V. Paul Wright

National Museum Wales, Cardiff, Wales, United Kingdom

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Publications (46)90.97 Total impact

  • V. Paul Wright · Lesley Cherns

    No preview · Article · Dec 2015 · Journal of the Geological Society
  • A. J. Barnett · V. P. Wright · V. S. Chandra · V. Jain

    No preview · Article · Dec 2015 · Geological Society London Special Publications
  • V. P. Wright · A. J. Barnett
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    ABSTRACT: The cyclic distribution of various types of carbonates and Mg-clays in early Cretaceous rift-sag phase lacustrine carbonates from the subsurface of the South Atlantic provides an insight into how evolving lake chemistries in highly alkaline settings control facies development. The typically subdecametre scale symmetrical and asymmetrical cyclothems exhibit three main components: mud-grade laminated carbonates, millimetre-diameter spherulites with evidence of having been in a matrix of Mg-silicates, and millimetre-centimetre calcitic shrub-like growths. The laminites contain conspicuous numbers of ostracods and vertebrate remains and were produced by short-lived pluvial events, causing expansion of shallow lakes. Later evaporation triggered Mg-silicate precipitation and calcite nucleation within gels to produce spherulitic textures. When the rate of gel precipitation decreased or ceased, calcite growth, now less inhibited, produced shrub-like calcites resembling those produced abiotically in modern travertines, although still with some evidence of the former presence of some Mg-silicates. Physical reworking of these sediments led to the dispersion of the gels and the concentration of detrital carbonate components. Despite earlier proposals, evidence of microbial processes producing carbonates in these Cretaceous lake deposits is rare and the application of facies models based on modern and ancient microbialite analogues maybe be misplaced.
    No preview · Article · Jul 2015 · Geological Society London Special Publications
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    ABSTRACT: The unusual occurrence of calcretes and prominent organic matter in the Middle Jurassic (Lower Bathonian, Serra de Aire Formation) of the Lusitanian Basin of western Portugal (Western Iberian Margin) revealed a complex palimpsest exposure record, here interpreted as reflecting hydrological changes caused by phases of emergence and immersion. It serves as a potential model for understanding strtigraphic development at lowstand surfaces in ther carbonate successions. The exposure-dominated facies association grades upwards into peritidal and lagoonal limestones, and the interval is assigned to the regressive peak of a Transgressive-Regressive Facies Cycle (2nd order) of the thick Middle Jurassic carbonate ramp succession.
    No preview · Article · May 2015 · Sedimentary Geology
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    ABSTRACT: Platform margins have been targets for carbonate exploration because they are commonly seismically resolvable and reservoir prone for several critical reasons including karstic porosity. Platform margin karst models, mainly based on the Quaternary of the Caribbean (tropical humid, including "flank margin caves") are well documented, but analogs remain rarely identified in the stratigraphic record. Analysis of a remarkably well-exposed macroporosity paleokarst system from the Paleocene of north Spain, formed under an arid to semiarid climate, provided a model that differs from the Caribbean template. Implications for exploration and appraisal strategies, include provisos regarding (1) how early fracture intensity can be estimated at platform margins, (2) the absence of flank margin caves at the margin, (3) the absence of karstic features at or immediately below the main lowstand surface, (4) the presence of cave-free corridors such that the porosity zones could be missed completely, and (5) the stratigraphic inheritance of caves into successive levels adjacent to the cave-free zones. Quantitative data were evaluated on the main macroporous intervals. We also compared this model with other paleokarst models in the literature to emphasize the diversity of approaches that can be used to evaluate paleokarst targets: "one size does not fit all."
