Growth rate and life span of Eocene/Oligocene Nummulites tests: inferences from Sr/Ca ratio
✍ Scribed by S. Sarangi; A. Sarkar; M. M. Sarin; S. K. Bhattacharya; M. Ebihara; A. K. Ray
- Book ID
- 104463318
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 252 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0954-4879
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✦ Synopsis
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 δ^18^O 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. δ^18^O 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.