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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Long-Term African Dust Delivery To The Eastern Atlantic Ocean From The Sahara And Sahel Regions: Evidence From Quaternary Paleosols On The Canary Islands, Spain, Daniel R. Muhs, Joaquín Meco, James R. Budahn, Gary L. Skipp, Kathleen R. Simmons, Matthew C. Baddock, Juan F. Betancourt, Alejandro Lomoschitz
Long-Term African Dust Delivery To The Eastern Atlantic Ocean From The Sahara And Sahel Regions: Evidence From Quaternary Paleosols On The Canary Islands, Spain, Daniel R. Muhs, Joaquín Meco, James R. Budahn, Gary L. Skipp, Kathleen R. Simmons, Matthew C. Baddock, Juan F. Betancourt, Alejandro Lomoschitz
United States Geological Survey: Staff Publications
Africa is the most important source of dust in the world today and dust storms from that continent frequently deposit sediment on the nearby Canary Islands. Many investigators have inferred African dust inputs to Canary Islands paleosols based only on the presence of quartz. However, some local rocks do contain this mineral, so quartz alone is insufficient proof of dust deposition. Further, it is not known whether the Sahara Desert or the Sahel region is more important as a dust source. We address these issues by study of sequences of Pleistocene aeolian sands on the islands of Lanzarote and Fuerteventura. …
Coherent Late-Holocene Climate-Driven Shifts In The Structure Of Three Rocky Mountain Lakes, Jeffrey R. Stone, Jasmine E. Saros, Gregory T. Pederson
Coherent Late-Holocene Climate-Driven Shifts In The Structure Of Three Rocky Mountain Lakes, Jeffrey R. Stone, Jasmine E. Saros, Gregory T. Pederson
United States Geological Survey: Staff Publications
Large-scale atmospheric pressure centers, such as the Aleutian and Icelandic Low, have a demonstrated relationship with physical lake characteristics in contemporary monitoring studies, but the responses to these phenomena are rarely observed in lake records. We observe coherent changes in the stratification patterns of three deep (>30 m) lakes inferred from fossil diatom assemblages as a response to shifts in the location and intensity of the Aleutian Low and compare these changes with similar long-term changes observed in the 18O record from the Yukon. Specifically, these records indicate that between 3.2 and 1.4 ka, the Aleutian Low shifted …
Geochemical Evidence For Seasonal Controls On The Transportation Of Holocene Loess, Matanuska Valley, Southern Alaska, Usa, Daniel R. Muhs, James R. Budahn, Gary Skipp, John P. Mcgeehin
Geochemical Evidence For Seasonal Controls On The Transportation Of Holocene Loess, Matanuska Valley, Southern Alaska, Usa, Daniel R. Muhs, James R. Budahn, Gary Skipp, John P. Mcgeehin
United States Geological Survey: Staff Publications
Loess is a widespread Quaternary deposit in Alaska and loess accretion occurs today in some regions, such as the Matanuska Valley. The source of loess in the Matanuska Valley has been debated for more than seven decades, with the Knik River and the Matanuska River, both to the east, being the leading candidates and the Susitna River, to the west, as a less favorable source. We report here new stratigraphic, mineralogic, and geochemical data that test the competing hypotheses of these river sources. Loess thickness data are consistent with previous studies that show that a source or sources lay to …
Possible Tsunami Deposits On The Caribbean Coast Of The Yucatán Peninsula, Charles Shaw, Larry Benson
Possible Tsunami Deposits On The Caribbean Coast Of The Yucatán Peninsula, Charles Shaw, Larry Benson
United States Geological Survey: Staff Publications
The western Caribbean Basin is notable for its tectonic stability. It has experienced no historical earthquakes or the tsunami that sometimes accompany them. This paper describes a single, wedge-shaped, boulder-covered, coastal berm on the Yucatán coast of México that stretches unbroken for 50 km across a coastal segment characterized by rocky headlands that alternate with crescent beaches. The remainder of the 350 km of Yucatán coast consists mostly of mangrove that extends 1 to 30 km inland, often behind long, sandy beaches. On the headlands, the surface of the berm is densely paved with boulders—large boulders on its seaward face …
Loess Origin, Transport, And Deposition Over The Past 10,000 Years, Wrangell-St. Elias National Park, Alaska, Daniel R. Muhs, James R. Budahn, John P. Mcgeehin, E. Arthur Bettis Iii, Gary Skipp, James B. Paces, Elisabeth A. Wheeler
Loess Origin, Transport, And Deposition Over The Past 10,000 Years, Wrangell-St. Elias National Park, Alaska, Daniel R. Muhs, James R. Budahn, John P. Mcgeehin, E. Arthur Bettis Iii, Gary Skipp, James B. Paces, Elisabeth A. Wheeler
