Epeirogenic Movements Research Articles

Geometry of sedimentary deposits and evolution of the landforms in the Chobe Enclave, Northern Botswana

The imprint of neotectonics is frequently obscured in low-relief environments by the sedimentary cover. This is the case in the Chobe Enclave, part of a pristine region of the Middle Kalahari Basin in northern Botswana, where numerous fossil landforms, such as sand dunes, pans, sand ridges, and carbonate islands, can be observed but whose detailed origins are unclear. In this study, a combination of near-surface geophysical surveys, sedimentological analysis, and optically-stimulated luminescence (OSL) dating were used to study the relationship between landscape development and neotectonic activity in one region of the Chobe Enclave. Specifically, electrical resistivity tomography (ERT) and ground penetrating radar (GPR) surveys were used to define the lateral and vertical distribution of sedimentary deposits associated with a prominent sand ridge and its margins. Sedimentological analysis and OSL dating of soil samples from pits taken along the survey lines were then used to calibrate the geophysical results and establish a chronostratigraphical framework. Our results lead to the following hypotheses regarding the evolution of this part of the Chobe landscape: (i) during the Late Pleistocene (>~25 ka), fluvial channels were buried due to epeirogenic movements, resulting in paleo-channels; (ii) between ~25 ka and ~6 ka, a paleo-lake shoreline formed, which resulted in the linear eastern margin observed on the considered sand ridge. Erosional bounding surfaces suggest the syndepositional uplift of the sand ridge morphologies during this time; (iii) a neotectonic influence on the evolution of the landscape is revealed by the incision of the sand ridge forming fluvial watergaps since ~6 ka ago; and (iv) due to continuous aeolian and fluvial reworking, the western-most ridge became gradually isolated from the floodplain resulting in an inherited relief. In conclusion, this investigation allowed the deformation caused by epeirogenic movements acting on a low relief landscape to be characterized in terms of landforms and sedimentary body properties.

Late Paleozoic-Early Mesozoic paleotectonics of the northern Arabian Plate (SE Turkey) and its role in the Paleozoic petroleum system

The Carboniferous compressional deformation of the Arabian Plate has been causally linked with the Hercynian orogeny. However, this epeirogenic movement occurred far from the Arabian plate. Instead, the Gondwana-directed subduction of the Paleo-Tethys oceanic crust may be the controlling factor of the Carboniferous structural development of southeast Turkey (the northern Arabian Plate). The tectonic activity resulted in uplift and widespread erosion of a large area and produced granitic intrusions, metamorphism, folding, and faulting. The compressional event was intermitted by theback-arc spreading of the Neo-Tethys Ocean (Middle Permian-Triassic) that occurred because of the detachment of the Cimmerian supercontinent from the Gondwana margin. The spreading of the Neo-Tethys caused the Arabian Plate to be subjected to extensional tectonism. The tectonic overprints of these epeirogenic events on the structural fabric of southeast Turkey have not been studied in detail. Innovations in subsurface imaging techniques, wireline logs, and sufficient-quality data enable the depiction of the traces of the Carboniferous compression and the subsequent Permian–Triassic regional extension. This study explores the structural remnants of the Carboniferous compression and the Permian–Triassic extension in southeast Turkey and their impact on the Paleozoic petroleum system. In conclusion, the Carboniferous, SW- and EW-oriented compressional forces led to major uplift, inversion, and substantive erosion in southeast Turkey. The regional uplift confined the Silurian-sourced oil exploration activities to a narrower area due to the denudation of the Silurian units towards the Carboniferous Arches. Subsequently, the opening of the Neo-Tethys yielded en-echelon NW and WNW-trending horsts and grabens bounded on both sides by normal faults, resulting in the northeastward thickening of the syn-rift units. The horst structures allow hydrocarbon accumulation in the Ordovician Bedinan Formation sandstones tectonically juxtaposed with the Silurian source rock.

