scholarly journals ?Kimmeridgian-Tithonian shallow- water platform clasts from mass flows on top of the Vardar/Axios ophiolites

2016 ◽  
Vol 47 (1) ◽  
pp. 184
Author(s):  
G. Kostaki ◽  
A. Kilias ◽  
H. J. Gawlick ◽  
F. Schlagintweit
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Eastern Alps ◽  
Sediment Supply ◽  
Carbonate Platforms ◽  
Northern Greece ◽  
Tectonic Event ◽  
Mass Flows ◽  
Sedimentary Succession ◽  
Ophiolite Emplacement

The Late Jurassic to Early Cretaceous sedimentary succession of the Neochorouda Unit lies unconformably on top of the Oreokastro ophiolites of the Vardar/Axios “suture zone” in northern Greece. This succession consists of turbidites and mass flows and provides an upper limit for ophiolite emplacement. New biostratigraphic and microfacies analysis from the clasts in the mass flows were carried out for a better understanding of the Late Jurassic to Early Cretaceous geodynamic history. Microfacies and organism content prove the onset of Late Jurassic carbonate platforms on top of a Middle to Late Jurassic nappe stack striking from the Eastern Alps to the Hellenides. Middle to Late Jurassic nappe stacking towards WNW to NW followed late Early to Middle Jurassic intra-oceanic thrusting in the Western Vardar/Axios (= Neotethys) Ocean and subsequent ophiolite obduction onto the Pelagonian Units forming a thin-skinned orogen on the lower plate. After ophiolite emplacement Kimmeridgian- Tithonian carbonate platforms sealed widespread this tectonic event. Tithonian extension due to mountain uplift resulted in partial erosion of these platforms and new extensional basins were formed. Late Tithonian to earliest Cretaceous erosion of the uplifted nappe stack including the obducted ophiolites resulted in sediment supply into the newly formed basins also east of the Pelagonian Units.

Hooked on salt: Rethinking Alpine tectonics in Hallstatt (Eastern Alps, Austria)

Geology ◽  
2020 ◽  
Author(s):  
Oscar Fernández ◽  
Mario Habermüller ◽  
Bernhard Grasemann
Keyword(s):  
Late Jurassic ◽  
Eastern Alps ◽  
Salt Tectonics ◽  
Alpine Tectonics ◽  
Carbonate Platforms ◽  
Gravity Driven ◽  
World Class ◽  
Permian Salt ◽  
Platform Carbonates ◽  
First Time

Permian salt in the Hallstatt and neighboring salt structures of the Eastern Alps (Austria) crops out along with Triassic deep-water deposits that are at odds with the surrounding Triassic platform carbonates. The traditional interpretation of this juxtaposition is that the salt bodies were emplaced in the Late Jurassic as gravity nappes onto the carbonate platforms, in what has been considered to be the earliest orogenic event in the Eastern Alps. Here we describe for the first time a world-class outcrop of halokinetic sequences in Triassic platform carbonates flanking the Hallstatt diapir. Combining this with other outcrop evidence, we prove that the Hallstatt diapir grew passively during the Triassic, surrounded by carbonate platforms, and extruded to the seabed during the Jurassic. The development of the Hallstatt diapir in a platform setting disproves its emplacement as a gravity-driven nappe, proves the relevance of salt tectonics in the Mesozoic development of the Eastern Alps, and challenges the existence of a Late Jurassic Alpine orogenic event.

LATE JURASSIC-EARLY CRETACEOUS DEPOSITIONAL SYSTEMS OF THE DAMPIER SUB-BASIN-QUO VADIS?

