The Magnitude of Exhumation in the Kidson Sub- basin, Western Australia, using Thermal and Compaction Techniques

The Kidson Sub-basin which forms the largest tectonic province of the Canning Basin has high potential for Uranium, sediment-hosted base metals, conventional and unconventional hydrocarbons. The basin has undergone major tectonic events since its formation in the Early Ordovician involving several inversion episodes resulting in extensive exhumation in the basin. The magnitude, timing and distribution of exhumation associated with these inversion episodes are poorly studied due to sparse data in the area. In this study, we integrate recently acquired seismic and well data with existing well data, combining for the first time thermal and compaction techniques to constrain the magnitude and distribution of exhumation associated with these major inversion episodes. Our results from vitrinite reflectance indicate that at least 300 to 500 m of exhumation occurred during the middle Silurian to Early Devonian inversion episode (Prices Creek Compression), 500 to 750 m of exhumation occurred during the middle Carboniferous inversion episode or Meda Transpression and 800 to 1200 m of exhumation occurred during the Late Triassic to Early Jurassic inversion episode, or Fitzroy Transpression. Data from apatite fission track analysis put temporal constraints on the timing of this exhumation and indicate that a paleo-thermal maximum was reached within the Kidson Sub-basin during the Late Triassic extensional event. During this period, we also detect that the sediments were affected by a slight increase in basal heat flow associated with the rifting event. The results from this study also demonstrate that the magnitude of exhumation generally increased with each exhumation period progressively. We suggest that this may have occurred due to the progressive weakening of inherited basement units during each phase. Results also illustrate that each of these inversion events had a much higher impact on the exhumation of the Kidson Sub-basin than previously thought. Manuscript

Our results from vitrinite reflectance indicate that at least 300 to 500 m of exhumation occurred during the middle Silurian to Early Devonian inversion episode (Prices Creek Compression), 500 to 750 m of exhumation occurred during the middle Carboniferous inversion episode or Meda Transpression and 800 to 1200 m of exhumation occurred during the Late Triassic to Early Jurassic inversion episode, or Fitzroy Transpression. Data from apatite fission track analysis put temporal constraints on the timing of this exhumation and indicate that a paleo-thermal maximum was reached within the Kidson Sub-basin during the Late Triassic extensional event. During this period, we also detect that the sediments were affected by a slight increase in basal heat flow associated with the rifting event.

Introduction
The Kidson Sub-basin is a part of the onshore Canning Basin in Western Australia (Fig. 1) and has a potential for energy and CO2 storage as well as conventional and unconventional gas and minerals. While conventional hydrocarbons form the major energy resource produced in the Canning Basin, it is estimated to have the largest unconventional shale gas potential in Australia and 8 th largest shale gas potential in the world (Geoscience Australia, 2020;U.S.A Energy Information Administration, 2013, 2011Western Australia Department of Mines and Petroleum, 2021). The Kidson Sub-basin also contains the largest halite formation in Australia (Hashimoto et al., 2018), one a the most cost-effective methods for underground hydrogen storage (Lord et al., 2014). The Sub-basin also has significant mineral resource prospectivity, such as for Uranium (Botten, 1984) and sediment-hosted base metals (McCracken et al., 1997;Passmore and Towner, 1987;Ringrose, 1984;Veamcombe et al., 1995).
The Kidson Sub-basin formed in the Early Ordovician (~ 480 Ma) and has since undergone three major extensional phases, separated by three major inversion episodes (Hashimoto et al., 2018;Kennard et al., 1994a;Shaw et al., 1994). The inversion episodes are associated with extensive exhumation and have impacted fluid migration, salt dissolution, brine migration and mineralisation in the Canning Basin overall (Hashimoto et al., 2018;Yule and Daniell, 2019). Exhumation studies, therefore, have great implications on understanding the evolution of the Kidson Sub-basin, as well as its hydrocarbon and mineral potential.
Exhumation is the process of removing overburden from a basin or terrane when the rocks are vertically displaced from their maximum burial depth (Corcoran and Doré, 2005). Exhumation occurs in a wide variety of geological settings in response to epeirogeny and tectonic processes and as such can be used to study basin evolutionary processes (Gallagher, 2012) and hydrocarbon prospectivity (Corcoran and Doré, 2005;Dore ́ et al., 2002;Jensen and Schmidt, 1993). Additionally, exhumation has important significance on halite dissolution and brine migration and mineralisation of basins with salt deposits, influencing the formation and preservation, as well as spatial and temporal distribution of sedimenthosted mineral deposits (Cox et al., 2003;Kesler and Wilkinson, 2006). Thus, exhumation studies have great implication on the tectonic evolution and energy potential of a basin.
As a result of this potential, the Kidson Sub-basin has been the focus of new acquisition of seismic and well data in the area. These new data sets includes an 872 km 2D seismic line across the Kidson Sub-basin, acquired in 2018 and the Barnicarndy-1 stratigraphic well, drilled in 2019 (Geoscience Australia, 2020;Southby et al., 2019). The acquisition of these datasets has led to new understandings of the salt formations in the Kidson Sub-basin, which are the result of tectonic uplift and associated change of the depositional environment from open marine to restricted marine conditions in the Ordovician (Zhan, 2019). Extensive erosional unconformities were also observed on seismic line 18GA-KB1 and have been interpreted to be the result of exhumation following major basin inversion episodes (Southby et al., 2019). Prior to this new acquisition, there have been exhumation studies based on wells in the broader Canning Basin, such as that of Duddy et al. (2003Duddy et al. ( , 2006 and Green (2014) that studied the thermal history reconstruction of the Canning Basin. These studies found that the paleo-thermal maximum in the Canning Basin was likely attained between the Late Triassic to Early Jurassic. Exhumation has therefore strongly affected the geological evolution of the Canning Basin and by implication the Kidson Sub-basin too. These studies provide evidence on the existence of uplift and some constraints on the timing, but a detailed study of the exhumation of the Kidson Sub-basin remains to be carried out based on the new data.
In this study we integrate the newly acquired seismic data with existing wells (13 wells) to quantify the magnitude of exhumation in the Kidson Sub-basin (Fig. 1). This includes three wells located on the adjacent Munro Arch and Ryan shelf (Fig. 1). The study involved a detailed interpretation of the newly acquired seismic line (Kidson seismic survey 18GA-KB1-60km), highlighting exhumation features within the basin. We employed two methods of analysis to better constrain the basin evolution from the available data. Firstly, a thermal technique involved integration of Apatite Fission Track Analysis (AFTA) with Vitrinite Reflectance (VR) data whilst the compaction technique employed porosity data from core and well logs. These methods are discussed in more detail below. Results from both methods are independent and complementary and were used to constrain the timing, magnitude, and the distribution of exhumation during major inversion episodes in the Kidson Sub-basin. In the next section, we describe the geological setting of the Kidson Sub-basin .   1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61 Carlsen and Ghori, 2005). Insert (bottom left corner) is the map of Australia showing the approximate location of the Canning Basin (red box) (modified from Bradshaw et al., 2012). The Canning Basin located in Western Australia is divided into onshore and offshore component. The onshore Canning component developed as an intra-cratonic basin during the Early Ordovician and has undergone a prolonged period of extensional and compressional deformation which has structured the basin into several tectonic features. Wells in the Kidson Sub-basin used in this study include Kidson-1, Sahara-1, Wilson Cliffs-1, Frankenstein-1, Kemp Field-1, Nicolay-1, Patience-1, and Contention Heights-1.  Bradshaw et al., 2012). The onshore Canning Basin was initiated between two sets of cratonic blocks: the Halls Creek and King Leopold orogens to the northeast; and the Paterson Orogen and Pilbara Craton to the southwest.

