Differential Tectonic Movements Research Articles

The Roman Eifel Aqueduct: archaeoseismological evidence for neotectonic movement at the transition of the Eifel to the Lower Rhine Embayment

The Lower Rhine Embayment and adjacent areas are characterised by neotectonic deformation resulting in differential crustal movement. Slip rates along the fault systems are very low (< 0.1 mm/a). Significant earthquakes are known to have occurred in the past but the faulting behaviour is not adequately known which hampers the risks assessment. We analysed the archaeological record of the largest Roman aqueduct north of the Alps. This so called Eifel Aqueduct is 95.4 km long, has its source in the Eifel mountains and supplied the ancient city of Cologne with calcareous fresh water. The aqueduct crosses major faults of the Lower Rhine Embayment perpendicular. Analyses of the aqueduct´s gradient gives weak evidence for creep along the Kirspenich Fault resulting in differential movement of hanging and foot wall in the order of a few centimetres. Vertical offsets of 15 and 35 cm are documented exactly where the aqueduct crosses the Holzheim Fault system close to the city of Mechernich. Here, also structural damage of the aqueduct is recorded and archaeological evidence exists for repair works on the aqueduct. We interpret these observations as well as the construction of a 4 km long deviation as necessary measures to keep the aqueduct operational after earthquake damage. The timing of the event falls within the period of aqueduct operation which is reconstructed to be between 80 ± 10 and 270 ± 10 CE. Supporting evidence for earthquake activity within this period is seen in the roof collapse of the nearby Kakus cave.

THE ROLE OF THE GEOLOGICAL COMPOSITION IN THE STRUCTURAL MORPHOLOGY OF THE TERRITORY OF ALBANIA

In the context of geological composition, the territory of Albania closely depends on the geographic position. The presence of our country in the alpine-Mediterranean fold belt and the geological structures, called Albanide, have determined the intense development of the internal tectonic processes, as well as the external processes. The tectonic regime of the geological structures during the Miocene epoch to the Quaternary period, was accompanied by reverse faults and thrust faults one over the other of the tectonic areas of Albania. The morphologic and morphogenetic complex of the relief was created during the tectogenic period, especially during the tecto-orogenesis, where as consequence diverse magmatic. terrigenous and carbonates rocks were created. The highly pronounced character of the differential tectonic movements during morphotectonic evolution, especially during the plio-quaternary period, has created the actual morphological features of the relief of Albania.In the context of geological composition, the territory of Albania closely depends on the geographic position. The presence of our country in the alpine-Mediterranean fold belt and the geological structures, called Albanide, have determined the intense development of the internal tectonic processes, as well as the external processes. The tectonic regime of the geological structures during the Miocene epoch to the Quaternary period, was accompanied by reverse faults and thrust faults one over the other of the tectonic areas of Albania. The morphologic and morphogenetic complex of the relief was created during the tectogenic period, especially during the tecto-orogenesis, where as consequence diverse magmatic. terrigenous and carbonates rocks were created. The highly pronounced character of the differential tectonic movements during morphotectonic evolution, especially during the plio-quaternary period, has created the actual morphological features of the relief of Albania.The migration of orogenesis from east to west is conditioned by the dominance of mountainous ranges and ridges in the eastern and central parts, as well as in the fields and lowlands of the western part of Albania. The relief is distinguished by its diversified morphogenetic traits, due to the highly complex morphotectonic evolution, a large number of carbonate, terrigenous and magmatic rocks, as well as the significant influence of the outward processes. Due to the existence of composition of the large number of tectonic faults as well as the high values of tectonic uplift and downlift, the genetic composition of the structural relief was also created. Each of the sub-types within the structural relief is closely related to the presence of complex geological structures such as anticlinal, synclinal, monoclinal and aclinal structures. An important role have the structural landforms formed in the structures of faulting type, thus in the horst and graben structures, which are associated with very large morphological contrasts of the relief.A part of the horst and graben structures during the last period of pliocene and during the quaternary was involved by intense tectonic lifting movements, resulting to a fragmentation of flat bottom of ex-former depressions, and consequently they were transformed into depressions with fragmented bottom. A large part of structural relief landforms, such as structural benches, flat surfaces formed in the aclinal structure, structural surfaces, denudational surfaces and concave fragment of front of the cuestas, have been used for the construction of rural and urban settlements, for the road infrastructure network, the construction of human buildings, as well farmlands for the country's economy. The detailed analysis of the structural relief features, based on the characteristics of geological construction, enables prospects for taking measures against geomorphological, seismic and hydrological hazards.

