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.

Abstract Late Quaternary stratigraphy of the shelf over which the modern tropical Mahakam River delta is prograding indicates an alternating dominance of shelf carbonate sediments and siliciclastic deltaic deposits. Control of these major facies shifts is in response to high-frequency cyclic relative sea-level changes. Seismic facies and stratigraphy of the two latest Pleistocene depositional episodes reflect interplay of deltaic and shelf processes as well as accommodation during the last two glacio-eustatic cycles. Over 3000 line km of high-resolution seismic and side-scan sonar data calibrated to 380 bottom samples and 97 vibracores amd piston cores help characterize seismic facies of the Holocene and latest Pleistocene shelf deposits, which have been influenced by a strong north-to-south flowing current from the Makassar Strait. Holocene prodelta sediments are confined to the inner shelf of the northern and central sectors of the delta front, but they are skewed to the south, creating a broad facies tract in the southern sector. The middle and outer parts of the shelf are dominated by mounded topography characterized by both individual and aggregate bioherms. Mound relief varies from a few meters to over 30 m, but the average is about 20 m. This topography is locally accentuated by intervening erosional lows. Cores through the upper 6 m of these features indicate that the mounds are constructed of flakes of the calcareous green alga Halimeda in a matrix of foraminifera-rich terrigenous mud. The Halimeda bioherms are established on a ravinement surface formed during the Pleistocene to Holocene transgression. Inner-shelf bioherms are now being slowly buried by the Holocene advance of the Mahakam delta. Below the Pleistocene to Holocene ravinement surface are the deposits associated with the preceding relative sea-level fall. Deposits defining this falling-stage systems tract and associated lowstand systems tract consist of entrenched fluvial networks, incised-alluvial-valley fill, aggraded delta-plain and platform deposits, and prograded delta lobes. Pleistocene deltaic deposits have prograded to the shelf edge along the entire shelf–slope break. Over 50% of the stratigraphy in the lowstand systems tract is related to aggradation during the lowstand turnaround. The Pleistocene deltaic deposits bury massive carbonate bioherms and aggregates of bioherms that mimic their Holocene counterparts in morphology and scale. A prominent ravinement surface underlies the bioherm facies, and a maximum flooding surface runs through these features.

Abstract The Congo deep-sea fan was surveyed recently by a unique set of data that includes as of today more than 30 piston cores and 25,000 km of 2D high resolution seismic acquisition. During the different cruises, the following tools were used simultaneously: an EM12 dual Simrad swath bathymetric and sonar system, a 3.5 kHz mud penetrator, an oceanographic seismic system (6 traces), and a multichannel seismic streamer (96 traces) with G.I. air gun source. The data set covers an area in excess of 200,000 km 2 from the canyon head to the most recent depositional lobes 700 km downslope. In this four year project cosponsored by ELF and IFREMER, the prime objective was to gain comprehension of the construction and the lateral evolution of the recent fan. As a result, we were able to build a chronostratigraphic and architectural model at the fan scale. The Congo Canyon geometry has been enhanced and has confirmed the lack of any tributaries downdip from the continental shelf. Furthermore, no real large scale slumped blocks have observed at the base of the steep submarine canyon slopes. Therefore, widening of the canyon seems to have occurred through progressive sliding and creeping of the bordering Congolese and Angola platform into the canyon valley. The recent Congo fan growth results from the stacking and overlapping of at least 3 main stratigraphic units. Each unit is composed of numerous channel-levee complexes laterally switching path through time by avulsion. Previous interpretation of “distributaries” at the toe of the Congo submarine canyon is invalidated as this surveys shows that they are in fact abandoned channel-levee complexes. It has also been confirmed that in this particular mud-rich submarine fan setting, only one channel is active at a time. The present day “active” fan channel as well as the canyon are eroding into previously deposited sediments. In the levees, individual sub-kilometer scale morphological features have been mapped, and sedimentary and/ or structural processes responsible for such geometries have been reviewed. The present day depositional lobe is more than 700 km away from the Congo River mouth. It occupies an area of around 300 km 2 and shows clustered lobes, 20 km long, prograding down slope. It is now clear that multibeam coverage of the lower part of the canyon, over complex lobe, and channel avulsion zones shows strong similarities with seismic attribute maps of West Africa’s structurally controlled turbiditic channel complexes.

ABSTRACT The Conception submarine fan is located in the northwestern corner of the Santa Barbara basin, within the tectonically active western Transverse Ranges Province of southern California. This small radial fan heads off a series of small submarine canyons and slope gullies that were fed by the modern and ancestral Santa Ynez River, intermittent streams and longshore drift. A unique data set of high resolution analog to deep penetration, CDP seismic reflection profiles and records, collected along north-south/east-west tracklines was used for this study. These data were collected for or by the energy industry primarily between 1960-1985, and were augmented by boring logs and near-surface core and grab samples. Surface and deep-tow side scan sonar records over critical features (e.g. fan channels, faults, etc.) complete the data set. East-west trending oblique-slip faults and related folds control the position of shelf break along the northern margin of the basin. Barriers or tectonic dams along the shelf were formed by growing anticlinal folds and active faults and breached by streams incised along shear zones such as the south Santa Ynez fault and minor cross faults. At these points the small submarine canyons that fed the fan during low-stands of sea-level were established. Inactive today, this Quaternary fan extends from shelf break (-90 m) to the basin floor (-550 m), a distance of 25 km. In width the middle fan is 20 to 25 km across, while the lower fan is 35 km across where it is deflected eastwards along the southern or island margin of the basin. The fan is about 150 m thick and internally consists of four major, 30-40 m thick sand-thin mudstone sequences that represent low and high sea level stands. Uplift along the northern and western margins of the basin and the southern or island margin restricted the fan’s radial growth and progressively shifted its activity to the southeast toward the center of the basin. The southern edge of the fan laps onto the basin apron of the island or southern margin of the basin. The eastern edge of the fan is marked by an abrupt southwesterly deflection of the east-west trending isobaths that are typical of the northern slope. Internally this boundary is evidenced by a rapid change in seismic facies as slope mudstones interfinger with sand-rich fan deposits. Isopachs of the four seismic sequences of the fan document the offset or horizontal stacking of these sequences. The maximum thickness of each overlying sequence is offset horizontally from the maximum thickness of the underlying sequence. As a potential reservoir the Conception Fan offers four 30-45 m (maximum) thick sand-rich sequences separated by mud seals (3± m thick). Each sand sequence is topographically high along its axis of maximum thickness. The entire fan is encased in mud-as it overlies mudstones of the Pico Formation and is covered by a high-stand mud deposit. An offset stacking model of depositional sequences or “fan lobes” provides a valuable tool for exploration. Examples of offset stacking include the Lathrop and the Winters Formation fans of the northern Great Valley and Neogene fans in southern California.