Geological setting and evolution
The Canning Basin is the largest sedimentary basin in Western Australia covering an approximate area of 530,000 km 2 . The basin is divided into an onshore portion described to be an intra-cratonic system and an offshore portion which is described to be part of a passive margin system (Bradshaw et al., 2012;Carlsen and Ghori, 2005;Forman et al., 1981;Western Australia Department of Mines and Petroleum, 2021). The onshore intra-cratonic system constitutes two major northwest to southeast trending depositional centres (Fig. 1 and   1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64  65 2), which are separated from each other by basement platforms and surrounded by shelves and terraces (Fig. 1). These depocenters comprise the (i) Fitzroy Trough-Gregory Sub-basin complex located within the northern part of the basin and (ii) Willara-Kidson Sub-basin complex located within the southern portion of the basin ( Fig. 1; Hashimoto et al., 2018). The Kidson Sub-basin is the largest amongst all the depocenters and tectonic provinces in the basin and occupies the south-eastern corner of the basin (Fig. 1).
The onshore Canning Basin, which hosts the Kidson Sub-basin, is an intra-cratonic rift basin that developed in the Early Ordovician (Bradshaw et al., 2012;Carlsen and Ghori, 2005;Forman and Wales, 1981;Hashimoto et al., 2018;Shaw et al., 1994). After the basin's formation, The onshore Canning Basin underwent several major basin-wide periods of tectonic evolution involving extension, subsidence, inversion and exhumation (uplift and erosion) which together resulted in the development of the individual depocenters and tectonic features in the basin (Hashimoto et al., 2018;Shaw et al., 1994). Compared to the northern sub-basins, the southern sub-basins (Kidson and Willara) are less deformed characterised by the lack of significant fault block movements (Western Australia Department of Mines andPetroleum, 2021, 2014). The Kidson Sub-basin together with the other sub-basins within the Canning Basin are dominated by Ordovician to Permian sediments with minor or no Mesozoic and Cenozoic overburden sediments at some locations. Sediments within the Kidson Sub-basin are generally thinner with total sediment thickness of 5 km compared to the thicker sediments of more than 15 km in the northern parts of the Canning Basin (Kennard et al., 1994a). The sediments within the Kidson Sub-basin were deposited within a wide variety of depositional environments ranging from marine to nonmarine comprising marine shelf, carbonate reef, paralic, fluvial, fluvio-deltaic, aeolian and evaporitic sediments (Cadman et al., 1993;Forman et al., 1981). The evolution of the Kidson Sub-basin is linked to the overall evolution of the Canning Basin. A complete tectonic and sequence stratigraphic evolution of the Kidson Sub-basin is summarised in Fig. 3 and presented in the next section .  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64 Figure 3. Generalised litho-stratigraphy of the Kidson Sub-basin showing the evolution of the basin as well as stratigraphic relationships between formations and major unconformities [created using timescale creator with reference from Command Petroleum NL (1989); Forman and Wales (1981); Hashimoto et al., (2018); Shaw et al. (1994)]. The Kidson Subbasin has undergone three major extensional phases separated from each other by three major compressional/transpression episodes. The extensional episodes resulted in deposition of major sedimentary sequences whilst the inversional episodes resulted in exhumation. Unconformity, U1 is associated with either a period of non-deposition or minor exhumation episode during the Cenozoic. Unconformities, U2, U3 and U4 are associated with major exhumation periods that affected the Kidson Sub-basin and are the focus of this study.
Phase 1: Early Ordovicianmiddle Silurian (500 -420 Ma) Multiple extensional events affected Western, Central, Eastern and Northern Australia during the Early Ordovician associated with the breakup of microcontinents from the northeastern Gondwanan supercontinent (Johnson et al., 2017). In western Australia, these extensional activities led to the initiation of the onshore Canning Basin as an intra-cratonic rift basin between two main sets of cratonic blocks; the Halls Creek and King Leopold orogens to the northeast and the Paterson Orogen and Pilbara Craton to the southwest cratonic blocks (Fig. 2;Hashimoto et al., 2018;Hocking et al., 1994) This early extension that initiated the basin has been named the Samphire Marsh Extensional Movement (Shaw et al., 1994). During this extension and early basin development, the Kidson and Willara Sub-basins developed as relatively broader and shallower graben and half-graben depocenters (Hashimoto et al., 2018). On the other hand, the northern depocenters (Fitzroy Trough and Gregory Sub-basin) developed as narrow and deeper graben and half-graben structures. Anatomically, the graben and half graben structures of the Kidson Sub-basin have been described as relay-style accommodation zones that developed between overlapping fault blocks (Shaw et al., 1994). As compared to other parts of the basin, faulting was less prevalent in the Kidson Sub-basin, Broom platform, and Crossland platform (Hashimoto et al., 2018). Rather, these areas were dominated by intra-cratonic sag during this period (Hashimoto et al., 2018).
Extension was accompanied by Subsidence of more than 1.5 km across the major depocenters in the Canning Basin including the Kidson and Willara Sub-basins and the Fitzroy Trough (Shaw et al., 1994). Subsidence at this time was strongly influenced by basement heterogeneities and initial basin tectonics (Shaw et al., 1994). Tectonic provinces that experienced slower Subsidence such as the Kidson Sub-basin seem to strongly correlate with more stable and and older basement areas (Hashimoto et al., 2018). Associated extensionrelated subsidence led to the formation of transgressive environments and the deposition of thick sedimentary sequences over the basement during the Early Ordovician to late Silurian period ( Fig. 3; Kennard et al., 1994a;Parra-Garcia et al., 2014). The sequence is about 3 km thick over much of the Canning Basin, with thicknesses up to 5 km within the Kidson Subbasin. The lower part of this sequence comprises shallow to deep marine mixed siliciclastic and carbonate successions (mudstone, dolostone, limestone and sandstone) of the Nambeet and Carranya formations, Kudata Dolomite, and lower Emanuel Formation, Nita, and Goldwyer formations with the Goldwyer Formation marking the maximum flooding surface within the basin (Kennard et al., 1994a;Parra-Garcia et al., 2014) During the Late Ordovician to early Silurian, depositional environment changed from open marine to restricted evaporitic conditions across much of the basin (Parra-Garcia et al., 2014;Zhan, 2019). This change is strongly correlated to a combination of regression and tectonic uplift related to the early episodes of the Alice Spring Orogeny (Zhan, 2019). The restricted evaporitic environments were synchronous with arid climatic conditions and led to the deposition of thick salt sequences of the Minjoo and Mallowa salt of the Curibbudy Group in the southern Kidson and Willara sub-basins (Forman et al., 1981;Parra-Garcia et al., 2014;Zhan, 2019). Particularly, the Mallowa salt is up to 800 m thick within the central Kidson Sub-basin and is considered as the most extensive halite deposit in Australia (Hashimoto et al., 2018).

Phase 2: Late Silurian to Early Devonian (420 -400 Ma)
The late Silurian to Early Devonian period was characterised by a change from an initial extension to a compression tectonic regime which is correlated to major peak episodes of the Alice Springs Orogeny that affected much of central Australia (Shaw et al., 1994). This compressional event (termed Prices Creek Compression) resulted in extensive tilting, folding, uplifting, onlap and erosion of sedimentary units resulting in an angular unconformity on top of the Ordovician to Silurian sedimentary sequence over much of the Canning Basin ( Fig. 3; Hashimoto et al., 2018;Parra-Garcia et al., 2014;Shaw et al., 1994). This deformation is also suggested to have initiated extensive salt dissolution and brine migration within the Canning Basin, and this has important significance for mineralisation in the basin (Hashimoto et al., 2018).

Phase 3: Early Devonian to early Carboniferous (400 -345 Ma)
Extension resumed from the Late Devonian to early Carboniferous period (Fig. 3). The main rifting (extension) phase was preceded by a pre-rift sag (Tandalgoo sag) phase in the Early to Middle Devonian and this sag-related basin Subsidence period was attributed to extension in the lower crust with no major extension in the upper Crust (Shaw et al., 1994). Aeolian, fluvial, playa and marginal marine sedimentary facies make up the Millinjerie Limestone, Tandalgoo Sandstone and Dominic Shale were deposited at this time ( Fig. 3; Hashimoto et al., 2018;Kennard et al., 1994a). The main extensional event (termed Pillara Extensional Movement) started during the Late Devonian with the development of normal faults and the reactivation of older faults, especially the Beagle Bay-Pinnacle and Fenton Fault Systems and the formation of accommodation zones between fault segments (Hashimoto et al., 2018). Following this extension, and associated Subsidence, widespread transgression developed across the entire Canning Basin (Forman et al., 1981). Fluvio-deltaic complexes, hypersaline lagoonal deposits, carbonate reef complexes and mixed carbonate-siliclastic ramps were deposited made up of the Cadjebut Formation, Fairfield Formation, Anderson Formation, Pillara and Nullara sequences (Cadman et al., 1993;Kennard et al., 1994a;Parra-Garcia et al., 2014). These sequences are not observed in the Kidson Sub-basin which may be due to their subsequent erosion. Varying rates of tectonic Subsidence controlled and led to the deposition and variation in the thickness of the Devonian to early carboniferous sequences across the basin (Parra-Garcia et al., 2014). These sequences range in thickness from thin (between 20 and 300 m thick) on the Broome Platform, to very thick (between 6-15 km) on the Fitzroy Trough (Hashimoto et al., 2018).

Phase 4: Middle Carboniferous (345 -320 Ma)
The ongoing extension was disrupted by basin inversion associated with transpressional tectonics during the middle to late Carboniferous period (Shaw et al., 1994) The cause of this inversion episode is suggested to be the far-field effect of Laurasia-Gondwana collision ( Fig.  3; Hashimoto et al., 2018). The inversion event, termed the Meda Transpressional Movement, resulted in mild folding, extensive uplift and erosion, and reactivation of extensional faults producing flower and pop-up structures, which are evident in most part of the basin (Shaw et al., 1994). The erosion of part of the Devonian and carboniferous sequence resulted in a major unconformity at the base of the Lower Grant Group, which is laterally extensive across the entire basin (Forman et al., 1981).

Phase 5: Late Carboniferous to Early Triassic (320 -240 Ma)
During the late Carboniferous to Triassic period, north to northeast oriented transpressional tectonism renewed across the basin resulting from a tilted orientation of the Canning Basin in comparison to ongoing rifting along the Gondwana Margin ( Fig. 3; Hashimoto et al., 2018;Parra-Garcia et al., 2014). This event has been termed, Point Moody Extension (Shaw et al., 1994). Associated tectonic related Subsidence was widespread across the Canning Basin and the deposition of transgressive and regressive sequences included glacial, fluvio-deltaic to marine deposits of the Upper Grant Group ( Fig. 3; Cadman et al., 1993;Forman and Wales, 1981;Kennard et al., 1994a). The main rifting phase at this period was succeeded by a postrift thermal sag phase initiating a transgressive-regressive cycle and resulting in the deposition of the Noonkanbah Formation, Poole Sandstone and Liveringa Group that reach thicknesses of more than 700 m over much of the Kidson Sub-basin ( Fig. 3; Cadman et al., 1993;Shaw et al., 1994).

