3D geometry of a shale-cored anticline in the western South Caspian Basin (offshore Azerbaijan)

Betancor, I. Santos; Soto, Juan I.

doi:10.1016/j.marpetgeo.2015.06.012

Cited by 9 publications

(4 citation statements)

References 54 publications

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“…The seismic characteristics of the mud pipes, their cylindrical 3D geometry, their position at the anticline crests, as well as the nature of their contacts with the host rock suggest the existence of pervasive fluid migration from the mobilized, overpressured muds along these conduits piercing the country sediments (e.g. Kopf, 2002;Santos Betancor & Soto, 2015). Note: See also Basinward and landward (counterregional)…”

Section: Mud Pipesmentioning

confidence: 99%

“…Shale‐rich, deltaic continental margins may be characterized by thin‐skinned, gravity‐driven deformation above an unconsolidated, overpressured, buried shale (e.g. Briggs et al, 2006; Cohen & McClay, 1996; Damuth, 1994; Espurt et al, 2009; Morley & Guerin, 1996; Morley et al, 2011; Rowan, 2020; Santos Betancor & Soto, 2015; Zhang et al, 2021). However, difficulties with seismically imaging mobilized shale bodies mean that we have a poor understanding of the shape and size of these bodies, and of their mechanisms (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Extensional deformation of a shale‐dominated delta: Tarakan Basin, offshore Indonesia

2023

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Deformation on shale-rich continental margins is commonly associated with thin-skinned extension above mobile shales. Normal faulting and shale mobilization are widespread on such margins, being associated with and controlled by progradation and gravitational failure of deltaic sedimentary wedges. However, due to uncertainties in seismically imaging mobile shales, our understanding of problems like how base mobile-shale controls deformation, and the shape, size, and distribution of shale structures remain poorly understood. We here use 3D seismic reflection data from the platform region of the Tarakan Basin, offshore eastern Indonesia to investigate the temporal and spatial evolution of thin-skinned deformation of the Neogene sedimentary section.Our detailed seismic interpretation reveals up to 74 km long, concave-and convex-into-the-basin normal faults, dipping both basinward (eastwards) and locally landward (westwards), which detach downwards on a basal mobile shale (Early-Middle Miocene). The base of the mobile shale unit dips gently (< 17 o ) seaward, although older (Eocene-Early Miocene), rift-related normal faults originate local structural highs deforming the base of mobile shales. Our isochore (thickness map) analysis shows that supra-shale normal faulting commenced in the Middle Miocene and was accompanied by the formation of hanging-wall rollover folds and associated crestal grabens, with the subsequent along-and across strike migration of the deformation related to the nucleation, lateral linkage, and reactivation of individual fault systems. Updip growth normal faulting was also accompanied by the downslope flow of mobile shale, accompanied by parallel and perpendicular variations of the differential loading in the delta system, and local contraction and mobile shale-upbuilding, resulting in the growth of large, margin-parallel shale anticlines further downdip. The growth faults and anticlines are locally overlain by up to 5 km tall of mud pipes and volcanoes. We suggest that variations in the rate of sedimentary loading, mobile shale flow, fault growth, and gravitational failure of the delta system above a seaward-dipping, but locally rugose base mobile-shale surface, controlled Neogene deformation in the Tarakan Basin. We also demonstrate how variations in the trend and dip of the base mobile-shale surface influences the position, timing of formation, and evolution of supra-shale normal faults and their associated depocenters along shale-rich, deltaic margins.

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Section: Mud Pipesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Extensional deformation of a shale‐dominated delta: Tarakan Basin, offshore Indonesia

2023

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“…For example, in Azerbaijan and the Caspian basin, many mud volcanoes occur along normal faults formed over the crests of compressional anticlines (e.g. Bonini & Mazzarini, 2010; Fowler et al., 2000; Hovland et al., 1997; Omrani & Raghimi, 2018; Oppo & Capozzi, 2016; Santos Betancor & Soto, 2015).…”

Section: Shale Piercement Mechanismsmentioning

confidence: 99%

“…In many cases, mud and breccia clasts brought up in mud volcanoes come from units many kilometres in the subsurface. For example, in the South Caspian Basin, the Maykop Formation (the primary source of the muds in the mud volcanoes) can lie as much as 9 km below the volcanoes (Fowler et al., 2000; Inan et al., 1997; Omrani & Raghimi, 2018; Planke et al., 2003; Santos Betancor & Soto, 2015). Published seismic images of fracture systems feeding mud volcanoes show the fractures reaching to depths of up to 2.6 km below the volcano, nearly to the top of the source bed (e.g.…”

Section: Shale Piercement Mechanismsmentioning

confidence: 99%

Piercement mechanisms for mobile shales

Hudec

Soto

2021

Basin Research

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We have identified seven mechanisms by which mobile shales can pierce their roofs. The operative piercement mechanism depends on mobile‐shale viscosity, roof strength and stress state. For mobile shales at depths of several kilometres, three mechanisms are possible: fracture piercement, thrust piercement and ductile “piercement.” However, injection up fractures and faults appears to be the dominant mechanism by which mobile shales rise towards the surface. In this process, mobile shales behave similar to magmas rising through the Earth's crust. Nearer the surface, a wider range of piercement mechanisms becomes possible: passive piercement, reactive piercement, active piercement and erosional piercement. These mechanisms all have salt‐tectonics analogues. Although shale tectonics and salt tectonics share common piercement mechanisms, in many cases the resulting structures are different. This is because near‐surface mobile shales can have much lower viscosities than salt. Mobile shales that reach the surface extrude very rapidly, in many cases leading to caldera collapse of the underlying shale chamber. This instability in the near‐surface means that long‐term, stable growth of passive shale diapirs is unlikely, in contrast with the behaviour of salt. A key question in seismic interpretation of mobile‐shale structures is whether large‐volume mobile‐shale diapirs exist. We show that both active piercement and ductile “piercement” can create such structures. Both of these mechanisms create steeply upturned beds on diapir flanks, which are diagnostic. However, active shale diapirs appear to be rare, and ductile “piercements” are not documented. We therefore suggest that large‐volume shale diapirs should be interpreted with caution on seismic data.

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Mudrock overpressure, fracturing, and mud volcanism in the Lower Kura Depression, Azerbaijan

İnan,

Namazlı,

Askerova

et al. 2024

Int J Earth Sci (Geol Rundsch)

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3D geometry of a shale-cored anticline in the western South Caspian Basin (offshore Azerbaijan)

Cited by 9 publications

References 54 publications

Extensional deformation of a shale‐dominated delta: Tarakan Basin, offshore Indonesia

Extensional deformation of a shale‐dominated delta: Tarakan Basin, offshore Indonesia

Piercement mechanisms for mobile shales

Mudrock overpressure, fracturing, and mud volcanism in the Lower Kura Depression, Azerbaijan

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