Lower Jurassic Carbonate Buildups and Associated Facies, Central and Western Morocco

Park, Robert K.

doi:10.2110/cor.83.01.0328

Cited by 5 publications

(12 citation statements)

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“…Two coral-reef sites from shallow intraplatform and shelf-margin areas of Morocco are listed in the database for the Toarcian-Aalenian time span (cf. Beauvais, 1986;Park, 1983). Detailed stratigraphic study is needed, however, to Biota.-The Early Jurassic reef biotas were dominated by corals and bivalves.…”

Section: Lower Jurassic Reef Pattern (Fig 2) General Distribution Anmentioning

confidence: 99%

“…Moroccan Domain: Morocco, Algeria.-Morocco played a major role in Early Jurassic reef development. Numerous localities with sponge-microbial mud mounds, coral reefs, and/or lithiotid bioherms are recorded from the Middle and High Atlas region (e.g., Beauvais, 1986;Dresnay, 1971Dresnay, , 1977Park, 1983;Crevello and Harris, 1984;Hauptmann and Warme, 1990;Morabet, 1974;Scheibner and Reijmer, 1999). The three reef-building groups may have occurred separately from each other, such as siliceous sponge mud mounds up to 150 m high in slightly deeper basin positions (Dresnay et al, 1978;Evans and Kendall, 1977), pinnacle coral reefs growing on conglomerates of Paleozoic boulders (Jebel Bou Mokhta: Dresnay, 1971), or isolated bivalve banks in the middle of coastal platforms (Dresnay, 1977).…”

Section: Lower Jurassic Reef Pattern (Fig 2) General Distribution Anmentioning

confidence: 99%

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Jurassic Reef Patterns—the Expression of a Changing Globe

Leinfelder¹,

Schmid²,

Nose³

et al. 2002

Phanerozoic Reef Patterns

156

168

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Jurassic reef patterns reflect the fulminant global and regional changes initiated by the breakup of northern Pangea. The pattern of reef distribution across the Jurassic reflects a complex mix of (1) different and changing tectonic styles along the continental margins and adjacent shelf seas; (2) sea-level rise and its modulating influence on extrinsic sedimentation; (3) oceanographic and climatic reorganizations related to general sea-level rise and the new plate-tectonic configurations; and (4) evolutionary changes in the ecological demands and abilities of reef biota, which, in part, appear to have been triggered by the extrinsic changes during the breakup of northern Pangea. Rifting and onset of drift in the central Atlantic as well as in the western Tethys resulted in a distinct sea-level rise, which transformed Jurassic shelf seas along the northern Tethys margin from dominantly siliciclastic to dominantly carbonate settings. The opening of the ocean passageway from the Tethys to the Caribbean and Pacific completely reorganized global oceanic circulation patterns. During the Late Jurassic, shelf seas were considerably deep, increasing the areas of settings suitable for development of siliceous sponge mounds on the northern Tethys margin. In contrast, many parts of the southern Tethys margin underwent strong morphological changes due to rift tectonics within the Triassic carbonate platforms, which resulted in a completely different pattern in Jurassic reef distribution relative to the northern Tethys. After the end-Triassic extinction event, Jurassic reefs recuperated gradually during the Early Jurassic, with a first major reef domain developing in Morocco. Their temporal distribution through the Middle Jurassic was more balanced, but reefs occurred in scattered domains often distant from each other (e.g., Portugal, France, Madagascar, Iran). Late Jurassic reefs expanded rapidly in the course of the ongoing sea-level rise and the oceanographic reorganization, resulting in mostly interconnected domains. A pattern of waxing and waning of reef abundance and spatial reef distribution through time is superimposed on this trend. It is again, at least to a large extent, correlatable with sea-level fluctuations of greater magnitude. Jurassic reef growth had peaks during the transgressive episodes of the Sinemurian-Pliensbachian, Bajocian-Bathonian, and Oxfordian-Kimmeridgian, with superimposed higher-frequency peaks. The Jurassic represents the peak not only of development of Mesozoic coral reefs but equally of development of sponge mounds. Sponge mounds represent siliceous sponge-microbolite mud mounds, which expanded enormously during the Oxfordian along the European part of the northern Tethys. A peculiar type of bivalve reefs, the Lithiothis reefs, were widespread particularly during the Sinemurian and Pliensbachian, and they might have partially filled a potential reef-growth habitat not occupied by corals, owing to the reduced availability of coral taxa at that time. Bivalve reefs, in particular oyster reefs,...