TECTONO-STRATIGRAPHIC COMPLEXES AS THE LARGEST UNITS IN THE PALEOPROTEROZOIC OF THE UKRAINIAN SHIELD

The main problems of stratigraphic taxonomy and no menclature of Paleoproterozoic metamorphic formations of the Ukrainian Shield are characterized by the example of the Kryvyi Rih (Kryvyi Rih-Kremenchuk), Ingulets (W-Ingulets) and Ingul structural-formation zones. In addition to the existing stratigraphic units of regional rank — series — the relevance of identifying supra-regional tectono-stratigraphic structural-material complexes, which have cardinal differences in geotectonic and paleogeographic conditions of formation and formational paragenesis, is shown. The most general features of the evolution of sedimentary lithogenesis in the Paleoproterozoic of the Ukrainian Shield are shown in terms of identifying two tectono-stratigraphic structural-material complexes of supra-regional rank: 1) Krivorozhsky (subplatform with a relatively poorly differentiated type of epeirogenic movements, subhumid, ma - ture — with a high level of chemical weathering, characterized by close paragenesis of five formational types of sedi - ments — monoquartz and oligomictic metapsephopsammites ↔ high-aluminous metaaleuropelites ↔ aluminous carbonaceous metaaleuropelites ↔ terrigenous-carbonaceous shales and metadolomites ↔ ferruginous quartzites and shales; 2) Ingulsky or Ingulsko-Gleyevatsky (tectonically active, resembling Phanerozoic myogeosynclinal or marine trough complexes, subarid, immature — with a low level of chemical weathering, carbonate-terrigenous metaflichoid subgrawacke). Typomorphic features of the structure and formational content of the identified complexes are considered and their correlation with similar complexes on other shields is indicated; attention is drawn to their correspon - dence to the stratigraphic rank of “Supergroups”.

Paleozoic sequence stratigraphy, depositional systems, and hydrocarbon habitats across the Arabian plate

The Paleozoic sedimentary section of the Arabian plate recorded the effects of numerous fluctuations in sea level and gentle epeirogenic movements. Eustatic changes in sea level over the Arabian plate resulted in transgressions and regressions and created many local and regional unconformity surfaces, identified by missing section and nondeposition. The distant deformation of the Caledonian tectonic orogeny and mountain building of the North Atlantic region, and the later Hercynian tectonic event, are partially responsible for eustatic sea-level changes. Additionally, detailed evidence of Paleozoic glacial erosion and glacial eustasy in the regressive sedimentary section over uplifted paleohighs comes from deep wells penetrating local exotic tectonic blocks. The resulting surfaces mark the sea-level falls associated with the glacial events in the Ordovician, Late Devonian, and Carboniferous–early Permian sediments. The depositional settings of the Cambrian–upper Permian rocks include deltaic and glacial settings and are expressed as alluvial–fluvial fans that grade into braided plains and shallow-marine carbonates flanked by distal shales. Late Permian sediment fill accompanied the development of widespread accommodation, resulting from a major sea-level rise, coinciding with a major period of carbonate–evaporite deposition, in which clastic sediments were only a minor factor. The regional sedimentary facies have good reservoir quality and are juxtaposed to regional source rocks and seals associated with both structural and minor stratigraphic traps. Production occurs in Precambrian through Permian strata in which mature clastic and shallow-water carbonate reservoirs occur, commonly sealed by shales, and sourced by Silurian hot shales or older source rocks in the section.

On the observability of epeirogenic movement in current and future gravity missions

Next generation gravity missions are expected to improve the accuracy of temporal gravity models significantly. The periodic signals and trends retrieved by these missions are induced by mass redistribution in the Earth system, carrying essential information on dynamic processes in the atmosphere, cryosphere, continental hydrosphere, the oceans and the solid Earth. While temporal gravity signals induced by deep Earth's processes are commonly thought to lie below the observational threshold of satellite gravity missions, as one assumes them to be small in amplitude and restricted to the longest spatial and temporal scales, there exists evidence from the geologic record for rapid uplift and subsidence events at regional scales, especially along passive continental margins, related to flow in the underlying mantle. Here we explore novel mantle flow retrodictions for geodynamically plausible, compressible, high resolution Earth models with ≈670 million finite elements. These time-dependent Earth models link to geologic observables in the late Paleogene that can be tested independently, while at the same time indicating mantle flow induced geoid rates on the order of 5μm/year, at spatial scales of 1000km. We assess the signal retrievability of the modeled rates in closed-loop numerical simulations, with different satellite gravity retrieval mission assumptions, including GRACE, GRACE-FO and a next generation gravity mission. We find the modeled deep Earth signal to be on the edge of detectability, but coming into the range of detectability in future temporal gravity field solutions, suggesting the use of satellite gravity data to validate geodynamic Earth models. Importantly, the application of forward modeled dynamic mantle signals seems to be essential for improved de-aliasing and signal separation in future gravity missions.

