Northwest Shelf Of Australia Research Articles

Discussion/comments regarding “Trends in pCO2 and sea–air CO2 flux over the global open oceans for the last two decades” by Y. Iida, A. Kojima, Y. Takatani, T. Nakano, H. Sugimoto, T. Midorikawa, M. Ishii

A paper by Iida et al. that was recently published in this journal (J Oceanogr 17:637–661, 2015) presented trends in the partial pressure of carbon dioxide in surface seawater and the estimated sea–air carbon dioxide flux over the global open oceans for the last two decades. The purpose of the present discussion is to demonstrate that the formula used by Iida et al. in their assessments can also be employed to estimate the sea–air carbon dioxide flux based on long-term wind statistics, i.e., based on data showing how the mean wind speed 10 m above the sea surface has varied over a long period. Examples of the application of this approach are given here, based on long-term wind statistics for the northern North Sea and the North West Shelf of Australia.

Multi-Year Observation of Holloway Current along the Shelf Edge of North Western Australia

ABSTRACT Bahmanpour, M.H.; Pattiaratchi, C., Wijeratne, E.M.S., Steinberg, C., and D'Adamo, N., 2016. Multi-year observation of a boundary current along the shelf edge of North Western Australia. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 517–521. Coconut Creek (Florida), ISSN 0749-0208. Analysis of multi-year current meter data across North West shelf of Australia identified various aspects of the mean flow in a macro-tidal environment. Main features of the flow appear to be a continuous alongshore south-westward flow, i.e., Holloway current located along the continental shelf edge in depth 100–200 m. Annually, the current transports ∼ 1 Sv of lower salinity, higher temperature water from the tropical regions to North West Cape. The Holloway current is at its maximum intensity (up to 2 Sv) during autumn/winter (Apr–Jul) when the winds are ei...

Stress‐induced seismic azimuthal anisotropy in the upper crust across the North West Shelf, Australia

AbstractSeismic azimuthal anisotropy (SAA) is observed in many areas of the Earth, and fast polarized directions (ϕ) have been mapped using earthquake surface waves and teleseismic S wave splitting over large regional and tectonic scales. Higher‐resolution petroleum exploration data, including 3‐D seismic surveys and dipole shear logs, often exhibit azimuthal anisotropy; however, we are unaware of any published studies mapping SAA from exploration‐scale data to study large‐scale regional and tectonic SAA trends. The physical mechanisms causing SAA in earthquake data are a subject of great interest; comparing regional ϕ trends to the higher‐resolution exploration trends may help understand these mechanisms. We present a SAA analysis using seismic exploration data across the North West Shelf (NWS) of Australia. We map the fast polarization directions ϕ from 34 dipole shear logs and two 3‐D seismic surveys and compare them to in situ maximum horizontal stress orientations (σH). Our results show that the ϕ and σH trends correlate across a geographical area spanning almost 2000 km and are similar to published results in the region from earthquake seismology. These results suggest that differential horizontal stress is the likely mechanism causing SAA at a wide range of spatial scales on the NWS of Australia. We also show that SAA is not observed at exploration scales in some areas of the NWS and propose a lithology‐dependent stress sensitivity model in which SAA is strongest in clean, unconsolidated quartz‐dominated sandstones and weaker or nonexistent in well‐consolidated cemented rocks and shale‐dominated sediments.

Calibration of Early Cretaceous dinoflagellate zones from the NWS of Australia to the global time scale through calcareous nannofossils

Palynomorphs and nannofossils were examined from the Lower Cretaceous interval of the well North Scarborough-1, drilled on the Exmouth Plateau, North West Shelf of Australia. Integration of the chronostratigraphic information from both fossil groups revealed discrepancies in the age information with the nannofossils suggesting a younger age than dinoflagellate cysts. The nannofossil events have a stronger tie to the global time scale than the dinoflagellate zones which are mainly local. The direct comparison of nannofossil and dinoflagellate events in the same section allows for improved stratigraphic precision and a revised correlation of Australian dinoflagellate zonal ages to the global time scale, GTS12. Global nannofossil ages confirm a Barremian–late Hauterivian age for the Muderongia australis Zone, but the Systematophora areolata to Dissimulidinium lobispinosum Zones appear to be 1–2 my younger than previously estimated.

