肖良^1,2,3,,
王佳楠^1,2,
国丽妍¹,
李相传^1,2,3,
何祎晨¹,
孙楠¹,
陈淑娥¹,
王青山¹
1. 长安大学地球科学与资源学院, 陕西 西安 710054
2. 现代古生物学和地层学国家重点实验室(中国科学院南京地质古生物研究所), 江苏 南京 210008
3. 陕西省早期生命与环境重点实验室(西北大学), 陕西 西安 710069

基金项目: 国家自然科学基金项目（批准号：41872017和41672156）、现代古生物学和地层学国家重点实验室（中国科学院南京地质古生物研究所）开放课题基金项目（批准号：183125和193113）、陕西省自然科学基础研究计划项目（批准号：2019JM-401）、陕西省早期生命与环境重点实验室（西北大学）开放基金项目（批准号：211827200366）和长安大学大学生创新创业训练计划项目（批准号：202110710064）共同资助


详细信息

作者简介: 肖良, 男, 41岁, 副教授, 古生物学与地层学专业, E-mail: youmu4@sina.com

中图分类号: Q915.817⁺.2;P534.63⁺1

收稿日期:2021-05-29
修回日期:2021-09-08
刊出日期:2021-11-30

Gastropods fossils from the Sanmen Formation on the western margin of the Weihe Basin and their paleoenvironmental significance

XIAO Liang^1,2,3,,
WANG Jianan^1,2,
GUO Liyan¹,
LI Xiangchuan^1,2,3,
HE Yichen¹,
SUN Nan¹,
CHEN Shue¹,
WANG Qingshan¹
1. School of Earth Science and Resources, Chang'an University, Xi'an 710054, Shaanxi
2. State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS), Nanjing 210008, Jiangsu
3. Shaanxi Key Laboratory of Early Life and Environments(Northwest University), Xi'an 710069, Shaanxi


MSC: Q915.817⁺.2;P534.63⁺1

--> Received Date: 29 May 2021
Revised Date: 08 September 2021
Publish Date: 30 November 2021


摘要
摘要:渭河盆地西缘的宝鸡陈仓区簸箕庄发育一套三门组地层，地质时代为早更新世杰拉期，其年代可能在2.60~1.95 Ma范围内。地层中保存有丰富的腹足动物化石和记录气候突变信息的标志层，是研究古生物与古环境的重要材料。本文首次对该地区三门组中保存的腹足动物化石进行了鉴定分类，共计4种：Gyraulus sibiricus（Dunker）（西伯利亚小旋螺）、Galba elegans（Ping）（雅致土蜗）、Radix niangtzeiensis（Ping）（娘子关萝卜螺）、Viviparus chengxianensis（Guo）（成县田螺）。同时，结合上述4种腹足动物的生态习性以及宝鸡陈仓区三门组的岩石与气候突变标志层（"白线"钙质层）的XRF地球化学特征，恢复宝鸡陈仓地区早更新世杰拉期的古环境，探讨环境突变对腹足动物的影响。由于早更新世杰拉期东亚冬季风的增强，西北地区干旱程度加剧，古三门湖水位下降，处于古三门湖边缘的宝鸡陈仓更容易受到湖水变化的影响。陈仓地区三门组存在两条"白线"层，指示了该地区在杰拉期发生了两次较为严重的干旱事件，导致湖泊水位下降，使腹足动物的生存环境发生了突变，造成腹足动物在该地区发生了两次集中死亡事件。而且第一次腹足动物死亡事件比第二次更加严重，说明第一次气候干旱事件更加强烈。
关键词: 腹足动物化石/
渭河盆地西缘/
三门组/
早更新世杰拉期/
古环境

Abstract:A 7.92 m Bojizhuang outcrop(34°31'33″N, 107°06'37″E) in Chencang District, Baoji, Western Weihe Basin, can be correlated to the Sanmen Formation. After synthesizing previous petrologic and chronological results of the Sanmen Formation with an assigned Early Pleistocene Gelasian age(2.60~1.95 Ma). The strata consists of 32 cyclothemic layers of earthy yellow clay stoneat the bottom to mudstone and siltstone at the middle and top. Two white colored calcareous layers with CaO content up to 56.19% wt marks the transition between mudstone and siltstone in the upper part of the section, containing abundant gastropod fossils. These fossils are assigned into four species: Gyraulus sibiricus, Galba elegans, Radix niangtseiensis, Viviparus chengxianensis. Combined with XRF principal element analysis of the calcareous sediments, these fossils revealed the impact of the Eastern Asian Winter Monsoon on local hydrology in the Weihe Basin. Under the influence of the strong uplifting of the Qinghai-Tibet Plateau, the modern monsoon-drought pattern in China had been formed and strengthened during Gelasian, resulting in further arid conditions in Northwest China and leading to the decline of water level in the ancient Sanmen lake. Two episodes of lake water level reduction, marked by the "white line" horizons of calcareous layers in the Sanmen Formation, indicate the two severe drought events resulting in two mass deaths of gastropods. Taphonomic analysis of these fossils found between the two calcareous layers suggested that more gastropods were killed during the first drought event with more severe hydrological changes. After a short period of lake water level rebound, the gastropod population recovered. But the subsequent second drought event led to a large number of deaths of gastropods again, although not as violent as the previous episode. The two local gastropod mass-killing events illustrated regional hydrological impact of the strengthening of Eastern Asian Winter Monsoon during Early Pleistocene under the global deteriorating glacier climate in the Northern Hemisphere.
Key words:Gastropod fossils/
western Weihe Basin/
the Sanmen Formation/
the Early Pleistocene Gelasian age/
paleoenvironment



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