نتایج جستجو برای: holocene
تعداد نتایج: 8437 فیلتر نتایج به سال:
The Middle Fork Salmon River watershed spans high-elevation mixed-conifer forests to lowerelevation shrub-steppe. In recent decades, runoff from severely burned hillslopes has generated large debris flows in steep tributary drainages. These flows incised alluvial fans along the mainstem river, where charcoal-rich debris-flow and sheetflood deposits preserve a record of latest Pleistocene to Hol...
We reconstructed Holocene water-level and vegetation dynamics based on pollen and plant macrofossils from a coastal lake in Upper Michigan. Our primary objective was to test the hypothesis that major fluctuations in Great Lakes water levels resulted in part from climatic changes. We also used our data to provide temporal constraints to the mid-Holocene dry period in Upper Michigan. From 9600 to...
At an international scientific meeting held in 2000, the NobelPrize-winning atmospheric chemist Paul Crutzen became increasingly frustrated by the repeated use of the term “Holocene” to describe the earth’s most recent geological epoch. “After the term Holocene was mentioned yet again,” one observer recounts, Crutzen became “visibly agitated” and then “interrupted” the session. “‘Stop using the...
A reconstruction of Holocene sea ice conditions in the Fram Strait provides insight into the palaeoenvironmental and palaeoceanographic development of this climate sensitive area during the past 8500 years BP. Organic geochemical analyses of sediment cores from eastern and western Fram Strait enable the identification of variations in the ice coverage that can be linked to changes in the oceani...
Holocene vegetational dynamics along the prairie-forest border of Minnesota were first documented in McAndrews' classic work. Despite numerous subsequent paleo-studies, a number of questions remain unanswered about the vegetation history of the region. Here, pollen, stable-isotope, mineral, and charcoal data are described from three lakes near McAndrews' sites. These data were compared with oth...
Rea, D. K. and Leinen, M., 1988. Asian aridity and the zonal westerlies: Late Pleistocene and Holocene record of eolian deposition in the northwest Pacific Ocean. Palaeogeogr., Palaeoclimatol., Palaeoecol., 66:1 8. A 30,000-year record of eolian deposition in the northwestern Pacific Ocean provides a history of the aridity of the Asian source region and information on the changing latitude and ...
New observations of reef accretion from several locations show that in Hawai‘i accretion during early to middle Holocene time occurred in areas where today it is precluded by the wave regime, suggesting an increase in wave energy. Accretion of coral and coralline algae reefs in the Hawaiian Islands today is largely controlled by wave energy. Many coastal areas in the main Hawaiian Islands are p...
Nonglacial deposits Artificial fill (Holocene)—Mud, sand, and gravel of varying proportions, possibly including foreign debris such as concrete, logs, timbers, or brick. Used for highway roadbeds and other construction. Thickness generally greater than 2 m. Mapped where fill substantially obscures or has altered original geologic deposit. Beach deposits (Holocene)—Soft sand, silt, and mud depos...
The response of coccolithophore calcification to ocean acidification has been studied in culture experiments as well as in present and past oceans. The response, however, is different between species and strains, and for the relatively small carbonate chemistry changes observed in natural environments, a uniform response of the entire coccolithophore community has not been documented so far. Mo...
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