HR: 0800h
AN: PP51C-0618    [Abstracts]
TI: Milankovitch Modulated Eocene Growth Strata From the Jaca Piggyback Basin, Spanish Pyrenees
AU: * Anastasio, D J
EM: dja2@lehigh.edu
AF: Lehigh University, Earth and Environmental Sciences, 31 Williams Dr., Bethlehem, PA 18015-3188 United States
AU: Hinnov, L A
EM: hinnov@jhu.edu
AF: Johns Hopkins University, Earth and Planetary Sciences, Olin Building, 34th and North Charles Sts., Baltimore, MD 21218 United States
AU: Newton, M L
EM: mln3@lehigh.edu
AF: Lehigh University, Earth and Environmental Sciences, 31 Williams Dr., Bethlehem, PA 18015-3188 United States
AU: Kodama, K P
EM: kpk0@lehigh.edu
AF: Lehigh University, Earth and Environmental Sciences, 31 Williams Dr., Bethlehem, PA 18015-3188 United States
AB: New stratigraphic and rock magnetic data from the southern margin of the Jaca basin, Spanish Pyrenees, shows evidence of Eocene sedimentary cycles modulated by the climatic effects of Milankovitch orbital forcing. Tectonic processes simultaneously controlled larger-scale stratigraphic sequences and overall wedge-top basin development. Within the context of existing magnetostratigraphy, we described 1 km of marine basinal and prodeltaic rocks near Pico del Aguila, a large-scale synsedimentary fold, and collected samples every ~4krs for ~4myrs for lithologic and rock magnetic analysis. In magnetochrons C17r, C18n.1n, and C18n.1r (1.27myrs) anhysteretic remanent magnetization (ARM) variations occur with strong hierarchical bundling patterns suggestive of precession-scale cycles grouped into 100 kyr eccentricity cycles, and "super bundled" into 400 kyr eccentricity cycles. This pattern was exploited to construct an "eccentricity time scale" for the series producing a minimally tuned time series that is 1.3 myrs in duration; comparing well with the magnetochron calibration. Spectral analysis of this ARM time series shows that the 100-kyr tuning has aligned power into all of the principal orbital frequency bands: long eccentricity (1/(400 kyrs)), obliquity (1/(40.4 kyrs)), long precession (1/(24.4 kyrs)), and short precession (1/(20 kyrs)). Lithologic data, including bed thickness and grain size also shows high frequency periodicity we attribute to precessional forcing. ARM variations may result from climate modulated carbonate production or more likely, variable detrital inputs such as atmospheric dust (varying wind intensity or aridity) or watershed erosion (runoff variation) rather than diagenetic sources. The Milankovitch based chronology within the growth stratigraphy was then used to calculate deformation rates. Tilt rates of 9 degrees / myr for folding are comparable to other studies in which deformation was averaged over more time. We show that Milankovitch rhythms in growth strata can be used to develop novel high resolution, long-term deformation histories.
DE: 1540 Rock and mineral magnetism
DE: 4946 Milankovitch theory
DE: 8005 Folds and folding
DE: 8177 Tectonics and climatic interactions
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005