Abstract Due to its intermediate geographical position between the Mediterranean and W Pacific, the Oligocene shallow-marine sequence of Kutch (India) is of key importance in paleobiogeographical interpretations. Larger benthic foraminifera (LBF) are a fundamental link for the correlation between the Mediterranean shallow benthic zones (SBZ) and the W Pacific ‘letter stages’. LBF were re-evaluated by morphometric studies of the internal test from five stratigraphic sections of the Maniyara Fort Formation. Based on their significant affinity to coeval fauna in the Mediterranean, they were assigned to W Tethyan SBZ zones, supported by Sr-isotope stratigraphy. In the Basal Member, traditionally considered as early Rupelian, we identified Nummulites bormidiensis, N. kecskemetii and Heterostegina assilinoides assigning it to the early Chattian SBZ 22B Zone. The Coral Limestone Member, previously considered as late Rupelian, is also assigned to this zone, for the presence of N. bormidiensis, Eulepidina formosoides-dilatata and Nephrolepidina morgani-praemarginata. Its early Chattian age (26.5–29 Ma) is further supported by Sr-isotope data. Miogypsinoides complanatus and Spiroclypeus margaritatus in the Bermoti Member (the top of the formation) document the late Chattian SBZ 23 Zone and the Sr-isotope data (22.5–24 Ma) place it close to the Oligocene–Miocene boundary.

中文翻译：

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来自 Kutch 渐新世（印度西部）的 Nummulitids、lepidocyclinids 和 Sr 同位素数据以及年代地层学和古生物地理评估

摘要 由于位于地中海和西太平洋之间的中间地理位置，Kutch（印度）渐新世浅海层序在古生物地理解释中具有重要意义。较大的底栖有孔虫 (LBF) 是地中海浅底栖带 (SBZ) 和西太平洋“字母阶段”之间相关性的基本联系。通过对 Maniyara Fort Formation 的五个地层剖面的内部测试进行形态测量研究，重新评估了 LBF。基于它们与地中海同期动物群的显着亲和力，它们被分配到 W Tethyan SBZ 带，并得到 Sr 同位素地层学的支持。在传统上被认为是早期 Rupelian 的基底成员中，我们确定了 Nummulites bormidiensis, N. kecskemetii 和 Heterostegina assilinoides 将其分配给早期的 Chattian SBZ 22B 区。由于存在 N. bormidiensis、Eulepidina formosoides-dilatata 和 Nephrolepidina morgani-praemarginata，之前被认为是晚 Rupelian 的珊瑚石灰岩成员也被归入该区域。它的早期 Chattian 时代（26.5-29 Ma）得到了 Sr 同位素数据的进一步支持。Bermoti 段（地层顶部）的 Miogypsinoides complanatus 和 Spiroclypeus margaritatus 记录了晚期 Chattian SBZ 23 带，Sr 同位素数据（22.5-24 Ma）将其置于渐新世-中新世边界附近。Sr 同位素数据进一步支持 5–29 Ma)。Bermoti 段（地层顶部）的 Miogypsinoides complanatus 和 Spiroclypeus margaritatus 记录了晚期 Chattian SBZ 23 带，Sr 同位素数据（22.5-24 Ma）将其置于渐新世-中新世边界附近。Sr 同位素数据进一步支持了 5–29 Ma)。Bermoti 段（地层顶部）的 Miogypsinoides complanatus 和 Spiroclypeus margaritatus 记录了晚期 Chattian SBZ 23 带，Sr 同位素数据（22.5-24 Ma）将其置于渐新世-中新世边界附近。