Source Rock Evaluation in The Lake Chad Area of the Bornu Basin, Nigeria

Source rock evaluation of the Lake Chad area of the Bornu Basin which contains a comparatively thicker sedimentary succession based on interpreted seismic and gravity data was undertaken in this study. A total of twenty-nine shale samples from three wells (Kutchali-1, Faltu-1 and Herwa-1) were analysed to arrive at the bulk geochemical properties, organic matter particles and vitrinite reflectance (VR) data of the strata penetrated by the wells. The Lake Chad area appears to contain the main ingredients required to make a rich source rock with over 96% of the total organic carbon (TOC) values being in the range of 0.63-2.88 wt% and over 95% having Tmax greater than 435°C in most of the sampled intervals. The variation of Tmax and VR with depth in the wells reveals irregular decreases or subtle decreasing trends that are suggestive of cooling in the basin’s thermal history probably as a result of uplift and erosion. The uplift could have been caused by epeirogenic movement or by folding related to the Santonian inversion witnessed by the West African Rift Subsystem. In terms of hydrocarbon generation potential, most of the samples have HI values greater than 50 mgHC/g TOC, but generally less than 200 mgHC/g TOC. These HI values suggest dominance of Type III with less Type II Kerogen; thus, a predominantly predominantly gas prone area. A study of some bulk geochemical parameters (TOC, Tmax and HI) of the three study wells has revealed that the succession penetrated by one of them (Faltu-1 well) contains several potential gas source intervals and two potential oil source intervals with the latter probably lying between 2500 m and 3000 m depth.

GEOMORPHOLOGICAL LEGACY OF THE OUTSTANDING RUSSIAN NATURALIST B.L. LICHKOV (1888–1966)

Boris Lichkov, an outstanding scientist of the first half of the XXth century, worked successfully on a number of basic problems of Earth sciences, such as origin and evolution of deserts, epeirogenic crustal movements correlation of marine and alluvial terraces in the context of the Black Sea formation, geochronology of continental nuclea, such as the “ancient crown of Asia” by E. Suess (Baikalian orogen of Southern Siberia), glaciations and formation of great alluvial plains

Integrated application of geoelectrical techniques for structural investigations: case study of Wadi Marsad Graben, Jordan

An integrated geoelectrical survey has been conducted at the Wadi Marsad area, south of Jordan, to map the dominant structural features associated with the Arabian-African plate movements. The area is known to be tectonically affected by the epeirogenic movements of the Arabian shield which originated several major and minor structural features. Fifty-four vertical electrical soundings (VES) using Schlumberger configuration and nine induced polarization (IP) profiles (both resistivity and metal factor parameters were determined) were carried out in the investigated area. The integrated use of IP and VES surveys has proved to be efficient in mapping the lateral and vertical extensions of a major graben structure existing in the investigated area.

Interactions between fluvial and eolian geomorphic systems and processes: Examples from the Sahara and Australia

