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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]

The submarine fan with a narrow shelf is usually reactive to environmental signal propagation; however, source-to-sink functioning can be further complicated by several allogenic forcings. Here, we document the high-frequency provenance variations and different sediment delivery models recorded in the late Triassic Zhuoni fan developed in the northeastern Paleo-Tethys Ocean, mainly based on process-based sedimentological and provenance study of the Panyuan section in the West Qinling area in the northeastern margin of Tibetan Plateau. High-, low-density turbidites, hybrid event beds and hyperpycnites are distributed in the lobe-dominated submarine fan succession. Field sedimentological evidence from surrounding outcrops suggests that shelf-edge failure was the main cause of most high-and low-density turbidites with the overall absence of submarine slides or slumps, whereas the narrow shelf configuration together with late Triassic humid pulses is favourable for the occurrence of flood-related hyperpycnites in the Zhuoni fan. Detrital zircon grains (N = 6; n=123-272) generally have Palaeozoic-Mesozoic ages (ca. 350-250 Ma and 500-400 Ma) and Neoarchean-Paleoproterozoic ages (ca. 2100-1750 Ma and 2600-2400 Ma), but they can be further categized into three age groups due to different proportions of Precambrian age populations. The results demonstrate that the potential source areas may include the South and North Qinling Orogenic Belt, Qilian Orogenic Belt, different segments of North China Craton and the tectonic junction area between the Qinling and Qilian Orogenic Belts. The temporal changes in provenance signals, which are reflected by both the detrital zircon age spectra and heavy mineral assemblages, indicate different contributions of those sources in response to sea-level fluctuation. It could thus give rise to temporal variations between reactive and buffered source-to-sink sediment delivery models of the Zhuoni fan, despite the overall narrow shelf configuration. The development of the lowstand Zhuoni fan was directly related to extrabasinal hyperpycnal delivery from the river mouth and its high-frequency provenance variability recorded different efficiencies of signal transfer through the onshore catchment with significantly influence of temporal storage, fluvial rejuvenation or even regional climate variability. The highstand submarine fan was thought to be formed by shelf-edge failure with sediment buffering in the shelf region, which was associated with a strong magnitude of provenance mixing. Our work provides a new perspective for deciphering the different origins of deep-water sediment delivery in response to high-frequency sea-level and climate changes. [ABSTRACT FROM AUTHOR]

The Tertiary-age deep-marine succession cropping out between Tarifa and Algeciras can be subdivided into two units, namely the Late Eocene-?Early Oligocene Getares Unit and the overlying Oligocene-?Early Miocene Algeciras Formation. These strata comprise six sedimentary facies, ranging from thick-bedded sandstones to mudstones. The depositional settings are variable, comprising sandstone/calcarenite packages with intercalated mudstones and marls. The lowermost coarse-grained package is the Getares Unit (fan-fringe setting). This is overlain by the thick-bedded sandstones of the Algeciras Fm (channel, channel-margin setting) which pass upwards into more laterally-extensive beds (sheet-like lobe). Sediments were derived from a coastal setting to the north, as evidenced by occasionally abundant plant remains, from direct fluvial input (hyperpycnal flow). Within this succession, 34 ichnogenera (48 ichnospecies) have been recorded, including, Belorhaphe, Capodistria, Chondrites, Circulichnis, Cochlichnus, Cosmorhaphe, Desmograpton, Gordia, Halopoa, ?Helicorhaphe, Helminthopsis, Helminthorhaphe, Imponoglyphus, Lorenzinia, Megagrapton, Oldhamia, Ophiomorpha, Palaeophycus, Paleodictyon, ?Phycodes, Phycosiphon, Planolites, Protopaleodictyon, Protovirgularia, Scolicia, Skolithos, Spirophycus, Spirophyton, Spirohaphe, Taenidium, Teichichnus, Thalassinoides Urohelminthoida and Zoophycos. Of the ichnofossil assemblages that were defined, most are concentrated in the fan-fringe (Getares Unit; 74%) and channel/channel-margin (lowermost Algeciras Fm; 41%) settings, with a marked reduction in the sheet lobe system (uppermost Algeciras Fm; 9%). The ichnofaunal assemblage from the Tarifa-Almeria section represents the Nereites ichnofacies, or more specifically, the Paleodictyon and Nereites subichnofacies, both typified by abundant graphoglyptids. Deposition in the Algeciras-Tarifa region commenced with the mudstones underlying the Getares Unit followed by a sandstone package (fan fringe; Punta de Getares), indicative of fan progradation. Subsequent mudstones suggest a phase of quiescence before the deposition of the thick, sandy hyperpycnites in the lower part of the Algeciras Fm (Punta del Carnero I & II) where deposition was probably related to flooding events in the source rivers to the N. These were subsequently overlain by the Tarifa area lobe sediments. Deposition of the succession coincided with the transition from a Greenhouse to an Icehouse climatic regime (Eocene-Oligocene) and this change may be reflected in the marked reduction in ichnofaunas moving from the lower (Punta del Carnero) to the upper (Tarifa) Algeciras Fm. [ABSTRACT FROM AUTHOR]