United States Geological Survey: Staff Publications
Contemporary glaciogenic dust has not received much attention, because most research has been on glaciogenic dust of the last glacial period or non-glaciogenic dust of the present interglacial period. Nevertheless, dust from modern glaciogenic sources may be important for Fe inputs to primary producers in the ocean. Adjacent to the subarctic Pacific Ocean, we studied a loess section near Chitina, Alaska along the Copper River in Wrangell-St. Elias National Park, where dust has been accumulating over the past ~10,000 years. Mass accumulation rates for the fine-grained (<20 >µm) fraction of this loess section are among the highest reported for the …
Origin Of The Sinai-Negev Erg, Egypt And Israel: Mineralogical And Geochemical Evidence For The Importance Of The Nile And Sea Level History, Daniel R. Muhs, Joel Roskin, Haim Tsoar, Gary Skipp, James Budahn, Amihai Sneh, Naomi Porat, Jean-Daniel Stanley, Itzhak Katra, Dan G. Blumberg
Origin Of The Sinai-Negev Erg, Egypt And Israel: Mineralogical And Geochemical Evidence For The Importance Of The Nile And Sea Level History, Daniel R. Muhs, Joel Roskin, Haim Tsoar, Gary Skipp, James Budahn, Amihai Sneh, Naomi Porat, Jean-Daniel Stanley, Itzhak Katra, Dan G. Blumberg
United States Geological Survey: Staff Publications
The Sinai-Negev erg occupies an area of 13,000 km2 in the deserts of Egypt and Israel. Aeolian sand of this erg has been proposed to be derived from the Nile Delta, but empirical data supporting this view are lacking. An alternative source sediment is sand from the large Wadi El Arish drainage system in central and northern Sinai. Mineralogy of the Negev and Sinai dunes shows that they are high in quartz, with much smaller amounts of K-feldspar and plagioclase. Both Nile Delta sands and Sinai wadi sands, upstream of the dunes, also have high amounts of quartz relative …
A Robust, Multisite Holocene History Of Drift Ice Off Northern Iceland: Implications For North Atlantic Climate, John T. Andrews, Dennis Darby, Dennis Eberle, Anne E. Jennings, Matthias Moros, Astrid Ogilvie
A Robust, Multisite Holocene History Of Drift Ice Off Northern Iceland: Implications For North Atlantic Climate, John T. Andrews, Dennis Darby, Dennis Eberle, Anne E. Jennings, Matthias Moros, Astrid Ogilvie
United States Geological Survey: Staff Publications
An important indicator of Holocene climate change is provided by evidence for variations in the extent of drift ice. A proxy for drift ice in Iceland waters is provided by the presence of quartz. Quantitative xray diffraction analysis of the < 2 mm sediment fraction was undertaken on 16 cores from around Iceland. The quartz weight (wt.)% estimates from each core were integrated into 250-yr intervals between −0.05 and 11.7 cal. ka BP. Median quartz wt.% varied between 0.2 and 3.4 and maximum values ranged between 2.8 and 11.8 wt.%. High values were attained in the early Holocene and minimum values were reached 6–7 cal. ka BP. Quartz wt.% then rose steadily during the late Holocene. Our data exhibit no correlation with counts on haematite-stained quartz (HSQ) grains from VM129-191 west of Ireland casting doubt on the ice-transport origin. A pilot study on the provenance of Fe oxide grains in two cores that cover the last 1.3 and 6.1 cal. ka BP indicated a large fraction of the grains between 1 and 6 cal. ka BP were from either Icelandic or presently unsampled sources. However, there was a dramatic increase in Canadian and Russian sources from the Arctic Ocean ~1 cal. ka BP. These data may indicate the beginning of an Arctic Oscillation-like climate mode.
An Association Of Benthic Foraminifera And Gypsum In Holocene Sediments Of Estuarine Chesapeake Bay, Usa, John Cann, Thomas Cronin
An Association Of Benthic Foraminifera And Gypsum In Holocene Sediments Of Estuarine Chesapeake Bay, Usa, John Cann, Thomas Cronin
United States Geological Survey: Staff Publications
Two cores of Holocene sediments recovered from the Cape Charles Channel of Chesapeake Bay yielded radiocarbon ages of about 6.8 to 5.8 ka for the lower intervals. Fossil foraminifera preserved in these lower sediments are dominated by species of Elphidium, which make up about 90% of the assemblage throughout, and probably signify deposition in hypersaline waters. Buccella frigida and Ammonia beccarii are the only other species commonly present. Hypersalinity of bottom waters seems to have been maintained by water-density stratification in a basin-like section of the channel. In core PTXT -4-P-I transition to modem Chesapeake conditions, in which numbers …