late holocene coastline and landscape changes to the west of ephesus turkey abstract palaeogeographical research regarding coastline and landscape changes has been conducted in the kucuk menderes graben and the environs of the ancient city of ephesus in western turkey for a few decades based on geophysical data multi proxy and microfaunal analyses of sediment cores 14 c ams age estimates and diagnostic ceramics this study presents for the first time results of an area close to the present coastline where a byzantine church is located on top of a small hill the results reveal that this mica schist hill turned into an island during the 2nd 1st millennium bce it was reconnected to the mainland via a tombolo during the 5th century ce drill cores and geophysical measurements surrounding the hill show massive stone layers which were deposited intentionally during the 5th 6th century ce when the byzantine church was built geophysical images point to wall structures in the surroundings of the hill the area to the northeast hosts a small harbour site when the coastline continued to shift further to the west this site was still connected to the sea by the kucuk menderes river

quaternary deposits of the buyuk menderes graben in western anatolia turkey implications for river capture and the longest holocene estuary in the aegean sea abstract the buyuk menderes graben is a seismically active depositional basin in the n s extensional tectonic region of western anatolia turkey it extends in an e w direction and is bounded by the aegean sea to the west the infill of this tectonic basin comprises ca 850 m and 245 m thick clastic sequences of neogene and quaternary respectively and the quaternary part of the basin fill is presented here by the help of seismic sections and boreholes results show that the studied succession was made of unconsolidated mostly fine grained clastic sediments of marine and continental sequences interfingered with each other the marine counterpart forms three relatively short approx 30 km and one long approx 100 km from modern coastline sediment wedges representing sea transgressions onto the graben the last one was a rapid incursion that occurred in the middle holocene forming the longest estuary of the aegean sea in western anatolia the filling of this estuary caused the decline of some historical harbours and settlements in the region while marine based events occurred in the west of the graben alluvial and fluvial processes produced marginal and axial deposits in the east of graben respectively in general the continental succession of quaternary is thinner than its marine equivalent probably due to sea level fluctuations in addition the sedimentation rate increased suddenly during deposition of the last marine sequence estuarine deposits in the holocene it is likely that this was the result of enlargement of the drainage area of the river buyuk menderes due to a river capture that occurred in the latest stages of pleistocene

paleoglacial records from kavron valley ne turkey field and cosmogenic exposure dating evidence abstract kavron valley lies in the kackar mountain range of northeastern anatolia and is a north south oriented typically u shaped glacial valley consisting of a main and three tributary valleys the quaternary units that outcrop in this valley have been mapped and 22 samples have been processed for surface exposure dating using cosmogenic 10 be according to the 10 be ages the advance of the kavron paleoglacier began at least 26 0 1 2 kyr ago with the last glacial maximum lgm advance continuing until 18 3 0 9 kyr after this time the kavron paleoglacier receded although the magnitude of this recession is still unknown subsequent to this retreat the glacier most probably separated into three smaller glaciers that were restricted to the tributary valleys ifrit derebasi and mezovit paleoglaciers the main valley was definitely ice free by 15 5 0 7 kyr ago with the mezovit paleoglacier completing its recession around 15 5 0 6 kyr a late glacial advance took place around 13 0 0 8 to 11 5 0 8 kyr and little ice age moraines appear to be absent our results from the kavron valley system seem to be consistent with the lgm paleoclimate record of anatolia which has been delineated by data gathered from lowlands and lakes the deposition of red clay layers in the northwestern black sea and the deposition of heinrich 1 layers in the north atlantic

late holocene human environmental interactions in the eastern mediterranean settlement history and paleogeography of an ancient aegean hill top settlement abstract interactions between settlement history and landscape evolution of a hill top settlement on the west anatolian coast near ancient pergamon modern bergama were studied by a combination of archaeological and geographical investigations ceramics ancient literary and epigraphic texts numismatics and architectural remains show that the hill top had been populated since late bronze age times from the sixth century bc until the change of the eras the hill was occupied by a greek polis atarneus and was abandoned afterwards it was newly populated in the second half of the twelfth and the first half of the thirteenth century ad the lithostratigraphy of nine drilling cores arranged in three transects and dated by ams radiocarbon dating shows that during the past 4000 years the sedimentary plains surrounding the settlement hill were aggraded by braided and meandering rivers while colluviation and alluvial fan deposition occurred at the foot slopes sedimentation totaled about 5 7 m in the past 4000 years evidencing a drowning of the landscape in terrestrial sediments although channels shifted repeatedly and alluvial fan deposition fluctuated the depositional system did not change in general during the past 4000 years this striking resistance to the changing settlement and land use intensity is an effect of the distinct modification of the slopes through terracing that countervailed erosion and likewise increased the buffering capacity of the sediment storages on the slopes there is no evidence that landscape deterioration contributed to the abandonment of the settlement hill rather socio economic factors were crucial for the rise and fall of the settlements occupying the hill

geoscience of ancient mediterranean harbours abstract although much has been written on the subject of ancient mediterranean harbours the relatively new area of harbour geoarchaeology remains dispersed in the geoscience and archaeological literature over a decade of research has amassed rich and varied datasets of anthropogenically forced coastal evolution with a remarkable number of between site analogies this new research field also shows the rich potential of geoscience to reconcile important archaeological questions no single publication however has yet drawn on these geological patterns to yield a detailed overview suitable for geoscientists and environmental archaeologists the aim of this review article is to 1 discuss how ancient harbours have come to be preserved in the geological record 2 expound the basic principles and palaeoenvironmental tools underpinning ancient harbour geoarchaeology 3 outline some of the most significant research advances made and 4 discuss a new chrono stratigraphic model applicable to harbour sequences

magnetic properties of granitic rocks from the southern half of the idaho batholith influences of hydrothermal alteration and implications for aeromagnetic interpretation the measured magnetic susceptibilities of rocks from more than 600 outcrops in the southern idaho batholith have a good spatial correspondence with the observed intensities of magnetic anomalies koenigsberger ratios are low 0 3 in 75 of cored samples indicating that remanent magnetizations are unimportant relative to induced magnetizations which are related to susceptibilities in aeromagnetic anomaly interpretations in this region extremely low susceptibilities 25 10 5 within the eastern and western parts of the batholith are the sources of positive aeromagnetic anomalies the associated lithologies include mesozoic tonalite and granodiorite as well as a diverse tertiary group of epizonal stocks and batholiths intense meteoric hydrothermal activity associated with the emplacement of these tertiary plutons caused a reduction in in some rocks although coarse igneous magnetite is surprisingly resistant to hydrothermal corrosion and oxidation however under conditions of lower water rock ratios a significant increase in commonly occurred in the leucocratic plutons generally reflecting growth of hydrothermal magnetite because the measured susceptibilities do not necessarily represent more than the uppermost part of the 14 to 20 km thick crust that gives rise to magnetic anomalies an apparent discordance between susceptibility measurements and susceptibilities inferred from aeromagnetic data can occur such discordance patterns occur near the margins of the batholith where granitic rocks are thin and also in hydrothermally altered regions where subsurface tertiary plutons are present magnetic models suggest that the idaho batholith thickens to 20 km in its east central part which is underlain by enormous tertiary intrusive bodies

human influence and the changing geomorphology of mediterranean deltas and coasts over the last 6000 years from progradation to destruction phase the present geomorphology of the mediterranean s coasts is largely a product of an intricate long term relationship between nature and human societies a cradle of ancient civilisations the mediterranean has seen its shores occupied by humans since prehistory and is therefore a particularly pertinent unit of analysis the morphotectonic context and other forcing agents e g climate shaped out a highly diversified coastal morphology and generated a sediment supply regime potentially favourable to the formation of numerous open coast deltas and bay head deltas in infilled rias as sea level stabilised during the mid holocene this supply of riverine sediment has also been the key agent in mediating human occupation of the mediterranean s clastic coasts expressions of this relationship have been extensively archived in clastic coastal deposits including base level deltaic and estuarine sedimentary sinks which comprise records to explore the interactions between geosystems and the human environment the stratigraphic sequences in these coastal sedimentary archives comprise in many places a clearly identified anthropogenic signature notably in ancient harbours some of which underwent extremely rapid silting up due to massive sediment sourcing generated by new agricultural practices from the neolithic onwards increasing human influence especially over the last 3000 years has been in turn an important driver of changes in sediment supply strongly modulating deltaic development pulses of sediment supply from catchments rendered vulnerable by human perturbations during the roman period resulted in a new cycle of inception of many other deltas and in rapid delta growth e g the ebro the po the arno and the ombrone another progradation dynamic during the little ice age at a time of strong rural population growth river discharge increases technological developments and urbanisation further consolidated delta growth understanding the life cycle of these deltas since their initial formation is in turn key to unravelling the relative role of natural and anthropogenic forcing agents rapid climate changes are deemed to have contributed through both the stripping of landscapes rendered fragile by human activities and active fluvial sediment transport to the coast but disentangling climate change effects from human impacts in the mediterranean remains a challenge the patterns of subsequent deltaic growth and delta morphodynamics reflect adaptations to pulsed sediment supply river discharge variations the microtidal fetch limited context of the mediterranean and direct engineering interventions the progradation dynamic of the roman period and little ice age contrasts markedly with the situation of common coastal destabilisation over the last two centuries particularly well documented for the last 50 years this period has been characterised by reduced sediment flux to base level geosystems due to catchment reforestation retenion within reservoirs fluvial regulation and dredging resulting in the erosion of deltas and barrier lagoon and beach dune systems large stretches of shoreline and narrow coastal plains have been massively engineered for coastal defence and protection against erosion but also for the construction of marinas leisure harbours and artificial beaches resulting in the emergence of veritable artificial seafronts these interventions have collectively and progressively raised societies to a pervasive and overarching position in the geomorphic stability instability of the mediterranean s coasts a situation that will be exacerbated by pressures from sea level rise paving the way for rampant coastal erosion and delta destruction

steady state secondary convection beneath lithospheric plates with temperature and pressure dependent viscosity we have constructed a thermomechanical model for upper mantle convection such that the thickness and structure of the lithosphere are determined self consistently by the heat transported by convection in this study of the interaction between the lithosphere and upper mantle strongly temperature and pressure dependent rheologies for both newtonian and non newtonian creep mechanisms are employed for a strictly temperature dependent rheology an insignificant amount of heat less than 12 5 mw m2 can be transported convectively for an interior viscosity 0 1021 pas compatible with postglacial rebound on the other hand for similar values of the interior viscosity steady heat fluxes between 20 and 40 mw m2 are produced by introducing pressure dependence into the rheology for the temperature and pressure dependent flow law the horizontally averaged interior temperature displays very little variation with the amount of heat evacuated once all of the rheological parameters are fixed this finding may have important ramifications for parameterized convection we employ both the single mode mean field approximation and the complete two dimensional equations using finite elements to obtain solutions for the various types of rheologies from evaluating the geophysically relevant observables such as topography free air gravity anomalies surface heat flow and stress fields in the lithosphere we find that the lateral variations of these quantities predicted by a non newtonian rheology are much smaller than those derived from a linear rheology these results suggest that surface variations of geophysical observables are more compatible with a non newtonian rheology in the upper mantle

magnetic fabric in some granitic aureoles southern uplands scotland the loch doon cairnsmore of fleet and criffell granites and aureoles show considerable variation in their magnetic mineralogy and fabrics the loch doon area has magnetite as the dominant magnetic mineral while the cairnsmore of fleet area shows magnetite and hematite in different areas the criffell granite and immediately adjacent aureole are characterized by magnetite but hematite predominates in the outer aureole and country rocks despite such differences the magnetic fabric only shows effects of granitic emplacement within the thermal aureole mostly within 200 300 m of the contact considerable variation in magnetic fabric is observed over small distances but the granitic contacts are generally marked by a strong foliation parallel to the granite contact

