气候变化领域集成服务门户(CCPortal): Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation

CCPortal

DOI	10.1130/B35590.1
	Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation
	Pfeifer L.S.; Soreghan G.S.; Pochat S.; Driessche J.V.D.
发表日期	2020
ISSN	167606
起始页码	379
结束页码	392
卷号	133 期号:2021-01-02
英文摘要	Carboniferous–Permian strata in basins within the Central Pangean Mountains in France archive regional paleoequatorial climate during a unique interval in geological history (Pangea assembly, ice-age collapse, megamonsoon inception). The voluminous (μ 1.5 km) succession of exclusively fne-grained red beds that comprises the Permian Salagou Formation (Lodève Basin, France) has long been interpreted to record either lacustrine or fuvial deposition, primarily based on a local emphasis of subaqueous features in the upper μ 25% of the section. In contrast, data presented here indicate that the lower-middle Salagou Formation is dominated by up to 15-m-thick beds of internally massive red mudstone with abundant pedogenic features (microscale) and no evidence of channeling. Up-section, limited occurrences of ripple and hummocky cross-stratifcation, and mudcracks record the intermittent in-fuence of shallow water, but with no channeling nor units with grain sizes exceeding coarse silt. These data suggest that the most parsimonious interpretation for the Salagou Formation involves eolian transport of the sediment and ultimate deposition as loess in shallow, ephemeral lacustrine environments. Provenance analyses of the Salagou Formation indicate coarse-grained protoliths and, together with geochemical proxies (chemical index of alteration [CIA] and τNa) that correspond respectively to a low degree of chemical weathering and a mean annual temperature of μ 4 °C, suggest that silt generation in this case is most consistent with cold-weathering (glacial and associated periglacial) processes in the Variscan highlands. Together with previous studies that detailed voluminous Permian loess in western equatorial Pangea, this work shows a globally unique distribution of dust at low latitudes that can be linked either directly to glaciated alpine terranes or to reworked and defated deposits of other types (e.g., fuvial outwash) where fne-grained material was originally generated from glacial grinding in alpine systems. These results further support a revised model for early Permian climate, in which extratropical ice sheets coexisted with a semiarid tropics that may have hosted signifcant ice at moderate elevation. © 2020 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184847
作者单位	School of Geosciences, University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma, 73019, United States; CNRS UMR 6112, Université de Nantes, Laboratoire de Planétologie et de Géodynamique, 2 rue de la Houssinière, Nantes, F-44000, France; Université de Rennes, CNRS, Géosciences Rennes-UMR 6118, Rennes, F-35000, France
推荐引用方式 GB/T 7714	Pfeifer L.S.,Soreghan G.S.,Pochat S.,et al. Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation[J],2020,133(2021-01-02).
APA	Pfeifer L.S.,Soreghan G.S.,Pochat S.,&Driessche J.V.D..(2020).Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation.Bulletin of the Geological Society of America,133(2021-01-02).
MLA	Pfeifer L.S.,et al."Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation".Bulletin of the Geological Society of America 133.2021-01-02(2020).