Stratigraphic evolution of Triassic arc-backarc system in northwestern Croatia

2005 ◽  
Vol 176 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Špela Goričan ◽  
Josip Halamić ◽  
Tonći Grgasović ◽  
Tea Kolar-Jurkovšek
Keyword(s):  
Continental Margin ◽  
Middle Triassic ◽  
Extensional Tectonics ◽  
Carbonate Platforms ◽  
Backarc Basin ◽  
Sea Floor ◽  
Western Tethys ◽  
Backarc Basins ◽  
Sea Floor Spreading ◽  
Stratigraphic Evolution

Abstract Middle Triassic arc-related extensional tectonics in the western Tethys generated a complex pattern of intra-and backarc basins. We studied volcano-sedimentary successions of subsided continental-margin blocks (Mts. Žumberak and Ivanščica) and of dismembered incomplete ophiolite sequences interpreted as remnants of a backarc basin (Mts. Medvednica and Kalnik) in northwestern Croatia. We dated the successions with radiolarians, conodonts, foraminifers, algae, and sponges. The continental margin experienced a phase of accelerated subsidence in the late Anisian that was approximately coincident with the onset of intermediate and acidic volcanism; pelagic sediments with volcaniclastics accumulated atop subsided carbonate platforms. These relatively shallow basins were later infilled completely by prograding platforms in the late Ladinian-Carnian. In the backarc basin, sea-floor spreading initiated near the Anisian-Ladinian boundary and continued into the late Carnian. Pillow basalts were erupted and interlayered with radiolarian cherts and shales. The studied area was a part of a larger Triassic arc-backarc system preserved in the southern Alps, Alpine-Carpathian Belt, Dinarides, and Hellenides. Volcano-sedimentary successions of Mts. Medvednica and Kalnik are relics of the Meliata-Maliak backarc basin. In comparison to other previously dated oceanic remnants of this system, the longest continuous sea-floor spreading is now documented in one restricted tectonic unit.

Middle Triassic carbonate platforms in eastern Iberia: Evolution of their fauna and palaeogeographic significance in the western Tethys

2015 ◽  
Vol 417 ◽  
pp. 236-260 ◽  
Author(s):  
M.J. Escudero-Mozo ◽  
A. Márquez-Aliaga ◽  
A. Goy ◽  
J. Martín-Chivelet ◽  
J. López-Gómez ◽  
...  
Keyword(s):  
Middle Triassic ◽  
Carbonate Platforms ◽  
Western Tethys

scholarly journals Facies analysis of the Lower-Middle Toarcian in the External Subbetic (provinces of Murcia and Granada, Southern Spain): palaeoenvironmental conditions

2019 ◽  
Author(s):  
José Miguel Molina ◽  
Luis M Nieto
Keyword(s):  
Lower Jurassic ◽  
Southern Spain ◽  
Tectonic Activity ◽  
Oceanic Circulation ◽  
Carbonate Platforms ◽  
The South ◽  
Sea Floor ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Facies Types

Toarcian sedimentary rocks are well recorded in the Subbetic (Betic External Zones, Southern Spain) as part of the Zegrí Formation (upper Pliensbachian-Aalenian). These rocks were deposited in the South Iberian Palaeomargin in the Western Tethys. We study the lower-middle Toarcian facies in two sections in the External Subbetic and their palaeoenvironmental interpretation. The lower-middle Toarcian have more than 160 m in thickness, the maximum for this time in all the Betic External Zones. Five types of lithofacies are differentiated: 1) Grey-yellow marl-marly limestone rhythmite and limestones (lower part of the Polymorphum Zone); 2) dark marls (upper part of the Polymorphum Zone and lower part of the Serpentinum Zone); 3) thin bedded grey-yellow limestones, locally with chert and abundant slumps (upper part of the Serpentinum Zone); 4) grey marls and marly limestones (Bifrons and Gradata Zones); and 5) yellow-brown laminated calcisiltites and calcarenites, intercalated in facies 3 and 4. Facies 1 to 4 are interpreted as hemipelagites, deposited by the slow accumulation, on a quiet sea floor of biogenic and very fine terrigenous particles. Facies 2 was deposited in rather depleted oxygen conditions with slightly dysoxic bottom waters but discarding completely anoxic conditions. The Toarcian Oceanic Anoxic Event (T-OAE) is recorded in this facies 2 by some increase of total organic carbon (maximum of 1.05 wt.%) and redox sensitive elements, the decrease of CaCO3, and the negative excursion of δ13C observed at the base of Serpentinum Zone. Facies 5 are mainly peloidal grainstone with bioclasts (brachiopods, bivalves, and echinoderms), ooids and allochthonous shallow water foraminifera, and packstone-wackestone of bioclasts (mainly radiolarians) and peloids. This facies 5 with parallel lamination and locally with normal grading, low angle, wavy, and hummocky cross stratification is interpreted as tempestites related with tropical cyclones, and/or internalites. The influence of adjacent emerged lands and carbonate platforms, differential subsidence by local tectonics, sediment winnowing by currents, sedimentation rates, bioturbation, and diagenesis, may have had more importance in the distribution of the facies types than depth. The evolution during the lower-middle Toarcian was mainly controlled by tectonics after the Pliensbachian break-up of the Lower Jurassic platform, together with a relative sea-level change. Also the beginning of basaltic submarine volcanism to the South in some Median Subbetic areas had influence. The diversified physiography related to synsedimentary tectonic activity and oceanic circulation patterns, determined different intensities of winnowing and oxygenation on the sea-floor. The T-OAE is recorded in the base of Serpentinum Zone. The general re-oxygenation after the T-OAE could be favoured by changes in oceanic currents and by the tempestite/internalite inputs during the upper part of Serpentinum and Bifrons zones.

