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The Qom Formation is the most important hydrocarbon reservoir target in Central Iran. The Qom platform developed in a back‐arc basin during the Oligo–Miocene due to the closing of the Tethyan Seaway. This formation consists of a variety of carbonate and non‐carbonate facies deposited on a platform ranging from supratidal to basin. A combination of tectonic and eustatic events led to some lateral and vertical facies variations in the study area. Six third‐order depositional sequences and related surfaces were identified regarding vertical facies changes in the studied sections of this Oligo–Miocene succession. According to all results and data, this succession was initially deposited during the Chattian upon a distally steepened ramp of siliciclastic‐carbonate composition, including the Bouma sequence. Then, from the late Chattian to the Aquitanian, the platform changed into a homoclinal carbonate ramp with a gentle profile. With respect to tectonic activity, this phase was a calm period during the deposition of the Qom Formation. Finally, a drowned carbonate platform and a rimmed shelf emerged during the Burdigalian, terminated by the continental deposits of the Upper Red Formation. Regarding all geological characteristics, three main tectono‐eustatic evolutionary phases have been recognized in the Qom back‐arc basin. [ABSTRACT FROM AUTHOR]

The deposits of the upper Neoproterozoic Zerrissene Group of central‐western Namibia represent a large siliciclastic deep‐water depositional system that showcases the intricacies of facies and architectural relationships from bed‐scale to fan‐system‐scale. The lack of vegetation in the Namib Desert and regular east–west repetition of folded stratigraphy (reflecting ca 50% tectonic shortening) provides quasi‐three‐dimensional exposure over a current area of approximately 2700 square kilometres. The Brak River Formation, the middle sand‐rich unit of the Zerrissene Group, consists of nearly 600 m of strata exposed in multiple parallel continuous outcrops up to ca 10 km in length and oriented obliquely to depositional dip. Ten stratigraphic sections are correlated ca 32 km (ca 64 km restored) across the basin and offer exposure comparable in scale to modern submarine fans. Six sedimentary facies are identified and grouped into four facies associations that represent axial‐to‐marginal portions of deep‐water lobes in an unconfined submarine fan system. Spatial facies patterns, regional thickness variations, and palaeocurrents indicate that Brak River Formation sediments were transported primarily from the north to south–south‐west through a trough‐like basin, and deposited within an unconfined basin plain at the junction of the Adamastor and Khomas oceans. The unique outcrop exposure and extent permits the documentation of system‐scale architecture and basin configuration of the Brak River submarine fan system. A transition from the sand‐rich lower Brak River Formation to more intercalated mudstone‐dominated intervals in the middle and upper Brak River Formation is interpreted to record a change from aggradational to compensational stacking of lobe deposits. This records the evolution of a large submarine fan as it filled the subtle seafloor topography and became less confined at the system‐scale. The documentation of these deep‐water deposits from centimetre‐scale to basin‐scale provides a new model for a system with extensive long‐distance transport of sand‐rich sediment gravity flows to submarine lobes without apparent channelization. [ABSTRACT FROM AUTHOR]

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Hybrid event beds (HEBs) record disequilibrium in submarine fan evolution attributed to mud-forced dampening turbulence, which could be caused by allogenic and autogenic forcings in either the proximal or distal segment of a lobe-dominated submarine fan on several timescales. Detailed field investigation combined with petrographic and mineralogical analysis of selected outcrop samples indicate that the Upper Triassic submarine fan succession mainly comprises turbidites, HEBs, and debrites in the West Qinling (WQ) area of NE Tibetan Plateau. Five types of HEBs are recognized based on the thickness, sedimentary structure, and texture. Bed-by-bed description and measurement reveal that these HEBs show a distinct distribution pattern throughout the submarine fan succession, including dominance of HEB-1 and HEB-2 beds (∼71.50%) in distributary channel to lobe off-axis (FA1–FA3) and significant portion of HEB-3 to HEB-5 beds (∼54.22%) in lobe fringe to lobe distal fringe environments (FA4–FA5). Textural and petrographic characteristics of mudclasts suggest disaggregation of heterolithic, homogenous and less cohesive mudclasts (MC-1 to MC-4 type) within H1b and H3 interval of HEBs, which could play different roles in the longitudinal mud-driven flow transformation between turbulent and laminar flow behavior patterns. The vertical distributions of the HEB-prone succession are characterized by four types of depositional scenarios, which yields significant allogenic and autogenic signatures combined with the recognition of the dominant HEB types and thickening- or thinning-upward trend of the vertically stacked submarine lobes. This study can enhance our understandings of flow transformation of sediment gravity flows (SGF) along the eastern margin of the Paleo-Tethys Ocean based on the anatomy of several undiscovered deep-water outcrops, which were reflected by the initiation, gradual switching, and avulsion of the high-frequency submarine fan evolution during the Late Triassic. • HEBs are well developed both in proximal and distal parts of the submarine fan. • Various types of mudclasts play different roles in the mud-driven transformation. • Vertical distribution of HEBs records high-frequency change in the submarine fan. [ABSTRACT FROM AUTHOR]

Analysis of tectonic-sedimentary setting and facies based on cores and well logging shows that Lower Devonian F4 unit is submarine fan that can be divided into two cycles by correlating a fan-wide marine mud datum named middle mud. The association of lithofacies forms five facies, including slump, braided channel complex and depositional channel, channel-distal lobe, turbidity-sheet sand, and hemipelagic deposits. Mapping intrafan units reveals an aggradational–retrogradational stacking pattern of the F4 unit, which is a multiple point source sand-rich fan who supplied from northwest, southeast, and south. This study provides not only correlation strategy, but also a reliable geological model for the further development of F4 unit. [ABSTRACT FROM AUTHOR]

The uppermost Quaternary deposits of the Hueneme and Dume submarine fans in the Santa Monica Basin have been investigated using a closed-spaced grid of boomer seismic-reflection profiles, which give vertical resolution of a few tens of centimetres with acoustic penetration to 50 m. Acoustic facies integrated with geometry define six architectural elements, some with discrete subelements that are of a scale that can be recognized in outcrops of ancient turbidite systems. In the Santa Monica Basin, the relationship of these elements to fan morphology, stratigraphy and sediment source is precisely known. The width of upper Hueneme fan valley has been reduced from 5 km since the last glacial maximum to 1 km at present by construction of laterally confined sandy levees within the main valley. The middle fan comprises three main subelements: thick sand deposits at the termination of the fan valley, low-gradient sandy lobes typically 5 km long and < 10 m thick, and scoured lobes formed of alternating sand and mud beds with many erosional depressions. The site of thickest lobe sediment accumulation shifts through time, with each sand bed deposited in a previous bathymetric low (i.e. compensation cycles). The lower fan and basin plain consists of sheet-like alternations of sand and mud with shallow channels and lenses. Variations in the rate of late Quaternary sea level rise initiated changes in sediment facies distribution. At lowstand, and during the approximately 11 ka stillstand in sea level, the Hueneme Fan was fed largely by hyperpycnal flow from the Santa Clara River delta, depositing high sediment waves on the right hand levee and thick sandy lobes on the middle fan. At highstand of sea level, most turbidity currents were generated by failure of silty prodelta muds. In contrast, the smaller Dume Fan was apparently always fed from littoral drift of sand through a single-canyon point source. [ABSTRACT FROM AUTHOR]