EVOLUTION OF A LOWER PALEOZOIC CONTINENTAL-MARGIN CARBONATE PLATFORM, NORTHERN CANADIAN APPALACHIANS

1989 ◽  
pp. 123-146 ◽  
Author(s):  
NOEL P. JAMES ◽  
ROBERT K. STEVENS ◽  
CHRISTOPHER R. BARNES ◽  
IAN KNIGHT
Keyword(s):  
Continental Margin ◽  
Carbonate Platform ◽  
Lower Paleozoic ◽  
Canadian Appalachians

scholarly journals Tectono-thermal evolution of Oman's Mesozoic passive continental margin under the obducting Semail Ophiolite: a case study Jebel Akhdar, Oman

2018 ◽  
Author(s):  
Arne Grobe ◽  
Christoph von Hagke ◽  
Ralf Littke ◽  
István Dunkl ◽  
Franziska Wübbeler ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Continental Margin ◽  
Thermal Evolution ◽  
Carbonate Platform ◽  
Passive Continental Margin ◽  
Passive Margin ◽  
Temperature Evolution ◽  
Thermal Maturity ◽  
Solid Bitumen ◽  
Shear Sense

Abstract. The Mesozoic sequences of the Oman Mountains experienced only weak post-obduction overprint and deformation, thus they offer a unique natural laboratory to study obduction. We present a study of the pressure and temperature evolution in the passive continental margin under the Oman Ophiolite, using numerical basin models calibrated with thermal maturity data, fluid inclusion thermometry and low-temperature thermochronology. Thermal maturity data from the Adam Foothills constrain burial in the foredeep moving in front of the advancing nappes to be at least 4 km. Peak temperature evolution in the carbonate platform under the ophiolite is only weakly dependent on the temperature of the overriding nappes which have cooled during transport from the oceanic subduction zone to emplacement. Fluid-inclusion thermometry yields pressure-corrected homogenization temperatures of 225 to 266 °C for veins formed during progressing burial, 296–364 °C for veins related to peak burial and 184 to 213 °C for veins associated with late-stage strike-slip faulting. In contrast, the overlying Hawasina nappes have not been heated above c. 170 ºC, as witnessed by only partial resetting of the zircon (U-Th)/He thermochronometer. In combination with independently determined temperatures from solid bitumen reflectance, we infer that the fluid inclusions of peak-burial-related veins formed at minimum pressures of 225–285 MPa. This implies that the rocks of the future Jebel Akhdar Dome were buried under 8–10 km of ophiolite on top of 2 km of sedimentary nappes, which is in agreement with thermal maturity data of solid bitumen reflectance and Raman spectroscopy. Burial of the passive margin under the ophiolite results in sub-lithostatic pore pressures, in agreement with observations on veins formed in dilatant fractures in the carbonates. We infer that overpressure is induced by rapid burial under the ophiolite nappes. Obduction-related tilt of the passive margin in combination with overpressure in the passive margin caused fluid migration towards the south in front of the nappes. Exhumation of the Jebel Akhdar as indicated by our zircon (U-Th)/He data, integrated with existing data, started as early as the late Cretaceous to early Cenozoic, linked with extension along a major listric shear zone with top-to-NNE shear sense, together with an early phase of extensional dome formation. The carbonate platform and obducted nappes of the whole Jebel Akhdar cooled together below c. 170 °C between 50 and 40 Ma, before the final stage of anticline formation.

scholarly journals A missing link in the peri-Gondwanan terrane collage: the Precambrian basement of the Moroccan Meseta and its lower Paleozoic cover

2018 ◽  
Vol 55 (1) ◽  
pp. 33-51 ◽  
Author(s):  
Dominik Letsch ◽  
Mohamed El Houicha ◽  
Albrecht von Quadt ◽  
Wilfried Winkler
Keyword(s):  
Carbonate Platform ◽  
Source Area ◽  
Source Rocks ◽  
Lower Paleozoic ◽  
Northern Margin ◽  
Precambrian Geology ◽  
The North ◽  
Late Cambrian ◽  
Paleozoic Rocks ◽  
Rifted Margin

This article provides stratigraphic and geochronological data from a central part of Gondwana’s northern margin — the Moroccan Meseta Domain. This region, located to the north of the Anti-Atlas area with extensive outcrops of Precambrian and lower Paleozoic rocks, has hitherto not received much attention with regard to its Precambrian geology. Detrital and volcanic zircon ages have been used to constrain sedimentary depositional ages and crustal affinities of sedimentary source rocks in stratigraphic key sections. Based on this, a four-step paleotectonic evolution of the Meseta Domain from the Ediacaran until the Early Ordovician is proposed. This evolution documents the transition from a terrestrial volcanic setting during the Ediacaran to a short-lived carbonate platform setting during the early Cambrian. The latter then evolved into a rifted margin with deposition of thick siliciclastic successions in graben structures during the middle to late Cambrian. The detritus in these basins was of local origin, and a contribution from a broader source area (encompassing parts of the West African Craton) can only be demonstrated for postrifting, i.e., laterally extensive sandstone bodies that seal the former graben. In a broader paleotectonic context, it is suggested that this Cambrian rifting is linked to the opening of the Rheic Ocean, and that several peri-Gondwanan terranes (Meguma and Cadomia–Iberia) may have been close to the Meseta Domain before drifting, albeit some of them seem to have been constituted by a distinctly different basement.

scholarly journals Neogene evolution and demise of the Amapá carbonate platform, Amazon continental margin, Brazil

2019 ◽  
Vol 105 ◽  
pp. 185-203 ◽  
Author(s):  
A.M. Cruz ◽  
A.T. Reis ◽  
J.P. Suc ◽  
C.G. Silva ◽  
D. Praeg ◽  
...  
Keyword(s):  
Continental Margin ◽  
Carbonate Platform

New conodont records of the Los Sombreros Formation (Cambrian–Ordovician) from the Western Precordillera, Argentina: biostratigraphic and palaeoenvironmental implications

2019 ◽  
Vol 157 (4) ◽  
pp. 539-550
Author(s):  
Gabriela Torre ◽  
Guillermo L. Albanesi
Keyword(s):  
Continental Margin ◽  
Carbonate Platform ◽  
South American ◽  
The South ◽  
Depositional History ◽  
The Matrix ◽  
Minimum Age ◽  
History Of ◽  
Lower Palaeozoic ◽  
Early Palaeozoic

AbstractThe presence of a carbonate platform that interfingers towards the west with slope facies allows for the identification of an ancient lower Palaeozoic continental margin in the Western Precordillera of Argentina. The Los Sombreros Formation is essential for the interpretation of the continental slope of the Precordillera, which accreted to Gondwana as part of the Cuyania Terrane in the early Palaeozoic. The age of these slope deposits is controversial; therefore, a precise biostratigraphic scheme is critical to reveal the evolution of the South American continental margin of Gondwana. The study of lithic deposits of two sections of the Los Sombreros Formation, the El Salto and Los Túneles sections, provides important information for further understanding the depositional history of the slope. At El Salto section, the conodonts recovered from an allochthonous block refer to the Cordylodus proavus Zone (upper Furongian). The conodonts recovered from the matrix of a calclithite bed of the Los Sombreros Formation in the Los Túneles section are assigned to the Lenodus variabilis Zone (early Darriwilian), providing a minimum age for this stratigraphic unit. In addition, clasts from this sample yielded conodonts from the Paltodus deltifer − Macerodus dianae zones (upper Tremadocian). The contrasting conodont colour alterations and preservation states from the elements of two latter records, coming from the same sample, argue the reworked clasts originated in the carbonate platform and later transported to the slope during the accretion process of the Precordilleran Terrane to the South American Gondwanan margin during the Middle–Late Ordovician.

Comment and Reply on "Roberts Mountains allochthon: Stratigraphic comparison with lower Paleozoic outer continental margin strata of the northern Canadian Cordillera"

Geology ◽  
1989 ◽  
Vol 17 (11) ◽  
pp. 1063
Author(s):  
J. G. Johnson ◽  
M. A. Murphy ◽  
Robert J. W. Turner ◽  
Raul J. Madrid ◽  
Elizabeth L. Miller
Keyword(s):  
Continental Margin ◽  
Canadian Cordillera ◽  
Lower Paleozoic

scholarly journals Sedimentology and paleoenvironments of the La Laja Formation (Cambrian), Quebrada La Laja, Sierra Chica de Zonda, San Juan, Argentina.

