Local Uplift Research Articles

Control on Pleistocene shelf drainage by post-Eocene stratigraphy of the Gippsland Basin

The Jemmys Point Formation - uppermost member of the cool-water carbonate Seaspray Group - records a terrestrial drainage system that traversed the now submerged continental shelf of the Gippsland Basin during the latest ice age. A partial network of large sinuous channels that includes a few diffuse areas of arced broadening (probably recording local slack-water lacustrine conditions), has been imaged by aeromagnetic survey data and now large-scale 3D exploration seismic data. Channels are well resolved in narrow-band quadrature phase exploration seismic data by a surface probe that runs along the first zero crossing of the seismic wavetrain. This corresponds closely with the modern-day bathymetric surface when assuming a seawater acoustic velocity of 1,500 m/s.The stratigraphy of these channel features has not been ground-truthed despite the basin being a highly mature and productive petroleum province. In fact, it seems that their distribution is a ‘negative’ of the distribution of petroleum field areas. This fact leads to the consideration of two hypotheses: ongoing structural inversion of existing trapping structures at depth pushes channels away; or intervening zones of relatively high differential compaction subsidence pull channels towards them. No evidence was found to confirm the former hypothesis but this may be because the rate of local uplift does not outpace shelf-wide sedimentation (so cannot be resolved in seismic or seabed bathymetry data). By contrast, the loci of drainage channels appear to correspond well with regions of the thickest post-Eocene stratigraphy. This suggests that differential compaction subsidence has continued to hold the lowstand drainage system in place since a pre-cursor canyon head network was developed by the Mid-Miocene inversion maximum.

Compositional and structural constraints on the geologic history of eastern Tharsis Rise, Mars

Identification and mapping of distinct compositional units using high-resolution orbital imagery of the walls of Valles Marineris, Mars, provide key structural and environmental constraints on the geologic history of the eastern Tharsis Rise. Our results corroborate an overall vertical structure of the upper crust consistent with that inferred from previous studies. An upper unit spectrally consistent with basalt that has variable thickness is overlain on an early to possibly pre-Noachian substrate. The pre-/early-Noachian material is heterogeneous, dominated by low-calcium pyroxene-rich material but ranging locally from feldspathic to and olivine-rich. Aqueous alteration of pre-/early-Noachian rock to dominantly Fe/Mg-smectite is widespread and observed along the chasma walls from −4 to 1km. However phyllosilicates outcrop discontinuously, suggesting that they were emplaced via impact excavation of even older altered material, or formed by non-uniform alteration driven by impact- or magma-related hydrothermal activity. A distinct, higher-temperature alteration assemblage identified by the presence of chlorite, zeolite, and associated carbonate (+/−serpentine) occurs on both the north and south walls of eastern Coprates Chasma in a confined longitudinal band, where the eastern margin of the Thaumasia Plateau intersects Valles Marineris. These secondary minerals are concentrated within a heavily fractured band exposed at a regional tectonic boundary along the margin of the Thaumasia Plateau, and likely record a regional zone of elevated crustal heat flow and fluid circulation. The generally north–south trending band exhibiting this distinct assemblage serves as a tracer for tectonic deformation; its continuity across Valles Marineris is incongruous with previously suggested lateral slip along the margin of a ‘megaslide’, and constrains left-lateral transtensional faulting to less than ∼25–50km. Mapping of compositionally distinct outcrops to the west also reveals localized uplift in western Coprates Chasma, suggesting thrust faults underlying wrinkle ridges. In western Valles Marineris, the upper basalt layer thickens dramatically, supporting either occurrence of a large, infilled basin to the west, or down-dropping and volcanic burial of material near Melas/Candor Chasma, the latter consistent with a constructional origin of the Tharsis Rise.

