کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8908857 | 1636689 | 2017 | 58 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Tectono-stratigraphic evolution of the Comondú Group from BahÃa de La Paz to Loreto, Baja California Sur, Mexico
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله

چکیده انگلیسی
The late Oligocene to mid-Miocene volcanic and volcaniclastic rocks of the Comondú Group are well exposed along the Main Rift Escarpment of Baja California Sur from the BahÃa de La Paz region to BahÃa Concepción. New mapping and stratigraphic analysis of the Comondú Group from BahÃa de La Paz to Loreto reveal facies trends and correlations that form the foundation for a continuous stratigraphic framework for the Comondú Group along a 300Â km-long transect on the eastern coast of the Baja California peninsula. Broad but distinct lithostratigraphic trends, alluvial fan facies, and volcanic and volcaniclastic facies record an overall coarsening-upwards package that includes ignimbrite deposits within increasingly proximal alluvial fan deposits, both derived from the east. Geochronology of the unit, including 32 isotope ages and 12 previously unpublished 40Ar/39Ar ages, provide the timing of four main increasingly proximal depositional events. Non-marine sandstone, defining the base of the Comondú Group, was first deposited between ~Â 26Â Ma and ~Â 24Â Ma. Emplacement of rhyolitic ignimbrites initiated between ~Â 24Â Ma and ~Â 23Â Ma and marked a westward expansion of volcanic activity affiliated with the Sierra Madre Occidental ignimbrite sequences in southern Sinaloa, western Durango, and northern Nayarit. A change in volcanism occurred at ~Â 19Â Ma to ~Â 18Â Ma with more ignimbrites, increased intermediate compositions, and the appearance of local vents and proximal volcanic facies. A final localized change of volcanism occurred from ~Â 14 to ~Â 12Â Ma in the Loreto area with an increase of proximal alluvial fan deposits and local volcanoes in the Upper Comondú Group. The bulk of the Upper Comondú Group is absent south of the Loreto area and has either been removed by erosion as a source for the Magdalena Fan in the Pacific Ocean, or was focused primarily in the Loreto area and northward. We use a pre-rift tectonic reconstruction of the Gulf of California to align broad stratigraphic trends along the peninsula, the Gulf conjugate margins, and within the Gulf. The Cascadia arc of Oregon and northern California may be a modern analog for the Comondú Group with a linear volcanic arc formed above shrinking subducting microplates, and a broad backarc region of moderate extension and scattered volcanism.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tectonophysics - Volumes 719â720, 13 November 2017, Pages 107-114, 115, 123-134
Journal: Tectonophysics - Volumes 719â720, 13 November 2017, Pages 107-114, 115, 123-134
نویسندگان
William R. Drake, Paul J. Umhoefer, Alexis Griffiths, Ann Vlad, Lisa Peters, William McIntosh,