Fractionation of particles in deep‐water sediment gravity flows is an important factor in the resulting deposit and for discriminating sedimentary environments, but remains poorly understood. Quantitative characterization of particle shape was performed for more than ten‐thousand particles of experimental gravity flow experiments (both of cohesive and non‐cohesive nature) made using coal and kaolin particles. Eleven particle shape parameters were calculated and their distribution and trends within the experimental basin were evaluated. Results indicate the existence of non‐normal distributions and observable correlations between particle shape parameters. Shape parameters such as circularity and roundness are dominant controls on shape variation. Strong correlations exist between mean shape parameters and along‐flow distance from the source for particles in non‐cohesive flow experiments. Important differences were observed between shape parameter distributions of particles sampled at different areas within the experimental basin, which can be grouped based on their depositional setting (proximal or distal) using multivariate statistical analysis, especially for the non‐cohesive flow experiments. A tendency for more elongated and irregularly‐shaped particles at the more distal and marginal areas of the studied experimental basin was observed and validated by previous field studies in real‐world deep‐marine deposits. Besides, fractionation of particles is less‐pronounced in cohesive flows compared with non‐cohesive ones suggesting the soundness of discrimination of depositional settings based solely on particle shape characteristics is strongly dependent on parent flow characteristics. Yet, results highlight the potential of particle shape analysis in revealing spatial particle shape trends due to hydrodynamic fractionation and discriminating different depositional settings within submarine fans. This methodology may be applied to seafloor and subsurface samples to help identify the flow process and depositional environment. [ABSTRACT FROM AUTHOR]

Highlights: [•] Submarine fan stratigraphy can be analysed by autogene and allogene responses. [•] Auto-cycle expresses as a sequence of slumps, debrites, densites, and turbidites. [•] Stacking auto-cycles of fan progradating or retrograding forms allo-cycle. [•] Seismic stratigraphy is effective for genetic stratigraphy of submarine fan. [Copyright &y& Elsevier]

Abstract: The Cretaceous to Eocene aged Basque Basin in northern Spain preserves a variety of submarine fan related environments of deposition in well exposed outcrops. Here, quantitative trace fossil data is calibrated to sedimentologically defined environments of deposition. Nine environments of deposition are assigned according to sedimentary facies associations, depositional architecture and stratigraphic context. The preserved trace fossil assemblages are interpreted in terms of extrinsic palaeoecological, and intrinsic taphonomical and depositional environment controls. In channel related environments, diverse pre-depositional dominated assemblages are prevalent in marginal settings. These are replaced by low diversity post-depositional dominated assemblages in more axial positions within the system. Lobe related environments display a higher level of diversity and bioturbation intensity in more distal/off axis (lobe fringe) environments compared to the most axial lobe environments that preserve low diversity, and exclusively post-depositional assemblages (dominated by Ophiomorpha). Diverse pre- and post-depositional assemblages are common in fan fringe deposits, with less diverse assemblages dominated by post-depositional ichnotaxa (particularly Zoophycos) in basin floor fan deposits. The use of ‘sub-ichnofacies’ is found to only aid characterisation of trace fossil assemblages based on a general (proximal–distal) position within a submarine fan system. Tier preservation of trace fossil assemblages is almost exclusively determined by the depth of erosion that a substrate is subjected to. As such, colonisation style (pre- versus post depositional) and ethological groupings are proposed as being the most powerful tool in assisting sedimentological observations in assigning environments of deposition. [Copyright &y& Elsevier]

Abstract: The West Crocker Formation (Oligocene–Early Miocene), NW Borneo, consists of a large (>20 000 km2) submarine fan deposited as part of an accretionary complex. A range of gravity-flow deposits are observed, the most significant of which are mud-poor, massive sandstones interpreted as turbidites and clast-rich, muddy sandstones and sandy mudstones interpreted as debrites. An upward transition from turbidite to debrite is commonly observed, with the contact being either gradational and planar, or sharp and highly erosive. Based on their repeated vertical relationship and the nature of the contact between them, these intervals are interpreted as being deposited from one flow event which consisted of two distinct flow phases: fully turbulent turbidity current and weakly turbulent to laminar debris flow. The associated bed is called a co-genetic turbidite–debrite, with the upper debrite interval termed a linked debrite. Linked debrites are best developed in the non-channellised parts of the fan system, and are absent to poorly-developed in the proximal channel-levee and distal basin floor environments. Due to outcrop limitations, the genesis of linked debrites within the West Crocker Formation is unclear. Based on clast size and type, it seems likely that a weakly turbulent to laminar debris-flow flow phase was present when the flow event entered the basin. A change in flow behaviour may have led to deposition of a sand-rich unit with ‘turbidite’ characteristics, which was subsequently overlain by a mud-rich unit with ‘debrite’ characteristics. Flow transformation may have been enhanced by the disintegration and incorporation into the flow of muddy clasts derived from the upstream channel floor, channel mouth or from channel-levee collapse. Lack of preservation of this debrite in proximal areas may indicate either bypass of this flow phase or that the available outcrops fail to capture the debris flow entry point. Establishing robust sedimentological criteria from a variety of datasets may lead to the increasing recognition of co-genetic turbidite-debrite beds, and an increased appreciation of the importance of bipartite flows in the transport and deposition of sediments in deepwater environments. [Copyright &y& Elsevier]

Recent studies of turbidite bed thickness distributions have demonstrated power-law as well as log-normal statistical distributions. The different distributions may reflect different fan processes and environments and, therefore, could be used as a quantitative method to help identify those environments, including those devoid of sequential patterns. The cumulative distributions of well-known turbidite deposits spanning a range of interpreted fan subenvironments are used to illustrate the potential correlation between cumulative distribution and environments. Assuming that power-law distributions may, for some systems, be the primary input signal, one-dimensional modelling allows semi-quantitative characterization of the effects of different fan processes such as erosion and bed amalgamation. Environments indicative of different fan processes may be characterized based on the degree to which processes have acted as a ‘filter’ to modify the assumed power-law distribution systematically. This model of the effect of fan processes on the power-law distribution is used to help to account for bed thickness distributions observed in several field sites. [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]