InSAR observations of the 2009 Racha earthquake, Georgia

Abstract. Central Georgia is an area strongly affected by earthquake and landslide hazards. On 29 April 1991 a major earthquake (Mw = 7.0) struck the Racha region in Georgia, followed by aftershocks and significant afterslip. The same region was hit by another major event (Mw = 6.0) on 7 September 2009. The aim of the study reported here was to utilize interferometric synthetic aperture radar (InSAR) data to improve knowledge about the spatial pattern of deformation due to the 2009 earthquake. There were no actual earthquake observations by InSAR in Georgia. We considered all available SAR data images from different space agencies. However, due to the long wavelength and the frequent acquisitions, only the multi-temporal ALOS L-band SAR data allowed us to produce interferograms spanning the 2009 earthquake. We detected a local uplift around 10 cm (along the line-of-sight propagation) in the interferogram near the earthquake's epicenter, whereas evidence of surface ruptures could not be found in the field along the active thrust fault. We simulated a deformation signal which could be created by the 2009 Racha earthquake on the basis of local seismic records and by using an elastic dislocation model. We compared our modeled fault surface of the September 2009 with the April 1991 Racha earthquake fault surfaces and identify the same fault or a sub-parallel fault of the same system as the origin. The patch that was active in 2009 is just adjacent to the 1991 patch, indicating a possible mainly westward propagation direction, with important implications for future earthquake hazards.

Constraining the timing and provenance of trans-Laurentian transport using Nd and Sm isotopes from Silurian and Devonian marine carbonates

We demonstrate trans-Laurentian transport processes during the late Silurian and Late Devonian via a combination of eolian transport, large rivers traversing up to 3000km, and mid-Laurentian epeiric seawater currents using Nd and Sm isotopes from marine limestone successions. Upper Silurian εNd(425Ma) range from −10.94 to −8.27. Upper Devonian εNd(380Ma) range from −12.83 to −6.44. Negative and absent linear correlations for 147Sm/144Nd versus 143Nd/144Nd for upper Silurian and Upper Devonian samples reflect mixing between older (low εNd) and younger (higher εNd) sources. Upper Silurian samples reflect major contributions from an average Acadian source (higher 143Nd/144Nd and εNd) and the Canadian Shield and/or Transcontinental Arch (low 143Nd/144Nd and εNd). Upper Devonian samples also demonstrate mixing between the Acadian and Canadian Shield/Transcontinental Arch, with minor contributions from proximal ophiolites, arc volcanics, and local uplifts. A compilation of Cambrian-Mississippian εNd(t) data from sedimentary rocks across Laurentia illustrate a transition from older (low εNd) to younger (higher εNd) sources was established in mid-Laurentia by the early Silurian and in western Laurentia by the Middle Devonian. These results suggest that transport of weathered continental material to marine basins is more complex than a simple source-to-sink model, involving contributions from multiple sources over thousands of kilometers of transport from the original source to marine basins.

Morphotectonics of the Tunka rift and its bordering mountains in the Baikal rift system, Russia

The Tunka section of the Baikal rift system presents a uniform alternation of the following neostructural forms: tilted horsts and asymmetrical block uplifts on the northern flank; the central system of the rift valleys; and the arched uplift of the southern flank. This is a standard set of morphostructural elements for the Baikal rift system. The main morphological feature of the Tunka rift is the strong inclination of its floor, ranging from 900m to 200km in general elevation above Lake Baikal. Such traits of recent geodynamics as volcanism, thermal activity, and seismicity are also different from other parts of the rift zone. All of these features of the Tunka rift are related to the deep structure of the rift zone.The peculiarities of the neotectonic structure of the Tunka rift, which are clearly expressed morphologically as is typical of the Baikal rift system, as well as its unique features are in accordance with deep geodynamic processes of the region. On the other hand, the development of the rift basin structures of the southwestern area near Baikal is complicated by inversion deformations. Local uplifts followed by deformations of the basin sedimentary cover and inverted morphostructures expressed in relief are fixed against the background of the general subsidence of blocks of the pre-Cenozoic basement grabens. The Tunka rift has repeatedly experienced inversion deformations throughout its history. The last wave of such deformations involved the southwestern region near Baikal in the second half of the late Pleistocene. During the Quaternary, the positive component prevailed in the whole range of vertical movements of the inter-rift and interbasin blocks; since the late Neogene, these structures have experienced a slow but steady uplift, accompanied by their extension at the expense of the bordering basins.The remote influence of the India-Asia collision on the formation of the southwestern section of the Baikal rift system is very significant and well pronounced in the development of the morphostructural elements of the Tunka rift and its bordering mountains.

Middle-to late-Holocene environmental changes in the Garigliano delta plain (Central Italy): which landscape witnessed the development of the Minturnae Roman colony?

