TY - JOUR

T1 - Geochemistry of the brachiopod Hemithiris psittacea from the Canadian Arctic

T2 - Implications for high latitude palaeoclimate studies

AU - Ullmann, Clemens V.

AU - Korte, Christoph

AU - Bitner, M. Aleksandra

AU - Azmy, Karem

AU - Brand, Uwe

PY - 2017

Y1 - 2017

N2 - Fossil shell material from high palaeo-latitudes is increasingly studied for environmental forcings specific to these latitudes and as sensitive archives of climate change. However, more detailed studies of modern analogues are necessary for putting findings into global and high latitude perspectives.Here we present δ13C and δ18O values, as well as Mg, Sr, Na, Mn and Fe contents for the rhynchonellide brachiopod Hemithiris psittacea from Friday Harbor, U.S.A. and twenty-five sites from Canada ranging in latitude from 48° to 71°N. Median Mn/Ca ratios are below 0.1mmol/mol and Fe/Ca ratios are below 0.3mmol/mol, with no strong correlation between ratios and no apparent geographical relationship. Mg/Ca and Sr/Ca ratios vary within relatively narrow limits and yield median ratios of 3.7mmol/mol and 1.13mmol/mol. Na/Ca ratios vary widely amongst the sites with median values ranging from 9 to 20mmol/mol. Relatively uniform median δ13C values of +1.8±0.6‰ (2 sd, n=25) are observed for the Canadian sites, whereas at Friday Harbor the signature of 13C depletion in local DIC is imprinted in the shell calcite. Median δ18O values of -0.5 to +2.7‰ are more variable than carbon isotope signatures and point to precipitation of shell material in seawater diluted by variable amounts of freshwater and affected by seasonal sea ice.Our results imply that robust elemental patterns and carbon isotope signatures of high latitude brachiopod fossils can be expected for most palaeogeographic situations. In contrast, δ18O signatures of shell material from high latitude marginal seas, particularly during glacial periods, would yield unreasonably high seawater temperature estimates unless the oxygen isotopic composition of the ambient water is accurately accounted for in palaeotemperature calculations.

AB - Fossil shell material from high palaeo-latitudes is increasingly studied for environmental forcings specific to these latitudes and as sensitive archives of climate change. However, more detailed studies of modern analogues are necessary for putting findings into global and high latitude perspectives.Here we present δ13C and δ18O values, as well as Mg, Sr, Na, Mn and Fe contents for the rhynchonellide brachiopod Hemithiris psittacea from Friday Harbor, U.S.A. and twenty-five sites from Canada ranging in latitude from 48° to 71°N. Median Mn/Ca ratios are below 0.1mmol/mol and Fe/Ca ratios are below 0.3mmol/mol, with no strong correlation between ratios and no apparent geographical relationship. Mg/Ca and Sr/Ca ratios vary within relatively narrow limits and yield median ratios of 3.7mmol/mol and 1.13mmol/mol. Na/Ca ratios vary widely amongst the sites with median values ranging from 9 to 20mmol/mol. Relatively uniform median δ13C values of +1.8±0.6‰ (2 sd, n=25) are observed for the Canadian sites, whereas at Friday Harbor the signature of 13C depletion in local DIC is imprinted in the shell calcite. Median δ18O values of -0.5 to +2.7‰ are more variable than carbon isotope signatures and point to precipitation of shell material in seawater diluted by variable amounts of freshwater and affected by seasonal sea ice.Our results imply that robust elemental patterns and carbon isotope signatures of high latitude brachiopod fossils can be expected for most palaeogeographic situations. In contrast, δ18O signatures of shell material from high latitude marginal seas, particularly during glacial periods, would yield unreasonably high seawater temperature estimates unless the oxygen isotopic composition of the ambient water is accurately accounted for in palaeotemperature calculations.

KW - Arctic

KW - Brachiopoda

KW - Modern analogue

KW - Oxygen isotopes

U2 - 10.1016/j.chemgeo.2017.06.007

DO - 10.1016/j.chemgeo.2017.06.007

M3 - Journal article

AN - SCOPUS:85020774050

VL - 466

SP - 187

EP - 198

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

ER -