Phase 6: Late Triassic -Early Jurassic (240 -165 Ma)
During the Late Triassic to Early Jurassic the entire Canning Basin experienced an inversion episode associated with dextral transpressional movements that affected basement blocks at the margins of the basin, especially the Fitzroy Trough ( Fig. 3; Hashimoto et al., 2018;Shaw et al., 1994). This inversion episode, termed Fitzroy Transpressional Movement, resulted in extensive folding, reactivation of extensional faults, deformation and remobilization of salt deposits and intense uplift and erosion of Permian-Triassic strata across the entire basin (Hashimoto et al., 2018;Shaw et al., 1994). This event is considered to be a crucial tectonic event that affected the entire petroleum system of the Canning Basin including cooling of source rocks, trap formation and breaching and affecting seal integrity (Zhan and Mory, 2013). The large synclines and anticlines observed in the centre of the Fitzroy Trough and the regional unconformity at the base of the Jurassic sequence are attributed to this inversion episode (Shaw et al., 1994). This compressional deformation was accompanied by the emplacement of isolated intrusive bodies in the Fitzroy Trough and Lennard Shelf (Hashimoto et al., 2018;Reeckmann and Mebberson, 1984).

Phase 7 and Phase 8: Middle Jurassic -Cenozoic
During the Middle Jurassic, northwest to southeast oriented extension that led to the final Gondwana breakup was initiated in the Argo Abyssal Plain, in the adjacent northern Carnarvon Basin (Shaw et al., 1994). Associated Subsidence related to this extension resulted in the establishment of aeolian, fluvial and delta plain environmental conditions into the onshore Canning Basin and the deposition of conglomerate, coal, mudstone and sandstone over the offshore Canning basin (Cadman et al., 1993;Forman and Wales, 1981;Parra-Garcia et al., 2014). Similar sedimentary sequences were deposited onto the onshore Canning Basin during the Early Cretaceous period following the breakup of Greater India from Australia and the development of the north-western Australian passive margin (Betts et al., 2002;Hashimoto et al., 2018;Kennard et al., 1994a). The present-day onshore Canning Basin has been terrestrial since the middle Cretaceous time except for the occasional flooding of marine waters along the present-day coast (Johnson et al., 2017).
During the Oligocene to Miocene time, the northern margin of the Australian plate collided with southeast Asian microplates resulting in extensive deformation involving reactivation of Paleozoic to Mesozoic faults and basin inversion across the North West Shelf (Keep et al., 2007). This appears not to have affected the adjoining onshore Canning Basin significantly (Hashimoto et al., 2018;Keep et al., 2007), however, mild basin inversional tectonics including uplift and erosion across the onshore Canning Basin are attributed to this Cenozoic event (Shaw et al., 1994).

Data sets
This study integrates seismic reflection data and well data obtained for the Kidson Sub-basin. The location of seismic and well data used for this study is shown in Fig. 1. Additionally, thermal history analysis (using AFTA data) and burial history modelling obtained from other independent studies (Duddy et al., 2006(Duddy et al., , 2003Ghori, 2013;Green, 2014) have been integrated with this study. The seismic data (Survey 18GA-KB1-60km) is a relatively new data acquired by Geoscience Australia in 2018. It is a Pre-stack Depth Migrated 2D seismic line with a sampling rate of 2 ms and 150-fold. The seismic line covers a total length of 872 km and images major tectonic units within the Canning Basin including the Wallal Embayment, Barnicandy Graben, Anketell Shelf, Kidson Sub-basin and Ryan Shelf (Fig. 1). The Kidson Sub-basin is the main Sub-division imaged by the seismic survey.
Well data used in this study includes well-logs (interval transit time from sonic log, density, gamma ray), core porosity, litho-stratigraphic data, vitrinite reflectance data, well completion reports, and surface and bottom hole temperature measurements. These are open file data obtained from the Western Australia Petroleum and Geothermal Information Management System (WAPIMS). Stratigraphic information and well log data are shown in Fig. 4 reflectance data and present-day temperature measurements are shown in Table 1 and Table 2 respectively. The number of sample runs (N) used to determine the maximum mean VR for each sample was obtained for only two wells. For Kidson-1, N ranged from 9 to 28; For Contention Heights-1, N ranged from 9 to 11. Where VR data were not available, especially withing pre-Silurian sediments, Graptolite Reflectance data were converted to equivalent VR using Eqn. 1 after Luo et al. (2020) = ( * 0.515) + 0.506 (1) The compressional sonic velocity (interval transit time, Δt) was used as a proxy for porosity because interval transit times are directly related to porosity which is a direct effect of compaction (Hillis, 1995;Tassone et al., 2014). This is because, contrary to density logs that measure bulk porosity of a sedimentary unit, sonic waves do not generally pass through void spaces and open fractures and the associated interval transit time therefore measures the primary porosity of the sedimentary unit (Tassone et al., 2014). Sonic velocities from shale lithologies are widely used since shales exhibit the most simple velocity-depth trend (Hillis, 1995;Licciardi et al., 2020;Magara, 1980;Tassone et al., 2014). Sandstone lithologies also show a consistent porosity-depth relationship and have been employed extensively in basin analysis (Allen and Allen, 2013;Corcoran and Doré, 2005). Thus, in this study, we employ compressional sonic velocity data obtained from both sandstone and shale lithologies, and core porosity data obtained from sandstone lithologies to estimate the magnitude of exhumation across the Kidson Sub-basin. Within sandstone intervals, core porosity data provided additional constraint to log porosity data. Particularly for the Kidson Sub-basin, one advantage of using log porosity from sandstone intervals is that most shale intervals are mixed lithologies, making it difficult to isolate clean shale zones for analysis. However, clean sandstone intervals were readily available from the log data ( Fig. 4). . Well log and stratigraphic data used for this study. Stratigraphic information from well data is used to identify position and timing of unconformities at each well location Gamma ray and density logs were combined with core description and other stratigraphic data from well completion reports to delineate sandstone and shale lithologies for analysis. Sandstone units used for analysis were obtained from the Poole Formation (to constrain exhumation at unconformity U2), Tandalgoo Formation (to constrain exhumation at unconformity U3) and Carribuddy Group (to constrain exhumation at unconformity U3). U1, U2, and U3 correspond to erosional unconformities (exhumation) associated with the Fitzroy Transpression, Meda Transpression and Prices Creek Compression, respectively.   Duddy et al. (2003) and Duddy and Erout (2001). For measured BHT < 66 0 C, correction was made by increasing the measured BHT by 20% of the difference between the BHT and surface temperature, and for measured BHT, correction was made by increasing the measured BHT by 25% of the difference between the BHT and surface temperature.

Methodology
As the first step, seismic interpretation was conducted to identify and establish features associated with exhumation in the Kidson Sub-basin. Seismic interpretation was followed with estimating the amount of exhumation at the individual well location. The amount of exhumation in sedimentary basins are estimated using one of four main techniques: tectonic, thermal, compaction and stratigraphic (Corcoran and Doré, 2005). In this study, the thermal and compaction techniques were both employed to estimate the magnitude of exhumation in the Kidson Sub-basin. Combining these two methods offers the advantage of providing independent results that can be used to constrain exhumation magnitudes in basins (Johnson et al., 2017;Makuluni et al., 2021). The methods are described in detail in the following sections.

Seismic Interpretation
Seismic interpretation involved a detailed interpretation of line 18GA-KB1-60km (pre-stack depth migrated) across the Kidson Sub-basin (see Fig. 1  neutron logs from boreholes were used to generate synthetic seismograms, which were used to tie the well (borehole) to seismic data. Several horizons, corresponding to formation tops in the borehole were then selected and mapped across the seismic line. In this work, the main horizons that were selected and mapped corresponds to formation tops as well as erosional unconformities associated with exhumation. Structural features such as faults and folds were also identified and mapped out. Seismic interpretation was conducted mainly to identify lithological, chronostratigraphic, and seismic stratigraphy as well as the location, extent, and approximate timing of erosional unconformities associated with exhumation within the Kidson Sub-basin. The amount of exhumation at the various unconformities was estimated.

