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- Volume 18, Issue 3, 2006
Basin Research - Volume 18, Issue 3, 2006
Volume 18, Issue 3, 2006
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Investigating the surface process response to fault interaction and linkage using a numerical modelling approach
Authors P.A. Cowie, M. Attal, G. E. Tucker, A. C. Whittaker, M. Naylor, A. Ganas and G. P. RobertsABSTRACTIn order to better understand the evolution of rift‐related topography and sedimentation, we present the results of a numerical modelling study in which elevation changes generated by extensional fault propagation, interaction and linkage are used to drive a landscape evolution model. Drainage network development, landsliding and sediment accumulation in response to faulting are calculated using CASCADE, a numerical model developed by Braun and Sambridge, and the results are compared with field examples. We first show theoretically how the ‘fluvial length scale’, Lf, in the fluvial incision algorithm can be related to the erodibility of the substrate and can be varied to mimic a range of river behaviour between detachment‐limited (DL) and transport‐limited (TL) end‐member models for river incision. We also present new hydraulic geometry data from an extensional setting which show that channel width does not scale with drainage area where a channel incises through an area of active footwall uplift. We include this information in the coupled model, initially for a single value of Lf, and use it to demonstrate how fault interaction controls the location of the main drainage divide and thus the size of the footwall catchments that develop along an evolving basin‐bounding normal fault. We show how erosion by landsliding and fluvial incision varies as the footwall area grows and quantify the volume, source area, and timing of sediment input to the hanging‐wall basin through time. We also demonstrate how fault growth imposes a geometrical control on the scaling of river discharge with downstream distance within the footwall catchments, thus influencing the incision rate of rivers that drain into the hanging‐wall basin. Whether these rivers continue to flow into the basin after the basin‐bounding fault becomes fully linked strongly depends on the value of Lf. We show that such rivers are more likely to maintain their course if they are close to the TL end member (small Lf); as a river becomes progressively more under supplied, i.e. the DL end member (large Lf), it is more likely to be deflected or dammed by the growing fault. These model results are compared quantitatively with real drainage networks from mainland Greece, the Italian Apennines and eastern California. Finally, we infer the calibre of sediments entering the hanging‐wall basin by integrating measurements of erosion rate across the growing footwall with the variation in surface processes in space and time. Combining this information with the observed structural control of sediment entry points into individual hanging‐wall depocentres we develop a greater understanding of facies changes associated with the rift‐initiation to rift‐climax transition previously recognised in syn‐rift stratigraphy.
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River spacing and drainage network growth in widening mountain ranges
Authors Sébastien Castelltort and Guy SimpsonABSTRACTDrainage networks in linear mountain ranges always display a particular geometrical organisation whereby the spacing between the major drainage basins is on average equal to half the mountain width (distance from the mountain front to the main drainage divide), independent of climate and tectonics. This relationship is valid for mountains having different widths and is thus usually thought to be maintained by drainage reorganisation during mountain belt widening. However, such large‐scale systematic drainage reorganisation has never been evidenced. In this paper, we suggest an alternative explanation, namely that the observed drainage basin relationships are an inherent property of dendritic river networks and that these relationships are established on the undissected, lowland margins outside mountain ranges and are progressively incorporated and quenched into uplifted topography during range widening. Thus, we suggest that the large‐scale geometry of drainage networks in mountain ranges is mainly antecedent to erosion. We propose a model in which the large‐scale drainage geometry is controlled mainly by the geometrical properties of the undissected surfaces (in particular, the ratio of the regional slope to the local slope related to roughness) over which rivers are flowing before uplift, and is therefore independent of climate and tectonics.
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Lithospheric bulge in the West Taiwan Basin
Authors J. Tensi, F. Mouthereau and O. LacombeABSTRACTWe use well data to investigate the timing and the origin of the lithospheric bulge in the West Taiwan Basin. The possibility that the subsidence patterns observed since Middle‐Upper Miocene are simply related to the flexural response of the Chinese continental margin to loading is examined by the reconstructions of the West Taiwan Basin evolution using two‐dimensional geometric and numerical flexural modelling of a purely elastic plate. Reconstructions of the forebulge and basin evolution since Middle Miocene are finally discussed in terms of plate strength and geological context. The results are finally placed in the framework of the geodynamic setting of the Philippines Sea Plate/Eurasia convergence in order to provide new insights on the early stage of the Taiwan arc‐continent collision. Modelling suggests that the initiation of the flexure in the West Taiwan Basin occurred at ca. 12.5–8.6 Ma. A good fit is obtained for Te of 10–20 km, consistent with earlier studies. During 5–6 m year−1 the growth of the bulge was static and associated with increasing plate curvature. Then, at 3–4 Ma the bulge migrated forelandward within the West Taiwan Basin in relation to the migration of the load and the increase in plate curvature. The passage of the forebulge into an inherited weaker portion of the Chinese margin produced an increase in plate curvature and renewed extension, leading to enhancement of the bulge uplift and to its localization for a prolonged period of time. Taking into account the age of the flexure initiation and plate convergence rates, we infer that the load might not be related to the arc‐continent collision. We conclude that a Middle Miocene obduction, already proposed by some authors, may explain the deflection of the Chinese margin at that time. It is not before 3–4 Ma that the bulge and the load propagated forelandward in association with the development of the Taiwan arc‐continent collision.
