogene boundary event. Marine Micropalaeontology 73, 105–116.
Alegret, L., Thomas, E. 2013. Benthic foraminifera across the Cretaceous/Paleogene boundary in the Southern Ocean (ODP Site 690): Diversity, food and carbonate saturation. Marine Micropalaeontology 105, 40–51.
Alegret, L., Thomas, E., Lohmann, K.C. 2012. End–Cretaceous marine mass extinction not caused by productivity collapse. Proceedings of the National Academy of Sciences 109, 728–732.
Ayyad, S.N., Faris, M., El Nahass, H.A., Saad, Kh. A.A. 2003. Planktonic Foraminiferal and Calcareous Nannofossil Biostratigraphy from the Upper Cretaceous–Lower Eocene successions in Northeast Sinai, Egypt. In: The 3rd International Conference on the Geology of Africa, 1, 649–683.
Beckmann, J. P., El Heiny, I., Kerdany, M. T., Said, R., Viotti, L. 1969. Standard planktonic zones in Egypt. In: Proc. 1st International Conference on Planktic Fossils (Geneva, 1967) 1, 92–103.
Berggren, W.A. 1974. Late Palaeocene–early Eocene benthonic foraminiferal biostratigraphy and palaeoecology of Rockall Bank. Micropalaeontology 20, 426–448.
Bernhard, R.P. 1986. Late Quaternary Benthic Foraminifera of the Colombia Basin and Cayman Trough, Caribbean Sea. M.S. thesis, Louisiana State University, Baton Rouge, USA, 185.
Birch, H. S., Coxall, H. K., Pearson, P. N., Kroon, D., Schmidt, D. N. 2016. Partial collapse of the marine carbon pump after the Cretaceous–Paleogene boundary. Geology doi:10.1130/G37581.1.
Birch, H., Coxall, H., Pearson, P. 2012. Evolutionary ecology of Early Palaeocene planktonic foraminifera: size, depth habitat and symbiosis. Palaeobiology 38, 374–390.
Brinkhuis, H., Bujak, J.P., Smit, J., Versteegh, G.J.M., Visscher, H., 1998. Dinoflagellate–based sea surface temperature reconstructions across the Cretaceous–Tertiary boundary. Palaeogeography, Palaeoclimatology, Palaeoecology 141, 67–83.
Buzas, M.A., Gibson, T.G. 1969. Species diversity: benthonic foraminifera in western North Atlantic. Science 163, 72–75.
Cetean, C.G., Ramona Bălc, R., Kaminski, M.A. Filipescu, S. 2011. Integrated biostratigraphy and palaeoenvironments of an upper Santonian – upper Campanian succession from the southern part of the Eastern Carpathians, Romania. Cretaceous Research 32, 575–590.
Chamney, T.P. 1976. Foraminiferal morphogroup symbol for palaeoenvironmental interpretation of drill cutting samples: Arctic America. Maritime Sediments, Special Publication 1B, 585–624.
Chan, S.A., Kaminski, M.A., Al–Ramadan, K., Babalola, L.O. 2017. Foraminiferal biofacies and depositional environments of the Burdigalian mixed carbonate and siliciclastic Dam Formation, Al–Lidam area, Eastern Province of Saudi Arabia. Palaeogeography, Palaeoclimatology, Palaeoecology 469, 122–137.
Cherif, O. H., Hewaidy, A. A. 1987. The Maastrichtian planktic foraminiferal fauna of the Abu Tartur area, Western Desert, Egypt. Egyptian Journal Geology 31, 217–31.
Coccioni, R., Marsili, A. 2007. The response of benthic foraminifera to the K/Pg boundary biotic crisis at Elles (northwestern Tunisia). Palaeogeography, Palaeoclimatology, Palaeoecology 255, 157–180.
Corliss, B.H. 1985. Microhabitats of benthic foraminifera within the deep–sea sediments. Nature 314, 435–438.
Corliss, B.H., Chen, C. 1988. Morphotype patterns of Norwegian Sea deep sea benthic foraminifera and ecological implications. Geology 16, 716–719
Corliss, B.H., Emerson, S. 1990. Distribution of Rose bengal stained deep–sea benthic foraminifera from the Nova Scotian continental margin and Gulf of Maine. Deep–Sea Research 37, 381–400.
Coxall, H.K., d'Hondt, S., Zachos, J.C. 2006. Pelagic evolution and environmental recovery after the Cretaceous–Paleogene mass extinction. Geology 34, 297–300.
Culver, S.J. 2003. Benthic foraminifera across the Cretaceous–Tertiary (K–T) boundary: a review. Marine Micropalaeontology 47, 177–226.
Den Dulk, M., Reichart, G.J., Memon, G.M., Roelofs, E.M.P., Zachariasse, W.J., van der Zwaan, G.J. 1988. Benthic foraminiferal response to variations in surface water productivity and oxygenation in the northern Arabian Sea. Marine Micropalaeontology 35, 43–66.
Dercourt, J., Ricou, L.E., Vrielynck, B. 1993. Atlas Tethys Palaeoenvironmental maps, Explanatory notes. Gauthier–Villars, Paris, 307 p.
d'Hondt, S. 2005. Consequences of the Cretaceous/Paleogene mass extinction for marine ecosystems. Annual Reviews on Ecology Systematics 36, 295–317.
d'Hondt, S., Donaghay, P., Zachos, J.C., Luttenberg, D., Lindinger, M. 1998. Organic carbon fluxes and ecological recovery from the Cretaceous–Tertiary mass extinction. Science 282, 276–279.
El Deeb, W.Z.M. 1995. Startigraphy and peleoecology of the upper cretaceous sediments in north Western Desert, Egypt. Egyptian Petroleum Journal 4, 77–94.
El–Azabi, M.H., El–Araby, A. 2000. Depositional cycles: an approach to the sequence stratigraphy of the Dakhla Formation, west Dakhla–Farafra stretch, Western Desert, Egypt. Journal of African Earth Sciences 30, 971–996.
El–Bassiouni, A., Ayyad, S. N., Shahin, A. M., Shahin, S. M. 2003. Planktonic foraminiferal bio–and– chronostratigraphy of the upper Maastrichtian–middle Eocene succession in northeastern Sinai. Egypt. Journal of Palaeontology 3, 109–140.
Esmeray–Senlet, S., Wright, J., Olsson, R., Miller, K., Browning, J., Quan, T. 2015, Evidence for reduced export productivity following the Cretaceous/Paleogene mass extinction: Palaeoceanography 30, 718–738.
Faris, M., Allam, A., Marzouk, A.M. 1985. Biostratigraphy of the Late Cretaceous –Early Tertiary rocks in the Nile Valley (Qena region), Egypt. Ann. Geological Survey of Egypt 15, 278–300.
Farouk, S. 2014. Maastrichtian carbon cycle changes and planktonic foraminiferal bioevents at Gebel Matulla, westecentral Sinai, Egypt. Cretaceous Research 50, 238–251.
Farouk, S. 2016. Paleocene stratigraphy in Egypt. Journal of African Earth Sciences 113, 126–152.