volcanism on mars more than 15 years of planetary exploration of mars have given insight into the geologic processes that have shaped its surface the newly acquired viking data have shown that volcanism is one of the most important geologic processes operating on mars throughout its history in situ chemical analyses of martian soil by the viking lander spacecraft indicate mafic to ultramafic source rocks this is consistent both with available remote sensing data which indicate the presence of mafic minerals such as pyroxene and olivine and with petrologic modeling based on available geophysical data which suggest that martian lavas are probably iron rich and ultramafic these data strongly suggest that basaltic volcanism is widespread on mars and much of the photogeological data may be studied in this context photogeological analysis of the martian surface has shown two main types of volcanic morphologies the first type is central volcanoes which are volcanic landforms developed by continued and prolonged eruption from a point source vent this category includes 1 shields the classic low profile volcanic mountains of which olympus mons is the most spectacular example 2 domes steep sided constructs such as tharsis tholus that may represent lower rates of eruption than the shields or possibly more silicic lava compositions 3 highland patera radially textured low profile volcanoes that occur in the cratered terrain and are interpreted as ash shields 4 alba patera an apparently unique volcanic landform consisting of a vast volcanic center over 1500 km across with flank slopes of less than a tenth of a degree and 5 various small features such as cinder cones the second major category is volcanic plains which are units recognized by several criteria of which the presence of mare ridges and flow lobes are the most useful volcanic plains are subdivided into four main groups 1 simple flows broad smooth to rolling plains that contain numerous mare type ridges but no flow lobes interpreted as being composed of thick single cooling units 2 complex flows displaying multiple overlapping flow lobes interpreted to be indicative of thin multiple cooling units 3 undifierentiated flows plains that typically lack any morphologic identifying feature but are considered to be volcanic partly on the basis of their association with large volcanic centers and 4 questionable plains volcanic units heavily modified by other processes erosion tectonism etc so that their origins are uncertain when these categories of volcanic morphologies are combined with relative age data provided by crater statistics a volcanic history for mars can be derived as follows early heavy bombardment of mars was accompanied and followed by small scale fluvial channeling extensive flood volcanism the plateau plains and ash shield volcanism in the cratered terrain shortly after this time less extensive flood volcanism continued to resurface the planet during formation of the northern southern hemisphere dichotomy central volcanism became more prominent with the development of the alba patera center as well as the older shields and domes of the northern hemisphere early tharsis and elysium regions the development of the tharsis and elysium uplifts may have triggered the release of large scale catastrophic floods producing large channels continued uplift and lithospheric thinning concentrated volcanic activity in the tharsis region producing large shield volcanoes and extensive lava plains both central vent and plains volcanism have been active throughout martian history but the volumes of extrusion have gradually decreased with time this is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time gradually turning off the volcanism although many questions remain regarding martian volcanism the viking data have provided a remarkable detailed overview of the probable nature of the volcanic history of mars

reconstructing middle to late holocene palaeogeographies of the lower messenian plain southwestern peloponnese greece coastline migration vegetation history and sea level change abstract the glacio eustatic sea level rise after the last glacial maximum lgm led to a worldwide flooding of shelf areas and the evolution of marine embayments and indentations its significant deceleration in mid holocene times resulted in the overcompensation by sediment yields and shoreline progradation in many areas at the southeastern part of the lower messenian plain southwestern peloponnese greece detailed investigations of the holocene stratigraphy revealed a maximum landward shoreline displacement around 3000 bc subsequently aggradational processes started to form a prominent beach ridge in the late 3rd millennium bc this is the substratum on which the early iron age poseidon sanctuary of akovitika was founded approx 900 850 bc palaeogeographic reconstructions based on 18 corings in the sanctuary and its surroundings revealed the later extension of adjacent marshland and gradual surface levelling due to seasonal inundations these findings represent probable reasons for the abandonment of the ceremonial site around 380 350 bc palynological studies of the vegetational changes provide evidence for early land use and reflect regional settlement activities initial degradation and burning of woodland during late neolithic times c 3500 3100 bc as well as significantly reduced human impact during the protogeometric dark ages c 1060 900 bc are proven additionally local relative mean sea level rsl change since 5000 bc was reconstructed based on 14c dated paralic peats

secondary convection and the growth of the oceanic lithosphere abstract this paper presents a study of the evolution of the oceanic lithosphere from a thermomechanical approach we have investigated the finite amplitude development of secondary convection cells beneath the oceanic plates by means of the single mode mean field equations and the fully 2 dimensional convection equations using finite element techniques both newtonian and non newtonian rheologies with highly temperature and pressure dependences and an activation energy of 100 kcal mol 1 have been employed the temperature at the base of the convecting medium governs the final thickness of the lithosphere the mean interior temperature varies only slightly during the temporal evolution non newtonian rheology has the tendency to induce oscillatory time dependent behavior of the flow heat flow topography and gravity are influenced by secondary convection in two ways small scale perturbations with wavelengths of around 600 km arise from the lateral thermal differences between the uprising and descending convective limbs large scale features are also produced as a consequence of lithospheric growth the calculated quantities of the heat flow topography and gravity associated with small scale convection are typically in the range of o hfu o 102m and o 10 mgal the horizontal mean temperature profiles from the convection model are used to calculate long wavelength geophysical observables as a function of age convective processes are found to reduce the rate of lithospheric thickening predictions from our model can fit well the observed data of heat flow ocean floor topography and geoid offsets along fracture zones the last data base exhibiting the most sensitivity to thermal perturbations below the lithosphere our calculations show that the oceanic lithosphere is able to grow continuously up to o 109 y long past the flattening of the seafloor we report here that the thickness of a thermally equilibrated lithosphere could reach 250 km which lies within the appropriate range of values for the continental lithosphere as inferred from studies in seismology flexure observations and secular polar motions

constraints on plate tectonics initiation from scaling laws for single cell convection abstract the earth is the only planet known to have plate tectonics while other planets are covered with a stagnant lid on the earth the initiation of subduction which is thought to be the fundamental process for plate tectonics initiation is caused not only by the negative buoyancy of the lithosphere but also by the forces from plate motions however for planets which do not have plate tectonics the very first episode of lithospheric failure has to be caused by forces other than plate motions sublithospheric convection has been proposed as a possible mechanism that provides lithospheric instability through inducing stresses in the lithosphere and lithospheric failure can occur when the yield stress is below a critical value we test the applicability of scaling laws for the critical yield stress obtained in single cell convection simulations to strongly time dependent multi cell systems we show that with an appropriate choice of characteristic aspect ratio for the convective system the scaling laws from single cell simulations can be used to evaluate the conditions on the terrestrial planets in the inner solar system for plate tectonics to exist in agreement with previous studies the estimated values for critical yield stress and coefficient of friction are much lower than the expected values for the earth s lithosphere

ages of regional metamorphism and ductile deformation in the central and southern appalachians abstract a summary of available geochronology of deformational fabrics formed at greenschist and higher grades in the central and southern appalachians is presented as a map showing the ages of regional metamorphism and ductile deformation the ca 480 435 ma taconic event affected most of the piedmont and blue ridge provinces the ca 380 340 ma acadian event was milder and was centered in the west central piedmont and eastern blue ridge the 330 230 ma alleghanian event exhibits an abrupt ductile deformation front in the eastern piedmont and extends an unknown distance eastward below the atlantic coastal plain

