Early synrift reservoir development on the flanks of extensional forced folds: A seismic-scale outcrop analog from the Hadahid fault system, Suez rift, Egypt

Lewis, Matthew M.; Jackson, Christopher; Gawthorpe, Robert L.; Whipp, Paul S.

doi:10.1306/12011414036

Cited by 27 publications

(57 citation statements)

References 36 publications

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“…Irrespective of its origin, a consequence of this unusual structural style is that the stratigraphic architecture and thickness patterns in the syn‐rift succession are unlike that documented in many rift basins (cf. Davies et al ., ; McLeod et al ., ; Lewis et al ., ). The lowermost syn‐rift stratal unit thickens and diverges towards the fault, which is characteristic of syn‐rift growth sequences (SRM1; Figs and ).…”

Section: Discussionmentioning

confidence: 97%

Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

et al. 2015

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Rift basin tectono-stratigraphic models indicate that normal fault growth controls the sedimentology and stratigraphic architecture of syn-rift deposits. However, such models have rarely been tested by observations from natural examples and thus remain largely conceptual. In this study we integrate 3D seismic reflection, and biostratigraphically constrained core and wireline log data from the Vingleia Fault Complex, Halten Terrace, offshore Mid-Norway to test rift basin tectono-stratigraphic models. The geometry of the basin-bounding fault and its hangingwall, and the syn-rift stratal architecture, vary along strike. The fault is planar along a much of its length, bounding a half-graben containing a faultward-thickening syn-rift wedge. Locally, however, the fault has a ramp-flat-ramp geometry, with the hangingwall defined by a fault-parallel anticline-syncline pair. Here, an unusual bipartite syn-rift architecture is observed, comprising a lower faultward-expanding and an upper faultward-thinning wedge. Fine-grained basinfloor deposits dominate the syn-rift succession, although isolated coarse clastics occur. The spatial and temporal distribution of these coarse clastics is complex due to syn-depositional movement on the Vingleia Fault Complex. High rates of accommodation generation in the fault hangingwall led to aggradational stacking of fan deltas that rapidly (<5 km) pinch out basinward into offshore mudstone. In the south of the basin, rapid strain localization meant that relay ramps were short-lived and did not represent major, long-lived sediment entry points. In contrast, in the north, strain localization occurred later in the rift event, thus progradational shorefaces developed and persisted for a relatively long time in relay ramps developed between unlinked fault segments. The footwall of the Vingleia Fault Complex was characterized by relatively low rates of accommodation generation, with relatively thin, progradational hangingwall shorelines developed downdip of the fault block apex, sometime after the onset of sediment supply to the hangingwall. We show that rift basin tectono-stratigraphic models need modifying to take into account along-strike variability in fault structure and basin physiography, and the timing and style of syn-rift sediment dispersal and facies, in both hangingwall and footwall locations.

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Section: Discussionmentioning

confidence: 97%

Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

et al. 2015

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“…Extensional forced folding can control the stratal architecture of and facies distributions within early syn‐rift deposits (e.g. Gawthorpe et al ., ; Gupta et al ., ; Corfield & Sharp, ; Dawers & Underhill, ; Sharp et al ., ; Maurin & Niviere, ; Gawthorpe et al ., ; Ford et al ., ; Lewis et al ., ). Our observations from the Abura Graben further highlights the key role that forced folding has on basin physiography during the early stage of rifting and provides a rare insight into the detailed, sub‐seismic stratal architecture associated with this structural style.…”

Section: Discussionmentioning

confidence: 97%

Tectono‐sedimentary development of early syn‐rift deposits: the Abura Graben, Suez Rift, Egypt