Evidence for synsedimentary differential tectonic movements in a low-subsidence setting: Early Jurassic in northwestern Switzerland

During the Early Jurassic (lasting ~ 27 Myr) only thin deposits (mostly ca. 30–50 m) of the Staffelegg Formation accumulated in wide parts of NW Switzerland while sea-level rise was in the range of ~ 60 m. Isopach and facies patterns provide clear evidence of differential subsidence while faults that formed in the basement during the late Palaeozoic became reactivated. Orientation of many relative thickness minima and maxima follows faults constituting either the Rhenish Lineament or the North Swiss Permo-Carboniferous Trough. Such pattern is seen on the isopach maps of the Schambelen, Beggingen, Weissenstein, Frick, Fasiswald, Mt. Terri, Breitenmatt, Rickenbach, Rietheim and Gross Wolf members of the Staffelegg Formation, independently upon if the individual lithostratigraphic units are condensed or display somewhat enhanced thickness. Onto a general trend of decreasing thickness to the S, often isopach anomalies of small areal extension are superimposed. They suggest that localized strike-slip movements affected a mosaic of basement blocks. Reactivation of faults in the basement during the Early Jurassic is also evidenced by temporally enhanced hydrothermal activity as documented by chronometric ages of veins and mineral alterations.

A postglacial relative sea-level database for the Russian Arctic coast

We present the first quality-controlled relative sea-level (RSL) database for the Russian Arctic coast from the Barents Sea in the west to Laptev Sea in the east (29–152oE and 63 to 81oN). The database consists of 385 sea-level index points and 249 limiting dates and spans 24 ka to present. Sea-level indicators are derived from multiple proxies, including isolation basins, raised beaches, glacial erratics, marine terraces, laidas (salt marshes), and deltaic salt marshes. Here, we calculate the indicative meanings for all indicators and evaluated possible elevation errors. We have estimated the ages and uncertainties of index points and limiting dates using the most recent calibration datasets.In the western Russian Arctic (Barents and White Seas), RSL was driven by glacial isostatic adjustment (GIA) due to deglaciation of the Eurasian ice sheet complex. For example, within the Baltic crystalline shield, RSL fell rapidly from 80 to 100 m at 11–12 ka to 15–25 m at ∼4–5 ka. In the Arctic Islands of Franz-Joseph Land and Novaya Zemlya, RSL gradually fell from 25 to 35 m at 9 ka to 5–10 m at 3 ka. The Timan coast and the Kara Sea shelf are characterized by constant RSL rise due to proglacial forebulge collapse; Yamal and the Gydan Peninsula and Novaya Zemlya are all marked by a high LGM position of RSL, followed by a lowstand and consequent rise to a late Holocene highstand of several meters. Data from the Laptev Sea coasts and shelf and the New Siberian Islands demonstrate post-LGM RSL rise with a Holocene highstand of up to 5–10 m, with scatter caused by differential tectonic movements along a diffuse lithospheric plate boundary. The collected database allowed to estimate and discuss the reasons of both spatial and temporal variability of RSL histories in different parts of the Russian Arctic.

Tidally influenced shoal water delta and estuary in the Middle Jurassic of the Søgne Basin, Norwegian North Sea: sedimentary response to rift initiation and salt tectonics

AbstractRecent studies in the Middle Jurassic Bryne and Sandnes formations, primary reservoirs in several fields across the Norwegian and Danish North Sea, show the widespread occurrence of tidal-influenced and tide-dominated deposits. Aalenian–Bajocian Bryne cores reflect deposition by a shoal water, tidally influenced delta onto a low wave energy tidal platform (both supratidal and intertidal) that probably occupied the majority of the Søgne Basin, a narrow rift system connected to the Central and Danish graben and transgressed from an open-marine basin, possibly located to the south. At the Bathonian–Callovian boundary, a new phase of rifting and progressive salt movements led to the deposition of the upper Bryne and Sandnes formations within an 80–100 km long composite estuarine valley. Basin tilting to the south and continued transgression resulted in tidal deltas that offlap the northern margin of the basin. The basin was fully transgressed by the end of the Callovian. From the Late Bathonian onwards, differential tectonic movements along the broadly interconnected Middle Jurassic rift basins led to a change in the transgression direction from south to north, with an open-marine basin located in the Central and Viking graben.

BURIED VALLEYS IN MOUNTAIN REGIONS, COASTAL LOWLANDS AND CONTINENTAL SHELF IN THE ASIAN PART OF RUSSIA

In mountain areas, adjacent coastal lowlands and continental shelf in the Asian part of Russia a variety of buried valleys is found very different in their forming conditions and morphology. Classification of buried valleys is suggested that shows a great variety types, their formation conditions, morphometric and morphological characteristics. Buried valleys are divided into two main groups: 1) valleys formed in areas of rapid crustal uplifts and differential tectonic movements; 2) valleys formed in areas of tectonic subsidence such as transient areas between uplifting and sinking structures, inversion or inherited tectonic basins, individual valley sections preserved at the crossings of subsiding tectonic blocks, valleys buried in coastal lowlands, valleys buried in continental shelf due to the global sea level rise. In most areas, buried valleys are represented by a combination of different age generations of the above types. The degree of inheritance of the identified types of valleys varies and depends on the type and amplitude of tectonic movements. The larger the amplitude of tectonic movements is, the poorer is the inheritance of river network. In the areas of differential tectonic movements, inheritance may be detected not only for river network pattern, but also for morphodynamic types of river channels and even individual channel forms.

The sinking city: Earthquakes increase flood hazard in Christchurch, New Zealand

Airborne light detection and ranging (LiDAR) data were acquired over the coastal city of Christchurch, New Zealand, prior to and throughout the 2010 to 2011 Canterbury Earthquake Sequence. Differencing of pre- and post-earthquake LiDAR data reveals land surface and waterway deformation due to seismic shaking and tectonic displacements above blind faults. Shaking caused floodplain subsidence in excess of 0.5 to 1 m along tidal stretches of the two main urban rivers, greatly enhancing the spatial extent and severity of inundation hazards posed by 100-year floods, storm surges, and sea-level rise. Additional shaking effects included river channel narrowing and shallowing, due primarily to liquefaction, and lateral spreading and sedimentation, which further increased flood hazard. Differential tectonic movement and associated narrowing of downstream river channels decreased channel gradients and volumetric capacities and increased upstream flood hazards. Flood mitigation along the large regional Waimakariri River north of Christchurch may have, paradoxically, increased the long-term flood hazard in the city by halting long-term aggradation of the alluvial plain upon which Christchurch is situated. Our findings highlight the potential for moderate magnitude (MW 6-7) earthquakes to cause major topographic changes that influence flood hazard in coastal settings.

Geomorphic indices of rivers and drainage in China’s Longmen Shan Fault zone and their implications for regional tectonic activity

Theoretical models suggest that active tectonic deformation can impose a primary control on the patterns and styles of channels. The Longmen Shan Fault zone, which is located on the eastern margin of the Tibetan Plateau, has experienced strong tectonic activity, including uplift and strike-slip phases of tectonic movements. Here, we adopt ASTER-GDEM2 data and utilise a stream-power incision model to extract information on the spatial characteristics of differential tectonic movements. Analysis of the patterns and styles of 37 channels exhibits systematic differences in the channel steepness indices and the river sinuosity values along the strike of the Longmen Shan Fault zone. Our primary results demonstrate that the normalised channel steepness indices in the southern part of the Longmen Shan Fault zone are much higher than those in the northern part, where the river sinuosity values are much lower. Comparisons between the five drainage basins reveal that the river systems in the middle southern part of the fault zone are mainly controlled by tectonic uplift and thrusting, whereas the river systems in the middle northern part of the fault zone are mostly attributed to right-lateral strike-slip movement.

Stratigraphical position of pleistocene fluvial deposits of southeastern Srem and the Danube terraces in eastern Serbia

Pleistocene fluvial deposits have a significant distribution in Serbia, especially in the riparian area of the Danube and Sava in the southern part of the Pannonian basin. In this region these sediments are almost universally overlain by younger Pleistocene or Holocene deposits, and their thickness varies from 10 to 40 meters. Deposits of similar characteristics, that could be correlated to the synchronous ones in southern Srem, form high terraces of the Danube valley system. Morphologically, these terraces are of erosional-accumulation character. Some pre-Quaternary deposits of different composition and age are situated beneath the Pleistocene fluvial deposits. Significant height differences among these deposits in the part of southern Srem connected to the high terraces of the Danube are the consequence of differential tectonic movements which were expressed in subsidence of the Panonnian basin, and in stagnation or uplifting in the river valleys.

