机构地区:[1]中国科学院南京地质古生物研究所,现代古生物学和地层学国家重点实验室,江苏南京210008 [2]中国科学院生物演化与环境卓越创新中心,江苏南京210008 [3]中国科学院大学地球与行星科学院,北京100049 [4]伊斯兰堡COMSATS大学(阿伯塔巴德校区)地球科学系,巴基斯坦阿伯塔巴德市22060
出 处:《地层学杂志》2023年第3期339-352,共14页Journal of Stratigraphy
基 金:第二次青藏科考研究国家专项(2019QZKK0706);国家自然科学基金(41921002、42002024);中国科学院战略性先导科技专项(XDB26000000)共同资助。
摘 要:小壳化石是寒武系纽芬兰统年代地层划分和全球对比的主要生物地层学依据。长期以来,喜马拉雅西侧的巴基斯坦北部寒武纪早期小壳化石的发现较为零星,导致该地区埃迪卡拉纪与寒武纪过渡期地层序列的划分缺乏统一认识,相关地层时代归属十分不清晰。在第二次青藏科考任务的支持下,作者对巴基斯坦北部隶属于小喜马拉雅区的Hazara盆地东部前寒武纪与寒武纪过渡期地层Hazara组、Kakul组、Abbottabad组和Hazira组开展详细研究,首次在Kalu-di-Bandi剖面Abbottabad组Sirban段顶部硅磷质白云岩中发现了寒武纪纽芬兰世幸运期小壳化石组合。该小壳化石组合属种相对丰富,含有Anabarites trisulcatus、Protohertzina anabarica、Conotheca subcurvata、Hexangulaconularia formosa、Olivooides multisulcatus、Maikhanella pristinis、Lopochites latazonalis、Siphogonuchites sp.及Spirellus columnaris等分子。上述属种组合面貌常见于华南、印度北部、克什米尔、伊朗、蒙古国及西伯利亚的寒武纪纽芬兰世幸运期地层中,其中A.trisulcatus和P.anabarica是这一化石组合带中的标准分子。因此,本文以A.trisulcatus和P.anabarica的共同出现为标志,将Sirban段顶部的小壳化石组合命名为Anabarites trisulcatusProtohertzina anabarica组合带,时代上归属为寒武纪纽芬兰世幸运期。该化石组合的发现表明,该地区存在寒武纪幸运期地层记录,寒武系底界应位于Abbottabad组Sirban段内某个层位(不过确切的界线位置仍需将来进一步的生物地层学和化学地层学工作进行校对),同时也修正了前人将该地区寒武系底界置于Hazira组与Abbottabad组界线处或Abbottabad组与Kakul组界线处的观点。对比研究发现,Sirban段中的化石组合分子与华南A.trisulcatus-P.anabarica组合带面貌非常相似,且共有一些特征属种,支持寒武纪纽芬兰世印度次大陆北部的喜马拉雅区与华南之间的生物群存在�Small Shelly Fossils(SSFs)are globally distributed across various continents in the early Cambrian and especially critical for the Terreneuvian biostratigraphic subdivision and correlation.However,the early Cambrian SSFs remain least documented from the Western Himalaya in North Pakistan,which has apparently restricted the establishment of a credible early Cambrian chronostratigraphic framework in this region.During the second Tibetan Plateau scientific expedition in the Hazara Basin constituting the Lesser Himalayan zone in the North Pakistan,we systematically observed and sampled the Precambrian-Cambrian strata including Hazara,Kakul,Abbottabad and Hazira formations.Herein,we report the first discovery of an early Terreneuvian SSF fauna from one thin interval dominated by cherty-phosphatic dolostone in the upper part of the Sirban Member of the Abbottabad Formation at the Kalu-di-bandi Section in the Hazara Basin.This relatively abundant SSF fauna includes Anabarites trisulcatus,Protohertzina anabarica,Conotheca subcurvata,Hexangulaconularia formosa,Olivooides multisulcatus,Maikhanella pristinis,Lopochites latazonalis,Siphogonuchites sp.and Spirellus columnaris.These fossils are common components in the earliest Terreneuvian SSF assemblage worldwide which are normally marked by the first occurrence of A.trisulcatus and/or P.anabarica,such as South China,North India,Kashmir,Iran,Siberia and Mongolia.Herein,this SSF assemblage is named as the Anabarites trisulcatus-Protohertzina anabarica Assemblage Zone defined by the co-occurrence of A.trisulcatus and P.anabarica,which represents a Fortunian age of Terreneuvian.This new bio-chronostratigraphic information markedly contrasts with the previous propositions and further suggests that the base of Cambrian almost certainly lies within the upper Sirban Member of the Abbottabad Formation rather than at the boundaries of the Hazira and Abbottabad formations or the Abbottabad and Kakul formations.However,the precise horizon of the Precambrian-Cambrian boundary needs to b
关 键 词:小壳化石 生物地层 Abbottabad组 纽芬兰统 巴基斯坦 小喜马拉雅区
分 类 号:P534.41[天文地球—古生物学与地层学]
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