Farouk, S. EL–Sorogy, E. 2015. Danian / Selandian unconformity in the central and southern Western Desert of Egypt. Journal of African Earth Sciences 103, 42–53.
Farouk, S., Faris, M. 2012. Late Cretaceous calcareous nannofossil and planktonic foraminiferal bioevents of the shallow–marine carbonate platform in the Mitla Pass, west central Sinai, and Egypt. Cretaceous Research 33, 50–65.
Farouk, S., Jain, S. 2016. Benthic foraminiferal response to relative sea–level changes in the Maastrichtian–Danian succession at the Dakhla Oasis, Western Desert, Egypt. Geological Magazine 2016, 1–18,
Farouk, S., Jain, S. 2017. Sea–level changes in the Palaeocene (Danian–Thanetian) succession at the Dakhla Oasis, Western Desert, Egypt: implications from benthic foraminifera. Proceedings of the Geologists' Association 128, 764–778.
Flexer, A., Reyment, R.A. 1989. Note on Cretaceous transgressive peaks and their relation to geodynamic events for the Arabo–Nubian and the northern African shields. Journal of African Earth Sciences 8, 65–73.
Fontanier, C., Jorissen, F.J., Licari, L., Alexandre, A., Anschutz, P., Carbonel, P. 2002. Live benthic foraminiferal faunas from the Bay of Biscay: faunal density, composition and microhabitats. Deep–Sea Research I 49, 751–785.
Friedrich, O., Erbacher, J. 2006. Benthic foraminiferal assemblages from Demerara Rise (ODP Leg 207, western Tropical Atlantic): possible evidence for a progressive opening of the Equatorial Atlantic Gateway. Cretaceous Research 27, 377–397.
Friedrich, O., Erbacher, J., Wilson, P.A., Moriya, K., Mutterlose, J. 2009. Paleoenvironmental changes across the Mid Cenomanian Event in the tropical Atlantic Ocean (Demerara Rise, ODP Leg 207) inferred from benthic foraminiferal assemblages. Marine Micropaleontology 71, 28–40.
Friedrich, O., Hemleben, C., 2007. Early Maastrichtian benthic foraminiferal assemblages from the western North Atlantic (Blake Nose) and their relation to palaeoenvironmental changes. Marine Micropalaeontology 62, 31–44.
Friedrich, O., Nishi, H., Pross, J., Schmiedl, G., Hemleben, C., 2005. Interruptions of the Oceanic Anoxic Event 1b (Lower Albian, Middle Cretaceous): evidence from benthic foraminiferal repopulation events. Palaios 20, 64–77.
Galal, G., Kamel, S. 2007. Early Paleogene Planktonic foraminiferal biostratigraphy at the Monastery of Saint Paul, Southern Galala, Eastern Desert, Egypt. Revue de Paléobiologie 26, 391–402.
Gebhardt, H., Kuhnt, W., Holbourn, A. 2004. Foraminiferal response to sea level change, organic flux and oxygen deficiency in the Cenomanian of the Tarfaya Basin, southern Morocco. Marine Micropaleontology 53, 133–157.
Giusberti, L., Coccioni, R., Sprovieri, M., Tateo, F. 2009. Perturbation at the sea floor during the Paleocene–Eocene thermal maximum: evidence from benthic foraminifera at Contessa Road, Italy. Marine Micropaleontology 70, 102–119.
Gooday A.J., Bett B.J., Shires R., Lambshead P.J.D. 1998. Deep–sea benthic foraminiferal diversity in the NE Atlantic and NW Arabian sea: a synthesis. Deep–Sea Research II 45, 165–201.
Gooday, A.J. 2003. Benthic foraminifera (Protista) as tools in deepwater palaeoceanography: environmental influences on faunal characteristics. Advances in Marine Biology 46, 1–90.
Haq, B.U., 2014. Cretaceous eustasy revisited. Global Planet Change 113, 44–58.
Heinz, P., Ruepp, D., Hemleben, C. 2004. Benthic foraminifera assemblages at Great Meteor Seamount. Marine Biology 144, 985–998.
Hendriks, F., Luger, P., Kallenbach, H., Schroeder, J.H. 1984. Stratigraphical and sedimentological framework of the Kharga–Sinn El–Kaddab stretch (western and southern part of the Upper Nile Basin), Western Desert, Egypt. Berliner Geowiss. Abh., (A) 50, 117–151.
Hess, S., Kuhnt, W. 2005. Neogene and Quaternary palaeoceanographic changes in the southern South China Sea (Site 1143): the benthic foraminiferal record. Marine Micropalaeontology 54, 63–87.
Hollis, C.J., Strong, C.P., Rodgers, K.A., Rogers, K.M. 2003. Palaeoenvironmental changes across the Cretaceous/Tertiary boundary at Flaxbourne River and Woodside Creek, Eastern Marlborough New Zealand. New Zealand Journal of Geology and Geophysics 46, 177–197.
Hsü, K.J., McKenzie, J. 1985. A “Strangelove Ocean” in the earliest Tertiary. Geophysics Monograph 32, 487–492.
Huber, B.T., 1988. Upper Campanian–Paleocene foraminifera from the James Ross Island region, Antarctic Peninsula. Geological Society of America, Memoir 169, 163–252.
Hull, P.M., Norris, R.D. 2011. Diverse patterns of ocean export productivity change across the Cretaceous–Paleogene boundary: New insights from biogenic barium. Palaeoceanography 26 (3), PA 3205. http://dx.doi.org/10.1029/2010PA002082.
Issawi, B., 1972. Review of Upper Cretaceous–Lower Tertiary stratigraphy in central and southern Egypt. American Association of Petroleum Geologist Bulletin 56, 1448–1473.
Jain, S. 2011. Changes in Late Neogene Caribbean Benthic Foraminifers: Palaeoproductivity, Diversity and Test Size, Lap Lambert Academic Publishing Gmbh and Co. Kg., Germany, 150 p.
Jain, S., Collins, L.S. 2007. Trends in Caribbean palaeoproductivity related to the Neogene closure of the Central American seaway. Marine Micropalaeontology 63, 57–74.
Jain, S., Collins, L.S., Hayek, Lee–Ann. C. 2007. Relationship of benthic foraminiferal diversity to palaeoproductivity in the Neogene Caribbean. Palaeogeography, Palaeoclimatology, Palaeoecology 255, 223–245.
Jain, S., Farouk, S. 2017. Shallow Water Agglutinated Foraminiferal response to Late Cretaceous – early Palaeocene sea–level changes in the Dakhla Oasis, Western Desert, Egypt. Cretaceous Research 78, 240–257.
Jannink, N.T., Van der Zwaan, G.J., Almogi–Labin, A., Duijnstee, I., Jorissen, F.J. 2001. A transfer function for the quantitative reconstruction of oxygen contents in marine palaeoenvironments. Geologica Ultraiectina 203, 161–169.