Thermal-based technique for estimating the amount of exhumation
Thermal indicators including Vitrinite Reflectance (VR) and Apatite Fission Track Analysis (AFTA) are irreversible temperature indicators that provide information on the maximum temperature a rock unit has attained in the geologic past (paleo-thermal maximum) before the start of a cooling episode that is usually caused by exhumation (Allen and Allen, 2013;Bray et al., 1992;Gallagher, 2012;Green et al., 2002). VR is a common analysis so is therefore widely available and is a decent maturity indicator. In the case of AFTA, an estimate of the timing of maximum paleo-temperatures and timing of exhumation (cooling from maximum paleotemperatures) may be obtained additionally (Duddy et al., 2003;Green et al., 2002). VR may also record higher paleo-temperatures (from relatively deeper depths) that may exceed the partial annealing zone of AFTA (Bray et al., 1992;Green et al., 2002). Thus, a major advantage of integrating VR and AFTA data is that, both can be used to constrain the amount and timing of exhumation independent of stratigraphic indication (Corcoran and Doré, 2005). The general principle for the use of VR or AFTA data (or any thermal-based method) for exhumation analysis is that rocks are heated when buried but cool when exhumed (Bray et al., 1992). During maximum burial (heating), the vitrinite or apatite particles undergo thermal heating which alters the nature of these particles within the rock. This is an irreversible process, so these maximum temperatures are 'locked in' by the vitrinite or apatite grains even after an exhumation period (Fig 5a). Thus, the measured vitrinite reflectance or apatite fission tracks is an indicator of maximum temperature experienced by the rock. These maximum temperature measurements extracted from VR or AFTA data may be converted to equivalent depth using appropriate techniques and compared to present-day depth of the sample to estimate the amount of exhumation (Corcoran and Clayton, 1999). Alternatively, a graph of depth versus VR plotted on a log scale (Dow, 1977) or depth versus temperature (Bray et al., 1992) may be used to estimate the amount of exhumation.
In this study, we employ the graphical approach initially proposed by Bray et al. (1992) to estimate the magnitude of exhumation in the basin. As a method, it is generally accepted as one of the most accurate methods for estimating exhumation using paleo thermal indicators and resolves some of the pitfalls of semi-log plots and empirical depth conversions (Corcoran and Doré, 2005). The technique has been used to quantify exhumation in several basins including the Brooks Range, Alaska (O'sullivan et al., 1995), Northern Australia basins (Duddy et al., 2003), Sichuan Basin, China (Zhu et al., 2019) and Bonaparte Basin, North West Shelf, Australia (Makuluni et al., 2021). The general procedure involved in using this method to estimate the magnitude of exhumation has been described below. In our study, only VR data was used to estimate the magnitude of exhumation, while VR data was integrated with AFTA from other independent studies to constrain the timing of thermal activities in the basin.
The method involves an initial conversion of VR values to equivalent temperature estimates. The Sweeney and Burnham (1990) kinetic model represents one of the most accurate and widely accepted VR to temperature translation models (Corcoran and Doré, 2005). We used this model was used to convert VR values to equivalent maximum temperature values using an associated equation obtained from Yamamoto et al. (2005) (Table 1; Eqn. 2). As a basis for comparison, an empirical model (Barker and Pawlewicz, 1994) was used to convert VR to equivalent temperature values (Eqn. 3).
Estimated maximum paleo-temperature values extracted from VR data are presented in Table 1. These maximum temperature values were plotted against equivalent depth for individual wells. From these plots, maximum or paleo-temperature profiles for individual wells were established by fitting a linear relationship (line of best fit) between maximum paleo-temperatures and depth (example shown in Fig 5). Paleo-geothermal gradients were estimated from the paleo-temperature profiles at each well location (Fig. 5). Moreover, present-day temperature values obtained from drill-stem tests (DST) and corrected bottomhole temperature (BHT) were plotted against depth to establish present-day temperature profiles and gradients for the individual wells (example shown in Fig 5). By extrapolating the maximum temperature profile to the paleo-surface (unconformity) and comparing it with the present-day temperature profile, the amount of exhumation at the unconformity can be estimated at each well location (Fig. 5;Bray et al., 1992). The estimated amount of exhumation is obtained by dividing the amount of cooling (temperature difference between the paleo-temperature and present-day temperature intercepts at the unconformity) by the paleo-geothermal gradient (Fig. 5;Bray et al., 1992;Corcoran and Doré, 2005;Green et al., 2002).
The method has some limitations including the following: vitrinite macerals are typically obtained from lithologies with high organic matter with very limited use for other lithologies (Corcoran and Clayton, 2001). Thus, the number of VR measurements down-well may may not be enough to develop a good profile for calibration or for modelling purposes. Additionally, the method assumes that the paleo-geothermal signatures from the thermal indicators (VR) are due to conductive heat flow resulting from depth of burial (Bray et al., 1992). Thus, results may be misleading in areas where stratigraphic units were affected by external heat sources such as magmatic bodies, hot fluids or areas that have experienced large increase in basal heat flow (Corcoran and Doré, 2005). However, comparison of the present- day and paleo-temperature profiles can be used to identify such effects (Bray et al., 1992;O'sullivan et al., 1995). As an additional constraint to the VR method, we have also considered the compaction-based technique, discussed in the next section.  (2005) and Bray et al. (1992)]. (a) Maximum temperatures are trapped in the vitrinite particles during maximum burial. (b) VR preserves these maximum temperatures even after a cooling event caused by exhumation. By comparing the paleo-temperature profile with the current (or present-day) temperature profile, the amount of exhumation can be estimated. E represents the amount of exhumation, Tp represents the temperature where the paleotemperature profile intercepts the unconformity, Tc represents the temperature where the current temperature profile intercepts the unconformity and (dT/dZ)p represents the paleogeothermal gradient estimated from the paleo-temperature profile.

Compaction-based technique for estimating the amount of exhumation.
The compaction-based method employs the porosity-depth reference to estimate the magnitude of exhumation at well locations. The advantages and limitations regarding the use of compaction-based techniques for estimating exhumation has been discussed in detail by Corcoran and Doré, (2005). This method uses sonic transit-time data (used as a proxy for porosity) that are widely available and are routinely acquired during formation evaluation, which is one of its biggest advantages (Hillis, 1995;Tassone et al., 2014). Thus, the method provides greater spatial resolution compared to limited data from paleo-thermal indicators (such as VR and AFTA) (Johnson et al., 2017). Furthermore, wireline logs including sonic logs are in situ measurements and are not affected by errors such as sample collection, preparation and processing (Tassone et al., 2014). Moreover, mechanical compaction is less susceptible to changes by transient heating, which is a major weakness associated with thermal-based techniques (Corcoran and Doré, 2005). However, the compaction-based technique cannot be used to independently constrain the timing of exhumation and this serve as the main limitation of the method (Tassone et al., 2014). Thus, in this study, we integrates compaction-based method with stratigraphic data to constrain the timing of exhumation. A detailed description of the method is presented below.
The compaction technique is based on (Athy, 1930) law which is govern by the fundamental principle that porosity reduces with increasing depth through burial and loading (mechanical compaction), and that this mechanism is largely irreversible (Licciardi et al., 2020;Magara, 1980). Diagenetic effects such as cementation and dissolution may also produce irreversible effects on the porosity of a sedimentary unit unrelated to burial (Allen and Allen, 2013). However, Tassone et al. (2014) argued that for normal basins that have not been affected by excessive convective or advective heating, these temperature-dependent diagenetic processes are mostly associated with depth of burial. These diagenetic processes are considered to be minimal for clastic sediments with burial depth ranging from 2 to 3 km (80 0 C isotherm) (Corcoran and Doré, 2005). Also, Makuluni et al. (2021) argued that diagenetic effects including porosity enhancement through dissolution and porosity reduction through cementation generally counteracts and cancel out, leaving mechanical compaction as the main mechanism driving porosity reduction. Thus, the porosity of a sedimentary unit reflects the overall mechanical and thermochemical state of the unit and is a reflection of its maximum depth of burial (Tassone et al., 2014). Thus, the porosity of the sediments during maximum burial is retained during and even after exhumation (Licciardi et al., 2020). Although pore-elastic rebound (increase in porosity) resulting from unloading effects are recognised, these effects are considered to be negligible in comparison with loading effects (Tassone et al., 2014). As a result, most sedimentary units are compacted under equilibrium conditions (i.e. compaction under normal hydrostatic pressure) with no or negligible effects from overpressure or under-pressure (Allen and Allen, 2013;Magara, 1980). A basin's compaction pattern can therefore be represented by a single porosity-depth relationship (Licciardi et al., 2020). After an exhumation event in the geologic past, sedimentary units underlying the associated unconformity will show a present-day porosity, which is lower than expected for present-day burial depth (Hillis, 1995;Licciardi et al., 2020). By establishing a reference porosity-depth curve (which describes the normal compaction within the basin) and comparing that curve with the present-day porosity (obtained from core or well log), the difference in depth axis represents the potential exhumation that occurred between the time of maximum burial and the present-day at the well location (Corcoran and Doré, 2005;Hillis, 1995;Johnson et al., 2017;Licciardi et al., 2020). The approach has been used to quantify the amount of exhumation in several basins across the world including the Otway Basin, Australia (Tassone et al., 2014), Southern North Sea basins, UK (Corcoran and Doré, 2005;   1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64  65 Hillis, 1995), Barents Sea, Norway (Licciardi et al., 2020), Broom Platform, Canning Basin, Australia (Johnson et al., 2017) and Bonaparte Basin, North West Shelf, Australia (Makuluni et al., 2021). We focused our study on normally pressured clastic sedimentary units and looked out for signs of extreme cementation that may potentially serve as sources of errors. Interval sonic transit time data and core porosity are used to infer compaction (see section 3.1 for discussion) and have been used to estimate the amount of exhumation. The procedure is described below.
Gamma ray and density logs were combined with litho-stratigraphic descriptions from well completion reports to delineate interesting and laterally consistent sandstone and shale units. The gamma ray cut off for shale intervals was 130 API, and the upper limit for sandstone intervals was 30 API. In the case of sandstones, corrected sonic interval transit time data within selected sandstone units were converted to porosity using the well-known Wyllie et al. (1956) time average equation (Eqn. 4). This is one of the commonly used technique in the Petroleum Industry for converting interval transit time to porosity in sandstone lithologies (Crain, 2002).
where, ϕ = porosity, Δtlog = logged compressional sonic interval transit time, Δtma = standard sonic transit time for matrix material (55 սs/ft for sandstone), Δtf = standard sonic transit time for pore fluid. Well completion report indicate formation water in the selected sandstone units. Thus, a standard value of 189 սs/ft was used. These standard parameters were obtained from Crain (2002).
Filtered interval transit time (compressional sonic velocity data) from the selected sandstone and shale units and their equivalent depths were plotted and compared with the reference porosity-depth curve. In the case of the sandstone, both the measured core porosity and log porosity data from the units were plotted on the reference curve. The reference curve is a standard porosity versus depth curve or transit time versus depth curve that describes porosity reduction with depth (Athy, 1930) representing sedimentary units at their maximum burial depth (Hillis, 1995;Tassone et al., 2014). The vertical displacement of the data from this reference curve is represented as the estimated amount of exhumation (Licciardi et al., 2020). Reference curves are normally obtained from well locations in the basin where sedimentary units are presently at their maximum burial depth (Dentith, 2012;Hillis, 1995). That is, areas within the basin that have not experienced exhumation. However, considering that the entire Kidson Sub-basin has experienced multiple significant exhumation periods (Shaw et al., 1994), obtaining a reference curve for the basin will lead to inaccurate results by significantly underestimating the amount of exhumation (Hillis, 1995). Thus, reference curves for the shale (transit time data) and sandstone (porosity data) were obtained using other alternative published methods. For the shale compaction technique, we followed the approach employed by Johnson et al. (2017). The reference curve was obtained from a standard shale compaction curve that describes normal velocity-depth relationship for shales (Fig. 6a). For the sandstone compaction technique, we followed the approach presented in Corcoran and Doré (2005) and (Makuluni et al., 2021). Thus, the reference curve was constructed following Athy's (1930) porosity-depth trend (Eq. 5; Fig 6b). Standard lithological parameters for sandstone were obtained from Allen and Allen (2013) and Sclater and Christie (1980). The equation defining the reference curve is given as Where, ϕ represents measured porosity, surface porosity, ϕ0 = 0.56, compaction coefficient, c = 0.39 (km -1 ) and y represents depth.  After obtaining the reference curve, porosity or sonic interval transit time from stratigraphic units immediately below the specified unconformity that meet the necessary requirements (stratigraphically equivalent, thick and laterally extensive) were used to constrain the amount of exhumation. These requirements are to ensure that similar lithotypes are used across the individual well locations and to avoid facies related transit-time or porosity variations (Dentith, 2012;Hillis, 1995). For the youngest unconformity, estimates represent the net magnitude of exhumation since those stratigraphic units have only experienced a single exhumation episode (Johnson et al., 2017). The deeper (older) stratigraphic units have been subjected to successive exhumation events, therefore estimates from these units represent the cumulative (total) sum from the time of deposition until the present. To obtain the net magnitude of exhumation at these unconformities, the estimated amount of exhumation at younger unconformities are deducted from the cumulative estimates. The selected sandstone and shale units were tied to chrono-and litho-stratigraphic data as well as the geological history of the basin to constrain the approximate timing of exhumation. The selected units provide information on the exhumation that occurred immediately after their deposition. Thus, the Poole, Tandalgoo and middle Carribuddy sandstones and shale units have been carefully selected to constrain the amount of exhumation during the Early Jurassic, middle Carboniferous, and Early Devonian exhumation episodes, respectively (Figure 3 and 6).