1994 ◽  
Vol 34 (1) ◽  
pp. 566
Author(s):  
Peter Barber
Keyword(s):  
Sea Level ◽  
Early Cretaceous ◽  
Late Jurassic ◽  
Geographic Location ◽  
Sediment Supply ◽  
Submarine Fan ◽  
Potential Reservoir ◽  
Basin Floor ◽  
Quo Vadis ◽  
Mapping Techniques

A diminishing prospect inventory based on traditional structural targets, has placed increasing emphasis upon finding commercially viable stratigraphic traps. This is especially true in the Dampier Sub-basin where recent drilling has identified at least twelve depositional sequences within the Late Jurassic to Early Cretaceous succession. These sequences document a far more complex Late Jurassic to Early Cretaceous sedimentary history than previously acknowledged using traditional litho-stratigraphic mapping techniques. Use of a chronostratigraphic framework to develop Late Jurassic and Early Cretaceous systems tract models, reveals that several repetitive facies suites may be penetrated by the drill, depending on geographic location and frequency of lowstand events. These models have profound implications for prediction of Late Jurassic to Early Cretaceous submarine fan systems, their potential reservoir distribution, and sealing capacity for hydrocarbon entrapment.At least eight lowstand events have been recognised in the Oxfordian to Tithonian sequence alone, associated with both synrift crustal extension and/or related fluctuations in global-eustatic sea level. During these lowstand episodes, huge volumes of coarse clastics were transported by mass-flow into the Lewis Trough with sediment transport of some 5–40 km. The magnitude of shelf-margin tectonic instability, sediment supply, and relative sea level change, controlled the geometry of submarine fan complexes that developed within each lowstand depositional cycle. In general, earlier (Oxfordian) basin-floor sand cycles comprise mixed channel-fill and submarinefan lobe moundforms confined to the Lewis Trough. Following collapse of the Madeleine intra-basinal high in early Kimmeridgian times, these earlier channelised lobes were progressively replaced by more widespread, massive, detached, non-channelised basin floor lobes, which became dominant by end-Tithonian time. The Early Cretaceous succession comprises mainly transgressive-highstand shelf to slope sediments, heralding a change from synrift lowstand to post-rift highstand depositional cycles.Sequence boundaries identified in the Dampier Sub-basin demonstrate a remarkable synchroneity with the worldwide global-eustatic curve, suggesting that a symbiotic relationship may exist between major tectonic events and third-order eustatic cycles, at least within the synrift section of the Dampier Sub-basin.

scholarly journals “Rootless” Ophiolites above the Exhuming Pelagonian Core Complex, Northern Greece

2019 ◽  
Vol 54 (1) ◽  
pp. 60
Author(s):  
Anne Ewing Rassios ◽  
Constantina Ghikas ◽  
Yildirim Dilek ◽  
Dimitrios Kostopoulos
Keyword(s):  
Late Jurassic ◽  
Root Zone ◽  
Local Response ◽  
Core Complex ◽  
Northern Greece ◽  
Active Deformation ◽  
Ophiolite Emplacement ◽  
Exhumation Model ◽  
Metamorphic Facies ◽  
Oceanic Slab

The Mesohellenic ophiolites (MHO) in the Western Hellenides are part of an oceanic slab emplaced onto Pelagonian (Pangaean) continental rocks in the mid-Jurassic with a documented NE ophiolite emplacement. Ophiolitic outliers to the east of the MHO are oceanic lithospheric fragments, not complete ophiolite bodies, preserved above exhumed Pelagonia continental rocks. As these fragments lack connection to original root zone provenance, we refer to these as the “rootless” ophiolites.Pelagonian exhumation, possibly triggered by transcurent shear along its continental margin with the Pindos basin, began by the Late Jurassic and continued into the mid-Cretaceous. Exhumation affected the emplaced oceanic slab in the following ways: i) The metamorphic facies of the basal mélange separating the ophiolite from the Pelagonian basement grades from phyllitic to schist and amphibolite-schist over the exhumed Pelagonia. ii) Ophiolitic remnants are metasomatized where in contact with the exhumed Pelagonian rocks. iii) Remnant ophiolitic fragments are rotated and largely disassociated from their original relative pseudostratigraphic positions in their parent slab. iv) No amphibolite emplacement soles are preserved beneath ophiolitic remnants found directly above Pelagonia.East of Vourinos, remnants of the slab were tectonically entrapped between the exhuming Pelagonian core and its sedimentary overburden, and demonstrate extensional, largely gravitational displacements as well as rotation from original emplacement vectors. Primary constrictive slab emplacement features are obscured, but a general westerly sense of kinematics via listric and extensional faults have been imprinted. In the exhumation model, this "SW topping" direction cannot be interpreted as indicative of an eastern origin of the Pindos Basin ophiolites from the Vardar Zone, but rather as a local response to the uplift of Pelagonia and active deformation of the sedimentary overburden.  

