Abstract The Sonar River Valley is centrally located in Madhya Pradesh, flanked by rich Palaeolithic and fossiliferous localities in the Son and Narmada valleys and has historically been overlooked in favour of the latter rivers, which tend to preserve well-stratified Quaternary formations along varying portions of their length. Here an attempt is made to look at the Sonar Basin through a broader lens, examining the various landforms found in the district of Damoh through which the Sonar flows before joining the Ken. The objective of this paper is threefold: to bring together the geomorphology of the area both in association with and as a result of fluvial action but also as a product of other geomorphic processes; to understand the consequences these processes have for the visibility of the prehistoric archaeological record within the region; and to look at this geoarchaeological relationship in the wider context of some of the major river basins in Madhya Pradesh, notably the Son and Narmada. Secondary sources on geology and geoarchaeology have been integrated with preliminary fieldwork in Districts Damoh and Narsinghpur, and to a smaller extent in Sagar, Chhatarpur and Panna. This work demonstrates the complexity of the South Asian Palaeolithic record that stretches beyond fluvial contexts, in turn helping to spatially expand our understanding of hominin behaviour beyond narrow riverine corridors.

The Black Sea basin presents an ideal laboratory for investigations of morphodynamic interplay between response (morphology) and force (processes) associated with shelf sedimentation. Recent studies along the perimeter of the basin have documented the existence of a complex, heterogeneous seafloor varyingly composed of sand, gravel, silt, and clay. Side-scan sonar data are utilized to establish the spatial patterns of bedform types in the area. In addition, a benthic tripod, configured with an acoustic Doppler current profiler, a rotary fanbeam sonar, and a conductivity-temperature sensor was deployed to record seabed dynamics in response to changing forcing conditions. Together, the tripod and side-scan survey data sets provide a complementary basis for deciphering the processes responsible for the observed seafloor morphology. The side-scan sonar data allows for the determination of spatial patterns of bedform length and orientation. In total, 2376 individual large sand wave bedforms were digitized in geographic information systems with mean and modal wavelengths of 72.8 and 15.7 m respectively. The correlation of near-inertial waves (velocity amplitude 12–20 cm/s and period 12–16 h) and bedform geometry suggest that the extensive sand-wave patches imaged across the shelf are affected by active modern processes and may themselves be modern features or perhaps relict features that remain active presently. Progressive vector diagrams of the nearbed mean current flow indicate a component of cross-shelf directed flow, suggesting an enhanced potential for artifact preservation via cross-shelf advection of anoxic bottom waters by the near-inertial flows measured in this study.

