Variable Pace of Deposition and Deformation Recorded from High-Resolution by Climate Cycles in Growth Strata, Spanish Pyrenees

David J. Anastasio¹, Kenneth P. Kodama¹, Linda A. Hinnov², and Josep M. Pares^3
1Earth & Environmental Sciences, Lehigh University, Bethlehem, PA
²Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD
³Geological Sciences, University of Michigan, Ann Arbor, MI

Growth Strata provide chronological and kinematic information on depositional and deformational processes in orogenic belts. Magnetostratigraphy and cyclostratigraphy from Eocene marine flysch records varying sedimentation rates accompanying oscillating deformation intensity at orbital-scale resolution at Pico del Aguila anticline; a transverse, halotectonic, décollement fold along the south Pyrenean mountain front. Formation-scale deposition in the Paleogene Jaca wedge-top basin responded to tectonic forcing, however, clastic facies patterns in the prodeltaic and slope environments reflect regional uplift controlling sediment supply, sea level variations controlling delta front position, and climate forcing of runoff variability. Both lithologic and rock magnetic data series from the productive Arguis Fm., shows hierarchical cyclicity at all predicted Milankovitch orbital frequencies. New kinematic GPS mapping, improved magnetostratigraphy, novel bed-by-bed decompaction, and precessional tuning of anhysteretic remanent magnetization (ARM) data using the LA2004 orbital model results in a sedimentary age model with 10kyr temporal resolution and meter-scale spatial resolution for growth strata deposited on the long-lived regional structure. Growth geometries record a pinned anticline hinge during décollement folding above the emerging Guarga thrust sheet. Limb tilt rates increased rapidly then decreased slowly twice from 41.6Ma to 37.8Ma at rates varying from <8°/Myr to 26°-28°/Myr, after which folding stopped for 300kyr before slowly accumulating last increment of folding, which ended at 36.6Ma. Submarine folding rates at Pico del Aguila are attributed to episodic thrusting in the fold core along a roof ramp fault and along the basal décollement.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas