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Title: Temporal and spatial relationships of syn-rift, deep-marine hangingwall stratigraphy : examples from the Upper Jurassic of the Inner Moray Firth and the Central North Sea
Author: McArthur, Adam D.
ISNI:       0000 0004 2736 9078
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2012
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Sedimentological and palynological datasets have been integrated to improve the understanding of syn-rift, deep-marine hanging wall strata. Upper Jurassic fault scarps were examined from Inner Moray Firth (IMF) outcrops and subsurface data from the Central Graben. Reduced sand supply recorded in IMF sediments, comprising siltstones, sandstones and breccias with Devonian clasts, was investigated by logging of 970 m of outcrop, provenance and palynological analysis, identifying three factors: exhumation of resistant footwall strata; climate change and sea-level rise. Sedimentation rates and lithofacies distribution identified an initial turbidite prone syn-rift phase; MTC dominated rift climax and late stage rifting when sedimentation declined. Thirty-two palynological samples determined palaeoclimate and palaeoenvironment variations; documenting change from humid-temperate to semi-arid. The nature of debris flows implies trigger by earthquakes and their frequency describes three phases of tectonism; turbidites are not distal MTC expressions but correlate with sea-level falls. Temporal and spatial relationships of MTCs and sandstones adjacent to the Josephine Ridge were investigated. One hundred and twenty one palynological samples were used to indicate subaerial exposure of the Judy Horst; Jade remained submerged, with implications for Central Graben palaeogeography. Seismic studies suggest footwall collapse of the horsts provided MTCs. Wireline signatures from sixteen wells and 116.7 m of core demonstrate a Triassic provenance for the MTCs. Distally the massive Freshney Sandstone is interpreted as gravity flow deposits; petrographic and HM studies indicate it was not sourced from the Josephine Ridge. Biostratigraphy shows sandstones were deposited during initial rifting; pre-dating MTCs, which are not predicted to have damaged the reservoir interval due to their non-erosive nature. This study has disentangled the effects of relative sea-level change and growth faulting in rift basins. Rift stages have been identified independently from multiple datasets. The effect of climate change on rift basin stratigraphy has been highlighted and changing footwall lithology has been shown to have a major impact on the development of siliciclastic sediments.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geology ; Geology ; Startigraphic