palinspastic reconstruction and topographic evolution of the eastern alps during late tertiary tectonic extrusion this paper presents a new palinspastic restoration of the eastern alps for neogene time and an attempt to reconstruct the neogene palaeogeology palaeotopography and palaeohydrography in connection with the structural evolution the eastern alps underwent radical horizontal displacement during the neogene due to large strike slip systems and formation of structural windows our palinspastic reconstruction considers a the rearrangement of tectonic units dismembered during tectonic extrusion b the tectonic denudation driven by displacement of the crystalline blocks c geochronological arguments and d the sedimentary record of the syn extrusion basins the rearrangement of tectonic blocks results in a remarkably good fit of highly dismembered zones both in crystalline and sedimentary areas and shows the pre miocene unstretched pattern of the eastern alps reduced to 65 of its present day e w elongation using this structural frame and considering the sedimentary record a set of palaeogeologic and palaeotopographic sketch maps with the palaeo river systems is presented for three time slices pre syn and post extension situation in late oligocene and early miocene times the western eastern alps were already mountainous whereas the eastern part of the orogen formed lowlands or hilly areas enhanced block movement in the course of the extrusion process around the early middle miocene boundary led to the formation of intramontane sedimentary basins and a fault induced reorientation of the drainage pattern which forms the basis of the modern river system in the area east of the tauern window this region where pre miocene land surfaces are preserved probably became a mountainous area not before late miocene time and never reached the elevations of the areas further west

source rocks and hydrocarbon generation in slovenia mura depression pannonian basin abstract source rock analysis organic carbon rock eval gas chromatography vitrinite reflectance and numeric modelling techniques have been applied to evaluate the hydrocarbon potential and the timing of hydrocarbon generation in northeastern slovenia mura depression pannonian basin source rocks of mesozoic age were not detected most tertiary samples are gas prone oil prone sediments occur mainly in egerian eggenburgian karpatian and sarmatian levels the maturity pattern reflects complex neogene subsidence and thermal histories so the thickness of the oil window varies from about 300 m maribor somat area to 1500 m ljutomer depression the top of the oil window lies below a depth of 2500 m in the ljutomer depression whereas it reaches the surface in the maribor area three main hydrocarbon generation phases are distinguished in different parts of the mura depression a a karpatian badenian stage due to extremely elevated heat flow maribor somat radkersburg area boc anticline probably ormoz selnica anticline b a middle late miocene to early pliocene stage due to miocene deep burial ormoz selnica anticline c a late miocene to present generation stage ljutomer depression eastern margin of the murska sobota high

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

depositional environment and sedimentary of the basinal sediments in the eibiswalder bucht radl formation and lower eibiswald beds miocene western styrian basin austria the eibiswald bucht is a small subbasin of the western styrian basin exposing sediments of lower miocene age in the past the entire sequence exposed in the eibiswalder bucht has been interpreted as being of fluvial lacustrine origin here results are presented of detailed sedimentological investigations that lead to a revision of this concept the lowermost siliciclastic sedimentary unit of the eibiswalder bucht sequence is the radl formation it is overlain by the eibiswald beds which are subdivided into the lower middle and upper eibiswald beds the radl formation and the lower eibiswald beds are interpreted as a fan delta complex deposited along nnw sse striking faults based on the sedimentary facies this fan delta can be subdivided into a subaerial alluvial fan facies group a proximal delta facies group and a distal delta prodelta facies group the radl formation comprises the alluvial fan and proximal delta facies groups the lower eibiswald beds the distal delta prodelta facies group the alluvial fan and the proximal delta consist of diverse deposits of gravelly flows the distal delta prodelta consists of wave reworked bioturbated low density turbidites intercalated with minor gravelly mass flows the prodelta can be regarded as as the basin facies of the small and shallow eibiswalder bucht where marine conditions prevailed the basin was probably in part connected with the eastern styrian basin the contemporary depositional environment of the styrian schlier mainly turbiditic marine offshore sediments in the eastern styrian basin analysis of the clast composition in conjunction with the paleotransport direction of the coarse delta mass flows of the radl formation shows that the source rocks were exclusively crystalline rocks ranging from greenschists to eclogites

miocene thermal history of the southwestern margin of the styrian basin vitrinite reflectance and fission track data from the pohorje kozjak area slovenia the kozjak possruck and pohorje mountains form the southwestern basement rim of the neogene styrian basin this region was affected by two tertiary magmatic events the emplacement of the oligocene pohorje tonalite and of early middle miocene dacites in the western pohorje vitrinite reflectance and fission track data are used to reconstruct the thermal history and to constrain the exhumation of the pohorje kozjak area early miocene sediments lacking a thermal overprint contain apatite grains of eggenburgian 19 ma cooling age only 1 2 ma older than the time of deposition the cooling rate of the mainly austroalpine source units was very fast denoting tectonic denudation it means that in the eastern alps during early middle miocene time the pohorje kozjak region in addition to the tauern and rechnitz windows was supplying sediment into the surrounding basins with nearly syn sedimentary apatite cooling ages vitrinite reflectance anomalies in early miocene sediments in the ribnica selnica trough located between the kozjak and pohorje mountains and at the eastern margin of the kozjak mountains give evidence for a strong post depositional thermal overprint thermal models based on nearby wells suggest that miocene temperatures were as high as 220oc apatite fission track ages indicate that the thermal overprint had terminated by middle badenian 14 4 2 3 ma time vitrinite reflectance anomalies in the ribnica selnica trough are a result of early middle miocene volcanic activity another vitrinite reflectance anomaly situated at the eastern margin of the kozjak mountains extends eastward into the somat radkersburg area the heat source in this region is not obvious possible heat sources are 1 a shallow pluton beneath this area which easily can explain the reconstructed early middle miocene heat flow of more than 250 mw m 2 and 2 advective heat transport due to rapid exhumation of hot metamorphic rocks in the pohorje kozjak region rapid exhumation is proven by fission track dating it would explain the appearance of the nearly syn sedimentary detrital apatite ft ages in the sediments and the post depositional heating 1998 elsevier science b v all rights reserved

provenance of the miocene slovenj gradec basin sedimentary fill western central paratethys abstract the slovenj gradec basin represents one of the marginal western basins of the neogene pannonian basin system its sedimentary succession is investigated by combination of field petrographic and geochemical methods the succession is at least 540 m thick and characterised by frequent alternation of conglomerate sandstone siltstone and marlstone deposited in terrestrial brackish and shallow marine environments modal composition of the sandstones indicates that they originated from recycled orogen namely from quartzose sedimentary rocks of the eastern alps and show moderate to absent chemical weathering the results indicate two different tectonic settings a collisional which correlates well with the end mesozoic and cenozoic alpine collision resulting in orogeny and thrusting of the austroalpine nappes and a passive margin related to the early neogene lithospheric extension and subsidence as the result of slab retreat in the carpathian subduction zone which was responsible for the formation of the pannonian basin system in this area where the sediments were subjected to various tectonic events discriminant function diagrams of verma and armstrong altrin are found to be a good tool for their identification and differentiation

subsidence analysis and quantitative basin modelling in the styrian basin pannonian basin system austria abstract we present the results of subsidence analysis and of quantitative basin modelling using isostatical and flexural models for basin evolution along four cross sections in the styrian basin the westernmost subbasin of the pannonian basin system subsidence analysis reveals a first ottnangian karpatian synrift phase our local isostatic models predict crustal stretching values up to 1 3 and subcrustal stretching values of 1 6 for this event stretching factors of a minor sarmatian extension phase are below 1 04 the termination of subsidence during the pannonian and a rapid quaternary uplift phase can be explained by major changes in the regional stress field a w e cross section through the northern furstenfeld subbasin provides a key for the understanding of the dynamics of basin formation it crosses a narrow karpatian rift basin the metamorphic core complex of the penninic eisenberg window and shows an eastward tilting of the easternmost part of the basin during pannonian times uplift of the penninic window can only be modelled with an extremely weak lithosphere equivalent elastic thickness eet 2 km whereas a best fit between observed and modelled tilting is obtained with an eet value of 5 km these results suggest that the lithosphere was extremely weak during the onset of basin evolution in ottnangian karpatian times probably caused by high extension rates and high heat flows associated with karpatian to early badenian magmatic activity subsequent cooling led to a pronounced increase in flexural rigidity an eet of 5 km fits well with estimations in other parts of the pannonian realm depth dependent rheology models based on palaeo heat flow estimates indicate a similar increase in lithospheric strength with time the impact of plio pleistocene volcanism on rheology appears to be relatively modest which can be explained by a deep position of the magma chamber for this event

three dimensional reconstruction of fluvial surface sedimentology and topography using personal mobile laser scanning high resolution quantification of fluvial topography has been enabled by a number of geomatics technologies hyperscale surveys with spatial extents of 1 km2 have been widely demonstrated by means of terrestrial laser scanning tls and structure from motion sfm photogrammetry recent advances in the development and integration of global navigation satellite system gnss inertial measurement unit imu and lightweight laser scanning technologies are now resulting in the emergence of personal mobile laser scanners mls that have the potential to increase data acquisition and processing rates by 1 2 orders of magnitude compared to tls sfm and thus challenge the recent dominance of these technologies this investigation compares a personal mls survey using a leica pegasus backpack that integrates velodyne puck vlp 16 sensors and a multi station static tls survey using a riegl vz 1000 scanner to produce digital elevation models dems and surface sedimentology maps the assessment is undertaken on a 500 m long reach of the braided river feshie comparison to 107 independent real time kinematic rtk gnss check points resulted in similar mean error me and standard deviation error sde for tls me 0 025 m sde 0 038 m and personal mls me 0 014 m sde 0 019 m direct cloud to cloud c2c comparison between a sample of tls and personal mls observations 2 8 million points revealed that c2c distances follows a sharply decreasing burr distribution a 2 35 b 3 19 rate parameter s 9 53 empirical relationships between sub metre topographic variability and median sediment grain size 10 100 mm demonstrate that surface roughness from personal mls can be used to map median grain size differences between tls and personal mls empirical relationships suggest such relationships are dependent on survey technique personal mls offers distinct logistical advantages over sfm photogrammetry and tls for particular survey situations and is likely to become a widely applied technique

holocene aridification of india 1 spanning a latitudinal range typical for deserts the indian peninsula is fertile instead and sustains over a billion people through monsoonal rains despite the strong link between climate and society our knowledge of the long term monsoon variability is incomplete over the indian subcontinent here we reconstruct the holocene paleoclimate in the core monsoon zone cmz of the indian peninsula using a sediment core recovered offshore from the mouth of godavari river carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the cmz and document a gradual increase in aridity adapted vegetation from 4 000 until 1 700 years ago followed by the persistence of aridity adapted plants after that the oxygen isotopic composition of planktonic foraminiferglobigerinoides ruberdetects unprecedented high salinity events in the bay of bengal over the last 3 000 years and especially after 1 700 years ago which suggest that the cmz aridification intensified in the late holocene through a series of sub millennial dry episodes cultural changes occurred across the indian subcontinent as the climate became more arid after 4 000 years sedentary agriculture took hold in the drying central and south india while the urban harappan civilization collapsed in the already arid indus basin the establishment of a more variable hydroclimate over the last ca 1 700 years may have led to the rapid proliferation of water conservation technology in south india

miocene pliocene tectonic evolution of the slovenian periadriatic fault implications for alpine carpathian extrusion models the periadriatic line pal is a remarkable several hundred kilometer long fault system of the alpine orogen its dextral character was documented by several authors using diverse criteria but detailed kinematics and timing of movements had not been investigated along its whole length structural and paleomagnetic measurements mapping and stratigraphic and sedimentological studies have helped to unravel the miocene pliocene evolution of the slovenian segment of the pal brittle deformation was characterized by nw se to n s compression and perpendicular tension deformation has resulted in dextral strike slip faulting folding and tilting of beds the first transpressional event corresponds to the first phase of lateral extrusion of the east alpine western carpathian northern pannonian block in the early miocene 24 17 5 ma after a short period of transtension during the karpatian 17 5 16 5 ma dextral transpression reoccurred during the middle miocene to pliocene and lasted up to the quaternary middle miocene dextral slip can be connected to the second phase of extrusion the highly deformed rocks within the dextral shear zones show variable clockwise sometimes counterclockwise rotations the mechanism of rotation seems to be complex ranging from regional rotation to local folding due to pure or simple shear domino type rotation

formation and spreading of arabian sea high salinity water mass the formation and seasonal spreading of the arabian sea high salinity water ashsw mass were studied based on the monthly mean climatology of temperature and salinity in the arabian sea north of the equator and west of 80 e on a 2 2 grid the ashsw forms in the northern arabian sea during winter and spreads southward along a 24 sigma t surface against the prevailing weak zonal currents the eastern extent of the core is limited by the strong northward coastal current flowing along the west coast of india during the southwest monsoon the northern part of the core shoals under the influence of the findlater jet while the southern part deepens throughout the year the southward extent of the ashsw is inhibited by the equatorial currents the atmospheric forcing that leads to the formation of ashsw was delineated using the monthly mean climatology of heat and freshwater fluxes monsoon winds dominate all the flux fields during summer june september while latent heat release during the relative calm of the winter november february monsoon driven by cool dry continental air from the north results in an increased density of the surface layer thus excess evaporation over precipitation and turbulent heat loss exceeding the radiative heat gain cool the surface waters of the northern arabian sea during winter and drive convective formation of ashsw

holocene benthic foraminiferal faunas in coastal deposits of the nakdong river delta korea and izumo plain japan abstract we documented the holocene benthic foraminifera in the coastal deposits based on drilled cores nd 01 nakdong river delta southeastern korea and hs02 izumo plain southwestern japan the rapid deepening and subsequent gradual shoaling during the holocene were recognized from the stratigraphic distribution of five clusters a to e and the ratio of planktonic foraminifera to the sum of benthic and planktonic foraminifera p t ratio in core nd 01 comparison of benthic foraminiferal faunas indicated that the faunal composition differs somewhat between the nakdong river delta and izumo plain or urauchi bay the east china sea the relationships between mds axis 1 and the rarefaction and between mds axis 1 and the rac kurtosis showed positive and negative linear like trends respectively in both the nakdong river delta and the izumo plain the biotic response of benthic foraminifera to taxonomic loss also seemed to be common in that both coastal deposits experienced shoaling or enclosing of the bay environments despite the different occurrence of benthic foraminifera between the nakdong river delta and izumo plain transient changes of benthic foraminifera in both areas at 8 ka might have been caused by the enhanced influence of the tsushima warm current

thermal history of tertiary basins in slovenia alpine dinaride pannonian junction abstract the transition zone between the alps the dinarides and the pannonian basin was affected by syn collisional magmatism in oligocene time and post collisional lateral escape followed by extreme extension in early and middle miocene times numeric heat flow models for sixteen sites and 650 vitrinite reflectance data from paleogene and neogene sediments were used to evaluate temporal and lateral heat flow variations related to these events oligocene oligocene smrekovec volcanism is the main heat source for paleogene sediments south of the periadriatic lineament vitrinite reflectance patterns suggest dextral displacement along the donat fault of the order of 50 km coalification of paleogene coal bearing sequences south of the pohorje is a result of the emplacement of the oligocene pohorje tonalite early middle miocene extremely elevated early middle miocene heat flow 200 mw m2 occurred in the styrian basin the pohorje area the maribor radgona area and along the boc anticline it is partly a consequence of magmatic activity however no igneous rocks are known from the maribor radgona area a large shallow early miocene pluton could explain the observed miocene heat flow rapid uplift of hot basement rocks in the pohorje kozjak region may have increased surface heat flow neither volcanic rocks nor metamorphic core complexes are known from the boc area the ormo selnica anticline was probably influenced by a middle miocene heating event 150 mw m2 coeval volcanism south of the anticline represents a potential heat source post middle miocene the wsw ene trending ljutomer and radgona depressions are characterized by moderate neogene heat flow 60 75 mw m2 whereas late miocene to present day heat flow in the ormo selnica anticline is 80 90 mw m2 a recent heat flow anomaly occurs in the somat benedikt area

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

geodynamical models of lithospheric deformation rotation and extension of the pannonian basin of central europe article i nfo the two major crustal blocks of the pannonian basin alcapa alpine carpathian pannonian and tisza underwent a complex process of rotation and extension of variable magnitude during the tertiary the northward push of the adriatic block initiated the eastward displacement and rotation of both the alcapa and tisza blocks we have constructed geodynamical models of the rotation and extension of the two pannonian blocks we analyse this process in terms of the competing influences of a ne push by the adriatic block a ne pull from a retreating subduction zone on the eastern carpathians and the internal buoyancy forces arising from crustal thickness variations deformation of the blocks included substantial strike slip movements together with shortening and possible extension across the mid hungarian line which now separates the two domains we use an idealised thin viscous sheet model of the continental lithosphere in which deformation is described by a nonlinear viscous constitutive relationship our approach is based on the finite element method and we consider several distinct models of initial geometry boundary conditions and constitutive parameters rotation and deformation vary across both blocks with anticlockwise rotation occurring in the alcapa plate and clockwise rotation in the tisza block the opposite rotations of the two plates led to nw se convergence in the space between the two intra carpathian terranes subsequently both domains underwent extension dominantly in the ne sw direction extension and internal rotation can be represented using a thin sheet model in which deformation is driven by an east or northeast directed outward traction of order 1 to 3 mpa internal buoyancy forces produced by thick crust from a prior phase of alpine style convergence appear to be a necessary element in the force balance that drives the extension process

