Although the Euphrates River-stretching similar to 3,000 km across Western Asia-has shaped the region's geology for millions of years, the timing of its origin and the evolution of its course remain enigmatic. So far, two contrasting hypotheses have been proposed to explain the fluvial system's Late Neogene path: termination in Anatolia at a palaeo-lake or the Mediterranean, or a southeastward continuation to Arabia. Here we use seismic-reflection and topographic data to show that two previously identified sedimentary accumulations-deposited during the terminal phase of the Late Miocene Messinian salinity crisis-resulted from dual riverine systems that drained into a partially desiccated eastern Mediterranean before avulsing toward the Persian Gulf and converging to form the modern Euphrates River. From probabilistic sediment-budget modelling, we show that although the latest Messinian drainage basins were an order of magnitude smaller than their present-day extents, the total palaeo-discharge exceeded that of the modern Tigris, Euphrates and Nile rivers combined, indicating intense palaeo-precipitation and high palaeo-relief. These results suggest that plate-margin deformation both controlled the fluvial avulsions that diverted the Euphrates River from the Anatolian-Eurasian Plate to the Arabian Plate, and established the conditions necessary for the development of the alluvial Fertile Crescent.

The seismically active Australian North West Shelf (NWS) hosts a 170 km-long carbonate platform in the Exmouth Sub-basin, where Cenozoic mass-transport complexes (MTCs) provide a valuable opportunity to investigate slope failure processes in carbonate-dominated margins, which remain underrepresented in global datasets largely derived from siliciclastic systems. Using a high-resolution 3D seismic dataset covering 11,731 km2, interpreted through full-volume seismic interpretation workflows and calibrated to the Ravensworth 1/CH1 well, we establish a high-resolution seismic stratigraphic framework and map in detail four MTCs ranging from 40 to 185 km3 in volume. Geomorphological and quantitative analysis reveals a down-slope continuum of deformation along basal shear surfaces, transitioning from coherent slide blocks up to 3.3 km long near the headscarps to rafted blocks and ultimately amorphous debris flows. Run-out distances of 11 to 80 km are controlled by paleotopography and rheology, highlighting the importance of substrate properties in governing MTC evolution and architectural maturity. Spatial relationships between faulting and headscarps, locally hardlinked to underlying faults, indicate that tectonic processes constitute a key triggering mechanism, while retrogressive failure features suggest on-going slope instability associated with present-day seismicity. Overall, the timing of MTC development reflects the interplay of tectonic and climatic controls, with major failure events coinciding with periods of intensified regional structural activity. These MTCs are associated with proto-slumps, crown cracks, and pockmarks, which in turn can increase slope instability in the future (i.e., development of new MTCs) and represent a significant geohazard risk. Quantitative morphometric relationships demonstrate that these MTCs are broadly comparable to passive margin-attached MTCs globally, including carbonate systems such as the Great Bahama Bank. However, observed differences with global trends infer that the variability of carbonate lithologies (i.e., diverse rheological properties) constitutes a key control parameter on MTC dimensions. By providing a detailed morphometric analysis of MTCs along a carbonate margin, this study helps address a bias in current global databases and offers new hypotheses for evaluating the transferability of slope failure models between siliciclastic and carbonate systems. These results improve our understanding of how sediments are redistributed along carbonate slopes and how the interaction between structural inheritance, sedimentary processes and external forcing governs slope failure on continental margins, with implications for basin evolution and geohazard assessment, which ultimately can help the prediction of MTC occurrence and behavior in analogous settings worldwide.

This article presents a national seismic-derived bathymetric compilation based on the integration of 253 3D seismic surveys. Individual surveys were combined to produce four regional compilations covering an area of 267,000 km2, with a spatial resolution of 30 × 30 m and a vertical accuracy of 5 m + 5%d. The production of the dataset is based on the integration of seismic survey first returns with seismic vessel echosounder measurements. Following the extraction of the depth soundings, all data points were converted from time to depth using synthetic velocity profiles and filtered to remove erroneous records. The seismic survey’s first returns were corrected using navigation depth soundings to account for geometric distortions. All depth values were reduced to WGS84 and EGM2008 datum. A comparison of the seismic-derived bathymetry with multibeam echosounder surveys suggests that where a thin layer of loose sediments overlies a lithified substratum, the seismic first return captures the top of the substratum.

