Magnitude Of Uplift Research Articles

Late Cenozoic uplift of the Sierra Nevada, California? A critical analysis of the geomorphic evidence

From the earliest days of California geology, the ramp-like profile of the northern half of the Sierra Nevada mountains and putative signs of recent incision have been interpreted as evidence that the range was formed by the tilting of a rigid block in the late Cenozoic. Over the years, various geomorphic analyses have been used to quantify the magnitude of uplift and to establish its timing, such as analyzing the gradients of ancient channels, examining the tilt of sedimentary beds, and reconstructing the incisional history of rivers. Most studies that have used these methods have supported substantial (\>500 m) recent uplift of the Sierra. In contrast, investigations based on other sources of paleotopographic information, such as isotope records, thermochronology, and detrital zircon geochronology, have found that the Sierra have been at high elevations for much of the Cenozoic. This set of contradictory results motivates a re-examination of the geomorphic evidence for late Cenozoic uplift. A critical assessment of these geomorphic studies, based on new topographic analyses and field investigations, reveals that their conclusions are not well supported. For example, several studies based their results on reconstructions of ancient channels that would have flowed up and over bedrock ridges as high as 190 m, a physical impossibility. Other weaknesses include unjustified assumptions regarding the original tilt of fluvial deposits, misinterpretations of stratigraphic relationships, and inadequate recognition of the effect of lithology on channel profiles. The studies supporting recent tilting in the *northern* Sierra Nevada are inconclusive and rely on observations not unique to tectonic forcing. Indeed, much of the evidence based on the paleogradients of the Tertiary channels is consistent with an early trellis drainage network formed across alternating bands of resistant and weak lithologies. In addition, analyses are presented to demonstrate that deep northern Sierran canyons thought to have been recently incised were, instead, cut as early as the Eocene-Oligocene. Two geomorphic studies from the *southern* Sierra are consistent with late Cenozoic tilting and uplift although ongoing tectonic activity may be insignificant. Finally, I present a conceptual model of the evolution of the Sierran landscape, applicable primarily to the northern half of the range, illustrating the development of three different drainage networks since the late Jurassic.

Numerical Simulation of Effect of Foundation Pit Excavation on Underlain Shield Tunnel

In the background of a foundation pit excavation project on Yanan Road in Hangzhou City, this study simulated the excavation of foundation pit above an underground tunnel using 3D MIDAS/GTS software. The combined action of foundation pit, ground and tunnel were considered. The influence of foundation pit excavation on the deformation of underlain shield tunnel was evaluated and simulations were carried out on the effectiveness of different strengthening and control approaches. Results from the research showed that during the stages of piling and ground strengthening, settlement occurred at the tunnel; with the excavation of foundation pit, uplift deformation at the bottom of the foundation pit and the tunnel increased; with stricter strengthening and control techniques employed, the magnitude of uplift at the tunnel and bottom of the foundation pit reduced, suggesting that various control procedures were effective to some extent.

Linking morphology across the glaciofluvial interface: A 10Be supported chronology of glacier advances and terrace formation in the Garonne River, northern Pyrenees, France

The Garonne River drains an important part of the northern Pyrenees and its northern foreland. We investigated the middle reaches of the Garonne River establishing a detailed morphogenetic profile of its foreland terrace staircase and the preserved palaeoglacier margins. We particularly focussed on the glaciofluvial interface, linking (also genetically) the fluvial sediment archives in the foreland with the terminal glacial basin upstream of the Pyrenees mountain front. Using cosmogenic nuclide 10Be analyses, two terrace exposures have been dated, including a prominent fluvioglacial outwash fan at the foreland transition. We identified three terminal margins of late Pleistocene glacier advances. The prominent Garonne staircase consists of three major terrace complexes, comprising eight individual terrace levels. Results indicate a young age of the lower terrace complex of the Garonne staircase (MIS 4–2). The morphogenetic relationships and the new 10Be exposure age constraints suggest that during the last glaciation (Würmian) the Garonne glacier reached its maximum extent at the north Pyrenean mountain front, apparently already during MIS 4. Two different ice margins were associated with MIS 2, indicating close to maximum ice-extent during early MIS 2 (LGM) and relatively stationary ice-recession in the late MIS 2. The extensive Garonne terrace complexes formed under cold-climate conditions and were abandoned by incision during major glacial–interglacial transitions. During warm–cold climate transitions lateral erosion caused the reworking of previously abandoned palaeofloodplains.The long-term (Quaternary) incision of the Garonne and other north Pyrenean rivers indicates that the proximal Aquitaine foreland basin experienced uplift. However, non-uniform lateral course migrations and valley asymmetries of the north Pyrenean piedmont rivers indicate that uplift magnitude is variable, with maximum amounts in the centre of the molasse-fan of Lannemezan: Rivers on the western part of the fan were tilted toward the west, whereas rivers in the eastern part, like the Garonne, were tilted to the east.

Uplift and denudation history of the eastern Dead Sea rift flank, SW Jordan: Evidence from apatite fission track thermochronometry

AbstractThe Dead Sea rift (DSR), developed along the Dead Sea transform plate boundary, is characterized by salient flanks and morphotectonic asymmetry. Apatite fission track thermochronology (AFT) along ~1200 m high vertical profiles in Neoproterozoic basement and overlying Cambrian sandstone in southwestern Jordan is used to reconstruct timing, magnitude, and rate of uplift and denudation of the eastern DSR flank and examine its relationship to rift development and its flank landscape. Time‐temperature models based on AFT data suggest three major Phanerozoic heating and cooling episodes, Late Paleozoic, Early Cretaceous, and Oligocene. The latest episode, on which this study focuses, indicates uplift of ~3.8±0.3 km under a moderate paleogeothermal gradient. About 40% of the uplift was tectonically driven with the remainder attributed to isostatic rebound in response to denudation and erosion. Models suggest that uplift commenced in the Oligocene with a considerable part occurring prior to development of the DSR, despite being ~200 km from the Red Sea‐Gulf of Suez rift margin. Uplift is probably part of a regional rearrangement along the western Arabian platform margin occurring at the time of Red Sea rift initiation. Transition from primarily sedimentary layer stripping, most likely by scarp retreat, to one of dominantly incision of the underlying crystalline basement occurred in Late Miocene‐Pliocene time following enhanced subsidence and development of a low base level in the DSR. Consequently, the magnitude of uplift by isostatic rebound due to incision exceeded lowering by surface truncation and increased summit elevation and riftward flexing of the flank.

Centrifuge Modeling on Manhole Uplift in a Liquefied Trench

The uplift behavior of sewage manholes due to liquefaction in a trench is investigated through a series of dynamic centrifuge model tests. The objectives of a series of tests are to study the mechanism of the uplift and to obtain relationships among uplift displacement and factors affecting the uplift. The factors considered in the experiments are the ground water levels, the magnitude of input accelerations, the duration time of shaking, the relative densities of trench backfill and the native ground, the material of native ground, the volume of a trench, the apparent unit weight of a manhole, and the contact conditions at the bottom of a manhole. Test results show that the primary cause of uplift is the reduction of the effective confining stress near the bottom of a manhole due to strong shaking. The magnitude of uplift is found to be strongly correlated with the ground water depth, the intensity of shaking, the shear deformation of the trench, and the contact conditions at the bottom of the manhole. These findings are believed to be useful for engineering practice in the mitigation of the manhole uplift.

Chapter 17 Uplift and erosion of the greater Barents Sea: impact on prospectivity and petroleum systems

Abstract A regional net erosion map for the greater Barents Sea shows that the different areas in the Barents Sea region have been subject to different magnitudes of uplift and erosion. Net erosion values vary from 0 to more than 3000 m. The processes have important consequences for the petroleum systems. Reservoir quality, maturity of the source rocks and the migration of hydrocarbons are affected by the processes. Owing to changes in the PVT conditions in a hydrocarbon-filled structure, uplift and erosion increase the risk of leakage and expansion of the gas cap in a structure. Understanding of the timing of uplift and re-migration of hydrocarbons has been increasingly important in the exploration of the Barents Sea.

Reprint of: Maturity modelling integrated with apatite fission-track dating: Implications for the thermal history of the Mid-Polish Trough (Poland)

The Mid-Polish Trough (MPT) is situated in the easternmost part of the Central European Basin System (CEBS) and stretches NW–SE across the Polish Basin. It was characterised by pronounced subsidence and thick sediment accumulation between the Permian and the Late Cretaceous. Late Cretaceous–early Paleogene basin inversion led to the formation of the Mid-Polish Swell (MPS). The study area is located within the Pomeranian segment of the MPT/MPS (NW Poland) and experienced up to 7 km Permian-Mesozoic subsidence. PetroMod 1-D modelling was performed on several well-sections in order to study Permian to recent burial-uplift evolution. The modelling was calibrated with new vitrinite reflectance (VR r) data and allowed to constrain the magnitude of uplift and related erosion as well as provided a first overview of the temperature history. The base of the studied Permian–Mesozoic successions attained maximum burial depths of 4800–5400 m before the onset of the inversion, less than in the axial trough area. The thickness of pre- and most probably also syn-inversion Upper Cretaceous deposits is estimated as 300 m. Erosion associated with inversion processes removed between 900 and 1400 m of the Mesozoic sediments, i.e. 1000–1500 m less than in the most inverted central part of the trough. VR r data suggest constant Permian–Mesozoic heat flows corresponding to present-day values (40–45 mW/m 2). Apatite fission-track (AFT) ages modelled with the PetroMod module PetroTracks show a good fit with AFT ages directly measured on well samples, and further support the assumption of steady heat flow in the range 40–45 mW/m 2. Palaeotemperatures appear to have decreased towards the East European Craton margin, which is compatible with the present day distribution of heat flow. Thermal history modelling shows a relatively simple Permian–Mesozoic heat flow pattern in the Pomeranian segment of the MPT. Such a scenario implies that the present-day heat flow distribution has not changed essentially since Mesozoic times.

Coupled reservoir-geomechanical analysis of CO 2 injection and ground deformations at In Salah, Algeria

In Salah Gas Project in Algeria has been injecting 0.5–1 million tonnes CO 2 per year over the past 5 years into a water-filled strata at a depth of about 1800–1900 m. Unlike most CO 2 storage sites, the permeability of the storage formation is relatively low and comparatively thin with a thickness of about 20 m. To ensure adequate CO 2 flow-rates across the low-permeability sand-face, the In Salah Gas Project decided to use long-reach (about 1–1.5 km) horizontal injection wells. In an ongoing research project we use field data and coupled reservoir-geomechanical numerical modeling to assess the effectiveness of this approach and to investigate monitoring techniques to evaluate the performance of a CO 2 injection operation in relatively low-permeability formations. Among the field data used are ground surface deformations evaluated from recently acquired satellite-based inferrometry (InSAR). The InSAR data shows a surface uplift on the order of 5 mm per year above active CO 2 injection wells and the uplift pattern extends several km from the injection wells. In this paper we use the observed surface uplift to constrain our coupled reservoir-geomechanical model and conduct sensitivity studies to investigate potential causes and mechanisms of the observed uplift. The results of our analysis indicate that most of the observed uplift magnitude can be explained by pressure-induced, poro-elastic expansion of the 20-m-thick injection zone, but there could also be a significant contribution from pressure-induced deformations within a 100-m-thick zone of shaly sands immediately above the injection zone.

Late Cenozoic structural and tectonic development of the western margin of the central Andean Plateau in southwest Peru

Structural and thermochronologic studies of the western margin of the central Andean Plateau show changing styles of deformation through time that give insights into tectonic evolution. In southwest Peru, uplift of the plateau proceeded in several distinct phases. First, NW striking, NE dipping reverse faults accommodated uplift prior to ∼14–16 Ma. Subsequent uplift of the plateau relative to the piedmont (between the plateau and the Pacific Ocean) occurred between ∼14 and 2.2 Ma and was accommodated by NW striking, SW dipping normal faults and subparallel monoclinal folds. The youngest phase of uplift affected the piedmont region and the plateau margin as a coherent block. Although the uplift magnitude associated with phase 1 is unknown, phases 2 and 3 resulted in at least 2.4–3.0 km of uplift. Up to 1 km of this may have occurred during phase 3. Geodynamic processes occurring in both the continental interior and the subduction zone likely contributed to uplift.

Post-rift landscape development of north-east Brazil

The evolution of the landscape of north-east Brazil in relation to the burial and exhumation history of both onshore and offshore areas is the focus of a research project carried out for StatoilHydrodo Brasil and Petrobras from 2007 to 2009 by the Geological Survey of Denmark and Greenland in collaboration with Geotrack International. In hydrocarbon exploration it is important to understand the regional tectonic framework and thus also to consider the volumes of rocks that may have been present and then removed during the geological past. For example, the timing of hydrocarbon generation and changes in migration routes can be assessed when the timing and magnitude of uplift and erosion is known. Studies in West Greenland have demonstrated the usefulness of large-scale, low-relief, high-level landscapes as markers of uplift events, and in particular the strength of combining the denudation history from landscape analysis with the cooling history from apatite fission-track analysis (AFTA) data and the stratigraphic record (Bonow et al. 2006, 2007; Japsen et al. 2006, 2009). In the study area, there are two plateaux with elevations up to c. 1300 m above sea level (a.s.l.). The plateaux are currently being dissected by deeply incised fluvial valleys, and escarpments separate the two plateaux. The lowlands cut across Early Cretaceous rift systems along the Atlantic margin, including the intracontinental Recôncavo–Tucano–Jatobá (RTJ) Rift and also the Camamu Basin, of which the western margin is exposed onshore (Fig. 1). The RTJ Rift is a mature hydrocarbon province, whereas the deep-water parts of the Camamu Basin are the target of frontier exploration (e.g. Magnavita et al. 1994; Davison 1999; Cobbold et al. 2008). The post-rift sequence in the RTJ Rift and the inshore Camamu Basin is thin or absent. However, it has been estimated that up to 2000 m of sedimentary cover once was present, but has now been removed (Magnavita et al. 1994).

Maturity modelling integrated with apatite fission-track dating: Implications for the thermal history of the Mid-Polish Trough (Poland)

The Mid-Polish Trough (MPT) is situated in the easternmost part of the Central European Basin System (CEBS) and stretches NW–SE across the Polish Basin. It was characterised by pronounced subsidence and thick sediment accumulation between the Permian and the Late Cretaceous. Late Cretaceous–early Paleogene basin inversion led to the formation of the Mid-Polish Swell (MPS). The study area is located within the Pomeranian segment of the MPT/MPS (NW Poland) and experienced up to 7 km Permian-Mesozoic subsidence. PetroMod 1-D modelling was performed on several well-sections in order to study Permian to recent burial-uplift evolution. The modelling was calibrated with new vitrinite reflectance (VR r) data and allowed to constrain the magnitude of uplift and related erosion as well as provided a first overview of the temperature history. The base of the studied Permian–Mesozoic successions attained maximum burial depths of 4800–5400 m before the onset of the inversion, less than in the axial trough area. The thickness of pre- and most probably also syn-inversion Upper Cretaceous deposits is estimated as 300 m. Erosion associated with inversion processes removed between 900 and 1400 m of the Mesozoic sediments, i.e. 1000–1500 m less than in the most inverted central part of the trough. VR r data suggest constant Permian–Mesozoic heat flows corresponding to present-day values (40–45 mW/m 2). Apatite fission-track (AFT) ages modelled with the PetroMod module PetroTracks show a good fit with AFT ages directly measured on well samples, and further support the assumption of steady heat flow in the range 40–45 mW/m 2. Palaeotemperatures appear to have decreased towards the East European Craton margin, which is compatible with the present day distribution of heat flow. Thermal history modelling shows a relatively simple Permian–Mesozoic heat flow pattern in the Pomeranian segment of the MPT. Such a scenario implies that the present-day heat flow distribution has not changed essentially since Mesozoic times.

Coupled reservoir-geomechanical analysis of CO2 injection at In Salah, Algeria

In Salah Gas Project in Algeria has been injecting nearly one million tonnes CO2 per year over the past four years into a water-filled strata at a depth of about 1,800 to 1,900 m. Unlike most CO2 storage sites, the permeability of the storage formation is relatively low and comparatively thin with a thickness of about 20 m. To ensure adequate CO2 flow-rates across the low-permeability sand-face, the In Salah Gas Project decided to use long-reach (about 1 to 1.5 km) horizontal injection wells. In this study we are using field data and coupled reservoir-geomechanical numerical modeling of CO2 injection to analyze geomechanical responses and to assess the effectiveness of this approach for CO2 storage in relatively low permeability formations. Among the field data used are surface deformations evaluated from recently acquired satellite-based inferrometry (In SAR). The In SAR data shows a surface uplift on the order of 5 mm per year above active CO2 injection wells and the uplift pattern extends several km from the injection wells. We use the observed surface uplift to constrain our coupled reservoir-geomechanical model. We conduct sensitivity studies to investigate potential causes and mechanisms of the observed uplift. Preliminary results of our analysis presented in this paper indicates that most of the observed uplift magnitude can be explained by poro-elastic expansion of the 20 m thick injection zone, but there could also be a significant contribution from pressure changes within the adjacent caprock. Moreover, we show that surface deformations from In SAR can be useful for tracking the fluid pressure and for detection of a permeable leakage path (e.g. in a permeable fault) through the overlying caprock layers.

Uplift of a Coral Island in the Andaman Sea Due to the 2004 Sumatra Earthquake Measured Using Remote Sensing Reflectance of Water

The 2004 Sumatra earthquake, together with the tsunami that followed, caused massive destruction in many coastal areas of the Indian Ocean. Uplift and subsidence of land near the epicenter of the earthquake in the Andaman Sea have been reported. In this letter, we report observations of the uplift in high-resolution SPOT-5 satellite images in a coral island near the Andaman Islands. The depth of the submerged reefs was measured using water reflectance models commonly employed in the ocean color research community. The uplift magnitude was estimated by the difference in water depth measured in the pre- and post-earthquake images, taking into account the difference in tide levels. The uplift was found to be 1.6 m with an uncertainty of about 0.3 m. The methodology could be widely used for efficient estimation of shallow water depth of broad areas, particularly over shallow coral reefs.

Crustal deformation in the Central Ionian Islands (Greece): Results from DGPS and DInSAR analyses (1995–2006)

