Growth rate and life span of Eocene/Oligocene Nummulites tests: Inferences from Sr/Ca ratio

S. Sarangi, A. Sarkar, M. M. Sarin, S. K. Bhattacharya, M. Ebihara, A. K. Ray

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The problem of growth rate and life span of Nummulites foraminifers, attaining giant sizes during the Eocene, has been addressed by analysing their Sr/Ca ratio across the Eocene/ Oligocene Boundary (EOB) of Kutch, western India. The Eocene ratio (∼ 1) rapidly decreases during the Oligocene (∼ 0.5) and is coincident with the extinction of most of the Eocene Nummulites species, a rapid enrichment of δ18O and decrease in both test size and species diversity across the boundary. The high Sr/Ca ratio in Eocene foraminifers can be explained by their rapid growth under a favourable climatic condition. The climatic deterioration (e.g. δ18O cooling) across the boundary and during the early Oligocene possibly forced the Nummulites to adopt a slower growth rate (and stunted growth). The rapid growth of the Eocene Nummulites indicates that the giant sizes of these protists need not necessarily involve a large life span.

Original languageEnglish
Pages (from-to)264-269
Number of pages6
JournalTerra Nova
Issue number4
Publication statusPublished - 2001 Aug 1


ASJC Scopus subject areas

  • Geology

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