Interplay Of Tectonics Research Articles

Sequence stratigraphic analysis and paleogeographic interpretation of the Buntsandstein and Muschelkalk facies (Permo-Triassic) in the SE Iberian Range, E Spain

The Iberian Ranges is an Alpine structure trending NW-SE in Central Spain. They first appeared as small, intracratonic basins in the Early Permian, and experienced different periods of extensional tectonics during the Mesozoic and Cenozoic controlled by ancient (Hercynian or older) fracture systems and at least two periods of compressive, inversion tectonics. The Permian and Triassic of the SE Iberian Ranges are of “Germanic Type”. Within the prevailing Buntsandstein and Muschelkalk facies, eight formations are recognized. Pollen and spore assemblages and some ammonoid horizons allow for age-assessments ranging from Thuringian (Late Permian) to Carnian (Late Triassic). Two phases of sedimentation can be distinguished during the early extensional period. The first phase (rift phase) led to the development of the lower Buntsandstein Facies, bounded by two angular unconformities and subdivided into two depositional sequences (DS-1 and DS-2); the lower one is dominated by alluvial fans deposited in half-grabens and the upper one by sandy braided rivers in more symmetrical grabens. The second phase (thermal or flexural subsidence phase) led to the deposition of the uppermost Buntsanstein (Röt) and Muschelkalk Facies, mostly shallow marine carbonates, subdivided into two depositional sequences (DS-3 and DS-4) with well developed lowstand, transgressive and highstand systems tracts (LST, TST and HST) intervals. The criteria for separating systems tracts and the interplay of tectonics, eustatism and rate of sedimentation are discussed. DS-3 and DS-4 broadly correspond to 2.1 and 2.2 third order cycles,but their limits are about 3–4 m.y. younger; this may be explained by local tectonic factors.

Styles of extension in the Pannonian Basin

Structural interpretation of reflection seismic profiles reveals distinct modes of upper crustal extension in the Pannonian Basin. While some subbasins in the Pannonian Basin complex show little extension (planar rotational normal faults), others are characterized by large magnitude of extension (detachment faults, metamorphic core complexes). Gravitational collapse of the Intra-Carpathian domain, combined with subduction zone roll-back is thought to be the driving mechanism of the Neogene back-arc extension. The very heterogeneously distributed extension is accommodated by transfer faults, which bound regions characterized by different polarity, direction, or amount of extension. In cross section these transfer faults are characterized by flower structures, typical for strike-slip faults. Seismic stratigraphic interpretations indicate that the non-marine post-rift sedimentary fill of the Pannonian Basin can be described in terms of sequence stratigraphy. The exceptionally good seismic sequence resolution allows recognition of third-order and also fourth-order depositional sequences, which may reflect the interplay of tectonics and eustasy, and Milankovitch scale climatic variations, respectively.

Cretaceous Caribbean paleobiogeography: a comparison of the generic and species distributions of rudist bivalves in light of dispersal versus vicariance biogeography

A dynamic interplay of tectonics and eustasy controlled the development and distribution of Cretaceous carbonate platforms, and subsequently influenced patterns of gene flow among tropical reef-forming rudist bivalves of the Caribbean Province. Mediterranean faunas first entered the Caribbean during the Valanginian, via trans-Atlantic larval drift. Larval drift distance was exceeded during the mid-Cretaceous opening of the Atlantic, and resulted in isolation of rudist gene pools and an Albian burst of endemism, the first of two for the Cretaceous. Following a Cenomanian, Turonian and Coniacian diversity drop, Caribbean endemism climbed again during the Santonian, Campanian and Maastrichtian. This second explosion of endemism is attributed, in part, to vicariance biogeography as Caribbean terranes split and became isolated, and in part to biotic factors (competition, niche partitioning) as terranes collided when the Caribbean plate moved eastward from its Pacific Ocean origin. Paleobiogeographic maps were compiled per stage of the Cretaceous, with substage resolution for the critical Albian, Campanian and Maastrichtian. Data utilized were 58 genera and 214 species of rudist bivalves plotted on Recent mercator projections and on 119, 100, 95, and 80 million year plate tectonic reconstructions. Diversity trends and indices of similarity were analyzed in drawing paleobiogeographic divisions. Generic plots delineated regions of tropical carbonate sedimentation, the northern and southern limits of reef building, and fluctuations of this reef line through time. Generic plots also identified areas with the greatest generic diversity per stage, and defined the timing and regional extent of the postulated Supertethyan climate zone. Paleobiogeographic plots revealed that Tropical reef-building in the Caribbean Province was wholly north of the paleoequator - a major paleoclimatic dilemna. Species plots mimicked those of genera for the Valanginian, Barremian, Turonian, Coniacian, and Santonian, but provided important new details of the movements of terranes, dispersal pathways, and isolation of rudist gene pools for the Aptian, Albian, Cenomanian, Campanian and Maastrichtian. These detailed data, the first to combine Cretaceous Tropical paleontology with Caribbean tectonic reconstructions, provide a framework for testing rates, patterns, and causes of evolution among Tropical bivalves.