on the existence of a second scale of convection in the upper mantle summary this paper is concerned with an examination of the possibility that there might exist a small scale of convective circulation beneath the oceanic lithosphere recent suggestions that this might be the case have been made in an effort to understand why the bathymetry of the sea floor deviates from the prediction of boundary layer theory for ages in excess of about 100 ma the energy source which sustains the secondary motion is supposed to be found in the steep temperature gradient near the planetary surface which is itself presumably maintained by the large scale convective circulation associated with plate creation and destruction here we investigate the extent to which the temperature dependence of viscosity may act so as to stabilize the upper boundary layer against disruption by such secondary instability if the viscosity profile is monotonie and the asymptotic upper mantle viscosity is about 1022poise as suggested by post glacial rebound data then the existence of the second scale is extremely unlikely on the other hand if a sufficiently pronounced low viscosity zone does exist under old sea floor then the development of such a second scale cannot be ruled out completely some recently obtained geophysical evidence is reviewed which suggests that this is unlikely to be the case

hot regions and the origin of marginal basins in the western pacific abstract volcanic provinces showing no genetic relationship to plate boundaries may be classified into two categories hot spots which are a few hundred kilometers across and may be nearly fixed in position with respect to deep mantle and hot regions which are a few thousand kilometers across and can migrate more freely the mantle upwellings which presumably give rise to them may originate at different depths by different causes it is observed that the marginal basins older than 15 ma of the western pacific become progressively younger northward with the exception of the south fiji basin this leads to the hypothesis that the spreading of marginal basins was caused by the mantle upwelling associated with a migrating hot region and that a hot region which started from the australia region in the late cretaceous migrated northward successively creating the tasman coral sea caroline south china parece vela shikoku and japan basins through paleocene eocene oligocene and early miocene time this hot region presently underlies northern china mongolia and adjacent areas another hot region is assumed to have caused the spreading of the south fiji basin and all the currently spreading basins in the southwestern pacific spreading of individual marginal basins occurred during the short period when a hot region was passing the pertinent area the main merit of this hypothesis is that it can explain the relationship between the location and age as well as the short duration of spreading of western pacific marginal basins marginal basins are formed commonly though not always in the overriding plates near subduction zones because in such a setting a spreading marginal basin is readily accommodated either by an oceanward movement of the nearby subduction zone or by a continentward movement and subduction of the overriding oceanic plate there are a few marginal basins that were formed in other tectonic settings and accommodated by some other mechanism of compensative subduction presumably the splitting of the supercontinent pangea was also caused mainly by the effect of the mantle upwelling associated with the same hot region that later migrated northward creating marginal basins in the western pacific the main basis for this presumption is the fact that the splitting of pangea was completed in the australia region in middle cretaceous time whereas the spreading of marginal basins in the western pacific began in the same australia region in the late cretaceous immediately following

subduction initiation by thermal chemical plumes numerical studies abstract prior suggestions for the initiation of subduction have included sediment loading compression and plate reconfiguration as potential triggers here we investigate the possibility of subduction initiation by the interaction of the lithosphere with a buoyant mantle plume numerical testing of this hypothesis has been conducted in 2d with the i2vis thermo mechanical code accounting for phase transitions and a viscoplastic model of a thin oceanic lithosphere hit by a partially molten thermal chemical or purely thermal plume we demonstrate that a mantle plume can break the lithosphere and initiate self sustaining subduction provided the plume causes a critical local weakening of the lithospheric material above it the intensity of the required weakening depends on the plume volume plume buoyancy and the thickness of the lithosphere and is the highest for the least buoyant purely thermal plumes another necessary condition is the presence of high pressure fluids at the slab upper interface reducing the effective friction coefficient there to very low values based on our results we suggest that sheet like instabilities of the archean mantle convection could have initiated subduction on earth where ocean was already present in less stable tectonic settings provided that mantle plumes sheets at that time were rich in water and melt which could drastically reduce the effective friction coefficient in the lithosphere above the plume our numerical models are also in good agreement with suggested concepts for corona formation on venus

perturbation analysis of convective instability of oceanic lithosphere and initiation of subduction zones a linear perturbation analysis is made on convective instability of the oceanic lithosphere to understand the occurrence of subduction on the earth the oceanic lithosphere is modeled by the upper part of top thermal boundary layer in a convecting newtonian temperature dependent viscosity fluid thickening of oceanic lithosphere with its age due to cooling at the surface is modeled by thickening of the thermal boundary layer with time its thickening rate l is a measure of the rate with which temperature in the thermal boundary layer decreases with time and hence is a measure of the rate with which viscosity in the thermal boundary layer increases with time the linear perturbation analysis shows the possible excitation of plural eigenmodes to give rise to an instability in the thermal boundary layer depending on a threshold value rc of the local rayleigh number r of the thermal boundary layer further rc is shown to be a linearly increasing function of l which is treated as a free parameter from estimates of r and l appropriate for the major oceanic lithosphere denoted as robs and l obs respectively i find that rc l 0 robs rc l l obs the flow pattern of mantle convection depends strongly on which eigenmodes are excited by the convective instability in thermal boundary layer 1 when r is lower thanrc only the fundamental and the first higher modes at most are excited the resulting mantle convection manifests itself as the secondary convection 2 when r is higher than rc the modes higher than the first higher mode are also excited the resulting mantle convection involves lithospheric instability leading to large local deformation in the oceanic lithosphere and finally to subduction of the oceanic lithosphere this result implies that 1 subduction does not begin newly in the major oceanic lithosphere at present since lithospheric instability is suppressed by thickening of the major oceanic lithosphere neither by its high viscosity nor by its buoyancy 2 subduction will newly begin in the major oceanic lithosphere due to lithospheric instability in future when the oceanic lithosphere becomes so old that its thickening rate l decreases to sufficiently small value the latter result suggests that lithospheric instability is an important agent that maintains multiplate tectonics on the earth

holocene fluvial development of the upper tigris valley southeastern turkey as documented by archaeological data abstract this study was carried out to elucidate the holocene development of the valley of the tigris river between bismil and batman which will be inundated by the reservoir waters of ilisu dam to be built in upper tigris valley and to collect the geoarchaeological data of the mounds located there in the tigris valley 4 5 and 2 3 m terraces were formed in the holocene according to geoarchaeological data obtained from the mound located on the 4 5 m terrace it was determined that the tigris river has been flowing in the same bed from the neolithic age the floodplains of the 4 5 m terrace occurred as a result of floods which took place in three different cycles the first caused the formation of late pleistocene early holocene channel and floodplain material composed of coarse gravel and sandy silt on this floodplain with a relative altitude of 2 m above river level late neolithic settlements 6000 5500 bc were formed the second cycle is represented by the formation of early chalcolithic 5500 4000 bc floodplain material there were late chalcolithic and early bronze age 4000 2650 bc settlements formed on this floodplain with a relative altitude of 3 3 5 m above river level the third and the final cycle is represented by 1 2 m thick yellowish orange flood deposits which started to form from the end of early bronze age i these cover the early bronze age i cemetery 2800 2650 bc and settlements belonging to earlier periods as in the case of asagi salat mound

