Pre-Hirnantian (latest Ordovician) benthic community assemblages: Controls and replacements in a siliciclastic-dominated platform of the eastern Anti-Atlas, Morocco

Álvaro, J. Javier; Vennin, Emmanuelle; Villas, Enrique; Destombes, Jacques; Vizcaïno, Daniel

doi:10.1016/j.palaeo.2005.09.035

Cited by 33 publications

(23 citation statements)

References 9 publications

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“…This period corresponds to an extensional episode in northern Gondwana (Alvaro et al . 2007) during which the Taoudeni and Tindouf basins may have been separated by a threshold. The consistent Silurian record in each basin suggests that a sedimentary link between the two basins over the RR existed at that time (Fig.…”

Section: Discussionmentioning

confidence: 99%

Vertical movements along the northern border of the West African Craton: the Reguibat Shield and adjacent basins

et al. 2013

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The absence of a sedimentary record on large cratonic areas often prevents the reconstruction of the history of their vertical movements. The Reguibat Rise, belonging to the West African Craton, is typically a large basement high, whose Meso-Cenozoic history is poorly known because of the extreme reduction of this sedimentary record. In this paper we present the first thermochronological data from the centre of the Reguibat Rise, and combine them with the geometry of the sedimentary formations in the adjoining Tindouf and Taoudeni basins situated north and south, respectively. Fission track analysis on apatite yields ages from 256 ± 21 Ma to 139 ± 8 Ma, and 120 ± 10 Ma by (U-Th)/He dating. Two competing scenarios are tested based on these data with thermal history modelling. We favour the scenario that includes a Late Jurassic/Early Cretaceous cooling of the samples, based on stratigraphical constraints and the thermochronological results. We then propose a new model for the evolution of this region and reveal the occurrence of a previously unknown major exhumation event at the Jurassic/Cretaceous transition accounting for the main present-day structures.

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Section: Discussionmentioning

confidence: 99%

Vertical movements along the northern border of the West African Craton: the Reguibat Shield and adjacent basins

et al. 2013

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“…Studies of changing sedimentation rates and basin starvation, which result in a switch from dominantly siliciclastic to carbonate sedimentation, at a third order or greater timescale, are common in stable tectonic settings (Beukes, 1977;Haywick et al, 1992;Howe et al, 2000;Carroll et al, 2006;Dahlqvist & Calner, 2006;Á lvaro et al, 2007;Berra, 2007;Spengler & Read, 2010;Saul et al, 2011), where controls on the sedimentation can be defined readily. In rift basins, studies are typically focussed on relatively recent changes in sediment supply (Leeder et al, 1998(Leeder et al, , 2002Collier et al, 2000) or are concerned with longer term variations, for example the change in sedimentation in the North Atlantic across the Jurassic -Cretaceous boundary (Hallam, 1986).…”

Section: Introductionmentioning

confidence: 99%

Stratigraphic development of an Upper Jurassic deep marine syn‐rift succession, Inner Moray Firth Basin, Scotland

