The Petrology and Origin of the Lafayette Gravel Part 2. Geomorphic History
The Petrology and Origin of the Lafayette Gravel Part 2. Geomorphic History
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拉斐特砾石的岩石学和起源第 2 部分：地貌历史
DOI：
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发表时间：
1955
期刊：
影响因子：
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通讯作者：
P. E. Potter
中科院分区：
文献类型：
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作者：
P. E. Potter
与H. N.根据菲斯克的研究，史密斯兰河和密西西比湾最高部分的高表面下的拉法叶砾石中的重矿物和长石含量确定了它的冰前时代。地文学证据表明是上新世。据信，砾石沉积是由造陆抬升而不是晚第三纪气候变化或地壳运动引起的。一般来说，与密西西比河谷上游类似的孤立沉积物有关，密西西比湾头的冲积扇沉积物受到地文位置的青睐。扇形的位置和规模在一定程度上控制了田纳西河、密西西比河和坎伯兰-俄亥俄河的壕沟位置。随后的侵蚀使这些扇形体的面积减少到原来的大约21%，并部分切割了砾石的现有表面。
Contrary to the views of H. N. Fisk, the heavy-mineral and feldspar content of the Lafayette gravel underlying the Smithland and higher surfaces of the uppermost portions of the Mississippi embayment definitely establishes its preglacial age. Physiographic evidence indicates a Pliocene age. Epeirogenic uplift rather than late Tertiary climatic change or eustatism is believed to have initiated gravel deposition. Related in a general way to the similar, isolated deposits of the upper Mississippi Valley, alluvial fan deposits at the head of the Mississippi embayment were favored by physiographic position. The location and magnitude of the fans in part controlled the entrenchment positions of the Tennessee, Mississippi, and Cumberland-Ohio rivers. Subsequent erosion has reduced the fans to approximately 21 per cent of their original area and in part cut the present surfaces on the gravels.