New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data

The Jurassic-Cretaceous (J-K) boundary is poorly constrained, and is the only Phanerozoic system boundary that lacks an internationally accepted reference stratigraphic section (GSSP). Precise radio-isotopic U-Pb data are unavailable for the earliest stage of the Cretaceous- the Berriasian. The age...

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Detalles Bibliográficos
Publicado: 2014
Materias:
Ammonites
Nannofossils
U-Pb CA-ID-TIMS
U-Pb SHRIMP
Western Gondwana
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v26_n1_p374_Vennari
http://hdl.handle.net/20.500.12110/paper_1342937X_v26_n1_p374_Vennari
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_1342937X_v26_n1_p374_Vennari
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spelling paper:paper_1342937X_v26_n1_p374_Vennari2023-06-08T16:10:33Z New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data Ammonites Nannofossils U-Pb CA-ID-TIMS U-Pb SHRIMP Western Gondwana The Jurassic-Cretaceous (J-K) boundary is poorly constrained, and is the only Phanerozoic system boundary that lacks an internationally accepted reference stratigraphic section (GSSP). Precise radio-isotopic U-Pb data are unavailable for the earliest stage of the Cretaceous- the Berriasian. The age of the Jurassic-Cretaceous boundary was based on several assumptions, including the relative duration of ammonite zones, the constant spreading rates of magnetic anomalies, and the extrapolation of Rb-Sr or K-Ar isotopic data. This paper discusses a site in an Andean Basin of Western Gondwana showing the J-K boundary interval with geographically widespread nannofossil markers which are here uniquely combined with precise radiometric dates. The recent finding of a sequence of marine black shales in the High Andes of Argentina, interbedded with ash-fall tuffs, provides important constraints on this boundary. This succession bears calcareous nannofossils and ammonites, which allow correlation with well-established Tethyan floras and faunas in the northern hemisphere. The Tithonian-Berriasian transition in the Andes was recognized on the basis of ammonite zones and nannofossil bioevents for the first time in the southern hemisphere. The new ages obtained are 137.9. ±. 0.9. Ma by sensitive high-resolution ion microprobe (SHRIMP), and 139.55. ±. 0.09/0.18. Ma by chemical-abrasion isotope-dilution thermal ionization mass spectrometry (TIMS) near the base of the Berriasian. These new ages can be interpreted in two different ways. The first alternative would indicate that the present geological time table is correct and the fossil levels should be late Berriasian. The second alternative is that the J-K boundary is 5. Ma younger than the recently published geological time scale. The authors support the last alternative and propose that the J-K boundary should be close to 140 Ma. © 2013 International Association for Gondwana Research. 2014 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v26_n1_p374_Vennari http://hdl.handle.net/20.500.12110/paper_1342937X_v26_n1_p374_Vennari
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Ammonites
Nannofossils
U-Pb CA-ID-TIMS
U-Pb SHRIMP
Western Gondwana
spellingShingle Ammonites
Nannofossils
U-Pb CA-ID-TIMS
U-Pb SHRIMP
Western Gondwana
New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data
topic_facet Ammonites
Nannofossils
U-Pb CA-ID-TIMS
U-Pb SHRIMP
Western Gondwana
description The Jurassic-Cretaceous (J-K) boundary is poorly constrained, and is the only Phanerozoic system boundary that lacks an internationally accepted reference stratigraphic section (GSSP). Precise radio-isotopic U-Pb data are unavailable for the earliest stage of the Cretaceous- the Berriasian. The age of the Jurassic-Cretaceous boundary was based on several assumptions, including the relative duration of ammonite zones, the constant spreading rates of magnetic anomalies, and the extrapolation of Rb-Sr or K-Ar isotopic data. This paper discusses a site in an Andean Basin of Western Gondwana showing the J-K boundary interval with geographically widespread nannofossil markers which are here uniquely combined with precise radiometric dates. The recent finding of a sequence of marine black shales in the High Andes of Argentina, interbedded with ash-fall tuffs, provides important constraints on this boundary. This succession bears calcareous nannofossils and ammonites, which allow correlation with well-established Tethyan floras and faunas in the northern hemisphere. The Tithonian-Berriasian transition in the Andes was recognized on the basis of ammonite zones and nannofossil bioevents for the first time in the southern hemisphere. The new ages obtained are 137.9. ±. 0.9. Ma by sensitive high-resolution ion microprobe (SHRIMP), and 139.55. ±. 0.09/0.18. Ma by chemical-abrasion isotope-dilution thermal ionization mass spectrometry (TIMS) near the base of the Berriasian. These new ages can be interpreted in two different ways. The first alternative would indicate that the present geological time table is correct and the fossil levels should be late Berriasian. The second alternative is that the J-K boundary is 5. Ma younger than the recently published geological time scale. The authors support the last alternative and propose that the J-K boundary should be close to 140 Ma. © 2013 International Association for Gondwana Research.
title New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data
title_short New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data
title_full New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data
title_fullStr New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data
title_full_unstemmed New constraints on the Jurassic-Cretaceous boundary in the High Andes using high-precision U-Pb data
title_sort new constraints on the jurassic-cretaceous boundary in the high andes using high-precision u-pb data
publishDate 2014
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v26_n1_p374_Vennari
http://hdl.handle.net/20.500.12110/paper_1342937X_v26_n1_p374_Vennari
_version_ 1768542801590484992

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