scholarly journals Reconstruction of tectonically disrupted carbonates through quantitative microfacies analyses: an example from the Middle Triassic of Southern Italy

Facies ◽  
2021 ◽  
Vol 67 (3) ◽  
Author(s):  
Adriano Guido ◽  
Giuseppe Palladino ◽  
Matteo Sposato ◽  
Franco Russo ◽  
Giacomo Prosser ◽  
...  
Keyword(s):  
Middle Triassic ◽  
Southern Italy ◽  
Original Position ◽  
Tectonic Deformation ◽  
Carbonate Platforms ◽  
Southern Apennines ◽  
Central Mediterranean ◽  
Western Tethys ◽  
Diagenetic Alteration ◽  
Tethys Realm

AbstractThe main goal of the paper is the reconstruction of a Middle Triassic buildup cropping out in the central part of the Southern Apennines. Middle Triassic reefs of the western Tethys realm are well known in the Northern and Southern Alps. In contrast, few studies of the Anisian–Ladinian carbonate platforms of the southern Apennines are available, due to the diagenetic alteration and tectonic disruption that hinder their paleoenvironmental and stratigraphic reconstruction. In an attempt to fill this gap, and to improve the knowledge on the Anisian–Ladinian carbonates of central Mediterranean area, this research is focused on a carbonate buildup cropping out in the “La Cerchiara” area, Sasso di Castalda (Basilicata, Southern Italy). The buildup, affected by intense tectonic deformation associated with the development of the Apennine thrust and fold belt, was studied using a statistical evaluation of the quantitative microfacies data. The research enabled a reconstruction of the original stratigraphic relationships of the various buildup fragments. A positive linear regression between the sample positions vs the percentage of autochthonous carbonates indicates an increase of the autochthons carbonate toward the top of the succession. The allochthonous fabrics (packstone/wackestone) at the base of the section (Unit IIIa) pass gradually upward into autochthonous (boundstones) facies (Units IIIb, I), consisting of microbialites (clotted peloidal micrite, microbial-derived laminae, and aphanitic micrite), microproblematica and cyanobacterial crusts, with few encrusting skeletal organisms. Statistical data suggest that units IIIa, IIIb, and I are in stratigraphic order while unit II appears to have been moved by tectonic dislocation from its original position at the base of the succession. The absence of metazoan reef framework, and the richness of micro-encrusters, autochthonous micrite and synsedimentary cements, suggest a mud-mound style of growth for the carbonate bodies of the Southern Apennine during the Anisian.

