Paleotemperatures versus sea level: Oxygen isotope signal from fish bone phosphate of the Miocene Calvert Cliffs, Maryland

Abstract

The use of skeletal oxygen isotopic records for use in paleotemperature reconstruction has been hampered by the lack of independent evidence for ocean water oxygen isotopic composition. The δ18O record from homeothermic cetaceans has provided an independent estimate of ocean δ18O values represented by the Calvert and Choptank formations of Maryland. Fish teeth and bones (especially shark and ray teeth) were also collected from these sediments and provide the basis for paleotemperature estimates for represented time slices of the middle Miocene. Trends in δ18O values of the fish phosphate throughout the Calvert Formation are of opposite polarity to the trends from the cetacean bone phosphate. Paleotemperatures calculated using the cetacean proxies for ocean δ18O values sharpen the already present trend, indicating that ocean temperatures increased during episodes of greater glaciation and decreased during periods of lesser or no glaciation. When using modern average ocean values of 0‰ SMOW in the paleotemperature calculation, however, corrected paleotemperatures for the Choptank Formation do not alter the existing pattern of temperatures.

Stable oxygen isotopes from theropod dinosaur tooth enamel: interlaboratory comparison of results and analytical interference by reference standards

“…During each day of tooth growth in an animal, an enamel band ∼20 μm thick is added to the length of the tooth 1, 5–7. The phosphate in the new enamel forms in temperature‐dependent isotopic equilibrium with the animal's body water reservoir, preserving a record of daily relative change in the animal's body water δ 18 O 8–13. A small fraction of body water is derived from food and food water, which in herbivores reflects evapotranspiration in vegetable matter,14, 15 but the body water reservoir is dominated in all animals by drinking (meteoric) water, the δ 18 O of which reflects climatic controls such as temperature and humidity 16–21.…”

“…1,[5][6][7] The phosphate in the new enamel forms in temperature-dependent isotopic equilibrium with the animal's body water reservoir, preserving a record of daily relative change in the animal's body water d 18 O. [8][9][10][11][12][13] A small fraction of body water is derived from food and food water, which in herbivores reflects evapotranspiration in vegetable matter, 14,15 but the body water reservoir is dominated in all animals by drinking (meteoric) water, the d 18 O of which reflects climatic controls such as temperature and humidity. [16][17][18][19][20][21] In enamel of heterotherms, variations in phosphate d 18 O reflect changes in body temperature as well as in drinking water; [22][23][24][25][26] by contrast, phosphate d 18 O in enamel of homeotherms varies only in response to changes in consumed water d 18 O. Enamel from a homeothermic predator preserves the highest fidelity record of meteoric water d 18 O because its body water reservoir derives a surface water d 18 O signal both through direct drinking and through the drinking water component of prey-animal tissue.…”

Neogene Caribbean elasmobranchs: Diversity, paleoecology and paleoenvironmental significance of the Cocinetas Basin assemblage (Guajira Peninsula, Colombia)

“…Based on these studies, an equation that empirically represents the oxygen isotope fractionation between biogenic phosphate and water was calculated ([T ( • C) = 111.4 − 4.3 (δ 18 O PO 4 − δ 18 O w )]), which was later revised (Kolodny et al, 1983;Pucéat et al, 2010;Lécuyer et al, 2013). This equation is used by paleontologists as a paleothermometer (Barrick et al, 1993;Lécuyer et al, 1993Lécuyer et al, , 1996. Recently the δ 18 O PO 4 values have also been used to estimate the horizontal migrations of fishes into brackish environments (Kocsis et al, 2007;Klug et al, 2010;Fischer et al, 2012Fischer et al, , 2013aLeuzinger et al, 2015).…”

“…This isotopic composition is typical for brackish waters al-though †Carcharocles chubutensis utilized a habitat similar to the recent great white shark (Carcharodon carcharias). Most of the isotopic data for the extant and fossil species of lamniform sharks are characteristic of cold waters, because of its long oceanic migrations and formation of bioapatite in such cold settings (Barrick et al, 1993;Vennemann et al, 2001;Amiot et al, 2008;Aguilera et al, 2017a). Therefore, the low δ 18 O PO 4 value from this species is quite surprising and may indicate some hidden habitat trait for this ancient shark.…”

Escalation and Extinction Selectivity: Morphology Versus Isotopic Reconstruction of Bivalve Metabolism

“…Following deposition of Shattuck zone 10, the marine climate of the Salisbury Sea degenerated (Petuch 1997), with severe cooling accompanied by a substantial drop in sea level by the time of deposition of the overlying Choptank Formation (Seravallian Age, 13 million years ago). Barrick et al (1993) also documented a decrease in sea level between the Calvert and Choptank Formations, as well as two episodes of cooling during that interval. The loss of warm, shallow Salisbury environments between the time of deposition of zone 10 and Choptank zone 17 led to the extinction of nearly 38% of the bivalve species (calculated by us from species range charts of Shattuck 1904), including G. markoei.…”