Webbläsaren som du använder stöds inte av denna webbplats. Alla versioner av Internet Explorer stöds inte längre, av oss eller Microsoft (läs mer här: * https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Var god och använd en modern webbläsare för att ta del av denna webbplats, som t.ex. nyaste versioner av Edge, Chrome, Firefox eller Safari osv.

Mikael Calner

Mikael Calner

Professor

Mikael Calner

Palaeokarst evidence for widespread regression and subaerial exposure in the middle Katian (Upper Ordovician) of Baltoscandia: significance for global climate.

Författare

  • Mikael Calner
  • Oliver Lehnert
  • Jaak Nõlvak

Summary, in English

We report on widespread and contemporary palaeokarst in the middle Katian (Upper Ordovician) of Sweden,

Estonia and Latvia, the first major palaeokarst horizon to be reported from the Ordovician of Baltoscandia. The

solution features occurwithin a fewmetres of thick zone of limestone immediately belowthe widespread Fjäcka

Shale and are related to an unconformity with preserved palaeorelief in the Slandrom Limestone in Sweden and

the time-equivalent Saunja Formation in Estonia and Latvia. Facies evidence for a karst origin comes fromseveral

outcrops and core sections and includes 1) frequent karren-likemorphologies interpreted as ‘Swiss-cheese’ karst

[sensu Baceta et al., 2001], 2) local occurrences of solution/collapse breccia, 3) presence of bladed pseudospar

crystals in solution cavities, and 4) carbon isotope values indicating meteoric influence to the succession. These

findings are herein put in context with previously reported, large-scale erosional channels that may cut down

several tens of metres below the Fjäcka Shale in the subsurface Baltic Sea area, and with regional, anomalous

thickness variations in the Slandrom Limestone and Saunja Formation, all together forming strong support for

regional exposure of the Baltoscandian continent in the middle Katian. High-resolution stable isotopic data show

that the regression and lowstand of sea-level overlap with theWaynesville carbon isotope excursion. It resulted

in basin-wide cessation of carbonate production near the Amorphognathus superbus and A. ordovicicus conodont

zonal boundary. The contemporary development of palaeokarst in different confacies belts of the basin suggests

that this was an extraordinary sea-level lowstand, herein interpreted as reflecting a middle Katian glaciation.

Avdelning/ar

  • Berggrundsgeologi

Publiceringsår

2010

Språk

Engelska

Sidor

235-247

Publikation/Tidskrift/Serie

Palaeogeography, Palaeoclimatology, Palaeoecology

Volym

296

Issue

3-4

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Geology

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1872-616X