The Chachil Limestone (Pliensbachian-earliest Toarcian) Neuquen Basin, Argentina: U-Pb age calibration and its significance on the Early Jurassic evolution of southwestern Gondwana

被引：30

作者：

Leanza, H. A. ^{[1
,2
]}

Mazzini, A. ^{[3
]}

Corfu, F. ^{[4
]}

Llambias, E. J. ^{[5
]}

Svensen, H. ^{[3
]}

Planke, S. ^{[3
,6
]}

Galland, O. ^{[3
]}

机构：

[1] Serv Geol Minero Argentino, RA-1322 Buenos Aires, DF, Argentina

[2] Consejo Nacl Invest Cient & Tecn, RA-1322 Buenos Aires, DF, Argentina

[3] Univ Oslo, N-0316 Oslo, Norway

[4] Univ Oslo, Dept Geosci, N-0316 Oslo, Norway

[5] Univ Nacl La Plata, Ctr Invest Geol, RA-1900 La Plata, Argentina

[6] VBPR, N-0349 Oslo, Norway

来源：

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES | 2013年 / 42卷

关键词：

Radiometric ages; Pliensbachian/Toarcian boundary; Early Jurassic; Chachil Limestone; Precuyano Cycle; Neuquen Basin; ANTARCTIC PENINSULA; BREAK-UP; ZIRCON; PRECISION; VOLCANISM; ACCURACY; CHACAICO; SIERRA;

D O I：

10.1016/j.jsames.2012.07.012

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

New radiometric U-Pb ages obtained on zircon crystals from Early Jurassic ash layers found within beds of the Chachil Limestone at its type locality in the Chachil depocentre (southern Neuquen Basin) confirm a Pliensbachian age (186.0 +/- 0.4 Ma). Additionally, two ash layers found in limestone beds in Chacay Melehue at the Cordillera del Viento depocentre (central Neuquen Basin) gave Early Pliensbachian (185.7 +/- 0.4 Ma) and earliest Toarcian (182.3 +/- 0.4 Ma) U-Pb zircon ages. Based on these new datings and regional geological observations, we propose that the limestones cropping out at Chacay Melehue are correlatable with the Chachil Limestone. Recent data by other authors from limestones at Serrucho creek in the upper Puesto Araya Formation (Valenciana depocentre, southern Mendoza) reveal ages of 182.16 +/- 0.6 Ma. Based on these new evidences, we consider the Chachil Limestone an important Early Jurassic stratigraphic marker, representing an almost instantaneous widespread flooding episode in western Gondwana. The unit marks the initiation in the Neuquen Basin of the Cuyo Group, followed by widespread black shale deposition. Accordingly, these limestones can be regarded as the natural seal of the Late Triassic -earliest Jurassic Precuyano Cycle, which represents the infill of halfgrabens and/or grabens related to a strong extensional regime. Paleontological evidence supports that during Pliensbachian-earliest Toarcian times these limestones were deposited in western Gondwana in marine warm water environments. (c) 2012 Elsevier Ltd. All rights reserved.

引用

页码：171 / 185

页数：15

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