The remains of once integrated drainage systems are still discernible in many of the hot deserts of the world. Some of these date back to the Mesozoic, as in arid Western Australia, where they now form chains of salt lakes. Others were active in Miocene times, such as the Sahabi Rivers that once flowed from Chad to the Mediterranean. A few remained active during Quaternary interglacials, as in the Sahara. All contributed sediments that were reworked by wind during drier phases to form desert dunes. The desert dunes of Australia and of the 9500km long chain of deserts extending from the Sahara through Arabia to the Thar desert of India originated from sediments eroded from the uplands and deposited in closed interior basins formed during the course of Late Mesozoic and Cenozoic faulting, rifting and epeirogenic movements. It was the unconsolidated Neogene sediments laid down in large subsiding sedimentary basins such as the Kufra-Sirte basin in Libya and the Chad basin which provided the source material for the Late Pliocene and Quaternary desert dunes of the Sahara. One effect of the progressive build up of high latitude ice sheets during the Neogene was to steepen the temperature and pressure gradients between the equator and the poles, resulting in increased Trade Wind velocities. Stronger winds were better able to mobilize the alluvial sands of the increasingly dry Sahara and adjacent deserts and to fashion them into desert dunes.A more subtle form of interaction between eolian and fluvial processes concerns the interplay between desert dust (loess) accumulation on hill slopes in arid regions and the onset of fine-grained valley-fill accumulation by sluggish, low energy streams in mountain valleys. Some of these Late Pleistocene wetlands served as refuge areas for plants, reptiles and invertebrates at a time when the surrounding desert plains were very cold and dry, as in the Flinders Ranges of South Australia. In the arid Flinders Ranges such valley-fills were built up between 35kyr and 15kyr ago, after which the return of the summer monsoon led to stream channel incision and the formation of a network of gullies, often erroneously attributed to human activities. Understanding the causes of such accelerated erosion can prevent unnecessary and expensive attempts at restoration, since the latter are based on the incorrect assumption that overgrazing and present-day land use are responsible.

Lithofacies zoning and titanium-zirconium potential of the Mansi and North Sos’va areas, Transural placer region

The lithofacies and morphostructural analyses of the Mansi and North Sos’va areas of the Transural placer region allowed us to establish factors of the spatial and lithostratigraphic control of titanium-zirconium placer potential. It was established that the placers are localized in sediments of the upper stage of the Oligocene-Miocene complex and rocks of Oligocene basin shows facies zoning. The most promising are the paleolittoral and shoal facies formed under moderate hydrodynamic activity. In tectonic aspect, the position of promising areas and their lithofacies composition are controlled by flank zones of local domes that experienced epeirogenic movements. Regressive regime in the Oligocene basin suggests the highest probability for the discovery of titanium-zirconium placers of the littoral type in inner zones of neotectonic domes.

Sequence stratigraphy of Lower Cretaceous deposit on the eastern Russian Plate

The generalized eustatic and tectonoeustatic models developed by the author are tested on Lower Cretaceous deposits of the eastern part of the Russian Plate. The models are applicable to facies analysis of sections of epicontinental basins with mainly slope sedimentation. They demonstrate possible variations in section lithology depending on the rate of eustatic changes and the intensity and direction of epeirogenic movements. It has been revealed that the Lower Cretaceous sections in the east of the Russian Platform formed as a result of the synchronous global eustasy and regional epeirogeny. Superposition of the global eustatic curve onto the Lower Cretaceous chronostratigraphic chart of the eastern part of the platform showed that global eustasy, periodically concealed by regional epeirogeny, played a crucial role in the Early Cretaceous history of the study area. Regional epeirogenic and eustatic curves were constructed. The epeirogenic curve demonstrates the contribution of vertical tectonic movements to the overall eustatic-epeirogenic result recorded on a regional eustatic curve. The latter was constructed from the analysis of the spatial and temporal changes in the stratigraphic position of formations and strata and transgressive surfaces ranking. Eustatic cycles of different ranks, from elementary (systems tracts) to regional scale, have been recognized. In the rank of largest lithostratigraphic units, three sequences are revealed: Valanginian (RP-1K), Upper Hauterivian–Upper Aptian (RP-2K), and Albian (RP-3K), which reflect the crucial stages of the Early Cretaceous evolution of the eastern Russian Plate. The eustatic-epeirogenic processes during accumulation of formations and strata from Early Berriasian to Late Albian (145.5–99.6 Ma) are considered. It is shown that the division of the studied composite section into sequences permits precise prediction of diverse solid minerals.

