Abstract
Provenance of the Middle-Late Ordovician clastic wedge in the Argentine Precordillera
Abstracts with programs - Geological Society of America, Vol.41(1), p.20
Geological Society of America, Southeastern Section, 58th annual meeting
02/2009
Abstract
Middle-Late Ordovician subduction of the Argentine Precordillera beneath western Gondwana is indicated by: Famatina continental-margin arc on western Gondwana; thermochronology and top-to-west shear in massifs along the eastern Precordillera; down-to-east subsidence of the Precordillera carbonate platform, and westward progression of a synorogenic clastic wedge primarily from sources east of the Precordillera. U-Pb analyses of detrital zircons from 10 clastic-wedge sandstones span a vertical succession (Middle-Late Ordovician) and a cross-strike transect from east (proximal) to west (distal). Results include: (1) ages of 980-1200 Ma dominate all samples, (2) secondary abundances 1200-1500 Ma characterize most samples, and (3) scattered ages in the ranges of 515-940, 1650-1920, and 1970-2180 Ma are common. Clasts from the Las Vacas Conglomerate include: abundant igneous rocks (crystallization ages of 614-647 Ma with xenocrysts of 1000-1200 Ma); white quartzite and red sandstone (similar to the detrital populations); and very rare gneiss (distinctive peaks at 550-700 and 1750-1810 Ma with scattered, rare ages at 770-850, 1010-1320, and 2000-2277 Ma). Late Mesoproterozoic (1000-1200 Ma) ages are documented in basement of the Precordillera and of the Sierra de Pie de Palo and other massifs east of the Precordillera, as well as older ( approximately 1370 Ma) basement clasts in the Precordillera. More importantly, quartzite in Pie de Palo has detrital-zircon age peaks at 1000-1200 and 1300-1450 Ma. The abundance of 1000-1200 Ma zircons in the clastic wedge is compatible with a source in the Pie de Palo and other massifs (basement and cover), which may have been incorporated into a complex accrectionary prism and backthrusted during subduction. The 1000-1500 Ma grains could be from a primary Sunsas or Rondonian source or from recycling of pre-Ordovician sedimentary cover on the upper plate; however, the relative abundance of these grains favors the basement and cover of Pie de Palo and other nearby massifs. Neoproterozoic ages (515-800 Ma) are compatible with upper-plate (e.g., Pampean and Brasiliano) rocks or, alternatively, Iapetan synrift igneous rocks, which have been recognized in Pie de Palo. The distinct Paleoproterozoic grains (2000-2200 Ma) suggest a primary source in Amazonia or Rio de La Plata basement or cover.
Details
- Title: Subtitle
- Provenance of the Middle-Late Ordovician clastic wedge in the Argentine Precordillera
- Creators
- William A Thomas - University of KentuckyRicardo A AstiniPaul A MuellerWilliam C McClellandGeorge KamenovJohn S AllenLeeanna Hyacinth
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.41(1), p.20
- Conference
- Geological Society of America, Southeastern Section, 58th annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, Southeastern Section, 58th annual meeting
- Language
- English
- Date published
- 02/2009
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240884002771
Metrics
6 Record Views