Geomorphologic, stratigraphic, faunistic, palynological and 14C analyses were carried out in the area of the mouth of the Garigliano River characterized by two strand plains that are referred to the Eutyrrhenian and the Holocene, rimming two depressed zones separated by the Garigliano River channel. This study depicts the palaeoenvironmental evolution over the last 8200 years and the landscape context at the time of Minturnae Roman colony. Between 8200 and 7500 yr BP, a wet zone occurred in the northern zone, whereas in the southern part, a lagoon developed. During the final transgression stage and the beginning of the sea level still stand (7500–5500 yr BP), a freshwater marsh formed in the northern zone, and the width of the southern lagoon decreased. Between 5500 and 3000 yr BP, the coastal barrier changed into a delta cusp, a freshwater marsh also appeared in the southern part and the river wandered between the twin marshes. Because of local uplift, previously unknown in this area, part of the floor of the southern marsh emerged, and after 4000 yr BP, both marshes became coastal ponds with prevailing clastic sedimentation. A progressive increment in anthropic forcing on the land took place after 3000 yr BP. The Marica sanctuary was built (7th century BC), and the Roman colony of Minturnae was developed beginning the 3rd century BC. The shallow depth of the ponds prevented their use as harbours, and saltwork plants can be ruled out based on the faunal and palynological data. The ongoing infilling of both ponds was never completed, and their reclamation is still in progress.

A metasomatic setting, the Russian River Arch, and gravitational emplacement in the history of eclogites at the classic eclogite locality of Jenner, California, USA

ABSTRACTBlocks of metamorphic rock designated as ‘high-grade’ blocks, commonly less than 100 m in diameter, consisting of garnet-glaucophane- and hornblende-schists and gneisses and rare eclogite, are widely distributed within mélanges of the Franciscan (accretionary) Complex of California. Eclogite-glaucophane schist blocks present at Jenner, California, have been studied for petrographic, geochemical, structural, and age characteristics, but their relationship to associated Franciscan rocks is poorly understood. The studied blocks are not in situ, but rather occur in landslide deposits and beach sands. The landslide deposits overlie the low to middle slope exposures of sandstone-rich broken formations of the Franciscan Complex that are not known to contain high-grade blocks. Geochemical studies suggest a serpentinite host for the blocks. Upslope, a serpentinite-matrix mélange contains numerous high-grade blocks, including rare retrograded eclogite, and is the likely block source. The Jenner terrain as a whole was uplifted relative to rocks to the north and south near Annapolis and Freestone, respectively, by uplift along the post-Pliocene Russian River (anticlinal) Arch, as indicated by the regional distribution of arching, wave-cut, post-Franciscan surfaces with overlying Miocene/Pliocene marine sedimentary rocks. Local uplift increased landsliding and colluvial downslope movement of the blocks. In addition, local, wave-influenced transportation of smaller blocks, together with the downslope mass movements, brought the high-grade blocks to their present positions. The high-grade blocks are thus displaced from upslope exposures of the original serpentinite-matrix mélange host, in which the blocks likely experienced the metasomatism that converted eclogite to glaucophane schist. In general, the relationship of blocks to the original serpentinite host is a critical element of subduction zone architecture related to subduction zone processes and history, and should be analysed, in any studies that seek to explain the architecture and history of any accretionary complex with similar high-grade blocks.

3-D magnetotelluric image of offshore magmatism at the Walvis Ridge and rift basin

The Namibian continental margin marks the starting point of the Tristan da Cunha hotspot trail, the Walvis Ridge. This section of the volcanic southwestern African margin is therefore ideal to study the interaction of hotspot volcanism and rifting, which occurred in the late Jurassic/early Cretaceous. Offshore magnetotelluric data image electromagnetically the landfall of Walvis Ridge. Two large-scale high resistivity anomalies in the 3-D resistivity model indicate old magmatic intrusions related to hot-spot volcanism and rifting. The large-scale resistivity anomalies correlate with seismically identified lower crustal high velocity anomalies attributed to magmatic underplating along 2-D offshore seismic profiles. One of the high resistivity anomalies (above 500Ωm) has three arms of approximately 100km width and 300km to 400km length at 120° angles in the lower crust. One of the arms stretches underneath Walvis Ridge. The shape is suggestive of crustal extension due to local uplift. It might indicate the location where the hot-spot impinged on the crust prior to rifting. A second, smaller anomaly of 50km width underneath the continent ocean boundary may be attributed to magma ascent during rifting. We attribute a low resistivity anomaly east of the continent ocean boundary and south of Walvis Ridge to the presence of a rift basin that formed prior to the rifting.

