HR: 11:35h
AN: OS32A-06    [Abstracts]
TI: Deconvolving tectonic and climatic effects on Sedimentation Patterns in Deep-Marine Clastics, Eocene, Spanish Pyrenees
AU: * Pickering, K T
EM: ucfbktp@ucl.ac.uk
AF: UCL (University College London), Department of Earth Sciences Gower Street, London, WC1E 6BT, United Kingdom
AU: Heard, T G
EM: t.heard@ucl.ac.uk
AU: Bayliss, N
EM: n.bayliss@ucl.ac.uk
AU: Sutcliffe, C
EM: clare.sutcliffe@ucl.ac.uk
AU: Das Gupta, K
EM: k.dasgupta@ucl.ac.uk
AU: Robinson, S
EM: stuart.robinson@ucl.ac.uk
AB: The Eocene Ainsa basin, Spanish Pyrenees, contains ~4 km of deep-marine deposits that accumulated in ~10 M.yr., as two principal angular-unconformity-bound tectono-stratigraphic units, in which the younger unit is structurally less deformed and shows a WSW shift in depositional axis, showing a first-order tectonic control on accommodation and deposition. The basin evolved with mainly non-marine and marginal marine environments in the eastern sectors, whilst farther west there was an overall change from fluvio-deltaic to deep-marine systems. The deep-marine deposits are overlain by ~0.5 km of fluvio-deltaic and related sediments fed mainly from the south and east. Micropaleontology suggests water depths in the Ainsa basin were in the range 400-800 m. The two "tectono-stratigraphic" units contain 8 coarse clastic systems, each in the order of 100-200 m thick, and vertically separated by up to several tens of meters of mainly marls with lesser amounts of thin- to very thin- bedded sandstone turbidites. Each system typically contains 2-7 individual sandbodies (amounting to at least 25 throughout the basin), from 30-100 m thick, separated by 10s m of mainly thin- and very thin-bedded sandstones with subordinate marls. Within each sandbody, submarine channels show a consistent WSW offset stacking pattern away from the deformation front that acted as one of the confining basin lateral-margins. In contrast to the longer-term 4-5 M.yr. tectonic driver, the number of deep-marine sandbodies in the Ainsa basin (~25) that accumulated in ~10 M.yr, suggests the operation of a faster, non-tectonic driver, possibly related to the 400 k.yr. long-period eccentricity. Spectral analysis of bioturbation intensity in thin-bedded, fine-grained sediments in one of the cored intervals shows a likely 41 k.yr. and ~100 k.yr. Milankovitch cyclicity. The age model for the Ainsa basin yields an average sediment accumulation rate of ~40 cm/k.yr., that is consistent with that inferred from the spectral analysis (~30 cm/k.yr.) for fine-grained sedimentation. A detailed analysis of the Ainsa basin sediments has permitted the deconvolution of tectonic and climatic signals at several time scales within a tectonically active basin.
DE: 3022 Marine sediments: processes and transport
DE: 4910 Astronomical forcing
DE: 8169 Sedimentary basin processes
DE: 8175 Tectonics and landscape evolution
DE: 8177 Tectonics and climatic interactions
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting