Génesis Comparativa de Bioconcreciones: Implicaciones Paleoambientales
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COMPARATIVE GENESIS OF BIOCONCRETIONS: PALEOENVIRONMENTAL IMPLICATIONS. The aim of this study is to describe and morphogenetically and environmentally compare bioconcretions found in a continental environment at Quequén Salado with those found in a coastal environment at Playa Chica; both localities are in Buenos Aires Province. The first section —on the bank of the Quequén Salado river— is a 1.80 m thick bed of a late Pleistocene—Holocene siltstone with a sand to clay grain-size. These bioconcretions reach up to 25 cm long and variable diameters ranging from 1 to 5 cm. They are vertically oriented with ascending branches and associated with frustules of freshwater diatoms. The second analyzed profile is located at Playa Chica, on the northern shores of the Río Negro. The 2.40 m thick layer with bioconcretions is divided into 5 to 10 cm with subhorizontally laminated rhythmite-like beds at very low angle. The BC are yellowish to dark-reddish brown in color, subcircular, well-consolidated, accompanied by marine to brackish-water diatoms, euryhaline ostracods and foraminifera. Regarding the origin of the bioconcretions it was possible to establish that the Quequén Salado concretions were originated in a seasonally flooded, fluvial environment dominated by groundwater fluctuations. The Playa Chica bioconcretion deposits show wet periods with a stable water table. The sequence of several bioconcretion layers with successive growth is evidence of changing conditions with flooding and drainage of marine water levels in the basin, within a period of increasing aridity.Three new species of cytheracean ostracodes-Cytherura? mainensis (Holocene and Pleistocene), Munseyella atlantica (Holocene), and M. mananensis (Holocene and Pleistocene)-and their distributions are described. Munseyella is reported from the Holocene off northeastern North America for the first time, and its soft parts are described and illustrated, also for the first time.
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Based on the analyses of grain size,magnetic susceptibility,sporopollen,foraminifera,lithology and AMS14C from SC1 core in Chenghu Lake,this paper discusses the evolutions of climate and paleoenvironment since Late Pleistocene.The records of sporopollen show that climate is accord with the world's: warm-wet during the Late Pleistocene,a cool and dry climate during the last glaciation,warm-wet in the Early Holocene,a hot-wet climate in the Middle Holocene,cool-dry to warm-moist during the Late Holocene;Two marine invasion events are discovered,one is Gehu during Late Pleistocene and the other is Zhenjiang in the Middle Holocene.This district has undergone great palaeogeographic changes since Late Pleistocene: rivers in the Late Pleistocene,rivers and marshlands during the last glaciation,flood plain-estuary during the Early Holocene,estuary-shallow marine in the Middle Holocene,lakes and marshlands during the Late Holocene.
Holocene climatic optimum
Lithology
Marine transgression
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Based on the analyses of grain size,sporopollen,foraminifera,AMS14 C and OSL dating from LH01Core in the Northern Liaodong Bay,the evolutions of climate and paleoenvironment since Late Pleistocene are discusses in this paper.LH01Core has undergone great palaeogeographic changes since Late Pleistocene:rivers and lakes in the Late Pleistocene,marine and lands during the Early Holocene,shallow marine in the Middle Holocene,estuary shallow marine during the Late Holocene.The records of sporopollen show that climate:cool-dry during the Late Pleistocene,cool-wet during the Late Pleistocene, cool-wet in the Early Holocene,hot-wet in the Middle Holocene,hot-dry in the Middle Holocene,warmdry during the LateHo locene.PanShan invasion event is discovered aboaut 7.5ka BP in LH01Core.