Great Lakes Water Levels: Decomposing Time Series for Attribution

Great Lakes water levels have been trending downwards throughout the 20th and into the 21st centuries. Potential causes are numerous. There have been dredging and water diversion projects over the last 110 years, increasing demand for fresh water consumption from a rising population, and considerable variations in environmental factors (rainfall, snowfall, air temperature, and wind), all causal in nature. A thorough assessment of the National Ocean and Atmospheric Administration (NOAA) National Center for Environmental Information (NCEI) and the NOAA National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) — Reanalysis Project (RP) archives of time series of winds, air temperatures, rainfall and snowfall, and water level data, reveals that falling lake levels can be linked to rising air temperatures. Nonuniform, post-glacial, isostatic adjustments of the entire Great Lakes region has further complicated the system as land mass tilting causes localized uplift or subsidence that has also altered relative water levels. A mathematical decomposition of the various data sets and accessory calculations strongly indicate regional atmospheric temperature increases over the entire 20th century and the early 21st century resulting in increased evaporation, appears to be the dominant driving factor in the continued downward trend of water levels in the Great Lakes. Moreover, a high degree of correlation was discovered in comparing water level in the Great Lakes with the comparable temporal variability and record length trends evident both the Global (Land and Ocean) Surface Temperature Anomaly (GSTA) time series and the Atlantic Multidecadal Oscillation (the AMO). It is of note that there have been several water level events since 2013 from which the long term losses of fresh water have undergone a change and the lakes have gained fresh water. This presents an apparent quandary to our nearly 120 year, record length study which revealed downward trends in water levels. To wit, this recent upward movement begs the question: Is the two-year change a precursor to increases in water levels or is it just a local blip? We will focus on data up to 2013, but comment upon recently reported increases as part of our analyses.

A basin-scale perspective on Cenomanian-Turonian (Cretaceous) depositional systems, greater Gulf of Mexico (USA)

Recent exploration discoveries have extended the play fairway for Ceno-Turonian age sandstones from traditional onshore fields into the ultradeep water of the Gulf of Mexico (GOM), necessitating a reevaluation of the basin-scale depositional paleogeography. The Eagle Ford-Tuscaloosa (EFT) supersequence is a long-duration (10 my) aggregate of sand-prone depositional sequences, organic-rich shales, and shallow to deepwater carbonates. Tectonic drivers may help to explain how the Tuscaloosa depositional transport systems were able to surmount the prominent shelf-margin reef barrier that previously trapped so much sand in updip shoreline systems in underlying Lower Cretaceous supersequences. The EFT and underlying Paluxy-Washita supersequences were mapped across the Gulf Basin, from onshore to deep water, using a database of released wells, biostratigraphy, and proprietary 2D seismic data. Mapping reveals a carbonate- and shale-dominated, shallow to deep basin bisected by a sand-prone central corridor with two prominent depositional axes extending toward the Keathley Canyon and Mississippi Canyon protraction areas. Our paleogeographic reconstruction pointed to a large extrabasinal fluvial system with a catchment draining the Appalachians, confirmed by recently published detrital zircon provenance results. An older but underappreciated model for a brief but significant phase of uplift of the Mississippi embayment may explain how the basal sandstone units of the Tuscaloosa prograded and supported a large submarine fan extending more than 500 km (310 mi) from the previous Albian shelf margin. The estimated volumes of sediment generated by the local uplift are at least an order of magnitude too small to explain the deepwater grain volume suggesting related regional extension of drainage catchments during the tectonic event. Our work reveals the extent of a large sand fairway with an areal size, fan run-out length, and reservoir volume comparable in some respects with the hydrocarbon-rich Paleogene (Wilcox) in the central GOM.