Key Messages: (1) Isolated carbonate build-ups of the Vulcan sub-basin were initiated during the MIS16-MIS15 transition and recorded 5th order eustatic fluctuations. (2) Mass transport complex internal architecture and run-out distance are likely controlled by lithology and slope gradient. (3) Active tectonics between the Australian and Timor plates played a key role as a triggering mechanism.

While it is accepted deep-water sand delivery is most efficient during periods of relative sea-level fall and lowstand, other parameters (e.g., sediment supply, hydrodynamic regime) can also influence when, where and how these sands are bypassed. In this context, it is critical to understand how tectonic and climatic settings modulate those parameters and impact shelf-to-basin sediment transfers. Availability of high-resolution and extensive 3D seismic data in the Porcupine Basin offers a unique opportunity to study the evolution of shelf-margin clinoforms developed during the Paleogene in a failed rift basin under greenhouse climatic conditions. Using advanced full-volume seismic interpretation methods, the Quantitative 3D Seismic Stratigraphy (QSS) approach is used to identify fifteen clinothems prograding over a period of similar to 20.4 Myr during the Late Paleocene-Mid Eocene. Overall, the shelf margin presents low progradation rates and is developed under low rates of sediment supply. It appears that increasing fluvial influence along paleoshorelines developed at the shelf edge promotes deep-water sand delivery, which is consistent with previous published studies along other margins. The QSS analysis reveals that steeper clinoform slope gradients are associated with wave-dominated shorelines, whereas more gentle slope gradients are associated with fluvial-dominated shorelines. These results present opposite relationships to what is described in the literature, hence it is interpreted that in the absence of high sediment supply, the inherited rift topography (i.e., structural inheritance) controlled the shelf-margin architecture and its physiography by superseding relationships typically observed in other types of shelf margins. This study demonstrates the critical roles of sediment supply and inherited paleotopography in post-rift basins on shelf-margin architecture and associated sediment transfer mechanisms.

Key Messages: (1) Mass-transport complexes (MTCs) developed in the Exmouth Sub-basin exhibit a continuum of downslope deformation along basal shear surfaces that coincide with third-order sequence boundaries. (2) Fault reactivation is a likely trigger for slope failure in several MTCs as suggested by the direct link observed between headscarps and underlying faults. (3) Variations in run-out distance (11–80 km), likely influenced by paleotopography and rheology, affect the architectural maturity of the MTCs, which are morphometrically comparable to other passive margin-attached systems in carbonate settings.

Understanding the primary drivers of lateral and vertical variability in the stratal architecture of shelf-margin settings is key to understanding how sediments are partitioned from the shelf to the slope and the basin floor in source-to-sink systems. In this study, we model the 4-D evolution of a shelf margin over a period of 18.5 m.y. using Badlands stratigraphic forward modeling software. The modeled system is analogous to the Hammerhead shelf margin developed in the Bight Basin (southern Australian margin) during the Late Cretaceous, with forcing parameters interpreted from "real world" 3-D seismic data. A series of seven models were designed and tested to investigate potential drivers of shelf-margin variability, which include shoreline process regime (i.e., fluvial, wave, or mixed coastal processes), uplift, rainfall, and source area extent. We find that shoreline processes, which in the context of this study include fluvial and wave processes, may significantly impact shelf-margin architecture although they are less likely to affect the longterm evolution of a shelf margin. The addition of either fluvial or wave processes increases along-strike lateral variability with mixedprocess shorelines resulting in the most variability. We propose that these hydrodynamic processes affect sediment supply locally leading to "out-of-phase" supply influencing both shelf-margin architecture and the character of sequence stratigraphic surfaces laterally. Rainfall is also shown to have a much more immediate effect on shelf-margin architecture compared to changes in tectonics (uplift). The results of this study are particularly applicable to the Hammerhead shelf margin and