Differential tectonic movements in the confluence area of the Huang Shui and Huang He rivers (Yellow River), NE Tibetan Plateau, as inferred from fluvial terrace positions

In the Northeastern Tibetan Plateau (NETP), the courses of the Huang Shui and Huang He near their confluence are characterized by alternating gorges and wide depressions, segmenting the fluvial systems. The river valleys have developed terrace staircases, which are used to infer relative tectonic motions between the segments. The terrace staircases are correlated by means of relative height and optically stimulated luminescence (OSL) dating. At least eight terraces are present, two of which have been dated by OSL (the sixth and the third ones; c. 70 and c. 24 ka, respectively). The correlated longitudinal terrace profiles show no distinct relative tectonic movements within the confluence area, demonstrating that this area behaved as one tectonic block. The correlation of the terrace staircase of this block with areas upstream (Xining area) and downstream (eastern Lanzhou area) indicates relative tectonic movements, which therefore represent different tectonic blocks. The fluvial incision rate since c. 70 ka was much higher in the confluence area than in the blocks upstream and downstream, possibly indicating relative uplift. This relatively strong uplift provided more space for differentiation within the terrace staircase as a result of climatic changes, leading to six terraces formed as a response to minor climatic fluctuations (103–104 year timescale) since the last interglacial. This may indicate that the stronger the tectonic movement the better the climatic imprint as expressed in the form of terrace development. Over a shorter timescale, two accumulation terraces with thick stacked deposits (&gt;18 m) may indicate relative subsidence in the confluence, occurring sometime between 20 and 70 ka. This indicates changes in relative vertical crustal motions at timescales of tens of thousands of years. We speculate that the inferred tectonic motions are related to transpression movements in the NETP as a result of the collision of the Indian and Asian plates.

Morphostructural patterns and landform generations in a glaciated passive margin: the Kobberminebugt-Qaqortoq region of South Greenland

On the west coast of South Greenland, the passive continental margin displays a left-lateral step which is not apparent on the east coast and coincides with a topographic change that marks the transition between Archaean basement rocks to the north and the Ketilidian orogenic belt to the south. Two issues are considered: (1) the origin of the regional topographic asymmetry between the mountains of southeast and southwest Greenland; (2) the origin of the Kobberminebugt-Qaqortoq lowlands (differential early Cenozoic tectonic movements and/or subsequent differential erosion in the uplifted landmass). By identifying and mapping stepped landforms, morphostructural patterns and weathering features, we discriminate between control by differential erosion and tectonic movements. We suggest that the stepped patterns sof erosion surfaces represent a pre-glacial landform evolution related to the uplift of two antiforms along the west and east coast of southern Greenland. In addition, late fault reactivation may have favoured the development of a low coastal surface in less uplifted blocks. A relative chronology of landform development in the study area is given. Although implying a strong involvement of differential erosion, our interpretation of the geomorphology is compatible with a late reactivation of an oblique transfer zone formed during the early Cenozoic rifting.

3-D assessment of peak-metamorphic conditions by Raman spectroscopy of carbonaceous material: an example from the margin of the Lepontine dome (Swiss Central Alps)

This study monitors regional changes in the crystallinity of carbonaceous matter (CM) by applying Micro-Raman spectroscopy to a total of 214 metasediment samples (largely so-called Bundnerschiefer) dominantly metamorphosed under blueschist- to amphibolite-facies conditions. They were collected within the northeastern margin of the Lepontine dome and easterly adjacent areas of the Swiss Central Alps. Three-dimensional mapping of isotemperature contours in map and profile views shows that the isotemperature contours associated with the Miocene Barrow-type Lepontine metamorphic event cut across refolded nappe contacts, both along and across strike within the northeastern margin of the Lepontine dome and adjacent areas. Further to the northeast, the isotemperature contours reflect temperatures reached during the Late Eocene subduction-related blueschist-facies event and/or during subsequent near-isothermal decompression; these contours appear folded by younger, large-scale post-nappe-stacking folds. A substantial jump in the recorded maximum temperatures across the tectonic contact between the frontal Adula nappe complex and surrounding metasediments indicates that this contact accommodated differential tectonic movement of the Adula nappe with respect to the enveloping Bundnerschiefer after maximum temperatures were reached within the northern Adula nappe, i.e. after Late Eocene time.