Variable Phanerozoic thermal history in the Southern Canadian Shield: Evidence from an apatite fission track profile at the Underground Research Laboratory (URL), Manitoba

Analysis of a 1.15 km deep apatite fission track (AFT) thermochronology profile at the Underground Research Laboratory (URL), in the southwestern Canadian Shield suggests two Phanerozoic heating and cooling episodes indicating significant, previously unsuspected, Phanerozoic heat flow variations. Phanerozoic temperature and heat flow variations are temporally associated with burial and erosion of the Precambrian crystalline shield and its overlying Phanerozoic successions, which are now eroded completely. Maximum Phanerozoic temperatures occurred in the late Paleozoic when the geothermal gradient is estimated to have been ~ 40–50 °C/km (compared to a present day gradient of ~ 14 ± 2 °C/km) and the sedimentary cover was ~ 800–1100 m thick. Our thermal history models, confirm regional stratigraphic relationships that suggest that the Paleozoic succession was completely eroded prior to beginning of Mesozoic sedimentation. A second heating phase occurred during Late Cretaceous–Paleogene burial when the geothermal gradient is estimated to have been ~ 20–25 °C/km and the Mesozoic and Cenozoic succession was ~ 1200 to 1400 m thick. The Phanerozoic thermal history at the URL site shows a pattern similar to that inferred previously for the epicratonic Williston Basin, the centre of which lies several 100 km to the west. This implies a common regional thermal history for cratonic rocks underlying both the basin and the currently exposed shield. It is suggested that the morphotectonic differences between the Williston Basin and the exposed shield at the URL are due to a dissimilar thermomechanical response to a common, but more complicated than previously inferred, Phanerozoic geodynamic history. The two Phanerozoic periods of variations in geothermal gradient (heat flow) were coeval with epeirogenic movements related to the deposition and erosion of sediments. These paleogeodynamic variations are tentatively attributed to far-field effects of orogenic processes occurring at the plate margin (i.e. the Antler and the Cordilleran orogenies) and the associated accumulation of cratonic seaway sedimentary sequences (Kaskaskia and Zuni sequences).

Tectonics versus eustatic control on supersequences of the Zagros Mountains of Iran

At least 12 km of strata ranging in age from the latest Precambrian to the Recent are exposed in the Zagros Mountains of Iran. This sedimentary cover is characterized by distinct stratal packages separated by major unconformities forming twelve supersequences. They are informally named as: (1) Late Precambrian – Cambrian Hakhamanesh Supersequence, (2) Ordovician Kourosh Supersequence, (3) Silurian Camboojiyeh Supersequence, (4) Devonian Darioush Supersequence, (5) Mississippian – Pennsylvanian Khashayar Supersequence, (6) Permian – Triassic Ashk Supersequence, (7) Jurassic Farhad Supersequence, (8) Early Cretaceous Mehrdad Supersequence, (9) Late Cretaceous Ardavan Supersequence, (10) Paleocene – Oligocene Sassan Supersequence, (11) Oligocene – Miocene Ardeshir Supersequence, and (12) Miocene – Pleistocene Shapour Supersequence. These supersequences and their correlatives in neighboring areas have been used to infer tectonic events. The dominant interpretation has been that local or regional epeirogenic movements were responsible for the formation of these supersequences. Unconformities are considered as indications that epeirogenic movements associated with tectonic events affected the area. The present investigation provides an alternative to the established view of the Phanerozoic supersequences of the Zagros Mountains. A good correlation exists between the lithofacies of supersequences in the Zagros Mountains and the second-order eustatic sea-level changes. Deposition of deep-water, marine shales occurred during periods of eustatic sea-level rise. Platform-wide unconformities coincided with eustatic sea-level lows. In fact, supersequences of the Zagros Mountains are nearly identical to those described from the North American Craton and the Russian Platform suggesting that these stratal packages are global. These observations suggest that supersequences of the Zagros Mountains formed by second order eustatic sea-level changes and not by local or regional epeirogenic movements. Although tectonic events did not produce supersequences of the Zagros Mountains, they influenced regional lithofacies patterns through the formation of intrashelf depressions such as the Hormoz Salt Basin during the Precambrian and the Dezful Embayment and the Lorestan Basin during the Mesozoic. Tectonic events also affected sedimentation during the Tertiary collision of Arabia and the Central Iran microplate through uplift, erosion, and the formation of the Zagros Foreland Basin. The results of this investigation necessitate a re-evaluation of the role and the significance of pre-Tertiary tectonic events commonly used to interpret the geological evolution of the Zagros Mountains.

Long-term tropical morphogenesis of New Caledonia (Southwest Pacific): Importance of positive epeirogeny and climate change

Extensive mapping of relict lateritic landsurfaces over the 1600 m of relief of mainland New Caledonia is used to evaluate long-term morphogenesis of the island since its emergence in the Oligocene. The results support the interpretation of the lateritic levels as abandoned, stepped remnant landsurfaces that may be grouped into eight island-scale erosion levels recording episodic lowering of base level. The separation of the erosion levels results from the combination of positive epeirogenic movements of the New Caledonia continental ridge and long-term Neogene climate variability, which is recorded by the contrasted erosion and weathering patterns of the three youngest levels and tentatively correlated with known global and regional paleoclimatic events.

Edge tectonics (trench rollback, terrane export) of Gondwanaland-Pangea synchronized by supercontinental heat

From 650–500 Ma assembly, 320 Ma merger in Pangea, to 185 Ma breakup, Gondwanaland developed by the accretion of lithosphere along the convergent edge on the south and by the export of terranes from the divergent edges on the west and northeast. The interior underwent epeirogenic movement except in areas affected during the merger by farfield shortening. Synchronous or near-synchronous events on the edges and interior are linked hypothetically by convection currents in the asthenosphere driven by supercontinent-induced heat. On the convergent edge, currents countered the sinking slab to roll back the trench and generate a backarc basin. On the divergent edge, currents initiated an ocean that prised off continental rims in the form of terranes. In the interior, currents extended the lithosphere in basins and rifts.

Episodic Cenozoic tectonism and the development of the NW European ‘passive’ continental margin

The North Atlantic margins are archetypally passive, yet they have experienced post-rift vertical movements of up to kilometre scale. The Cenozoic history of such movements along the NW European margin, from Ireland to mid-Norway, is examined by integrating published analyses of uplift and subsidence with higher resolution tectono-stratigraphic indicators of relative movements (including results from the STRATAGEM project). Three episodes of epeirogenic movement are identified, in the early, mid- and late Cenozoic, distinct from at least one phase of compressive tectonism. Two forms of epeirogenic movement are recognised, referred to as tilting (coeval subsidence and uplift, rotations <1° over distances of 100s of Kilometres) and sagging (strongly differential subsidence, rotations up to 4° over distances <100 km). Each epeirogenic episode involved relatively rapid (<10 Ma) km-scale tectonic movements that drove major changes in patterns of sedimentation to find expression in regional unconformity-bounded stratigraphic units. Early Cenozoic tilting (late Paleocene to early Eocene, c. 60–50 Ma) caused the basinward progradation of shelf-slope wedges from elongate uplifts along the inner continental margin and from offshore highs. Mid-Cenozoic sagging (late Eocene to early Oligocene, c. 35–25 Ma) ended wedge progradation and caused the onset of contourite deposition in deep-water basins. Late Cenozoic tilting (early Pliocene to present, <4±0.5 Ma) again caused the basinward progradation of shelf-slope wedges, from uplifts along the inner margin (including broad dome-like features) and from offshore highs. The early, mid- and late Cenozoic epeirogenic episodes coincided with Atlantic plate reorganisations, but the observed km-scale tectonic movements are too large to be accounted for as flexural deflections due to intra-plate stress variations. Mantle–lithosphere interactions are implied, but the succession of epeirogenic episodes, of differing form, are difficult to reconcile with the various syn-to post-rift mechanisms of permanent and/or transient movements proposed in the hypothetical context of a plume beneath Iceland. The epeirogenic movements can be explained as dynamic topographic responses to changing forms of small-scale convective flow in the upper mantle: tilting as coeval upwelling and downwelling above an edge-driven convection cell, sagging as a loss of dynamic support above a former upwelling. The inferred Cenozoic succession of epeirogenic tilting, sagging and tilting is proposed to record the episodic evolution of upper mantle convection during ocean opening, a process that may also be the underlying cause of plate reorganisations. The postulated episodes of flow reorganisation in the NE Atlantic region have testable implications for epeirogenic movements along the adjacent oceanic spreading ridge and conjugate continental margin, as well as on other Atlantic-type ‘passive’ margins.

