粤北丹霞盆地晚白垩世丹霞组沉积相及古气候意义
- 1. 东华理工大学省部共建核资源与环境国家重点实验室, 南昌 330013;
- 2. 东华理工大学地球科学学院, 南昌 330013
基金项目:
国家自然科学基金项目（41602113，41772197）；韶关市丹霞山管理委员会科学研究项目（DXSGEO2017001）；东华理工大学省部共建核资源与环境国家重点实验室开放基金项目（NRE1605）
作者简介:
陈留勤,男,1983年出生,博士,副教授,沉积学,E-mail:liuqincheen@163.com
- 收稿日期:
2018-02-08
- 修回日期:
2018-03-19
- 刊出日期:
2019-02-10
摘要: 粤北丹霞山作为世界自然遗产“中国丹霞”的典型代表，在地貌方面已经积累了丰富的研究成果，但是对丹霞地貌成景地层（晚白垩世红层）的沉积环境和古气候的研究较少。通过对巴寨剖面丹霞组的野外观测、砾石统计、室内砂岩样品薄片鉴定及粒度分析，进行详细的沉积相研究。巴寨剖面丹霞组出露巴寨段和锦石岩段，前者以砾岩为主，发育粒序层理及平行层理、底侵蚀面、叠瓦状构造等，而后者以发育大型交错层理的风成砂岩夹古土壤为特征。在盆地其他位置，可见丹霞组白寨顶段砾岩地层。研究结果表明，在巴寨剖面的晚白垩世丹霞组红层中，可以识别出正粒序层理砾岩、逆粒序层理砾岩、平行层理砾岩、无沉积构造砾岩、大型交错层理风成砂岩、中—薄层砂岩、古土壤7种岩相。巴寨段砾石大小主要为0.5~9.5 cm，成分以脉石英、石英砂岩及砖红色砂岩为主。锦石岩段砂岩粒径为0.03~0.5 mm，分选性好，以跳跃组分为主，指示风成环境。丹霞组从巴寨段到锦石岩段沉积物粒度变细、沉积速率由快变慢，指示了由河流主导的冲积扇沉积体系向沙漠沉积体系的转变，反映了古气候向干热变化，锦石岩段的风成砂岩可能与东亚中纬度地区晚白垩世Campanian期古气候广泛的干旱化有关。丹霞组沉积末期（白寨顶段），古气候条件再次变湿，降水增加，河流将粗粒碎屑物再次搬运到盆地发生沉积，新的冲积扇叠覆在锦石岩段风成砂岩—古土壤序列之上。
Facies Analysis and Paleoclimate Implications of the Late Cretaceous Danxia Formation in the Danxia Basin, Northern Guangdong Province, South China
- 1. State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China;
- 2. School of Earth Sciences, East China University of Technology, Nanchang 330013, China
Funds:
National Natural Science Foundation of China, No. 41602113, 41772197; Scientific Research Fund from the Danxiashan Committee, No. DXSGEO2017001; Open Research Fund from the State Key Laboratory of Nuclear Resources and Environment (East China University of Technology), No. NRE1605
- Received Date:
2018-02-08
- Rev Recd Date:
2018-03-19
- Publish Date:
2019-02-10
Abstract: The Danxiashan of northern Guangdong province is representative of the World Natural Heritage site of "China Danxia". Previous studies were predominantly focused on description of landforms in the Danxiashan UNESCO Global Geopark. Little is known about depositional environments and paleoclimate during the formation of the Late Cretaceous redbeds, which are the bedrock of the Danxia landscapes. The Danxia Formation is further subdivided into three members. The first (Bazhai) and the second (Jinshiyan) members are outcropped at the measured Bazhai Section. The former is dominated by conglomerates with graded and parallel beddings and imbricated structures, whereas the latter is characterized by large-scale cross-bedded aeolian sandstones with paleosol interbeds. The third (Baizhaiding) member consists largely of conglomerate beds and was observed at other outcrops in the basin. Detailed stratigraphic column measurement, pebble counting, and petrographic and grain size analysis were performed to understand lithofacies changes in the Bazhai Section. The results show that seven lithofacies were recognized in the Danxia Formation: normal graded conglomerate, inverse graded conglomerate, parallel bedding conglomerate, structureless conglomerate, large-scale cross-bedded aeolian sandstone, medium- to thin-bedded sandstone, and paleosol. The pebbles of the Bazhai Member range from 0.5 cm to 9.5 cm in diameter and are mainly composed of quartzite, quartz sandstone, and brick-red sandstone. The grains of the sandstone samples from the Jinshiyan Member are 0.03-0.5 mm in diameter, well sorted, and dominantly consist of a saltation population, indicating aeolian environments. Therefore, lithofacies differences from the Bazhai to the Jinshiyan Members of the Danxia Formation are possibly indicative of a change from a stream-dominated alluvial fan system with higher deposition rate to an aeolian system, which in turn is considered as recording a paleoclimatic transformation from semi-humid to very arid conditions. The red aeolian sandstone-paleosol succession of the Jinshiyan Member might be linked with broad aridity in the middle latitudes of East Asia during the Campanian Stage. The Baizhaiding Member, the uppermost part of the Danxia Formation, is again characterized by conglomerate beds, which probably suggests a paleoclimate change towards semi-humid conditions. The abundant coarse clasts were transported to the basin by streams because of increased precipitation, reflecting new alluvial fans overlying on the aeolian sandstones and paleosols of the Jinshiyan Member.
陈留勤, 李鹏程, 郭福生, 刘鑫, 李馨敏. 粤北丹霞盆地晚白垩世丹霞组沉积相及古气候意义[J]. 沉积学报, 2019, 37(1): 17-29. doi: 10.14027/j.issn.1000-0550.2018.118
CHEN LiuQin, LI PengCheng, GUO FuSheng, LIU Xin, LI XinMin. Facies Analysis and Paleoclimate Implications of the Late Cretaceous Danxia Formation in the Danxia Basin, Northern Guangdong Province, South China[J]. Acta Sedimentologica Sinica, 2019, 37(1): 17-29. doi: 10.14027/j.issn.1000-0550.2018.118
| Citation: |
CHEN LiuQin, LI PengCheng, GUO FuSheng, LIU Xin, LI XinMin. Facies Analysis and Paleoclimate Implications of the Late Cretaceous Danxia Formation in the Danxia Basin, Northern Guangdong Province, South China[J]. Acta Sedimentologica Sinica, 2019, 37(1): 17-29. doi: 10.14027/j.issn.1000-0550.2018.118
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