the upper thermal stability of chlorite quartz an experimental study in the system mgo al2o3 sio2 h2o experiments up to water pressures of 21 kbar have been undertaken to bracket the reactions chlorite quartz talc kyanite h2o chlorite quartz talc cordierite h2o and talc kyanite quartz cordierite h2o by reversed runs in the system mgo al2o3 sio2 h2o mash these reaction curves intersect at an invariant point ip1 at ph2o 6 4 0 2 kbar and a temperature of 624 4 c the curve of the chlorite quartz breakdown to talc kyanite h2o at water pressures above 6 4 kbar shows a negative dp dt with the slope decreasing with rising pressure whereas the slope of the breakdown curve to talc cordierite h2o at water pressures is clearly positive the composition of the chlorite solid solution reacting with quartz has been estimated to be approximately mg4 85al1 15 al1 15si2 85o10 oh 8 over the entire pressure range investigated the composition of the talc solid solution forming by the breakdown of chlorite quartz appears to be mg2 94al0 06 al0 06si3 94o10 oh 2 at ph2o 2kbar with increasing pressure the al content of talc decreases reaching a value of about 0 06 atoms per formula unit at p h2o 21 kbar as a consequence of the new experimental data the existing phase topologies of the mash system and k2o mash system have been revised for example the invariant point ip1 and the univariant reaction curve kyanite talc h2o chlorite cordierite are stable for this reason the development of medium to high temperature metamorphic rocks compositionally approximating the mash system must be reconsidered the whiteschists from sar e sang afghanistan are treated as an example the application of the present experimental data to metamorphic rocks of more normal composition requires the examination of the influence of further components this leads to the conclusion that the introduction of fe2 into magnesian chlorite extends its stability field in the presence of quartz by 10 15 c in comparison with pure mg chlorite

did the red sea mediterranean connection over the dead sea fault zone end in the late pliocene abstract the delta plain of the asi orontes river in hatay turkey is located between two regional major tectonic zones the dead sea fault zone from the red sea to antakya and the east anatolian fault zone from karliova to antakya sediment samples from five cores performed on the asi delta plain to 15 m depth were studied and three fossil groups were identified in 5 samples they mainly consist of 51 foraminiferal species from 42 genera ostracod genera representing marine brackish and fresh water environments and gastropoda and bivalvia taxa the abundance of some benthic foraminifera in the recent sediment samples including euuvigerina reineri bedford siphonina tubulosa cushman and siphonodosaria abyssorum brady which are common in the pacific ocean indian ocean arabian sea and red sea is remarkable in addition euuvigerina reineri bedford individuals about 70 ka have been collected from magaracik village to the north of the drilling area the existence of these species in the quaternary sediments indicates that the water connection via the gulf of aqaba on the dead sea fault zone was still open in the pleistocene

palaeomagnetism of the loch doon granite complex southern uplands of scotland the late caledonian palaeomagnetic record and an early devonian episode of true polar wander abstract the southern uplands terrane is an ordovician silurian back arc foreland basin emplaced at the northern margin of the iapetus ocean and intruded by granite complexes including loch doon 408 3 1 5 ma during early devonian times protracted cooling of this 130 km 3 intrusion recorded magnetic remanence comprising a predominant a magnetisation linked to initial cooling with dual polarity and mean direction d i 237 64 95 4 palaeopole at 316 e 21 n subsidiary magnetisations include mesozoic remanence correlating with extensional tectonism in the adjoining irish sea basin b d i 234 59 and minority populations c d i 106 2 and d d i 199 1 recording emplacement of younger 395 ma granites in adjoining terranes and the variscan orogenic event the a directions have an arcuate distribution identifying anticlockwise rotation during cooling a comparable rotation is identified in the orthotectonic caledonides to the north and the paratectonic caledonides to the south following closure of iapetus continental motion from midsoutherly latitudes 40 s at 408 ma to equatorial palaeolatitudes by 395 ma is identified and implies minimum rates of continental movement between 430 and 390 ma of 30 70 cm year more than double maximum rates induced by plate forces and interpreted as a signature of true polar wander silurian devonian palaeomagnetic data from the british scandinavian caledonides define a 430 385 ma closed loop comparable to the distributed contemporaneous palaeomagnetic poles from gondwana they reconcile pre 430 ma and post 380 ma apw from this supercontinent and show that laurentia baltica avalonia lay to the west of south america with a relict rheic ocean opening to the north which closed to produce variscan orogeny by a combination of pivotal closure and right lateral transpression

the nature and magnetic expression of isograds in the contact aureole of the liberty hill pluton south carolina summary introduction the granitic rocks of the southeastern piedmont have been divided into several groups on the basis of age composition and field appearance butler and ragland 1969a fullagar 1971 wagener and howell 1973 wright and others 1975 the liberty hill is one of the postmetamorphic coarse grained granitoids of the southern appalachian piedmont a group whose field relations petrology chemistry and ages have been reviewed by fullagar and butler 1979 and speer and others 1980 previous geologic mapping indicated that the liberty hill pluton has a cordierite bearing thermal metamorphic aureole bell and others 1974 which is similar to the contact aureoles of several of the other plutons in the same group this paper is a result of a study of the magmatic and postconsolidation evolution of these granites examination of the contact metamorphism offers a better opportunity for estimating intensive parameters of pressure temperature oxygen fugacity and their variation following emplacement than does study of the granite alone the results also provide constraints on the regional conditions during intrusion in addition the aureole of the liberty hill provides a clear picture of mineral chemistries and metamorphic reactions that occur in the contact metamorphism of low grade slates dominated by a succession of continuous reactions