palaeogeography subsidence and thermal history of the neogene styrian basin pannonian basin system austria abstract the neogene styrian basin represents an extensional structure on top of a crustal wedge which was moving eastward during the final stages of the alpine orogeny eastward extrusion was a consequence of continental escape and extensional collapse within the eastern alps in a simple model the evolution of the styrian basin can be subdivided into an early miocene ottnangian to karpatian synrift and a subsequent postrift phase basement subsidence rates during the synrift phase reached 30 cm 100 yr and more than 2000 m of limnic to marine sediments were deposited the coincidence of the synrift phase and the formation of pull apart structures along strike slip zones bordering the eastward moving wedge is evidence for the close genetic relation between extrusion tectonics and basin formation a miocene magmatic phase is related to subduction along the carpathian front magmatic activity started during the synrift stage and continued into the postrift stage heat flow in the vicinity of the miocene volcanoes increased dramatically 300 mw m2 a second volcanic phase producing basalts in plio pleistocene times had only little influence on the heat flow pattern limnic to marine sediments of the synrift stage are separated by a major unconformity from middle to late miocene badenian to pontian marine to limnic fluvial postrift sediments sedimentation during the postrift phase was controlled by marine ingressions during middle miocene early badenian and sarmatian times from the south and a subsequent regression with a decline in salinity subsidence rates during the postrift stage were mostly below 2 5 cm 100 yr in pliocene times subsidence was replaced by uplift which resulted in erosion of a few hundred metres of sediment present day high heat flows are a consequence of thinned crust beneath the styrian basin

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

high resolution temperature and evaporation changes during the late holocene in the northeastern arabian sea in order to reconstruct the monsoonal variability during the late holocene we investigated a complete annually laminated sediment record from the oxygen minimum zone omz off pakistan for oxygen isotopes of planktic foraminifera and alkenone derived sea surface temperatures sst significant sst changes of up to 3 c which cannot be explained by changes in the alkenone producing coccolithophorid species inferred from the gephyrocapsa oceanica emiliania huxleyi ratio suggest that sst changes are driven by changes in the monsoon strength our high decadal resolution data indicate that the late holocene in the northeastern arabian sea was not characterized by a stable uniform climate as inferred from the greenland ice cores but by variations in the dominance of the sw monsoon conditions with significant effects on temperatures highest sst fluctuations of up to 3 0 c and 2 5 c were observed for the time interval from 4600 to 3300 years b p and during the past 500 years the significant short term sst changes during the past 500 years might be related to climatic instabilities known from the northern latitudes little ice age and confirm global effects surface salinity values reconstructed from 18o records after correction for temperature related oxygen isotope fractionation suggest that in general the past 5000 years were characterized by higher than recent evaporation and more intense sw monsoon conditions however between 4600 and 3700 years b p evaporation dropped sw monsoon weakened and ne monsoon conditions were comparatively enhanced for the past 1500 years we infer strongly fluctuating monsoon conditions comparisons of reconstructed salinity records with ice accumulation data from published tibetan ice core and tibetan tree ring width data reveal that during the past 2000 years enhanced evaporation in the northeastern arabian sea correlates with periods of increased ice accumulation in tibet and vice versa this suggests a strong climatic relationship between both monsoon controlled areas

progress in paleosalinity overview and presentation of a new approach this paper concerns the use of stable oxygen isotope ratios 18o and stable hydrogen isotope ratios 2h or d to derive paleosalinity first i evaluate the potential and limitations of existing methods based on 18o and d separately next i propose a new theoretical framework for the combined use of 18o and d to constrain the impact of the hydrological cycle on the surface waters and to thus characterize changes in surface water salinity this new method is accompanied by an error propagation exercise to demonstrate its limitations and areas of potential improvement a feasible strategy is outlined for achieving reconstructions of paleosalinity change with an uncertainty of 1 practical salinity unit or less with the newly proposed method especially in regions with high deuterium excess values

holocene reef growth in the maldives evidence of a mid holocene sea level highstand in the central indian ocean radiometrically calibrated ages from three reef cores are used to develop a holocene reef growth chronostratigraphy and sea level history in the maldives central indian ocean last interglacial reef u series age 122 7 ka was encountered at 14 1 m below mean sea level an age of ca 8100 calibrated cal yr b p immediately overlying this pleistocene surface records the initiation of holocene reef growth massive in situ corals occur throughout the cores and the consistency of the three age depth plots indicate that the reef grew steadily between 8100 and 6500 cal yr b p and at a decreasing rate for the next 2 k y the position of modern sea level was first achieved ca 4500 cal yr b p and sea level reached at least 0 50 1 m higher from 4000 to 2100 cal yr b p before falling to present level emergent fossil microatolls provide evidence of this higher sea level results are significant to two long standing issues relating to maldivian sealevel history first the ambiguity of a late holocene highstand has been resolved with clear evidence of its existence reported here second the uncertainty of the regional pattern of sea level change in the central indian ocean has been clarified the maldivian results broadly agreeing with island records in the eastern rather than western indian ocean our results provide the first field evidence confirming geophysical model projections of a highstand 4 2 k y ago in the central indian ocean though the observed level 0 50 0 1 m is lower than that projected

