TY - JOUR

T1 - Middle Jurassic–Lower Cretaceous glendonites from the eastern Barents Shelf as a tool for paleoenvironmental and paleoclimatic reconstructions

AU - Mikhailova, Kseniya

AU - Rogov, Mikhail

AU - Ershova, Victoria

AU - Vereshchagin, Oleg

AU - Shurekova, Olga

AU - Feodorova, Anna

AU - Zakharov, Victor

N1 - Publisher Copyright: © 2021 Elsevier B.V.

PY - 2021/10/1

Y1 - 2021/10/1

N2 - Glendonites are carbonate pseudomorphs after ikaite which use as indicators of near-freezing temperatures. We describe the first glendonites of Middle–Late Jurassic to Early Cretaceous age from the Barents Shelf, including the first glendonites of Late Barremian–Early Aptian age ever discovered on Earth and provide the detailed mineralogical-geochemical and isotopic studies. Mesozoic glendonites are well-known across the Arctic realm, however the ikaite-calcite transformation and implication of glendonite findings are still debatable. Pseudomorphs are mainly composed of calcite. Cathodoluminescence and scanning electron microscopy studies reveal three types (I-III) of calcite: type I - elongated, rounded and irregular calcite; type II - blocky, fibrous and needle-like calcite/siderite; type III - blocky calcite in pores. Elemental analyses distinguish geochemical differences between the calcite types: type I comprises pure CaCO3; type II calcite contains Mg and P (in all studied samples), Fe (Bajocian–Callovian), S (Middle Volgian) or Sr (Upper Barremian–Lower Aptian); type III calcite is depleted in Mg, P and Fe. Concentrations of Mn, Fe, Sr and calculated Mn/Ca, Fe/Ca and Sr/Ca ratios are suggestive of diagenetic alteration. Bulk δ18O values range from −5.39 to −1.71‰ VPDB, supporting overprinting of primary values during burial diagenesis, while bulk δ13C values range from −33.3 to −22.6‰ VPDB, providing the influence of organic matter on ikaite-glendonite formation. However, 87Sr/86Sr values range from 0.7070 to 0.7110, mainly corresponding to Jurassic–Cretaceous seawater. Rare-earth elements characterize porewater REE-patterns, with slight middle REE-enrichment and depletion in light and heavy REE. Weak positive and negative Ce anomalies indicate fluctiating from anoxic to oxic conditions during ikaite-glendonite formation. Our new biostratigraphic data refine the ages of glendonite-bearing horizons in the Barents Shelf region, allowing a more definitive correlation with coeval glendonite occurrences across the Arctic realm and with global climatic changes during the Jurassic–Cretaceous.

AB - Glendonites are carbonate pseudomorphs after ikaite which use as indicators of near-freezing temperatures. We describe the first glendonites of Middle–Late Jurassic to Early Cretaceous age from the Barents Shelf, including the first glendonites of Late Barremian–Early Aptian age ever discovered on Earth and provide the detailed mineralogical-geochemical and isotopic studies. Mesozoic glendonites are well-known across the Arctic realm, however the ikaite-calcite transformation and implication of glendonite findings are still debatable. Pseudomorphs are mainly composed of calcite. Cathodoluminescence and scanning electron microscopy studies reveal three types (I-III) of calcite: type I - elongated, rounded and irregular calcite; type II - blocky, fibrous and needle-like calcite/siderite; type III - blocky calcite in pores. Elemental analyses distinguish geochemical differences between the calcite types: type I comprises pure CaCO3; type II calcite contains Mg and P (in all studied samples), Fe (Bajocian–Callovian), S (Middle Volgian) or Sr (Upper Barremian–Lower Aptian); type III calcite is depleted in Mg, P and Fe. Concentrations of Mn, Fe, Sr and calculated Mn/Ca, Fe/Ca and Sr/Ca ratios are suggestive of diagenetic alteration. Bulk δ18O values range from −5.39 to −1.71‰ VPDB, supporting overprinting of primary values during burial diagenesis, while bulk δ13C values range from −33.3 to −22.6‰ VPDB, providing the influence of organic matter on ikaite-glendonite formation. However, 87Sr/86Sr values range from 0.7070 to 0.7110, mainly corresponding to Jurassic–Cretaceous seawater. Rare-earth elements characterize porewater REE-patterns, with slight middle REE-enrichment and depletion in light and heavy REE. Weak positive and negative Ce anomalies indicate fluctiating from anoxic to oxic conditions during ikaite-glendonite formation. Our new biostratigraphic data refine the ages of glendonite-bearing horizons in the Barents Shelf region, allowing a more definitive correlation with coeval glendonite occurrences across the Arctic realm and with global climatic changes during the Jurassic–Cretaceous.

KW - Ammonites

KW - Bivalve

KW - Carbonates

KW - Dinoflagellate

KW - Paleogeography

KW - REE

KW - Stable isotopes

KW - Strontium isotopes

KW - Sulphate reduction

UR - http://www.scopus.com/inward/record.url?scp=85112822829&partnerID=8YFLogxK

U2 - 10.1016/j.palaeo.2021.110600

DO - 10.1016/j.palaeo.2021.110600

M3 - Article

AN - SCOPUS:85112822829

VL - 579

JO - Palaeogeography, Palaeoclimatology, Palaeoecology

JF - Palaeogeography, Palaeoclimatology, Palaeoecology

SN - 0031-0182

M1 - 110600

ER -