alluvial geoarchaeology of a small drainage basin in western anatolia late holocene landscape development and the question of the mouth of the paleo bakircay abstract late holocene landscape evolution in the geyikli basin a sub catchment of the bakircay basin on the west anatolian coast and its implications for the plaeogeography of the environs of ancient pergamon modern bergama were studied by a combination of archaeological and geographical investigations the study aims to investigate whether the dorpfeld scenario of the paleogeographical situation in the lower bakircay valley is true or not the scenario postulates that during the late holocene an alluvial fan fed from the geyikli valley progressively closed a topographical constriction between the aegean sea and a supposed paleo gulf that occupied the lower bakircay valley initially this caused the development of an inland lake and finally the shift of the mouth of the paleo bakircay from a northern position to its modern southern position the lithostratigraphy of four sediment outcrops in the lower geyikli basin and in the topographical constriction between the aegean coastal plain and the bakircay valley shows that during the past ca 1950 years the lower geyikli valley was inhabited by a braided river with a highly dynamic depositional system sedimentation totalled about 4 6 m in the past 1950 years indicating a drowning of the landscape in terrestrial sediments in recent times gravel mining has led to a deformation of the valley floor and the geyikli s fluvial terrace has become inactive the lack of any sediment related to a paleo gulf or a paleo lake inside the bakircay basin as well as the lack of any sediments of a northern paleo bakircay documents that the dorpfeld scenario does not apply for the past 1950 years archaeological findings show that the geyikli basin was intensively settled in historic times but there is no evidence that the geyikli basin was anthropogenically deformed in a way that could have contributed to the dorpfeld scenario

holocene valley aggradation driven by river mouth progradation examples from australia since the end of the post glacial sea level rise 6800 years ago progradation of river mouths into estuaries has been a global phenomenon the responses of upstream alluvial river reaches to this progradation have received little attention here the links between river mouth progradation and holocene valley aggradation are examined for the macdonald and tuross rivers in south eastern australia optical and radiocarbon dating of floodplain sediments indicates that since the mid holocene sea level highstand 6800 years ago vertical floodplain aggradation along the two valleys has generally been consistent with the rate at which each river prograded into its estuary this link between river mouth progradation and alluvial aggradation drove floodplain aggradation for many tens of kilometres upstream of the estuarine limits both rivers have abandoned their main holocene floodplains over the last 2000 years and their channels have contracted a regional shift to smaller floods is inferred to be responsible for this change though a greater relative sea level fall experienced by the macdonald river since the mid holocene sea level highstand appears to have been an additional influence upon floodplain evolution in this valley copyright 2006 john wiley sons ltd

small scale variations and subtle zoning in granitoid plutons the liberty hill pluton south carolina u s a abstract imperfect flow separation and remixing of crystals and melt produced chemical mineral and textural variability on the scale of several centimeters to meters in coarse grained granitoids of the liberty hill pluton this is believed to develop during emplacement because the resulting layering conforms to the geometry of the pluton and is better developed toward the margins mineral specific equilibrium and fractional crystallization regimes superimposed on the flow separation and remixing produced more complex compositional variations than expected from such granitoid cumulate processes alone the process is chemically comparable to restite unmixing but it is difficult to demonstrate that many minerals involved in the flow are restites local compositional inhomogeneities also formed by deformation and disaggregation of enclaves depending on whether the enclaves are interpreted as xenoliths chilled mafic magma or high melting point restite clots they represent contamination by mechanical assimilation magma mingling and mixing or restite unmixing marginal granitoids distinguished from the central granitoids by pink feldspar biotite muscovite rather than white feldspar amphibole biotite are more evolved but overlap the compositional range of the central granitoids mineralogic and textural similarity and a gradational contact between the two granitoids indicate they are related and that the pluton s subtle reverse zoning was produced by a continuous in situ process flow separation and remixing operating more efficiently and on a larger scale may have produced the more evolved composition of the marginal granitoids however proximity to the contact is more important than rock composition in determining mineralogy there is slight geochemical evidence for contamination of the marginal granitoids by the wall rocks compared to central granitoids they have small lree depletions and hree enrichments which more nearly reflects the lree depletion and hree enrichment of the wall rocks cross cutting contacts and slightly differing compositional trends indicate a later and distinct evolution for the finer grained biotite granitoids they have silica enrichment incompatible element enrichment rb u th compatible element depletion major elements sr ba depleted hree and less frequently lree contents as compared to the central granitoids the fine grained granitoids could be a contemporaneous and unrelated magma or fractionally crystallized from the coarse grained magma compositional mineralogic and textural differences among the later finer grained granitoids indicate either multiple magmas periodic sampling and intrusion of successive residual melt fractions or flow separation and remixing during emplacement

tomography the geoid and plate motions the dynamics of the earth s mantle and its relationship to mantle structure as revealed by seismic tomography the geoid and plate motions are discussed in a critical review of u s research from the period 1987 1990 sections are devoted to plates and mantle convection seismic anomalies flow and the geoid subducted slabs and the 670 km discontinuity the physical properties of the mantle plumes and computational and experimental modeling efforts also included is a comprehensive bibliography for the period 248 refs

low pressure metamorphism and anatexis of carolina slate belt phyllites in the contact aureole of the lilesville pluton north carolina usa in the contact aureole of the lilesville granite and comagmatic pee dee gabbro n c greenschist facies phyllites of the carolina slate belt have been overprinted by a series of metamorphic reactions producing opx bearing hornfelses and migmatitic gneisses in the exterior aureole the slate belt assemblage chl ms ep ab qz gives way to the continuous reaction assemblages chl bt cd ms ab ep qz bt cd ms an8 29 qz bt cd kf ms pl qz bt cd als ms kf pl qz and bt cd ga kf pl qz from lowest to highest grade the interior aureole interpreted as part of the floor of the granite bears the continuous and discontinuous reaction assemblages bt cd als kf pl qz bt cd kf pl qz and near the gabbro bt cd ga opx kf pl qz the leucosomes of the migmatitic interior aureole are predominantly trondhjemites with the assemblage an35 45 qz bt cd kf restites in the migmatitic interior aureole contain the afm assemblages bt bt cd bt cd als and bt cd ga plus kf an40 50 and qz contact metamorphism was isobaric at 4 0 5 1 or 2 0 3 5 kb depending on choice of aluminosilicate triple point temperatures reached 650 c in the migmatitic interior aureole and approached 750 c near the gabbro text p text h text 2 text o was less than 0 8 in the migmatites and was lower in the interior aureole and in the high grade exterior aureole partial melting in the migmatitic interior aureole took place during dynamothermal metamorphism caused by the magmatic diapir incipient melting occurred by the reaction bt cd kf pl qz w liquid the melt was h2o undersaturated and coefficients of the reactants were weighted heavily toward the felsic minerals the proportion of felsic minerals in the leucosomes was controlled in part by modal abundance of kf pl and qz available for melting the incorporation of k into biotite by subsolidus reactions coupled with the high thermal stability and low solubility of biotite in a felsic melt are responsible for the trondhjemitic composition of the early anatectic liquids