recent benthic foraminiferal assemblages in deep high energy environments from the gulf of cadiz spain the benthic environment in the gulf of cadiz north eastern atlantic is strongly affected by the mediterranean outflow water undercurrent mow which flows northwards along the western iberian margin at 500 1500 m water depth foraminiferal census counts of living and dead assemblages from 27 surface samples ranging from 103 to 1917 m water depth and the examination of hard substrates reveal a close correlation of the fauna with the local hydrography and sediment facies four different faunal groups are separated by factor analysis of the living fauna assemblage 1 contains typical lower slope species and dominates samples from the lower mow core layer and in the north atlantic deep water below shelf edge foraminifera are common in assemblage 2a which shows the highest proportions in samples from 103 to 272 m assemblage 2b is dominated by upper slope species and suspension feeders that are frequent in the upper mow core layer and in distal settings between 396 and 901 m species from assemblage 3 prefer epibenthic habitats and are recorded with high proportions exclusively in the immediate flow paths of the upper mow between 496 and 881 m colonisation structures and species composition of epibenthic assemblages from the proximal facies largely differ from those in distal settings in general epibenthic foraminifers only use elevated substrates under the influence of near bottom flow under high current velocities epibenthic foraminifers prefer large and heavy objects they colonise high attachment levels where a maximum yield of advected food particles can be achieved in distal settings at lower flow velocities the elevation height does not exceed 20 mm above the surrounding sediment surface this level is related to a hydrologic transition layer with high concentrations of suspended particles the comparison of microhabitat preferences and faunal structure under high and low current velocities reveal that substrate stability may be a confining environmental variable for endobenthic and shallow epibenthic foraminifers the observations also indicate that the preferential settling height of epibenthic foraminifera is related to the highest lateral flux rates of food particles within reach from the sea floor a dynamic selection of elevated microhabitats is only used by 7 8 of all species recognised in the gulf of cadiz area

benchmark data of a changing sea palaeogeography palaeobiogeography and events in the central paratethys during the miocene abstract the reconstruction and interpretation of terrestrial ecosystems and vegetational patterns in the central european miocene have to take into account the influence of a vast landlocked water body namely the paratethys sea as a northern appendage of the early mediterranean sea it spanned a north south gradient of at least 4 latitude and has been suggested to represent some kind of palaeothermometer which reflected slight expansions or restrictions of climatic belts due to its vulnerable marine connections it was also highly susceptible to major global sea level fluctuations which are reflected in phases of endemism hence a fairly continuous record of marine nearshore assemblages throughout the miocene reflects an extraordinary interplay of sea level fluctuations changes in climate immigrations and blooms in autochthonous elements whilst biostratigraphic implications of these patterns were recognised early in palaeontology a biogeographic model is still lacking the intermingling of palaeogeographic terms with those restricted to biogeography is still commonly used a situation which can be overcome by integrating data from different biota into a new palaeobiogeographic scheme herein a data set of 1809 species level taxa gastropoda and foraminifera serves as the base for interpretations gastropods in particular turned out to be of greatest value for the differentiation of palaeobiogeographic units due to sensitive reactions to all environmental parameters and occupying a wide range of ecological niches based on the excellent gastropod record the proto danubian province early danubian p danubian p balatonian p and a proto caspian subprovince are defined the biogeographic reorganisations are associated with five major biotic events within the gastropod faunas these big five comprise four extinctions the late ottnangian extinction event loee the mid badenian extinction event mbee the badenian sarmatian extinction event bsee the sarmatian pannonian extinction event spee and one exceptional immigration origination event termed the early badenian build up event ebbe foraminifera are less valuable for palaeobiogeographic purposes in the area and time slice studied endemisms are generally lower and turn over rates less dramatic they are however very useful for stratigraphic correlations with the mediterranean and atlantic areas this fairly well calibrated marine biostratigraphy of the central paratethys serves as stratigraphic backbone and control for continental stratigraphy

geochemistry of sandstones from the upper miocene kudankulam formation southern india implications for provenance weathering and tectonic setting abstract petrographic major trace and rare earth element compositions of sandstones from the upper miocene kudankulam formation southern india have been investigated to determine their provenance tectonic setting and weathering conditions all sandstone samples are highly enriched in quartz q but poor in feldspar f and lithic fragments l the major element concentrations of these sandstones reveal the relative homogeneity of their source geochemically the kudankulam sandstones are classified as arkose subarkose litharenite and sublitharenite the cia values chemical index of alteration mean value 44 5 for these sandstones and the a cn k diagram suggest their low weathering nature similarly their fe2o3 mgo mean 2 7 al2o3 sio2 0 09 k2o na2o 2 2 ratios and tio2 contents 0 3 are consistent with a passive margin setting the eu eu 0 5 la lu cn 21 la sc 5 9 th sc 1 9 la co 5 7 th co 1 8 and cr th 5 3 ratios support a felsic source for these sandstones chondrite normalized ree patterns with lree enrichment flat hree and negative eu anomaly also are attributed to felsic source rock characteristics for kudankulam sandstones total ree concentrations of these sandstones reflect the variations in their grain size fractions the source rocks are probably identified to be proterozoic gneisses charnockites and granites of the kerala khondalite belt which must have been exposed at least since the late miocene finally the unusual ni enrichment in the kudankulam sandstones unaccompanied by a similar enrichment in cr co and v may be related to either the presence of pyrite in the sandstones or more likely the fractionation of garnet from the source rocks during transportation

