Abstract Scroll bars are curvilinear ridges of sediment deposited as meandering channels migrate laterally. It is unclear exactly which variables control the spacing, height, and curvature of scroll ridges, and in turn how these properties record channel migration histories. This study tests the relationship between channel and scroll bar geometries in river systems with laterally migrating chute channels that deposit their own scroll packages. LiDAR- and Shuttle Radar Topography Mission-derived digital elevation models (DEMs) are used to calculate the spacing, relief, wavelength, and curvature of scroll bars in eight different chute-channel-dominated river systems with a range of channel dimensions, slopes, and water and sediment discharge regimes. Seven of the eight rivers have statistically indistinguishable chute channel (CC) and main channel (MC) scroll spacings, even though the chute channels have smaller channel dimensions. Additionally, there is no correlation between scroll spacing and relief for main or chute channels. For LiDAR-derived DEMs, the ratio between median scroll spacing and median channel width is low and falls within a narrow range for MC scrolls (from 0.13 to 0.22; mean 0.16), but is higher with a wider range for CC scrolls (from 0.48 to 1.33; mean 0.8). CC scrolls are straighter overall than MC scrolls, but there is no correlation between curvature and scroll spacing. Overall, these results show that (1) chute channel scrolls are often indistinguishable from main channel scrolls based on spacing and relief, and (2) MC and CC scrolls have different relationships with formative channel widths, which suggests that other variables, such as lateral migration rate and flood inundation depth, are key controls on scroll bar geometries.

Abstract This study provides a comprehensive examination of the Oligocene–Miocene Ethiopian Flood Basalt Province (EFBP) within the Blue Nile (Abay) Basin (BNB), Ethiopia. Extensive logging through 29 new sections has enabled an updated stratigraphic account of the BNB to be elucidated and reveals the significance of intravolcanic sedimentary systems within the EFBP. Five sub- and intra-volcanic surfaces were modelled using spot heights to generate isopach maps that were used to constrain the thickness variations within the stratigraphy. Additionally, lineaments, Strahler stream segments and volcanic cones were mapped out from digital elevation models (SRTM DEM) and satellite data (ASTER and LANDSAT 8 imagery). These data were used in conjunction with the isopach maps to better understand the basinal controls on the distribution of intravolcanic sedimentary systems within the BNB. The study reveals how NNE and ESE/SE structural trends have influenced the distribution of volcanoes within the basin, which has in turn disrupted the distribution and lithofacies architecture of the volcanic sequences. The presence of intrabasinal ridges parallel to the major structural trends are also revealed, which formed relatively short-lived drainage divides. The implications of these intrabasinal highs on the composition and the reservoir potential of intravolcanic sedimentary successions are discussed.

Abstract The formal beginning of geoarchaeology in India can be traced back to 1863 when the first palaeolith was documented and collected by Robert Bruce Foote in Tamil Nadu and later described in a detailed geological context. Today, various geological tools such as geospatial analytical tools are available to provide extra mileage to geoarchaeological investigations. They supplement field evidence and enable researchers to display, manipulate, and model geological data and the associated archaeological evidence. The present paper attempts to summarize the current status of understanding of the Quaternary geoarchaeology of the Tapi River basin in west-central India. The aspects considered include geomorphology, landform evolution, morphometric parameters, relationships between climate and basin evolution and Palaeolithic and Mesolithic evidence. This present study uses Landsat imagery, locational data, Survey of India topographic sheets and Shuttle Radar Topography Mission data in ArcGIS software. The study is the first comprehensive attempt to summarize the issue of prehistoric human adaptations (dominated mainly by Late Pleistocene evidence) through changing environments, with an assumption that the two occurred in synchronization. Another assumption is that the reported lithic and fossil sites and the surrounding areas have preserved signatures of original landforms and sedimentary contexts. Through these perspectives and visual integration of topography, drainage networks and Landsat image parameters in a Geographic Information System platform, along with other variable field inputs, a testable hypothetical model of the Quaternary evolution of Central Tapi valley is proposed. Additionally, an accelerator mass spectrometry (AMS) date of 47 145 cal BP for a newly discovered ostrich eggshell fragment from Sakegaon near Bhusawal is presented and its palaeoanthropological implications are discussed. Altogether, our observations from the study area, such as an expansion of land use from the Acheulean onwards, signatures of arid phases and the oldest reported ostrich eggshell, warrant further detailed multidisciplinary research. An in-depth understanding of the first-to-last occurrences of ostriches in the region and comprehensive picture of their pan-South Asian distribution in general will help address the issue of prehistoric human adaptations through changing environments.