Submarine-fan development in the southern Chile Trench: A dynamic interplay of tectonics and sedimentation

Submarine fans are well developed in the southern Chile Trench, from 33°S to 41°S latitude. SeaMARC-II side-scan sonar and seismic reflection records image steep erosional escarpments, as much as 400 m in relief, extending seaward across the trench basin from the mouths of submarine canyons. The scarps bisect trench fans into paired lobes of contrasting morphology where gravity flows either follow or oppose the gradient of the axial trough. Fanlobes are depositional and constructional up-gradient (south) from the canyon mouths. They are composed of aggraded channel/levee complexes, smooth and conformable sediment drapes, and crescentic levees rimming the headwalls of erosional scarps. Fanlobes are carved and dissected by erosional processes down-gradient (north) from the canyon mouths. They exhibit amalgamated lag pavements, composite sediment lobes, longitudinal furrows, braided channels, and canyon-mouth bars. Thick, massive-to-laminated sand and gravel with abundant scour surfaces were sampled from the erosional fanlobes, whereas fine-grained turbidites with expanded hemipelagic intervals typify the depositional fanlobes. The texture and composition of the sediment supply, the onshore climate, and the tectonic perturbations of the axial gradient affect the morphologic development of trench fans. Stratigraphic intervals recording periods of intensified fan erosion and progradation of the axial channel are manifested by channeled, high-amplitude seismic facies: reflective lenticular bodies, truncation and scour surfaces, planar-amalgamation, and sigmoidaccretion structures. The severe erosional dissection of down-gradient fanlobes and the northerly encroachment of the axial channel are best developed in the surficial strata of the trench basin. Extensive sediment remobilization and efficient longitudinal transport sculpted the present fan surface and are correlated with the last glacial maximum. The trench fans may have been deposited on progressively steeper trench gradients, because the buoyant Chile Rise migrates northward as it subducts beneath the Andean continental margin. Fan distributary channels, axial channels, slump scars, and erosional gullies are largely localized along structural features. Normal faults propagate through the sedimentary cover and create elongate depressions on the sea floor that capture the high-velocity mainstreams of turbidity currents. Orthogonal fault sets within the deposits of the trench basin, which parallel the spreading and transform structures of the extinct Pacific-Farallon Rise and the Chile Rise, are evidently reactivated during subduction by flexure of the oceanic basement along the outer wall of the trench basin. Uplifted thrust ridges, generally restricted to a narrow zone along the base of the deformation front, are dissected by distributary channels, and channel courses are locally deflected seaward of these propagating structures. Transform-oriented basement ridges, associated with strike displacements of the axial channel and vertical faults in the trench basin, may accommodate renewed strike-slip motion as they enter the subduction zone and thereby influence the debouchment points of submarine canyons to the trench basin.

The Interplay of Tectonism and Eustasy in Controlling Carbonate Platform-to-Basin Deposition: Triassic of the Dolomites, Northern Italy: ABSTRACT

The Interplay of Tectonism and Eustasy in Controlling Carbonate Platform-to-Basin Deposition: Triassic of the Dolomites, Northern Italy: ABSTRACT

Timing, style and sedimentary evolution of Late Palaeozoic-Mesozoic extensional basins of East Greenland