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过去的 13000 一 from 胡古安吉安·马尔·莱克的一个高分辨率的花粉记录在 Holocene 期间在南部的中国揭示植被和环境变化。它证明树和灌木的那个(i) 花粉百分比在早 Holocene 期间到达了 56%(11600—7800 cal BP ) ，哪个热带树的花粉百分比在 9500 点到达了最大值—8000 cal BP，反映热、湿的环境；(i i ) 在 mid-Holocene 期间(7800—4200 cal BP ) ，当热带副热带的树的百分比减少了时，山区的具球果的树和植物的花粉百分比增加了，显示降低温度和湿度；(iii ) 从 4200 ～ 350 在迟了的 Holocene 跨越 BP，植物的花粉百分比和山区的针叶树显著地增加了的 cal，显示温度和湿度的显著减少。我们的花粉数据揭示时间时期 9500—在南部的中国的 BP 代表的 8000 cal 为 Holocene 的气候的最佳由热、湿的条件描绘了。这与 Holocene 最佳全球性在更低的纬度区域发现了一致。我们推测那个强壮的曝晒力量原因向北方 ITCZ 和副热带的夏天季风前面的移植，它在 Huguangyan 区域导致了早 Holocene 最佳。中间、迟了的 Holocene 的干燥趋势和气候变化能在太阳的曝晒和经常的 ENSO 事件与减少被联系。
Intertropical Convergence Zone
Holocene climatic optimum
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在为硅藻，种子和 phytoliths 的 Tianluoshan 的古老的稻田的节的考古学的分析证明了在东方中国的最高本地的海水平在 Holocene 期间出现在 7.0 ka BP 前。进入 Mid-Holocene，作为海水 regressed，一个广阔沼泽地平原出现在沿海的区域，在过时的 Hemudu 文化的农民栽培了米饭的地方。然而，仍然在 Mid-Holocene 有几个海平面的变化，哪个最大从 6.4 ～ 6.3 ka BP 并且从 4.6 ～ 2.1 ka BP。另外在沼泽地草植被统治的时期， 6.3 ～ 4.6 ka BP，更小的变化显然在回来上把海岸线推到陆地。尽管与这些海岸线违反联系的海平面的上升没有最高的海的紧张，铺平时期，将仍然生活和住在这个区域的人的生产活动上有深刻影响。从在 Tianluoshan 的古老的稻田的考古学的证据证明更大的海平面的上升事件推了海水到土地上并且淹没而更弱的海平面的上升事件沿着河导致了海水的侵入，在大米在土壤咸度和减少引起增加产出的稻田的大区域。米饭耕作上的海平面的上升的影响在本地饮食引起了变化。在米饭生产掉落了的区域，聚在一起并且狩猎的流行升起了。在早 Holocene 的高海层次暗示在东方沿海的平原的米饭耕作的起源是可能的在小附近的山盆。
Holocene climatic optimum
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Several assumptions on the size of the African aurochs have been tested primarily using measurements assembled from the literature. During the Holocene, the African aurochs was indeed smaller than its European and Near Eastern cousins and it appears also to have been more gracile. The available African aurochs measurements of this period probably derive mostly from male animals, since many females may have been misidentified as domestic cattle. Therefore, the degree of sexual dimorphism remains unknown, although iconographic evidence suggests that it may have been marked. Male Holocene aurochs probably reached a height of about 160 cm at the withers and is not taller than Pleistocene female aurochs, which grew to between 140 and 160 cm. The height at the withers of the Pleistocene male individuals is estimated at between 150 and 170 cm. As in Europe, the aurochs in Africa underwent a size decline between the Pleistocene and the Holocene. The Pleistocene African aurochs moreover seems to have been more robust than its Holocene successor.
Sexual dimorphism
Withers
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Shiyang 河排水盆位于亚洲季风区域的西北边缘。以前的研究在盆关于 Holocene 气候的变化得出了不同结论。一些研究建议 Holocene 气候的变化被亚洲季风主要控制并且气候在早 Holocene (11.67.1 cal ka BP ) 期间是相对潮湿的。另外的研究发现 mid-Holocene 气候的最佳(7.05.0 cal ka BP ) ，并且这个气候条件类似于在干旱中亚的 Holocene 西的风模式。现代气候被亚洲季风和西的风在排水盆影响，并且 Holocene 气候的记录显示出二不同 Holocene 气候的 patternsa 西的风模式和 monsoonal 模式。然而，什么引起了二不同 Holocene 气候的模式在这个区域共存，仍然保持不清楚。palynological 记录是为在盆的 Holocene 气候的变化的主要证据。这份报纸为排水盆的不同部分集中于 palynological 记录。在他们之中， QTH02， QTL-03 和 Sanjiaocheng 记录位于终端湖，并且 Hongshuihe 记录位于盆的中间的活动范围。在终端湖， QTH02 和 QTL-03 的 palynological 记录是类似的，但是 Sanjiaocheng 记录不同。差别被可变花粉集合主要在湖盆的不同地点影响。从四个 palynological 记录的比较和合成，我们断定千年规模的 Holocene 气候的变化被亚洲季风和西的风的联合效果在排水盆影响，它在亚洲季风的西北边缘显示出复杂 Holocene 气候的模式。
Holocene climatic optimum
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This article notes that stone artefacts often provide the only means for identifying sites, reconstructing behaviour and determining cultural affiliation in West and Central Africa. For the period covering the end of the Pleistocene and early Holocene, lithic industries can be grouped into two broad technological traditions, the Lupemban–Tshitolian assemblages and microlithic quartz industries. Even if different human populations would leave different signatures in their material culture and, more specifically, their stone tools, the current distribution of western and eastern hunter-gatherers in the Central African forest is not reflected in the Pleistocene or Holocene distribution of the two broad technological complexes. Meanwhile, a combination of poor access to and conservation of raw material may explain the absence of evidence in the forests of the central Congo basin.
Stone tool
Stone Age
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The paper brings geomorphological characteristic of Neogene sediments and Pleistocene terraces of the Berounka (the left tributary to the Vltava). The localities of Neogene fluvial and fluvial-lacustrine sediments of Lower Miocene Age are clean-cut and neotectonically dislocated. The Pleistocene terraces (13 levels in 7 groups), diverging downstream, have been incorporated into the stratigraphical Pleistocene system.
Neogene
River terraces
Early Pleistocene
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