Short-term middle Eocene (Bartonian) paleoenvironmental changes in the sedimentary succession of Olivetta San Michele (NW Italy): the response of shallow-water biota to climate in NW Tethys

IF 1.8 3区 地球科学 Q1 GEOLOGY
Facies Pub Date : 2024-01-11 DOI:10.1007/s10347-023-00677-4
Luca Arena, Victor M. Giraldo-Gómez, Andrea Baucon, Michele Piazza, Cesare A. Papazzoni, Johannes Pignatti, Antonella Gandolfi, Antonino Briguglio
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Abstract

This study focuses on the paleontological content of the middle Eocene (Bartonian) carbonate–siliciclastic sediments of the Capo Mortola Calcarenite Formation from Olivetta San Michele (Liguria, Italy). Along the succession, there are significant paleoecological changes triggered by the variation in neritic input as a consequence of tectonic and climatic instability. Among microfossils, nummulitids prevail, followed by orthophragmines, smaller benthic, and planktonic foraminifera, whereas mollusks and ichnofossils are the most abundant macrofossils. The sudden changes in the benthic communities due to the progressive increase in fluvial input are recorded throughout the sedimentary succession. An increase in water turbidity caused stressful conditions for autotrophic taxa, reducing their size and abundance. In contrast, filter feeders became dominant, suggesting an increase in dissolved and suspended nutrients. Ichnological analysis shows environmental fluctuations controlled by the transport of neritic material offshore, thus confirming the general deepening trend of the studied succession. In the upper part of the succession, we recorded an alternation between gravity flows and marly sediments that are interpreted as short-term alternations between low and intense precipitations. The gravity flows yield taxa such as larger benthic foraminifera (LBF), smaller benthic and planktonic foraminifera, mollusks, and corals. In turn, marls display only a few LBF and abundant smaller benthic and planktonic foraminifera. In these intervals, the increase in planktonic foraminifera also suggests a deepening of the carbonate ramp coinciding with a reduction of light that did not favor the development of LBF. These changes are probably related to the climatic dynamics that occurred in the Bartonian in the western Tethys.

Abstract Image

Olivetta San Michele(意大利西北部)沉积演替中始新世中期(巴顿期)古环境的短期变化:浅水生物群对特提斯西北部气候的响应
本研究的重点是 Olivetta San Michele(意大利利古里亚)Capo Mortola Calcarenite Formation 中始新世(巴顿期)碳酸盐-硅质碎屑沉积物中的古生物内容。由于构造和气候的不稳定性,岩浆输入的变化引发了该演替的重大古生态变化。在微化石中,有孔虫居多,其次是正虹吸虫、小型底栖有孔虫和浮游有孔虫,而软体动物和有孔虫化石则是最丰富的大型化石。在整个沉积演替过程中,都记录了由于河水输入量逐渐增加而导致底栖生物群落发生的突变。水体浊度的增加对自养类群造成了压力,使它们的体积和数量减少。与此相反,滤食性类群成为优势类群,这表明溶解和悬浮营养物质有所增加。技术分析表明,环境波动受近海海泥物质迁移的控制,从而证实了所研究的演替总体上呈加深趋势。在演替的上部,我们记录了重力流和泥灰沉积物之间的交替,这可以解释为低降水量和高降水量之间的短期交替。重力流产生的分类群包括大型底栖有孔虫(LBF)、小型底栖和浮游有孔虫、软体动物和珊瑚。而泥灰岩中只有少量的底栖有孔虫和大量的小型底栖和浮游有孔虫。在这些区间,浮游有孔虫的增加也表明碳酸盐斜坡加深,同时光照减少,不利于枸杞藻的生长。这些变化可能与特提斯西部巴顿期的气候动态有关。
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来源期刊
Facies
Facies 地学-地质学
CiteScore
3.70
自引率
5.60%
发文量
15
审稿时长
>12 weeks
期刊介绍: The journal is open to papers dealing with the interpretation of ancient and modern biotopes and carbonate depositional environments by means of facies analysis in its broadest sense. Once the central part of research in hydrocarbon exploration, facies analysis more and more integrates modern and ancient biogeological processes of a changing earth. Special emphasis is laid on paleobiology and -ecology, basin evolution, sedimentology including diagenesis and geochemistry, as well as studies emphasising the impact of life on earth history. The main part of the target group will be people in academia.
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