    No preview · Article · Jun 2014
  • D. A. Pollitt · P. M. Burgess · V. P. Wright
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    ABSTRACT: Hierarchies of cyclicity have been described from a wide variety of carbonate platform strata and are assumed to be a consequence of Milankovitch-forced variations in accommodation, although descriptions of hierarchical strata, including 'cycles' and what they constitute, are typically qualitative, subjective, and in some cases difficult to reproduce. One reason for this is the lack of any detailed definition of what constitutes a hierarchy, as well as the implicit and largely untested nature of the assumptions underpinning most interpretations of hierarchical strata. In this study we aim to investigate the response of depositional systems if they were to behave in the way implied by sequence stratigraphic (hierarchical) models, to clearly state the assumptions of these models, and illustrate the consequences of these assumptions when they are employed in a simple, internally-consistent forward model with plausible parameters. We define hierarchies, in both the time-domain (chronostratigraphic) and thickness-domain (stratigraphic), as two or more high-frequency sequences (HFSs) in which there exists a repeated trend of decreasing high-frequency sequence thickness such that within a single low-frequency sequence (LFS) each high-frequency sequence is thinner than the previous sequence. Based on this definition, results from 110 000 numerical model runs suggest that ordered forcing via cyclical eustatic sea-level oscillations rarely results in an easily identifiable hierarchy of stacked cycles. Hierarchies measured in the chronostratigraphic time-domain occur in only 9% of model run cases, and in 15% of cases when measured in the thickness-domain, suggesting that vertical thickness trends are probably not a useful way to identify products of ordered periodic external forcing. Variability in relative forcing periodicity results in significant variation in both HFS and LFS thickness trends making accurate identification of hierarchy and any forcing controls from thickness data alone very difficult. Comparison between model results and outcrop sections suggests that hierarchies are often assumed to be present despite a lack of adequate supporting evidence and quantitative analysis of these sections suggests that they are not hierarchical in any meaningful sense.
    No preview · Article · Apr 2014 · Geological Society London Special Publications
  • A.J. Barnett · V.P. Wright · S.F. Crowley
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    ABSTRACT: Orange to tan weathering ferroan dolomites associated with palaeosols are a volumetrically minor but conspicuous feature of cyclic late Mississippian (Brigantian) icehouse ramp successions in Kentucky, eastern USA. The ferroan dolomites have sharp bases and tops and are intercalated with pedogenic units (e.g. calcretes) or floodplain deposits. Sedimentological and C/O stable isotope data suggest that the dolomiteswere formed in brackish or schizohaline coastal marsh (paludal) environments. This chapter establishes the origin of these ferroan dolomite beds, documents their sequence stratigraphic significance, and draws attention to a potentially wide-spread but rarely documented sub-aerial exposure feature. Paludal dolomite beds associated with well-developed palaeosols and major (Myr-scale) disconformities probably reflect depressed Milankovitch band sea-level oscillations that occurred during third-order lowstands.
    No preview · Chapter · May 2013
  • L. Cherns · V. P. Wright
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    ABSTRACT: It is now well established that seawater chemistry, as well as influencing non-skeletal marine precipitation ('calcite' and 'aragonite seas'), has affected skeletal mineral secretion in some algal and marine invertebrate groups. Skeletal mineralogy has had a yet more profound consequence on fossil preservation. The realization that the fossil record of marine organisms with an aragonite shell is widely depleted in some shelf settings through early, effectively syn-depositional, dissolution ('missing molluscs' effect) has led to a re-evaluation of the composition, diversity, ecological and trophic structure of marine benthic communities. Comparisons of molluscan lagerstätten from 'calcite' and 'aragonite seas' show a similar pattern of skeletal mineralogical loss, that is, no differences are discernibly linked to changed seawater geochemistry. It is notable that the rare mollusc-rich skeletal lagerstätten faunas in the fossil record include many small individuals. Micromolluscs are quantitatively important among modern shell assemblages, yet small size is a major source of taphonomic and biodiversity loss in the fossil record. In skeletal lagerstätten faunas, micromolluscs contribute variably to mollusc biodiversity but appear particularly significant through at least to Triassic times. They highlight a further 'missing molluscs' effect of taphonomic loss through early dissolution.