Ground deformation studies based on Differential GPS (DGPS) and Differential Interferometric SAR (DInSAR) analyses have been conducted in the seismically active area of the Central Ionian Islands. Local GPS networks were installed in Cephallonia (2001) and Zakynthos (2005). The Cephallonian network has been remeasured five times and Zakynthos' once as of July 2006. The studies have yielded detailed information regarding both local and regional deformations that are occurring in the area. For Lefkas Island, DInSAR analysis (March to September 2003) revealed 56 mm of uplift in the central and western parts and is attributed to the August 2003 earthquake ( M w = 6.3) that occurred offshore to the west. Synthetic DInSAR modelling of the magnitude and extent of deformation is consistent with the seismologically deduced parameters for the ruptured segment along the Lefkas Transform Fault. Subsidence (< 28 mm) along the northern part of the island is attributed to local conditions unrelated to the earthquake. For Zakynthos Island, large-magnitude earthquakes that occurred offshore to the south in October 2005 and April 2006 most likely contributed to the observed deformation as deduced from DGPS measurements for an encompassing period (August 2005 to July 2006). The largest amount of horizontal deformation occurred in the south, where its western part moved in a W–NW direction, while the eastern part moved towards the NE, with magnitudes ranging from 15 to 26 mm. The southern part of the island uplifted a maximum of 65 mm whereas the north subsided from 12 to 28 mm. For Cephallonia Island, DInSAR analysis (1995 to 1998) indicated ground deformation up to 28 mm located in small sections of the island. Further interferometric analysis for the period 2003 to 2004, encompassing the occurrence of the Lefkas earthquake in August 2003, indicated 28 mm of uplift in the northern part, while during the next two years (2004 to 2005), further uplift of at least 56 mm had taken place at the western and northern part of the island. DGPS measurements for the period 2001 to 2006 revealed a clockwise rotation of the island with respect to a centrally located station on Aenos Mt. The horizontal component of deformation generally ranged from 6 to 34 mm, with the largest values at the western and northern parts of the island. Considering the vertical deformation, two periods are distinguished. The first one (2001 to 2003) is consistent with anticipated motions associated with the main geological and tectonic features of the island. The second one (2003 to 2006) has been tentatively attributed to dilatancy in which relatively small uplift (20–40 mm) occurred along the southern and southeastern parts of the island, while larger magnitudes (> 50 mm) happened at the western part (Paliki Peninsula). These large magnitudes of uplift over an extended area (> 50 km), in conjunction with an accelerated Benioff strain determined from the analysis of the seismicity in the broader region, are consistent with dilatancy. This effect commenced some time after 2003 and is probably centered in the area between Zakynthos and Cephallonia. If this interpretation is correct, it may foreshadow the occurrence of a very strong earthquake(s) sometime during 2007 to 2008 in the above designated region.

Dating of the Giant Huize Zn‐Pb Ore Field of Yunnan Province, Southwest China: Constraints from the Sm‐Nd System in Hydrothermal Calcite

AbstractThe Huize ore field, which is the most famous high‐grade Mississippi Valley‐type Zn‐Pb ore field in China, consists of the Kuangshanchang and Qilinchang deposits. The Sm‐Nd isotopic compositions of gangue calcite were analyzed to constrain the timing of mineralization. Eight calcite samples from the No. 6 orebody in the Qilinchang deposit have Sm and Nd concentrations of 1.82–25.93 and 15.25–79.02 ppm, respectively, and yielded an age of 225 ± 9.9 Ma with epsilon Nd =−10.6 and MSWD = 0.13. Five calcites from the No. 1 orebody in the Kuangshanchang deposit contain 2.37–2.90 ppm Sm and 8.18–16.85 ppm Nd, and yielded an age of 228 ± 16 Ma, with epsilon Nd =−10.6 and MSWD = 0.28. These two ages are close to the age of the Emeishan flood basalt, which is ca 255 Ma, and agree with the reported 40Ar/39Ar plateau and isochron ages of the native copper mineralization related to the Emeishan flood basalt in this region, which are 226–228 Ma. Moreover, previous study shows that the magnitude of uplift resulting from the Emeishan flood basalts is &gt;1000 m. It indicates that the Kuangshanchang and the Qilinchang deposit formed during the same geological event and originated by fluid migration during uplift resulting from the Emeishan flood basalt.

A revision of mid‐late Holocene marine terrace distribution and chronology at the Pakarae River mouth, North Island, New Zealand