Jones, R.W. 1999. Forties Field (North Sea) revisited; a demonstration of the value of historical micropalaeontontological data. In: Jones, R.W., Simmons, M.D. (Eds.), Biostratigraphy in Production and Development Geology. Geological Society, London, Special Publication 152, 185–200.
Jones, R.W., Charnock, M.A. 1985. Morphogroups of agglutinated foraminifera. Their life positions and feeding habits and potential applicability in (palaeo) ecological studies. Revue de Paléobiologie 4, 311–320.
Jones, R.W., Pickering, K.T., BouDagher–Fadel, M., Matthews, S. 2005. Preliminary observations on the micropalaeontological characterisation of submarine fan / channel sub–environments, Ainsa system, south–central Pyrenees, Spain. In: Powell, A.J., Riding, J.B. (Eds.), Recent Developments in Applied Biostratigraphy: The Micropalaeontological Society, Special Publication 1, 55–68.
Jorissen, F.J. 1988. Benthic foraminifera from the Adriatic Sea: principles of phenotypic variation. Utrecht Micropalaeontological Bulletin 37, 174 pp.
Jorissen, F.J. 1999. Benthic foraminiferal microhabitats below the sediment–water interface. In: Sen Gupta, B.K. (Ed.), Modern Foraminifera. Kluwer Academic Press, Dordrecht, pp. 161–179.
Jorissen, F.J., Barmawidjaja, D.M., Puskaric, S., Van der Zwaan, G.J. 1992. Vertical distribution of benthic foraminifera in the northern Adriatic Sea; the relation with the organic flux. Marine Micropalaeontology 19, 1–2.
Jorissen, F.J., De Stigter, H.C., Widmark, J.G. 1995. A conceptual model explaining benthic foraminiferal microhabitats. Marine Micropalaeontology 22, 3–15.
Jorissen, F.J., Fontanier, C., Thomas, E. 2007. Palaeoceanographical proxies based on deep–sea benthic foraminiferal assemblage characteristics. In Proxies in Late Cenozoic Palaeoceanography, Volume 1. Developments in Marine Geology, Ed. Hillaire–Marcel, C., Vernal, A. De, pp. 263–325.
Jorissen, F.J., Wittling, I., Peypouquet, J.P., Rabouille, C., Relexans, J.C. 1998. Live benthic foraminiferal faunas off Cap Blanc, NW Africa: community structure and microhabitats. Deep–Sea Research I45, 2157–2188.
Kaiho, K. 1991. Global changes of Paleogene aerobic/anaerobic benthic foraminifera and deep–sea circulation. Palaeogeography, Palaeoclimatology, Palaeoecology 83, 65–85.
Kaiho, K. 1994. Benthic foraminiferal dissolved–oxygen index and dissolved–oxygen levels in the modern ocean. Geology 22, 719–722.
Kaminski, M.A., Aksu, A., Box, M., Hiscott, R.N., Filipescu, S., Al–Salameen, M. 2002. Late Glacial to Holocene benthic foraminifera in the Marmara Sea: implications for Black Sea–Mediterranean Sea connections following the last deglaciation. Marine Geology 190, 165–202.
Kaminski, M.A., Boersma, A., Tyszka, J., Holbourn, A. 1995. Response of deep–water agglutinated foraminifera to dysoxic conditions in the California borderland basins. In: Kaminski, M.A., Geroch, S., Gasinski, M.A. (Eds.), Proceedings of the Fourth International Workshop on Agglutinated Foraminifera: Grzybowski Foundation Special Publication 3, 131–140.
Kaminski, M.A., Gradstein, F.M. 2005. Atlas of Paleogene cosmopolitan deepwater agglutinated foraminifera. Grzybowski Foundation Special Publication, 10, 574 pp.
Keller, G. 1988. Biotic turnover in benthic foraminifera across the Cretaceous–Tertiary boundary at El Kef, Tunisia. Palaeogeography, Palaeoclimatology, Palaeoecology 66, 153–171.
Keller, G. 1992. Paleoecologic response of Tethyan benthic foraminifera to the Cretaceous–Tertiary boundary transition. In: Takayanagi, Y., Saito, T. (Eds.), Studies in Benthic Foraminifera. Tokai University Press, Tokyo, pp. 77–91.
Keller, G., Adatte, T., Stinnesbeck, W., Stueben, D., Kramar, U., Berner, Z., Li, L., Von Salis Perch–Neilsen, K. 1998. The Cretaceous–Tertiary transition on the shallow Saharan Platform of southern Tunisia. Geobios 30, 951–975.
Kender, S., Kaminski, M.A., Jones, R.W. 2008a. Oligocene deep–water agglutinated foraminifera from the Congo Fan, offshore Angola: palaeoenvironments and assemblage distributions. In: Kaminski, M.A., Coccioni, R. (Eds.), Proceedings of the Seventh International Workshop on Agglutinated Foraminifera: Grzybowski Foundation Special Publication 13, 107–156.
Kender, S., Kaminski, M.A., Jones, R.W. 2008b. Early to middle Miocene foraminifera from the deep–sea Congo Fan, offshore Angola. Micropaleontology 54, 477–568.
Khalil, H., Al Sawy, S. 2014. Integrated biostratigraphy, stage boundaries and Paleoclimatology of the Upper Cretaceous–Lower Eocene successions in Kharga and Dakhala Oases, Western Desert, Egypt. Journal of African Earth Sciences 96, 220–242.
Koutsoukos, A.M., Hart, M.B. 1990. Cretaceous foraminiferal morphogroup distribution patterns, palaeocommunities and trophic structures: a case of study from the Sergipe Basin, Brazil. Transactions of the Royal Society of Edinburgh, Earth Sciences 81, 221–246.
Koutsoukos, E.A.M., Leary, P.N., Hart, M.B. 1990. Latest Cenomanian–earliest Turonian low–oxygen tolerant benthonic foraminifera: A case study from the Sergipe Basin (N.E. Brazil) and the western Anglo–Paris Basin (Southern England). Palaeogeography, Palaeoclimatology, Palaeoecology 77, 145–177.
Langer M. R. 1993. Epiphytic foraminifera. Marine Micropaleontology 20, 235–265.
Levin, L.A., Etter, R.J., Rex, M.A., Gooday, A.J., Smith, C.R., Pineda, J., Stuart, C.T., Hassler, R.R., Pawson, D. 2001. Environmental influences on regional deep–sea species diversity. Annual Reviews of Ecology Systematic 32, 51–93.
Li, L., Keller, G., Adatte, G., Stinnesbeck, W. 2000. Late Cretaceous sea level changes in Tunisia: a multi–disciplinary approach. Geological Society of London 157, 447–458.
Li, L., Keller, G., Stinnesbeck, W. 1999. The late Campanian and Maastrichtian in northwestern Tunisia: palaeoenvironmental inferences from lithology, macrofauna and benthic foraminifera. Cretaceous Research 20, 231–252.
Linke, P. 1992. Metabolic adoptions of deep–sea benthic foraminifera to seasonally varying food input. Marine Ecology Progress Series 81, 51–63.