paleogene retroarc flexural basin beneath the neogene pannonian basin a geodynamic model abstract the neogene middle miocene recent pannonian basin is superimposed on an earlier paleogene middle eocene early miocene basin complex as a result of back arc extension although the stratigraphy of the latter is very well known due to raw material exploration its formation and structural evolution is much less understood a transtensional origin was generally proposed for the paleogene basin of hungary assuming an origin analogous to that of the overlying neogene pannonian basin we suggest an alternative geodynamic scenario for the development of the paleogene basin complex as we think that the observations are better understood in terms of a retroarc foredeep basin model according to this a flexural basin developed south of the backthrust inner west carpathian units the thrust load resulted in a generally deep underfilled flysch basin during middle eocene early oligocene times in the late oligocene early miocene predominantly shallow marine and continental deposition occurred indicating the gradual cessation of thrusting in the adjacent thrust fold belt and the beginning of molasse sedimentation throughout the whole paleogene a shift can be observed of the bathyal dominantly siliciclastic in the axis of the foredeep and neritic partly carbonate in the foreland flank of the foredeep facies belts this migration of the middle eocene early miocene depocenters of the hpb hungarian paleogene basin to the east northeast in present day coordinates is the result of two processes 1 1 the advancement of backthrusting to the southeast 2 2 along strike shift of thrusting to the northeast while a thin skinned thrust front can be reconstructed for the late eocene buda anticline the diosjeno hurbanovo line is interpreted as the result of a major thick skinned thrusting event at the base of the np24 zone 31 ma the subsidence pattern the distinct depositional environments and the structural observations can be more easily integrated into a flexural basin model than into a wrench basin model based on the flexural basin model of this work the early tertiary western carpathians formed a compressional arc while this arc probably developed above a b subduction zone during the late eocene with a corresponding trench magura a forearc basin central carpathian or podhale and a retroarc flexural basin hungarian paleogene from the early oligocene to the early miocene it was characterized by a subduction with a corresponding peripheral foredeep dukla and silesian and a retroarc flexural basin hungarian paleogene

a core top assessment of proxies for the ocean carbonate system in surface dwelling foraminifers we have assessed the reliability of several foraminifer hosted proxies of the ocean carbonate system 11b b ca and u ca using holocene samples from the atlantic and pacific oceans we examined chemical variability over a range of test sizes for two surface dwelling foraminifers globigerinoides sacculifer and globigerinoides ruber measurements of 11b in g ruber show no significant relationship with test size in either atlantic or pacific sites and appear to provide a robust proxy of surface seawater ph likewise there is no significant variability in the 11b of our atlantic core top g sacculifer but we find that 11b increases with increasing test size for g sacculifer in the pacific these systematic differences in 11b are inferred to be a consequence of isotopically light gametogenic calcite in g sacculifer and its preferential preservation during postdepositional dissolution the trace element ratio proxies of ocean carbonate equilibria u ca and b ca show systematic increases in both g ruber and g sacculifer with increasing test size possibly as a result of changing growth rates this behavior complicates their use in paleoceanographic reconstructions in keeping with several previous studies we find that mg ca ratios increase with increasing size fraction in our well preserved atlantic g sacculifer but not in g ruber in contrast to previous interpretations we suggest that these observations reflect a proportionally larger influence of compositionally distinct gametogenic calcite in small individuals compared to larger ones as with 11b this influences g sacculifer but not g ruber which has negligible gametogenic calcite

east west similarities and differences in the surface and deep northern arabian sea records during the past 21kyr abstract this study analyses monsoon proxy globigerina bulloides from ocean drilling program odp hole 723a western arabian sea and hole abp 25 02 northeastern arabian sea as well as dominant benthic foraminifera pteropods total organic carbon toc inorganic carbon ic and stable isotope values of benthic foraminifera from hole abp 25 02 to understand summer monsoon driven changes in the western and eastern arabian sea and their impacts on deep sea ventilation during the past 21 kyr we have also combined published toc data from odp hole 724b to understand if deep sea conditions in the arabian sea were same throughout the region during the studied interval the summer monsoon was generally weaker during cold intervals including the last glacial maximum the younger dryas and the bond events of the holocene from 20 to 10 kyr the deep northeastern arabian sea was better oxygenated with less organic carbon supply except during 14 12 5 kyr when toc values increased indicating a weaker summer monsoon and a weak oxygen minimum zone omz the toc values and the abundance of the eutrophic benthic foraminiferal species bulimina aculeata melonis barleeanum and uvigerina peregrina increased during the late holocene whereas well oxygenated low organic carbon benthic species sphaeroidina bulloides as well as pteropods decreased indicating an intense omz and an increased supply of refractory organic material to the arabian sea it is important to note that although the surface response to monsoon variability was more or less similar in the western and northeastern arabian sea the deep sea conditions show a marked contrast in the two regions during the past 21 kyr

morphostratigraphy and provenance of plio pleistocene terraces in the south eastern alpine foreland the mislinja and upper savinja valleys northern slovenia

phases of compression during the evolution of the pannonian basin and its bearing on hydrocarbon exploration abstract progress in understanding the structural evolution of the pannonian basin is reported this has been driven by the application of seismic stratigraphy constrained by magnetostratigraphic data and the recent release of a great amount of hydrocarbon exploration data this has led to a redefinition and better understanding of the syn rift period and style of rifting in addition a complex structural evolution history during the post rift phase has been recognized two compressive events are defined one in the early stage and another in the late stage of evolution the importance of these findings for hydrocarbon exploration includes an improved knowledge of the timing of trap formations and a possible explanation for remarkably variable reservoir pressures in pools of the great hungarian plain

critical evaluation of six tectonic setting discrimination diagrams using geochemical data of neogene sediments from known tectonic settings abstract an attempt is made to evaluate 6 tectonic setting discrimination diagrams 1 discriminant function and 5 bivariate diagrams frequently used by many researchers for this purpose an extensive database was established for major element geochemistry derived from miocene to recent sand and sandstone medium to fine grained samples collected from a variety of tectonic settings including 1 passive margin pm setting 2 active continental margin acm setting and 3 oceanic island arc oia setting our results suggest that the discrimination fields proposed to infer tectonic settings for six commonly used discrimination diagrams do not work properly for the analyzed miocene to recent sediments the success for these diagrams varies from 0 to about 62 we therefore recommend that these diagrams be used with prudence

