RT Journal Article
T1 Glendonite occurrences in the Tremadocian of Baltica: first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitudes
A1 Popov, Leonid E.
A1 Álvaro, J.J.
A1 Holmer, Lars E.
A1 Bauert, Heikki
A1 Pour, Mansoureh Ghobadi
A1 Dronov, Andrei V.
A1 Lehnert, Oliver
A1 Hints, Olle
A1 Männik, Peep
A1 Zhang, Zhifei
A1 Zhang, Zhiliang
AB The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40 °C. In the mid-latitude Baltoscandian Basin, conodonts displaying low δ18O values, which suggest high temperatures (>40 °C) in the water column, are in contrast with the discovery of contemporaneous glendonite clusters, a pseudomorph of ikaite (CaCO3·6H2O) traditionally considered as indicator of near-freezing bottom-water conditions. The massive precipitation of this temperature sensitive mineral is associated with transgressive conditions and high organic productivity. As a result, the lower Tremadocian sediments of Baltoscandia apparently contain both “greenhouse” pelagic signals and near-freezing substrate indicators. This paradox points to other primary controlling mechanisms for ikaite precipitation in kerogenous substrates, such as carbonate alkalinity, pH and Mg/Ca ratios, as recently constrained by laboratory experiments. Preservation of “hot” conodonts embedded in kerogenous shales rich in δ18O-depleted glendonites suggests both the onset of sharp thermal stratification patterns in a semi-closed basin and the assumed influence of isotopically depleted freshwater yielded by fluvial systems.
PB Nature Research
SN 2045-2322
YR 2019
FD 2019
LK https://hdl.handle.net/20.500.14352/13338
UL https://hdl.handle.net/20.500.14352/13338
LA eng
NO Ministerio de Economía y Competitividad
NO Estonian Research Council
NO Deutsche Forschungsgemeinschaft
NO Golestan University Research
NO Swedish Research Council
NO National Natural Science Foundation of China
NO 111 Centre
NO Russian Governmental Program of Competitive Growth of Kazan Federal University
NO Program for Fundamental Research of the Presidium of Russian Academy of Sciences
DS Docta Complutense
RD 9 abr 2025