Título:
|
Glendonite occurrences in the Tremadocian of Baltica: first Early Palaeozoic evidence of massive ikaite precipitation at temperate latitudes
|
Autores:
|
Popov, Leonid E. ;
Álvaro, J.J. ;
Holmer, Lars E. ;
Bauert, Heikki ;
Pour, Mansoureh Ghobadi ;
Dronov, Andrei V. ;
Lehnert, Oliver ;
Hints, Olle ;
Männik, Peep ;
Zhang, Zhifei ;
Zhang, Zhiliang
|
Tipo de documento:
|
texto impreso
|
Editorial:
|
Nature Research, 2019
|
Dimensiones:
|
application/pdf
|
Nota general:
|
cc_by
info:eu-repo/semantics/openAccess
|
Idiomas:
|
|
Palabras clave:
|
Estado = Publicado
,
Materia = Ciencias: Geología: Geología estratigráfica
,
Materia = Ciencias: Geología: Geoquímica
,
Materia = Ciencias: Geología: Mineralogía
,
Tipo = Artículo
|
Resumen:
|
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 ?18O 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 ?18O-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.
|
En línea:
|
https://eprints.ucm.es/55501/1/Glendonite%20occurrences%20in%20the%20Tremadocian%20of%20Baltica.pdf
|