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Lithological control on thrust‐related deformation in the Sassa‐Guardistallo Basin (Northern Apennines hinterland, Italy)
ABSTRACTThe Sassa‐Guardistallo Basin (SGB) is located close to the Tyrrhenian Sea and represents one of the most internal Neogene–Quaternary hinterland basins of the Northern Apennines fold‐and‐thrust belt. Its sedimentary succession consists of ca. 400‐m‐thick Late Tortonian–Messinian continental – largely conglomeratic – units overstepping a mainly shaly substratum (Palombini Shales) and overlain by Late Messinian evaporites and marine to continental Pliocene–Pleistocene sediments. This stratigraphic succession can be approximated to a composite rheological multilayer that dictated the style of basin deformation. Detailed geological mapping and structural analysis revealed that basin deposits were affected by compressional deformations that can be found both at map and outcrop scales. Decametric splay thrusts emanating from the substratum–conglomerate interface locally double the continental succession and are bounded by a roof thrust along the Late Messinian evaporite décollement, defining a deformation pattern consistent with a duplex‐like structure. The time–space structural evolution of the basin inferred from the fieldwork was addressed and tested by analogue modelling that approximated the rheological stratification of the study area to a layered brittle–ductile system. The model results support the hypothesis that the evolution of the thrust system affecting the SGB started as an early floor imbricate fan thrust system that successively evolved to a duplex structure as the link thrusts propagated into the upper décollement layer that resulted from the deposition of the Late Messinian evaporites. Models display many structural features that may be compared with the natural prototype, and highlight the importance of syntectonic sedimentation in the development and evolution of tectonic structures. The results of this study retain relevant implications for the Neogene evolution of the Tyrrhenian Basin–Northern Apennines system. This study also supports that combining between field structural analyses and analogue modelling can give useful hints into the evolutionary history of tectonically complex areas.
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Three‐dimensional‐seismic coherency signature of Niger Delta growth faults: integrating sedimentology and tectonics
Authors S. Back, C. Höcker, M. B. Brundiers and P. A. KuklaABSTRACTThis case study of growth faults and associated deltaic sedimentation in the shallow‐offshore Niger Delta uses an integrated analysis of three‐dimensional (3D)‐seismic coherence facies and wireline data that supports an evaluation of the sedimentary response to delta tectonics. The study area comprises four fault blocks bounded by a set of kilometre‐scale, basinward‐dipping, synsedimentary normal faults. Correlation of highly variable growth stratigraphy across faults was achieved by a systematic visualization and interpretation of series of coherence horizon‐slices: the detection and matching of erosive and depositional patterns (e.g. channels) across faults allowed the establishment of sedimentology‐controlled links between diverse footwall and hanging‐wall growth successions. At the same time, this interpretation approach helped to visualize seismic‐sedimentological and seismic‐geomorphological features survey‐wide at all depth levels. The integration of this extensive 3D database with lithology information from wireline logs provides a powerful tool for subsurface sedimentology interpretation.
Synoptic analysis of the 3D‐seismic sedimentology interpretation with stratigraphy based fault‐kinematic analysis using throw vs. depth plots (Th–Z plots) enabled a discussion of the relation between delta tectonics and sedimentary‐system development, and the evaluation of the Th–Z method for subsurface‐lithology prediction. The interpretation results document that both motion analysis of synsedimentary deltaic faults and Th–Z‐based lithology prediction are only feasible when supported by detailed 3D information on palaeoenvironment and palaeotopography at and around studied fault systems. We therefore recommend the use of fast‐track fault‐kinematic and subsurface‐lithology predictions based on Th–Z plots only when supported by comprehensive 3D seismic‐sedimentological interpretations.
