Outlining of Shale Masses by Geophysical Methods

Musgrave, A. W.; Hicks, Warren G.

doi:10.1190/1.1439805

Cited by 41 publications

(11 citation statements)

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“…The concept of mobile shale was formed in the 1960s (Musgrave and Hicks, 1966) and has been cited as a common interpretation where thick sequences of mudrocks exist through to recent times (Morley, 2003). If shale is unable to flow, i.e., deforming by brittle failure instead of a plastic flow, and is unable to effectively fill the shape of the void created, strain compatibility problems may occur within the core of detachment folds where the redistribution of relatively incompetent material occurs.…”

Section: Reinterpretation Of Mobile Shale In the South Niger Deltamentioning

confidence: 99%

New insights into deformation mechanisms in the gravitationally driven Niger Delta deep-water fold and thrust belt

et al. 2010

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Section: Reinterpretation Of Mobile Shale In the South Niger Deltamentioning

confidence: 99%

New insights into deformation mechanisms in the gravitationally driven Niger Delta deep-water fold and thrust belt

et al. 2010

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“…Additionally, chaotic seismic facies in the subsurface of many continental margins are often interpreted as 'mud' or 'shale diapirs' due to their resemblance to salt diapirs (e.g. Musgrave & Hicks, 1968;Lancelot & Embley, 1977;Morley & Guerin, 1996;Morley, 2003;L eon et al, 2010). In these studies, the terms 'mud diapir', 'clay diapir', 'shale diapir' and 'mudstone diapir' have been used somewhat interchangeably (Milkov, 2000;Wood, 2010; e.g.…”

Section: Mud Diapirs Versus Shale Diapirsmentioning

confidence: 99%

Early burial mud diapirism and its impact on stratigraphic architecture in the Carboniferous of the Shannon Basin, County Clare, Ireland

et al. 2018

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Delta fronts are often characterized by high rates of sediment supply that result in unstable slopes and a wide variety of soft‐sediment deformation, including the formation of overpressured and mobile muds that may flow plastically during early burial, potentially forming mud diapirs. The coastal cliffs of County Clare, western Ireland, expose Pennsylvanian (Namurian) delta‐front deposits of the Shannon Basin at large scale and in three dimensions. These deposits include decametre‐scale, internally chaotic mudstone masses that clearly impact the surrounding sedimentary strata. Evidence indicates that these were true mud (unlithified sediment) diapirs that pierced overlying strata. This study documents a well‐exposed ca 20 m tall mud diapir and its impact on the surrounding mouth‐bar deposits of the Tullig Cyclothem. A synsedimentary fault and associated rollover dome, evident from stratal thicknesses and the dip of the beds, define one edge of the diapir. These features are interpreted as recording the reactive rise of the mud diapir in response to extensional faulting along its margin. Above the diapir, heterolithic sandstones and siltstones contain evidence for the creation of localized accommodation, suggesting synsedimentary filling, tilting and erosion of a shallow sag basin accommodated by the progressive collapse of the diapir. Two other diapirs are investigated using three‐dimensional models built from ‘structure from motion’ drone imagery. Both diapirs are interpreted to have grown predominantly through passive rise (downbuilding). Stratal relationships for all three diapirs indicate that they were uncompacted and fluid‐rich mud beds that became mobilized through soft‐sediment deformation during early burial (i.e. <50 m, likely <10 m depth). Each diapir locally controlled the stratigraphic architecture in the shallow subsurface and potentially influenced local palaeocurrents on the delta. The mud diapirs studied herein are distinct from deeper ‘shale diapirs’ that have been inferred from seismic sections worldwide, now largely disputed.

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“…However, in certain instances it may be possible to draw reliable inferences about fluid pressure indirectly. The tendency of certain overpressured shales to flow [Musgrave and Hicks, 1968;Pritchett, 1980] presumably indicates fluid pressures near lithostatic load. Along similar lines, Walder and Nur [1984] have suggested that seismic low-velocity zones in the crust may indicate regions of crystalline rock with nearly lithostatic fluid pressures.…”

Section: The Field Problemmentioning

confidence: 99%

Groundwater Flow in Low‐Permeability Environments

Neuzil¹

1986

Water Resources Research

359

217

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Certain geologic media are known to have small permeability; subsurface environments composed of these media and lacking well developed secondary permeability have groundwater flow sytems with many distinctive characteristics. Moreover, groundwater flow in these environments appears to influence the evolution of certain hydrologic, geologic, and geochemical systems, may affect the accumulation of pertroleum and ores, and probably has a role in the structural evolution of parts of the crust. Such environments are also important in the context of waste disposal. This review attempts to synthesize the diverse contributions of various disciplines to the problem of flow in low‐permeability environments. Problems hindering analysis are enumerated together with suggested approaches to overcoming them. A common thread running through the discussion is the significance of size‐ and time‐scale limitations of the ability to directly observe flow behavior and make measurements of parameters. These limitations have resulted in rather distinct small‐ and large‐scale approaches to the problem. The first part of the review considers experimental investigations of low‐permeability flow, including in situ testing; these are generally conducted on temporal and spatial scales which are relatively small compared with those of interest. Results from this work have provided increasingly detailed information about many aspects of the flow but leave certain questions unanswered. Recent advances in laboratory and in situ testing techniques have permitted measurements of permeability and storage properties in progressively “tighter” media and investigation of transient flow under these conditions. However, very large hydraulic gradients are still required for the tests; an observational gap exists for typical in situ gradients. The applicability of Darcy's law in this range is therefore untested, although claims of observed non‐Darcian behavior appear flawed. Two important nonhydraulic flow phenomena, osmosis and ultrafiltration, are experimentally well established in prepared clays but have been incompletely investigated, particularly in undisturbed geologic media. Small‐scale experimental results form much of the basis for analyses of flow in low‐permeability environments which occurs on scales of time and size too large to permit direct observation. Such large‐scale flow behavior is the focus of the second part of the review. Extrapolation of small‐scale experimental experience becomes an important and sometimes controversial problem in this context. In large flow systems under steady state conditions the regional permeability can sometimes be determined, but systems with transient flow are more difficult to analyze. The complexity of the problem is enhanced by the sensitivity of large‐scale flow to the effects of slow geologic processes. One‐dimensional studies have begun to elucidate how simple burial or exhumation can generate transient flow conditions by changing the state of stress and temperature and by burial metamorphism. Invest...

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Outlining of Shale Masses by Geophysical Methods

Cited by 41 publications

References 0 publications

New insights into deformation mechanisms in the gravitationally driven Niger Delta deep-water fold and thrust belt

New insights into deformation mechanisms in the gravitationally driven Niger Delta deep-water fold and thrust belt

Early burial mud diapirism and its impact on stratigraphic architecture in the Carboniferous of the Shannon Basin, County Clare, Ireland

Groundwater Flow in Low‐Permeability Environments

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