Late Quaternary Vegetational and Climatic Changes in the Pampa Grassland of Argentina
Late Quaternary Vegetational and Climatic Changes in the Pampa Grassland of Argentina
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DOI：
10.1006/qres.1996.0007
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发表时间：
1996-01
影响因子：
2.3
通讯作者：
A. Prieto
中科院分区：
文献类型：
--
作者：
A. Prieto
摘要根据从河谷壁和考古发掘的年代地层剖面中获得的花粉，重建了阿根廷潘帕草原第四纪晚期的植被和气候。在10,500年前，草原中部为草本沙生草原，西南部为沙生和盐生草原混生的旱生林地。这些类型的植被和在现今海岸地区（38°S）盛行的大陆条件表明，亚湿润-干燥气候和年降水量比现在低100毫米。随后的变化朝着池塘，沼泽，和foodplains的植被特征，或对环境与当地更有效的水分，发生在约。10，500 yr B. P.，表明年降水量接近现代水平或在潘帕草原中部有更高的可用水，这种类型的植被一直存在到8000 yr B. P.，在西南部的潘帕草原，这种植被发展之前，7000年B. P.，并持续到约。5000年B. P.海平面高于现在的约。6200 yr B. P.与植被的急剧变化和38°S处占优势的当地盐生植物群落的发展一致。5000年B. P.后发生的亚湿润干燥的条件下，晚全新世植被的特点是花粉组合类似的沙生植物和盐生植物群落的南部大草原，与社区更多的土壤条件。同时，在南纬38°，淡水花粉组合和微体古生物遗迹的优势表明海平面下降。趋向潮湿，温和的条件下，约。1000 yr B. P.的脊椎动物遗骸的特点温和和潮湿的条件，以及一个非常短的，但干燥的插曲，在18世纪世纪的地质建议，没有明确的证明在花粉序列。植被和气候变化的原因是纬度的变化和南部大气环流强度的变化以及海平面的变化。
Abstract The vegetation and climate of the Pampa grassland, Argentina, during the late Quaternary are reconstructed from pollen recovered from dated stratigraphic sections from arroyo walls and from archaelogical excavations. Prior to 10,500 yr B.P., herbaceous psammophytic steppe existed in the central part of the Pampa grassland while xerophytic woodland associated with psammophytic and halophytic steppe occurred in the southwestern part of the Pampa. These types of vegetation and the continental conditions that prevailed in the area of the present-day coast (38°S), indicate subhumid-dry climate and annual precipitation 100 mm lower than present. A subsequent change toward a vegetation characteristic of ponds, swamps, and foodplains, or toward environments with locally more effective moisture, occurred ca. 10,500 yr B.P. suggesting annual precipitation close to modern levels or a higher availability of water in the central part of the Pampa grassland, this type of vegetation existed until 8000 yr B.P., when it was replaced by grassland communities that lasted until 7000 yr B.P. In the southwestern part of the Pampa grassland, this vegetation developed before 7000 yr B.P. and persisted until ca. 5000 yr B.P. Sea level higher than the present ca. 6200 yr B.P. is consistent with sharp modification of the vegetation and development of local halophytic communities dominant at 38°S. A return to subhumid-dry conditions occurred after 5000 yr B.P. The late Holocene vegetation is characterized by pollen assemblages similar to the psammophytic and halophytic communities of the Southern pampa grassland, associated with communities with more edaphic conditions. At the same time, at 38°S a sea level regression is suggested by the dominance of fresh-water pollen assemblages and micropaleontological remains. The trend toward humid, temperate conditions ca. 1000 yr B.P. suggested by vertebrate remains characteristic of temperate and humid conditions, as well as a very short but dry episode during the 18th century suggested by the geology, are not clearly evidenced in the pollen sequences. Vegetational and climatic changes are explained by the latitudinal shifts and changes in intensity of the southern atmospheric circulation and changes in sea level.