New palynological data and paleoenvironmental implications for the Lower Devonian and Lower Cretaceous successions in the Rio do Peixe Basin, Brazil: Sedimentary organic matter analyses

IF 1.5 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of South American Earth Sciences Pub Date : 2025-09-25 DOI:10.1016/j.jsames.2025.105805

Lucas Mateus Andrade Lima , Juan David Vallejo , Regina Buarque Gusmão , Mario Ferreira Lima Filho , Enelise Katia Piovesan

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引用次数: 0

Abstract

The Rio do Peixe Basin (RDPB) is recognized for its paleontological significance, due to the presence of dinosaur fossils, as well as traces of invertebrates, such as arthropod and annelid burrows. Additionally are included plant fossils, ostracods, conchostracans, fish scale, and crocodylomorph bones, all from the Lower Cretaceous (Berriasian—Barremian). However, the depositional conditions of the RDPB remain being discussed, considering the presence or not of a Devonian sequence and its limits. The latest proposals indicate two groups for this basin: the Santa Helena Group, from the Lower Devonian and the Rio do Peixe, from the Lower Cretaceous. Between these two units lies a significant depositional hiatus of approximately 265 million years. This study characterizes sedimentary organic matter from Lower Devonian and Lower Cretaceous drill cuttings of the 1-PIL-1-PB well to reconstruct the depositional paleoenvironment, redox conditions and kerogen type. Standard palynological preparation techniques were applied to produce microscope slides and to classify organic matter into groups and subgroups. Based on the analyzed section, the Devonian sequence of the RDPB is interpreted as a closed to semi-closed lagoonal system with marine influence, developed under reducing conditions and generating predominantly Type II kerogen. In contrast, during the Lower Cretaceous, the basin was dominated by a fluvial system characterized input of phytoclast, developed under predominantly oxic conditions. In addition, new miospore occurrences were identified, such as Dictyotriletes emsiensis, Cymbostporites sp., Retusotriletes triangulatus, Retusotriletes sp., Gneudnaspora divellomedia and Diabolisporites sp. Considering the age constraints in this study, we propose a re-evaluation of the Lower Devonian–Lower Cretaceous bounding in this basin.

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巴西里约热内卢do Peixe盆地下泥盆统和下白垩统新孢粉学资料及其古环境意义：沉积有机质分析

由于发现了恐龙化石，以及节肢动物和环节动物洞穴等无脊椎动物的痕迹，里约热内卢do Peixe盆地（RDPB）因其古生物学意义而得到认可。此外还包括植物化石、介形类、贝壳类、鱼鳞和鳄鱼骨，都来自下白垩纪（贝里亚-巴雷米亚）。然而，考虑到泥盆纪层序的存在与否及其局限性，RDPB的沉积条件仍在讨论中。最新的建议表明该盆地有两个群：来自下泥盆纪的圣赫勒拿群和来自下白垩纪的里约热内卢do Peixe。在这两个单元之间有一个大约2.65亿年的重要沉积间隙。本研究对1-PIL-1-PB井下泥盆统和下白垩统钻井岩屑的沉积有机质进行了表征，重建了沉积古环境、氧化还原条件和干酪根类型。采用标准孢粉制备技术制备显微镜载玻片，并对有机质进行类群和亚类群的划分。根据分析剖面，认为RDPB泥盆纪层序为受海相影响的封闭-半封闭泻湖体系，发育于还原性条件下，以ⅱ型干酪根为主。相比之下，下白垩世盆地以植物碎屑输入为特征的河流系统为主导，主要在氧气条件下发育。此外，还发现了新的微孢子，如Dictyotriletes emsiensis、Cymbostporites sp.、Retusotriletes triangulatus、Retusotriletes sp.、Gneudnaspora divellomedia和Diabolisporites sp.。考虑到本研究的年龄限制，我们建议对该盆地下泥盆统-下白垩统界线进行重新评价。

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来源期刊

Journal of South American Earth Sciences 地学-地球科学综合

CiteScore

3.70

自引率

22.20%

发文量

364

审稿时长

6-12 weeks

期刊介绍： Papers must have a regional appeal and should present work of more than local significance. Research papers dealing with the regional geology of South American cratons and mobile belts, within the following research fields: -Economic geology, metallogenesis and hydrocarbon genesis and reservoirs. -Geophysics, geochemistry, volcanology, igneous and metamorphic petrology. -Tectonics, neo- and seismotectonics and geodynamic modeling. -Geomorphology, geological hazards, environmental geology, climate change in America and Antarctica, and soil research. -Stratigraphy, sedimentology, structure and basin evolution. -Paleontology, paleoecology, paleoclimatology and Quaternary geology. New developments in already established regional projects and new initiatives dealing with the geology of the continent will be summarized and presented on a regular basis. Short notes, discussions, book reviews and conference and workshop reports will also be included when relevant.