The glauconite-phosphate association in hardgrounds: examples from the Cenomanian of Devon, southwest England

Carson, G.A.; Crowley, Stephen F.

doi:10.1006/cres.1993.1006

Cited by 27 publications

(16 citation statements)

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“…Condensation‐related mineralization of major Assoul Formation discontinuities by secondary iron and manganese oxides or phosphates is a common feature (Fig. 12) and similar mineralization features have been described in the literature (Bromley, 1975b; Fürsich, 1979; Carson & Crowley, 1993; Gomez & Fernandez‐Lopez, 1994; Burkhalter, 1995; Hillgärtner, 1998). Several laterally limited surfaces display superficial and spatially rather localized staining by secondary iron and manganese oxides.…”

Section: Characterization and Interpretation Of Discontinuity Surfacessupporting

confidence: 70%

Characterization and interpretation of discontinuity surfaces in a Jurassic ramp setting (High Atlas, Morocco)

Christ¹,

Immenhauser²,

Amour

et al. 2011

Sedimentology

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Discontinuity surfaces are widely recognized but often poorly understood features of epeiric carbonate settings. In sedimentary systems, these features often represent hiatus surfaces below biostratigraphic resolution and may represent a considerable portion of the time contained in the sediment record. From an applied perspective, discontinuities may represent horizontal flow barriers and result in reservoir compartmentalization. Here, a total of 80 condensed surfaces (S1), firmgrounds (S2) and hardgrounds (S3) from a Jurassic (Middle and Upper Bajocian Assoul Formation) ramp setting of the High Atlas in Morocco are carefully documented with respect to their morphology, their secondary impregnation by Fe and Mn oxides and phosphates and their palaeoecological record. A statistical frequency distribution of two surfaces of the S1 type, 1·1 surfaces of the S2 type and 0·4 surfaces of the S3 type per 10 section metres is observed along a 220 m long carbonate succession. Based on two stratigraphically and spatially separated study windows and correlative sections, the stratigraphic frequency distribution, the lateral extent and the nature of facies change across discontinuities are documented in a quantitative manner. Specific features of the study site include the considerable stratigraphic thickness of the Assoul Formation and the conspicuous absence of subaerial‐exposure‐related features. Based on the data presented here, firmground and hardground surfaces are best interpreted as maximum‐regression‐related features. Relative sea‐level lowstand results in a lowered wave base, and wave orbitals and currents result in sea floor omission and lithification. Care must be taken to avoid overly simplistic interpretations, as differences in bathymetry and carbonate facies result in marked changes in discontinuity characteristics in proximal–distal transects. The data shown here are of significance for those concerned with the interpretation of shoal water carbonate environments and are instrumental in the building of more realistic carbonate reservoir flow models.

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Section: Characterization and Interpretation Of Discontinuity Surfacessupporting

confidence: 70%

Characterization and interpretation of discontinuity surfaces in a Jurassic ramp setting (High Atlas, Morocco)

Christ¹,

Immenhauser²,

Amour

et al. 2011

Sedimentology

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“…7,8,10b). This event is not yet widely recognized, but it may correspond to the omission surface at the base of the Bila Hora Formation in the Bohemian Cretaceous Basin (Ulicný et al 1993), the top of the Dölzschen Formation in the Saxonian Cretaceous Basin (Wilmsen et al 2009b), and the top-hardground of the Beer Head Limestone in the condensed Cenomanian successions in Devon, SW England (Carson and Crowley 1993), thus being of inter-regional importance. The name SB Ce 6 is proposed for this sequence boundary (Fig.…”

Section: Sequence Stratigraphymentioning

confidence: 99%

Facies pattern and sea-level dynamics of the early Late Cretaceous transgression: a case study from the lower Danubian Cretaceous Group (Bavaria, southern Germany)