Detrital zircon provenance of the Paleogene syn‐rift sediments in the northern South China Sea

AbstractThe early rift sedimentation history of the South China Sea is still not well understood due to restricted borehole coverage of the Paleogene strata and lack of reliable stratigraphic dating. We use detrital zircon U‐Pb geochronology to explore the source‐to‐sink characteristics of syn‐rift sequences in the northern South China Sea. The results reveal significant intrabasinal provenances in addition to the well‐perceived terrigenous supply from the north. The Dongsha Uplift is considered to account for the dominance of the Early Cretaceous zircons in the Eocene samples. The Lower Oligocene sediments in the Qiongdongnan Basin could have been sourced from Hainan Island and local uplifts, but their distinction cannot be confirmed by the U‐Pb age spectra. Contemporary sediments in the northern Pearl River Mouth Basin were most likely transported from southeastern South China with well‐rounded zircon grains showing U‐Pb age similarity to those from the northeastern tributaries of the Pearl River. By contrast, intrabasinal sources from the west and east are suggested to have contributed the infill of the southern part of the Pearl River Mouth Basin based on generally euhedral zircon shapes. These sedimentary source patterns appear to change very little in the Oligocene northern South China Sea. However, the newly detected Neoproterozoic zircons in the Upper Oligocene sediments from borehole L21 tend to indicate a southern source. The episodic and diachronic nature of rifting and erosion processes in the early South China Sea is the cause of complex patterns in the Paleogene provenance history.

Continuous record of Holocene sea-level changes and coastal development of the Kattegat island Læsø (4900 years BP to present)

Læsø is the largest island of the Kattegat–Skagerrak region and exposes a vast array of relative sealevel (RSL) indicators, mainly raised beach ridges, swales, lagoons and saltmarshes. The physical environment of continuous glacial rebound, excessive supply of sediment, shallow surrounding waters, low amplitudes of near-shore waves, and micro-tidal conditions produced numerous sealevel proxies of both barrier coasts and saltmarshes. About 1200 RSL/age index points reflect not only short-term sea-level highstands as in most other parts of Europe, but also short-erm sea-level lowstands, which in less regressive environments have normally been removed by coastal erosion or obscured by berms from subsequent highstands. Based on a high-precision lidar digital terrain model, the beach ridges have been mapped, typified, levelled and correlated relative to their order of appearance. Transformation of this relative chronology to a robust absolute age model of the RSL changes has been made on the basis of 119 optically stimulated luminescence (OSL) datings, 14C datings, and tree-ring datings. By ground penetrating radar (GPR) and terrain analyses, the height of the swash zone (run-up) has been determined in order to transform the ridge elevations to a detailed curve of the RSL/age relation. The curve reveals eight centennial sea-level oscillations of 0.5–1.1 m superimposed on the general trend of the RSL curve, including a Little Ice Age lowstand of 0.6 m at 1300 AD. The island grew from now eroded landscapes of Weichselian glacio-marine deposits, including the oldest known post-Weichselian forested area in Scandinavia. During the last 4900 years new coastal landscapes have formed continuously, resulting in around 4000 km of still visible, raised palaeo-shorelines in mostly uncultivated landscapes. After formation of the oldest preserved beach-ridge complex, numerous sea-level proxies formed in a strongly regressive environment caused by glacial rebound supplemented with local uplift due to extensive erosion during Boreal and Atlantic time of the 1700 km2 glacio-marine platform upon which the island is still being built. The combined uplift produced a relative sea-level fall of 10.3 m, corresponding to a mean vertical regression rate of 2.1 mm/year and a mean horizontal regression rate of 2 m/year, and formed eight distinct types of raised coastal landscapes where well separated beach ridges and saltmarshes developed continuously. The oldest preserved part of Læsø appeared 4900 years BP as the eastern tip of a 10 km long barrier-spit system growing from a raised glacio-marine landscape, now represented only by boulder reefs west and north-west of the present island. Around 4000 years BP another barrier-spit system appeared to the south, growing northwards from another raised glacio-marine landscape at the raised boulder reefs in the town of Byrum and the abrasion landscapes of Rønnerne. Around 3000 years BP these two inital barrier-spit systems united and formed one major barrier between the present towns Vesterø and Byrum. To the north-east, a third glacio-marine landscape provided materials for the development of the eastern end of the island. Thus, around 2500 BP the island had become one triangular, completely detached island (’the old triangle’) between Vesterø, Byrum and Bansten Bakke. From this detached stage, nine subsequent barrier-spit systems grew to the east and formed the present Østerby peninsula, while a series of nine barrier-island complexes developed south-west of ’the old triangle’. To the south and south-east, low-energy coasts developed and formed low beach ridges and saltmarsh landscapes.

