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首页> 外文期刊>Stratigraphy >New palynological data from the Upper Ordovician of the Precordillera Basin, Argentina: A potential key for understanding the geological history of the Precordillera terrain
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New palynological data from the Upper Ordovician of the Precordillera Basin, Argentina: A potential key for understanding the geological history of the Precordillera terrain

机译：来自阿根廷Precordillera盆地上奥陶纪的新孢粉数据：了解Precordillera地形地质史的潜在关键

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摘要

Biostratigraphic data from the Precordillera Basin have traditionally been analyzed to contribute to the understanding of its biogeographic evolution as an allochthonous microcontinent accreted to the western Gondwanan margin in the Middle-Late Ordovician. The first palynological data from Late Ordovician units of the eastern Precordillera are incorporated in an attempt to better constrain the timing of the collision. The Las Vacas Formation has previously been assigned to the Sandbian (gracilis-bicornis zones). Chitinozoans from the Las Vacas Formation are poorly diversified. The basal part of this unit contains Lagenochitina sp. cf. baltica, previously recorded in the late Darriwilian of Precordillera and the late Darriwilian-early Sandbian of eastern Canada. The assemblages from its upper part contain primarily Spinachitina bulmani, Cyathochitina sp. cf. kuckersiana, Cyathochitina sp. aff. macastyensis, and Desmochitina minor form typica. The lower-upper part of this formation also yields Kalochitina multispinata. Acritarchs are poorly preserved and the few recognized genera are not biostratigraphically significant. Cryptospore findings contribute to the record of evidences for land plants in the Ordovician of Argentina and suggest that the upper part of the unit was deposited proximal to the shoreline. The lower part of the Trapiche Formation contains a few poorly preserved chitinozoans, acritarchs and algae (cf. Gloeocapsomorpha sp.), probably due to reworking of the material. The basal chitinozoan assemblage could indicate that the deposition of the Las Vacas Formation started during the Middle-Late Ordovician (late Darriwillian-basal Sandbian). Typical Katian chitinozoans from the uppermost part of the Las Vacas Formation indicate that these deposits would have reached the middle Late Ordovician. Palynological studies seem to be a useful tool to contribute to the biostratigraphic knowledge of controversial terrains, such as the Precordillera.
机译：传统上，对Precordillera盆地的生物地层数据进行了分析，以有助于了解其生物地理演化，因为该物种是奥陶纪中晚期冈多瓦南缘增生的异源微大陆。为了更好地限制碰撞时间，尝试合并了东部前柏奥陶纪晚期奥陶纪单元的第一笔孢粉数据。拉斯·瓦卡斯编队以前曾被分配给桑迪比亚（gracilis-bicornis区）。来自拉斯·瓦卡斯组的千岁动物的多样性很差。这个单位的基础部分包含Lagenochitina sp。 cf. baltica，先前记录在Precordillera的Darriwilian晚期和加拿大东部的Darriwilian-Sandbian早期。从顶部开始的组合主要包含菠菜棘，Cyathochitina sp。 cf.克索亚斯纳（Cyathochitina sp。） aff。 macastyensis和Desmochitina次要型。该地层的下部上部也产生了Kalochitina multispinata。头针保存不佳，少数公认的属在生物地层学上不重要。隐孢子虫的发现有助于记录阿根廷奥陶纪的陆地植物，并表明该单元的上部沉积在海岸线附近。特拉皮切地层的下部包含一些保存较差的几丁质动物，顶头动物和藻类（参见Gloeocapsomorpha sp。），这可能是由于该材料的再加工所致。基底的甲壳动物组合可能表明拉斯瓦卡斯组的沉积始于中晚期奥陶纪（达里维利安基底桑地亚晚期）。来自拉斯·瓦卡斯组最上层的典型的凯蒂奇诺奇古生物表明这些矿床将到达奥陶纪晚期。孢粉学研究似乎是有益的工具，有助于对有争议的地形（如前鞭毛虫）的生物地层学知识做出贡献。

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