Nick’s coauthors were Matthew Malkowski from the Department of Earth and Planetary Sciences at the University of Texas at Austin and Stephen Dobbs and Stephen Graham from the Department of Earth and Planetary Sciences at Stanford University.
Nick is a Staff Professional based in California focusing on geology and geomorphology site characterization and soil and groundwater remediation. He brings experience in data analysis and interpretation of sediment, seismic, and geological datasets, including his geological research on the Magallanes-Austral Basin in southern Patagonia and the Chugach-Prince William terrane in southern Alaska.
Geosphere is an open-access, online journal that addresses the growing need for timely publication of data-driven research results, including those that cannot be addressed by traditional formats. Its broad scope and flexible format encourages extensive use of color, animations, interactivity, and oversize figures and provides easy access to digital data such as GIS databases and modeling results.
The Geological Society of America is a global scientific society that enhances the professional growth of geoscientists at all career levels, encourages cooperative research among scientists from different fields, fosters public dialogue on geoscience issues, and promotes the geosciences in the service of humankind.
Abstract
Analyzing how provenance signatures of tectonically complex ancient sedimentary basins vary between the outcrop and the subsurface provides a more complete sediment provenance history. The 500+-kilometer- long outcrop belt of the Rocas Verdes and the Magallanes-Austral Basins in southern Patagonia and its subsurface to the east allow us to constrain relationships between longitudinal and transverse sediment sources feeding the basin. New detrital zircon U-Pb ages (n = 2558) from nine subsurface core samples from the Springhill, Piedra Clavada, and La Anita Formations along a 140 kilometer E-W seismic reflection transect (50°S, 71.5°W–69.5°W) reveal the provenance of the basin’s eastern subsurface extent and the influence that tectonic activity can have on sediment capture. Detrital zircon ages (n = 1068) were also collected from four outcrop Springhill Formation samples 140 km NW from the transect near Lago San Martín. Maximum depositional ages (MDAs) from the Springhill Formation cores range from 159 to 157 Ma, which are older than correlative outcrop ages of 151 to 148 Ma. MDAs from the Piedra Clavada and La Anita Formations range from 93.7 to 91.5 Ma and from 79.3 to 78.3 Ma, respectively, and overlap in age or are slightly younger than outcrop ages. The unimodal Late Jurassic age distribution from the Springhill Formation suggests that it almost exclusively was sourced by recycling of the underlying El Quemado Complex. Early–Middle Jurassic ages in the Early Cretaceous Piedra Clavada Formation samples suggest the basin was either sourcing from the North Patagonian Massif to the N-NE and from the Deseado Massif to the NE or recycling exhumed volcaniclastic sequences in the northern margin of the basin. By the Late Cretaceous, the basin fill was more locally sourced, as suggested by the muted abundance of Early–Middle Jurassic ages in La Anita Formation samples and a second mode of Late Jurassic–Early Cretaceous ages locally derived from recycling of the exhumed El Quemado Complex from the Patagonian fold-and-thrust belt. We suggest that the latitudinal and local transverse drainages that sourced the Magallanes-Austral Basin outcrop belt also fed the eastern, subsurface extent of the basin. Results of this work highlight the importance of using several types of provenance methods and a three-dimensional approach to study the erosional history of sedimentary basins.
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For more information on detrital zircon provenance links between outcrop and subsurface, contact Nick at Nicholas.Gross@Geosyntec.com.
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