Linke, P., Lutze, G.F. 1993. Microhabitat preferences of benthic foraminifera ^ a static concept or a dynamic adaptation to optimize food acquisition? Marine Micropalaeontology 20, 215–234.
Luger, P. 1985. Stratigraphie der marinen Oberkreide und des Alttertiars im Sudwestlichen Obernil–Becken (SW–Aegypten) unterbesonderer berucksichtigung der mikropaläontologie, paläoekologie und paläogeographie. Berliner geowiss. Abh. (A) 63, Berlin, pp.1–150.
Luger, P. 1988. Maastrichtian to Paleocene facies evolution and Cretaceous/Tertiary boundary in middle and southern Egypt. Rev. Espan. Micropaleontol., Numero Extraord., 83–90.
Mackensen, A., Grobe, H., Kuhn, G., Fütterer, D.K. 1990. Benthic foraminiferal assemblages from the eastern Weddell Sea between 68° and 73°S: distribution, ecology and fossilization potential. Marine Micropalaeontology 16, 241–283.
Mackensen, A., Schmiedl, G., Harloff, J., Giese, M. 1995. Deep–sea foraminifera in the South Atlantic Ocean: ecology and assemblage generation. Micropalaeontology 41, 342–358.
Miller, K.G., Janecek, T.R., Katz, M., E., Keil, D.J. 1987. Stable carbon and oxygen isotope record of benthic foraminifera from Paleocene–Eocene sediments. Paleoceanography 2, 741–761.
Murray, J.W. 2001. The niche of benthic foraminifera, critical thresholds and proxies. Marine Micropalaeontology 41, 1–8.
Murray, J.W., Alve, E., Jones, B.W. 2011. A new look at modern agglutinated benthic foraminiferal morphogroups: their value in palaeoecological interpretation. Palaeogeography, Palaeoclimatology, Palaeoecology 309, 229–241.
Nagy, J. 1992. Environmental significance of foraminiferal morphogroups in Jurassic North Sea deltas. Palaeogeography, Palaeoecology, Palaeoclimatology 95, 111–134.
Nagy, J., Gradstein, F.M., Kaminski, M.A., Holbourn, A.E.L. 1995. Late Jurassic to Early Cretaceous foraminifera of Thakkhola, Nepal: Palaeoenvironments and description of new taxa. In: Kaminski, M.A., Geroch, S., Gasinski, M.A. (Eds.), Proceedings of the Fourth International Workshop on Agglutinated Foraminifera. Grzybowski Foundation Special Publication 3, 181–209.
Nagy, J., Hess, S., Alve, E. 2010. Environmental significance of foraminiferal assemblages dominated by small–sized Ammodiscus and Trochammina in Triassic and Jurassic delta–influenced deposits. Earth–Science Reviews 99, 31–49
Nagy, J., Pilskog, B., Wilhelmsen, R. 1990. Facies controlled distribution of foraminifera in the Jurassic North Sea Basin. In: Hemleben, C., Kaminski, M.A., Kuhnt, W., Scott, D. B. (Eds.), Papleoecology, Biostratigraphy, Paleoceanography and Taxonomy of Agglutinated Foraminifera. Kluwer Academic Press, Dordrecht, the Netherlands, pp. 621–657.
Nagy, J., Reolid, M., Rodríguez–Tovar, F.J. 2009. Foraminiferal morphogroups in dysoxic shelf deposits from the Jurassic of Spitsbergen. Polar Research 28, 214–221.
Obaidalla, N.A. 2005. Complete Cretaceous/Paleogene (K/P) boundary section at Wadi Nukhul, southwestern Sinai, Egypt: inference from planktic foraminiferal biostratigraphy. Revue de Paléobiologie 24, 201–224.
Olsson, R.K. 1960. Foraminifera of latest Cretaceous and earliest Tertiary age in the New Jersey coastal plain. Journal of Paleontology 34, 1–58.
Olsson, R.K., Chengjie, Liu, van Fossen, M., 1996. The Cretaceous–Tertiary catastrophic event at Millers Ferry, Alabama. In: Ryder, G., Fastovsky, D., Gartner, S. (Eds.), The Cretaceous–Tertiary Event and Other Catastrophes in Earth History. Geological Society of America, Special Paper 307, 263–277.
Orabi, H.O., 1995. Biostratigraphy and paleoecology of the Campanian–Paleocene agglutinated foraminifera from Gebel Um El Ghanayim Kharga Oasis, Egypt. Science Journal Faculty of Science, Menoufia University 11, 25–68.
Orabi, O.H. 2000. Foraminiferal morphogroups and paleoenvironments of some Upper Cretaceous exposures in Egypt. Egyptian Journal of Geology 44, 359–397.
Orabi, O.H., Khalil, H.M. 2014. Calcareous benthonic foraminifera across the Cretaceous / Palaeocene transition of Gebel Um El–Ghanayem, Kharga Oasis, Egypt. Journal of African Earth Sciences 96, 110–121.
Perez–Cruz, L.L., Machain–Castillo, M.L. 1990. Benthic foraminifera of the oxygen minimum zone, continental shelf of the Gulf of Tehuantepec, Mexico. Journal of Foraminiferal Research 20, 312–325.
Peryt, D., Alegret, L., Molina, E. 2002. The Cretaceous/Paleogene (K/P) boundary at Aìn Settara, Tunisia: restructuring of benthic foraminiferal assemblages. Terra Nova 14, 101–107.
Peryt, D., Alegret, L., Molina, E. 2004. Agglutinated foraminifers and their response to the Cretaceous/Paleogene (K/P) boundary event at Ain Settara, Tunisia. In: Bubik, M., Kaminski, M.A. (Eds.), Proceedings of the Sixth International Workshop on Agglutinated Foraminifera. Grzybowski Foundation Special Publication 8, 393–412.
Phleger, F.B., Soutar, A. 1973. Production of benthic foraminifera in three East Pacific oxygen minima. Micropalaeontology 19, 110–115
Plummer, H.J., 1927. Foraminiferal of the Midway Formation in Texas. University of Texas Bulletin 2644, 3–206.
Preece, R.C., Kaminski, M.A., Dignes, T.W. 1999. Miocene benthonic foraminiferal morphogroups in an oxygen minimum zone, offshore Cabinda. In: Cameron, N.R., Bate, R.H., Clure, V.S. (Eds.), The oil and gas habitats of the South Atlantic: Geological Society, London, Special Publications 153, 267–282.
Rathburn, A.E., Corliss, B.H. 1994. The ecology of living (stained) deep–sea benthic foraminifera from the Sulu Sea. Palaeoceanography 9, 87–150.
Reolid, M., Rodríguez–Tovar, F.J., Nagy, J. 2012. Ecological replacement of Valanginian agglutinated foraminifera during a maximum flooding event in the Boreal realm (Spitsbergen). Cretaceous Research 33, 196–204.
Reolid, M., Rodríguez–Tovar, F.J., Nagy, J., Olóriz, F. 2008. Benthic foraminiferal morphogroups of mid to outer shelf environments of the Late Jurassic (Prebetic Zone, Southern Spain): Characterisation of biofacies and environmental significance. Palaeogeography, Palaeoclimatology, Palaeoecology 261, 280–299.