Ridge subduction: kinematics and implications for the nature of mantle upwelling

1993 ◽  
Vol 30 (5) ◽  
pp. 893-907 ◽  
Author(s):  
Edward Farrar ◽  
John M. Dixon
Keyword(s):  
North America ◽  
Continental Margin ◽  
Plate Tectonics ◽  
Thermal Anomaly ◽  
Driving Mechanism ◽  
Mantle Upwelling ◽  
Basin And Range Province ◽  
Sea Floor ◽  
Ridge Subduction ◽  
Sea Floor Spreading

Ridge subduction follows the approach of an oceanic spreading centre towards a trench and subduction of the leading oceanic plate beneath the overriding plate. There are four possible kinematic scenarios: (1) welding of the trailing and overriding plates (e.g., Aluk–Antarctic Ridge beneath Antarctica); (2) slower subduction of the trailing plate (e.g., Nazca–Antarctic Ridge beneath Chile and Pacific–Izanagi Ridge beneath Japan); (3) transform motion between the trailing and overriding plates (e.g., San Andreas Transform); or (4) divergence between the overriding and trailing plates (e.g., Pacific – North America). In case 4, the divergence may be accommodated in two ways: the overriding plate may be stretched (e.g., Basin and Range Province extension, which has brought the continental margin into collinearity (and, therefore, transform motion) with the Pacific – North America relative motion); or divergence may occur at the continental margin and be manifest as a change in rate and direction of sea-floor spreading because the pair of spreading plates changes (e.g., from Pacific–Farallon to Pacific – North America), spawning a secondary spreading centre (i.e., Gorda – Juan de Fuca – Explorer ridge system) that migrates away from the overriding plate.Mantle upwelling associated with sea-floor spreading ridges is widely regarded as a passive consequence, rather than an active cause, of plate divergence. Geological and geophysical phenomena attendant to ridge–trench interaction suggest that regardless of the kinematic relations among the three plates, a thermal anomaly formerly associated with the ridge migrates beneath the overriding plate. The persistence of this thermal anomaly demonstrates that active mantle upwelling may continue for tens of millions of years after ridge subduction. Thus, regardless of whether the mantle upwelling was active or passive at its origin, it becomes active if the spreading continues for sufficient time and, thus, must contribute to the driving mechanism of plate tectonics.

scholarly journals Facies analysis of the Lower-Middle Toarcian in the External Subbetic (provinces of Murcia and Granada, Southern Spain): palaeoenvironmental conditions

2019 ◽  
Author(s):  
José Miguel Molina ◽  
Luis M Nieto
Keyword(s):  
Lower Jurassic ◽  
Southern Spain ◽  
Tectonic Activity ◽  
Oceanic Circulation ◽  
Carbonate Platforms ◽  
The South ◽  
Sea Floor ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Facies Types

Toarcian sedimentary rocks are well recorded in the Subbetic (Betic External Zones, Southern Spain) as part of the Zegrí Formation (upper Pliensbachian-Aalenian). These rocks were deposited in the South Iberian Palaeomargin in the Western Tethys. We study the lower-middle Toarcian facies in two sections in the External Subbetic and their palaeoenvironmental interpretation. The lower-middle Toarcian have more than 160 m in thickness, the maximum for this time in all the Betic External Zones. Five types of lithofacies are differentiated: 1) Grey-yellow marl-marly limestone rhythmite and limestones (lower part of the Polymorphum Zone); 2) dark marls (upper part of the Polymorphum Zone and lower part of the Serpentinum Zone); 3) thin bedded grey-yellow limestones, locally with chert and abundant slumps (upper part of the Serpentinum Zone); 4) grey marls and marly limestones (Bifrons and Gradata Zones); and 5) yellow-brown laminated calcisiltites and calcarenites, intercalated in facies 3 and 4. Facies 1 to 4 are interpreted as hemipelagites, deposited by the slow accumulation, on a quiet sea floor of biogenic and very fine terrigenous particles. Facies 2 was deposited in rather depleted oxygen conditions with slightly dysoxic bottom waters but discarding completely anoxic conditions. The Toarcian Oceanic Anoxic Event (T-OAE) is recorded in this facies 2 by some increase of total organic carbon (maximum of 1.05 wt.%) and redox sensitive elements, the decrease of CaCO3, and the negative excursion of δ13C observed at the base of Serpentinum Zone. Facies 5 are mainly peloidal grainstone with bioclasts (brachiopods, bivalves, and echinoderms), ooids and allochthonous shallow water foraminifera, and packstone-wackestone of bioclasts (mainly radiolarians) and peloids. This facies 5 with parallel lamination and locally with normal grading, low angle, wavy, and hummocky cross stratification is interpreted as tempestites related with tropical cyclones, and/or internalites. The influence of adjacent emerged lands and carbonate platforms, differential subsidence by local tectonics, sediment winnowing by currents, sedimentation rates, bioturbation, and diagenesis, may have had more importance in the distribution of the facies types than depth. The evolution during the lower-middle Toarcian was mainly controlled by tectonics after the Pliensbachian break-up of the Lower Jurassic platform, together with a relative sea-level change. Also the beginning of basaltic submarine volcanism to the South in some Median Subbetic areas had influence. The diversified physiography related to synsedimentary tectonic activity and oceanic circulation patterns, determined different intensities of winnowing and oxygenation on the sea-floor. The T-OAE is recorded in the base of Serpentinum Zone. The general re-oxygenation after the T-OAE could be favoured by changes in oceanic currents and by the tempestite/internalite inputs during the upper part of Serpentinum and Bifrons zones.

