Benthic Foraminifera Across the Cretaceous/Paleogene Boundary in the Eastern Tethys (Northern Alborz, Galanderud Section): Extinction Pattern and Paleoenvironmental Reconstruction

IF 0.9 4区 地球科学 Q4 PALEONTOLOGY
M. Rostami, F. Frontalini, R. Leckie, R. Coccioni, E. Font, B. Balmaki
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引用次数: 7

Abstract

Extinction patterns, paleobathymetric inferences, and paleoenvironmental changes based on benthic foraminifera were investigated across the Cretaceous/Paleogene (K/Pg) boundary at the Galanderud section (Northern Alborz, Iran), which contains one of the most continuous and expanded K/Pg transitions in the eastern Tethys. On the basis of benthic foraminiferal taxa abundance and distribution, an outer neritic to uppermost bathyal paleo-depositional setting is inferred. In addition, benthic foraminiferal assemblages and planktic/benthic ratios do not indicate any major change in relative sea level during latest Maastrichtian-early Danian time. Changes in benthic foraminiferal assemblages, morphotypes, diversity, heterogeneity, and benthic foraminiferal oxygen index, coupled with statistical analyses, define three intervals. In the first interval (uppermost Maastrichtian Plummerita hantkeninoides Zone), benthic foraminiferal assemblages are moderately to well preserved and highly diverse, with a combination of epibenthic and endobenthic taxa indicating stable, mesotrophic to weakly eutrophic, normal marine conditions. A major change in benthic foraminiferal assemblages at the K/Pg boundary defines a second interval (basal Danian Guembelitria cretacea and lower part of Parvularugoglobigerina eugubina Zones) that is marked by a decrease in the endobenthic morphogroups as well as a decrease in diversity, heterogeneity, genus and species richness. This second interval denotes highly oligotrophic conditions and a collapse in productivity and food availability due to the extinction of some primary producers, with the exception of the three chalk beds representing short-lived blooms of calcareous dinoflagellates. Benthic foraminifera do not show significant extinction at the end of the Cretaceous at this section with only about an 8% loss of species. Additionally, the abundance of some opportunistic species, including Cibicidoides pseudoacutus and Tappanina selmensis, may reflect instability in the benthic foraminiferal assemblages. The third interval (middle-upper part of the Pv. eugubina Zone) is characterized by the dominance of epibenthic morphogroups (up to 70% of the assemblages) with a partial recovery of endobenthic groups. The characteristics of the benthic foraminiferal assemblages indicate that the flux of food to the benthos had not fully recovered during the early Danian.
东特提斯(Alborz北部Galanderud剖面)白垩纪/古近纪边界底栖有孔虫:灭绝模式与古环境重建
在Galanderud剖面(伊朗Alborz北部)研究了白垩纪/古近纪(K/Pg)边界的灭绝模式、古测深推断和基于底栖有孔虫的古环境变化。Galanderud剖面包含了特提斯东部最连续和扩展的K/Pg转换之一。根据底栖有孔虫类群的丰度和分布,推断其为外浅海至上深海的古沉积环境。此外,底栖有孔虫组合和浮游生物/底栖生物比值并未表明在马斯特里赫特晚期-丹尼世早期相对海平面有任何重大变化。底栖有孔虫组合、形态、多样性、异质性和底栖有孔虫氧指数的变化,结合统计分析,确定了三个区间。在第一个区间(最上层马斯特里赫特Plummerita hantkeninoides带),底栖有孔虫组合保存较好,多样性高,底栖和底栖分类群的组合表明稳定,中营养到弱富营养,正常的海洋环境。K/Pg边界底栖有孔虫组合的主要变化定义了第二个区间(基底Danian Guembelitria白垩纪和Parvularugoglobigerina eugubina带的下部),其特征是底栖生物形态群减少,多样性、异质性、属和种丰富度下降。第二个间隔表示由于一些初级生产者的灭绝,生产力和粮食供应的崩溃,生产力和粮食供应的崩溃,除了三个白垩床,代表石灰质鞭毛藻的短暂繁殖。底栖有孔虫在白垩纪末期没有明显的灭绝,只有大约8%的物种消失。此外,一些机会性物种(包括Cibicidoides pseudoacutus和Tappanina selmensis)的丰度可能反映了底栖有孔虫组合的不稳定性。第三个区间(Pv的中上部分)(eugubina带)的特点是底栖生物形态群占主导地位(高达70%的组合),底栖生物群部分恢复。底栖有孔虫组合的特征表明,在大年早期,底栖动物的食物通量尚未完全恢复。
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来源期刊
Journal of Foraminiferal Research
Journal of Foraminiferal Research 地学-古生物学
CiteScore
2.10
自引率
9.10%
发文量
32
审稿时长
>12 weeks
期刊介绍: JFR publishes original papers of international interest dealing with the Foraminifera and allied groups of organisms. Review articles are encouraged.
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