2012

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The stratigraphic development of an Upper Jurassic syn‐rift succession exposed at outcrop in the Inner Moray Firth Basin has been investigated using high‐resolution biostratigraphy and sedimentology. A continuous 970 m thick section, exposed in the hangingwall of the Helmsdale Fault was logged in detail. The succession spans 8 Ma and contains eight lithofacies types, which indicate deposition in a deep marine setting. Boulder beds contain large, angular clasts, with bed thicknesses typically >2 m and poor sorting suggesting deposition by debris flows. An inverse clast stratigraphy is observed; the oldest boulder beds contain sandstone clasts of Upper Old Red Sandstone (ORS) with younger debris flows containing clasts of Middle ORS calcareous siltstone. A marked change from siliciclastic to carbonate dominated sedimentation occurred during the Early Tithonian, interpreted primarily as a result of change in lithologies in the footwall catchment from sandstone to calcareous siltstone, which reduced supply of siliciclastic sediment. Secondary factors are identified as increased aridity in the Early Tithonian, which reduced sand supply from the hinterland and a third‐order Early Tithonian eustatic sea‐level rise, which trapped coarser clastic sediment within the hinterland. Biostratigraphy allows calculation of variations in sedimentation rates with recognition of: (1) an early rift phase characterised by sandy turbidite deposition, when sedimentation rates averaged 0.08 m/ky, (2) a rift climax phase from the Early Kimmeridgian where sedimentation rates increased steadily to a maximum of 0.64 m/ky in the Early Tithonian, with strata dominated by boulder scale clast‐supported debris flows and (3) a late stage of rifting from the mid Tithonian, where sedimentation rates decreased to 0.07 m/ky. Overall sedimentation rates are comparable to those of other deep marine rift basins. Unroofing a resistant lithology on the footwall of a rift has important implications for siliciclastic sediment supply in rift basins.

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“…The hummocky cross stratifications identified a few meters below in the Aber section are characteristic of the proximal upper offshore (30-60 m). Finally, in the thick bioclastic L3 limestone bed which seals the effusive activity at Lostmarc'h, the association of bryozoa and crinoids suggests a deepening of the environment with respect to that characterized by brachiopod assemblages, as the L2 level or comparable Moroccan occurrences (Alvaro et al, 2007).…”

Section: The Presence Of Fossiliferous Marine Beds Throughout the Strmentioning

confidence: 93%

A late-Ordovician phreatomagmatic complex in marine soft-substrate environment: The Crozon volcanic system, Armorican Massif (France)

Caroff

Vidal

Bénard

et al. 2009

Journal of Volcanology and Geothermal Research

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International audienceThe mafic lavas and the diabases of Crozon (Armorican Massif, France), belong to an anorogenic Ordovician volcanic complex, emplaced on a rifted passive margin in North Gondwana. Magma passed through syn-volcanic soft sedimentary substrate, which is today mostly composed of alternating sandstones and mudstones, from Llanvirn to Ashgill in age. Field observations together with microscopic studies and geochemical analyses of magmatic rocks lead us to propose a model of volcano formation which combines hydromagmatic processes, peperitic intrusions, a shallow submarine tephra settling, eruption-fed turbidity currents, and a pillow lava effusion. The Crozon outcrops can be used to reconstruct a complete cross-section from the root of the volcanic complex to the lavas and breccias emplaced on the sea floor. The sites expose: (i) a hypabyssal breccia containing mud chunks and coarse-grained diabase clasts with amoeboidal fine-grained magmatic material; (ii) bulbous peperitic sills and pillow-like lobes bearing a great quantity of sediment-derived enclaves of fluidal morphology; (iii) volcaniclastic breccias containing near-spherical magmatic clasts that resulted from the complete fragmentation of sills in the ductile regime; (iv) a rhythmic peperitic breccia interpreted as the product of mingling between thin lava flows and soft calcareous sediment. The Crozon volcanic form, resulting from explosive interaction with subsurface/surface water, was probably a subaqueous collapsed tuff cone. This upper part of the system is synchronous with an Ashgill carbonate sedimentation, which overlies an Ordovician siliciclastic succession deposited in shelf environments

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Pre-Hirnantian (latest Ordovician) benthic community assemblages: Controls and replacements in a siliciclastic-dominated platform of the eastern Anti-Atlas, Morocco

Cited by 33 publications

References 9 publications

Vertical movements along the northern border of the West African Craton: the Reguibat Shield and adjacent basins

Vertical movements along the northern border of the West African Craton: the Reguibat Shield and adjacent basins

Stratigraphic development of an Upper Jurassic deep marine syn‐rift succession, Inner Moray Firth Basin, Scotland

A late-Ordovician phreatomagmatic complex in marine soft-substrate environment: The Crozon volcanic system, Armorican Massif (France)

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