holocene stratigraphy and geomorphological evolution of the aegean coastal plains of anatolia abstract three main stages can be distinguished in the sedimentary development and geomorphological formation of the present delta plains on the aegean coast of turkey the early holocene is characterized by post glacial transgression and dependent sedimentation the middle holocene was the period when sea level reached the present level and apart from small fluctuations stopped rising alluviation and deltaic progradation were prevalent during this transition period from marine to terrestrial environments as for the late holocene deltaic progradation slowed down and delta plains were covered by floodplain sediments these characteristics can be observed in the same sequence throughout the aegean coast of turkey

stagnant lid convection on venus the effect of strongly temperature dependent viscosity on convection in the interior of venus is studied systematically with the help of finite element numerical models for viscosity contrasts satisfying experimental constraints on the rheology of rocks venus is likely to be in the regime of stagnant lid convection this regime is characterized by the formation of a slowly creeping very viscous lid on top of the mantle venusian lithosphere and is in agreement with the tectonic style observed on venus stagnant lid convection explains large geoid to topography ratios on venus by the thermal thinning of a thick lithosphere the thickness of the lithosphere can be as large as 400 550 km for beta regio and 200 400 km on average geoid and topography data and experimental data on the rheology of rocks provide constraints on the viscosity of the mantle 10 20 10 21 pa s the convective stresses in the interior 0 2 0 5 mpa the stresses in the lid 100 200 mpa the velocity in the interior 0 5 3 cm yr 1 and the heat flux beneath the lithosphere 8 16 mw m 2 parameterized convection calculations of thermal history of venus are difficult to reconcile with a thick present day lithosphere however a sufficiently thick lithosphere can be formed if a convective regime with mobile plates was replaced by stagnant lid convection around 0 5 b y ago one of the possible explanations for the cessation of venusian plate tectonics is that during the evolution of venus stresses in the lid dropped below the yield strength of the lithosphere this model predicts a drastic drop in the heat flux thickening of the lithosphere and suppression of melting and is consistent with the hypothesis of cessation of resurfacing on venus around 0 5 b y ago

stability of the oceanic lithosphere with variable viscosity an initial value approach abstract we have studied the problem concerning the onset of convective instabilities below the oceanic lithosphere a system of linear partial differential equations in which the background temperature field is time dependent is integrated in time to monitor the evolution of incipient disturbances two types of rheologies have been examined one depends strongly on temperature the other involves a viscosity which is both temperature and pressure dependent the results from this initial value approach in which the viscosity profiles migrate downward with time reveal the importance of considering temperature and pressure dependent rheology in issues regarding the development of local instabilities in upper mantle convection for temperature dependent viscosity viscosities of 0 1020p are required to produce instabilities with growth rates of 0 1 ma in contrast these same growth rates can be attained for a temperature and pressure dependent viscosity profile with a mean value close to 0 1020p in the upper mantle owing to the presence of a low viscosity zone 0 1020p existing right below the lithosphere unlike the results of temperature dependent viscosity whose growth rates increase with time the amplification of disturbances in a fluid medium with temperature and pressure dependent rheology reaches a maximum at an early age

a controlled source seismic and gravity study of the high lava plains hlp of eastern oregon 1 this study employs data collected during the high lava plains hlp controlled source seismic experiment conducted in september 2008 in this experiment 2612 short period seismic recorders and 120 3 component recorders were deployed across eastern oregon and adjacent parts of nevada and idaho to record 15 seismic sources seismic and gravity data were integrated to create 2 d crustal scale p wave velocity and density models for the 400 km long nw se and n s profiles to provide a better understanding of the crustal and upper mantle structure and ultimately the magmatic and tectonic evolution of the region these models are the first high resolution images beneath the path of migratory bi modal volcanism that dotted the high lava plains beginning at 16 ma our models show that the crustal structure across the hlp region is similar to that of the northern basin and range which has experienced extension since 35 ma but with moderate magmatic modification of the crust a thick layer 5 7 km of sediments and volcanics extends over most of the area and is thickest in the harney basin area we interpret denser faster material in the lower to middle crust under the southern harney basin area to be mafic intraplating we have also identified a region of denser faster material in the upper crust in the vicinity of oregon idaho border the crust thickens from 34 to 37 km and the lower crust increases in density 2 8 2 85 g cm3 from west to east across eastern oregon in close proximity to the interpreted position of the 0 706 sr isotope line suggesting a decrease in extension in the lowermost crust below the southeastern hlp there is relatively high velocity 7 2 7 4 km s and density 2 95 g cm3 that suggests the presence of underplating the hlp region has undergone moderate extension and the average crustal velocity is somewhat higher than in the adjacent basin and range suggesting some magmatic modification in the lower crust but not as much as might be expected given the voluminous surface volcanism

palaeogeographical and palaeoenvironmental reconstruction of the medjerda delta tunisia during the holocene abstract the progradation of the medjerda delta has been the subject of many studies since the 19th century the scale and the rapidity of this phenomenon interested researchers in various fields early on such as geomorphology geology palaeogeography history archaeology or geoarchaeology indeed the delta prograded by around 10 km over 3 millennia at the time of its foundation supposedly at the end of the 12th century bc the phoenician city of utica was located on a promontory bathed by the sea but the sediments carried by the medjerda progressively sealed the bay leaving the tip of the utica promontory now 10 km inland this area is therefore an exception to the general pattern along the tunisian coast since as over the same period everywhere else there is a regression of the coastline owing to a sea level rise of several decimeters based on multi proxy analyses of two coring transects this paper aims to reconstruct the palaeoenvironments and the palaeogeography of the medjerda delta s progradation since the mid holocene some aspects of which are described in ancient sources the results highlight in particular an episode of high intensity flooding around the 4th century ad which is consistent with episodes of high floods and an increase in sedimentation rates recorded in the watershed at the end of the roman period the gradual abandonment of the city of utica can certainly be related to the activity of the medjerda river but our results show that it is because of an increase of fluvial sediment contribution in connection with an erosive crisis in the headwaters and not because of the change of course of the river which had occurred long before