Abstract Stacked channel sands from braided fluvial deposits have attracted interest as excellent hydrocarbon reservoirs because of their high porosity, high permeability, and large volume due to great thickness and lateral extent. Strata of this nature are commonly found in epicontinental-seaway depositional successions. Strata of the Yellow Sea (YS) continental margin compose an excellent modern analog of epicontinental-sea and foreland-basin depositional settings because of the YS’s very high sediment supply, shallow depth, and gentle gradient from the shelf edge to basin. Today, these conditions are rarely found on modern continental margins, but they were quite significant in ancient continental-margin stratigraphic successions. Therefore, a grid of approximately 5,024 km of high-resolution (<1 m) seismic-reflection and chirp-sonar data and cores were collected from the YS to begin to develop models of the spatial variability of reservoir facies that evolve in this type of system. These data have been processed, filtered at 300 to 2,000 Hz, and interpreted in a sequence stratigraphic framework. Seismic facies were objectively identified on the basis of reflection orientation, frequency, amplitude, and lateral continuity. These seismic facies are assumed to be related to the mode of sediment deposition and are further interpreted to be indicative of deposition of specific lithofacies within particular systems tracts. Pleistocene falling-stage/lowstand deposits identified on high-resolution seismic-reflection data and chirp-sonar data from the YS continental shelf (and epicontinental sea) consist of seismic facies with reflections that are chaotic or steeply inclined. These facies are located above an erosional unconformity (sequence boundary) that truncates underlying and laterally adjacent reflections. The great lateral extent of these falling-stage/lowstand deposits (nearly 400 km in the southern YS and 100 km in the northern YS) suggests deposition from a rapidly avulsing, braided fluvial depositional environment. The falling-stage facies are locally stacked on other channel sands and separated by thin transgressive systems (silty fine sand), which define prominent transgressive surfaces. Thickness of the channel-sand units is commonly 25 m. These channel sands are capped by organic-rich muds (as thick as ~2 to 10 m). Stratified silty mud deposits occur adjacent to the channel-sand packages. An early assessment of the horizontal and vertical distribution of seismic facies suggests that falling-stage braided fluvial deposits are prevalent in the southern end of the YS (reservoir rock that is relatively homogeneous, with very high lateral continuity, and a volume of ~1,400 km 3). Highstand deposits (identified by downlapping, nearly flat lying, laterally continuous parallel reflections with moderate to high frequency) are more widespread both vertically and horizontally in the north, behind the Shantung-Laoyehling Massif. The Fukien-Reinan Massif is also apparent in the seismic records. Maps of the distribution of these falling-stage/lowstand deposits indicate that an important controlling influence on the distribution of these deposits is the paleogeographic location of preceding lowstand channels and the locations of the crystalline Shantung-Laoyehling Massif in the north and the crystalline Fukien-Reinan Massif in the south. The crystalline rocks serve as barriers to fluvial flow when they are exposed during sea-level lowstands, and they protect certain areas from fluvial reworking and erosion during lowstands. In these protected areas, settling of silt from suspension during sea-level highstands is the dominant depositional mechanism. The high lateral continuity (along both strike and dip) of the falling-stage/lowstand reservoir facies of depositional systems such that of the YS (which ranges from 100 km updip to nearly 1,000 km downdip) is significantly different from that of many Gulf of Mexico systems (which commonly have a maximum lateral continuity of 50 km). In addition to the high continuity of reservoir facies, systems such as the YS also have a seal of fine-grained highstand deposits that lie over the fluvial facies. These highstand deposits are also laterally continuous (over 100 to 1,000 km) and contain a significant quantity of organic matter. They, therefore, also may serve as source rocks.

Abstract High resolution 2D seismic, sidescan sonar images, and shallow penetration cores were used to study a portion (approximately 60 km length) of the upper to middle Texas continental slope. Within the study area are four intra-slope basins presently connected to one another via a network of submarine channels. The depositional setting occurs in water depths of 400 to1500 m and is located depositionally down-dip of Pleistocene fluvio-deltaic complexes. These shelf edge systems represent the source of sediment delivered to these intra-slope basins. Three of these basins are filled, while the fourth, most southerly basin is presently underfilled. The filling of these basins occurred very rapidly and with pronounced cyclicity, in perhaps less than 100 Ky during the late Pleistocene. Based on seismic stratigraphy and facies, the fill of these basins is interpreted to exhibit vertical cyclicity reflecting alternating deposition of mass transport complexes (MTC), distributary channel-lobe complexes (DLC), leveed-channel complexes (LCC), and hemipelagic drape complexes (DC). MTCs are low amplitude, chaotic seismic facies units and are interpreted as mud-rich complexes of slumps, slides, and debris flow deposits. The DLCs are sand-rich depositional units characterized by moderate to high reflection amplitude and continuity. The DLCs exhibit onlapping, compensatory and locally erosional internal reflection geometries and fan shaped or distributary map patterns. These complexes were deposited from highly concentrated sediment gravity flows delivered across the basin floor through networks of relatively small distributary channels or as broad sheet-like flow. LCCs form a distinct seismic facies characterized by low amplitude, highly continuous reflection character and “gullwing” cross-sectional profile. LCCs are considered to form from overbank deposition of low concentration turbidites and contain low to moderate sand percentages. DCs are thin, highly continuous seismic units that represent hemipelagic mudstones deposited during periods of abandonment and sediment starvation. Alternating deposition of MTCs and DLCs dominate the early stages of basin filling. LCCs are not observed within the deeper portions of the basin fills, and are interpreted as elements formed during the latter stages of basin filling episodes. These units represent an integral part of the sediment transport system currently linking the basins. Post-depositional processes have significantly modified these channels and the fill of the basins. Most notable among these processes are headward erosion and mass wasting. This erosional modification occurred in response to flow across local gradient changes along the system as individual basins were filled and subsequently bypassed by sediment gravity flows.