Upper Campanian Paleogene from the Rio Turbio coal measures in southern Argentina: Micropaleontology and the Paleocene/Eocene boundary
Upper Campanian Paleogene from the Rio Turbio coal measures in southern Argentina: Micropaleontology and the Paleocene/Eocene boundary
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DOI：
10.1016/s0895-9811(97)00015-1
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发表时间：
1997-03-01
影响因子：
1.8
通讯作者：
Carames, A
中科院分区：
文献类型：
--
作者：
Malumian, N;Carames, A
Austral盆地的Rio Turbio煤系地区是阿根廷少数几个在厚海相层序内记录白垩纪/古近纪和古新世/始新世边界而没有重大构造扰动的地区之一。700多个上白垩统和古近系样品，从露头和地下，进行了调查的微体化石。记录的浅环境，不适合南极元素，导致以下大多是低多样性的底栖有孔虫组合的认可。在Cerro Cazador组的下部，Hoplitoplacenticeras动物群（早期Campanian）与Miliammina，Haplophragmoides sp. cf. walteri和Reticulophragmium sp.组合，主要由凝集有孔虫组成。在中部和Arabconitic部分，包含摩利斯动物群，Coryphostoma incrassata Arabitea组合，由高比例的钙质和底栖物种，表明一个显着的环境变化，它代表了一个Maestrichtian海侵插曲，笼罩着所有的巴塔哥尼亚盆地。在上覆的Cerro Dorotea组中，Buliminella isabelleana procera组合是唯一一个含有反褶有孔虫的组合：Parasubbotina pseudobulloides，Danian时代。不整合的上覆Rio Turbio组（主要是中始新世）含煤岩系，包含Karreria pseudoconvica和Bythocypris sp.组合，位于下段，Boltovskoyella argentinensis是上段的特征。形成Cerro Dorotea/Rio Turbio接触与古新世/始新世边界相吻合，并与古近纪气候最佳相关的高岭石含量峰值相一致。这种不整合接触的原因尚不清楚，因为该边界没有主要的岩浆活动，这与整个巴塔哥尼亚的普遍海退有关。Rio Turbio组是不整合的，其上覆有Rio Guillermo组的厚河流砾岩，这是印加期地壳运动的结果。Rio Guillermo被非海相Rio Leona地层（上始新世-下渐新世）覆盖，不整合地被巴塔哥尼亚新生代海侵期间沉积的海相Rio Centinela地层（上渐新世-下中新世）覆盖。(C)1997年由Elsevier Science Ltd.出版
The Rio Turbio coal measures area, Austral Basin is one of the few areas in Argentina that records the Cretaceous/Paleogene and Paleocene/Eocene boundaries within a thick marine sequence without major tectonic disturbances. More than 700 Upper Cretaceous and Paleogene samples, from outcrops and subsurface, were investigated for microfossils. The shallow environments recorded, unsuitable for planktonic elements, led to recognition of the following mostly low diversity benthic foraminiferal assemblages. In the lower part of the Cerro Cazador Formation, the Hoplitoplacenticeras fauna (Early Campanian) is associated with the Miliammina, the Haplophragmoides sp. cf. walteri and the Reticulophragmium sp. Assemblages, mostly composed of agglutinated foraminifera. In the middle and glauconitic part, containing the Moorites fauna, the Coryphostoma incrassata gigantea Assemblage, composed a high percentage of calcareous and infaunal species, suggests a marked environmental change and it represents a Maestrichtian transgressive episode that hooded all the Patagonian basins. In the overlying Cerro Dorotea Formation the Buliminella isabelleana procera Assemblage is the only one which contains planktonic foraminifera: Parasubbotina pseudobulloides, of Danian age. The unconformable overlying Rio Turbio Formation (mostly Middle Eocene) bearing coal measures, contains the Karreria pseudoconvexa and Bythocypris sp. Assemblage in the lower Member, and Boltovskoyella argentinensis characterize the upper Member. The formational Cerro Dorotea/Rio Turbio contact coincides with the Paleocene/Eocene boundary and with a kaolinite content peak related to the Paleogene climatic optimum. The cause or causes of this unconformable contact ate not clear, because no major magmatic activity is known for this boundary, which is associated with a generalized regression in all Patagonia. The Rio Turbio Formation is unconformable overlain by thick fluvial conglomerates of the Rio Guillermo Formation, as a result of the Incaic diastrophic Phase. The Rio Guillermo is overlain by the non-marine Rio Leona Formation (Uppermost Eocene-Lower Oligocene) and unconformable overlaid by the marine Rio Centinela Formation (Uppermost Oligocene-Lower Miocene) deposited during the major Cenozoic transgression in Patagonia. (C) 1997 Published by Elsevier Science Ltd.