Vertical crustal motions from differential tide gauge observations and satellite altimetry in southern Italy

Our goal is to determine vertical crustal movement rates from tide gauge and satellite altimetry measurements. Tide gauges measure sea level, but as they are fixed to the crust, they sense both sea surface height variations and vertical crustal movements. The differential sea level rates of sufficiently nearby stations are a good means to determine differential crustal movement rates, when sea level height variations can be assumed to be homogeneous. Satellite altimetric measurements determine sea surface height variations directly and can be used to separate the crustal signal from the sea surface height variations in tide gauge measurements. The correction of the tide gauge sea level rates for the sea surface height contribution requires collocation of the satellite pass and the tide gauge station. We show that even if this is not the case, the satellite altimetric observations enable correction of differential tide gauge rates for the effects of sea surface rate inhomogeneities. We apply the methodology to an area of broad scientific interest, due to its high seismic risk and its location as standpoint for a proposed major bridge connecting Sicily to the Italian mainland. We find that the Southern Calabria and the eastern Sicily tide gauges have a deficit in sea level increase of 1–2 mm/yr with respect to the north western Sicilian tide gauge. The satellite altimetric observations show that this differential movement must be caused by a tectonic component, because the sea surface rates are higher offshore eastern Sicily compared to offshore western Sicily. The satellite altimetric rates show that the sea surface rates are inhomogeneous in the Mediterranean and have larger amplitudes as we move away from the coast than immediately offshore. Our technique can be applied to any part of the world where tide gauge observations are available, because satellite altimetric observations are global. © 2010 Elsevier Ltd. All rights reserved.

Late Cenozoic fluvial development within the Sea of Azov and Black Sea coastal plains

Late Cenozoic terrestrial deposits are widespread across the northern coastal regions of the Black Sea and the Sea of Azov and represent diverse fluvial, estuarine and deltaic environments. The dating and correlation of these deposits rely on stratigraphically-associated marine index beds, mammalian and molluscan faunas and magnetostratigraphy. In detail the geometries of these sediment bodies are extremely complex, typically varying between localities and representing many cycles of incision and aggradation. However, the overall disposition of the sediments reflects the transition from the uplifting sediment source region to the north and the subsiding depocentre in the interior of the Black Sea to the south. Since the Middle Miocene the area of the Paratethys/Black Sea depocentre has decreased significantly, but since the Middle Pliocene the hinge zone between uplift and subsidence has been located close to the modern coastline. A combination of regional and local differential crustal movements has given rise to the great variety of fluvial sediment bodies, to the erosion–aggradation cycles, different phases and river activity and to the various fluvial landforms that have all been important in landscape development in this region during the past 12 Ma. The fluvial erosion–accumulation cycles (during the upper Serravillian–Messinian, the Zanclean–late Gelasian, and the Pleistocene) and corresponding cycles of relief dissection and planation are reconstructed against a background of local sea-level changes and climatic variations determined from palaeobotanical data. The maximum fluvial incision occurred in the early Zanclean time with alluvial coastal plains, unique in this area, developing in the Gelasian. Increased climatic aridity during the Pleistocene caused a reduction of fluvial activity in comparison with the Late Miocene and Pliocene. The sea-level oscillations and Pleistocene glaciations affected fluvial processes in different ways. The most remarkable events were the substantial reduction of fluvial activity during the Messinian dessication in the Black Sea and drainage of the shelf, with intensive dissection, coeval with the Last Glaciation.

Convective heat transfer in a steeply dipping fault zone and its impact on the interpretation of fission-track data - a modelling study

AbstractThe effects of convective heat transfer by hydrothermal fluid flow on fission-track (FT) thermochronology are studied using numerical modelling techniques. Parameter studies are carried out on two-dimensional crustal segments with a steeply dipping fault zone exposed to constant denudation to evaluate the relative importance of different variables, including denudation rate as well as hydraulic and material properties. Time–temperature histories of particle points are calculated in the vicinity and also a few kilometres away of the fault zone. These time–temperature paths are then used in a forward-modelling approach to determine the expected FT cooling ages and track-length distributions.Modelling results indicate that hydrothermal fluid flow can significantly disturb the background conductive thermal state of the upper crust, and the interpretation of FT data using a steady-state geothermal gradient can result in erroneous denudation rates that overestimate the true erosion rates by more than 80%. A pattern of highly varied FT cooling ages from samples at the same elevation does not necessarily ask for differential tectonic movements, instead it can be generated by deep circulation of groundwater within a few million years (Ma). Denudation rates inferred from FT cooling age–elevation plots are likewise inaccurate in a hydrothermally active area because the important assumption about closure temperature isotherms being horizontal or at a constant depth below the surface is not met.