Romein, A.J.T., Smit, J. 1981. The Cretaceous/Tertiary boundary: calcareous nannofossils and stable isotopes. Proc. K. Ned. Akad. Wet. Ser. B 84, 295–314.
Scheibner, C., Kuss, J., Speijer, R.P. 2003. Stratigraphic modeling of carbonate plateform–to–basin sediments (Maastrichtian to Palaeocene) in the Eastern Desert, Egypt. Palaeogeography, Palaeoclimatology, Palaeoecology 3136, 1–23.
Schmiedl, G., Mackensen, A., Müller, P.J. 1997. Recent benthic foraminifera from the eastern South Atlantic Ocean: dependence on food supply and water masses. Marine Micropalaeontology 32, 249–287.
Schmitz, B., Keller, G., Stenvall, O. 1992. Stable isotope and foraminiferal changes across the Cretaceous–Tertiary boundary at Stevns Klint, Denmark: arguments for long–term oceanic instability before and after bolide–impact event. Palaeogeography, Palaeoclimatology, Palaeoecology 96, 233–260.
Sen Gupta, B.K. 1999. Introduction to modern Foraminifera. In: Sen Gupta, B.K. (Ed.), Systematics of Modern Foraminifera. Kluwer Academic Publishers, Dordrecht, Netherlands, pp. 7–36.
Sen Gupta, B.K., Machain Castillo, M.L. 1993. Benthic foraminifera in oxygen–poor habitats. Marine Micropalaeontology 20, 3–4.
Severin, K.P., Erskian, M.G. 1981. Laboratory experiments on the vertical movement of Quinqueloculina impressa Reuss through sand. Journal of Foraminiferal Research 11, 133–136.
Sibert, E., Hull, P., and Norris, D. 2014, Resilience of Pacific pelagic fish across the Cretaceous/Paleogene mass extinction: Nature Geoscience 7, 667–670.
Sikora, P.J. 1984. Quantitative analysis of Foraminifera from the Kemp Clay, north–central Texas. MS Thesis, University of Texas.
Sjoerdsma, P.G., Van der Zwaan, G.J. 1992. Simulating the effect of changing organic flux and oxygen content on the distribution of benthic foraminifers. Marine Micropalaeontology 19, 1–2.
Sliter, W.V. 1968. Upper Cretaceous foraminifera from southern California and northwestern Baja California, Mexico. The University of Kansas Paleontoogical Contribution, pp. 1–141. Art. 7.
Sliter, W.V., Baker, A. 1972. Cretaceous bathymetric distribution of benthic foraminifera. Journal of Foraminiferal Research 2, 167–183.
Speijer, R.P., van der Zwaan, G.J. 1996. Extinction and survivorship of southern Tethyan benthic foraminifera across the Cretaceous/Paleogene boundary. In: Hart, M.B. (Ed.), Biotic Recovery from Mass Extinction Events. Geological Society Special Publication 102, 343–371.
Sprong, J., Kouwenhoven, T.J., Bornemann, A., Dupuis, C., Speijer, R.P, Stassen, P., Steurbaut, E. 2013. In search of the Latest Danian Event in a paleobathymetric transect off Kasserine Island, north–central Tunisia. Palaeogeography, Palaeoclimatology, Palaeoecology 379–380, 1–16.
Strougo, A., 1986. The Velascoensis event: A significant episode of tectonic activity in the Egyptian Paleogene. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 173, 253–269.
Tantawy, A.A., Keller, G., Adatte, T., Stinnesbeck, W., Kassab, A., Schulte, P., 2001. Maastrichtian to Paleocene depositional environment of the Dakhla Formation, Western Desert, Egypt: Sedimentology, mineralogy, and integrated micro– and macrofossil biostratigraphies. Cretaceous Research 22, 795–827.
Thomas, E. 1990. Late Cretaceous–early Eocene mass extinctions in the deep sea. In: Sharpton, V.L., Ward, P.D. (Eds.), Global Catastrophes in Earth history. Geological Society of America. Special Publication 247, 481–495.
Thomas, E., Gooday, A.J. 1996. Cenozoic deep–sea benthic foraminifers: tracers for changes in oceanic productivity? Geology 24, 355–358.
Thomas, E., Shackleton, N.J. 1996. The Paleocene–Eocene benthic foraminiferal extinction and stable isotope anomalies. In: Knox, R.W., Corfield, R.M., Dunay, R.E. (Eds.), Correlation of the Early Paleogene in Northwest Europe. Geological Society of London Special Publication 101, 401–441.
Tribovillard, N., Dupuis, C., Robin, E., 2000. Sedimentological and diagenetical conditions of the impact level of the Cretaceous/Tertiary boundary in Tunisia: no anoxia required. Bulletin de la Société géologique de France 171, 629–636.
Tyszka, J. 1994. Response of Middle Jurassic benthic foraminiferal morphogroups to dysoxic/anoxic conditions in the Pieniny Klippen Basin, Polish Carpathians. Palaeogeography, Palaeoecology, Palaeoclimatology 110, 55–81.
van der Akker, T.J.H.A., Kaminski, M.A., Gradstein, F.M., Wood, J. 2000. Campanian to Palaeocene biostratigraphy and palaeoenvironments in the Foula Sub–basin, west of the Shetland Islands, UK. Journal of Micropalaeontology 19, 23–43.
Van der Zwaan, G.J., Duijnstee, I.A.P., Den Dulk, M., Ernst, S.R., Jannink N.T., Kouwenhoven, T.J. 1999. Benthic foraminifers: proxies or problems? A review of palaeoecological concepts. Earth–Science Reviews 46, 213–236.
Voigt, S., Gale, A.S., Jung, C., Jenkyns, H.C. 2012. Global correlation of Upper Campanian–Maastrichtian successions using carbon-isotope stratigraphy: development of a new Maastrichtian timescale. Newsletters on Stratigraphy 45, 25–53.
Widmark, J.G.V. 2000. Biogeography of terminal Cretaceous benthic foraminifera: deep–water circulation and trophic gradients in the deep South Atlantic. Cretaceous Research 21, 367–379.
Widmark, J.G.V., Malmgren, B. 1992. Benthic foraminiferal changes across the Cretaceous–Tertiary boundary in the deep sea; DSDP sites 525, 527 and 465. Journal of Foraminiferal Research 22, 81–113.
Widmark, J.G.V., Speijer, R.P. 1997. Benthic foraminiferal ecomarker species of the terminal Cretaceous (late Maastrichtian) deepsea Tethys. Marine Micropaleontology 31, 135–155.
Wollenburg, J.E., Kuhnt, W. 2000. The response of benthic foraminifers to carbon flux and primary production in the Arctic Ocean. Marine Micropalaeontology 40, 189–231.
Wollenburg, J.E., Mackensen, A. 1998. Living benthic foraminifers from the central Arctic Ocean: faunal composition, standing stock and diversity. Marine Micropalaeontology 34, 153–185.