A suite of seven marine terraces at the Pakarae River mouth, New Zealand, provide evidence for the highest Holocene coastal uplift rates adjacent to the Hikurangi Subduction Zone. New elevation, coverbed stratigraphy, and age data allow for a timely revision of the distribution, nomenclature, and chronology of these terraces. Terrace correlation primarily is based on the elevation of the wave‐cut strath. Terrace preservation either side of the river is more equal than previously proposed. The age of abandonment of each terrace is c. 7 ka (T1), 4.3 ka (T2), 3.5 ka (T3), 2.89 ka (T4), 1.6 ka (T5), 0.91 ka (T6), and <0.91 ka (T7). The average Holocene tectonic uplift rate at Pakarae is 3.2 ± 0.8 mm/yr. The abandonment of each terrace, from T2 to T7, probably took place after a discrete uplift event. The average time interval between these events is 850 ± 450 yr and the average uplift magnitude is 2.7 ± 1.1 m per event. We infer that uplift has been accommodated by slip on an offshore reverse fault. Normal slip on the Pakarae Fault, at right angles to the margin, occurs at a comparatively slower rate and has probably made little contribution to coastal uplift.

Source parameters of the great Sumatran megathrust earthquakes of 1797 and 1833 inferred from coral microatolls

Large uplifts and tilts occurred on the Sumatran outer arc islands between 0.5° and 3.3°S during great historical earthquakes in 1797 and 1833, as judged from relative sea level changes recorded by annually banded coral heads. Coral data for these two earthquakes are most complete along a 160‐km length of the Mentawai islands between 3.2° and 2°S. Uplift there was as great as 0.8 m in 1797 and 2.8 m in 1833. Uplift in 1797 extended 370 km, between 3.2° and 0.5°S. The pattern and magnitude of uplift imply megathrust ruptures corresponding to moment magnitudes (Mw) in the range 8.5 to 8.7. The region of uplift in 1833 ranges from 2° to at least 3.2°S and, judging from historical reports of shaking and tsunamis, perhaps as far as 5°S. The patterns and magnitude of uplift and tilt in 1833 are similar to those experienced farther north, between 0.5° and 3°N, during the giant Nias‐Simeulue megathrust earthquake of 2005; the outer arc islands rose as much as 3 m and tilted toward the mainland. Elastic dislocation forward modeling of the coral data yields megathrust ruptures with moment magnitudes ranging from 8.6 to 8.9. Sparse accounts at Padang, along the mainland west coast at latitude 1°S, imply tsunami runups of at least 5 m in 1797 and 3–4 m in 1833. Tsunamis simulated from the pattern of coral uplift are roughly consistent with these reports. The tsunami modeling further indicates that the Indian Ocean tsunamis of both 1797 and 1833, unlike that of 2004, were directed mainly south of the Indian subcontinent. Between about 0.7° and 2.1°S, the lack of vintage 1797 and 1833 coral heads in the intertidal zone demonstrates that interseismic submergence has now nearly equals coseismic emergence that accompanied those earthquakes. The interseismic strains accumulated along this reach of the megathrust have thus approached or exceeded the levels relieved in 1797 and 1833.

Cenozoic uplift of Nuussuaq and Disko, West Greenland—elevated erosion surfaces as uplift markers of a passive margin

Remnants of a high plateau have been identified on Nuussuaq and Disko, central West Greenland. We interpret the plateau as an erosion surface (the summit erosion surface) formed mainly by a fluvial system and graded close to its former base level and subsequently uplifted to its present elevation. It extends over 150 km east–west, being of low relative relief, broken along faults, tilted westwards in the west and eastwards in the east, and having a maximum elevation of ca. 2 km in central Nuussuaq and Disko. The summit erosion surface cuts across Precambrian basement rocks and Paleocene–Eocene lavas, constraining its age to being substantially younger than the last rift event in the Nuussuaq Basin, which took place during the late Maastrichtian and Danian. The geological record shows that the Nuussuaq Basin was subjected to subsidence of several kilometres during Paleocene–Eocene volcanism and was transgressed by the sea later during the Eocene. By comparing with results from apatite fission track analysis and vitrinite reflectance maturity data, it is suggested that formation of the erosion surface was probably triggered by an uplift and erosion event starting between 40 and 30 Ma. Surface formation was completed prior to an uplift event that started between 11 and 10 Ma and caused valley incision. This generation of valleys graded to the new base level and formed a lower erosion surface, at most 1 km below the summit erosion surface, thus indicating the magnitude of its uplift. Formation of this generation of valleys was interrupted by a third uplift event also with a magnitude of 1 km that lifted the landscape to near its present position. Correlation with the fission-track record suggests that this uplift event started between 7 and 2 Ma. Uplift must have been caused initially by tectonism. Isostatic compensation due to erosion and loading and unloading of ice sheets has added to the magnitude of uplift but have not significantly altered the configuration of the surface. It is concluded that the elevations of palaeosurfaces (surfaces not in accordance with present climate or tectonic conditions) on West Greenland's passive margin can be used to define the magnitude and lateral variations of Neogene uplift events. The striking similarity between the landforms in West Greenland and those on many other passive margins is also noted.

