Mid-Cretaceous desert system in the Simao Basin, southwestern China, and its implications for sea-level change during a greenhouse climate
Mid-Cretaceous desert system in the Simao Basin, southwestern China, and its implications for sea-level change during a greenhouse climate
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思茅盆地中白垩纪荒漠系统及其对温室气候下海平面变化的影响
DOI：
10.1016/j.palaeo.2016.12.048
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Wagreich Michael
中科院分区：
文献类型：
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作者：
Wu Chihua;Liu Chenglin;Yi Haisheng;Xia Guoqing;Zhang Hua;Wang Licheng;Li Gaojie;Wagreich Michael
古气候指标表明，白垩纪中期是中生代最温暖的时期之一。白垩纪中期的“超级温室”时期也经历了赤道到两极的温度梯度，远低于今天的温度梯度，这意味着大气和/或海洋的纬向热传输更大。然而，白垩纪大气环流的重建一直受到缺乏可靠的代理或直接的地质证据的基础上的相关数据集。风成沉积物提供了有关古气候的直接信息，以及大陆内部古风的方向和强度。通过对思茅盆地中白垩统满岗组的岩石学和沉积学观察，对该地区的陆相沉积进行了重新评价。最初被认为是水性沉积物，我们重新解释这些地层代表沙漠环境中的风成运输。我们认为，风成沉积在曼岗组（和同时代的地层在邻近的盆地）的发展是一个局部的响应，在中白垩纪期间，在北方半球的中低纬度地区的沙漠气候，这是占主导地位的副热带高压系统在行星尺度上。此外，随着中特提斯洋的闭合，华南、思茅和中南半岛地块的山间盆地变得更加孤立于大气环流。班公湖-怒江洋壳和伊那木板块的双向俯冲作用导致了安第斯型陆缘的发育，在东亚大陆形成了雨影效应。这些因素造成了热带沙漠气候的发展，其特点是风成沙丘和蒸发岩沉积。我们推测，通过东亚的荒漠化，地下水库的严重枯竭可能是一个以前未被认识到的触发短期海平面变化在无冰白垩纪温室间隔。
Paleoclimatic indicators suggest that the mid-Cretaceous was one of the warmest intervals of the Phanerozoic. The period of the mid-Cretaceous “super-greenhouse” also experienced an equator-to-pole temperature gradient much lower than that of the present day, implying greater meridional heat transport by the atmosphere and/or oceans. However, reconstructions of Cretaceous atmospheric circulation have been hindered by a lack of relevant datasets based on reliable proxies or direct geological evidence. Aeolian deposits provide direct information about paleoclimate, as well as the direction and intensity of paleo-wind in the interiors of continents. Using petrologic and sedimentologic observations, this study reassesses the terrestrial deposits of the mid-Cretaceous Mangang Formation in the Simao Basin of southwestern China. Originally considered to be aqueous deposits, we reinterpret these strata as representing aeolian transport in a desert environment. We suggest that the development of aeolian deposits in the Mangang Formation (and coeval strata in adjacent basins) was a local response to the prevailing desert climate in the mid- to low-latitudes of the Northern Hemisphere during the mid-Cretaceous, which were dominated by subtropical high-pressure systems on a planetary scale. In addition, with the closure of the Mesotethys Ocean, the intermontane basins of the South China, Simao, and Indochina blocks became more isolated from atmospheric circulation. Bidirectional subduction of the Bangong-Nujiang oceanic crust and the Izanagi Plate beneath East Asia led to the development of Andean-type margins, which created a rain-shadow effect in continental East Asia. These factors caused the development of a tropical desert climate, characterized by aeolian dunes and evaporite deposition. We speculate that the severe depletion of groundwater reservoirs via the desertification of East Asia may represent a previously unrecognized trigger for short-term sea-level changes during the ice-free Cretaceous greenhouse interval.