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Section: Lower Jurassic Reef Pattern (Fig 2) General Distribution Anmentioning

confidence: 99%

Section: Lower Jurassic Reef Pattern (Fig 2) General Distribution Anmentioning

confidence: 99%

Jurassic Reef Patterns—the Expression of a Changing Globe

Leinfelder¹,

Schmid²,

Nose³

et al. 2002

Phanerozoic Reef Patterns

156

168

View full text Add to dashboard Cite

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“…Indeed a possible expression of such induced events may be the stacked array of crusts through the more seaward reaches of the sabkha and intertidal sections, as reported by Strohmenger (this volume). Recognition of such events farther inland (Park, 1983), as are the Miocene Messinian sequences of the Mediterranean region. The high frequency 1-2 m scale cycles illustrated are typical of sedimentation on a gently dipping shelf margin subject to low-amplitude, highfrequency, flooding-evaporation cycles.…”

Section: Resultsmentioning

confidence: 99%

“…Elsewhere, the evaporite-bearing sections bordering the early proto-Atlantic (Fig. 12) have been described by Evans et al (1977), Park (1983) and Cocozza & Gandin (1990), while the Miocene Messinian deposits in the Mediterranean Basin has been documented at length through the work of Schreiber (1976) and Schreiber et al (1977). In all cases high-frequency transgressive-regressive cycles are typical.…”

Section: The Holocene Of Abu Dhabi In a Sequence Contextmentioning

confidence: 86%

The impact of sea‐level change on ramp margin deposition: lessons from the Holocene sabkhas of Abu Dhabi, United Arab Emirates

Park¹

2010

Quaternary Carbonate and Evaporite Sedimentary Facies and Their Ancient Analogues

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Around the globe, the Holocene is replete with examples of the rapid accumulation and outbuilding of sediment wedges in response to, and associated with, a rise in sea level. It is particularly evident among the much-studied shallow-marine carbonate tidal flat association and arguably, nowhere better displayed than by the sabkha cycle developed along the coastal margin of the UAE. This cycle of rapid transgression and steady outward progradation throughout the last 10,000 years is only the most recent of a number of similar cycles that have been a characteristic of ramp margin sedimentation and a feature of stratigraphic associations in the Arabian Basin since the late Palaeozoic. It is not coincidental that these successions lying on top of earlier rifted basin sequences, many salt filled, are home to huge reserves of hydrocarbons.The sabkha cycle, as represented by the Holocene transgressive -highstand sequence found along the northern coast of the Arabian Platform is barely 2 m thick. Its sedimentary facies, associated mineralogical suites and early diagenesis are well documented. The gently sloping ramp margin setting is one that is extremely sensitive to even minor fluctuations in sea level and thin high-frequency sediment cycles are its hallmark. Fluctuations in sea level, however small, produce dramatic changes in sedimentation and groundwater chemistry in this environment, all of which can and do impact the rates of growth and destruction of the sequence. This may occur via increased erosion and ablation, leaching, alteration and replacement of existing minerals and precipitation of new ones, to aerobic destruction of organic material.Coastal flats are situated at the interface between groundwater, seawater and meteoric water which, especially in a sabkha setting, exposes the sequence to a multiplicity of diagenetic overprints. These, through their impact on porosity and permeability properties of potential reservoirs and seals, are of vital interest to the petroleum industry. The preservation potential, or lack thereof, in such tidal flat facies should be recognised as an inherent feature of high-frequency cyclicity. Despite this, relicts and indicators of highfrequency cycles can be observed in cores and wireline logs and offer some insights into the history of formation and preservation of porosity and hydrocarbon migration.

