نتایج جستجو برای: glacial erosion
تعداد نتایج: 41285 فیلتر نتایج به سال:
Reconstructing the evolution of ice sheets is critical to our understanding of the global environmental system, but most detailed palaeo-glaciological reconstructions have hitherto focused on the very recent history of ice sheets. Here, we present a three-dimensional (3D) reconstruction of the changing nature of ice-sheet derived sedimentary architecture through the Quaternary Ice Age of almost...
This was a study of subglacial deformation till genesis from a modern temperate glacier, at Sk alafellsj€ okull, Iceland. Detailed microscale properties of till samples (from Scanning Electron Microscope [SEM] and thin section analysis) were examined from a glacial site with in situ subglacial process monitoring and an exposed subglacial surface in the foreland. Two lithofacies were examined, a...
Understanding spin orbital parameter-driven climate change on Mars prior to ~ 20 Ma ago requires geological evidence because numerical solutions for that period are chaotic and non-unique. We show geological evidence that lineated valley fill at low midlatitudes in the northern hemisphere of Mars (~ 37.58 N) originated through regional snow and ice accumulation and underwent glacial-like flow. ...
[1] Glacial sedimentary sequences in the north central United States record multiple advances of the Laurentide Ice Sheet (LIS) since 2 Ma. Although the tills found in these sequences were deposited by southward flowing glacial lobes, little information is available on the geometry of flow lines in the interior of the LIS during any one glaciation, and the provenance of glacial deposits older t...
NASA's New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto's encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection, with a crater retention age no greater than ~10 million years. Surrounding terrains show active glacial flow, apparen...
The effects of Quaternary glacial range partitioning on the diversification of Holarctic biota remain unclear. Glacial refugial lineages may form vicariant species, hybrid products, or merge after secondary contact. Here, we assess the effects of Quaternary glaciation on a Holarctic sexual zooplankter, Daphnia galeata, with apparently marked dispersal capacity and a widespread hybrid lineage in...
[1] Variability in sediment hydraulic properties associated with landscape depositional and erosional features can influence groundwater recharge processes by affecting soil-water storage and transmission. This study considers recharge to aquifers underlying river-incised glaciated terrain where the distribution of clay-rich till is largely intact in upland locations but has been removed by all...
Core MD99-2323 was extracted from the Snorri Drift at a water depth of 1062 m, just south Denmark Strait, and ~120 km Last Glacial Maximum (LGM) margins Iceland East Greenland Ice Sheets. The core chronology (~7.5 to 240 cal ka) is derived radiocarbon dates, marker tephra, paleomagnetic excursion, correlation with North Atlantic δ18O records on Neogloboquadrina pachyderma (δ18ONp). Sedimentatio...
The discovery over the past two decades of viable microbial communities within glaciers has promoted interest in the role of glaciers and ice sheets (the cryosphere) as contributors to subglacial erosion, global biodiversity, and in regulating global biogeochemical cycles. In situ or in-field detection and characterisation of microbial communities is becoming recognised as an important approach...
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