Willem 3D: Reprocessed, inverted, revitalized

The Carnarvon Basin on the North West Shelf of Australia is a world-class hydrocarbon province, with the pace of discoveries significantly accelerating in the last 15 years. The high success rate has been aided by improvements in seismic data quality, hydrocarbon detection techniques, and widespread 3D seismic surveys. This has led to the identification of several new play concepts, an increase in target depths, and an extension into more difficult seismic data areas. New broadband acquisition technologies undoubtedly have delivered a significant enhancement in many parts of the basin, but there is still much to be gained from existing 3D seismic data sets. Broadband seismic data reprocessing, prestack depth migration, and facies-based seismic inversion can offer a cost-efficient exploration tool to maintain the historical success rates. The open-file Willem 3D seismic survey adjacent to the giant Io/Jansz, Wheatstone, and Pluto gas fields is located in an area that has been explored insufficiently. The 2006 seismic data originally were regarded to be of good quality, but with advancements in acquisition and reprocessing techniques, the imaging result is now considered to be poor relative to modern-day seismic data sets. The Urania-1 gas discovery and northern extent of the Pluto field were detected on the original data, but other prospects based on this data set proved to be unsuccessful. The complex overlying Tertiary channels and the presence of shallow strong seismic attenuation caused historical data-imaging limitations. Recent prestack depth-migration reprocessing has improved the data quality, with deghosting providing a significant uplift throughout the processing workflow. A facies-based inversion of the reprocessed data has delineated the known gas accumulations successfully and has predicted the location and dimensions of the recent Woodside Petroleum Pyxis-1 gas discovery.

Wave-equation multiple imaging (WeMi) — Swimming between the flags

Deghosting dual-sensor streamer seismic data requires separation of the total recorded wavefield into upgoing and downgoing components during seismic preprocessing. Imaging of multiples exploits the wavefield separation process by using the downgoing wavefield at each receiver location as a virtual source. Multiple imaging has been shown to effectively remove shallow-acquisition-related artifacts commonly seen on wide-tow marine seismic surveys and improve imaging quality of the shallow overburden. Acquisition design factors, imaging condition, and cross-talk noise are the main factors that determine the effectiveness of separated wavefield imaging (SWIM) of dual-sensor streamer data. (SWIM is a common nontrademarked acronym used in the literature to describe multiple imaging of separated wavefields sampled from dual-sensor streamer data.) In a field trial, acquisition design did not allow for proper sampling of the total wavefield, with the result that multiple imaging did not prove to be as robust a technique as examples in the literature might imply. Understanding the effects of acquisition design parameters on image quality is essential to more successfully apply multiple-imaging techniques with greater relevance on the North West Shelf of Australia.

High Resolution Anisotropic Earth Model Building on Conventional Seismic Data Using Full Waveform Inversion: A Case Study Offshore Australia

SUMMARY We present a case study from the North West Shelf of Australia where the complexity of the overburden consists of several thin multi-level channel systems filled with a combination of anomalously high or low velocity sediments. Not accounting for these strong velocity variations accurately, can lead to subtle image distortions affecting the underlying section down to and including the reservoir level. This can have significant impact on the volumetric estimates of reserves in place. To resolve these complexities in the overburden, full waveform inversion (FWI) was utilized to generate an updated earth model exploiting both early arrivals and reflection events. One caveat to using full waveform inversion is the need for low frequencies to be present in the seismic data, or, the initial starting velocity model must contain the correct low wavenumber components. However, seismic acquired at shallow tow depths are usually band limited particularly at the very low frequencies. Our case study will discuss these issues along with other limitations that this conventional data presented along with the workflows and quality control methods adapted to this in order to converge to a plausible, high resolution earth model.

Layer-induced scattering attenuation and VTI anisotropy - NW Shelf Australia synthetic study

SUMMARY Seismic attenuation and anisotropy in the overburden can significantly affect seismic image quality, including amplitudes of the target horizons. Therefore, understanding magnitudes, causes and spatial distribution of attenuation and anisotropy is important for seismic imaging and reservoir characterization. Thin layering can cause both scattering attenuation and anisotropy. These phenomena can only be significant, if there is a strong contrast in elastic properties between the layers. We present a case study from North-West Shelf of Australia, where presence of shallow stiff carbonate layers can be responsible for deterioration of seismic data quality through both attenuation and anisotropy.

