As anyone travelling on the roads of southeast England between 2006 and 2008 has probably been aware, major improvements have recently been made at the junction of the M25 and A2 motorways, south of the main Dartford crossing of the River Thames ( Fig. 1 ). The roadworks, funded by the UK Highways Agency, with the main contractors Jacobs Babtie and Costain, were accompanied by archaeological investigations carried out by Oxford Archaeology between 2003 and 2006. The archaeological programme had a major Palaeolithic/Pleistocene element under my direction ( Fig. 2 ) that has produced evidence of Neanderthal occupation early in the last glaciation (the Devensian, which lasted from 115 000 to 10 000 bp ), during a period when Britain had until now, been thought to have been entirely deserted. Figure 1 Open in figure viewer PowerPoint Site location and areas of investigation. 相似文献
The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments. 相似文献
An experiment was conducted to quantify the effects of different levels of nutrient enrichment on the plant communities of temperate coastal lagoons, specifically the lagoons of the northeast U.S. Ten mesocosms, each containing coastal water, lagoon sediments, and plants and animals found in natural lagoons, were subjected to five levels of enrichment. Two mesocosms served as controls, and received no experimental nutrient additions. The remaining 8 mesocosms were enriched in duplicate with ammonium plus phosphate at 1.0 and 0.11 mmol N or P m?2 d?1, 2.0 and 0.19 mmol N or P m?2 d?1, 4.0 and 0.35 mmol N or P m?2 d?1, and 8.0 and 0.67 N or P mmol m?2 d?1. At all levels of enrichment, and through much of the experiment, water column concentrations of dissolved inorganic nitrogen (DIN) were drawn down to background levels. Despite the efficient drawdown of added DIN even at the highest loadings, differences in plant biomass among the 5 treatments were difficult to detect. Enrichment at the highest loadings increased standing stocks of phytoplankton for one month mid-experiment. No significant effect of loading could be detected for dry biomass of eelgrass (Zostera marina), epiphytic material, drift macroalgae, or for all plant components combined. The experiment has demonstrated that the enrichment responses of coastal lagoons can be diverse, especially at intermediate loadings. 相似文献
We present the results of early observations for 130 error-boxes of gamma-ray bursts performed with the Mobile Astronomical System of TElescope-Robots (MASTER) global network of robotic telescopes from Moscow State University in fully automatic mode (2011–2017). Among them, GRB 130907A, GRB 120811C, GRB 110801A, GRB 120404A, GRB 140129B, GRB140311B, and GRB 160227A are considered in details. Among these 130 gamma-ray bursts, in the first 60 s after the trigger with the Swift, Fermi, INTEGRAL, MAXI, Lomonosov, and Konus-Wind orbital observatories, the MASTER was pointed on 51 gamma-ray bursts, being the leader in terms of the first pointing. Full observation automation and MASTER own real-time image processing software allowed us to obtain unique data on early optical emission that accompanied 44 gamma-ray bursts (GRB 110801A, GRB120106A, GRB 120404A, GRB 120811C, GRB 120907A, GRB 121011A, GRB 130122A, GRB 130907A, GRB 131030A, GRB 131125A, GRB 140103A, GRB 140108A, GRB 140129B, GRB 140206A, GRB 140304A, GRB 140311B, GRB 140512A, GRB 140629A, GRB 140801A, GRB140907A, GRB 140930B, GRB141028A, GRB 141225A, GRB 150210A, GRB 150211A, GRB 150301B, GRB 150323C, GRB 150404A/Fermi trigger 449861706, GRB 150403A, GRB 150413A, GRB 150518A, GRB 150627A, GRB 151021A, GRB 151215A, GRB 160104A, GRB 160117B, GRB 160131A, GRB 160227A, GRB 160425A, GRB 160611A, GRB 160625B, GRB 160804A, GRB 160910A, GRB 161017A, GRB 161117A, GRB 161119A). We obtain light curves for 13 gamma-ray bursts among the above listed ones and compare the data in the optical (MASTER), X-ray (Swift-XRT), and hard X-ray (Swift-BAT) ranges. 相似文献
Competition between taxa related to climate changes has been proposed as a possible factor in Pleistocene megafaunal extinctions, and here we present isotope evidence of the diets of three co-existing bear species [black bear (Ursus americanus), brown bear (Ursus arctos), and the now extinct short-faced bear (Arctodus simus)] from a locale in western North America dating to the Late (Terminal) Pleistocene (~14.5–11.7 ka). The three bear species were found at several sites on Vancouver Island, on the western coast of Canada. To examine the chronological overlap and niche partitioning between these species of bear, we used direct radiocarbon dating, stable isotope analysis and ZooMS proteomic identification methods. Here we present new radiocarbon evidence from Terminal Pleistocene U. americanus, U. arctos and A. simus from several sites on the island, along with both bulk collagen and compound-specific isotope data for these species. Radiocarbon dates confirm the chronological overlap of Arctodus and both Ursus species in the montane regions of the island at the end of the Pleistocene. Stable isotope data reveal niche differentiation between these species, with U. americanus occupying a distinctly lower trophic position than the other two taxa. 相似文献