Interpretation of Seismic line 18GA-KB1-60km.
Seismic line 18GA-KB1-60km covers the tectonic units of the Canning Basin and include the Pilbara Craton, Wallal Embayment, Barnicarndy Graben, Ankatell Shelf, Kidson Sub-basin and Ryan shelf (Fig. 7). For the purposes of this study, interpretation has been focused on the Kidson Sub-Basin. According to the seismic line, the Kidson Sub-basin is about 400 km wide and 6.3 km deep at the location of the seismic line, and contains well preserved sediments seen as reflectors in the seismic section (Fig. 7). Sediments were deposited in a depocenter created between two basement highs (Ankatell and Ryan shelves) during the early extensional phase of the basin in the Early Ordovician (Fig. 7). These basement highs are shown by the chaotic seismic reflections pattern at the edges of the Kidson Sub-basin. The reflectors are continuous and traceable across the entire basin, implying that major geological events, including deposition and erosion, occurred there continuously (Fig. 7). In general, most reflectors show conformable relationships across the basin indicating continuous deposition episodes (Fig. 7). Few reflectors show unconformable relationships, which extend across the entire basin indicating a break in deposition (unconformity) and are discussed in the following section. Extensional structures shown as normal faults are observed within the deeper parts of the Sub-basin which demonstrate early rifting episodes that developed and shaped the basin during the early Paleozoic period ( Fig. 7; Southby et al., 2019). Compressional and inverted structures, including faulting and upright folds, are observed within the entire stratigraphic package, from Silurian to Mesozoic sediments, at the eastern and western edges of the Kidson Sub-basin (Fig. 7a). We interpret these to be the result of major compressional and transpressional episodes that affected the basin during the Paleozoic and Mesozoic periods and resulted in extensive uplift, erosion, tilting and folding of sedimentary units (Hashimoto et al., 2018;Shaw et al., 1994). Litho-stratigraphic control from wells in the basin indicate that the Ordovician to Devonian sequence is dominated by mixed clastics, carbonates and evaporite sequences (example, Goldwyer Formation, Carribuddy Group) unconformably overlain by clastic dominated carboniferous to Mesozoic sequences (example Grant Group, Poole Sandstone) (Fig. 7b).

Unconformities in the Kidson Sub-basin
Seismic data and stratigraphic information from well data, such as well completion reports have been integrated with the overall evolution of the basin to give a detailed analysis of the  Fig. 3. In general, we identified four major unconformities and are labelled from U1 to U4 (Fig. 3). We identified and interpreted unconformities U1, U2 and U3 on seismic line 18GA-KB1-60km. They are observed to extend across the entire Kidson Sub-basin (Fig. 7). On seismic profiles, these obvious strata-discordant relation at these boundaries indicate an angular unconformity where older units are truncated by erosion and then superimposed by younger units (Fig. 7). In relation to the geological history of the basin, we interpret these angular unconformities as erosional surfaces following major periods of inversion that resulted in extensive uplift and erosion across the basin (Figs. 3 and 7). We interpreted unconformity U1, as a period of nondeposition or minor erosion associated with the collision of Australian and Indian Sub-plates during the Tertiary era (Eocene ca. 40-45 Ma) ( Fig. 3 and 5; Keep et al., 2007). Although a break-up unconformity has been suggested during the middle Cretaceous era (Fig 3; Hashimoto et al., 2018), it appears to have no strong correlation with major exhumation in the Canning Basin. We associate unconformity U2 with the Fitzroy Transpressional movement, which resulted in extensive exhumation in the Canning Basin during the Late Triassic (230 Ma) to Middle Jurassic periods (180 Ma) ( Fig. 3 and 7). We associate unconformity U3, with transpressional tectonics, the Meda Transpressional Movement, which resulted in extensive exhumation in the basin during the middle to late Carboniferous time (from 330 to 200 Ma) ( Fig. 3 and 7). The unconformity U4 has not been observed on seismic profiles, but note that it has been reported in well completion reports and documented as part of the evolution of the basin (Fig 3; Hashimoto et al., 2018). We associated unconformity U4 with the compressional deformation, Prices Creek Compressional Movement, that led to exhumation during the Middle Silurian to Early Devonian (from 420 to 400 Ma) ( Fig. 3 ; Parra-Garcia et al., 2014; Shaw et al., 1994). We were not able to constrain the magnitude of exhumation at unconformity U1 because well stratigraphic data indicated that the post Jurassic sediments have been removed at the various well locations leaving the Early Jurassic unconformity, U2 at or close to the surface. Moreover, the Cenozoic inversion that resulted in U1 is suggested not to have had significant effects on the onshore Canning Basin (Shaw et al., 1994). Since unconformities U2, U3 and U4 are the results of major exhumation events in the basin, they are the focus of this study. Thus, the amount of exhumation at these unconformities have been estimated and results are presented in the next section.