The Canadian Cordillera, the Hellenides, and the Sea-Floor Spreading Theory

1972 ◽  
Vol 9 (6) ◽  
pp. 709-743 ◽  
Author(s):  
Jean Dercourt
Keyword(s):  
Pacific Ocean ◽  
Oceanic Crust ◽  
Continental Margin ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Late Triassic ◽  
Canadian Cordillera ◽  
Transform Faults ◽  
Sea Floor ◽  
Sea Floor Spreading

The theory of plate tectonics is applied to the tectonic evolution of the Hellenides and the Canadian Cordillera. In the Hellenides a Tethyan zone of sea-floor spreading developed within the continental crust during Triassic time and functioned until the end of the Middle Jurassic. It led to the formation of two plates, each with continental and oceanic segments, that were separated in some places by accreting plate margins and in others by transform faults. In Late Jurassic time the mid-Tethyan ridge became inactive as new ridges developed in the Atlantic Ocean. From Late Jurassic to Recent time, Tethyan oceanic crust largely disappeared under one of the cratons. The chronology of tectonic events in the Hellenides corresponds well with that of sea-floor spreading in the Atlantic.Four periods of sea-floor spreading were involved in the formation of the Canadian Cordillera: (1) a Silurian? to Early Devonian period when an Archeo-Pacific Ocean separated the Canadian craton with a stable sedimentary margin from a volcanic archipelago; (2) a Middle Devonian to Permian period when the extinct volcanic archipelago was bounded to the west by a spreading Paleo-Pacific Ocean, and to the east by a tectonic contact which was consuming Archeo-Pacific oceanic crust; part of this crust was obducted over the continental margin; (3) a Late Triassic to Middle Jurassic period when a second volcanic archipelago separated a spreading Neo-Pacific Ocean from the continental margin; and (4) a Late Jurassic to Recent period where spreading occurred in both the Atlantic and Pacific Oceans, subjecting the second volcanic archipelago and the continental margin to major tectonism; since the Paleocene, the Cordillera has slid towards the NNW along transform faults.

The Continental Margin Off Labrador and Eastern Newfoundland–Morphology and Geology

1972 ◽  
Vol 9 (11) ◽  
pp. 1394-1430 ◽  
Author(s):  
A. C. Grant
Keyword(s):  
Continental Margin ◽  
Structural Model ◽  
Geologic Structure ◽  
Western Atlantic ◽  
Study Region ◽  
Vertical Movements ◽  
Sea Floor ◽  
Precambrian Rocks ◽  
Vertical Displacements ◽  
Sea Floor Spreading

Seismic profiler surveys have defined the landward limit of presumed Mesozoic–Cenozoic deposits on the continental shelf off Labrador and eastern Newfoundland. Along the Labrador coast the contact of these deposits with Precambrian rocks coincides with a pronounced 'marginal channel'; off eastern Newfoundland their contact with rocks of the Appalachian System is marked by a landward-facing escarpment. The physiographic relief characterizing this contact zone reflects erosional exploitation of the associated contrast in erosional susceptibility. The chief erosional agent is considered to have been the Quaternary glaciers. The marginal channel off northern Labrador is indicated as a zone of major faulting, which probably further enhanced the erosional vulnerability. The transverse depressions cutting the outer shelf off Labrador and Newfoundland are likewise considered to be zones of structural dislocation, which have been physiographically emphasized through processes of erosion.Integration of the seismic profiler results with other geophysical and geological data from the study region consistently supports the concept that the morphology of the continental margin expresses fundamental elements of geologic structure. Available evidence can apparently be reasonably synthesized in terms of a structural model based upon differential vertical movements of segments of continental crust. By this approach the structure of the continental margin north of the Grenville Front off Labrador may be very different from that of the continental margin bordering the western Atlantic Ocean to the south. In addition, the continental fragments represented by Orphan Knoll and Flemish Cap are indicated as having experienced only vertical displacements during postulated episodes of late and post-Cretaceous sea-floor spreading.

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