Table 1. Benthic foraminiferal morphogroups and submorphogroups categorized in this study (modified after Koutsoukos and Hart, 1990).

Morpho-groups		Sub-groups	General morphotypes	Chamber number	Inferred microhabitat	Inferred trophic group	Species (This study)
CH	A	1	plano-convex, low / high trochospiral broad	multilocular	epifaunal	deposit feeders	Gyroidinoides girardana and G. globusa
		2	concave-convex, low trochospiral broad		epifaunal		Valvalabamina planulata, V. depressa, Valvulineria aegyptiaca, V. esnehensis, V. scrobiculata and Siphonina prima.
		3	Inflated, biconvex periphery broadly rounded		epifaunal / shallow infaunal		Nonionella africana, N. insect, Gavelinella brotzeni, G. paleocenica
		4	conical, low trochospiral		epifaunal	deposit feeders and passive herbivores (browsers)	Alabemina midwayensis, A. wilcohensis, Anomalinoides acutus, A. aegyptiacus, A. affinis, A. midwayensis, A. praeacutus, A. pseudoacutus, A. simplex, A. umboniferus, A. zitllie, Cibicides beaumontianus, C. decoratus, C. farafraensis, C. praecursorius, C. tappanae, Cibicidoides abudurbensis, C. harperi, C. howelli, C. libycus, C. melhaensis, C. phraonis, C. pseudoperlucidus, Discorbis pseudoscopus and Rotalia calcariformis
		5	lenticular, low trochospiral periphery subacute / carinate		epifaunal	deposit feeders	Epistomina esnahensis, Oridorsalis plummerae, Osangularia expanse, O. plummarae and O. desertorum
		6	lenticular, low planispiral periphery subacute / carinate		epifaunal / shallow infaunal	deposit feeders	Lenticulina alabamensis, L. cultrate, L. discrepans, L. midwayensis, L. muensteri, L. pseudosecans, L. rotulata, L. spisso-coslatus and L. navicula
		7	conical, low / high trochospiral	bilocular	epifaunal	deposit feeders and passive herbivores (browsers)	Not recorded
		8	discoidal-flattened	bilocular	epifaunal	deposit feeders	Not recorded
	B	1	globular / ovate to elongate/ fusiform	bilocular/ multilocular	epifaunal / infaunal		Globulina lacrima
		2	broad to palmate, compressed planispiral to uncoiled uniserial	multilocular			Frondicularia archiaciana, F. lanceola, Neoflabellina suturalis, Palmula woodi, Vaginulina longiformis, V. cretacea, V. plummarae, V. suturalis, V. taylorana and V. trilobata
		3	elongate, straight to arcuate uniserial or planispiral-uniserial				Dentalina delicatula, Laevidentalina basiplanata, L. colei, Marginulinopsis intercostata, M. tuberculate, Nodosaria radicula, Pseudonodosaria lagenoides, P. manifesta and Ramulina navarroana
		4	tapered rounded - elongate triserial - biserial - uniserial		infaunal		Bolivina cretosa, B. decurrans, Bulimina prolixa, B. strobili, Cassidulina globosa, Lacosteina maquawilensis, Neobulimina canadaensis, N. khagaensis, Orthokarstenia esnahensis, O. higazi, O. oveyi, O. parva, Praebulimina carseyae, P. kikapoensis, P. russi, Pseudouvigerina cretacea, Pyramidulina affinis, P. distans, P. semispinosa, P. vertebralis, P. zippei and Reussella aegyptiaca
		5	tapered flattened-elongate biserial		infaunal		Coryphostoma platium, Eouvigerina aegyptiaca, Tappanina selmensis, Vaginulinopsis austinana, Elhasaella alanwoodi and Siphogenrinoides eleganta
CP	A		fusiform., compressed broad	multilocular	epifaunal	deposit feeders	Not recorded
CP	B		elongate to ovate quinqueloculine	multilocular	epifaunal / shallow infaunal	deposit feeders	Quinquloculina gussensis
AG	A		elongate, variable coiling uniserial and multiserial	multilocular	infaunal	deposit feeders	Ammoastuta megacribrostomoides, Ammobaculites alexanderi, A. coprolithiformis, A. expansus, A. fragmentarius, A. impexus, A. junceus, A. khargaensis, A. stehensoni, A. subcretaceous, A. texana, Clavulinoides trilaterus, Gaudryina africana, G. austinana, G. limbata, G. pyramidata, G. soldadoensis, Pseudoclavulina farafraensis, Reophax texanus, Spiroplectinella esnaensis, S. henryi, S. knebeli, S. laevis, S. longa and Verneuilina karreri
	B	1	low trcochospiral / planispiral broad		epifaunal	deposit feeders and passive herbivores (browsers)	Trochammina albertensis, T. bohemi, T. deformis, T. diagonis, T. globigeriniformis, T. mellariolum, T. rainwateri, T. ribstonensis, T. rutherfordi, T. simplex, T. texana and T. umiatensis.
		2	low trochospiral / streptospiral / planispiral, spherical / subspherical		epifaunal / shallow infaunal	deposit feeders	Cribrostomoides cretacea, C. trinitatensis, Haplophragmoides advenus, H. calcula, H. excavata, H. glabra, H. gracilis, H. hausa, H. kirki, H. nigeriense, H. sahariense, Ammodiscus cretacea, Ammomarginulina aubertae and Flabillammina chapmani.
		3	streptospiral / planispiral / subspherical / flattened	bilocular / multilocular			Not recorded
		4	globular	unilocular			Not recorded
	C		tubular or branching	unilocular	epifaunal	suspension feeders	Bathysiphon arenaceous and B. eocenicus