When producing reservoirs in fluvial deposits, it is notoriously difficult to define pore volumes connected to completed well intervals from sparse subsurface data. It is equally difficult to forecast production behaviours like initial delivery rates and long-term drawdown curves. These prediction challenges reflect the wide variety of potential fluvial reservoir geometries, from isolated narrow shoestring sands to broad labyrinth sheets, and complex patterns of intra-reservoir heterogeneities. Improved subsurface predictions require detailed characterization of the fluvial system to define the scale and magnitude of grain size variations across a hierarchy of depositional scales. A fluvial reservoir architecture classification is used to improve subsurface characterization and is applied to the Triassic Mungaroo Formation, Northwest Shelf, Australia. Integration of a substantial database of 3D seismic and records from hundreds of well penetrations provides an exceptional opportunity to characterise a large fluvial system across the full hierarchy of scales from source to sink. The fluvial hierarchy and channel-belt classification, developed specifically to aid in subsurface modelling of fluvial systems, was partially created and tested using observations from the Mungaroo Formation. The fluvial hierarchy is defined as having progressively larger-scale depositional units termed: 1) Bed, 2) Bed set & Storey, 3) Element, 4) Complex, and 5) System. A channel-belt element is the typical subsurface modelling object composed of an amalgamation of channel bar and abandonment fill deposits (storeys) formed between episodes of river avulsion. Channel-belt elements are classified into four different channel-belt types with decreasing stream power: A to D. A-type channel-belts are high powered and dominated by downstream accretion deposits. B-type belts are moderately powered and feature a mix of down and lateral accretion deposits. C-type belts are moderately-low powered and dominated by lateral accretion deposits. D-type belts are low- to very-low-powered and feature oblique to downstream accretion deposition. High-quality 3D seismic data covering large parts of the basin allowed the mapping and interpretation of individual channel-belts over hundreds of kilometres in length to document downstream changes. Integration of seismic, core and well logs allow measurements of channel-belt width, thickness, and channel-belt edge rugosity geometry to estimate river bend wavelength. Mungaroo Formation C-type and D-type channel-belts average 1100 m wide (ranging from 150 to 3000 m) and 22 m thick (ranging from 5 to 68 m), which indicates these deposits formed in very large rivers. Along individual stratigraphic intervals, thicker, wider channel-belts with longer edge rugosity wavelength in the proximal part of the system pass down depositional dip into narrower, thinner, and lower wavelength rugosity belts. These spatial changes in channel-belt geometry are used to define changes in the fluvial system across a broad fluvial distributary system spanning hundreds of kilometres, including the branching of the trunk river into smaller distributaries that are typical of a distributive fluvial system. Channel-belt scaling relationships and detrital zircon provenance data indicate a continental-scale fluvial catchment comparable in size to large-discharge modern coastal systems like the Mississippi, Orinoco, and Parana rivers. The interpretation of the Mungaroo Formation as a large, low-gradient distributive river system, has significant reservoir modelling and hydrocarbon production implications.

