Dating of paleolakes in the central Altiplano of Bolivia
Dating of paleolakes in the central Altiplano of Bolivia
复制标题
DOI：
10.1016/s0031-0182(01)00301-7
复制
发表时间：
2001-08-15
影响因子：
3
通讯作者：
Féraud, G
中科院分区：
文献类型：
--
作者：
Fornari, M;Risacher, F;Féraud, G
玻利维亚高原广泛的古湖泊的沉积物对应于湖泊期和干旱期的交替，这是一种通常用气候变化来解释的现象。由于缺乏对沉积物的精确测年，无法详细重建古湖泊的演变，从而无法确定相邻盆地和当地气候条件之间相互联系的相对影响。在五个古湖泊的北方高原（的的喀喀盆地）和三个中央高原（Poopo，Coipasa和Uyuni盆地），只有两个最近的古湖泊已定。从乌尤尼盐沼采集的121米长的沉积物岩芯中含有被12个盐壳分隔的I I湖相层（L1-L11）。放射性碳测年结果表明，L1和L2与Tauca湖相（12000 ~ 16000 calyr bp）有关，L3和L4与Minchin湖相（30000 ~ 73000 calyr bp）有关。L5层位于地表以下46 m处，含有火山灰和保存完好的黑云母，其年龄由40 Ar/39 Ar法测定。测得的年龄为191 000 +/- 5000年是有史以来第一次从前明钦古湖（湖埃斯卡拉）。这一结果结合C-14和U/Th的数据从不同的作者Tauca和Minchin湖上得到的湖泊事件的持续时间在更新世定期增加。相比之下，古湖水平在北方高原下降，从最古老的已知（湖马塔罗，3950米），目前的喀喀水平（3806米）。北方和中央高原之间的门槛的逐渐侵蚀可能使大量的水从北方盆地溢出到中央高原。因此，高原中部大型古湖泊的存在不仅取决于当地的气候条件，而且还取决于来自北方的额外输入，那里的气候条件可能与南方的气候条件大不相同。(C)2001 Elsevier Science B. V.保留所有权利。玻利维亚高原上广泛的古湖泊的沉积对应于湖泊事件和干旱期的交替，这一现象通常由气候变化来解释。由于缺乏对沉积物的精确测年，无法详细重建古湖泊的演变，从而无法确定相邻盆地和当地气候条件之间相互联系的相对影响。在五个古湖泊的北方高原（的的喀喀盆地）和三个中央高原（Poopo，Coipasa和Uyuni盆地），只有两个最近的古湖泊已定。从乌尤尼盐沼采集的121米长的沉积物岩芯中含有被12个盐壳分隔的I I湖相层（L1-L11）。放射性碳测年结果表明，L1和L2与Tauca湖相（12000 ~ 16000 calyr bp）有关，L3和L4与Minchin湖相（30000 ~ 73000 calyr bp）有关。L5层位于地表以下46 m处，含有火山灰和保存完好的黑云母，其年龄由40 Ar/39 Ar法测定。测得的年龄为191 000 +/- 5000年是有史以来第一次从前明钦古湖（湖埃斯卡拉）。这一结果结合C-14和U/Th的数据从不同的作者Tauca和Minchin湖上得到的湖泊事件的持续时间在更新世定期增加。相比之下，古湖水平在北方高原下降，从最古老的已知（湖马塔罗，3950米），目前的喀喀水平（3806米）。北方和中央高原之间的门槛的逐渐侵蚀可能使大量的水从北方盆地溢出到中央高原。因此，高原中部大型古湖泊的存在不仅取决于当地的气候条件，而且还取决于来自北方的额外输入，那里的气候条件可能与南方的气候条件大不相同。(C)2001 Elsevier Science B. V.保留所有权利。
The deposits of the extensive paleolakes of the Bolivian Altiplano correspond to an alternation of lacustrine episodes and dry periods, a phenomenon commonly explained by climatic changes. The lack of precise dating of the deposits has prevented detailed reconstruction of the evolution of paleolakes that would allow a determination of the relative influence of interconnections between neighboring basins and local climatic conditions. Among the five paleolakes of the northern Altiplano (Titicaca basin) and the three of the central Altiplano (Poopo, Coipasa and Uyuni basins) only the two most recent paleolakes have been dated. A 121 m long sediment core recovered from the Salar de Uyuni contained I I lacustrine layers (L1-L11) separated by 12 salt crusts. Radiocarbon dating shows that the younger layers L1 and L2 are related to the Tauca lacustrine phase (12 000-16 000 cal yr bp) and layers L3 and L4 to the Minchin lacustrine phase (30 000-73 000 cal yr bp). Layer L5, located at 46 m below the surface, contains a volcanic ash with well-preserved biotites is here dated by the 40Ar/39Ar method. The measured age of 191 000 +/- 5000 y is the first date ever obtained from a pre-Minchin paleolake (Lake Escara). This result combined with C-14 and U/Th data obtained on lakes Tauca and Minchin from various authors suggests that the duration of the lacustrine events increased regularly during the Pleistocene. In contrast, paleolake levels in the northern Altiplano decreased from the oldest known (Lake Mataro, 3950 m) to the present Titicaca level (3806 m). A progressive erosion of the threshold between the northern and central Altiplano may have allowed important volumes of water to overflow from the northern basin into the central Altiplano. The existence of large paleolakes in the central Altiplano was thus not only dependent on local climatic conditions but also on additional inputs from the north, where climatic conditions could have been quite different from those prevailing in the south. (C) 2001 Elsevier Science B.V. All rights reserved.The deposits of the extensive paleolakes of the Bolivian Altiplano correspond to an alternation of lacustrine episodes and dry periods, a phenomenon commonly explained by climatic changes. The lack of precise dating of the deposits has prevented detailed reconstruction of the evolution of paleolakes that would allow a determination of the relative influence of interconnections between neighboring basins and local climatic conditions. Among the five paleolakes of the northern Altiplano (Titicaca basin) and the three of the central Altiplano (Poopo, Coipasa and Uyuni basins) only the two most recent paleolakes have been dated. A 121 m long sediment core recovered from the Salar de Uyuni contained I I lacustrine layers (L1-L11) separated by 12 salt crusts. Radiocarbon dating shows that the younger layers L1 and L2 are related to the Tauca lacustrine phase (12 000-16 000 cal yr bp) and layers L3 and L4 to the Minchin lacustrine phase (30 000-73 000 cal yr bp). Layer L5, located at 46 m below the surface, contains a volcanic ash with well-preserved biotites is here dated by the 40Ar/39Ar method. The measured age of 191 000 +/- 5000 y is the first date ever obtained from a pre-Minchin paleolake (Lake Escara). This result combined with C-14 and U/Th data obtained on lakes Tauca and Minchin from various authors suggests that the duration of the lacustrine events increased regularly during the Pleistocene. In contrast, paleolake levels in the northern Altiplano decreased from the oldest known (Lake Mataro, 3950 m) to the present Titicaca level (3806 m). A progressive erosion of the threshold between the northern and central Altiplano may have allowed important volumes of water to overflow from the northern basin into the central Altiplano. The existence of large paleolakes in the central Altiplano was thus not only dependent on local climatic conditions but also on additional inputs from the north, where climatic conditions could have been quite different from those prevailing in the south. (C) 2001 Elsevier Science B.V. All rights reserved.