华南腹地茶永盆地白垩系古沙漠床沙构型定量重建与启示^*

Quantitative reconstruction and implications of the Cretaceous Aeolian bedform architecture in Chayong Basin,the hinterland of South China

摘要

华南腹地茶永盆地白垩系发育古沙漠沉积,其沙丘构型特征多样,是构造活动、地下水文条件和古气候演变等多因素的综合结果,然而目前在该方面的研究却近乎空白,制约了对华南腹地古沙漠环境演变规律的认识。本研究将粒度端元分析(EMMA)新方法和沙丘构型分析传统方法相结合,开展古沙漠形态学研究及床沙构型定量重建工作。结果表明,华南腹地茶永盆地白垩纪沙漠沙丘规模较大,各项沙丘形态参数均远超全球典型断陷盆地的古沙丘均值,可以类比鄂尔多斯盆地白垩系古沙丘或塔克拉玛干沙漠的现代沙丘,指示茶永盆地的初始状态可能为一个大型干旱或沙漠盆地; 通过粒度端元四组分识别出风成沙丘、沙席和潮湿丘间(泥滩)等沉积环境类型。基于沙丘构型重建,恢复古风向为N-NE向,受北半球西风带控制,且该沉积构型记录了复合新月形沙丘、复杂(爬升)横向沙丘等多种形态类型。茶永盆地南部风成序列为干燥—潮湿型丘间风成体系,表现为内部干旱—潮湿丘间沉积与小—中型新月形沙丘的叠置; 盆地北部风成序列发育干燥型丘间风成体系,发育巨型(爬升)叠加复合沙丘。茶永盆地周缘地区的构造隆升与水系发育,为盆地带来大量沉积物源,并在风力作用下发生二次侵蚀、迁移和堆积; 断—拗陷盆地基底下沉、潜水面的升降,为风成沉积物的累积和保存创造了可容纳空间。该研究从风成沉积地质记录分析出发,提出了茶永盆地白垩纪沙漠沙丘规模可能较大的新见解,加深了对华南腹地风成/水成沉积—盆地构造—古气候等多要素耦合过程的理解。

Abstract

The Cretaceous strata in the Chayong Basin,located in the hinterland of South China,are characterized by ancient desert sediments with diverse dune morphology. These features reflect a complex interplay of tectonic activity,hydrological conditions,and palaeoclimatic changes. Despite their significance,research on this topic remains limited,hindering our understanding of the evolution of the paleodesert environment. This study employs the innovative End-Member Modeling by Grain Size Analysis(EMMA)with traditional dune morphology analysis to investigate paleoaeolian morphologies and quantitatively reconstruct bedform configurations. The results indicate that the Cretaceous dunes in the Chayong Basin are exceptionally large,with morphological parameters surpassing global averages for typical fault basins. This suggests an initial arid or desert basin state comparable to the Cretaceous dunes of the Ordos Basin’s or the modern dunes of the Taklamagan Desert. EMMA identified four end-members that are indicative of aeolian dunes,sand sheets,and moist interdune areas. The reconstructed paleowind direction was predominantly north-northeast,influenced by the westerlies of the Northern Hemisphere. The sedimentary configurations exhibit a variety of forms,including compound crescentic and complex transverse dunes. The southern part of the basin is characterized by a dry-moist interdune system,presenting internal arid-moist interdunes and small-medium crescentic dunes. In contrast,the northern part develops a dry interdune aeolian system dominated by giant compound dunes. Tectonic uplift and fluvial development surrounding the basin have provided abundant sediment sources,resulting in secondary erosion,migration,and deposition driven by wind action. The subsidence of the fault-basin basement and fluctuations in the groundwater table,has created accommodation space for the accumulation and preservation of aeolian sediments. This study,based on aeolian sedimentary geological records,offers a new perspective on the large-scale dynamics of the Chayong Basin during the Cretaceous period,enhancing our comprehension of the coupled processes of aeolian/fluvial sedimentation,basin tectonics,and paleoclimatic evolution in the hinterland of South China.

关键词

沙漠 / 床沙构型 / 白垩系 / 茶永盆地 / 华南

Key words

desert / bedform architecture / Cretaceous / Chayong Basin / South China

基金资助

*湖南省自然科学基金项目(编号: 2021JJ30388)、 中国地质调查局古生物与地质环境演化湖北省重点实验室开放基金(编号: PEL-202203)、 湖南省地质院科研项目(编号: HNGSTP202322)和湖南省创新型省份科普专题(编号: 2022ZK4207)共同资助