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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]

U-Pb ages determined using sensitive high-resolution ion microprobe-reverse geometry on 205 single-grain zircons from 16 ash beds within submarine fan deposits of the Ecca Group provide the first evidence of a marine Permian-Triassic (P-T) boundary in the Karoo Basin of South Africa. These U-Pb ages provide an objective basis for correlating the deep-marine sediments of the southwest Karoo Basin with fluvial-deltaic deposits in the central and eastern parts of the basin where the P-T boundary is recorded in a diverse macrofauna. Furthermore, these new zircon ages and their correlation imply asymmetric subsidence and variable sedimentation rates across the basin.

The Mesozoic evolution of the Andean Cordillera of southern Patagonia is recorded in two formations that are now part of the fold-thrust belt: the Zapata Formation and the Punta Barrosa Formation. Extension in the Ultima Esperanza region began in the Late Jurassic with deposition of the marine volcaniclastic Tobifera Formation and eventually resulted in the full-fledged oceanic Rocas Verdes Basin. The Zapata Formation was deposited over a time span of ~50 m.y. in an irregular basin ultimately bordered by an Early Cretaceous arc to the west. It is characterized by interbedded shale and siltstone mostly deposited in shallow water and, in areas of oceanic crust emplacement, also as deep-water hemipelagic deposits. Sediments of the Zapata Formation were derived initially from local oceanic upwarps and Tobifera highs and later from the andesitic cover of the juvenile arc and/or exhumed oceanic crust. The paucity of sandstone in the Zapata Formation in the Ultima Esperanza region indicates a highly irregular basin partitioned by prominent horsts, with sand deposition confined to sub-basins closer to the arc. Changes in depositional regimes and sediment dispersal patterns related to the onset of Andean contraction and formation of the Magallanes foreland basin are recorded by sediments of the overlying Punta Barrosa Formation. This formation records the evolution of a fold-thrust belt on the basis of the multimodal mineralogical and geochemical character of its sandstone and shale. The presence of an arc is indicated, but nearby Andean metamorphic terranes are more significantly represented in Punta Barrosa sediments. Stratigraphic details across the Zapata and Punta Barrosa Formations indicate that deformation and development of a proto-Andean Cordillera in southern South America was initiated in the late Mesozoic and involved conspicuous crustal shortening. Keywords: Patagonian Andes, orogenic evolution, backarc basin, Magallanes foreland basin, provenance, geochemical modeling.

New sensitive high-resolution ion microprobe-reverse geometry U-Pb detrital zircon data establish the timing of onset of foreland basin subsidence in the Magallanes basin and the age of the Patagonian Andes in southernmost Chile. Initiation of the Magallanes foreland basin is signaled by the abrupt occurrence of sandstone of the Punta Barrosa Formation, loosely dated as upper Albian-Cenomanian from biofacies assemblages. Detrital zircon analyses demonstrate that the Punta Barrosa Formation is not older than 92 [+ or -] 1 Ma and that the linked Andean belt started forming in the Turonian. Keywords: Andean orogeny, foreland basin, SHRIMP-RG data, zircon, Chile.

Research on the depositional record of submarine fans and related turbidite systems has highlighted the importance of channel, lobe and levée–overbank architectural elements as fundamental building blocks. However, many of the characteristics and processes of deposits left by flows traversing those fans remain elusive, because flows seem to be able to go unconfined for long distances. Offshore southern California (USA), the La Jolla Canyon decreases in relief to become an approximately U‐shaped channel across the basin floor of the San Diego Trough. The La Jolla Channel gradually loses confinement and transitions to a network of scours, some of which align to form incipient channels, and fields of bedforms. High‐resolution seafloor topography, CHIRP seismic‐reflection data, sediment cores and hydrodynamic flow analysis are used to explore these features. The focus is on two regions of bedforms: (i) a field of net‐depositional, concentric bedforms across the eastern levée–overbank upstream from the terminus of the La Jolla Channel; and (ii) a linear train of more erosional bedforms approximating an incipient channel adjacent to the present mouth of the La Jolla Channel. These bedforms are interpreted to be among a class of upper‐flow‐regime bedforms called cyclic steps, which were formed by densimetric Froude supercritical turbidity currents that spilled out of the present La Jolla Channel. The high‐resolution data for the La Jolla Fan provide valuable insights into the characteristics of supercritical bedforms likely common to distal submarine fans, as well as on sedimentary processes likely important for submarine fan growth into sedimentary basins. In particular, the pattern of evolution of the La Jolla Fan suggests that cyclic steps with wavelengths on the order of tens of metres to a few hundreds of metres could be fundamentally important for the evolution of the distal submarine fans with relatively low‐relief main channels. [ABSTRACT FROM AUTHOR]