The Role of Surface Processes in Partitioning of Strain and Uplift, St. Elias Orogen, Southern Alaska

<span style="font-size: 10.5pt; font-family: 'Times New Roman','serif'; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;" lang="EN-US">Three-dimensional thermo-mechanical numerical simulations of the ongoing Yakutat–North America collision are used to identify the role of surface processes in triggering localized rapid uplift, exhumation, and strain observed within the St. Elias orogen of southern Alaska. Thermochronological data reveal localized rapid exhumation associated with the Seward-Malaspina and Hubbard Glaciers within a tectonic corner structure where transpressional motion to the south along the Fairweather Fault system transitions to shortening to the north and west within the active fold-and-thrust belt of the St. Elias orogen. The modeled deformation patterns are characteristic of oblique convergence within a tectonic corner, recording the transition from simple shear to contractional strain within a zone spatially consistent with the highest exhumation rates suggesting the corner geometry is the primary control of strain partitioning.</span><span style="font-size: 10.5pt; font-family: 'Times New Roman','serif'; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;" lang="EN-US">The relative roles of surface-related processes versus tectonics-related processes in the development of this pattern of deformation were tested with the inclusion of an erosional surface model. The presence of surface processes enhanced the uplift and development of a localized rapid exhumation. When spatially and temporally erosion models are employed, the location of maxima is shifted in response. This indicates that efficient erosion, and resultant deposition and material advection can influence the localization of strain and uplift.</span>

Analyzing the effect of large rotations on the seismic response of structures subjected to foundation local uplift

This work deals with seismic analysis of structures by taking into account soil-structure interaction where the structure is modeled by an equivalent flexible beam mounted on a rigid foundation that is supported by a Winkler like soil. The foundation is assumed to undergo local uplift and the rotations are considered to be large. The coupling of the system is represented by a series of springs and damping elements that are distributed over the entire width of the foundation. The non-linear equations of motion of the system were derived by taking into account the equilibrium of the coupled foundation-structure system where the structure was idealized as a single-degree-of-freedom. The seismic response of the structure was calculated under the occurrence of foundation uplift for both large and small rotations. The non-linear differential system of equations was integrated by using the Matlab command ode15s. The maximum response has been determined as function of the intensity of the earthquake, the slenderness of the structure and the damping ratio. It was found that considering local uplift with small rotations of foundation under seismic loading leads to unfavorable structural response in comparison with the case of large rotations.

Great Lakes Water Levels: Decomposing Time Series for Attribution

Great Lakes water levels have been trending downwards throughout the 20th and into the 21st Centuries. Potential causes are numerous. There have been dredging and water diversion projects over the last 110 years, increasing demand for fresh water consumption from a rising population, and considerable variations in environmental factors (rainfall, snowfall, air temperature and wind), all causal in nature. A thorough assessment of United States federal agency and laboratory data archives of time series of winds, air temperatures, rainfall and snowfall, and water level data, reveals that falling lake levels can be linked to rising air temperatures. Non-uniform, post-glacial, isostatic adjustments of the entire Great Lakes region has further complicated the system as land mass tilting causes localized uplift or subsidence that has also altered relative water levels. A mathematical decomposition of the various data sets and accessory calculations strongly indicate regional atmospheric temperature increases over the entire 20th century and the early 21st century resulting in increased evaporation, is the dominant driving factor in the continued downward trend of water levels in the Great Lakes. Moreover, a high degree of correlation was discovered in comparing water level in the Great Lakes with the comparable temporal variability and record length trends evident both the Global (Land and Ocean) Surface Temperature Anomaly time series and the Atlantic Multi-Decadal Oscillation. It is of note that there have been several water level events since 2013 from which the long term losses of fresh water have undergone a change and the lakes have gained fresh water. This received a great deal of attention in both the public press and a scientific newsletter and shows that there is a danger in only dealing with a small portion, 2 years, of a 120 year climate record.