    No preview · Article · Dec 2011 · Geological Society London Special Publications
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    ABSTRACT: Current classifications of carbonate platforms use depositional gradient as the main criterion for separating systems into two end-member types, ramps and flat-topped platforms (FTPs). However, many examples do not conform to this simple classification. To investigate why this is and to better understand probable controls on platform development, we have used a series of 2D numerical forward model runs to investigate how sediment production, diffusional sediment transport, and other controls such as tectonic subsidence, antecedent topography, and relative sea-level oscillation interact to determine platform geometry. Modeling results reaffirm that rates of down-dip sediment transport relative to rates of autochthonous production are a critical factor in maintaining a ramp profile in stable cratonic settings under a constant rate of relative sea-level rise. Type of carbonate production versus water-depth curve, for example euphotic versus oligophotic, is not a significant control in our model cases. Both euphotic and oligophotic production profiles produce FTPs when diffusion coefficients are low relative to production rates, and ramps when diffusion coefficients are relatively high. These results suggest a continuum of platform types, ranging from transport-dominated, low-gradient systems at one end of the spectrum, to in situ accumulation dominated systems at the other. A system may be transport-dominated because high-energy processes are able to break down and transport even bound sediment, or because carbonate factories produce only sediment that is easily transportable under even low-energy conditions. Time evolution is also probably important. Initially low gradient systems will, in the absence of sufficiently high sediment transport rates, tend to evolve towards high-gradient flat-topped steep-margined platforms. Many observed or inferred platform geometries are therefore likely to be transient forms, and this could complicate interpretation. Investigating how basin bathymetry and style of subsidence control platform geometry suggests that, in transport-dominated systems, strata simply drape the underlying topography, and that pre-existing breaks of slope and differential fault subsidence are a stronger control on platform geometry in in situ accumulation dominated systems. Rotational subsidence tends to create transport-dominated systems during rotation as the topographic gradient increases and transport rate increases and outpaces in situ production rate. Relative sea-level oscillations tend to move the locus of sediment production laterally along any slope present on the platform, distributing the sediment accumulation across the whole width of the platform, suppressing progradation and steepening, and so favoring development of low-gradient systems. Based on all these results, we suggest that a simple cutoff classification into ramp and flat-topped platform types can still be useful in some circumstances, but a more meaningful approach may be to describe and predict platform strata in terms of a multiple-dimension platform parameter space containing a continuum of geometries controlled by sediment production, sediment diffusion coefficient, antecedent topography, differential subsidence effects, relative sea-level oscillations and perhaps other as yet unappreciated controls.
    Full-text · Article · Jan 2011 · Journal of Sedimentary Research
  • Lesley Cherns · James R. Wheeley · V. Paul Wright
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    ABSTRACT: Early diagenetic dissolution of skeletal carbonate in environments from seafloor to shallow burial has the potential to skew the marine fossil record of aragonitic shells, particularly molluscs. Taphonomic windows leading to the preservation of labile skeletal components include relatively rare occurrences of early mineral replacement by silica (skeletal lagerstätten). Another, much more frequent process is event deposition where dissolution is halted by rapid burial of shells. Shell plasters form in basinal mud or low energy lagoonal environments during temporary dysoxic episodes, such as are caused by algal blooms. Preservation potential for aragonitic fossils may be enhanced by early cementation during shallow burial (hardgrounds) that protects the delicate dissolution moulds from destruction by bioturbation, or in high energy shoal environments where the drive for microbial dissolution is reduced. A data-based environmental model summarizes the main taphonomic zones, and illustrates significant taphonomic bias against aragonitic shells in lower energy settings of platform interiors and mid-outer ramps/shelves. The temporal distribution of various taphonomic windows shows the limited occurrence of silicified faunas, while the nature and extent of shell beds also change, but there is no obvious correlation with periods of ‘calcite’ and ‘aragonite seas’.
    No preview · Chapter · Nov 2010
  • Lesley Cherns · V. Paul Wright
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    ABSTRACT: Quantitative analysis of rare skeletal Lagerstatten of Paleozoic-early Mesozoic ages indicates that early dissolution of aragonite has seriously skewed community structures. The consequences of this widespread diagenetic process effectively preclude accurate interpretation and reconstruction of many fossil faunas in shelf settings. Trophic and ecologic loss focuses on the shallow infaunal tier of burrowing bivalves and the epifaunal vagrant detritus-feeding tier represented by gastropods. Case studies of the Ordovician-Carboniferous suggest that sequences with apparently typical Sepkoski Paleozoic faunas dominated by brachiopods were originally molluscan-dominated and included significant infaunal components. Early Mesozoic faunas dominated by epifaunal and semi-infaunal bivalves are similarly severely skewed by loss of ecologic diversity. Molluscan biodiversity appears more strongly affected in Paleozoic times. Such lower-energy environments as lagoons and mid-to-outer carbonate ramp settings are especially prone to dissolution loss. It is perhaps important to question for such faunas whether trophic tiers are reduced or missing.
    No preview · Article · Oct 2009 · Palaios
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    ABSTRACT: As much as 80% of the 4.5-km-thick succession of alluvial sediments of late Silurian to early Devonian age in South Wales is composed of mudstone, generally regarded as overbank suspension deposits. Studies of selected formations reveal a variety of lithofacies associations in these mud-dominated intervals, which suggest diverse mechanisms for mud emplacement. For example, there are distinct fining upward units, 2.5–5 m thick, that represent ephemeral channel-zone deposits in which extensive reworking of palaeo-Vertisols took place as clay pellet bedload material. The overall depositional system has many similarities with that described from the Channel Country of central Australia, where anastomosing fluvial systems are associated with distal mud sheetflood deposits. The exact channel planforms for the Old Red Sandstone systems, however, cannot be readily determined, although where larger channel sandbodies exist they have a sheet-like occurrence with a high width/depth ratio, and possibly may be the result of large-scale, low-frequency sheet-flood events. The development of palaeosols with vertic features, calcretes, alternations of desiccation and burrowing in the channel deposits suggests marked seasonality with a flashy regime. The Channel Country represents a fairly stable low-relief cratonic interior, whereas the Old Red Sandstone in South Wales was deposited on a coastal-plain in a subsiding basin setting. There are, however, similarities in terms of depositional products despite the disparity in morpho-tectonic setting, which may reflect extremely low gradients and climatic influences such as frequency and magnitude of flood events.
    No preview · Chapter · Mar 2009
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    Lesley Cherns · James R. Wheeley · V. Paul Wright
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    ABSTRACT: Recent studies on silicified fossil biotas have suggested that substantial skewing of the molluscan record resulted from early aragonite dissolution in mid-outer carbonate ramp settings. If those rare skeletal lagerstätten are representative, then the quality and completeness of the molluscan record are thrown into doubt. Yet database studies suggest that the bivalve fossil record is actually relatively complete. If so, then biodiversity must be captured by other processes that preserved shells vulnerable to early dissolution, and which operated on a relatively high frequency, i.e., less than the species duration for bivalves.Storm beds, shell plasters and submarine hardgrounds are identified as fossil deposits that can preserve the labile aragonitic component of the fauna and thus represent potential taphonomic windows. Many storm event beds include rich accumulations of shelly benthos. Differences between storm bed faunas and those of the background facies could reflect transportation effects. However, some storm bed assemblages are rich in originally aragonitic infaunal bivalves that are not represented in background facies or more proximal shelf equivalents, and here rapid burial and removal of organic matter by winnowing may be the keys to aragonite shell preservation. Despite Palaeozoic to Cenozoic changes in the thickness and frequency of shell beds that reflect the predominant bioclast producers, shallow infaunas are commonly concentrated together with epifauna in such deposits.Some low energy, organic-rich mud-dominated settings are associated with preservation of aragonitic molluscs. Infaunal bivalves are a prominent component of shell plasters or pavements in such settings, linked to episodic bottom water anoxia. Decaying algal blooms drew the redox boundary up above the sediment–water interface, and brought populations of infaunal bivalves to the surface where they died. Isolated from the oxic taphonomically active zone, the shells were not dissolved and were buried as thin shell layers. In similar settings, aragonitic shells were preserved as moulds through early pyritisation, or even through preservation of original shell aragonite.In oxic environments, bioturbational reworking of surface sediment destroyed moulds of aragonitic shells after early dissolution. In some hardgrounds, these delicate moulds were preserved due to synsedimentary cementation, probably using carbonate released by aragonite dissolution. The examples included here come from both intervals of “calcite” and “aragonite” seas, and it is not possible to assess whether the saturation state (with respect to aragonite) of the ambient sea water played a role in the selective removal of aragonitic shells.While taphonomic windows may have captured the diversity of individual groups, it is clear from quantitative data involving skeletal lagerstätten that the scale of loss from early aragonite dissolution has drastically altered the trophic composition of some fossil assemblages commonly used as the basis for reconstructions of past communities.
    Full-text · Article · Dec 2008 · Palaeogeography Palaeoclimatology Palaeoecology
  • P. M. Burgess · V. P. Wright · D. Emery
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    ABSTRACT: The mechanisms responsible for formation of peritidal parasequences have been a focus of debate between proponents of contrasting autocyclic and allocyclic models. To contribute to this debate a three-dimensional numerical forward model of carbonate production, transport and deposition has been developed. Shallowing-upward parasequences are produced in the model via carbonate island formation and progradation, with an element of self-organization, and no external forcing. These autocyclic parasequences have characteristics comparable with peritidal parasequences observed in outcrop. Modelled parasequence thickness and duration depend primarily on subsidence rate and sediment transport rate, illustrating the significance of sediment flux in formation of peritidal parasequences. Adding an element of stochastic variation of sediment transport rate and transport path leads to formation of nonuniform-thickness parasequences that generate Fischer plots showing apparent hierarchies similar to those often interpreted as evidence of eustatic forcing. The model results do not rule out allocylic mechanisms, but suggest that shoreline and island progradation are also plausible mechanisms to create variable-thickness, shallowing-upward peritidal parasequences and should be considered in interpretations of such strata.