2010 ◽  
Vol 33 (1) ◽  
pp. 19 ◽  
Author(s):  
Fernando J. Gomez ◽  
Ricardo A. Astini
Keyword(s):  
Carbonate Platform ◽  
San Juan ◽  
Lower Paleozoic ◽  
Depositional History ◽  
Subaerial Exposure ◽  
South Central ◽  
Subtidal Environment ◽  
History Of ◽  
Marine Facies ◽  
Shallow Subtidal

The La Laja Formation is a key unit regarding the hypothesis of the Argentine Precordillera as a Laurentia-derived allochtonous terrane in the south central Andes. Together with the Cerro Totora Formation it comprises the oldest unit exposed at the base of the Lower Paleozoic carbonate platform of the Precordillera. According to previous work these units record the rifting-drifting history of this terrane exotic to Gondwana. The La Laja Formation contrasts with the rest of the overlying units of the Cambro-Ordovician carbonate platform by being partly mixed carbonate-siliciclastic. A detailed facies analysis of the five recognized members in the reference section at Quebrada La Laja (Sierra Chica de Zonda, San Juan Province) allow the recognition of 19 microfacies grouped into four main environmentally significant associations: 1) a storm-influenced, deep subtidal environment with variable influx of fine siliciclastic sediments; 2) shallow subtidal, 3) mixed shallow subtidal and 4) shallow subtidal to intertidal occasionally with well developed high-frequency tidal flat cycles. No deeper basinal or slope facies were found. In contrast, the unit largely records shallow-marine facies with some evidence of subaerial exposure. Medium to coarse, calcareous, feldspar-rich sandstones and sandy limestones characterize the El Estero Member. The base of the Soldano Member shows profuse development of cyclicity with capping oolitic shoals. This member and the upper Juan Pobre Member contain deeper subtidal intervals, below the storm weather wave base, with high percentages of fine terrigenous material represented by shaly marls and nodular limestones. Skeletal-rich and oolite-rich storm beds are recorded within them. Relative shallowing to subaerial environments recorded within the Rivadavia and Las Torres members, with the development of ribbon limestones, intraclastic rudstones, microkarstic surfaces and exposure breccias. Herringbone cross-bedded oolite shoals are common at the top of the uppermost Las Torres Member. The transition into the overlying Zonda Formation is represented by an abrupt rearrangement of the depositional systems and development of meter-scale microbial-rich peritidal cycles. Several orders of superposed cyclicity are recorded within the La Laja Formation. Larger-scale cycles ('Grand Cycles') are inferred from alternating members with important amounts of siliciclastics, whereas meter-scale cycles indicate higher frequency superposed mechanisms. Altogether these show a complex depositional history linking environmental and tectono-eustatic signatures.

Deciphering the geodynamic evolution of the Dinaric orogen through the study of the ‘overstepping’ Cretaceous successions

2020 ◽  
Vol 157 (8) ◽  
pp. 1238-1264
Author(s):  
Giuseppe Nirta ◽  
Martin Aberhan ◽  
Valerio Bortolotti ◽  
Nicolaos Carras ◽  
Francesco Menna ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Continental Margin ◽  
Late Jurassic ◽  
Carbonate Platform ◽  
Depositional Environments ◽  
Small Scale ◽  
Large Area ◽  
Geodynamic Evolution ◽  
Sedimentary Evolution ◽  
Platform System

AbstractAlong the Dinaric–Hellenic orogen, the Late Jurassic – Early Cretaceous ophiolite obduction over the Adria continental margin was sealed by sedimentation of clastic terrestrial deposits rapidly followed by a widespread carbonate platform system since the Early Cretaceous period. These Cretaceous sediments presently crop out over areas of varying extension, from several hundred kilometre wide undeformed continuous covers to small-scale tectonic slivers involved in the tectonic stack following the latest Cretaceous–Palaeogene collision. These deposits are unconformably sedimented above the units formed by the Late Jurassic to Early Cretaceous nappe stacking above the eastern Adria continental margin. We studied these deposits in a large area between western Serbia and eastern Bosnia. In the studied area, these deposits are divided into three lithostratigraphic groups according to their age, depositional environment and type of underlying basement. The Mokra Gora Group sediments (upper Aptian–Maastrichtian) were deposited on top of previously obducted and weathered ophiolites, the Kosjerić Group (Cenomanian–Campanian) overlies composite tectonic units comprising obducted ophiolites and their underlying continental basement portions, while the Guča Group (Campanian–Maastrichtian) exclusively rests on top of continental basement. The reconstructed sedimentary evolution of these groups, together with the comparison with the syn- and post-obduction deposits at the front of the ophiolitic nappe(s) in a wider area of the internal Dinarides (e.g. Pogari Group and Bosnian flysch), allowed us to clarify the obduction mechanisms, including their tectonic context, the changes in depositional environments and the timing of depositional and tectonic events, and, in a wider view, shed light on the geodynamic evolution of the Dinaric belt.

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