PALEOENVIRONMENTAL ANALYSIS OF A LOWER CRETACEOUS PALEOLAKE FROM THE IGUATU BASIN BASED ON ITS OSTRACOD FAUNA AND XRF DATA

IF 1.5 4区地球科学 Q2 GEOLOGY

Palaios Pub Date : 2021-12-27 DOI:10.2110/palo.2021.006

Marcos Antonio Batista dos Santos Filho, G. Fauth, B. Sames, E. Wolfgring, Jorge Villegas‐Martín

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引用次数: 3

Abstract

Abstract: This paper presents the results of a paleoenvironmental study of two Hauterivian–Aptian adjacent sections (Transnordestina A/B) of the Iguatu Basin using ostracods and aided by X-ray fluorescence (XRF), total organic carbon (TOC), total sulfur (S), and spectral analyses. Cluster analysis divided the 10 genera found into two main groups: one composed of Alicenula-Pattersoncypris?-Brasacypris-Hastacypris-Ilyocypris?, and the second composed of Cypridea-Looneyellopsis-Rhinocypris?. The first group is interpreted as representing paleoenvironments with permanent waterbodies, such as lakes, and the second as being indicative of ephemeral settings, such as temporary pools in an inundation plain. XRF analysis using the positive peaks of Ca/Ti and Ca/RTi, Fe, Al ratios show a few dry periods, particularly in the lower and middle part of Transnordestina A, between 0 to 175 m and 385 to 475 m, which also display a small number of ostracods. Total S shows several high peaks which might be indicative of gypsum deposition during droughts. Spectral analysis of molar Ti/Al ratio shows two intervals with different sedimentation rates, between 0 and 233 m, and 233 to 836 m. For the first interval, six 100 ka eccentricity cycles were identified; the low number of ostracods for the interval and highly variable Ca/Ti and Ca/RTi, Fe, Al values indicate a different sedimentation rate in a drier environment. For the second interval, ten 405 ka cycles were identified; its higher ostracod count and more stable Ca/Ti and Ca/RTi, Fe, Al values could be indicative of increasing humidity.

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基于介形虫区系和XRF资料的伊瓜图盆地下白垩统古湖古环境分析

摘要利用介形类，结合x射线荧光(XRF)、总有机碳(TOC)、总硫(S)和光谱分析，对伊瓜图盆地两个hauteriian - aptian相邻剖面(Transnordestina a /B)进行了古环境研究。聚类分析将发现的10个属分为两大类:一类由alicenula - pattersoncyis - brasacypris- hastacypris- ilycypris ?第二类由cydea - looneyellopsis - rhinocypris组成。第一组被解释为代表了具有永久水体(如湖泊)的古环境，第二组被解释为代表了短暂的环境(如淹没平原上的临时水池)。利用Ca/Ti和Ca/RTi、Fe、Al比值的正峰进行XRF分析，发现在横北a的中下部(0 ~ 175 m和385 ~ 475 m)存在少量的干旱期，其中也存在少量介形虫。总S显示出几个高峰，这可能表明干旱期间石膏沉积。摩尔Ti/Al比值的光谱分析显示了0 ~ 233 m和233 ~ 836 m两个不同沉积速率的层段。在第一个层段，确定了6个100 ka偏心旋回;层段介形类数量少，Ca/Ti和Ca/RTi、Fe、Al值变化大，表明在干燥环境下沉积速率不同。在第二个区间，确定了10个405 ka旋回;介形虫数量增加，Ca/Ti和Ca/RTi、Fe、Al值稳定，表明湿度增加。

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来源期刊

Palaios 地学-地质学

CiteScore

2.80

自引率

12.50%

发文量

审稿时长

6 months

期刊介绍： PALAIOS is a monthly journal, founded in 1986, dedicated to emphasizing the impact of life on Earth''s history as recorded in the paleontological and sedimentological records. PALAIOS disseminates information to an international spectrum of geologists and biologists interested in a broad range of topics, including, but not limited to, biogeochemistry, ichnology, paleoclimatology, paleoecology, paleoceanography, sedimentology, stratigraphy, geomicrobiology, paleobiogeochemistry, and astrobiology. PALAIOS publishes original papers that emphasize using paleontology to answer important geological and biological questions that further our understanding of Earth history. Accordingly, manuscripts whose subject matter and conclusions have broader geologic implications are much more likely to be selected for publication. Given that the purpose of PALAIOS is to generate enthusiasm for paleontology among a broad spectrum of readers, the editors request the following: titles that generate immediate interest; abstracts that emphasize important conclusions; illustrations of professional caliber used in place of words; and lively, yet scholarly, text.