Holocene relative sea-level change, isostatic subsidence and the radial viscosity structure of the mantle of northwest Europe (Belgium, the Netherlands, Germany, southern North Sea)

A comprehensive observational database of Holocene relative sea-level (RSL) index points from northwest Europe (Belgium, the Netherlands, northwest Germany, southern North Sea) has been compiled in order to compare and reassess the data collected from the different countries/regions and by different workers on a common time–depth scale. RSL rise varies in magnitude and form between these regions, revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity. It clearly contains a non-linear, glacio- and/or hydro-isostatic subsidence component, which is only small on the Belgian coastal plain but increases significantly to a value of ca 7.5m relative to Belgium since 8cal.kaBP along the northwest German coast. The subsidence is at least in part related to the Post-Glacial collapse of the so-called peripheral forebulge which developed around the Fennoscandian centre of ice loading during the Last Glacial Maximum. The RSL data have been compared to geodynamic Earth models in order to infer the radial viscosity structure of the Earth's mantle underneath NW Europe (lithosphere thickness, upper- and lower-mantle viscosity), and conversely to predict RSL in regions where we have only few observational data (e.g. in the southern North Sea). A very broad range of Earth parameters fit the Belgian RSL data, suggesting that glacial isostatic adjustment (GIA) only had a minor effect on Belgian crustal dynamics during and after the Last Ice Age. In contrast, a narrow range of Earth parameters define the southern North Sea region, reflecting the greater influence of GIA on these deeper/older samples. Modelled RSL data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow, WNW–ESE trending band connecting the German federal state of Lower Saxony with the Dogger Bank area in the southern North Sea. Identification of the effects of local-scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea-level index points based on model-data comparisons is possible but is still complicated by the relatively large range of Earth model parameters fitting each RSL curve, emphasising the need for more high-quality observational data.

How stable is the Mississippi Delta?

Large deltas are commonly believed to exhibit rapid rates of tectonic subsidence, largely due to sediment loading of the lithosphere. As a result, deltaic plains are prone to accelerated relative sea-level rise, coastal erosion, and wetland loss. Hurricane Katrina’s devastation testifies to the severe threat that these processes pose to the Mississippi Delta, but the relative role of tectonics versus other mechanisms causing land subsidence remains elusive. Relative sea-level records derived from basal peat have the potential to quantify differential crustal movements over Holocene time scales with exceptionally high accuracy and precision. Here we present new sea-level index points from two study areas in the southwestern Mississippi Delta that essentially coincide with a recently published detailed relative sea-level record from the eastern part of the delta. Our results show that differential vertical movements among the three study areas have been only 0.1 mm yr 1 .W e compare our evidence with a recent sea-level compilation from the Caribbean, to a large extent based on data from areas that are tectonically stable. Our sea-level index points nearly coincide with the Caribbean data, showing surprising tectonic stability for considerable sections of the Mississippi Delta. However, the well-documented high subsidence rates in and near the birdfoot of the Mississippi Delta indicate that different conditions prevail there. The rapid wetland loss in coastal Louisiana is likely due, to a considerable extent, to the compaction of Holocene strata.

Detection of neotectonic deformations along the Rio do Peixe Valley, Western São Paulo State, Brazil, based on the distribution of late Quaternary allounits

Terrace deposits (34 10 ka) were mapped in the Rio do Peixe valley and submitted to an allostratigraphic analysis. Three allomembers (viz. “A”, “B”, and “C” ) were established in the medium to lower river valley and other three allounits (allomembers “ L”, “M” and “N”) were defined in the upper valley. It is probable tha “B” and “M” allomembers represent the same stratigraphic level. The spatial distribution of these allomember shows the influence of the Recent base-level changes, due to neotectonics events. Longitudinal cross-section o the Rio do Peixe valley shows that it is possible to define some areas with differential tectonic movements, tha includes uplift blocks (prone to erosion and terrace deposit destruction), and other areas with relative subsidence, controlling both the Recent alluvial plains and the preservation of some ancient terrace deposits. This scenery is in accordance with regional tectonic studies.