Shelf margins represent a crucial area along source-to-sink systems where sediments are partitioned from the shelf to slope and basin-floor areas. Reconstructing the evolution of these depositional systems is key for interpreting the interplay between past accommodation and sediment supply, and sediment dispersal mechanisms into deep water. In the Bight Basin, on the southern margin of Australia, the Hammerhead shelf margin prograded during the Late Cretaceous following break-up between Australia and Antarctica. This understudied interval offers important insights into source-to-sink processes in a post-rift, greenhouse, high sediment supply setting. A dynamic stratigraphic approach using high-resolution 3D seismic data across the Hammerhead shelf margin has been used to quantitatively characterise 28 clinothems developed over 1.9 Myrs each with an average duration of 67,000 years. By applying a shallow-marine process-based classification to shorelines, alongside quantitative analysis of the architecture of their coeval deep-water deposits downdip, statistical relationships and clear links between shallow-marine processes, stratigraphic architecture, and deep-water sand delivery are revealed. A statistically significant relationship between fluvial dominated shorelines, high slope gradients, and mass-transport deposit development is demonstrated, as is a requirement for fluvial influence at the shoreline for the initiation of long run-out turbidite systems. These long run-out turbidite systems are interpreted to have been formed by repeated density flows which lead to greater sediment transfer efficiency and increased sediment supply. This research has direct application to improve prediction of reservoir locations within the Bight Basin for resource exploration and/or carbon sequestration and may also be applied to improve deep-water sediment predictability in other basins worldwide developed in similar tectonic and climatic settings. (c) 2024 The Author(s). Published by Elsevier B.V. on behalf of International Association for Gondwana Research. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/ 4.0/).

Faults can fundamentally change a groundwater flow regime and represent a major source of uncertainty in groundwater studies. Much research has been devoted to uncertainty around their location and their barrier-conduit behavior. However, fault timing is one aspect of fault uncertainty that appears to be somewhat overlooked. Many faulted models feature consistent layer offsets, thereby presuming that block faulting has occurred recently and almost instantaneously. Additionally, barrier and/or conduit behavior is often shown to extend vertically through all layers when a fault may in fact terminate well below-ground surface. In this study, we create three plausible geological interpretations for a transect in the Perth Basin. Adjacent boreholes show stratigraphic offsets and thickening which indicate faulting; however, fault timing is unknown. Flow modeling demonstrates that the model with the most recent faulting shows profoundly different flow patterns due to aquifer juxtaposition. Additionally, multiple realizations with stochastically generated parameter sets for layer, fault core, and fault damage zone conductivity show that fault timing influences flow more than layer or fault zone conductivity. Finally, fault conduit behavior that penetrates aquitards has significant implications for transport, while fault barrier behavior has surprisingly little. This research advocates for adequate data collection where faults may cause breaches in aquitards due to layer offsets or conduit behavior in the damage zone. It also promotes the use of multiple geological models to address structural uncertainty, and highlights some of the hurdles in doing so such as computational expense and the availability of seamless geological-flow modeling workflows.

North and South Scott Reefs are isolated carbonate platforms separated by an inter-reef channel on the NWS, Australia. They evolved from a carbonate platform in the Miocene, and into isolated carbonate build-ups (ICB’s) in the Pliocene, and finally to the isolated carbonate platforms that continued to present day. However, the timings of coral reef turn on and off are insufficiently understood with respect to global climatic changes in this region. The North West Shelf (NWS) of Australia endured dramatic climatic and oceanographic changes throughout the Cenozoic. Most remarkably: (1) the Mid Miocene Climatic Optimum (MMCO), which saw the onset of ICB’s and carbonate platform development; (2) the Mid Pleistocene Transition (MPT) (ca. 0.8-0.6 Ma) and the associated change in regional climate from wet to dry; and (3) glacial-interglacial variability throughout the Pleistocene until present day. Availability of high resolution and extensive 3D seismic data provides a unique opportunity to investigate the evolution of these reefs using the principles of seismic stratigraphy and seismic geomorphology. Four main phases of carbonate factory (Phase I-IV) were identified from the Miocene to present. And for the first time, it was possible to reconstruct a chrono-stratigraphic framework, detailing relative sea-level (RSL) changes and the impact of global (e.g., climate, eustasy) and local (e.g., tectonics) forcing parameters on their development. Seismic stratigraphy reveals that despite rapid accommodation rate changes, the unique oceanographic setting, antecedent topography and rapid vertical reef accretion played a key role in the endurance of Scott Reefs. It is likely that the Indonesian throughflow (ITF) current has been a critical component in controlling the local climate. The Leeuwin current, tides, swells and wind regimes similarly exert a major influence on the NWS climate, whilst the inter-reef channel likely bypassed terrigenous sediment influx away from the reefs, avoiding periods of inundation during wet climates.

