ISSN:
1573-0417
Schlagwort(e):
pollen
;
palaeoecology
;
paleoclimate
;
glacial
;
interglacial
;
DCA
;
North America
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Geologie und Paläontologie
Notizen:
Abstract Raymond Basin and Bald Knob Basin, Montgomery County, Illinois, formed as kettles during Illinoian time. Fossil pollen from these basins provides information on vegetation and climate during the last glacial-interglacial cycle. The pollen profile at Raymond Basin contains an expanded Sangamonian section and an early Wisconsinan section, but both are missing the late Wisconsinan. The ages for the following pollen zones are estimated by correlation with the deep-sea δ18O record. In the late Illinoian,Picea-Pinus pollen zone 1, dating from about 150–130 ka, represents an apparently closed boreal coniferous forest indicating a cold late-glacial climate. The Sangamonian includes three major pollen zones ranging from about 130–75 ka. The early Sangamonian is represented byQuercus-Ulmus-Carya-Fagus dominance in zone 2, indicating vegetation comparable to the modern deciduous forest and climate that was warm and moist. The middle Sangamonian in zone 3, which is characterized byAmbrosia-Poaceae-Cupressaceae-Quercus pollen, suggests a savanna vegetation and a warm, dry climate. The late Sangamonian is subdivided into aQuercus-Ulmus-Carya subzone (4a) that indicates a mesic forest and greater precipitation; aQuercus-Ambrosia subzone (4b) that suggests drier climate and savanna conditions; and aQuercus-Liquidambar-Carya subzone (4c), containing the ‘southeastern forest’ element,Liquidambar, suggesting the peak in warmth and moisture. The early Wisconsinan is represented by a transitionalPicea-Chenopodiineae zone (5). This unusual assemblage suggests a cool prairie-like vegetation, perhaps with scatteredPicea trees at the end of that depositional interval. The Middle Wisconsinan is marked by the return of high percentages ofPicea andPinus pollen in zone 6. The latest pollen zone (7) is dominated by Chenopodiineae pollen and is absent at Raymond Basin. It is most likely Holocene in age, and probably represents prairie conditions and warm, dry climate. Apparent surface-temperature and apparent effective-moisture curves were derived from the first detrended correspondence analysis (DCA) axis of the pollen data. The first axis correlates well with the normalized deep-sea δ18O curve of sea surface temperature, and the second is controlled mainly by precipitation. The interglacial vegetation differs from that predicted by models driven by orbitally-induced insolation curves.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00682432
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