early miocene european loess a new record of aridity in southern europe the intercalation of silty units and coarse grained units represented by conglomerates and breccia characterizes a lower miocene terrestrial sedimentary sequence in the north croatian basin a part of the southwestern pannonian basin system these sediments were previously interpreted as alluvial sediments where the silty units would reflect deposition on a floodplain however in this study we show new results that support a different interpretation of the genesis of the silty units the units which vary in thickness between 6 and 180 cm are mostly composed of structureless loose silt they are brownish yellow to yellowish brown in color and do not contain fossils scanning electron microscopy indicated that quartz grains show fracture faces conchoidal fractures v shaped percussion marks linear steps and conchoidal crushing features such microtextures together with the macroscopic characteristics of the silt units indicate that they were deposited by wind therefore this study reports the first occurrence of miocene loess outside of china silt sized particles were probably produced by salt weathering processes on salina type lake flats during long arid periods alluvial deposition was controlled by a more humid climate so the intercalation of eolian silty units with alluvial conglomerates and breccias reflects alternation of arid and more humid periods in the early miocene this agrees with regional paleoclimate studies that show cyclicity in the climate with a dry cycle and orbital scale climate variability controlling paleoenvironmental and sedimentary changes in the area during the early miocene

seasonal variations in foraminiferal flux in the southern ocean campbell plateau new zealand abstract time incremental sediment trap moorings were deployed at two sites across campbell plateau new zealand one in the relatively quiet waters of the plateau interior pukaki rise and the other at the antarctic circumpolar current swept margin eastern campbell flank a continuous record of particle flux over 416 days identifies marked differences in faunal composition and seasonal occurrence in response to these two dynamically different southern ocean settings in the shallow and thermally isolated interior of the pukaki rise site the flux of foraminifera was closely linked to the austral spring pulse of primary production at which time 97 of the total foraminiferal production for the year occurred this seasonal flux of foraminifera at pukaki rise was dominated by the species globorotalia inflata and globigerina bulloides the collapse of phytoplankton production at the end of spring was most likely a result of a co limitation of iron and silicic acid over the deep and dynamic eastern flank of campbell plateau there were four seasonal pulses of foraminiferal flux the largest in spring when almost half of the foraminiferal production occurred most of the spring flux at this site consisted of globorotalia inflata and globigerinita glutinata summer at eastern campbell flank exhibited the lowest flux of foraminifera but the highest species diversity while autumn and winter fluxes were dominated by the deep dwelling globorotalia truncatulinoides although there was only a single pulse of foraminiferal flux at pukaki rise its mass g m 2 d 1 was still greater than that which occurred over the flank summed across all four seasons however the overall standing stock tests m 2 d 1 on the flank was more than twice that which occurred at the pukaki rise site an examination of core top material taken from gravity cores collected in the vicinity of the sediment trap locations revealed typical southern ocean foraminiferal assemblages that were markedly dissimilar in proportion to those observed in the sediment traps

response of shallow sea benthic foraminifera to environmental changes off the coast of goa eastern arabian sea during the last 6100 cal yr bp we have analysed a 6100 year record of benthic and planktonic foraminifera from inner neritic sediments from core sk291 gc13 off the goa coast eastern arabian sea to understand the response of benthic foraminifera to shallow marine processes the benthic foraminiferal assemblage is dominated by nonion cf asterizans ammonia beccarii a gaimardii and virgulinella fragilis which have been selected on the basis of a population of 10 or more in any three samples analysed the planktonic foraminiferal population is sporadic and rare with globigerinoides ruber as the predominant species showing a variable trend the foraminiferal proxies combined with total organic carbon wt and 13 c and 18 o values of ammonia gaimardii suggest distinct variations indicating changes in productivity and salinity in the shallow eastern arabian sea the coastal waters off goa were relatively warmer and less saline between 6100 and 4600 or perhaps to 4200 calibrated years before the present cal yr bp corresponding to a stronger monsoon in south and east asia the shallow sea was cooler from 4200 to 2600 cal yr bp in the study area coinciding with a lower sea surface temperature in the northeastern arabian sea and an arid phase in the indian subcontinent from 2900 to 2600 cal yr bp the study core exhibits the impacts of short term cold events which have earlier been observed in the northeastern arabian sea off pakistan during the little ice age the shallow sea off goa was less productive

relations of petrographical and geochemical parameters in the middle miocene lavanttal lignite austria abstract samples from two lignite seams lower seam upper seam of the lavanttal basin austria and additional xylite were investigated for variations in maceral composition petrography based facies indicators bulk geochemical parameters and molecular composition of hydrocarbons both seams originated in a topogenous mire and evolved within a transgressive setting the final drowning of the mire is indicated by sapropelic shales whereas the sapropelic shale overlying the lower seam was deposited in a freshwater lake the sapropelic shale above the upper seam represents a brackish lake numerous relationships are found between petrography based facies indicators and the geochemical composition of organic matter the contents of macerals of the liptinite group are positively correlated with soluble organic matter som yields and hydrogen index hi consistent with maceral composition and high hi values enhanced proportions of short chain n alkanes which are predominantly found in algae and microorganisms are obtained from samples of the sapropelic shales the final drowning of the mire is reflected by decreasing pristane phytane ratios due to the rise in ground water table and the establishment of anaerobic conditions as well as by decreasing ratios of diasterenes sterenes indicating increasing ph values in the mire the degree of gelification of plant tissue gelification index is governed by the microbial activity in the mire as indicated by the hopanes concentration the differences in floral assemblage during the formation of the lavanttal lignite seams are reflected by major differences in tissue preservation preservation of plant tissue tpi in the lavanttal lignite is obviously controlled by the presence absence of decay resistant gymnosperms in the peat forming vegetation and additionally influenced by the relative contribution of wood to coal formation the results provide evidence that valuable information for coal facies characterization could be obtained by petrography based and geochemical facies indicators an influence of the floral assemblage gymnosperms angiosperms ratio and of the contribution of algal biomass on carbon isotopic composition of the organic matter 13c 24 2 to 28 6 is proposed carbon cycling during biogeochemical decomposition of plant tissue by bacteria is suggested to affect the 13c values of the coal the chemotaxonomical classification of the xylites as gymnosperm remnants based on the molecular composition of terpenoid biomarkers is corroborated by the carbon isotopic composition of the xylites mean 13c 24 1 and the extracted cellulose mean 13c 20 2 the higher isotopic difference of about 3 9 between cellulose and total organic carbon of the xylites compared to the difference between cellulose and wood found in modern trees is explained by the smaller effect of decomposition on 13c of cellulose

