Strontium-isotope stratigraphy and oxygen-and carbon-isotope variation during the Middle Jurassic–Early Cretaceous of the Falkland Plateau, South Atlantic

Price, G.D.; Gröcke, D.R.

Abstract

87Sr/86Sr data of belemnites are presented from a Middle Jurassic–Early Cretaceous succession from the Falkland Plateau (Deep Sea Drilling Project Sites 511 and 330) that was deposited in a periodically anoxic, semi-enclosed shallow water basin. Diagenetically screened strontium-isotope values of 0.706789 rise to 0.707044 before increasing sharply to 0.707428 in the uppermost part of the sampled succession. Comparison with published strontium calibration curves suggests that the oldest samples were Callovian to Oxfordian in age, whilst the remainder of the Jurassic part of the succession consisted of Kimmeridgian and Early Tithonian age sediments. The nannofossil, dinoflagellate and molluscan assemblages provide comparable age determinations. The strontium-isotope analysis of the youngest belemnites points to a Hauterivian–Barremian age, whilst age interpretations based upon the fauna provide a wide age range from the Barremian to early Albian. Strontium-isotope stratigraphy of this succession hence offers increased age resolution providing data regarding the timing of episodes of bottom water anoxia which have been recorded throughout the South Atlantic Basin. Well-preserved belemnite specimens display an oxygen-isotope range between +0.08 and −2.22‰ (PDB, Peedee belemnite international standard) and a carbon-isotope range from +2.35 to −1.33‰ (PDB). δ13C values become increasingly negative through the Late Jurassic–Early Cretaceous and in concert with the 87Sr/86Sr data reveal a trend that could be accounted for by increasing levels of weathering and erosion. The oxygen-isotope data if interpreted in terms of palaeotemperature are consistent with warm palaeotemperatures in the Kimmeridgian and slightly cooler temperatures for the Tithonian and Early Cretaceous parts of the succession. The proposed relative Kimmeridgian warmth (based upon strontium-isotope age assignments) is thus in good agreement with other published palaeotemperature records.

Citation

Price, G., & Gröcke, D. (2002). Strontium-isotope stratigraphy and oxygen-and carbon-isotope variation during the Middle Jurassic–Early Cretaceous of the Falkland Plateau, South Atlantic. Palaeogeography, Palaeoclimatology, Palaeoecology, 183(3-4), 209-222. https://doi.org/10.1016/s0031-0182%2801%2900486-2

• Journal Article Type: Article
• Acceptance Date: Nov 26, 2001
• Online Publication Date: Apr 19, 2002
• Publication Date: 2002-07
• Deposit Date: May 19, 2015
• Journal: Palaeogeography, Palaeoclimatology, Palaeoecology
• Print ISSN: 0031-0182
• Electronic ISSN: 1872-616X
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 183
• Issue: 3-4
• Pages: 209-222
• DOI: https://doi.org/10.1016/s0031-0182%2801%2900486-2
• Public URL: https://durham-repository.worktribe.com/output/1428367