Paleofluid Evolution In Fault-Damage Zones: Evidence From Fault–Fold Interaction Events In the Jabal Qusaybah Anticline (Adam Foothills, North Oman)

Abstract Fault zones are known to play a key role in controlling fluid migration, including hydrocarbons, at local and regional scales. In this contribution physicochemical data from veins are used to document the extent and maintenance of fluid conductivity associated with fault-damage zones in an anticlinal structure occurring in the frontal part of a foreland fold and thrust belt. Migration of fluids during major deformational events has been recorded by several generations of calcite and localized dolomite cementation in veins in marine Cretaceous carbonates of the Jabal Qusaybah Anticline (North Oman). Applying detailed petrographic and paragenetic relations, geochemical analysis (stable carbon and oxygen isotopes, strontium isotopes, and trace elements), and microthermometry, coupled with structural studies of fault zones and associated calcite veins, made it possible to link fluid circulation to the structural evolution of the Jabal Qusaybah Anticline. Based on the structural framework and fault systems, three groups of veins were distinguished. Group 1 veins are interpreted to be linked to burial and early-tectonic deformation in association with E–W extensional fault zones. Calcite cementation in this group occurred in a closed to semiclosed fluid system, which originated as a result of intraformational fluid movement along a low-connectivity fracture network. The δ13C values of these veins range from 3‰ to 3.5‰, and δ18O values vary from –10.3 to –8.1‰ V-PDB. Group 2 veins are related to syntectonic deformation along NE–SW strike–slip and incipient N–S extensional faults linked to culmination of the Jabal Qusaybah Anticline. From this stage onward, fluids correspond to progressive fault connectivity and dilation related to interaction of fault–folding systems. The cements precipitated during this stage have more variable δ13C values ranging from 0.9 to 3.2‰ and possess a wide range of δ18O values varying between –11.2 and 0.3‰ V-PDB. The cements in Group 2 veins originated from fluids characterized by a relatively broad range of precipitation temperature (75–107°C) and salinities evolving from seawater to moderately saline fluids (3.4–12.8 eq. wt% NaCl), with H2O–NaCl composition. The source of salinity is inferred to be evaporitic brines that originated from the Ara Group, and the large range of salinity is interpreted as the result of mixing between those brines and modified seawater. Group 3 veins are considered to be related to late–tectonic deformation corresponding to late fold amplification of the anticline hinge, transition from NE–SW left-lateral strike–slip to N–S extensional faulting, progressive regional and local uplift, and exhumation. Stable-isotope data support the occurrence of bacterial methanogenesis or CO2 degassing at the end of this stage. Their associated cements are characterized by higher δ13C and δ18O values compared to other groups of veins, ranging from 0.6 to 8.0‰ and –3.6 to 1.5‰ V-PDB, respectively. Fluids responsible for calcite precipitation in this group evolved from a moderate saline to a more saline (8.5–16 eq. wt. % NaCl) H2O–NaCl–CaCl2 brine. The progressive 18O enrichment relative to seawater and preceding cements and its covariation with fluid salinity in the later stage suggest the higher contribution of the evaporitic brines. This hypothesis is further supported by the increase in their 87Sr/86Sr ratios compared to both middle to Upper Cretaceous marine carbonates and other groups of veins. Although during this episode calcite cementation occurred at temperatures below 50°C, their geochemical signatures reveal that the faults were sufficiently conductive to transfer extraformational fluids late in the deformation history of this structure. The interference between strike-slip and extensional fault systems and their interaction with fold amplification is invoked to be responsible for enhanced conductivity in fault-damage zones.

Middle–late Pleistocene marine molluscs from Izmit Bay area (eastern Marmara Sea, Turkey) and the nature of Marmara – Black Sea corridors

In this study, marine Pleistocene mollusc faunas from deposits along the southern shores of the Izmit Bay area (Marmara Sea, Turkey) are reviewed. Ten samples from five localities spanning middle and late Pleistocene intervals are assessed and compared to four samples of a Holocene age. For the Pleistocene fauna, a total of 59 mollusc species (33 bivalve and 26 gastropod species) are recorded, some of which are reported for the first time for this region. The middle Pleistocene fauna bears large resemblance to the late Pleistocene faunas, even though marine conditions were lacking during sea-level drops in the Marmara Sea Basin in intervening times. The middle Pleistocene mollusc fauna is dominated by species that typify the so-called Uzunlarian faunas while the late Pleistocene mollusc fauna is indistinguishable from Karangatian faunas of the Black Sea Basin.Several common species (including Bittium reticulatum, Rissoa spp. and Lucinella divaricata) show that the both Uzunlarian and Karangatian assemblages of Yalova fauna mainly represent seagrass palaeoenvironments. Palaeosalinities estimates for the Yalova area are uppermost mesohaline to polyhaline, typically around or above 20 psu, which is almost similar to the optimum salinity estimates for the middle Pleistocene Uzunlarian. However, it is slightly lower then the Upper Pleistocene Karangatian, representing the location of the Yalova area in an embayment with freshwater input at that time.The Yalova sections are located in the southern flank of the North Anatolian fault system responsible for a strong local uplift of the study area. The sections contain evidence for three marine high stands, separated by terrestrial intervals. When regional uplift rates (approximately 0.2 mm/y) and oceanic sea-levels are considered it is likely that the three highstand intervals correspond to relative sea level high stands of MIS7, MIS5e and possibly MIS5d but further study is required to confirm such a suggestion.