    No preview · Article · Oct 2008 · Basin Research
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    ABSTRACT: Study of four closely-spaced El Garia Formation reservoirs (offshore Tunisia) has identified diagenetic controls on variation in reservoir quality. The Ashtart, Didon and Zarat Fields have been affected by significant dissolution porosity, which occurred during burial diagenesis, with vuggy pores preferentially forming in micritic sediment. However, inter-crystalline porosity due to dolomitisation is the principal control on reservoir quality in the Hasdrubal Field. This spatial variation in porosity type reflects, to some extent, the structural and sedimentological isolation of Hasdrubal within the facies trend, surrounded by deep water embayments and, unlike the other studied fields, not directly underlain by salt diapirs.
    No preview · Article · Sep 2008 · Sedimentary Geology
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    ABSTRACT: The Mississippian - Pennsylvanian Global Stratotype Section and Point (GSSP) are hosted within a shallow-water, dominantly carbonate succession in the lower part of the Bird Spring Formation at Arrow Canyon, Nevada, USA. The boundary is marked by the first appearance datum (FAD) of the conodont Declinognathodus noduliferus sensu lato. It is shown that the boundary interval is punctuated by numerous subaerial hiatuses represented by palaeokarstic surfaces and palaeosols, which divide strata at this location into fourth-order glacio-eustatic cycles. A well-developed palaeosol horizon occurs <1 m above the FAD of D. noduliferus. It also coincides with a very marked facies change and a second-order shift in cycle-stacking patterns. These characteristics violate International Commission on Stratigraphy guidelines, which state that GSSPs should be chosen in sections showing continuous sedimentation and lacking vertical facies changes at or near the boundary. Because the Mid-Carboniferous is an icehouse interval, cyclostratigraphy is a powerful tool for high-resolution correlation. A comparison of the cyclostratigraphy of Mid-Carboniferous strata at Arrow Canyon and in northern England indicates that a large number of glacio-eustatic sea-level oscillations are not recorded at Arrow Canyon and that this section contains over 25 missed beats of Milankovitch band duration equating to a hiatus of ≥1 Ma.
    No preview · Article · Jul 2008 · Journal of the Geological Society
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    James R. Wheeley · Lesley Cherns · V. Paul Wright
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    ABSTRACT: Aragonite derived from marine molluscs is evaluated as the source for microcrystalline carbonate cements of limestone-mar] alternations (LMA). Calculations demonstrate that extremely low levels of mollusc-derived aragonite, well below the production rates of molluscs in modem marine settings, could have provided sufficient carbonate to cement examples of Ordovician, Silurian and Jurassic LMA in non-tropical or tropical settings. It is likely that even in the Palaeozoic molluscs provided sufficient carbonate entirely to source microcrystalline cements of LMA. Autochthonous molluscan aragonite is the only viable aragonite precursor for LMA microcrystalline cements of cool-water settings where temperatures precluded calcified algae and abiotic carbonate precipitation. In 'calcite seas' where Mg:Ca ratios inhibited both abiogenic aragonite precipitation and aragonite generation by calcified algae, molluscan aragonite was again the most likely main contributor. In some epeiric seas where brackish wedges switched off the shallow-water carbonate mud factories molluscan aragonite is the parsimonious source of carbonate for LMA microcrystalline cements.
