Quantification of Tertiary exhumation from sonic velocity data, Celtic Sea/Southwestern Approaches

Menpes, Robert J.; Hillis, Richard R.

doi:10.1144/gsl.sp.1995.093.01.23

Cited by 10 publications

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Section: Methodsmentioning

confidence: 99%

“…buried shallower than they have been in the past) will exhibit anomalously low porosity ('burial anomaly' of Japsen 1998). Our approach follows that described in detail by Menpes & Hillis (1995) in which interval transit times (ITT -the reciprocal of interval velocity) from wells drilled in an exhumed basin are compared with a normal compaction curve for a ubiquitous, uniform lithology (Mercia Mudstone Formation):where m 1 is the gradient of the normal compaction trend, t u is the mean formation ITT for each well, o t  is the constant of the normal compaction trend (i.e. ITT of uncompacted sediment) and d u is the depth of the formation midpoint below the seabed (see also Fig.…”

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confidence: 99%

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Inversion and exhumation of the St. George's Channel basin, offshore Wales, UK

Williams

Turner

Holford

2005

JGS

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The western UK basins of the Irish Sea have provided one of the best natural laboratories for investigating the causes and consequences of intracratonic uplift and erosion (exhumation). To date, the emphasis has been on igneous underplating as the chief process driving their exhumation. In this paper, we demonstrate that tectonic inversion -the shortening of formerly extensional basins and reactivation of their constituent faults -dominated the exhumation of the St. George's Channel basin, offshore Wales. Based on mapping of an extensive 2D seismic grid, evidence is presented for at least two major inversion episodes in the Late Cretaceous and the Neogene, plus minor shortening during the Eocene. Inversion was distinctly noncoaxial, especially during the Neogene when coeval transpression and transtension was focused at discrete bends and stepovers on the basin-bounding St.George's, Bala and Northwest Flank faults. That the principal mechanism driving these uplift episodes was inversion (as opposed to igneous underplating) is corroborated by analysis of thermal history data (apatite fission track and vitrinite reflectance). They reveal late Cretaceous and Neogene geothermal gradients that were comparable with the present day i.e. no significant increase in basal heatflow. Sonic velocity profiles logged in hydrocarbon boreholes constrain the minimum thickness of the eroded section which varies between c.1000m in the centre and c.2240m at the margins of the basin. Given the strength of evidence for tectonic inversion in the St. George's Channel basin, our favoured model invokes superimposition of the effects of inversion and igneous underplating to account for the complex exhumation history of the St. George's Channel basin in particular, and the western UK basins in general. KEYWORDS:ABBREVIATED TITLE: Inv. & Exh. of the SGCB 2 2 Intracratonic basinsadjacent to 'passive' ocean margins undergo uplift in response to a diverse range of processes related chiefly to i) epeirogeny (i.e uplift of broad regions of continental interiors), and ii) intraplate shortening and tectonic inversion. Sedimentary basin inversion, the compressional or transpressional reactivation and shortening of formerly extensional basins, can have a marked influence on the structure and evolution of the basin fill. It follows that inversion has major implications for the exhumation of petroliferous basins, where the attendant cooling and lithostatic pressure release affects hydrocarbon generation and retention directly (e.g. Dore et al. 2002).Reconstructing the tectonic history of the western UK basins is hampered by the difficulty in recognizing and discriminating the superimposed effects of epeirogeny and inversion. This paper reports on the results of recent mapping of an extensive seismic dataset imaging the SE margin of the St. George's Channel basin (SGCB; Fig. 1). The focus of this mapping has been to determine the geometry, kinematics and timing of deformation associated with the Cretaceous-Cenozoic inversion of the NW European 'A...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Inversion and exhumation of the St. George's Channel basin, offshore Wales, UK

Williams

Turner

Holford

2005

JGS

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“…Hillis (1995), Menpes and Hillis (1995), Japsen (1998), Densley et al (2000), Ware and Turner (2002) have all exploited seismic velocity-depth anomalies to infer the magnitude of missing section around the North Sea, Irish Sea and Australia. In general, the applications use shale or chalk velocities, as these tend to be less variable than sandstones, as a consequence of diagenetic effects, or lack thereof.…”

Section: Pressure-sensitive Methodsmentioning

confidence: 99%

Uplift, denudation, and their causes and constraints over geological timescales

Gallagher

2012

Phanerozoic Regional Geology of the World

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We define uplift and denudation, then review the basic principles underlying the mechanisms for producing uplift, and the methodologies used to quantify the geological timescale denudation history of uplifted regions. Uplift is represents work done against gravity, and does not necessarily lead immediately to rapid denudation. The causes of uplift can be categorised according to the principal driving mechanism -stress, thermal or gravitational factor, although all three can operate to varying degrees. Simple formulations and examples. are presented to demonstrate the magnitude of uplift in various situations. The magnitude of denudation over geological timescales is quantified through various methods, which are sensitive to depth, pressure or temperature. These include cosmogenic surface exposure dating, thermochronology (apatite fission track analysis, (U-Th)/He dating), porosity-depth relationship (overcompaction), and by comparing predicted subsidence to the observed subsidence history.3

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“…In addition, studies such as Hillis (1995) which derive statistically similar apparent exhumation estimates from different formations and different lithologies, also increase the confidence in the normal compaction relation of each formation. Skagen (1992) suggested that shale compaction-based estimates of exhumation have a potential accuracy of ±200 m. Menpes & Hillis (1995) examined the spread of the sonic logs of the reference wells around the normal compaction relation for the Upper Cretaceous Chalk in the Celtic Sea/South-Western Approaches, and suggested that an empirical estimate of the error in the apparent exhumation relation was ± 250 m. A potential error in the normal compaction relation of ± 250 m is also suggested for this study.…”

Section: Barmston-1mentioning

confidence: 99%

Determining apparent exhumation from Chalk outcrop samples, Cleveland Basin/East Midlands Shelf

Menpes

Hillis

1996

Geol. Mag.

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-Porosity measurements of 22 Upper Cretaceous Chalk samples, and mean Chalk porosities derived from sonic logs in three wells, were used to quantify apparent exhumation (height above maximum burial-depth) in the onshore Cleveland Basin/East Midlands Shelf. Late Cretaceous/Tertiary exhumation of the East Midlands Shelf resulted in the removal of 1.2 km of section near the coast and more than 2 km of section inland, to the west. The southern margin of the Cleveland Basin was exhumed by 2 km, and exhumation increases northwards towards the recognized inversion axis running east-west along the basin's centre. The northwards increasing exhumation associated with the east-west trending inversion axis of the Cleveland Basin is superimposed upon the regional westward trend of increasing exhumation of eastern England. These two trends control the outcrop distribution of the Upper Cretaceous Chalk in the Cleveland Basin/East Midlands Shelf.

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Quantification of Tertiary exhumation from sonic velocity data, Celtic Sea/Southwestern Approaches

Cited by 10 publications

References 0 publications

Inversion and exhumation of the St. George's Channel basin, offshore Wales, UK

Inversion and exhumation of the St. George's Channel basin, offshore Wales, UK

Uplift, denudation, and their causes and constraints over geological timescales

Determining apparent exhumation from Chalk outcrop samples, Cleveland Basin/East Midlands Shelf

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