IODP Expedition 356: Drilling to reveal a 5 million year carbonate and subsidence history on the Northwest Shelf of Australia

The late Cenozoic carbonates of the Northwest Shelf are important subsidence history archives that also cause significant sonic velocity problems affecting seismic imaging of underlying strata. Despite their substantial thickness and areal extent, these carbonates have been sampled only in engineering foundation boreholes and as cuttings and rare sidewall cores in petroleum wells. In August-September 2015 the International Ocean Discovery Program (IODP) will drill a transect of shelf to shelf margin cores in this region. Six sites will be drilled over 10° latitude from the Perth Basin to the Bedout sub-basin by RV JOIDES Resolution with continuously cored penetrations of 300 m to 1.1 km. An array of shipboard and post-cruise biostratigraphic, sedimentological and geochemical analyses will be carried out on these cores to achieve three primary aims: 1. Provide empirical input into the spatiotemporal patterns of subsidence along Northwest Australia that can be used to place fundamental constraints on the interaction between Australian plate motion and mantle convection and to ground truth geodynamic models. 2. Determine the timing and variability of regional oceanographic features in order to understand the controls on Neogene carbonate stratigraphy and reef development. 3. Obtain a tropical to subtropical climate and ocean archive, directly comparable to deep-ocean oxygen isotope and ice-core archives, to chart the variability of the Australian monsoon and the onset of aridity in northwestern Australia. Each site will be triple cored using a combination of Advanced Piston Coring (APC), Extended Core Barrel (XCB) and Rotary Core Barrel (RCB). An array of downhole measurements will be taken using three standard IODP tool string configurations: the triple combination (triple combo), Formation MicroScanner (FMS)-sonic, and Versatile Seismic Imager (VSI). These will be used to correlate the cores to regional multichannel seismic profiles in order to gain a better understanding of Northwest Shelf stratigraphy and neotectonics.

Mesozoic lithofacies palaeogeography and petroleum prospectivity in North Carnarvon Basin, Australia

The North Carnarvon Basin, which lies in the North West Shelf of Australia, is highly rich in gas resources. As a typical passive marginal basin, it experienced the pre-rifting, early rifting, main rifting, late rifting, post-rifting sagging and passive margin stages. The basin was mainly filled with thick Mesozoic-Cenozoic sediments, of which the Mesozoic hosts the principal source, reservoir and seal intervals. Mesozoic palaeogeography has an important control on the oil and gas distribution. Triassic gas-prone source rocks of deltaic origin determine the high endowment of natural gases in the North Carnarvon Basin. The more restricted distribution of oil accumulations is controlled by oil source rocks in the Upper Jurassic Dingo Claystone. The Muderong Shale deposited in the Early Cretaceous marine transgression provides the effective regional seal for the underlying oil and gas reservoirs.

A RaMM study of thermal maturity of dispersed organic matter in marine source rocks

The Raman Maturity Method (RaMM) is a non-graphical technique for thermal maturity determination based on the multi-linear regression analysis of parameters derived from carbon Raman spectra of humic macerals. It is calibrated against vitrinite reflectance with a suite of Australian mostly Permian coals. In a previous communication an equation to cover the range 0.4–1.2% equivalent vitrinite reflectance was derived. In this report we extend the range with a second equation for the range 1.0–2.5%, and validate its use by testing a series of Australian Permian and German Carboniferous coals. The special features of the technique are that it is equally applicable to vitrinite and inertinite, it corrects internally for the suppression of vitrinite reflectance effect, grains as small as 5μm are suitable, and it does not require well depth information to be available.The technique has been applied to two wells, Cape Range-2 and Dampier-1, from the rift margin of the North West Shelf of Australia. Both wells intersect large thicknesses of fine-grained marine Jurassic and Cretaceous sediments including the major source rock formation of the Carnarvon Basin. There are no terrestrial sediments for control. There is good agreement between RaMM and VR results for VR>1.2% for Cape Range-2. However within the oil window in both wells RaMM results indicate the vitrinites in many of the samples have reflectance suppression to such a degree that the VR results would be misleading or useless for maturity modeling. It is likely that this problem, which is well documented for marine influenced coals, to some degree affects organic matter in marine source rocks worldwide.

