Sandstone-hosted concretions record evidence for syn-lithification seismicity, cavitation processes, and Palaeocene rapid burial of Lower Cretaceous deep-marine sandstones (Outer Moray Firth, UK North Sea)

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doi: 10.1144/0016-764905-033
Authors:Hendry, James P.; Poulsom, Andrew J.
Author Affiliations:Primary:
University of Portsmouth, School of Earth and Environmental Sciences, Portsmouth, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 163(3), p.447-460. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:2006
Note:In English. 50 refs.; illus., incl. geol. sketch maps, block diag., 1 table, anals.
Summary:Syn- and post-lithification cemented fractures are abundant in concretions formed during shallow burial of Hauterivian turbidites in the Outer Moray Firth. Early fractures are irregular, bifurcating, and contain entrained sand grains. They are confined to the concretion bodies, but commonly splay into narrower fracture swarms at the margins. Multiple, cross-cutting fills of calcite microspar have similar isotopic composition to adjacent concretionary cements, suggesting that rupture and cementation cycles occurred as host concretions lithified. Expulsion of cementing pore fluids from the fractures produced cement protrusions at concretion margins. A hydraulic fracture mechanism resulting from localized permeability heterogeneity and episodic seismic activity is proposed. Rapid seismic loading created high pore fluid pressures for fracture dilation in lithifying concretions and, through cavitation and CO2 degassing, a trigger for rapid homogeneous nucleation of calcite. Many of the early structures were subsequently reactivated as brittle tensile fractures, and host a variety of mesogenetic cements. Reactivation probably occurred in response to stress amplification during rapid Palaeocene burial. By this time lithification of the concretions had dramatically changed their rheology and failure style. Minor permeability remained in the concretion cements adjacent to reactivated fractures, permitting invasion of intercrystalline voids by late diagenetic fluids.
Subsections:Sedimentary petrology
Subjects:Brittle deformation; Burial; Calcite; Carbonates; Cementation; Cenozoic; Clastic rocks; Concretions; Cretaceous; Deformation; Diagenesis; Fabric; Fractures; Isotopes; Jurassic; Kimmeridge Clay; Lithification; Lower Cretaceous; Mesozoic; Microstructure; Paleocene; Paleogene; Permeability; Pore pressure; Porosity; Reactivation; Reservoir rocks; Rifting; Sandstone; Secondary structures; Sedimentary rocks; Sedimentary structures; Seismicity; Solution cavities; Solution features; Stable isotopes; Tertiary; Upper Jurassic; Atlantic Ocean; Europe; Great Britain; Moray Firth; North Atlantic; North Sea; Scotland; United Kingdom; Western Europe; Outer Moray Firth; Valhall Formation; Witch Ground Graben
Coordinates:N580000 N580000 W0000000 W0000000
Abstract Numbers:06M/1921
Record ID:2006037821
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States, Reference includes data from The Geological Society, London
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