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Chronostratigraphic constraints and paleoenvironmental interpretation of the Romualdo Formation (Santana Group, Araripe Basin, Northeastern Brazil) based on palynology
Cretaceous Research ( IF 2.1 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.cretres.2020.104610
Mitsuru Arai , Mario Luis Assine

Abstract 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, Uesuguipollcenites 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.

中文翻译:

基于孢粉学的 Romualdo 组(桑塔纳群,阿拉里佩盆地,巴西东北部)的年代地层限制和古环境解释

摘要 阿拉里佩盆地桑塔纳群是巴西一个主要的古生物单元,包括两个重要的白垩纪Konservat-Lagerstatten。较低的地层是阿普蒂安,但最上面的罗穆阿尔多地层的时代已经延伸到阿尔比安。该上层单元的精确年代地层位置具有重要意义,因为 Romualdo 组记录了白垩纪海向进入巴西东北部内陆,对了解冈瓦纳古地理具有重要意义。本文的主要目的是根据 Romualdo 组在 Araripe 盆地最完整的剖面建立年代地层,通过确定孢粉体的出现,特别是确定 Sergipea variverrucata 物种的垂直范围,巴西阿普蒂安人的向导化石。基于 S. variverrucata 的存在,Romualdo 组的年代几乎完全是 Aptian。孢粉组合证实了至少三个间隔的海洋孢粉型(甲藻囊肿和有孔虫衬里);以及朝向 Romualdo 组顶部的典型回归模式,无孔花粉粒(Araucariacites、Uesuguipollcenites 和 Inaperturopollenites)的逐渐增加证明了这一点。此处提供的孢粉学数据表明,由于 Sergipea variverrucata 的显着存在和无可争议的阿尔比形式的缺失,整个桑塔纳集团都属于 Aptian 时代。Romualdo 组的精确年代表明,海侵发生在阿普蒂安晚期,进入巴西东北部内陆。
更新日期:2020-12-01
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