Estimating azimuthal stress‐induced P‐wave anisotropy from S‐wave anisotropy using sonic log or vertical seismic profile data

ABSTRACTMost sedimentary rocks are anisotropic, yet it is often difficult to accurately incorporate anisotropy into seismic workflows because analysis of anisotropy requires knowledge of a number of parameters that are difficult to estimate from standard seismic data. In this study, we provide a methodology to infer azimuthal P‐wave anisotropy from S‐wave anisotropy calculated from log or vertical seismic profile data. This methodology involves a number of steps. First, we compute the azimuthal P‐wave anisotropy in the dry medium as a function of the azimuthal S‐wave anisotropy using a rock physics model, which accounts for the stress dependency of seismic wave velocities in dry isotropic elastic media subjected to triaxial compression. Once the P‐wave anisotropy in the dry medium is known, we use the anisotropic Gassmann equations to estimate the anisotropy of the saturated medium. We test this workflow on the log data acquired in the North West Shelf of Australia, where azimuthal anisotropy is likely caused by large differences between minimum and maximum horizontal stresses. The obtained results are compared to azimuthal P‐wave anisotropy obtained via orthorhombic tomography in the same area. In the clean sandstone layers, anisotropy parameters obtained by both methods are fairly consistent. In the shale and shaly sandstone layers, however, there is a significant discrepancy between results since the stress‐induced anisotropy model we use is not applicable to rocks exhibiting intrinsic anisotropy. This methodology could be useful for building the initial anisotropic velocity model for imaging, which is to be refined through migration velocity analysis.

Madden Julian Oscillation impacts on global ocean surface waves

We assess the impact of the tropical Madden Julian Oscillation (MJO) on global ocean wind waves using 30 years of wave data from a wave model hindcast that is forced with high resolution surface winds from the NCEP–CFSR reanalysis. We concentrate on the boreal winter season when the MJO has its greatest amplitude and is potentially a source of predictable wave impacts at intra-seasonal lead times. Statistically significant anomalies in significant wave height (Hs), peak wave period (Tp) and zonal wave energy flux (CgE) are found to covary with the intra-seasonal variation of surface zonal wind induced by the MJO as it traverses eastward from the western tropical Indian Ocean to the eastern tropical Pacific. Tp varies generally out of phase with Hs over the life cycle of the MJO, indicating that these MJO-wave anomalies are locally wind-generated rather than remotely generated by ocean swell.Pronounced Hs anomalies develop on the northwest shelf of Australia, where the MJO is known to influence sea level and surface temperatures, and in the western Caribbean Sea and Guatemalan–Panama Seas with enhanced wave anomalies apparent in the vicinity of the Tehuantepec and Papagayo gaps. Significant wave anomalies are also detected in the North Pacific and North Atlantic oceans in connection with the MJO teleconnection to the extratropics via atmospheric wave propagation. The impact in the north Atlantic stems from induction of the high phase of the North Atlantic Oscillation (NAO) about 1 week after MJO convection traverses the Indian Ocean, and the low phase of the NAO about one week after suppressed convection traverses the Indian Ocean. Strong positive Hs anomalies maximize on the Northern European coast in the positive NAO phase and vice versa for the negative NAO phase. The MJO also influences the occurrence of daily low (below the 5th percentile) and high (above the 95th percentile) wave conditions across the tropics and in the North Pacific and North Atlantic, emphasizing that the MJO may be a valuable source of intra-seasonal predictability of surface wave variability.

Structural style in a young flexure-induced oblique extensional system, north-western Bonaparte Basin, Australia

In the north-western Bonaparte Basin (North West Shelf of Australia) Neogene to Recent flexure-induced extension superimposed obliquely over the Mesozoic rift structures. Thus, the area offers a good opportunity to investigate the dynamics and architecture of oblique extension fault systems. Analysis of basin-scale 2D and 3D seismic data along the Vulcan sub-basin shows that Neogene deformation produced a new set of extensional, en échelon faults, at places accompanied by the reactivation of the Mesozoic faults. The pre-existing Mesozoic structures strongly control the distribution of the Neogene-Recent deformation, both at regional and local scales. Main controls on the Neogene-Recent fault style, density and segmentation/linkage include: (1) the orientation of the underlying Mesozoic structures, (2) the obliqueness of the younger extension relative to the rift-inherited faults, and (3) the proximity to the Timor Trough. Three types of vertical relationships have been observed between Mesozoic and Neogene-Recent faults. Hard linkages seems to develop when both fault systems trend parallel, therefore increasing risks for trap integrity. It is suggested that the orientation of maximum horizontal stress (SHmax) relative to the Mesozoic faults, forming hydrocarbon traps, is critical for their potential seal/leak behaviour. Stratigraphic growth across the faults indicates that main fault activity occurred during the Plio-Pleistocene, which corresponds to the timing of tectonic loading on Timor Island and the development of lithospheric flexure. Synchronism of normal faulting with flexural bending suggests that extensional deformation on the descending Australian margin accompanied the formation of the Timor Trough.

