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Temporal and spatial sources of silica for chert remain poorly constrained. Modern sources to the worlds oceans include silica in rivers > aeolian (dust) deposition > sea floor vents and submarine weathering. However, changes in aridity and dust flux during the Phanerozoic may explain variations in the ocean silica cycle and times and places of chert formation. The chemistry of fine quartz dust (FQD) provides a chemical mechanism for the transformation of FQD to polymorphs of silica in chert; FQD is readily dissolved, then reprecipitated as Opal-A by either biotic or abiotic processes. An unequivocal relation between increases in dust flux and biogenic opal-A in the western Pacific Ocean during the past 200 kyr...
This dataset was created as part of the USGS Afghanistan Project investigating artisanal and small-scale mining activity. Clay mining for brick making purposes represents a small but important segment of the mineral extraction industry in Kabul, Afghanistan. Over the past several decades Kabul has grown from a relatively small city, with a 1970 population of less than 500,000 people, to a sprawling urban center with approximately 4.2 million people in 2020 (CIA 2020). Population growth has expanded the need for housing, commercial, and industrial buildings, and associated infrastructure. This has greatly increased demand for bricks, the primary construction material of the region. In this study, very high-resolution...
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This digital database is the product of collaboration between the U.S. Geological Survey, the Alfred Wegener Institute for Polar and Marine Research Potsdam, Foothill College GeoSpatial Technology Certificate Program, and the Geophysical Institute at the University of Alaska. The primary goal for creating this digital database is to enhance current estimates of organic carbon stored in deep permafrost, in particular Late Pleistocene syngenetic ice-rich loess permafrost deposits, called Yedoma. This deposit is vulnerable to thermokarst and erosion due to natural and anthropogenic disturbances. The original paper maps were issued by the Department of Natural Resources of the Russian Federation or its predecessor the...
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Thin loess deposits on the uplands of the southeastern Colorado Plateau have previously not been well studied. We sampled deposits and soils from trenches on Hatch Point mesa near Canyonlands National Park, Utah, and from two outcrops in Mesa Verde National Park, Colorado. At Hatch Point, the oldest buried unit yielded two OSL ages of 10,370 and 7,555 yr; the middle unit yielded 10 OSL ages from 6220 to 1385 yr; and the youngest unit has a single age of 1740 yr. At Mesa Verde, three loess units are preserved in the two outcrops we examined; six OSL ages range from 51 to 17 ka. At least one buried soil is present between two units with ages of about 50 and 40 ka. The ages of the loess units in both study areas correspond...


    map background search result map search result map Digital Database and Maps of Quaternary Deposits in East and Central Siberia Data release for Late Quaternary loess and soils on uplands in the Canyonlands and Mesa Verde areas, Utah and Colorado The chemistry of eolian quartz dust and the origin of chert Point locations of brick kilns in Kabul, Afghanistan, derived from 1965, 2004, 2011, and 2018 satellite imagery Data release for Late Quaternary loess and soils on uplands in the Canyonlands and Mesa Verde areas, Utah and Colorado Point locations of brick kilns in Kabul, Afghanistan, derived from 1965, 2004, 2011, and 2018 satellite imagery Digital Database and Maps of Quaternary Deposits in East and Central Siberia The chemistry of eolian quartz dust and the origin of chert