Abstract The late Palaeozoic-Mesozoic sedimentary basins of East Greenland record a complex series of events which eventually led to the successful opening of the Norwegian-Greenland Sea in the late Palaeocene. Major tectonic events and regional sea-level changes caused by plate movements and reorganizations, overprinted by the effects of local tectonics and associated sea-level changes are reflected in thick, unconformity bounded sequences. Caledonian crustal shortening and thickening culminated in the Silurian, and was succeeded by extensional collapse, vulcanism and intrusion of post-tectonic granites in the Devonian. Large, transtensional pull-apart basins were formed and became filled with continental red beds. Basin margins underwent repeated episodes of thrusting. A change to rifting took place in the latest Devonian. Rapid subsidence and continental deposition punctuated by episodes of igneous activity and contractional deformation continued from the Devonian until early Permian times for about 120 Ma leaving a record of alluvial fan and flood plain siliciclastics alternating with rhyolitic and alkaline basaltic intrusions and extrusions. Later basin subsidence reflected thermal cooling and contraction following the prolonged late Palaeozoic period of crustal thinning. Important phases of block faulting occurred at several intervals during Mesozoic times climaxing in the Volgian-Valanginian interval. Cenozoic basin inversions resulted in dramatic decoupled uplift and tilting of large blocks. The degree of Devonian extensional collapse, the position and orientation of Caledonian thrust planes, and the localization of mid- and late Palaeozoic transtensional strike-slip basins exerted a profound control on localization and style of the compartmentalized Mesozoic rift. The importance of pre-Mesozoic history, timing of Mesozoic tectonic events and the interplay of tectonism, and rates of subsidence, sea-level change and sediment influx have close parallels in the North Sea area. Examples from the exposed Mesozoic succession of East Greenland may thus serve as excellent predictive guides for subsurface geology around the British Isles.

Interplay of tectonics and sea‐level changes in basin evolution: an example from the intracratonic Amadeus Basin, central Australia

Abstract The Amadeus Basin, a broad intracratonic depression (800 times 300 km) in central Australia, contains a complex Late Proterozoic to mid‐Palaeozoic depositional succession which locally reaches 14 km in thickness. The application of sequence stratigraphy to this succession has provided an effective framework in which to evaluate its evolution. Analysis of major depositional sequences shows that the Amadeus Basin evolved in three stages. Stage 1 began at about 900 Myr with extensional thinning of the crust and formation of half‐grabens. Thermal recovery following extension was well advanced when a second less intense crustal extension (stage 2) occurred towards the end of the Late Proterozoic. Stage 2 thermal recovery was followed by a major compressional event (stage 3) in which major southward‐directed thrust sheets caused progressive downward flexing of the northern margin of the basin, and sediment was shed from the thrust sheets into the downwarps forming a foreland basin. This event shortened the basin by 50–100 km and effectively concluded sedimentation.The two stages of crustal extension and thermal recovery produced large‐scale apparent sea‐level effects upon which eustatic sea‐level cycles are superimposed. Since the style of sedimentation and major sequence boundaries were controlled to a large degree by basin dynamics, depositional patterns within the Amadeus and associated basin are, to a large degree, predictable. This suggests that an understanding of major variables associated with basin dynamics and their relationship to depositional sequences may allow the development of generalized depositional models on a basinal scale.The Amadeus Basin is only one of a number of broad, shallow, intracratonic depressions that appeared on the Australian craton during the Late Proterozoic. The development of these basins almost certainly relates to the breakup of a Proterozoic supercontinent and in large part, basin dynamics appears to be tied to this global tectonic event. Onlap and apparent sea‐level curves derived from the sequence analysis appear to be composite curves resulting from both basin dynamics and eustatic sea‐level effects. It thus appears likely that sequence stratigraphy could be used as a basis for inter‐regional correlation; a possibility that has considerable significance in Archaean and Proterozoic basins.

The history of the great northwest European rivers during the past three million years

This paper is based on a review of the histories of the Rivers Elbe, Saale, Weser, Rhine, Meuse, Scheldt, Thames, Somme and Seine. Two further rivers no longer in existence, the Baltic and Channel rivers, are also included. The histories of these rivers illustrate how the interplay of tectonics and climate have influenced the northwest European drainage system through the late Cainozoic. The foundations of the modern drainage system were laid in the Miocene when earth movements associated with Alpine orogenesis and the opening of the North Atlantic were at their height. In general, these early rivers occupied shallow valleys and transported only chemically resistant minerals and lithologies. The Pleistocene was marked by the appearance of cold climates. These climates resulted in fluvial dissection of the landscape, which stripped first regolith, then fresh material derived by periglacial processes. This material accumulated in the river valleys as gravel and sand deposits, which make up the overwhelming bulk of Pleistocene fluvial sediments. The rivers generally adopted braided courses during cold stages. The deeply incised modern valley system has developed largely as a result of rapid climatic changes over the past 2.4 Ma or so. Throughout this period the river system has undergone repeated adjustments in response to continental glaciation. These responses are discussed. Particular attention is paid to the impact of the Anglian-Elsterian glaciation that blocked the southern North Sea to produce a vast ice-dammed lake, the overspill from which initiated the Dover Straits. By contrast, interglacial sedimentation comprises predominantly fine, often fossiliferous sediments with rivers normally adopting single-thread channels, while estuarine sediments were deposited in areas invaded by high eustatic sea levels. The impact of sea-level change on the length of rivers and their courses is considered.