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“…Most reefs described from the Early Jurassic are of Sinemurian and Pliensbachian age. The best information on Liassic reefs comes from the High and Central Atlas of Morocco (DuDresnay, 1977;Park, 1983;Beauvais, 1986), which exhibit the existence of different reef types (e.g., coral reefs, coral-algal reefs, sponge mounds, bivalve mud mounds), some of which are known also from the Triassic. Other Liassic reefs are located in southern Spain (Turnsek et al, 1975), Portugal (Dromart, 1992), the Southern Alps, and British Columbia (Poulton, 1988).…”

Section: Overviewmentioning

confidence: 99%

Pangean shelf carbonates: Controls and paleoclimatic significance of Permian and Triassic reefs

Flügel

1994

Geological Society of America Special Papers

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Late Paleozoic to Liassic reefs and shelf carbonates, forming at the time of accretion and dispersal of Pangea, are specific because of the frequency of reef types other than framework reefs, the importance of microbial contribution, an increase of bioerosional control, the probable invention of algal/coral symbiosis, and the occurrence of major evolutionary crises of reef biota partly connected with extinction events.The data base is biased with regard to time intervals and geographic regions. The use of reef distribution in paleoclimatic reconstructions is strongly dependent on paleomaps available. The current three-step processes model describing the evolution of Mesozoic reefs must be modified. Important constituents of Pangean shelf and reef biota include algae, sponges, and corals exhibiting distinct changes in taxonomic composition, diversity, skeletal mineralogy, and the contribution to reef-building. Reef evolution is characterized by the development of various reef types with different time ranges during accretion and dispersal times of Pangea. Changes in the composition of reef biota with regard to taxa and guild membership are evident during the Permian and Triassic. Reef gaps might have existed during the Early Triassic and perhaps also during the lowermost Early Jurassic. Crucial questions concerning reef evolution in the time of Pangea concern the mode of biotic changes; the lack of Paleozoic holdovers in Triassic reef biotopes and the Scythian reef gap; the coincidence of the late Triassic reef crises with other major modifications of paleogeography, paleoceanography, and climate during the Carnian; and the meaning of the apparently synchronous end-Triassic reef extinction. Both biological and nonbiological processes depending on paleoclimate and paleolatitudes and connected with sea-level changes of different orders should have been active in the control of the evolution of reefs. The latitudinal distributional patterns of Late Paleozoic reefs, however, might not necessarily reflect low-latitudinal warm-water regions as would be derived from recent distributional patterns. Control of reef development, especially by water temperature and light, may have been different for the various types of reef mounds and reefs originating during Pangean times as compared with Holocene coral reefs. Comparisons of distribution patterns of ancient reefs and global circulation models could help in understanding climatic shifts (as indicated by apparently different paleolatitudinal maxima ofCarboniferous to Triassic reefs), in testing long-lasting factors that might have limited reef distribution (e.g., storm tracks, high precipitation areas) as well as in interpreting biogeographical patterns on the shelves around Pangea. Flügel, E., 1994, Pangean shelf carbonates: Controls and paleoclimatic significance of Permian and Triassic reefs, in Klein, G. D" ed., Pangea: Paleoclimate, Tectonics, and Sedimentation During Accretion, Zenith, and Breakup of a Supercontinent: Boulder, Colorado, Geological Society of America Sp...

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Lower Jurassic Carbonate Buildups and Associated Facies, Central and Western Morocco

Cited by 5 publications

References 0 publications

Jurassic Reef Patterns—the Expression of a Changing Globe

Jurassic Reef Patterns—the Expression of a Changing Globe

The impact of sea‐level change on ramp margin deposition: lessons from the Holocene sabkhas of Abu Dhabi, United Arab Emirates

Pangean shelf carbonates: Controls and paleoclimatic significance of Permian and Triassic reefs

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