Cenozoic tectonic evolution of Liaodong dome, Northeast Liaodong Bay, Bohai, offshore China, constraints from seismic stratigraphy, vitrinite reflectance and apatite fission track data

The Liaodong dome is a region of localized uplift and deformation within the Liaodong Bay, Bohai, offshore China. 3-D seismic dataset, vitrinite reflectance and apatite fission track data provide an exceptional opportunity to document the evolution of the Liaodong dome which developed coeval with the Tan-Lu strike-slip fault zone with a rift system. The 3-D seismic data demonstrates that the dome formed before the deposition stage of EsM sequence (40Ma), and it uplifted again during or after the depositional stage of Ed sequence (32-24Ma). Apatite fission track and vitrinite reflectance data indicate that the dome experienced two stages of cooling episodes, Paleocene to Early/Middle Eocene (65–40Ma) and Late Oligocene to Late Miocene (30–11.5Ma), usually indicating uplifting. Both the seismic stratigraphy and thermal history analysis show that: 1) the Liaodong dome is part of the Jiaoliao terrane; 2) regional continental rifting climaxed during 65–40Ma, as it did the rift-shoulder uplift of the dome; 3) the reactivation of the Tan-Lu fault caused a second uplift processes of the Liaodong dome during 30–11.5Ma; 4) the Liaodong dome uplifted independently and separated from the Jiaoliao terrane. Our results also suggest that it is important to take uplifting evolution into consideration to target a potential petroleum reservoir.

New data on the structure of Permian-Triassic Complex of the Ustyurt Plateau, Uzbekistan

The tectonic features of the Permian-Triassic Complex in the Ustyurt Plateau are considered on the basis of up-to-date seismic exploration methods against the background of a regional structural review. The peculiar structural style of the complex under consideration is characterized by the following attributes: the widespread Permian-Triassic faults that control block tectonics; the leading role of grabens various in morphology among negative paleostructures; the critical role of pre-Upper Permian rejuvenated faults in localization of grabens; the predominant extension of the Earth’s crust during origin and development of grabens and subsequent shortening; the appearance of an inversion of the Permian-Triassic graben, deepest in region; the posthumous local uplifts formed in Permian-Triassic and Jurassic-Cenozoic. The morphological typification of graben-like paleotroughs of the transitional stage has been proposed. This stage predates typical platform regime at the young platforms.

Seismicity on the western Greenland Ice Sheet: Surface fracture in the vicinity of active moulins

We analyzed geophone and GPS measurements collected within the ablation zone of the western Greenland Ice Sheet during a ~35 day period of the 2011 melt season to study changes in ice deformation before, during, and after a supraglacial lake drainage event. During rapid lake drainage, ice flow speeds increased to ~400% of winter values, and icequake activity peaked. At times >7 days after drainage, this seismicity developed variability over both diurnal and longer periods (~10 days), while coincident ice speeds fell to ~150% of winter values and showed nightly peaks in spatial variability. Approximately 95% of all detected seismicity in the lake basin and its immediate vicinity was triggered by fracture propagation within near-surface ice (<330m deep) that generated Rayleigh waves. Icequakes occurring before and during drainage frequently were collocated with the down flow (west) end of the primary hydrofracture through which the lake drained but shifted farther west and outside the lake basin after the drainage. We interpret these results to reveal vertical hydrofracture opening and local uplift during the drainage, followed by enhanced seismicity and ice flow on the downstream side of the lake basin. This region collocates with interferometric synthetic aperture radar-measured speedup in previous years and could reflect the migration path of themeltwater supplied to the bed by the lake. The diurnal seismic signal can be associated with nightly reductions in surface melt input that increase effective basal pressure and traction, thereby promoting elevated strain in the surficial ice.