Glendonite occurrences in the Tremadocian of Baltica: first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitudes

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 δ 18 O values, which suggest high...

Full description

Saved in:
Bibliographic Details
Published in:Scientific reports 2019-05, Vol.9 (1), p.7205-7205, Article 7205
Main Authors: Popov, Leonid E., Álvaro, J. Javier, Holmer, Lars E., Bauert, Heikki, Ghobadi Pour, Mansoureh, Dronov, Andrei V., Lehnert, Oliver, Hints, Olle, Männik, Peep, Zhang, Zhifei, Zhang, Zhiliang
Format: Article
Language:English
Subjects:
704/106/413
704/2151/213/4116
Alkalinity
Calcium carbonate
Chemical precipitation
Earth science
Freezing
Geology
High temperature
Humanities and Social Sciences
Isotopes
Laboratories
multidisciplinary
Preservation
Science
Science (multidisciplinary)
Sediments
Stratigraphy
Thermal stratification
Water column
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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 δ 18 O 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 (CaCO 3 ·6H 2 O) 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 δ 18 O-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.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-019-43707-4