Palaeothermal and compaction studies in the Mochras borehole (NW Wales) reveal early Cretaceous and Neogene exhumation and argue against regional Palaeogene

Abstract: The North Atlantic continental margins have been subject to widespread exhumation, although the timing, magnitude and causes of this uplift and erosion are debated. Exhumation is thought to be most severe across the Irish Sea basin system (Western UK), and recent years have seen an increas...

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Bibliographic Details
Main Authors: Simon P. Holford, Paul F. Green, Jonathan P. Turner
Other Authors: The Pennsylvania State University CiteSeerX Archives
Format: Text
Language:English
Subjects:
Irish Sea
apatite fission-track analysis
vitrinite reflectance
compaction
North Atlantic
Online Access:http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.536.2505
http://www.geotrack.com.au/papers/holford_et_al_mochras_bh_jgs.pdf
Description
Summary:Abstract: The North Atlantic continental margins have been subject to widespread exhumation, although the timing, magnitude and causes of this uplift and erosion are debated. Exhumation is thought to be most severe across the Irish Sea basin system (Western UK), and recent years have seen an increasing emphasis on the role of Palaeogene underplating as the primary mechanism of uplift. We present a study of palaeothermal and compaction data from the Mochras borehole (NW Wales). Located near the presumed locus of exhumation, Mochras penetrated thick successions of Lower Jurassic and Oligo-Miocene sediments. Our results indicate that both these successions experienced considerably deeper burial prior to early Cretaceous and Neogene exhumation, respectively. Apatite fission-track analysis (AFTA) and vitrinite reflectance data from the borehole reveal evidence for exhumation-related cooling episodes beginning during the Cretaceous (150–80 Ma) and Cenozoic (50–0 Ma). Regional AFTA results and stratigraphic constraints refine the timing estimates to the early Cretaceous (120–115 Ma) and Neogene (20–0 Ma). Estimates of exhumation magnitudes during these episodes based on palaeothermal and compaction data are c. 2.5 km and c. 1.5 km, respectively. Palaeothermal data provide no evidence for elevated Palaeogene palaeotemperatures indicative of deeper burial, and thus question the basis of Palaeogene exhumation.

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