High-resolution Late Silurian correlations between Gotland, Sweden and the Broken River region, NE Australia: Lithologies, conodonts and isotopes

Lennart Jeppsson, J. A. Talent, R. Mawson, A. J. Simpson, A. S. Andrew, M. Calner, D. J. Whitford, J. A. Trotter, O. Sandstrom, H. J. Caldon

Research output: Chapter in Book/Report/Conference proceedingPaper in conference proceedingpeer-review

67 Citations (SciVal)

Abstract

High-resolution correlations, partly with a precision better than 10 ka, are achieved between late Ludfordian sequences on Gotland, Sweden (on Baltica), and a section (COG) through the Coral Gardens Formation along the Broken River, northeastern Australia (on Gondwana), despite these sections having been on different palaeocontinents facing different oceans. The interval is characterised by rapid, very large faunal, isotopic, and lithologic changes. Lithologies are remarkably similar in the two areas, consisting of, in order from below: marls with thin limestone beds, flaggy limestones, oncoidal crinoidal limestone, oncoidal marls, terrigenous clastics (silty clay, mudstone, sandstone), oolite, and cliff-/gorge-forming limestones. Further, independent correlation dates several of the lithological changes as coeval. The 813 C excursion in whole rock carbonates is one of the three largest ones known during the Phanerozoic. The increase in delta C-13 is very similar in the two areas, from below + 1 parts per thousand to c. + 9 parts per thousand VPDB though two Gotland samples yielded + 9.71 parts per thousand and + 10.54 parts per thousand (the corresponding COG interval included fewer carbonate layers than needed to definitely exclude that this difference is due to a lack of suitable rocks for sampling). Compared with the lithologies and the delta C-13 curves, the conodont faunas display some divergence, but key taxa permit precise correlations for much of the studied interval. The conodont assemblages change stepwise from very diverse in the Polygnathoides siluricus Zone to a low diversity fauna dominated markedly by a single taxon (Upper Icriodontid Subzone), returning abruptly to a comparatively diverse Ozarkodina snajdri Zone fauna. A method resembling graphic correlation in some respects is used to propose a similarly high-resolution correlation through a longer interval for future testing. (c) 2006 Elsevier B.V. All rights reserved.
Original languageEnglish
Title of host publicationPalaeogeography, Palaeoclimatology, Palaeoecology
PublisherElsevier
Pages115-137
Volume245
DOIs
Publication statusPublished - 2007
EventInternational Symposium on Early Palaeozoic Palaeogeography and Palaeoclimate - Erlangen, Germany
Duration: 2004 Sep 12004 Sep 3

Publication series

Name
Number1-2
Volume245
ISSN (Print)1872-616X
ISSN (Electronic)0031-0182

Conference

ConferenceInternational Symposium on Early Palaeozoic Palaeogeography and Palaeoclimate
Country/TerritoryGermany
CityErlangen
Period2004/09/012004/09/03

Subject classification (UKÄ)

  • Geology

Keywords

  • high-resolution correlation
  • conodonts
  • carbon isotopes
  • Australia
  • Silurian
  • Sweden

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