Heard, T.G.; (2008) Ichnology and sedimentology of deep-marine clastic systems, Middle Eocene, Ainsa-Jaca basin, Spanish Pyrenees. Doctoral thesis , University of London.

PDF U591758.pdf Download (39MB)

Abstract

Despite considerable research into the characterisation of the architectural elements of submarine fans, few studies have attempted the full integration of ichnology and sedimentology. In this thesis, a quantitative analysis of trace fossils from the Early-Middle Eocene deep-marine clastic systems, Ainsa-Jaca basin, Spanish Pyrenees, shows that trace fossils are powerful discriminators of deep-marine fan and related environments. Sixteen fan and related environments have been recognised in the Ainsa-Jaca basin, from upper-slope gully to distal basin-floor. In the more laterally confined and channel-dominated Ainsa basin, there is a trend of increasing bioturbation intensity and trace-fossil diversity away from channel-axis to off-axis environments. In the more unconfined and distal Jaca basin, there is a trend of increasing trace-fossil diversity and number of pre-depositional trace fossils including graphoglyptids from the channel-lobe transition to the fan-fringe. The trace-fossil assemblages of the Ainsa-Jaca basin are characteristic of a number of subichnofacies of the Nereites ichnofacies. In the distal Jaca basin, the Paleodictyon subichnofacies occurs in the lobe-fringe and fan-fringe, whereas the distal basin-floor has a trace-fossil assemblage typical of the Paleodictyon subichnofacies, but with a high proportion of post-depositional fodinichnia. Trace-fossil assemblages of proximal basin, axial, environments are characteristic of the Ophiomorpha rudis subichnofacies, whilst proximal off-axis environments, have a mixed Paleodictyon-Ophiomorpha rudis subichnofacies trace-fossil assemblage. In core, a detailed ichnofabric study of the proximal Ainsa channel system shows a clear trend of increasing bioturbation intensity and trace-fossil diversity from channel axis to levee-overbank. Spectral analysis of bioturbation intensity in thin-bedded turbidites deposited in overbank and interfan environments from one of the wells (A6), suggests, for the first time from a siliciclastic turbidite succession at a tectonically active plate margin, a strong cyclicity interpreted to reflect the -41 k.yr and -112 k.yr. Milankovitch frequencies. It is, therefore, proposed that global climate change acted as the principal environmental driver in controlling changes in bottom-water conditions within the deep-marine Ainsa basin.

Download activity - last month

Export as CSVXMLJSON

Download activity - last 12 months

Export as CSVJSONXML

Downloads by country - last 12 months

Export as CSVJSONXML

Archive Staff Only

View Item