Constraining Vitrinite Reflectance (VR) data with AFTA
In this study, VR has been integrated with thermal history analysis using (AFTA) and burial history modelling obtained from other independent studies to provide important timing constrains on exhumation estimates. It must be noted that, this study did not involve AFTA and burial history modelling. AFTA results were obtained from Duddy et al. (2006Duddy et al. ( , 2003  and Green (2014) and results for burial history modelling were obtained from Ghori (2013). Results from thermal history modelling (using AFTA) indicate the approximate timing of maximum post-depositional paleo-temperatures and cooling from these temperatures at various well locations within the Canning Basin. It must be noted that results from thermal history modelling were available for only two wells in the Kidson Sub-basin, that is, Kidson-1 and Nicolay-1. However, results from wells located outside the Kidson Sub-basin were also integrated to identify whether thermal events were regional or local. Results are summarised below: Kidson-1 (used in this study), 205 to 160 Ma; Nicolay-1 (used in this study), 175 to 75 Ma; Acacia-1 and 2, 230 to 170 Ma; Yulleroo-1, 230 to 210 Ma; White Hills-1, 230 to 180 Ma; McLarty-1 -155 to 90 Ma. (Duddy et al., 2006(Duddy et al., , 2003Green, 2014). The consistency in results from several wells, including wells in the Kidson Sub-basin, indicate that the heating event was extensive across the entire Canning Basin (Duddy et al., 2003). Furthermore, results from burial history analysis indicate that maximum burial (which corresponds to maximum heating) of sedimentary units in the Kidson-1 well occurred between 230 to 180 Ma (Ghori, 2013).
Since the Kidson Sub-basin has experienced multiple exhumation episodes, timing constraints from these thermal and burial history analyses in the Canning Basin (and Kidson Sub-basin) put an important constraint on the temperature information and the associated paleo-temperature profile estimated from VR data. These constraints from AFTA and burial history modelling imply that maximum post depositional heating (temperatures) and subsequent cooling from maximum temperatures occurred in the Late Triassic to Early Cretaceous (from 230 to 170 Ma). Moreover, these constraints strongly suggest that the Late Triassic heating event associated with burial was the highest in the basin and overprinted earlier heating episodes leading to 'resetting' of the VR 'clock' in all the stratigraphic units below. This was followed by an exhumation event during the Early Jurassic that led to cooling of rocks from their maximum temperatures. Considering these time constraints, we imply that, the maximum temperature information obtained from vitrinite reflectance data represent a single and uniform heating episode during the Late Triassic, and that this temperature information is only appropriate for estimating the amount of exhumation during the succeeding cooling event. Results from AFTA analysis and burial history analysis support the well-documented and well-established timing of the Fitzroy Transpression, which occurred from the Late Triassic to Early Jurassic (from 230 to 170 Ma) (Figure 3; Cadman et al., 1993;Forman and Wales, 1981;Hashimoto et al., 2018;Parra-Garcia et al., 2014;Shaw et al., 1994;Zhan and Mory, 2013). We therefore associated this erosional event with the obvious regional Mesozoic erosional unconformity, U2, observed on seismic profiles that extends across the entire Kidson Sub-basin (Fig 7) and which has been reported in other parts of the Canning Basin (Hashimoto et al., 2018). Thus, VR data in the Kidson Sub-basin is only appropriate for estimating the magnitude of exhumation during the Early Jurassic exhumation period (Fitzroy Transpression), represented as unconformity U2 in this study (Fig.7). VR has been used to estimate the magnitude of exhumation at U2 and results are presented below.  Figure 8. Magnitude of estimated exhumation using VR data for wells in the Kidson Subbasin during the Late Triassic to Early Jurassic, Fitzroy Transpression (U2) Estimates have been made at unconformity U2 only using constraints from AFTA data (see section 4.3 for discussion). Numbers written in blue represent current or present-day geothermal gradient and numbers written in red represent paleo-geothermal gradient.

Magnitude and uncertainties in exhumation estimates from VR data
The magnitude of exhumation during the Late Triassic to Early Jurassic inversion episode has been estimated using VR and results are summarised in Table 3 and displayed in Fig. 8. Results indicate that the magnitude of exhumation ranged from 800 to 2400 m and increased from south east to northwest across the Kidson Sub-basin (Fig 12A2). Uncertainty analysis associated with the estimated magnitude of exhumation is discussed in the next section.
General uncertainties regarding the use of VR for exhumation estimates have been described in detail by Corcoran and Doré (2005). For this study, caved-in, suppressed and reworked VR, as well as VR data affected by external localised heat bodies, where identified were not used for analysis. However, there may be uncertainties associated with the quality of VR data associated with the number of sample runs (N) used to obtain each VR data point. Although, 'N' at most well locations is not known, 'N' obtained for Kidson-1 and Contention Heights-1 is small for some samples and may have uncertainty on the quality of VR data and associated exhumation estimate. In this study, we associate major uncertainty in exhumation estimates to the limited VR data points in the selected wells used to constrain paleo-geothermal profile at the individual well locations. Although this effect is observed in all the wells, it is most pronounced in Nicolay-1, Sahara-1 and Contention Heights-1, which have the least VR data points. Additional paleo-thermal data such as VR, AFTA, CAI, Tmax, etc. obtained from several stratigraphic intervals will provide enough data points to constrain the paleo-thermal profile and associated paleo-geothermal gradient at each well location. However, in the absence of such data, we have employed a range of possible paleo-geothermal gradients to analyse uncertainties in exhumation estimates. It must be noted that these range of paleogeothermal gradients are only based on convenience and to predict how exhumation estimates changes with variations in the estimated paleo-geothermal gradient. In general, a 5 0 C/km decrease in the estimated paleo-geothermal gradient, will result in about 300 to 500 m increase in the estimated magnitude of exhumation and a 5 0 C/km increase in the estimated paleo-geothermal gradient, will result in about 300 to 400 m reduction in the estimated amount of exhumation. A detailed uncertainty results is presented in Table 3.

Magnitude of exhumation from compaction method
The magnitude of exhumation using shale and sandstone compaction techniques are presented in Fig. 9 and 10, as well as in Table 4 and 5. Results from both methods are consistent and indicate that the Kidson Sub-basin has experienced a cumulative amount of exhumation up to 2400 m, 1850 m and 1200 m since the middle Silurian to Early Devonian, middle Carboniferous and Early Jurassic period, respectively (Fig. 9, 10, 11; Table 4). To determine the net exhumation during the middle Silurian to Early Devonian period, the cumulative exhumation since the middle Carboniferous period was deducted from the cumulative exhumation since the Early Devonian period. Similarly, the cumulative amount of exhumation since the Early Jurassic was deducted from the cumulative amount of exhumation since middle Carboniferous to obtain the net amount of exhumation during the middle Carboniferous. The Early Jurassic exhumation represents the last major exhumation in the Kidson Sub-basin. As a result, estimates represent the net amount of exhumation during the Early Jurassic time. Results are presented in Table 5 and Fig 11. Results indicate that about 350 to 500 m of exhumation occurred during the middle Silurian to Early Devonian inversion episode (Fig. 12C). We associate this exhumation to the Prices Creek Compression which resulted in unconformity U4 (Fig. 3). During this episode, the magnitude of exhumation increased from south-east to north-west across the Kidson Sub-basin (Fig. 12C).

Temperature profiles and geothermal gradients in the Kidson Sub-basin.
Comparison of the paleo-temperature profile with the present-day temperature profile at the various well locations indicate that sediments were hotter in the past. This is shown by the offset of the paleo-temperature profiles to higher temperatures (Fig. 8). Temperatures during the paleo-thermal maximum in the Late Triassic were significantly higher than the present day. Temperatures have decreased by 40 to 80 0 C from the Late Triassic to the present-day across the Kidson Sub-basin (Fig. 8). At all the well locations, except Sahara-1, the paleotemperature profiles are sub-parallel to the present-day temperature profiles and geothermal gradients range between 28 to 37 0 C/km (Fig. 8). At these well locations, the paleogeothermal gradients are 0.4 to 5.7 0 C/km higher than the present-day geothermal gradient. On the contrary, the present-day and paleo temperature gradients at Sahara-1 are 44 0 C/km and 64 0 C/km, respectively. These are extremely high compared to other well locations. Moreover, the relationship between the present-day and paleo-temperature profiles suggest significant influence of increase in basal heat flow (Bray et al., 1992;O'sullivan et al., 1995). However, the effects of basal heat flow are regional and affect larger areas (Allen and Allen, 2013). Thus, considering the proximity of Sahara-1 with other well locations, such large difference between present-day and paleo-temperature gradients, corresponding to large variation in basal heat flow would have been observed at other adjacent well locations. Moreover, typical present-day geothermal gradients reported in the Canning Basin are less than 43 0 C/km (Horstman, 1984). These high geo-thermal gradients are only observed at one well location and suggest that the temperature data (BHT and VR) from Sahara-1 may have been significantly influenced by localised heating bodies, such as intrusive fluids, or the BHT and VR data may not be accurate. As a result, we do not consider the temperature data from Sahara-1 in the general temperature analysis of the Kidson Sub-basin.
The sub-parallel relationship between the present-day and paleo-temperature profiles, and associated small variation between the present-day and paleo-geothermal gradients observed at all the other well locations (Fig. 8) indicate that heating to maximum temperatures was predominantly due to deep burial (during the Late Triassic subsidence) with little contribution from increase in basal heat flow (Bray et al., 1992;O'Sullivan et al., 1995). Also, the sub-parallel present-day and paleo-temperature profiles (Fig. 8) demonstrate that cooling to present-day temperatures was predominantly due to exhumation (Bray et al., 1992;Green et al., 2002;O'Sullivan, 1999). Similar temperature profiles have been reported for White Hills-1 located within the Gregory Sub-basin (northeast Canning Basin), about 200 km from the Kidson Sub-basin (Duddy et al., 2003). Thus, our results agree with the work of  (Allen and Allen, 2013;McKenzie, 1978;Waples, 2001). Heat flow may vary little or significantly long after the extensional event. As described above, the nearly parallel present-day and paleotemperatures profiles and associated gradients indicate little variation in heat flow from the Late Triassic thermal maximum until the present-day.
Geothermal gradients within the Kidson Sub-basin are consistent with results from other parts of the Canning Basin (Lennard Shelf and Fitzroy Trough) (Arne et al., 1989;Horstman, 1984). Geothermal gradients within a basin, whether in the present or in the past provide information about the tectonic setting of the basin (Allen and Allen, 2013). This is because geothermal gradients are related to heat flow which are diagnostic of the tectonic setting of a basin (Allen and Allen, 2013). Based on geothermal gradient, sedimentary basins have been classified into three broad categories including 'normal', hypothermal and hyperthermal basins (Allen and Allen, 2013;Robert, 1988). In general, present-day and paleo geothermal gradients in the Kidson Sub-basin range from 28 to 37 0 C/km and are considered to fall within the 'normal' to hyperthermal group of basins (Allen and Allen, 2013). Normal and hyperthermal basins predominantly comprise of regions of lithospheric extension such as oceanic and continental rift systems, strike slip and back arc basins, old passive margins, etc. (Allen and Allen, 2013) where heat flow is elevated. The range of present-day and palegeothermal gradients within the Kidson Sub-basins is consistent with the general classification of the basin as an intra-cratonic rift basin (Forman and Wales, 1981;Hashimoto et al., 2018;Hocking et al., 1994;Shaw et al., 1994).

Exhumation estimates from thermal and compaction methods.
The estimated magnitude of exhumation during the Late Triassic to Early Jurassic from both the thermal and compaction method have been compared (Table 5). The two techniques gave contrasting results. Results from the compaction method indicate that the amount of exhumation increased from east to west across the Kidson Sub-basin (Fig. 12A1). On the other hand, results from the thermal technique indicate that the magnitude of exhumation generally increased from west to east across the Kidson Sub-basin (Fig. 12A2). Also, results indicate that the thermal method yielded higher exhumation estimates at all the well locations, except for Sahara-1. Large uncertainties associated with temperature profiles and gradients associated with Sahara-1 have been discussed above. At all the other well locations, where the thermal method yielded higher exhumation estimates, differences in the estimated magnitude of exhumation between the two methods range from as low as 100 m to as high as 1700 m (Table 5). Reasons accounting for the contrasting pattern of exhumation distribution between both methods and comparatively higher exhumation estimates associated with the thermal method are discussed below. Here, we disregard potential uncertainties and errors that may be associated with data acquisition and sampling as well as errors that may be associated with analytical, processing and systematic techniques since their impact on the data cannot be recognised. These uncertainties may include sonic and VR data quality, VR to temperature translation model, etc.
Observations from temperature-depth plots for Kidson-1 and Wilson Cliffs-1, located within the eastern part of the Kidson Sub-basin indicate anomalous high temperature measurements interpreted as reworked vitrinite or the effect of localised heating ( Fig. 8a and 8b). Although the source of these anomalous high temperatures is inconclusive, they are only observed within the eastern part of the basin. Moreover, the difference in the magnitude of exhumation estimated using the thermal method are extremely high compared to estimates from the compaction method at these well locations with differences of 540 m and 1700 m at Kidson-1 and Wilson Cliffs-1 respectively (Table 5). Although, other wells including Patience-2 and Contention Heights-1 located within the eastern part of the basin do not show any anomalous high temperature data, they also show similar pattern where the thermal technique yielded very high exhumation estimates compared to the compaction technique (Table 5). Differences in the magnitude of exhumation are 570 m and 1000 m for Patience-2 and Contention Heigths-1 respectively.
However, wells located within the western part of the sub-basin, including Frankenstein-1 and Nicolay-1 do not show anomalous temperature data points. Also, at these well locations, there is very small variation in exhumation estimates between both methods with differences of 200 m and 100 m for Frankenstein-1 and Nicolay-1 respectively (Table 5). This small variation in exhumation estimates between the compaction and thermal method are consistent with other studies where both techniques have been employed and where no anomalous high temperature measurements were reported. For example, results from the UK Southern North Sea indicate that the thermal technique using VR and AFTA yielded higher estimates in the order of 300 to 500 m greater than estimates using the compaction method (sonic transit time) at the various well location (Hillis, 1995). Also, in the Southern Bonaparte Basin, the thermal technique yielded higher estimates ranging from 20 to 750 m higher than the compaction method (Makuluni et al., 2021). This small variation in exhumation estimates by both techniques is expected for areas where the interested unconformity is not at the present-day ground level. This is because subsequent sediment loading reduces the gross exhumation, which is the vertical displacement between the reference curve and the anomalous curve (depth of the sample) at the time of exhumation. (Corcoran and Doré, 2005;Hillis, 1995). As a result, the present estimated exhumation magnitude using the compaction method which is represented by the difference between the reference curve and present-day depth of the sample is reduced by an amount that is equal to the post exhumation reburial (Corcoran and Doré, 2005;Hillis, 1995). Thus, the magnitude of estimated exhumation using the compaction method represents minimum estimates as opposed to the total amount of exhumation that occurred at the time of denudation (Corcoran and Doré, 2005;Hillis, 1995; Licciardi et al., 2020).This reduction in the amount of exhumation is termed apparent exhumation by Hillis (1995) and net exhumation by Corcoran and Doré (2005) and Licciardi et al., (2020). The amount of post-exhumation reburial may vary across the basin as it depends on loading factors such as the volume and density of overlying sediments (Allen and Allen, 2013). These factors may vary across the basin and explain the small variation in exhumation estimates obtained by both methods for wells in the western part of the basin.
On the other hand, in areas where the thermal method (VR) estimated anomalously high exhumation magnitudes, compared to the compaction method for the same well location, VR oxidation effects (Hillis, 1995) or localised heating bodies such as hot fluids or intrusives accounted for higher VR values (Dow, 1977;Duddy et al., 1994) and the higher exhumation estimates associated with the thermal (VR) method. VR data quality including oxidation effects are not considered as they may be difficult to recognise in secondary VR data. Although igneous intrusives have not been reported in the Kidson Sub-basin, they have been reported in other parts of the Canning Basin including Fitzroy Trough and Lennard Shelf (Arne et al., 1989;Hashimoto et al., 2018). Also, sediment hosted base metal deposits as well as uranium deposits have been reported in the Canning Basin (Botten, 1984;Mccracken et al., 1997;Veamcombe et al., 1995). These deposits are associated with hot hydrothermal fluid circulation (Hoggard et al., 2020). Although external heating bodies such as hydrothermal fluids and igneous intrusives may influence porosity of the surrounding sediments, VR are more susceptible to variations in temperature (Johnson et al., 2017;Makuluni et al., 2021). Thus, the occurrence of anomalous high temperature measurements and associated high exhumation magnitudes estimated by the thermal (VR) method and the wide variation in exhumation estimates between both techniques obtained from wells in the eastern part of the Kidson Sub-basin strongly suggest that temperature signatures of sediments in the eastern part of the basin have been influenced by localised heating bodies. As a result, these anomalous high exhumation estimates obtained by the thermal technique for wells in the eastern part of the Kidson Sub-basin are over-estimated. Exhumation magnitudes estimated by the compaction method have therefore been used for further analysis and discussion.

Comparison of present study with earlier exhumation studies
The work of Kennard et al. (1994b) represents the only extensive exhumation studies within the Kidson Sub-basin. Their work involved the estimation of magnitude of exhumation through time using the WinBury 1.4 geohistorical analysis program. Their study used a wide range of paleo-thermal indicators including Vitrinite Reflectance (VR), Spore Colour Index (SCI), Conodont Colour Alteration Index (CAI =Ro equivalent), Thermal Alteration Index (TAI) and Tmax obtained from Rock-Eval Pyrolysis. However, minimum exhumation estimates from this study obtained using the compaction method (see 5.2 for discussion) during the various exhumation episodes are higher than estimates from Kennard et al. (1994b) (Table 6). Moreover, more recent studies from VR and AFTA data within other parts of the Canning Basin also indicate higher magnitude of exhumation during the Early Jurassic period compared to Kennard's study. For example, Duddy et al. (2006) and Green (2014) concluded that between 800-2800 m (maximum likelihood estimate of 1300 m) and between 950-1950 m (maximum likelihood estimate 1400 m) of sediments were removed at Acacia-2 and McLarty-1, respectively during the Early Jurassic Exhumation period. However, Kennard et al. (1994b) estimated 400 m and 450 m of uplift and erosion at those well locations.
We have not investigated the accuracy and limitations of WinBury 1.4 geohistorical analysis program. However, major possible sources of error in exhumation estimates by Kennard et al. (1994b) come from their approach in the use of paleo-thermal data. In their study, paleothermal data at individual well locations were divided into 3 sections with the assumption that peak paleo temperatures were attained at three different periods corresponding to major extension events in the Kidson Sub-basin. Thus, paleo-thermal data obtained from sediments deposited during a particular heating episode were used to estimate the amount of exhumation during the following inversion episode. For example, paleo-thermal data from Ordovician to Early Silurian sediments were assumed to represent the paleo-thermal maximum during the Ordovician to Silurian extension and heating episode. These were used to estimate the amount of exhumation during the succeeding inversion episode in the Early Devonian period. Similar approach was employed to estimate the magnitude of exhumation during other inversion episodes. Thus, a major limitation with their approach was the division of paleo-thermal data from individual wells into segments, which were not constrained by required timing information (example AFTA). Instead, the division was based on the timing of extension and associated Subsidence with the assumption that each extension episode corresponded to maximum heating. Applying the methodology and constraints used in this study to raw paleo-thermal data obtained from the work of Kennard et al. (1994b) would provide a more suitable basis for comparison of results as minor errors that may be associated with variation in data will be eliminated. However, raw paleo-thermal data employed by Kennard et al. (1994b) were not available for such analysis and comparison.
As discussed in section 4.3, recent data from AFTA and burial history modelling put important constraints on paleo-thermal data in the Kidson Sub-basin. These constraints imply that maximum heating in the Kidson Sub-basin was attained in the Late Triassic to Early Jurassic period (section 4.3). In this instance, previous heating and thermal records were overridden by the thermal event of the Late Triassic to Early Jurassic period. This implies that the entire paleo-thermal data (VR, CAI, TAI, SCI) obtained from stratigraphic units at the individual well locations employed by Kennard et al. (1994b) corresponds to a single and uniform heating episode associated with the Late-Triassic to Early Jurassic heating episode. It also means that, obtained paleo-thermal data are only appropriate for estimating the magnitude of exhumation during the cooling and exhumation period in the Early Jurassic which immediately followed the paleo-thermal maximum. Thus, the separation of paleothermal data into distinct thermal episodes may contribute to the very low exhumation estimates in the Kidson Sub-basin during the various inversion episodes as employed by Kennard et al. (1994b). 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64  65   Table 6. Comparison of the magnitude of exhumation estimated by Kennard et al. (1994b) and this study