The Rowley Shelf, the southern half of the tropical, carbonate-dominated, North West Shelf of Australia, is covered with linear ridges that can be tracked parallel to the coast over 1100 km between the modern coast and the 140 m isobath. Here, we investigate the origin and nature of these ridges based on the integration of extensive borehole data, high-resolution geophysical data, age dating and compaction analysis.Our investigation reveals that each ridge consists of now-submerged relict coastal deposits that were formed over the last 200,000 years through wave, tidal, fluvial and aeolian processes. These features were dominantly preserved through early diagenesis and illustrate the longest continuous submerged palaeoshorelines reported to date.The distribution of relict coastal features, and therefore early diagenesis, controls the morphology of the continental shelf. First, relict coastal features tend to be stacked on top of each other, resulting in the formation of composite diachronous coastal deposits that form distinctive steps on the seabed, up to 10s m high. Second, relict coastal features form a hard substrate that controls the location of coral reefs along the shelf. Reefs, including a 20-m-thick MIS 3 drowned coral reef described here for the first time, as well as modern reefs of the Muiron Islands, Montebello Islands and Dampier Archipelago, are all developed on top of relict coastal features.The distribution, size and mineralogy of relict coastal features highlight climatic changes along the Rowley Shelf. High relative sea levels (RSL) are associated with low carbonate production and up to 50% of terrigenous grains, while low RSL deposits exhibit increased carbonate production and reduced terrigenous grain content. This asymmetry is interpreted to reflect the onset of the monsoon associated with increased fluvial runoffs during interglacial periods.Lastly, our work shows that compaction analyses are critical for palaeoenvironment and RSL reconstructions. Indeed, the accumulation of 50 m of sediment on a RSL indicator can result in an offset of the measurement by 12.7 m.& COPY; 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Understanding the stratigraphic architecture of shelf-margin clinoforms is key to determining how sediments are transferred to deep-water settings and how the interplay of tectonics (subsidence/uplift), eustasy and variations in sediment supply rates and calibre, impacts deep-water sand delivery. Here, clinothems are used to establish quantitative relationships between shelf-margin architecture and shelf-to-basin sediment transfer. In the Bight Basin on the southern margin of Australia, the Hammerhead shelf margin prograded during the Late Cretaceous, following continental break-up from Antarctica. This understudied interval offers an opportunity to investigate controls on shelf-margin architecture during the early post-rift phase. Interpretation of integrated data (2D and 3D seismic reflection, and well data) has been completed using full-volume interpretation software (PaleoScan©), allowing for the first full high-resolution 3D interpretation of this interval. Quantitative analyses of clinoform geometry are used to calculate several parameters (e.g., shelf-edge trajectory angle, progradation rate, aggradation rate) within sixteen 3rd order seismic sequences mapped across the basin. This study increases our understanding of source-to-sink systems in extensional settings via this quantification of shelf margin clinoforms. Overall, four discrete phases of Hammerhead shelf margin evolution are identified with lateral variations in sediment supply proposed to be the main driver of shelf-margin variability. Through time, the evolution of the accommodation and sediment supply rates (i.e., A/S ratio) suggests that after a major flooding event, the initial high sediment supply rates become progressively lower as shelf accommodation creation increases due to thermal subsidence, leading to an overall progradational to aggradational stacking pattern, with final backstepping of the shelf margin. Quantitative results show that a variety of factors influenced the delivery of sediments to deep-water areas (e.g., clinoform slope gradient, slope relief, faulting and lateral sediment transport) and that shelf-edge trajectory angle cannot be used solely to predict sediment partitioning. This research improves understanding of sediment partitioning and the development of shelf margins in post-rift tectonic settings and by investigating the Hammerhead shelf margin, the timing of tectonic events and dynamics of Gondwanan break-up have been refined.

