Chronostratigraphic constraints and paleoenvironmental interpretation of the Romualdo Formation (Santana Group, Araripe Basin, Northeastern Brazil) based on palynology
Chronostratigraphic constraints and paleoenvironmental interpretation of the Romualdo Formation (Santana Group, Araripe Basin, Northeastern Brazil) based on palynology
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DOI：
10.1016/j.cretres.2020.104610
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发表时间：
2020-12-01
影响因子：
2.1
通讯作者：
Assine, Mario Luis
中科院分区：
文献类型：
--
作者：
Arai, Mitsuru;Assine, Mario Luis
Araripe盆地的Santana群是巴西一个重要的古生物单位，包括两个重要的白垩纪保护区。下部地层为阿普梯地层，上部罗穆阿尔多地层的时代已延伸至阿普梯地层。该上单元的精确年代地层位置具有重要意义，因为Romualdo组记录了白垩纪海相进入巴西东北部内陆，从而对了解冈瓦纳古地理具有重要意义。本文的主要目的是在Araripe盆地最完整的Romualdo组剖面的基础上，通过确定palynomorphs的发生情况，特别是确定巴西Aptian的指导化石Sergipea varverrucata的垂直范围，建立Romualdo组的年代地层学。根据S. varverrucata的存在，Romualdo组的年龄几乎完全是Aptian的。孢粉组合证实至少存在三个具有海洋孢粉形态的间隔（鞭毛囊和有孔虫衬里）；Romualdo组顶部呈典型的退变模式，不开孔花粉粒（Araucariacites、uesugipollgenites和Inaperturopollenites）逐渐增多。这里提出的孢粉学数据表明，整个桑塔纳群是阿普提时代的，因为明显存在的Sergipea varverrucata和缺乏无可争议的Albian形式。Romualdo组的精确定年表明，巴西东北部的海侵发生在阿普tian晚期，从而与巴西边缘盆地记录的沉积事件进行了对比。(C) 2020 Elsevier Ltd.版权所有。
The Santana Group of the Araripe Basin is a major paleontological unit in Brazil, incorporating two important Cretaceous Konservat-Lagerstatten. The lower formations are Aptian, but the age of the uppermost Romualdo Formation has been extended into the Albian. The precise chronostratigraphic position of this upper unit is of considerable significance because the Romualdo Formation records the Cretaceous marine ingression into the interior of Northeastern Brazil, thus playing a significant role in understanding the paleogeography of Gondwana. The main objective of this paper is to establish the chronostratigraphy of the Romualdo Formation based on its most complete section in the Araripe Basin, by determining the occurrence of palynomorphs, in particular establishing the vertical range of the species Sergipea variverrucata, a guide fossil of the Aptian in Brazil. Based on the presence of S. variverrucata, the Romualdo Formation is almost entirely Aptian in age. The palynological assemblage confirms the presence of at least three intervals with marine palynomorphs (dinoflagellate cysts and foraminiferal linings); and a typical regressive pattern towards the top of the Romualdo Formation, evidenced by progressive increase in inaperturate pollen grains (Araucariacites, Uesuguipollgenites and Inaperturopollenites). The palynological data presented herein indicate that the entire Santana Group is of Aptian age because of the conspicuous presence of Sergipea variverrucata and the absence of indisputably Albian forms. Precise dating of the Romualdo Formation signifies that the marine transgression into the interior of northeastern Brazil occurred in the late Aptian, thereby enabling correlation with the sedimentary events recorded in the Brazilian marginal basins. (C) 2020 Elsevier Ltd. All rights reserved.