0000000000073046
AUTHOR
Simon M.f. Sheppard
δ18O values of coexisting brachiopods and fish: Temperature differences and estimates of paleo–water depths
To estimate vertical thermal gradients and paleo–water depths to marine platforms we present a new method based on the difference between δ 18 O values of contemporaneous brachiopod carbonate and fish phosphate. Present-day marine fauna of well-known ecology from the surface to the sea floor record isotopic temperatures that agree with measured temperatures. We predict distributions of isotopic data that result from sampling strategy, basin morphology, and fauna ecology and discuss limitations. Application of the method to the Jurassic Paris-London basin gives vertical thermal variations of up to 14 °C associated with depths varying from a few meters to 170 ± 30 m. The estimated depths are …
Rare earth element contents of Jurassic fish and reptile teeth and their potential relation to seawater composition (Anglo-Paris Basin, France and England)
The rare earth element (REE) chemistry of Jurassic shelf seawater from western Europe (Anglo-Paris Basin) was investigated by analyzing the fish and reptile teeth deposited in shallow to deeper water (<200 m) environments. REE patterns in apatites are controlled by the host sediments. Vertebrate teeth sampled from the siliciclastic sediments (calcareous sandstones and shales) show flat shale-normalized REE patterns that reflect the dominant influence of the continental source from which the REE were derived. Carbonate deposits, protected from the clastic sources, contain fish and reptile teeth whose REE patterns reflect more accurately the REE composition of the overlying water column. The …
Ice age at the Middle–Late Jurassic transition?
A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (δ18O values of shark tooth enamel) indicates a severe cooling at the Middle–Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1–3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time. Ice sheets may have developed over the high-latitude mountainous regions of Far-East Russia. The drastic cooling just post-dated the Middle–Late Callovian widespread dep…
Thermal evolution of Tethyan surface waters during the Middle-Late Jurassic: Evidence from δ18O values of marine fish teeth
[1] Oxygen isotope compositions of phosphate from vertebrate tooth enamel were measured to determine the evolution of tropical sea surface ( 0‰ owing to limited growth of continental ice during the early middle Oxfordian. The resulting sea level fall is estimated to be at least 50 m and is compatible with a global regression stage. The middle Oxfordian thermal minimum is followed by a new warming stage of 3–4°C from the middle to the late Oxfordian.