Evidence for the biotic origin of seabed pockmarks on the Australian continental shelf

The generally accepted formation mechanism of pockmarks worldwide is the expulsion of fluid at the seafloor, but such a mechanism does not explain the close association between pockmarks and seabed infrastructure such as pipelines and wellheads within the Stag oil field on the North West Shelf of Australia. Furthermore, certain characteristics of the pockmarks, such as conical mounds of sediment positioned around their perimeters, are strongly suggestive of a biotic origin. Pockmarks in this case are typically 5 m in diameter and 1 m deep, excavated within a sandy seabed in 45 m water depth. Inspection of ROV footage acquired during oilfield operations within the Stag field supports but does not entirely confirm without doubt the proposition that the pockmarks are created by fish of the genus Epinephelus.Having determined the characteristic features of pockmarks within the Stag field which mark them as biotic excavations, data from commercial seabed surveys at 11 other sites on the North West Shelf, all of which reveal numerous pockmarks, was reviewed for evidence of similar pockmark characteristics. Based on the review, it appears likely that the majority of pockmarks on the shallow North West Shelf (between 40 m and 130 m water depth) are representative of biological rather than geological activity. The probability that pockmarks less than approximately 10 m in diameter throughout the remainder of the Australian continental shelf are also the result of purely biological activity is high, as demonstrated by the analysis of data from three further sites.Close inspection of seabed survey data from further afield could extend the findings of this paper throughout not only the tropical Indo-West Pacific (the range of the particular fish species implicated on the North West Shelf), but potentially worldwide if other species can be shown to display similar behaviour.

How frequency dependency of Q affects spectral ratio estimates

Because seismic amplitudes can be affected by purely geometrical factors, attenuation is often estimated not from amplitudes but from the evolution of the amplitude spectra of the waveform. Such estimation methods (e.g., the spectral ratio method and the centroid frequency shift method) assume that the quality factor [Formula: see text] is constant (independent of frequency) in the frequency band of the signal. If this assumption is violated, then [Formula: see text] estimates become biased. In particular, when the frequency dependency of [Formula: see text] is a power law [Formula: see text], then [Formula: see text] is systematically under- or overestimated by a factor of [Formula: see text]. The errors are larger for larger values of [Formula: see text], particularly when [Formula: see text] is negative. In particular, if [Formula: see text], the frequency content of the signal does not change, and [Formula: see text] is estimated to be infinite, regardless of the true value of [Formula: see text]. To avoid these systematic errors, it is necessary to monitor the evolution of frequency content and amplitude with distance. Zero-offset vertical seismic profile data from the North West Shelf of Australia revealed the decay of the signal amplitude with depth that can be explained by a combination of intrinsic constant [Formula: see text] and a frequency-independent factor, which in turn is caused by the geometric spreading plus transmission loss due to variations of acoustic impedance on a scale larger than the dominant wavelength in the signal.

Joint met-ocean description for design and operations of marine structures

For several engineering applications, joint met-ocean probabilities are required. Recently increasing attentions have been given to importance of inclusion wind-sea and swell components in the joint description. Presence of wind-sea and swell will affect design and operability of fixed and floating offshore structures as well as LNG terminals. The study presents a joint met-ocean model which can be applied for design and operations of marine structures, including LNG platforms. The model is fitted to hindcast data from four locations: Southern North Sea, West Shetland, and Northwest Shelf of Australia and off coast of Nigeria. Uncertainties related to the proposed fits are examined focusing on location specific features of the wave climate and an adopted partitioning procedure for the wave components. Implications of the uncertainties on design and operation criteria of LNG platforms are discussed and demonstrated by examples.

