کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6431474 1635167 2013 15 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The Chachil Limestone (Pliensbachian-earliest Toarcian) Neuquén Basin, Argentina: U-Pb age calibration and its significance on the Early Jurassic evolution of southwestern Gondwana
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
The Chachil Limestone (Pliensbachian-earliest Toarcian) Neuquén Basin, Argentina: U-Pb age calibration and its significance on the Early Jurassic evolution of southwestern Gondwana
چکیده انگلیسی

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 Neuquén 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 Neuquén 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 Neuquén 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.

Highlights► New radiometric data (ca. 182-186 Ma) constrain the age of the Chachil Limestone in the Neuquén Basin. ► It represents an instantaneous flooding episode throughout the entire basin. ► It is an Early Jurassic stratigraphic and paleoclimatic marker of regional significance. ► It marks the boundary between the synrift Precuyano Cycle and the Cuyo Group. ► The Precuyano Cycle includes the marine deposits below the Chachil Limestone.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of South American Earth Sciences - Volume 42, March 2013, Pages 171-185
نویسندگان
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