Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12136/1622
|Title:||High-resolution thrust front reconstruction using terrestrial growth strata, Pyrenees, Spain|
|Authors:||Anastasio, David J.|
Parés, Josep María
Carrigan, James H.
|Publisher:||American Geophysical Union|
|Citation:||AGU Fall Meeting, 2013|
|Abstract:||Rock and paleomagnetic research underway at Sant Llorenc de Morunys, eastern Pyrenees Spain affords the possibility of determining depositional and deformational rates with high-resolution. Along the northern boundary of the Ebro foreland Basin, the footwall of the Vallfogona thrust exposes a spectacular regional-scale growth fault-propagation fold in the Tertiary syntectonic Berga Conglomerate Group. Kilometric-scale unconformity geometries vary from angular to the west at at Santuari de Lord to conformable east of Serra de Busa. Variations in sediment accumulation rates, folding rates, and growth unconformity geometries are related to unsteady thrusting rates. Along the Llosa del Cavall reservoir bedding dips change from overturned 40<°> N to upright 30<°> S over a km of section. Through the progressively unconformable section, 3 cores were drilled and oriented in situ at sites spaced ~10m apart to determine horizon polarities. A progressive 15-step thermal demagnetization (150<°>,-690<°>C) was used to determine the characteristic remanent magnetizations directions (ChRM) by principal component analysis. The remanence is primarily carried by magnetite and hematite, and goethite is also present in some samples. ChRM directions are primary as shown by a positive fold test at 100% unfolding and were used to determine virtual geomagnetic pole latitudes. We assign the Berga Conglomerate Group to C13 and12 (Eocene/Oligocene age) based on correlation of the local magnetostratigraphy to geomagnetic polarity time scale. Based on the new data, the section was deposited at a rate of 30-50cm/kyr. Syndepositional tilt rates were higher and related to more uplift and erosion toward the west, indicating eastward propagation of the thrust fault and fold. Recovery of Milankovitch scale cyclostratigraphy based on anhysteretic remanence magnetization measurements (100 mT AC field with a 97μT constant DC field) from samples collected every 50cm support ongoing efforts to determine fault propagation and slip rate unsteadiness in 4-D.|
|Appears in Collections:||Congresos, encuentros científicos y estancias de investigación|
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