Onshore and offshore site investigations along the dryland tide-dominated De Grey River delta (northwestern Australia) led to the unexpected discovery of the largest yet-known ma-rine ooid shoals in the Indo-Pacific region. Ooids exhibit up to 60 tangential aragonitic lami-nae that were formed around fluvial sediment grains during the late Holocene. Covering an area >1250 km2, their spatial extent rivals in size individual ooid shoals from the Bahamas. Shoals appear to be spatially linked with the De Grey River, suggesting that fluvial outputs, combined with a macrotidal range, facilitated the precipitation of the ooids. Following their formation, ooids were reworked through tidal and wave processes along the delta. As a re-sult, the delta sedimentary features, including beach ridges, mouth bars, and distributary channels, are composed of ooids. This discovery broadens the range of depositional and climatic environments in which ooids can form and demonstrates that fluvial runoff may not inhibit aragonite precipitation. Such a configuration also provides a unique analogue for ancient ooids found in association with siliciclastic grains and further indicates that the interpretation of typical siliciclastic geomorphologies from geophysical data does not preclude the presence of carbonate grains.

Linear buildups formed in tropical carbonate environments are often interpreted as bioconstructed reefs. Nevertheless, coastal processes can also form extensive sedimentary ridges exhibiting buildup morphologies. This study investigates two Miocene ridges developed along the Australian North West Shelf using 3D seismic and well data. Ridge 1 is ca. 30 m thick and >60 km long, and it is made of foraminiferal pack‐grainstones. It protects a lagoon with pinnacle morphologies. Ridge 2 is ca. 150 m thick and >80 km long. It is composed of quartz sand forming lobes. Both ridges have a continuous curvilinear front and are in a mid‐shelf setting. They mimic the modern Australian coastline. It is then proposed that Ridge 1 is either: (1) a barrier reef developed on a drowned shoreline, or (2) stacked carbonate aeolianites and beachrocks acting as a barrier. Ridge 2 is interpreted as stacked deltaic sands. This study demonstrates that lithified and buried coastal features of carbonate and siliciclastic nature can form extensive ridges exhibiting buildup morphologies. It is proposed that ridges formed by stacked coastal features are overall continuous with a curvilinear front, while reefal ridges are more discontinuous and exhibit deeper and more stable passes.

The Early Cretaceous palynological successions record one of the earliest waves of angiosperm radiation in several low-latitude localities, including the Arabian Plate. The palynological analysis of 59 core and cuttings samples from the late Barremian-early Aptian Biyadh and Shu'aiba formations, offshore Saudi Arabia, reveals remarkably high angiosperm diversity. These Early Cretaceous angiosperms inhabited northeastern Gondwana together with a diverse flora that also included bryophytes, lycopodiopsids, ferns, conifers, and other gymno-sperms. A review of the dispersal capacity of this Gondwanan flora suggests that most mainland taxa had potentially colonized the carbonate islands and island arc archipelagos on both sides of the Neotethys Ocean.Two models are postulated to explain the late Barremian-early Aptian radiation of angiosperms. During sea -level lows, angiosperms would be easily dispersed to carbonate islands contiguous to northeastern Gondwana. Early birds and flying reptiles acted as the main dispersal agents for the early flowering plants, together with a diverse set of abiotic factors. The sub-aerial exposures of oceanic seamounts would serve as stepping-stones for early birds and flying reptiles, allowing a two-way dispersal of angiosperm propagules to distant volcanic islands. During sea-level highs, angiosperm gene flow between the mainland pool and the island inhabitants would be severely impeded because of the drowning of the coastal regions, many carbonate islands, and seamounts, thus promoting insular allopatric speciation and adaptive radiation. During these periods of geographical isolation, the remaining emergent Neotethyan archipelagos would act as 'insular centers of diversification' generating angiosperm island endemics, which in turn would be dispersed to the mainland during the following sea-level lows. Additionally, the gene flow of early aquatic angiosperms colonizing the scattered water bodies on north-eastern Gondwanan wetlands would be limited during sea-level lows, turning these sites into 'wet centers of diversification'.