نتایج جستجو برای: holocene
تعداد نتایج: 8437 فیلتر نتایج به سال:
Thick, late Quaternary sediment sections were recovered at several sites on the leeward slope of Great Bahama Bank during Leg 166 of the Ocean Drilling Program. These sections have paleoceanographic records with potentially high temporal resolution. To make an initial assessment of the records corresponding to the Holocene highstand of sea level, we have identified and dated the sediments from ...
A Holocene lake sediment record spanning the past 7300 years from Wishart Lake in the Turkey Lakes Watershed in the Hemi-Boreal of central Ontario, Canada, was used to evaluate the potential drivers of long-term change in diatom assemblages at this site. An analysis of diatom assemblages found that benthic and epiphytic taxa dominated the mid-Holocene (7300-4000 cal yr BP), indicating shallow, ...
The Indo-Pacific warm pool (IPWP), East Pacific cold tongue, and deep overturning atmospheric Hadley (meridional) and Walker (zonal) circulations form a tightly coupled system. In this chapter, we explore the concept of the Hadley circulation as the fundamental driver of changes in this system, and examine its possible impact on global climates of the past. Recent modeling studies indicate that...
Mineral dust plays an important role in the climate system by interacting with radiation, clouds, and biogeochemical cycles. In addition, natural archives show that the dust cycle experienced variability in the past in response to global and local climate change. The compilation of the DIRTMAP (Dust Indicators and Records from Terrestrial and MArine Palaeoenvironments) paleodust data sets in th...
Rebecca Turner Late Quaternary fire histories in the Eastern Mediterranean region from lake sedimentary micro-charcoals. The Eastern Mediterranean has a long history of human occupation, which spans the transition from hunter-gatherers to the establishment of early agro-pastoralist communities, coinciding with the Last Glacial: Interglacial transition. Over the same timeframe a delay in postgla...
Coastal barrier systems have been widely used to understand the responses of coastal margins to fluctuating Pleistocene sea levels. What has become apparent, particularly with the development of robust chronological frameworks, is that gaps in terrestrial barrier sedimentary records are not uncommon and that they most likely reflect phases of barrier construction on the now submerged continenta...
Most of the sediment components that accumulated in Elk Lake, northwestern Minnesota, during the Holocene are autochthonous or biogenic, delivered to the sediment-water interface on a seasonal schedule, preserved in distinct annual laminae (varves). The main allochthonous component is detrital clastic material, as measured by bulk-sediment concentrations of aluminum, sodium, potassium, titanium...
The Great Plains of the United States was the setting for some of the earliest research in North America into patterns and changes in the character of late Pleistocene environments and their effects on contemporary human populations. Many localities in the region have well-stratified records of terminal Pleistocene and early Holocene human (Paleoindian) activity and past environments. These hav...
This paper presents a new reconstruction of prehistoric population of Australia for the last 50 ka, using the most comprehensive radiocarbon database currently available for the continent. The application of new techniques to manipulate radiocarbon data (including correction for taphonomic bias), gives greater reliability to the reconstructed population curve. This shows low populations through...
We studied a complete Holocene sediment record from shallow (zmax = 9.7 m) Lake Harris, Florida (USA) to infer the historical development of the lake and its current eutrophic status. We used (210)Pb and (14)C to date the 5.9-m sediment sequence (core LH-6-13) and determined accumulation rates for bulk sediment, organic matter, calcium carbonate, phosphorus fractions and biogenic silica fractio...
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