Implication of exhumation magnitudes on the tectonic evolution of the Kidson Subbasin.
The magnitude of exhumation estimated by using the compaction method during the various inversion episodes have been compared. In general, the magnitude of exhumation increased from southeast to northwest during all the inversion episodes ( Fig. 11 and 12). Also, results indicate that the magnitude of exhumation increased progressively with the evolution of the Kidson Sub-basin with the lowest magnitudes recorded during the earliest inversion episode (late Silurian to Early Devonian Prices Creek Compression), medium exhumation estimates recorded during the second inversion episode (middle Carboniferous Meda Transpression) and highest exhumation magnitudes recorded during the latest inversion period (Early Jurassic Fitzroy Transpression) (Fig. 12 A1, B and C; Table 5).
Results therefore indicate that factors controlling the magnitude of exhumation were more pronounce in the western and north-western part of the sub-basin. Also, the progressive increase in the magnitude of exhumation with time indicate that factors these factors became 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64 more pronounced with time. The magnitude and distribution of exhumation in a terrane during an inversion episode are affected by several factors demonstrated by theoretical studies (Cloetingh and Ziegler, 2007;Turner and Williams, 2004;Ziegler et al., 1995), numerical, experimental and analogue models (Casas et al., 2001;Cerca et al., 2010;Cloetingh et al., 2008Cloetingh et al., , 2005Dooley and Schreurs, 2012;Schellart and Strak, 2016). These factors include inherited basement weaknesses, magnitude and direction of the stress fields associated with the compressional deformational event, proximity of the basin to the centre of the stress field, involvement of magmatic activity, etc. We therefore discuss the causes of the various exhumation events to investigate the probable cause of such exhumation pattern.
The early inversional events, the Meda Transpression and Prices creek compression which affected the entire Canning Basin are suggested to be far field effects of peak episodes (Pertnjara and Mt Eclipse Episodes) of the Alice Springs Orogeny (Hashimoto et al., 2018;Klootwijk, 2013;Munroe et al., 2004;Shaw et al., 1994). The Alice Spring Orogeny is in turn thought to be the far field effects of Gondwana-Laurussia collision (Klootwijk, 2013;Li and Powell, 2001). This Orogeny was a north-south directed thrusting concentrated within Central Australian including the Arunta region, Amadeus, Officer, Ngalia and Georgina Basins, (Edgoose, 2012;Haines et al., 2001;Hand and Sandiford, 1999). These regions are located east and south of the Kidson Sub-basin. In fact, Amadeus Basin is thought to have been connected to the eastern Canning Basin (Kidson Sub-basin area) during the Ordovician (Larapintine Seaway) (Haines et al., 2013;Haines and Wingate, 2007). Compressive deformational stress transmitted from the collisional front (Amadeus basin region) during the Pertnjara and Mt Eclipse events of the Alice Spring Orogeny would have first reached the eastern and south eastern parts of the Kidson Sub-basin. Thus, the intensity of compressive stress would have been highest within these areas and would have decreased westward across the Kidson Sub-basin. Since the intensity of compressive stress fields are directly related to the amount of deformation (Turner and Williams, 2004), the magnitude of exhumation is expected to also be highest in the eastern part of the basin and decreased westward. However, results indicate otherwise (Fig. 12) and therefore suggests that the distribution of exhumation in the Kidson Sub-basin during the Prices Creek Compression and Meda Transpression was controlled by factors other than the intensity of the compressive stress fields. Since the development of the Kidson Sub-basin is associated with the overall development of the Canning Basin, results from the Kidson Sub-basin alone may not be enough to explain the variation in exhumation magnitudes with space and time. Combining these results with other exhumation magnitudes from various parts of the Canning Basin will provide regional evidence to draw conclusions. However, major fault zones and fault systems that were developed during the early basin history were concentrated in the Northern part of the Canning Basin, Fitzroy Trough-Gregory Sub-basin complex and the Broom platform areas (Bradshaw et al., 2012;Romine et al., 1994). Moreover, the basement underlying the Kidson Sub-basin is considered to be stronger compared to the weak basement underlying the northern and western parts of the Canning Basin (Connors et al., 2018). This imply that basement units underlying the north-western margins of the Kidson Sub-basin were relatively weaker and more deformed and the strength of basement units increased towards the southeast before the onset of the compressional deformation. Analogue models indicate that the effects of compressional stress are intensified in areas of weak basement units (Dooley and Schreurs, 2012;Schellart and Strak, 2016). Thus, the increase in exhumation magnitudes from south-east to north-west across the Kidson Sub-basin during the Prices Creek and Meda   1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64  65 Transpression may be attributed to heterogeneities (weaknesses) in basement units which increases from east to west or (south-east to north-west) across the Kidson Sub-basin.
Similar pattern of exhumation distribution is observed in the Kidson Sub-basin during the last major inversional deformation, the Fitzroy Transpression. The Fitzroy Transpression resulted from compressional strike-slip movement propagated from a triple junction that was situated within the adjacent Roebuck basin during the early rifting phase of the North West Shelf (MacNeill et al., 2018). The triple junction was initiated by a magmatic plume which also caused extensive regional uplift in areas located close to the plume centre (MacNeill et al., 2018). Although results from Kidson Sub-basin alone are not conclusive, the increase in the magnitude of exhumation from north west to south-east across the Kidson Sub-basin during this event, similar to the previous exhumation events indicate a similar tectonic response of basement units to compressive deformation as described above. However, during this event compressional stresses were propagated from the Northwest (Roebuck Basin).
The noticeable progressive increase in the magnitude of exhumation with time ( Fig. 12) also imply that factors controlling exhumation increased progressively with time. These factors may include variation in intensity of deformational stress, basement heterogeneities with time (Cloetingh et al., 2005;Ziegler et al., 1995). There is no available data to compare the intensity of compressive stresses that reached the Kidson Sub-basin during the various compressional episodes. However, Shaw et al. (1994) indicated that the during the evolution of the Canning Basin, the extensional and compressional deformational events progressive weakened basement structures. Such weaknesses evolved as zones of thickened crust, crustal or lithospheric-scale faults or a regional boundary represented by density discontinuity and these weak zones progressively became the focus for future deformation (Shaw et al., 1994). Thus, the progressive weaknesses in basement units may play a significant role in intensifying the magnitude of future exhumation events, explaining the progressive increase in exhumation with time. This concept may also explain the emplacement of igneous intrusives during the latest inversion episode (Fitzroy Transpression) identified in the Fitzroy Trough and Lennard Shelf area.

Summary and Conclusion
In this study, we investigated the amount of exhumation during major inversion episodes in the Kidson Sub-basin by integrating a wide range of data set including seismic, stratigraphic, core, well-log, porosity and thermal data. We identified four major unconformities associated with major inversion periods that led to exhumation in the basin. These inversion episodes are Prices Creek Compression, which occurred from the middle Silurian to Early Devonian, Meda Transpression, which occurred from the middle Carboniferous to Early Devonian, Fitzroy Transpression, which occurred from the Late Triassic to Early Jurassic and Tertiary Compression, which occurred in the Eocene era.
Two independent methods, namely, thermal and compaction techniques were employed to estimate the magnitude of exhumation during three major inversion episodes in the Kidson Sub-basin. These independent methods both provide important constraints on results. Results indicate that at least 300-500 m of exhumation occurred during the Prices Creek Compression, 500 to 750 m of exhumation occurred during the Meda Transpression and 800 to 1200 m of exhumation occurred during the Fitzroy Transpression. Integration of timing constraints from Apatite Fission Track Analysis (AFT) data and burial history analysis indicate the Vitrinite Reflectance (VR) obtained at the individual well location represent a single uniform heating episode during the Late Triassic. Results indicate that thermal signatures of sediments in the eastern part of the Sub-basin have been influenced by external bodies.