Table 2. Seven scenarios (a–g) are explored to access neritic benthic foraminiferal changes at the K/Pg boundary ranging from an analysis of an assemblage below and above the boundary (scenario “a”, Assemblages 10 and 11, 26 samples; the boundary is drawn between samples 200 and 201) to a more extended interval (scenarios “f” and “g”). The lower panel summarizes the result of the seven scenarios (a–g). See Fig. 7 for benthic foraminiferal assemblages.

	DISAPPEARENCES
	[a]			[b]			[c]
	Assemblage	Samples		Assemblage	Samples		Assemblage	Samples
	11	16		11+12	38		11+12	38
	10	10		10	10		9+10	36

	Agglutinated species			Agglutinated species			Agglutinated species
	Survivors	2	10%	Survivors	2	9%	Survivors	9	32%
	Absent after K/Pg	2	10%	Absent after K/Pg	2	9%	Absent after K/Pg	7	25%
	Present after K/Pg	16	80%	Present after K/Pg	19	83%	Present after K/Pg	12	43%

	Calcareous species			Calcareous species			Calcareous species
	Survivors	5	9%	Survivors	3	6%	Survivors	7	13%
	Absent after K/Pg	17	32%	Absent after K/Pg	19	36%	Absent after K/Pg	16	30%
	Present after K/Pg	31	58%	Present after K/Pg	31	58%	Present after K/Pg	30	57%