Prospectivity insights from automated pre-interpretation processing of open-file 3D seismic data: characterising the Late Triassic Mungaroo Formation of the Carnarvon Basin, North West Shelf of Australia

Waveform data from pre-interpretation processing is used in nine Late Triassic interpretation case studies from an area extending more than 30,000 km2 across the Exmouth Plateau, Kangaroo Trough and Rankin Trend on the North West Shelf of Australia. Events selected from a database of automatically generated surfaces extracted from six large open-file 3D marine surveys (~16,000 km2) are used to analyse reservoirs, seals, and pore fluid within the Brigadier and Mungaroo formations in this peer-reviewed paper. Today, geoscience teams are challenged with vast data sets such as the archived versions of more than 125 Carnarvon Basin 3D seismic surveys. Pre-interpretation processing delivers a database of numerous seismic events that cannot be effectively managed using traditional interpretation workstations. With, however, a 3D viewer to query, edit and merge the results, geoscience teams are able to review many large surveys and the surfaces in their interpretation workflows. At the 2013 WABS Conference in Perth, WA, two papers offered models for the Late Triassic gas reservoirs. These models represent many years of synthesis and integration of data by teams of geoscientists from two of the major operators on the North West Shelf. Validation and corroboration of the proposed models was gained by using selected pre-interpretation surfaces. Stacking patterns, waveform fitness, amplitude and two-way time surfaces from these spatial databases revealed geological insights about the formations, such as their complexity of structure, extent of reservoirs, and continuity of seals, along with a better understanding about the trapping and charge systems of the fields.

Rift processes in the Westralian Superbasin, North West Shelf, Australia: insights from 2D deep reflection seismic interpretation and potential fields modelling

Acquisition of long-offset (8–10 km), long-record length (12–18 sec), 2D reflection seismic and ship-borne potential fields data (WestraliaSpan by Ion/GXT and New Dawn by PGS) on the North West Shelf of Australia provide the opportunity to study rift processes in the context of modern models for rifted margins (Manatschal, 2004). Basement and Moho surfaces were interpreted on seismic reflection data. Refraction models from Geoscience Australia constrain Moho depth and initial densities for gravity modelling through standard velocity-density transformation. 2D joint inversion of seismic reflection and gravity data for Moho depth and basement density constrain depth to basement on seismic. 2D gravity and magnetic intensity forward modelling of key seismic lines constrain basement thickness, type and density. Late Permian and Jurassic-Early Cretaceous rift zones were mapped on seismic reflection data and constrained further by inversion and forward modelling of potential fields data. The Westralian Superbasin formed as a marginal basin in Eastern Gondwana during the Late Permian rifting of the Sibumasu terrane. Crustal necking was localised along mechanically-weak Proterozoic suture belts or Early Paleozoic sedimentary basins (such as Paterson and Canning). Mechanically-strong cratons (such as Pilbara and Kimberley) remained intact, resulting in necking and hyper-extension at their edges. Late Permian hyper-extended areas (such as Exmouth Plateau) behaved as mechanically-strong blocks during the Jurassic to Early Cretaceous continental break-up. Late Permian necking zones were reactivated as failed-rift basins and localised the deposition of the Jurassic oil-prone source rocks that have generated much of the oil discovered on the North West Shelf.

A New Model for Coastal Resource Productivity and Sea‐Level Change: The Role of Physical Sedimentary Processes in Assessing the Archaeological Potential of Submerged Landscapes from the Northwest Australian Continental Shelf

Existing models of coastal occupation, in one form or another, embrace the assumption that changes in mean sea level were the prime driver for shifts in coastal resource productivity of consequence to coastal foragers. Focusing on the North West Shelf of Australia, this paper considers the role of physical sedimentary processes in understanding both past coastal resource productivity and the archaeology of drowned coastal landscapes. From a review of up‐to‐date literature on sea‐level related coastal formation process related to the North West Shelf, we describe the complex interplay of sea‐level change and sedimentary processes in determining (i) coastal resource availability, and (ii) archaeological site preservation potential through time. We argue that human behavioral models that have been linked solely to changes in sea level change from ca. 45 ka onward along the Australia continental shelf have inadequately accounted for local sedimentary regimes. It is not past sea‐level per se, which is of relevance to coastal productivity and human behavioral ecology models but changes in tidal regimes, coastal configurations and sedimentation. We conclude that our understanding of maritime adaptations for Sahul (Greater Australia) remain incomplete without investigating former coastlines and archaeological information that now lies submerged offshore.