Sequence stratigraphic analysis in deep-water, underfilled NW European passive margin basins

Sequence stratigraphic analysis is now carried out routinely on Mesozoic–Cenozoic sedimentary basins with a view to understanding their post-rift stratal geometries and predicting facies architecture. The conventional method embodies two concepts; the physical division of strata into unconformity-bounded units and their genetic interpretation on the assumption that hierarchical changes in sea-level represent the primary control on sedimentary architecture. The genetic model is reflected in a complex descriptive terminology and derives from the development of the method in shallow-water basins, where the results of analyses typically accord with geological data constraints. Applied to deep-water underfilled basins, however, the sea-level assumption yields results that are unsatisfactory and in many cases misleading, reflecting the influence of additional controls, including tectonic movements, deep-sea currents and climate (e.g. glaciation) on stratal geometries and facies architecture. This is illustrated by comparative analyses of examples from the deep-water Cenozoic basins of the NW European Atlantic passive margin, which contain a set of seismic megasequences, bounded by unconformable to conformable surfaces, correlative from shelf to slope to basinal settings. The deep-water successions contain regional, locally diachronous, submarine unconformities that were generated in response to changes in deep-water current circulation and slope processes, rather than subaerial erosion. These bound aggradational contourite drifts that include upslope accretion against basin margins. The deep-water successions interfinger at two levels with seaward-prograding shelf-slope wedges that reflect differential tectonic movements, involving coeval uplift and subsidence. The youngest wedges formed in the last 4 Ma and record seaward progradation of the margin by up to 100 km, overprinting high-amplitude variations in sea-level and coeval with changes in deep-ocean currents. Sediment supply by fluvial sources gave way in the Pleistocene to direct glacial sediment supply to the slope. In all these instances, the stratal geometries and facies architecture cannot be attributed to a simple lowering of regional sea-level, but instead reflect a complex interplay of controlling factors including tectonic movements, changes in sediment supply, deep-water current activity and climate, in addition to sea-level. Sequence stratigraphic analysis in such settings must recognise and evaluate alongslope, downslope and vertical components of sediment supply.

Neogene evolution of the Atlantic continental margin of NW Europe (Lofoten Islands to SW Ireland): anything but passive

A regional stratigraphic framework for the Neogene succession along and across the NW European margin is presented, based on a regional seismic and sample database. The stratigraphy provides constraints on the timing and nature of the mid- to late Cenozoic differential tectonic movements that have drivenmajor changes in sediment supply, oceanographic circulation and climate (culminating in continental glaciation). The overall context for Neogene deposition on the margin was established in the mid-Cenozoic, when rapid, km-scale differential subsidence (sagging) created the present-day deep-water basins. The Neogene is subdivided into lower (Miocene–lower Pliocene) and upper (lower Pliocene–Holocene) intervals. The lower Neogene contains evidence of early to mid-Miocene compressive tectonism, including inversion anticlines and multiple unconformities that record uplift and erosion of basin margins, as well as changes in deep-water currents. These movements culminated in a major expansion of contourite drifts in the mid-Miocene, argued to reflect enhanced deep-water exchange across the Wyville-Thomson Ridge Complex, via the Faroe Conduit. The distribution and amplitude of the intra-Miocene movements are consistent with deformation and basin margin flexure in response to enhanced intra-plate compressive stresses during a local plate reorganization (transfer of the Jan Mayen Ridge from Greenland to Europe). The upper Neogene records a seaward tilting (&lt;1°) of the margin from the early Pliocene, in which km-scale uplift and erosion was accompanied by increased offshore subsidence, resulting in a major seaward progradation of the shelf–slope wedge as well as deep-marine erosion during a reorganization of bottom current patterns. The large amplitude of tilting cannot be accounted for by intra-plate stress variations, but is consistent with a dynamic topographic response to upper mantle convection, in particular edge-driven flow beneath the continental margin. Sedimentary and oceanographic changes resulting from dynamic topographic responses to the evolution of upper mantle convective flow during ocean widening may be characteristic of the development of ‘passive’ continental margins.