Pleistocene fluvial systems of the Creuse river (Middle Loire Basin - Centre Region, France) [ Les systèmes fluviatiles pléistocènes de la Creuse (Bassin moyen de la Loire, Région Centre, France).

The Creuse River is a tributary of the Vienne River which joins the Loire Valley on its left bank downstream Tours (Centre Region, France). Recent field works has significantly increased the number of fossil fluvial formations identified in the Middle Creuse River Valley, has confirmed their penglacial character and shown the impact of recent tectonics and the magnitude of uplift which affect the geometry of the deposits on the northern edge of the Massif Central and the southern and western parts of the Pans Basin. Three sectors have been distinguished : - a "Massif Central" sector, with an endogenous bed-rock, where some five stepped higher alluvial formations are studied. - an "Intermediate" sector characterized by the opening of the valley when the river joins the Pans Basin. Eleven sandy formations, which constituted advancing fans in this actively tectonic zone, have been identified. - a "Pans Basin" sector in which the Creuse flows westwards along a major fault. Eight stepped terraces have been recognized here. Several geochronological data were obtained by electronic spin resonance (ESR) method applied to bleached alluvial quartz. The results show a good reproducibihty and generally a good coherence with the altimetry. They indicate, in close correlation with sedimentological and tectonic studies, that the response of the river is variable and depends of local geology and tectonic characteristics. From the results obtained on each sector, a first synthetic but schematic history of the fluvial system can be proposed for the Middle Creuse River valley between 1,7 Ma BP and today Some major tectonic movements are dated between 1,7 and 1,2 Ma, around 600 ka and between 450 and the present. On the other hand, the "Pont-de-Lavaud" Early Palaeolithic site with archaic pebble quartz industry was dated to the end of the Lower Pleistocene, around 1,1 Ma BP.

Inverted basins in the Netherlands, similarities and differences

AbstractAll Dutch rift basins that formed during Jurassic and Early Cretaceous extension have been inverted during the Late Cretaceous and Early Tertiary. Several inversion pulses occurred more or less simultaneously in all basins. Analysis of vitrinite reflectance data, in combination with fission track and fluid inclusion data show that the magnitude of uplift and erosion generally did not exceed 2 km. Inversion was strongest in the Broad Fourteens, Central Netherlands and West Netherlands basins. The direction of maximum compressive stress was generally not at right angles to the pre-existing fault trends, and resulted in transpressional movements. Within the NW-SE striking basins, dextral strike-slip movements can often be interpreted, which is consistent with a general N-S to NNW-SSE direction of maximum compression related to Alpine structural events. Where no Zechstein salt is present, trends of flower structures formed through reverse reactivation of pre-existing faults. Where the Zechstein salt is thick, re-activated faults could not breach the salt, and a broad uplift of the post-salt succession resulted, while faulting below the salt caused acceleration of halokinesis. In areas where the Zechstein salt was thin, and where the offsets of reverse faults exceeded the thickness of the salt, impressive thrusts with the Zechstein salt as detachment horizon developed. The later Tertiary inversion pulses did not affect all basins, and caused broad basin uplift in the West and Central Netherlands basins while individual faults were no longer reactivated. It appears that due to crustal thickening during the first inversion pulses the crust could become stabilised such that further compression could only be accommodated by broad basin uplift.