    Full-text · Article · Jan 2008 · Journal of the Geological Society

    No preview · Article · Jan 2008
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    ABSTRACT: The Early Devonian Conigar Pit Sandstone Member (CPSM) of the Freshwater West Formation (Lower Old Red Sandstone, Lochkovian age) at Freshwater West in south Wales comprises a heterolithic, predominantly alluvial suite (mudstones, fine to coarse-grained sandstones, conglomerates) with varying depositional architecture. A number of discrete facies associations are observed. The fine-grained, inclined- and non-inclined heterolithic association is dominant within the CPSM. It represents dryland sinuous channelized flow (IHS bedsets) and unconfined flow (non-inclined bedsets) at terminal and intermediate floodouts deposited under semi-arid conditions. Mudstones were deposited in two distinct environments associated with this semi-arid river system. Laminated and burrowed, reddish brown mudstones were deposited in shallow semi-permanent lakes or pools on the floodplain. Massive mudstones were deposited as within-channel muddy braid-bars, with sedimentary structures being lost during subsequent compaction. The mudstones exhibit Vertisol pedogenesis reflecting the seasonal wetting and drying associated with the semi-arid climate. Periods of intense desiccation are indicated by deep desiccation cracks and associated rubbly surfaces. Possible, though unproven tidal conditions influenced a small percentage of the heterolithic channels at Freshwater West. The extent of these channels is uncertain. The coarser-grained multi-storey sandstone association was deposited by low-sinuosity rivers with a fluctuating, but perennial discharge. Associated with these laterally extensive sandbodies was a high water table with surface ponding (wetlands) that enabled the preservation of plant detritus. During high discharge events, flow expanded over the contemporaneous floodplain depositing the sheet sandstone association within splay complexes. The interpretation that perennial discharge may have been triggered by basin-wide climate change challenges the long-held view that the Lower ORS climate was continuously semi-arid in nature. The spatial/temporal extent of this climate change is uncertain, as it is possible that the multi-storey sandbodies were deposited by allogenic rivers draining a distant, possibly uplifted source area. A decrease in the observed frequency and maturity of Vertisol profiles, and a corresponding increase in multi-storey sandbodies upward through the succession may reflect a long-term, episodic pattern of climate change.
    No preview · Article · Nov 2007 · Sedimentary Geology
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    ABSTRACT: An extensive palaeokarst porosity system, developed during a pronounced mid-Paleocene third-order lowstand of sea level, is hosted in Danian limestones of the Urbasa–Andia plateau in north Spain. These limestones were deposited on a 40–50 km wide rimmed shelf with a margin characterised by coralgal buildups and coarse-grained bioclastic accumulations. The sea-level fall that caused karstification was of approximately 80–90 m magnitude and 2.5 Ma in duration. During the exposure, a 450 m wide belt of sub-vertical margin-parallel fractures developed a few hundred metres inboard of the shelf edge. Most fractures are 90–100 m deep, average 1 m in width, and are associated with large erosional features created by collapse of the reefal margin. Inland from the fracture belt, three superimposed laterally extensive cave systems were formed over a distance of 3.5 km perpendicular to shelf edge, at depths ranging from 8–31 m below the exposure surface. The palaeocaves range from 0.3 to 2 m in height, average 1.5 m high. They show no evidence of meteoric processes and are filled with Thanetian grainstones rich in reworked Microcodium, a lithology that also occurs infilling the fractures. The caves are interpreted as due to active corrosion at the saline water–fresh-water mixing zone. Caves are missing from the shelf edge zone probably because the fractures beheaded the meteoroic lens preventing mixing-zone cave development beyond the fracture zone. Towards the platform interior, each cave system passes into a prominent horizon, averaging 1 m in thickness, of spongy porosity with crystal silt infills and red Fe-oxide coatings. The spongy horizons can be traced for 5.5 km inboard from the cave zone and occur at 10.5 m, 25 m and 32 m below the exposure surface. In the inland zone, two additional horizons with the same spongy dissolution have been recognised at depths of 50 m and 95 m. All are analogous to Swiss-cheese mixing-zone corrosion in modern carbonate aquifers and probably owe their origins to microbially-mediated dissolution effects associated with a zone of reduced circulation in marine phreatic water. In the most landward sections a number of collapse breccia zones are identified, but their origin is unclear. The palaeokarst system as a whole formed during the pulsed rise that followed the initial sea-level drop, with the three main cave-spongy zones representing three successive sea-level stillstands, recorded by stacked parasequences infilling large erosional scallops along the shelf margin. The geometry of the palaeo-mixing zones indicates a low discharge system, and together with the lack of meteoric karstic features favours a semi-arid to arid climatic regime, which is further supported by extensive calcrete-bearing palaeosols occurring in coeval continental deposits.
    No preview · Article · Jul 2007 · Sedimentary Geology

Publication Stats

1k Citations
90.97 Total Impact Points


  • 2014-2015
    • National Museum Wales
      • Department of Natural Sciences
      Cardiff, Wales, United Kingdom
  • 2001-2011
    • Cardiff University
      • School of Earth and Ocean Sciences
      Cardiff, Wales, United Kingdom
  • 2006-2007
    • Milton Keynes College
      Milton Keynes, England, United Kingdom
    • University of Bristol
      Bristol, England, United Kingdom
  • 2002-2007
    • University of Wales
      Cardiff, Wales, United Kingdom
  • 2003
    • University of South Wales
      Понтиприте, Wales, United Kingdom