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Submarine slope failure primed and triggered by silica and its diagenesis
Authors Richard J. Davies and Ian R. ClarkABSTRACTThree‐dimensional seismic analysis of a submarine palaeo‐translational slope failure on the northeast Atlantic margin indicates that it was ‘primed’ and probably ‘triggered’ as a result of diagenesis at a silica chemical reaction front, where biogenic silica (opal A) is being converted to opal CT (Cristobalite/Tridymite). Conversion of opal A to opal CT is a thermochemical dehydration reaction that causes rapid compaction. It therefore is a potential overpressure generation mechanism, usually once sediment has been buried to depths of 300–800 m below the contemporaneous seabed. The overpressure reduces the sediment shear strength, making it susceptible to failure. In this example, the translated succession (volume of 25 km3 and area of 110 km2) was coherent and rigid but the detachment unit was a liquified sediment mass. After failure, the translated succession broke up into a series of faulted‐bounded blocks, which differentially subsided into this underlying sediment‐fluid mass. Sediment‐fluid intrusions utilized the faults bounding the blocks, intruding 200–400 m of the overburden stratigraphy to expel a fluid–sediment mix into the water column and onto the palaeoseabed. Pore pressure decreased and sediment strength within the detachment unit was re‐established. Key factors for the initiation of this failure mechanism are (a) the rate of the reaction front advancement (ROFA), (b) the magnitude of the porosity reduction at the reaction front, (c) the sealing capabilities of the overburden and (d) the low shear strength of opal A. Given that the reaction front normally forms at depths of 300–800 m, the mechanism is more likely to induce deep and therefore large volume detachments, which should be more common in high latitude and equatorial regions where biogenic silica production is high.
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Burial/exhumation histories for the Cooper–Eromanga Basins and implications for hydrocarbon exploration, Eastern Australia
More LessABSTRACTThe Cooper–Eromanga Basins of South Australia and Queensland are not at their maximum burial depth due to Late Cretaceous–Tertiary, and Late Triassic–Early Jurassic exhumation. Apparent exhumation (maximum burial depth–present burial depth) for the Cooper Basin has been quantified using the compaction methodology. The results show that exhumation of the Cooper Basin for the majority of the wells is greater than the exhumation of the Eromanga Basin. Using the compaction methodology, apparent exhumation of Early to Middle Triassic age Arrabury and Tinchoo Formatios has been quantified. Both units yield similar results and do not support that the Arrabury/Tinchoo boundary represents the Cooper–Eromanga boundary. Hence, the Cooper Basin is believed to have reached its maximum burial depth in Late Triassic times. Sonic log data are not available for the units overlying the Late Cretaceous Winton Formation; thus, it is not possible to date exhumation beyond the Late Cretaceous–Tertiary using the compaction methodology. Tertiary sequences as are preserved are relatively thin and separated by marked unconformities and weathered surfaces; hence, exhumation rather than sedimentation dominated the Tertiary, and in exhumed areas, maximum burial depth was attained in Late Cretaceous times. The burial/exhumation history of representative wells was synthesized using sediment decompaction and establishing porosity/depth relations for the Cooper–Eromanga units. Considering the relative significance of the major periods of exhumation in the Cooper/Eromanga Basins, three broad types of burial/exhumation histories can be distinguished. Maximum burial depth of the Cooper Basin sequence was attained before the deposition of the Eromanga Basin sequence, i.e. Late Triassic–Early Jurassic times; maximum burial depth of the Cooper and Eromanga Basin sequences attained in Late Cretaceous times; and Cooper and Eromanga Basin sequences are currently at maximum burial‐depth. Incorporation of exhumation into burial history has major implications for hydrocarbon exploration.
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Volumes & issues
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Volume 36 (2024)
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Volume 35 (2023)
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Volume 34 (2022)
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Volume 33 (2021)
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Volume 32 (2020)
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Volume 31 (2019)
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Volume 30 (2018)
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Volume 29 (2017)
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Volume 28 (2016)
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Volume 27 (2015)
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Volume 26 (2014)
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Volume 25 (2013)
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Volume 24 (2012)
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Volume 23 (2011)
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Volume 22 (2010)
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Volume 21 (2009)
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Volume 20 (2008)
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Volume 19 (2007)
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Volume 18 (2006)
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Volume 17 (2005)
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Volume 16 (2004)
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Volume 15 (2003)
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Volume 14 (2002)
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Volume 13 (2001)
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Volume 12 (2000)
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Volume 11 (1999)
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Volume 10 (1998)
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Volume 9 (1997)
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Volume 8 (1996)
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Volume 7 (1994)
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Volume 6 (1994)
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Volume 5 (1993)
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Volume 4 (1992)
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Volume 3 (1991)
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Volume 2 (1989)
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Volume 1 (1988)