the mid hungarian line a zone of repeated tectonic inversions abstract the mid hungarian line is a major tectonic feature of the intra carpathian area separating two terranes of different origin and tectonic structure although this tectonic line was known from borehole records it has not been described in seismic sections the study presents interpreted seismic lines crossing the supposed trace of the mid hungarian line these seismic sections show north dipping normal faults and thrust faults as well as cross cutting young strike slip faults a complex tectonic history is deduced including intra oligocene early miocene thrusting middle miocene extension local late miocene inversion and late miocene pliocene normal faulting and left lateral wrenching in the light of our seismic study we think that the best candidate for the mid hungarian line is a north dipping detachment fault beneath large masses of neogene volcanics the auxiliary structures to the north seen on seismic sections suggest that it moved as a south vergent thrust fault during the palaeogene early miocene which later was reactivated as a set of normal faults the northern alcapa unit overrode the southern tisza dacia unit along this fault zone the same relative positions are observed in the northern termination of the line other structures along the supposed trace of the line are north dipping normal or strike slip faults which frequently were reactivated as smaller thrust faults during the late neogene palaeogene early miocene thrusting along the line might be the result of the opposite tertiary rotations of the two major units as suggested by palaeomagnetic measurements and earlier models

evolution of the south asian monsoon wind system since the late middle miocene abstract the evolution and timing of the inception of the south asian monsoon sam has been one of the most debated climatic mysteries amongst climate workers the himalaya tibetan plateau htp complex has been implicated as the main driver for sam circulation however there are intense debates as to whether there was a critical elevation of the htp complex that drove the sam and at what time such a critical elevation was attained also the role of the htp complex in driving the sam has been questioned in recent climate model studies the model simulation suggests a major intensification of the sam as early as 30 ma whereas marine records from the arabian sea indicate a major strengthening of the south asian summer or southwest monsoon winds between 10 and 8 ma the continental vegetation on the other hand captured a major transition from c 3 to c 4 type during 8 7 ma but whether this change was local or global and whether this transition was driven by monsoonal precipitation is not unanimously accepted our new record from ocean drilling program holes located off the oman margin and on the owen ridge western arabian sea shows appearance of monsoon wind proxy planktic foraminifer globigerina bulloides a significant increase in total organic carbon and a negative shift in stable carbon isotope record of benthic foraminifera at 12 9 ma these proxies indicate that present day south asian monsoon wind system began to develop during the late middle miocene 12 9 ma and summer monsoon was in its full strength in the late miocene 7 ma from 11 to 7 ma the summer monsoon was weaker when winter monsoon was stronger

climate change at the 4 2 ka bp termination of the indus valley civilization and holocene south asian monsoon variability 1 planktonic oxygen isotope ratios off the indus delta reveal climate changes with a multi centennial pacing during the last 6 ka with the most prominent change recorded at 4 2 ka bp opposing isotopic trends across the northern arabian sea surface at that time indicate a reduction in indus river discharge and suggest that later cycles also reflect variations in total annual rainfall over south asia the 4 2 ka event is coherent with the termination of urban harappan civilization in the indus valley thus drought may have initiated southeastward habitat tracking within the harappan cultural domain the late holocene drought cycles following the 4 2 ka bp event vary between 200 and 800 years and are coherent with the evolution of cosmogenic 14c production rates this suggests that solar variability is one fundamental cause behind holocene rainfall changes over south asia

the significance of large sediment supply active tectonism and eustasy on margin sequence development late quaternary stratigraphy and evolution of the ganges brahmaputra delta abstract borehole data from the ganges brahmaputra delta system unveil an intriguing late quaternary history controlled by immense sediment discharge tectonics and eustasy sea level first intersected a major portion of the lowstand surface 10 000 11 000 cal yr bp marking the onset of sediment trapping and delta growth despite rapid sea level rise 1 cm yr sediment load was sufficient to maintain relative shoreline stability during this time by 7000 cal yr bp accommodation was quickly infilled with slowed sea level rise leading to upstream channel migration and widespread dispersal of sands this forced coastal progradation along the western delta front where the ganges was situated and much of the river s fine grained discharge bypassed the subaerial delta and formed a prograding deltaic clinoform on the shelf concurrently brahmaputra sediments were sequestered to an inland tectonic basin thus starving the adjacent shoreline and leading to transgression along the eastern delta by 5000 cal yr bp the two rivers had migrated or changed course to discharge along the eastern delta shoreline which began to prograde into what is now the modern river mouth estuary present delta configuration appears to have developed by 3000 cal yr bp evolution of the tectonically active ganges brahmaputra g b system reveals important similarities and differences with other deltas overall facies succession follows that of basic models progressing from an alluvial valley to coastal marine delta front to a prograding subaerial delta plain however the timing thickness and controls of these deposits differ immense sediment discharge from the ganges and brahmaputra rivers allowed initial delta growth 2000 3000 yr earlier than the global average despite debouching onto a canyon incised high energy margin subsequently a thick 50 m transgressive systems tract was formed during the early holocene phase of delta aggradation contrasting with extensive shoreline retreat documented along most margins highstand progradation of coastal and shelf sequences ensued by the middle holocene but subsiding inland basins also favored accumulation of a thick to 40 m highstand sequence in the lower floodplains unlike many other delta systems subsidence in the subaerial g b delta is not dominated by compaction but rather by plate driven tectonic processes that generate rates up to 4 mm year overall the huge sediment load tectonic subsidence major seismic events and a nearshore canyon system have led to widespread sediment dispersal and sequence formation across the subaerial delta shelf and deep sea bengal fan throughout the late quaternary