Accumulation Rates of Biogenous Silica and Terrigenous Detritus in Late Miocene-Early Pliocene Santa Maria Basin, California: ABSTRACT

The upper-Miocene-lower Pliocene laminated to massive diatomaceous strata of the Santa Maria basin encompass portions of the Monterey and overlying conformable to nonconformable Sisquoc Formations and record the continued accumulation of admixed siliceous (mostly diatoms) and terrigenous (silt and clay) components in a Neogene borderland basin. Lithologies, which vary from diatomite to diatomaceous mudstone, are the result of fluctuations in slope-accumulating silica and terrigenous debris. Bulk accumulation rates, as well as silica and terrigenous component accumulation rates, were calculated for four measured sections using accurate stratal thicknesses, absolute ages, rock compositions, and bulk densities. Bulk accumulation rates range from less than 20 to greater than 70 mg/cm/sup 2//year and are comparable to bulk accumulation rates in the present-day Santa Barbara basin and Gulf o f California. Silica accumulation rates (20-30 mg/cm/sup 2//year) suggest that sedimentation took place beneath productive waters and they exceed those encountered in other high-productivity oceanic areas, such as the Bering Sea and Peruvian coastal waters. Relatively high terrigenous accumulation rates (18-35 mg/cm/sup 2//year) reflect the dilution of these high-productivity waters by continentally derived detritus. Comparison of calculated accumulation rates with rates determined for similarly aged strata of the Santa Barbara basin reveals that silica and terrigenousmore » debris were accumulating at higher rates within the Santa Maria basin. These differences are due to the complex interplay of tectonics and oceanographics and to the proximity of the basins relative to the strandline.« less

Shelf Break on Modern Passive Margins: Structure, Sedimentation, and Progradation: ABSTRACT

The time-integrated structural-stratigraphic configuration of the shelf-to-slope break of many modern margins records the interplay of tectonics, submarine erosion and/or depositional processes. A simple process-response model may be used to help interpret the variations of shelf-break configuration and progradational patterns of passive continental shelves. The key factors are (a) the amount and nature of the sedimentary flux (F) provided to and across the shelf, and (b) the depth at which particles come to rest (H), which is largely a function of the local hydrodynamic and boundary layer conditions and of the grain size and density of the particles being transported. By maintaining factors F and H as constants, we can evaluate the role of structural displacement and imp rtance of the relative position of the shelf surface to sea level in the development of the shelf-to-slope configuration. In places where a shelf subsides, or when there is a demonstrable eustatic rise while an ample sediment supply is provided, a sediment layer may accumulate over much of the shelf; excess seaward-transported sediment will accumulate at and beyond the shelf break. If a shelf remains relatively stable or if there is an appreciable eustatic drop in sea level, much of the sediment can bypass the shelf and will accumulate beyond the shelf break, on the slope, rise, and abyssal plain. As equilibrium is attained, we can expect that D (shelf depth) H on a continental slope. Thus, in this example, H becomes coincident with the depth at the shelf break. The model is tested at shelf-slope interfaces on the Tuscany and Ligurian margins in the western Mediterranean, and on the Iberian margin in the eastern Atlantic. Seismic profiles indicate that the structural-stratigraphic configuration and progradational patterns at shelf breaks observed on subbottom profiles are variable. We correlate this variability with age and tectonic development of a margin, and thus with the successive structural stages through which a passive margin evolves. End_of_Article - Last_Page 904------------

Recognition of Shelf-Slope Break Along Tectonically Active, Ancient Continental Margins: ABSTRACT

End_Page 939------------------------------Tectonically active continental margins include transform, protoceanic-rift, and subduction settings. Shelf-slope breaks in these settings tend to be transient in time and space. Wrench and fault-block systems feature irregularly shaped basins and uplifts that have abrupt vertical movements and facies changes. Subduction systems form elongate basins and ridges in response to the interplay of tectonics and sedimentation. Because of the nondepositional character of narrow, tectonically controlled shelves, shelf-slope breaks commonly are expressed as unconformities separating shallow-marine/nonmarine and slope/basinal deposits. Alternatively, shelf and basinal deposits may be separated by a biostratigraphically compressed interval, including glauconite and phosphorite, which represents the clastic-starved shelf-slope break. Subtly expressed shelf-slope break deposits of active margins commonly are masked by abrupt sedimentation in adjoining areas along with abrupt facies migration. Consequently, bracketing deeper and shallower marine facies is the usual key to locating ancient shelf-slope breaks. Basinal facies are distinctive in many wrench and fault-block systems, with two common sedimentary motifs: (1) ponded submarine-fan deposits displaying little proximal-to-distal facies segregation, and (2) clastic-starved sections of laminated (commonly biogenous) sediment reflecting anoxic conditions in isolated silled basins. These facies, together with slump-dominated slope facies, adjoin shelf-slope break deposits. Variable geometries characterize subduction-controlled shelf-slope breaks, but generally, ancient deposits overlie highly deformed, deep-marine components (trench-slope and trench sediments) and are overlain by relatively undeformed fore-arc deposits. Underlying deposits may have exotic sources and may contain recycled materials. Overlying deposits consist of predominantly land-derived components. End_of_Article - Last_Page 940------------

