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The carbon stable isotope composition (δ13C) of tooth enamel in mosasaurid squamates reflects aspects of their diet and diving behaviour. Here we present new δ13C data for such marine squamates from the Maastrichtian of Denmark and compare these with results obtained in previous studies from the lower-latitude type area of the Maastrichtian Stage (latest Cretaceous; 72.1-66.0 Ma) in the south-east Netherlands and north-east Belgium. For the Danish samples, there is a weak correlation between mosasaur body size and δ13C values, with larger-sized taxa having lower δ13C values, comparable to what has previously been observed for mosasaurs from the Maastrichtian type area. [ABSTRACT FROM AUTHOR]

Marine sediments from continental margins provide high-resolution archives of marine and continental climate, in particular near large river mouths. The Zambezi is one of the largest rivers in East Africa, discharging large amounts of fine-grained sediments onto the western margin of the Mozambique Channel. Accurate reconstructions of past variations in river discharge can be retrieved from the depositional history of riverine sediments. In this study, sedimentation patterns along the Mozambique Margin are inferred from a series of sediment cores spanning the last 20 kyr. These cores were retrieved off the Zambezi Mouth from the shelf and from various depths at the continental slope to provide detailed information on the depositional history of this region. High-resolution X-ray fluorescence and magnetic susceptibility core scanning measurements as well as grain-size distributions of the lithogenic sediment fraction, and organic matter and carbonate content analyses resolve centennial--millennial timescale variations in sediment transport and deposition along the Mozambique Margin. Largest changes in lithogenic sediment deposition coincide with the flooding of the Mozambique Shelf. Due to deglacial sea-level rise and changes in oceanic currents, fine-grained, mainly Zambezi sediments were no longer primarily deposited south of the Zambezi Mouth, but increasingly deposited onto the Mozambique Shelf, and transported northwards over the shelf before spilling over to the slope. In addition, flooding of the shelf initiated remobilization and down-slope transport of coarse-grained, winnowed sediments. The Heinrich Event 1 and Younger Dryas are clearly indicated as events of increased fine-grained sediment deposition along the Mozambique Margin, possibly linked to increased riverine runoff from the Zambezi Catchment, which is in harmony with a southward shift of the Intertropical Convergence Zone (ITCZ) and associated African rainfall belts, causing wetter conditions. This study illustrates that interpreting marine and continental climate proxy records in the vicinity of river deltas in terms of climate change requires proper consideration of sea-level and oceanic circulation induced effects on the transport and deposition patterns of fine-grained sediments at continental slopes. [ABSTRACT FROM AUTHOR]

To address questions regarding the evolutionary origin, radiation and dispersal of the genus Homo, it is crucial to be able to place the occurrence of hominin fossils in a high-resolution chronological framework. The period around 2 Ma (millions of years ago) in eastern Africa is of particular interest as it is at this time that a more substantial fossil record of the genus Homo is first found. Here we combine magnetostratigraphy and strontium (Sr) isotope stratigraphy to improve age control on hominin-bearing upper Burgi (UBU) deposits in Areas 105 and 131 on the Karari Ridge in the eastern Turkana Basin (Kenya). We identify the base of the Olduvai subchron (bC2n) plus a short isolated interval of consistently normal polarity that we interpret to be the Pre-Olduvai event. Combined with precession-forced (~20 kyr [thousands of years]) wet-dry climate cycles resolved by Sr isotope ratios, the magnetostratigraphic data allow us to construct an age model for the UBU deposits. We provide detailed age constraints for 15 hominin fossils from Area 131, showing that key specimens such as cranium KNM-ER 1470, partial face KNM-ER 62000 and mandibles KNM-ER 1482, KNM-ER 1801, and KNM-ER 1802 can be constrained between 1.945 ± 0.004 and 2.058 ± 0.034 Ma, and thus older than previously estimated. The new ages are consistent with a temporal overlap of two species of early Homo that can be distinguished by their facial morphology. Further, our results show that in this time interval, hominins occurred throughout the wet-dry climate cycles, supporting the hypothesis that the lacustrine Turkana Basin was a refugium during regionally dry periods. By establishing the observed first appearance datum of a marine-derived stingray in UBU deposits at 2.058 ± 0.034 Ma, we show that at this time the Turkana Basin was hydrographically connected to the Indian Ocean, facilitating dispersal of fauna between these areas. From a biogeographical perspective, we propose that the Indian Ocean coastal strip should be considered as a possible source area for one or more of the multiple Homo species in the Turkana Basin from over 2 Ma onwards., (Copyright © 2013 Elsevier Ltd. All rights reserved.)