Glacial paradoxes during the late Paleozoic ice age: Evaluating the equilibrium line altitude as a control on glaciation
Glacial paradoxes during the late Paleozoic ice age: Evaluating the equilibrium line altitude as a control on glaciation
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DOI：
10.1016/j.gr.2011.11.005
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发表时间：
2012-07
影响因子：
6.1
通讯作者：
J. Isbell;Lindsey C. Henry;E. Gulbranson;C. Limarino;M. Fraiser;Zelenda J. Koch;Patricia L. Ciccioli;Ashley A. Dineen
中科院分区：
文献类型：
--
作者：
J. Isbell;Lindsey C. Henry;E. Gulbranson;C. Limarino;M. Fraiser;Zelenda J. Koch;Patricia L. Ciccioli;Ashley A. Dineen
晚古生代冰期（LPIA）由石炭纪和二叠纪期间横跨冈瓦纳大陆的多次冰川作用组成。三个关键的时间间隔进行评估使用的概念的平衡线高度（ELA）作为控制冰川作用，提供洞察两个时间间隔的矛盾冰分布在冰川作用期间和之后。LPIA开始于阿根廷西部维塞安期间的中纬度地区，伴随着原始冰川的增长。冰川作用是由ELA以上山脉的抬升开始的。在巴什基尔，冰川消退发生在那里，而冰川开始在同一纬度与巴西巴拉那盆地有关的高地。分析表明，冰川消退的Protocordillera发生由于伸展崩溃的范围低于ELA在向西移动的板块俯冲的位置。在晚宾夕法尼亚-早二叠世高峰期冰川的LPIA，广泛的glacimarine存款表明，冰川达到海平面，这对应于一个主要的降低ELA由于全球变冷。最后，在LPIA的早期到早期晚期的过渡期间，极地冈瓦纳没有冰川。然而，三个冰期发生在中高纬度地区在澳大利亚东部从Sakmarian到Capitanian/最早的Wuchiapingian。在这些事件中全球变冷的程度是有争议的，因为有证据表明南极洲南极的无冰条件和ELA升高。这表明，严重的全球变冷不是最后三次澳大利亚冰川的原因，而是澳大利亚东部特有的与ELA相关的条件驱动了这些晚期事件。澳大利亚冰川形成的可能原因包括：1）海岸上升流产生的异常寒冷条件，2）允许冰川成核的高地的存在，3）pCO 2水平的波动，以及4）由于该地区位于副极地低压带而增加的降水。
The late Paleozoic ice age (LPIA) consists of multiple glaciations that waxed and waned across Gondwana during the Carboniferous and Permian. Three key intervals are evaluated using the concept of the equilibrium-line altitude (ELA) as a control on glaciation to provide insight into two intervals of paradoxical ice distribution during and following glaciation. The LPIA began in the mid-latitudes during the Viséan in western Argentina with the growth of glaciers in the Protoprecordillera. Glaciation was initiated by uplift of the range above the ELA. In the Bashkirian, deglaciation occurred there while glaciation was beginning at the same latitude in uplands associated with the Paraná Basin in Brazil. Analysis suggests that deglaciation of the Protoprecordillera occurred due to extensional collapse of the range below the ELA during a westward shift in the location of plate subduction. During Late Pennsylvanian–Early Permian peak glaciation for the LPIA, extensive glacimarine deposits indicate that glaciers reached sea level, which corresponds to a major lowering of the ELA due to global cooling. Finally, during the Early to early Late transition out of the LPIA, polar Gondwana was unglaciated. However, three glacial intervals occurred at mid- to high-latitudes in eastern Australia from the Sakmarian to the Capitanian/earliest Wuchiapingian. The magnitude of global cooling during these events is debatable as evidence indicates ice-free conditions and an elevated ELA at the South Pole in Antarctica. This suggests that severe global cooling was not the cause of the final three Australian glaciations, but rather that ELA-related conditions specific to eastern Australia drove these late-phase events. Possible causes for the Australian glaciations include: 1) anomalous cold conditions produced by coastal upwelling, 2) the presence of uplands allowing nucleation of glaciers, 3) fluctuations in pCO2levels, and 4) increased precipitation due to the location of the area in the subpolar low pressure belt.