Les « coteaux rhodaniens » de Vienne à Tournon : essai de typologie géographique de l'aménagement

An attentive geographical survey of the rather steep hills constituting the eastern facade of the French Central Massif from Vienne to Tournon overhanging the corridor valley of the Rhône tends to show that slope steepness is essentially due to the tectonic interplay and to the deepness of the hydrographie network of the Rhone's right bank. The frequent use of terraced parcels which nowadays have been more or less abandoned is accounted for by the steepness of the hillsides. Hence the aim of this paper is to offer a comprehensive morpho-anthropic classification of the hills comprising hillsides and precipitous gorges which were never worked upon, terraced hillsides either halfcultivated or completely cultivated, hillsides being urbanized or progressively destroyed (quarries, motorways cutlings). Thus it is suggested that an effort should be made to preserve these terraced hillsides for this country-side, resulting from past toil, constitutes a valuable element of our regional and national patrimony.

Generation, Migration, and Entrapment of Petroleum in Extensional Basins: ABSTRACT

The interplay of tectonics, thermal regime, and depositional history generally determines the petroleum potential of individual basins. The application of these factors to a review of several extensional basin systems (Rhine graben, North Sea basin, Reconcavo basin, Gulf of Suez basin, Red Sea basin, Bass basin, and Gippsland basin) provides the basis for this analysis. Extensional tectonic systems provide a mechanism for thinning the crust and upper mantle (the lithosphere). The result is a progressive rift-basin evolution starting with graben formation and ending in the development of continental margins. However, if tensional stress stops at any stage, a post-rift phase of subsidence, regulated by thermal decay, begins. Sedimentary rocks deposited prior to extension (pre-rift sediments) are preserved in the graben areas but eroded from the horsts. Rift sediments (usually clastics) deposited during extension are eroded from the uplifted areas, but carbonate rocks and evaporites may be deposited if the climatic environment is favorable. Sediment deposition is continued after extension stops (post-rift sediments). Source beds can be in the pre-rift, rift, or post-rift sediments but generation does not occur until they are buried to the depth of the generative window. Generation is aided by the high heat flow caused by the thinned crust. The kind of petroleum generated is dependent on the type of organic material present and the deepest zone of generation reached. Extensive normal faults contribute to trap geometry but inhibit long distance migration. Consequently, except in the post-rift section, entrapment of petroleum requires that the source and reservoir rocks are in close proximity, which can be accomplished by faulting, interfingering, or the superposition of source rocks on reservoir rocks at unconformities. The most favorable conditions for generating and trapping large oil fields are commonly in or near the deepest part of the basin. End_of_Article - Last_Page 779------------

Clastic sediments associated with radiolarites (Tauglboden—Schichten, Upper Jurassic, Eastern Alps)

ABSTRACTDuring the early Upper Jurassic, widespread deep‐sea radiolarites were deposited in most parts of the Northern Limestone Alps. In the formation described (Tauglboden‐Schichten), these pelagic sediments interfinger with local‐source clastic material. Depending on the topography and the kind of material, either slides and slumps, mudflows, grain flows or turbidity currents operated and formed slump‐folded beds, mud‐flow breccias, fluxoturbidites or turbidites.A breccia had been traced over an area of 20 km2. Its variation is described in terms of lithological columns, bed thicknesses, maximum grain sizes and grain orientations. It forms a tongue‐shaped body, which was probably a part of a submarine fan. The fluxoturbidites of the proximal area grade distally on three sides into turbidites within 3–5 km.The clastic material consists of marls and limestones of Rhaetian and Jurassic age. It was probably derived from a tectonically uplifted palaeo‐high by an interplay of tectonics and gravity. The clastics were deposited on submarine fans bordering this high.In its lithology the formation closely resembles certain marginal facies of flysch troughs.