2015

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The thickness and distribution of early syn-rift deposits record the evolution of structures accommodating the earliest phases of continental extension. However, our understanding of the detailed tectono-sedimentary evolution of these deposits is poor, because in the subsurface, they are often deeply buried and below seismic resolution and sparsely sampled by borehole data. Furthermore, early syn-rift deposits are typically poorly exposed in the field, being buried beneath thick, late synrift and post-rift deposits. To improve our understanding of the tectono-sedimentary development of early syn-rift strata during the initial stages of rifting, we examined quasi-3D exposures in the Abura Graben, Suez Rift, Egypt. During the earliest stage of extension, forced folding above blind normal fault segments, rather than half-graben formation adjacent to surface-breaking faults, controlled rift physiography, accommodation development and the stratigraphic architecture of nonmarine, early syn-rift deposits. Fluvial systems incised into underlying pre-rift deposits and were structurally focused in the axis of the embryonic depocentre, which, at this time, was characterized by a fold-bound syncline rather than a fault-bound half graben. During this earliest phase of extension, sediment was sourced from the rift shoulder some 3 km to the NE of the depocentre, rather than from the crests of the flanking, intra-basin extensional forced folds. Fault-driven subsidence, perhaps augmented by a eustatic sea-level rise, resulted in basin deepening and the deposition of a series of fluvial-dominated mouth bars, which, like the preceding fluvial systems, were structurally pinned within the axis of the growing depocentre, which was still bound by extensional forced folds rather than faults. The extensional forced folds were eventually locally breached by surface-breaking faults, resulting in the establishment of a half graben, basin deepening and the deposition of shallow marine sandstone and fan-delta conglomerates. Because growth folding and faulting were coeval along-strike, syn-rift stratal units deposited at this time show a highly variable along-strike stratigraphic architecture, locally thinning towards the growth fold but, only a few kilometres alongstrike, thickening towards the surface-breaking fault. Despite displaying the classic early syn-rift stratigraphic motif recording net upward-deepening, extensional forced folding rather than surface faulting played a key role in controlling basin physiography, accommodation development, and synrift stratal architecture and facies development during the early stages of extension. This structural and stratigraphic observations required to make this interpretation are relatively subtle and may go unrecognized in low-resolution subsurface data sets.

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“…This is not to suggest that some cover materials cannot be adequately simulated using either homogenous frictional-cohesive or elastic but rather that, in many examples, mechanical heterogeneity is very important (cf. Corfield & Sharp, 2000;Jackson et al, 2006;Lewis, Jackson, Gawthorpe, & Whipp, 2015;Conneally, Childs, & Nicol, 2017). In these initial models the growth strata included have been considered to be very weak (without friction, cohesion or bonding) and thus behave quite differently to the underlying pregrowth sequence, leading to a degree of decoupling of the growth from the pregrowth sequence.…”

Section: Discussionmentioning

confidence: 99%

“…As a result, predicting the geometry/architecture, thickness and location of both pregrowth and growth reservoirs can prove difficult (e.g. Corfield & Sharp, 2000;Jackson et al, 2006;Lewis et al, 2015). The approach used here to simulate or 'promote' flexural slip between defined layers in the cover materials is probably one of the simplest possible.…”

Section: Discussionmentioning

confidence: 99%

Discrete element modelling of extensional, growth, fault‐propagation folds

Hardy

2019

Basin Research

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Extensional fault‐propagation folds are now recognised as being an important part of basin structure and development. They have a very distinctive expression, often presenting an upward‐widening monocline, which is subsequently breached by an underlying, propagating fault. Growth strata, if present, are thought to provide a crucial insight into the manner in which such structures grow in space and time. However, interpreting their stratigraphic signal is neither straightforward nor unique. Both analogue and numerical models can provide some insight into fold growth. In particular, the trishear kinematic model has been widely adopted to explain many aspects of the evolution and geometry of such fault‐propagation folds. However, in some cases the materials/rheologies used to represent the cover do not reproduce the key geometric/stratigraphic features of such folds seen in nature. This appears to arise from such studies not addressing adequately the very heterogenous mechanical stratigraphy seen in many sedimentary covers. In particular, flexural slip between beds/layers is often not explicitly modelled but, paradoxically, it appears to be an important deformation mechanism operative in such settings. Here, I present a 2D discrete element model of extensional fault‐propagation folding which explicitly includes flexural slip between predefined sedimentary units or layers in the cover. The model also includes growth strata and shows how they may reflect the various evolutionary stages of fold and fault growth. When flexural slip is included in the modelling scheme, the resultant breached monoclines and their growth strata are strikingly similar to some of those seen in nature. Results are also compared with those obtained using simple, homogeneous, frictional‐cohesive and elastic cover materials. Both un‐lithified and lithified growth strata are considered and clearly show that, rather than just being passive recorders of structural evolution, growth strata can themselves have an important effect on fault‐related fold growth. Implications for the evolution of and strain within, the resultant growth structures are discussed. A final focus of this study is the relationship that trishear might have with the upward‐widening zone of flexural slip activation away from a fault tip singularity.

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Early synrift reservoir development on the flanks of extensional forced folds: A seismic-scale outcrop analog from the Hadahid fault system, Suez rift, Egypt

Cited by 27 publications

References 36 publications

Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

Late syn‐rift evolution of the Vingleia Fault Complex, Halten Terrace, offshore Mid‐Norway; a test of rift basin tectono‐stratigraphic models

Tectono‐sedimentary development of early syn‐rift deposits: the Abura Graben, Suez Rift, Egypt

Discrete element modelling of extensional, growth, fault‐propagation folds

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