scholarly journals Ophiolite derived material as parent rocks for Late Jurassic bauxite: evidence for Tithonian unroofing in the Northern Calcareous Alps (Eastern Alps, Austria)

2021 ◽  
Author(s):  
Timotheus Martin Christoph Steiner ◽  
Hans-Jürgen Gawlick ◽  
Frank Melcher ◽  
Felix Schlagintweit
Keyword(s):  
Shallow Water ◽  
Late Jurassic ◽  
Xrd Analysis ◽  
Eastern Alps ◽  
Major And Trace Elements ◽  
Parent Material ◽  
Northern Calcareous Alps ◽  
Carbonate Platforms ◽  
Northern Calcareous ◽  
Platform Margin

AbstractIn shallow-water limestones of the Plassen Formation in the Tirolic nappe of the Northern Calcareous Alps, bauxite was formed on karstified and tilted platform margin grainstones to boundstones around the ?Kimmeridgian/Tithonian boundary, or in the Early Tithonian as proven by Protopeneroplis striata Weynschenk, Labyrinthina mirabilis Weynschenk, and Salpingoporella pygmaea Gümbel. The platform established on top of the obducted ophiolite nappe stack. The onset of unroofing at the Kimmeridgian/Tithonian boundary exposed ophiolites to weathering, forming laterites, and bauxites. The weathered ophiolitic material was shed on the tilted, emerged, and karstified platform, where the bauxite accumulated. Continued subsidence led to flooding, and a Tithonian transgressive carbonate sequence sealed the bauxites. XRD analysis of the bauxite yields a composition of mainly boehmite with hematite and some berthierine, kaolinite, and chromite. SEM analysis verified magnetite, hematite, rutile, chromite, zircon, ferropseudobrookite, ilmenite, monazite, xenotime, and garnet distributed in pisoids and within the matrix. The pisoids reach a millimeter in size and partly show cores of older, larger pisoids. The composition of the chromites indicates an ophiolitic origin. Geochemical examination using major- and trace elements points to a mafic andesitic to basaltic parent material contaminated with highly fractionated rocks from an island arc. Formation of Early Tithonian bauxites in shallow-water limestones confirms Middle to Early Late Jurassic ophiolite obduction. This was followed by uplift and unroofing of the orogen from the Kimmeridgian/Tithonian boundary onwards after a period of relative tectonic quiescence with an onset of carbonate platforms during the Kimmeridgian on top of the nappe stack and the obducted Neo-Tethys ophiolites.

AGE MODEL FOR LATE JURASSIC THROUGH EARLY CRETACEOUS USED IN THE GEOLOGIC TIMESCALE 2012/2016 REFERENCE SCALES

2018 ◽  
Author(s):  
James G. Ogg ◽  
◽  
Chunju Huang ◽  
Chunju Huang ◽  
Linda A. Hinnov ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Age Model

Theropod teeth from the basalmost Cretaceous of Anoual (Morocco) and their palaeobiogeographical significance

2009 ◽  
Vol 146 (4) ◽  
pp. 602-616 ◽  
Author(s):  
F. KNOLL ◽  
J. I. RUIZ-OMEÑACA
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Dispersal Events ◽  
Early Occurrence

AbstractThe theropod teeth from the Berriasian (Early Cretaceous) site of Anoual (N Morocco) are described. The assemblage is important in that it comes from one of the very few dinosaur sites of this age globally and the only one for the whole of Gondwana. The theropod teeth from Anoual are morphologically diverse. Most of the material possibly belongs to the clade Dromaeosauridae, which would be an early occurrence for this taxon. The palaeogeographic position of Anoual enables it to provide data on the dispersal events that affected terrestrial faunas during Mesozoic times. A Laurasian influence is evidenced by the presence of Velociraptorinae and, on the whole, the theropod fauna from Anoual provides support for the existence of a trans-Tethyan passage allowing terrestrial faunal interchanges during Late Jurassic and/or earliest Cretaceous times. Additionally, Anoual records the existence of diminutive theropods. However, it cannot yet be determined whether the small size of the specimens is genetic or ontogenetic.

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