Wilmsen

Niebuhr

Chellouche

et al. 2010

Facies

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The facies development and onlap pattern of the lower Danubian Cretaceous Group (Bavaria, southern Germany) have been evaluated based on detailed logging, subdivision, and correlation of four key sections using an integrated stratigraphic approach as well as litho-, bio-, and microfacies analyses. Contrary to statements in the literature, the transgressive onlap of the Regensburg Formation started in the Regensburg-Kelheim area already in the early Early Cenomanian Mantelliceras mantelli ammonite Zone and not in the Late Cenomanian. In the Early Cenomanian, nearshore glauconitic-bioclastic sandstones prevailed (Saal Member), followed by Middle to lower Upper Cenomanian mid-shelf siliceous carbonates intercalated with fine-sandy to silty marls (Bad Abbach Member). Starting in the midLate Cenomanian (Metoicoceras geslinianum ammonite Zone), a considerable deepening pulse during the Cenomanian-Turonian Boundary Event (CTBE) initiated the deposition of the deeper shelf silty marls of the Eibrunn Formation, which range into the early Early Turonian. During the CTBE transgression, also the proximal Bodenwöhrer Senke (ca. 40 km NE of Regensburg) was flooded, indicated by the onlap of the Regensburg Formation onto Variscan granites of the Bohemian Massif, overlain by a thin tongue of lowermost Turonian Eibrunn Formation. A detailed record of the positive d 13 C excursion of the global Oceanic Anoxic Event (OAE) 2 has been retrieved from this shallow-water setting. An integrated approach of bio-, event-, carbon stable isotope and sequence stratigraphy was applied to correlate the sections and to decipher the dynamics of this overall transgressive depositional system. The Cenomanian successions show five prominent unconformities, which correlate with those being known from basins in Europe and elsewhere, indicating their eustatic origin. The rate of sea-level rise during the CTBE suggests glacio-eustasy as a driving mechanism for Late Cenomanian sea-level changes. The Regensburg and Eibrunn formations of the lower Danubian Cretaceous Group are highly diachronous lithostratigraphic units. Their regional distribution and northeast-directed onlap pattern onto the southwestern margin of the Bohemian Massif can readily be explained by the lateral movements of roughly coast-parallel (i.e., NW/SE-trending) facies belts of a graded shelf system transgressing on a northeastwardrising substrate. It took the Cenomanian coastline ca. 6 Ma to transgress from southwest of Regensburg to the topographically elevated granite cliffs southeast of Roding in the Bodenwöhrer Senke (=60 km distance).

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“…6A), pebbly-sized polymict dropstones ( Fig. 4D) which were transported by ice rafting from west Ireland during the Pleistocene (Scoffin and Bowes 1988), as well as clay minerals and detrital glauconite grains which are typically associated with hardgrounds (Carson and Crowley 1993;Remia et al 2004) occur in the sediments of the Porcupine Bank slope (Connacht Mound) and in the Belgica Mound Province. This terrigenous influx found in the mainland-connected areas contrasts the nearly pure carbonate sediments of the isolated western Rockall Bank (Scoffin et al 1980).…”

Section: Composition Of Sedimentsmentioning

confidence: 99%

From sediment to rock: diagenetic processes of hardground formation in deep-water carbonate mounds of the NE Atlantic

Noé

Titschack

Freiwald

et al. 2006

Facies

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Modern cool-water carbonate mounds topped by corals form an extended reef belt along the NW European continental margin at 200-1200 m water depth. An essential element of mound growth are hardgrounds which provide a stable substratum for mound-building invertebrate colonisation and stabilise the inclined mound flanks. Evaluating the degree of lithification and the slope stability against erosion represents an important task within the ESF programme MOUNDFORCE under the umbrella of EUROMARGINS. Sampling of hardgrounds during RV Meteor cruises M61-1 and -3 in 2004 by means of the IFM-GEOMAR TV-grab and the Bremen ROV QUEST focused on carbonate mounds of the Porcupine Seabight and northwestern Rockall Bank off Ireland. Lithified carbonates of mid-Pleistocene age were exhumed during the Holocene and are now exposed on the top and flanks of numerous carbonate mounds showing a patchy to dense colonisation by living corals and associated invertebrates. The sediments, composed of foraminiferal-nannoplankton oozes and admixed mound-derived invertebrate skeletons, range from partly lithified chalks to dense micritic limestones. These wackestones to packstones clearly differ from bacterially induced authigenic carbonate crusts typical of hydrocarbon seep settings by showing current-induced sedimentary structures, a non-luminescing matrix indicating oxic pore fluids, and a marine isotopic signature lacking any depleted carbon regime which is typical of anaerobic methane oxidation. The carbonate lithification is driven by carbonate ion diffusion from supersaturated seawater into the pore fluids S. Noé ( ) · W.-C. Dullo in the studied areas. Vigorous bottom currents were the ultimate control not only of carbonate cementation by enhancing the diffusion process and supporting a pumping mechanism, but also of hardground formation and mound shaping by exhuming lithified carbonates and preventing finegrained sediment accumulation at the downslope mound flanks.

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The glauconite-phosphate association in hardgrounds: examples from the Cenomanian of Devon, southwest England

Cited by 27 publications

References 0 publications

Characterization and interpretation of discontinuity surfaces in a Jurassic ramp setting (High Atlas, Morocco)

Characterization and interpretation of discontinuity surfaces in a Jurassic ramp setting (High Atlas, Morocco)

Facies pattern and sea-level dynamics of the early Late Cretaceous transgression: a case study from the lower Danubian Cretaceous Group (Bavaria, southern Germany)

From sediment to rock: diagenetic processes of hardground formation in deep-water carbonate mounds of the NE Atlantic

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