Skip to Main Content
GEOREF RECORD

A graptolite-rich Ordovician-Silurian boundary section in the south-central Pyrenees, Spain; stratigraphical and palaeobiogeographical significance

Petr Storch, Josep Roque Bernal and Juan Carlos Gutierrez-Marco
A graptolite-rich Ordovician-Silurian boundary section in the south-central Pyrenees, Spain; stratigraphical and palaeobiogeographical significance
Geological Magazine (June 2019) 156 (6): 1069-1091

Abstract

An Ordovician-Silurian boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower-middle Akidograptus ascensus-Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus-acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician-Silurian boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and delta (super 13) C (sub org) values suggest uninterrupted sedimentation under stable, anoxic conditions.


ISSN: 0016-7568
EISSN: 1469-5081
Coden: GEMGA4
Serial Title: Geological Magazine
Serial Volume: 156
Serial Issue: 6
Title: A graptolite-rich Ordovician-Silurian boundary section in the south-central Pyrenees, Spain; stratigraphical and palaeobiogeographical significance
Affiliation: Czech Academy of Sciences, Institute of Geology, Prague, Czech Republic
Pages: 1069-1091
Published: 201906
Text Language: English
Publisher: Cambridge University Press, London, United Kingdom
References: 98
Accession Number: 2019-062049
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., geol. sketch maps
N42°15'00" - N42°19'60", E01°34'60" - E01°42'00"
Secondary Affiliation: Universidad Complutense de Madrid, ESP, Spain
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Cambridge University Press. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201915
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal