71 results found
Allen PA, Michael NA, D'Arcy M, et al., 2017, Fractionation of grain size in terrestrial sediment routing systems, BASIN RESEARCH, Vol: 29, Pages: 180-202, ISSN: 0950-091X
Armitage JJ, Burgess PM, Hampson GJ, et al., 2016, Deciphering the origin of cyclical gravel front and shoreline progradation and retrogradation in the stratigraphic record, Basin Research, ISSN: 0950-091X
© 2016 John Wiley & Sons Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists. Nearly all successions of the near-shore strata exhibit cyclical movements of the shoreline, which have commonly been attributed to cyclical oscillations in relative sea level (combining eustasy and subsidence) or, more rarely, to cyclical variations in sediment supply. It has become accepted that cyclical change in sediment delivery from source catchments may lead to cyclical movement of boundaries such as the gravel front, particularly in the proximal segments of sediment-routing systems. In order to quantitatively assess how variations in sediment transport as a consequence of change in relative sea-level and surface run-off control stratigraphic architecture, we develop a simple numerical model of sediment transport and explore the sensitivity of moving boundaries within the sediment-routing system to change in upstream (sediment flux, precipitation rate) and downstream (sea level) controls. We find that downstream controls impact the shoreline and sand front, while the upstream controls can impact the whole system depending on the amplitude of change in sediment flux and precipitation rate. The model implies that under certain conditions, the relative movement of the gravel front and shoreline is a diagnostic marker of whether the sediment-routing system experienced oscillations in sea level or climatic conditions. The model is then used to assess the controls on stratigraphic architecture in a well-documented palaeo-sediment-routing system in the Late Cretaceous Western Interior Seaway of North America. Model results suggest that significant movement of the gravel front is forced by pronounced (±50%) oscillations in precipitation rate. The absence of such movement in gravel front position in the studied strata implies that time-equivalent movement of the shoreline was driven by relative sea-level change. We
Burgess PM, Allen PA, Steel RJ, 2016, Introduction to the future of sequence stratigraphy: evolution or revolution?, JOURNAL OF THE GEOLOGICAL SOCIETY, Vol: 173, Pages: 801-802, ISSN: 0016-7649
Allen PA, Armitage JJ, Whittaker AC, et al., 2015, Fragmentation Model of the Grain Size Mix of Sediment Supplied to Basins, JOURNAL OF GEOLOGY, Vol: 123, Pages: 405-427, ISSN: 0022-1376
Allen PA, Eriksson PG, Alkmim FF, et al., 2015, Classification of basins, with special reference to Proterozoic examples, Geological Society Memoir, Vol: 43, Pages: 5-28, ISSN: 0435-4052
© 2015 The Geological Society of London. Basin classification rests on a plate tectonic foundation, highlighting lithospheric substrate, proximity to plate margin and relative motion of the nearest plate boundary. Major mechanisms for regional subsidence and uplift are subdivided into isostatic, flexural and dynamic groups. Basin-forming mechanisms and basin types do not exhibit simple cause-and-effect relationships, but rather reflect a matrix-type relationship. Different basin types have different spans of existence, with generally shorter life spans related to more tectonically active settings. Many 'polyhistory' basins, composed of two or more megasequences, reflect a long evolution dominated by different basin-forming and basin-modifying mechanisms. The supercontinent cycle is marked by distinct sets of basin types, developed during successive phases of the cycle. Major classification schemes are reviewed briefly, before surveying the range of basin types represented in the Proterozoic of several key cratonic areas. Basins examined encompass almost the entire Neoarchaean-Neoproterozoic period. All of these basins have a relatively long history of preservation, which can be tied to the essentially continental character of their basement rocks and concomitant enhanced 'survivability'. Their preservation thus underlines the longevity and inherent stability of the continental lithosphere. The distinction between basin occurrence over geological time and preferential preservation is important when viewing the geological record.
Armitage JJ, Allen PA, Burgess PM, et al., 2015, SEDIMENT TRANSPORT MODEL FOR THE EOCENE ESCANILLA SEDIMENT-ROUTING SYSTEM: IMPLICATIONS FOR THE UNIQUENESS OF SEQUENCE STRATIGRAPHIC ARCHITECTURES, JOURNAL OF SEDIMENTARY RESEARCH, Vol: 85, Pages: 1510-1524, ISSN: 1527-1404
Thomas RJ, Ellison RA, Goodenough KM, et al., 2015, Salt domes of the UAE and Oman: Probing eastern Arabia, PRECAMBRIAN RESEARCH, Vol: 256, Pages: 1-16, ISSN: 0301-9268
Hampson GJ, Duller RA, Petter AL, et al., 2014, MASS-BALANCE CONSTRAINTS ON STRATIGRAPHIC INTERPRETATION OF LINKED ALLUVIAL-COASTAL-SHELFAL DEPOSITS FROM SOURCE TO SINK: EXAMPLE FROM CRETACEOUS WESTERN INTERIOR BASIN, UTAH AND COLORADO, U.S.A., JOURNAL OF SEDIMENTARY RESEARCH, Vol: 84, Pages: 935-960, ISSN: 1527-1404
Michael NA, Carter A, Whitaker AC, et al., 2014, Erosion rates in the source region of an ancient sediment routing system: comparison of depositional volumes with thermochronometric estimates, JOURNAL OF THE GEOLOGICAL SOCIETY, Vol: 171, Pages: 401-412, ISSN: 0016-7649
Michael NA, Whittaker AC, Carter A, et al., 2014, Volumetric budget and grain-size fractionation of a geological sediment routing system: Eocene Escanilla Formation, south-central Pyrenees, GEOLOGICAL SOCIETY OF AMERICA BULLETIN, Vol: 126, Pages: 585-599, ISSN: 0016-7606
Allen PA, Allen JR, 2013, Basin Analysis: Principles and Application to Petroleum Play Assessment, Chichester, Publisher: Wiley-Blackwell
Allen PA, Armitage JJ, Carter A, et al., 2013, The Qs problem: Sediment volumetric balance of proximal foreland basin systems, SEDIMENTOLOGY, Vol: 60, Pages: 102-130, ISSN: 0037-0746
Armitage JJ, Duller RA, Dunkley-Jones T, et al., 2013, Temporal buffering of climate-driven sediment flux cycles by transient catchment response, Earth and Planetary Science Letters
Armitage JJ, Dunkley Jones T, Duller RA, et al., 2013, Temporal buffering of climate-driven sediment flux cycles by transient catchment response, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 369, Pages: 200-210, ISSN: 0012-821X
Armitage JJ, Jaupart C, Fourel L, et al., 2013, The instability of continental passive margins and its effect on continental topography and heat flow, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 118, Pages: 1817-1836, ISSN: 2169-9313
Michael NA, Whittaker AC, Allen PA, 2013, The Functioning of Sediment Routing Systems Using a Mass Balance Approach: Example from the Eocene of the Southern Pyrenees, JOURNAL OF GEOLOGY, Vol: 121, Pages: 581-606, ISSN: 0022-1376
Allen PA, Armitage JJ, 2012, Cratonic Basins, Tectonics of Sedimentary Basins: Recent Advances, Pages: 602-620, ISBN: 9781405194655
Cratonic basins are sites of prolonged, broadly distributed but slow subsidence of the continental lithosphere, and are commonly filled with shallow water and terrestrial sedimentary rocks. They remain poorly understood geodynamically. A number of models have been proposed that fall into families involving cooling of stretched continental lithosphere, cooling related to mantle flow (dynamic topography), densification of the underlying lithosphere due to phase changes, the surface response to magmatism and/or plume activity, and long-wavelength buckling under in-plane stresses. The timing of initiation and spatial distribution of cratonic basin formation are linked to geodynamic phases within the overall framework of plate amalgamation and sup ercontinental break-up and dispersal. Many cratonic basins initiated in the Neoproterozoic and Cambrian-Ordovician. Some suites of cratonic basins originated as broad ramp-like realms of subsidence tilting down to the adjacent passive margin, and were later "individualized" by secondary processes such as, for instance, reactivation of tectonic structures during intracontinental orogeny, and the emergence of intervening arches and domes. Several different mechanisms may therefore control the geological evolution and subsidence history of cratonic basins during their long life-times. We propose that a model of low strain rate extension accompanied and followed by cooling of the underlying lithosphere satisfactorily explains the long-term subsidence history of a range of cratonic basins. However, the precise role played by dynamic topography transmitted from large-scale mantle flow in initiating or modifying the elevation history of continental interiors remains an intriguing focus for further research. © 2012 Blackwell Publishing Ltd.
Allen PA, Heller PL, 2012, Dispersal and Preservation of Tectonically Generated Alluvial Gravels in Sedimentary Basins, Tectonics of Sedimentary Basins: Recent Advances, Pages: 111-130, ISBN: 9781405194655
The dispersal of coarse gravel from source regions into sedimentary basins is commonly viewed as a hallmark of tectonic activity. Criteria for recognition of syn-tectonic conglomerates include characteristic architectural patterns, progradation of the gravel front, and the rate of down-system fining. However, interpretations of tec tonic timing from such deposits need to consider the dynamic framework of the sediment routing system transporting the sediment from source to sink. The time scales of processes associated with gravel production and transport can be significant and, as a result, dilute the fidelity of the rock record as a recorder of tectonic activity. Signals of coarse-grained sediment release are transformed during propagation through the sediment routing system. One of the most important methods of transforming a sediment release signal is by the buffering effect of local storage in alluvial river systems. The long-term stratigraphic impact of the release of gravel into sedimentary basins is also influenced by the relation between the frequency of the signal released from the source and the response time of the receiving basin. Few studies have evaluated the time lags of gravel deposition across basins. Results from a foreland basin setting in Spain suggest that lag times of 105 to 106 years take place, increasing with down-system distance from the source of gravel. Erosional and depositional landscapes perturbed by tectonics, such as the change of slip rate on a major border fault resulting from segment linkage, undergo a transient response the duration of which depends on climatic parameters, rock erodibility, and system size, but is commonly of order 106 years. Numerical models and field studies suggest that an important part of the variability in stratigraphic successions results from this transient behavior before the establishment of new steady-state conditions. The gravel supplied to sedimentary basins is dispersed down-system, but is also selec
Duller RA, Whittaker AC, Swinehart JB, et al., 2012, Abrupt landscape change post-6 Ma on the central Great Plains, USA, GEOLOGY, Vol: 40, Pages: 871-874, ISSN: 0091-7613
Parsons AJ, Michael NA, Whittaker AC, et al., 2012, Grain-size trends reveal the late orogenic tectonic and erosional history of the south-central Pyrenees, Spain, JOURNAL OF THE GEOLOGICAL SOCIETY, Vol: 169, Pages: 111-114, ISSN: 0016-7649
Allen PA, 2011, GEODYNAMICS Surface impact of mantle processes, NATURE GEOSCIENCE, Vol: 4, Pages: 498-499, ISSN: 1752-0894
Allen PA, Leather J, Brasier MD, et al., 2011, The Abu Mahara Group (Ghubrah and Fiq formations), Jabal Akhdar, Oman, Pages: 251-262
The Abu Mahara Group (c. 725- < 645 Ma) of the Huqf Supergroup in the Jabal Akhdar of northern Oman hosts two glacial successions in the Ghubrah and Fiq formations, separated by the < 50-m-thick volcanogenic Saqlah Member. The > 400-m-thick Ghubrah Formation is dominated by distal glaciogenic rainout diamictites, laminites and turbiditic siltstones, whereas the < 1.5-km-thick Fiq Formation exhibits a cyclical stratigraphy of proximal and distal marine glaciogenic facies, and non-glacial sediment gravity flow and shallow marine facies. The Fiq Formation is overlain by a transgressive, isotopically light carbonate known as the Hadash Formation. A tuffaceous ash interbedded with glacial diamictites of the Ghubrah Formation in Wadi Mistal has yielded a U-Pb zircon age of 713.7±0.5 Ma. The Fiq Formation contains detrital zircons as young as 645 Ma. The use of the CIA (Chemical Index of Alteration) shows the Fiq Formation to be climatically cyclic, with alternations of high and low chemical weathering of contemporary land surfaces driven by phases of glaciation and deglaciation. The transgression into the post-glacial Masirah Bay Formation is marked by a major increase in chemical weathering. © The Geological Society of London 2011.
Allen PA, Rieu R, Etienne JL, et al., 2011, The Ayn Formation of the Mirbat Group, Dhofar, Oman, Pages: 239-249
Glacial deposits are found in the Ayn Formation and Shareef Formation of the Mirbat Group close to Mirbat in Dhofar, southern Oman. The Mirbat Group is most likely a correlative of the Abu Mahara Group of the Huqf Supergroup of northern Oman. The Ayn Formation, the main subject of this chapter, comprises < 400 m of mainly coarse-grained glaciogenic deposits, ponded in 2- to > 8-km-wide N- to NW-oriented palaeovalleys eroded into crystalline basement, with few or no deposits preserved on intervening palaeohighs. The Shareef Formation occurs as thin, lenticular, erosional remnants beneath the unconformably overlying Cret aceous. The Ayn Formation is overlain by a thin ( < 3 m), discontinuous cap carbonate that passes from carbonate-cemented talus on the basin margin to stromatolitic carbonate on palaeohighs and resedimented gravity flows on palaeovalley flanks. © The Geological Society of London 2011.
Armitage JJ, Duller RA, Whittaker AC, et al., 2011, Transformation of tectonic and climatic signals from source to sedimentary archive, NATURE GEOSCIENCE, Vol: 4, Pages: 231-235, ISSN: 1752-0894
Etienne JL, Allen PA, Guerroué EL, et al., 2011, The blaini formation of the lesser Himalaya, NW India, Pages: 347-355
Neoproterozoic glaciogenic deposits crop out widely across the Lesser Himalaya fold and thrust belt in NW India. Underlain by the siliciclastic Simla and Jaunsar Groups, the Blaini Formation (Fm.) includes at least two thick and regionally extensive diamictite units, separated by siliciclastics and argillites and capped by a pink microcrystalline dolomite. A glaciogenic origin is supported by the presence of relatively abundant striated clasts and the local preservation of polished and striated pavement on underlying Simla Group clastics. The cap dolostone is isotopically light with respect to both 13 C and 18 O, which show strong covariance. The Blaini is ubiquitously deformed, incorporated in regional-scale folds and thrusts, and exhibits locally intensive intra-formational deformation. Until recently, geochronological constraints have remained poor, but new detrital zircon ages from diamictite samples provide a maximum age limit of 692±18 Ma ( 207 Pb/ 206 Pb). Reliable palaeomagnetic data are required to constrain the position of this important passive continental margin in palaeogeographical reconstructions. © The Geological Society of London 2011.
Whitchurch AL, Carter A, Sinclair HD, et al., 2011, SEDIMENT ROUTING SYSTEM EVOLUTION WITHIN A DIACHRONOUSLY UPLIFTING OROGEN: INSIGHTS FROM DETRITAL ZIRCON THERMOCHRONOLOGICAL ANALYSES FROM THE SOUTH-CENTRAL PYRENEES, AMERICAN JOURNAL OF SCIENCE, Vol: 311, Pages: 442-482, ISSN: 0002-9599
Whittaker AC, Duller RA, Springett J, et al., 2011, Decoding downstream trends in stratigraphic grain size as a function of tectonic subsidence and sediment supply, GEOLOGICAL SOCIETY OF AMERICA BULLETIN, Vol: 123, Pages: 1363-1382, ISSN: 0016-7606
Whittaker AC, Duller RA, Springett J, et al., 2011, Decoding downstream trends in stratigraphic grain size as a function of tectonic subsidence and sediment supply, Bulletin of the Geological Society of America, Vol: 123, Pages: 1363-1382, ISSN: 0016-7606
Downstream grain-size fi ning in stratigraphy is driven primarily by selective deposition of sediment, and the long-term effi ciency of this process is determined by: (1) the magnitude and characteristics of the input sediment supply; (2) the spatial distribution of subsidence rate, which creates accommodation for sediment preservation; and (3) the dynamics of sediment transport and deposition. A key challenge is to determine how these fi rst two factors control the caliber and spatial distribution of deposits over time scales of 10 4 -10 6 yr without incorporating sediment transport details that are largely unknowable for time-averaged stratigraphy in the geological past. We address this using grain-size data collected from fl uvial conglomerates in the Eocene Pobla Basin, Spanish Pyrenees, a synorogenic basin where the timing of sediment deposition is well-constrained; the sediment budget is closed; and good exposure enables time lines within stratigraphy to be picked out unambiguously. For successive stratigraphic horizons, downstream trends in grain size and composition are derived for basin-fi lling sediment-routing systems with length scales of 6 and 40 km, respectively. Our data show that the rate of grain-size fi ning varies over time and with system length and can be linked to changes in source area. These results are contrasted with grain-size data from the Antist Group, a 60-km-long Oligocene system that mantles the Southern Pyrenees, where very slow rates of grainsize fi ning on the wedge top of this foldand-thrust belt are observed. We apply aself-similarity-based selective deposition model to quantify the competing controls of tectonic subsidence and sediment supply on derived grain-size trends, and model results are compared with independent constraints on the Eocene-Oligocene evolution of the Pyrenees. Our results suggest that it is now possible to invert time-averaged grain-size trends in stratigraphy to gain quantitative information on the geologi
Armitage JJ, Allen PA, 2010, Cratonic basins and the long-term subsidence history of continental interiors, JOURNAL OF THE GEOLOGICAL SOCIETY, Vol: 167, Pages: 61-70, ISSN: 0016-7649
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