Search results for " subsidence"

Spatial and temporal distribution of ooids along a Jurassic carbonate ramp: Amellago outcrop transect, High-Atlas, Morocco

2010

Carbonate ramp systems are widespread throughout the geological record, but very few areas have seismic-scale, continuous and structurally undeformed outcrops that allow reliable interpretation of facies distributions and stacking patterns. The Amellago outcrop shows the detailed depositional and stratigraphic relationships of an ooid-dominated ramp system that is almost completely exposed along a dip profile (37 km long and 1000 m thick) in the Lower to Middle Jurassic of the southern High Atlas, Morocco. Ammonite and brachiopod fauna provide excellent biostratigraphic control on small scale stacking patterns. At Amellago, the evolution of depositional environments is evident at different …

Geomorphological west-east-section through the north chilean andes near antofagasta

2006

The extremely arid western slope of the Andes near Antofagasta is an area of young tectonic movements on the one hand, but of very low erosion rates on the other. Therefore the relief is characterized by very old erosional forms, but fresh and clearly visible tectonic forms. This is quite evident from the following characteristics of a west-east-section from the Coastal Cordillera to the High Cordillera: 1. The great height and steepness of the western escarpment of the Coastal Cordillera, devoid of deep valleys. 2. The preservation of the miocene and pliocene caliche deposits with highly soluble nitrates in the eastern part of the Coastal Cordillera and of the landforms covered by them. 3.…

Recycling plus: A new recipe for the formation of Alpine-Himalayan orogenic mantle lithosphere

2013

Abstract The origin of the lithospheric mantle beneath accretionary orogens is enigmatic; although severe compression of the buoyant crust occurs, the mantle lithosphere is generally thought to be removed and returned to the convecting mantle. We suggest that during the accretion of oceanic arcs and small continental blocks in the Mediterranean region, and more generally throughout the whole Alpine–Himalayan orogenic belt, the mantle lithosphere is newly created and composed of intimately mixed peridotite and crustal material from the forearc region. Potassium-rich volcanic rocks emplaced sometimes more than 30 Ma after the formation of this lithosphere carry evidence for the presence of ex…

Mid-Triassic to Early Liassic clastic/evaporitic deposits over the Maghreb Platform

2003

Abstract The development of Triassic to Lower Liassic clastic/evaporitic series over the epicratonic Maghreb Platform is closely associated with the eastern opening of a Tethyan marine domain between Africa and Europe. West of the platform, Morocco became separated from North America in Late Triassic times by rifting along the axis of the Proto-Atlantic Ocean. In addition, NE–SW and ENE–WSW trending Atlasic half-grabens formed, essentially in Morocco, as part of a Late Triassic/Early Liassic Atlas rifting episode. This is the tectonic context in which the red bed to evaporite sequences were deposited. A first depositional pattern is illustrated by the areally extensive onlapping of Upper Tr…

An exceptional rocky shore preserved during Oligocene (Late Rupelian) transgression in the Upper Rhine Graben (Mainz Basin, Germany)

2012

The Early Oligocene (Late Rupelian) Alzey Formation (Mainz Basin, Upper Rhine Graben, Germany) records the development of a rocky coast depositional system during transgression. The formation unconformably overlies Permian bedrock across a composite transgressive ravinement surface. Exposure of the surface shows a succession of subplanar bedrock terraces, separated by near-vertical risers. Terraces show a broad staircase geometry and display wave-erosional features (notches, sea stacks, furrows). Detailed sedimentological and palaeoecological investigations reveal prograding beachface and shoreface depositional units that overlie terraces and are adjacent to risers. Terraces are interpreted…

On the origin of the southern Permian Basin, Central Europe.

2000

A detailed study of the structural and stratigraphic evolution of the Southern Permian Basin during latest Carboniferous to Early Jurassic times, supported by quantitative subsidence analyses and forward basin modelling for 25 wells, leads us to modify the conventional model for the Rotliegend-Zechstein development of this basin. The Late Permian-Early Jurassic tectonic subsidence curves are typical for a Permian to Early Triassic extensional stage that is followed by thermal subsidence. However, a purely extensional model is extremely problematic because active faulting during this time is 'minor' and generally hard to document. Using inverse techniques to model the subsidence curves, we q…

Mesozoic discontinuities in the Panormide Carbonate Platform: constraints on the palaeogeography of the central Mediterranean

2008

Rejuvenation and erosion of the cratonic lithosphere

2008

Cratons are ancient continental nuclei that have resisted significant fragmentation for almost two billion years. Yet, many cratons also experience phases of instability in the form of erosion and rejuvenation of their thick lithospheric mantle keels. Melting governed by redox processes as well as small-scale convection play a key role in triggering such instability. Cratons are the ancient cores of continents, characterized by tectonic inactivity, a thick mantle lithosphere and low heat flow. Although stable as tectonically independent units for at least the past 2 billion years, cratons have experienced episodic rejuvenation events throughout their history. The lower part of the lithosphe…