Late Ordovician-early Silurian paleogeography of the Algerian Sahara

Late Ordovician-early Silurian paleogeography of the Algerian Sahara

Stratigraphy and sedimentology of the lower Neales River, West Lake Eyre, Central Australia: from Palaeocene to Holocene

The stratigraphy of the lower Neales River to the west of Lake Eyre, Australia's largest internal drainage system, preserves a detailed record of fluvial, lacustrine and aeolian deposits of early Tertiary to Holocene age. This stratigraphic framework provides a summary of the region's Cainozoic sedimentary units. Three units have been identified: an early Tertiary fluvial unit; a mid-Tertiary lacustrine unit; and a Quaternary unit composed of interbedded fluvial, lacustrine, and aeolian facies. Dramatic changes in depositional styles within, and between, these three major groups of sediments reflect the basin's response to changes in climate and sediment supply. Fluvial facies include perennial multi-channel, single-channel, and ephemeral river sequences. Lacustrine and deltaic facies reflect continuous fine-grained sedimentation during periods of high water-tables. The aeolian facies are evidence of aridity and sediment deflation in the basin. The early Tertiary fluvial unit is the result of Late Palaeocene–Eocene epeirogenic movements. A dramatic shift in facies to the mid-Tertiary lacustrine unit reflects a significant change in the basins climatic controls. Quaternary sediments reflect major changes in fluvial discharge regimes which may reflect major climatic and associated hydrological changes during past interglacial and glacial cycles.

The transformation of southern Israel from a swell to a basin: stratigraphic and geodynamic implications for intracontinental tectonics

The history of southern Israel during the ∼100 Myr period between the Cretaceous and the Eocene is an example of epeirogenic movements which were controlled by magmatism and heating. Initially this region was uplifted and became a local swell; then it subsided more than its surroundings and became a local basin. This study analyzes the subsidence history of the region during its cooling for two purposes: first, to understand the relations between the tectonic pattern of subsidence and the resulting stratal geometry, and second, to constrain the volume of magmatism that intruded the lithosphere and perturbed the isostatic equilibrium. Our results show that lateral changes in the intensity of the tectonically-driven subsidence are not always expressed by simple corresponding changes in the thickness of sedimentary units. The most prominent example of this was found in the Cenomanian section, which thickens northward in absolute contrast with the tectonic pattern of subsidence during its deposition. The reason for this discrepancy lies in lateral differences in the compactibility of the substrate upon which these sediments were deposited. The two most important factors controlling the compactibility of the substrate are the thickness of previously existing sediments and their history of uplift. Since sediments that are reburied after an uplifting phase do not compact significantly until they reach their previous maximal depth, we emphasize the need to reveal the amount of exhumation from the amount of erosion hidden in unconformities. Our second aim was achieved only in part because we cannot distinguish the subsidence caused by midlithospheric intrusions from secondary factors. One possible scenario that satisfies the observations is a combination of midlithospheric intrusions equivalent to a 15-km-thick sill, plus thermal thinning of the lithosphere of the same order.

Plan miocène et épandages siliceux {cf. rañas) au pied des Monts Ibériques Occidentaux/Miocene planation surface and siliceous deposits on the piedmonts of the Western Iberian Ranges

Abstract This paper links two events which seem very different : the Miocene planation surface and deposits (the Spanish "raňas "). We demonstrate the Vallesian erosion induces a thick weathering and a correlative accumulation of carbonates in the endoreic basins. During upper Miocene, the aridification and the beginning of epeirogenic movements releases the scouring of alterated materials and their deposits on the piedmonts. Here, the dating of "raňas " is not "villafranchian ", as it was estimated before. Indeed, the surface of these detrital deposits was bleached during the wet Pliocene : we find drifts coming from the upper white sands in the well-dated layers of Villarroya (-2,5 MA).