南非Dwyka群冈瓦纳双晶岩冰川成因的再思考

IF 0.9 Q3 GEOLOGY
Geologos Pub Date : 2022-08-01 DOI:10.2478/logos-2022-0008
Mats O. Molén, J. Smit
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引用次数: 4

摘要

摘要冈瓦纳大陆晚古生代冰河时代可能以南非的Dwyka群最为典型。条纹和凹槽的表面或路面通常被认为是在冰下形成的,被解释为原位或改造的泥质岩也是如此。这些解释是通过对南非各地以前研究得很好的地区的露头进行调查来检验的。详细分析的重点是杂岩中石英砂颗粒上的条纹表面/路面和表面微结构。四条路面的沉积学背景被解释为冰川成因,显示出通常与沉积物重力流而非冰川作用有关的特征。共从露头中提取了4271个石英砂颗粒,这些露头被认为主要是大陆冰川作用形成的tillite。通过SEM分析,这些颗粒并没有显示出与第四纪冰川沉积物相关的破裂和不规则磨损的特征性表面微结构组合,而是主要是与多循环颗粒相关的表面微结构的混合。Dwyka群杂岩应重新解释为非冰川沉积物重力流沉积物。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Reconsidering the glaciogenic origin of Gondwana diamictites of the Dwyka Group, South Africa
Abstract The Gondwana Late Palaeozoic Ice Age is probably best represented by the Dwyka Group in South Africa. Striated and grooved surfaces or pavements are commonly considered to have formed subglacially, as are diamictites which have been interpreted as in-situ or reworked tillites. These interpretations were tested by investigation of outcrops in formerly well-studied areas, throughout South Africa. Detailed analyses have focused on striated surfaces/pavements and surface microtextures on quartz sand grains in diamictites. The sedimentological context of four pavements, interpreted to be glaciogenic, display features commonly associated with sediment gravity flows, rather than glaciation. A total of 4,271 quartz sand grains were subsampled from outcrops that are considered mainly to be tillites formed by continental glaciation. These grains, analysed by SEM, do not demonstrate the characteristic surface microtexture combinations of fracturing and irregular abrasion associated with Quaternary glacial deposits, but mainly a mix of surface microtextures associated with multicyclical grains. The Dwyka Group diamictites warrant reinterpretation as non-glacial sediment gravity flow deposits.
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来源期刊
Geologos
Geologos GEOLOGY-
CiteScore
1.70
自引率
0.00%
发文量
7
审稿时长
12 weeks
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