	Overall species			Overall species			Overall species
	Survivors	7	10%	Survivors	5	7%	Survivors	16	20%
	Absent after K/Pg	19	26%	Absent after K/Pg	21	28%	Absent after K/Pg	23	28%
	Present after K/Pg	47	64%	Present after K/Pg	50	66%	Present after K/Pg	42	52%
	[d]			[e]
	Assemblage	Samples		Assemblage	Samples
	11 to 13 (up to P2)	47		11 to 13	54
	9+10	36		9+10	36

	Agglutinated species			Agglutinated species
	Survivors	8	28%	Survivors	8	26%
	Absent after K/Pg	7	24%	Absent after K/Pg	7	23%
	Present after K/Pg	14	48%	Present after K/Pg	16	52%

	Calcareous species			Calcareous species
	Survivors	5	8%	Survivors	6	9%
	Absent after K/Pg	18	28%	Absent after K/Pg	17	25%
	Present after K/Pg	42	65%	Present after K/Pg	46	67%

	Overall species			Overall species
	Survivors	13	14%	Survivors	14	14%
	Absent after K/Pg	25	26%	Absent after K/Pg	24	24%
	Present after K/Pg	56	59%	Present after K/Pg	62	61%

	EXTINCTIONS
	[f]			[g]
	Assemblage	Samples		Assemblage	Samples
	11 to 18 (up to P4)	258		11–16 (E. Paleo.)	84
	9+10	36		8+10 (U Mast.)	52

	Agglutinated species			Agglutinated species
	Survivors	8	25%	Survivors	12	26%
	Absent after K/Pg	7	22%	Absent after K/Pg	18	38%
	Present after K/Pg	17	53%	Present after K/Pg	17	36%

	Calcareous species			Calcareous species
	Survivors	6	6%	Survivors	26	28%
	Absent after K/Pg	37	37%	Absent after K/Pg	37	40%
	Present after K/Pg	58	57%	Present after K/Pg	29	32%

	Overall species			Overall species
	Survivors	14	11%	Survivors	38	27%
	Absent after K/Pg	44	33%	Absent after K/Pg	55	40%
	Present after K/Pg	75	56%	Present after K/Pg	46	33%
[h]
Sc.	Agglutinated species			Calcareous species		Overall	Samples
[a]	10%		Disappearances	26%		26%	26
[b]	9%			28%		28%	48
[c]	25%			30%		28%	74
[d]	28%			26%		26%	83
[e]	29%			25%		24%	90
[f]	22%		Extinctions	33%		33%	294
[g]	38%		Extinctions	40%		40%	136

Table 3. Benthic foraminiferal changes before and after the K/Pg boundary between samples (200 and 201) and Assemblages (10 and 11). See text for explanation and Fig. 7 for benthic foraminiferal assemblages.

		% Oxic species	%oxyphilic taxa	% Epifaunal (minus E/SI) species	BFOI	% Infaunal (DI+SI; minus E/SI) species	% Infaunal (E/SI included)	% HOFS	Fisher' α	%P	CH-A.4	CH-B.4	CH-B.5	AG-A	AG-B.2
Sample	201	64.3	425.9	41.7	1.1	31.3	36.6	0.0	1.87	63	33.9	0.9	0.9	0.0	5.2
Sample	200	30.8	603.0	30.8	0.6	0	23.1	0.0	0.8	0	7.7	0.0	0.0	0.0	0.0
Assemblage	11	61.3	436.2	48.4	14.4	22.4	33.4	4.3	2.1	51.2	42.1	7.1	7.1	1.5	6.2
Assemblage	10	26.0	182.0	28.9	2.5	50.4	34.1	5.4	0.2	0.0	38.5	59.3	59.3	0.9	0.0
Table 3

No competing interests reported.

AppendicesTables18.docx

Download PDF

Journal Publication

published 01 Feb, 2023

Read the published version in Geo-Marine Letters →

Editorial decision: Major revision
10 Nov, 2022
Editor assigned by journal
08 Nov, 2022
Submission checks completed at journal
03 Nov, 2022
First submitted to journal
28 Oct, 2022

You are reading this latest preprint version

Relationship of Maastrichtian–Thanetian benthic foraminiferal species diversity, palaeooxygenation and palaeoproductivity in shallow waters of Western Desert, Egypt

Status:

Journal Publication

Version 1

Abstract

Figures

1. Introduction

2. Geological Setting

3. Barren Intervals

4. Previous Studies

5. Methods

6. Results

6.1. Species diversity

6.2. Palaeoproductivity proxies

6.2.1. High organic–flux species (% HOFS)

6.2.2. Percent Infaunal

6.3. Oxygenation proxies

6.3.1. % Oxyphilic taxa

6.4. Morphogroups and subgroups

6.5. Wall structure

6.6. Statistical analysis

6.7. Changes at the K/Pg boundary

6.7.1. Comparative accounts

6.7.2. Present data

7. Discussion

8. Conclusions

Declarations

References

Tables

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1