continental margin tectonics forearc processes recent studies of convergent plate margins and the structural development of forearc terranes are summarized in a critical review of u s research from the period 1987 1990 topics addressed include the geometry of accretionary prisms coulomb wedge taper and vertical motion in response to tectonic processes offscraping vs underplating or subduction the response to oblique convergence fluids in forearc settings the thermal framework and the effects of fluid advection and serpentinite seamounts also included is a comprehensive bibliography for the period

stability of the oceanic tectosphere a model for early proterozoic intercratonic orogeny resistance of modern oceanic tectosphere to the initiation of subduction can be evaluated by considering its flexural rigidity shear resistance in the subduction zone and the negative buoyancy force after mckenzie 13 these depend on the effective elastic thickness the depth to which shear stresses are appreciable and the tectospheric thickness respectively evaluation of these thicknesses and their variation with age allows development of a model in which oceanic tectosphere becomes progressively less stable with increasing age and spontaneously subducts at an age of 200 ma the same model applied to early proterozoic oceanic tectosphere distinguished only by having sub tectosphere temperatures 100 c higher than in the modern rquires that proterozoic ocean tectosphere subduct spontaneously at ages of about 75 ma the subduction of universally young oceanic tectosphere inhibits the production of juvenile magmas due to the release of volatiles from the descending slab at low pressures near the trench the model therefore accounts for the scarcity of subduction related magmas in many early proterozoic orogens it also predicts that ocean basins opening in the early proterozoic should have generally limited width that blueschist metamorphism should be rare and that early proterozoic oceanic crust should rarely be preserved at the earth s surface with progressive cooling of the mantle the proterozoic tectonic scheme may have changed gradually into the modern one by early phanerozoic time although parts of the pan african system may exhibit the characteristics of still unstable oceanic tectosphere

metamorphic control of the magnetic mineralogy of black shales in the swiss alps toward the use of magnetic isogrades abstract the magnetic susceptibility of the helvetic jurassic black shales sampled around the aar and gothard massifs in the swiss alps is due to iron bearing silicates magnetite or pyrrhotite it exhibits a clear correlation with the alpine metamorphism from zeolite to amphibolite facies it firstly decreases due to the breakdown of original magnetite then sharply increases when pyrite is transformed into magnetic pyrrhotite using numerous field measurements of the susceptibility it was possible to carry out a fast and precise mapping of the pyrrhotite in isograde which appears to correspond closely to the stilpnomelane out isograde the matrix susceptibility obtained by means of high field measurements with a cryogenic magnetometer is due to iron bearing silicates and shows only smooth variations with metamorphism both monoclinic and hexagonal pyrrhotites are observed in the high grade area

initiation of subduction by small scale convection 1 the possibility of initiation of subduction by sublithospheric small scale convection is investigated with the help of fowler s theory numerical constraints on the lithospheric stresses generated by convection and direct numerical simulations of subduction the derived scaling laws show that the critical yield stress for initiation of subduction by small scale convection is of the order of 30 mpa this value is comparable with the critical yield stress required for initiation of subduction by plate forces and with the estimates of stresses in the subduction zone this implies that small scale convection can play an important role in the initiation of subduction on the present day earth this also implies that small scale convection can initiate subduction in the absence of already occurring plate tectonics and thus can be a trigger mechanism for plate tectonics on the early earth and other terrestrial planets the critical yield stress for initiation of subduction by either mechanism is at least one order of magnitude smaller than the estimates of the lithospheric strength suggested by laboratory experiments on rock deformation such a low lithospheric strength is most likely caused by a relatively high abundance of water in the interior of the earth since the critical yield stress depends only weakly on planetary parameters water seems to be the key condition required for plate tectonics to occur on a terrestrial planet

geoarchaeology and aggradation around kinet hoyuk an archaeological mound in the eastern mediterranean turkey we examined the alluvial history of the plain near kinet hoyuk an archaeological mound or tell with a sequence of six millennia of occupation on the southeast mediterranean coast of turkey through 17 excavations over a 1000 m transect near the mound excavations ranged from 2 to 6 m deep and up to 20 m across this low gradient alluvial plain shows significantly different rates and processes of near mound sedimentation with one unit having nearly 4 m of late bronze age habitation and flood deposits and another having 4 m of hellenistic channel and floodplain deposition this flat alluvial surface turns out to be a rich geoarchaeological landscape that shrouds early and late bronze age settlements hellenistic walls and two epochs of roman roads one widespread phenomenon was a hellenistic or earlier paleosol and occupation level covered by channel gravels and overbank deposits mostly from the hellenistic to the late roman period these channel and floodplain deposits filled in and flattened out the off mound settlements blanketing the pre hellenistic topography and silting in a long active port this glut of alluvium correlates in time with drier conditions and the most intensive land uses in the watershed where roman and hellenistic sites today are severely eroded

a geoarchaeological case study in the chora of pergamon western turkey to reconstruct the late holocene landscape development and settlement history this paper investigates the late holocene landscape development and settlement history of the central bakircay valley the ancient kaikos valley in western turkey which exemplifies a buried archaeological site approximately 12 km sw of pergamon a minimally intrusive geoarchaeological approach was applied by coupling an archaeological survey geophysical exploration geomorphological mapping and sedimentological analysis of drilling cores and pre existing outcrops the geomorphological and lithostratigraphical results imply that in the early and middle holocene the site was situated on a depositional piedmont plain that was protected from the annual bakircay floods over the past two millennia the bakircay flood plain was gradually aggraded and the site became prone to flooding despite the limitations of non intrusive archaeological investigations three scenarios were developed on the function and age of the buried site hence the site was either a sanctuary from the 2nd century ad a luxurious estate from the 4th 8th century ad or a lime kiln from late antique byzantine times

orogeny and metamorphism a model for deformation and pressure temperature time paths with applications to the central and southern appalachians a model is presented for deformation uplift and exhumation in convergent orogens based on the following premises 1 foreland basin subsidence monitors the distribution in time and space of overthrust loads added to an orogen 2 the presence of an inherited rifted margin plays an important role in the subsequent history of an orogen by forming a basement ramp or buttress that must be surmounted in order for thrusts to advance on the craton on the seaward side of this transition up to 20 km of overthrusts can be accumulated without creating topography 3 critical shape theory can be applied to orogens as a whole allowing predictions to be made concerning dynamic balance between mass addition and loss uplift exhumation and growth of topography and 4 pressure temperature time p t t data can be used to reconstruct particle paths within the deforming orogen three states of overthrust orogens can be defined based on the relative rates of mass loss and mass addition as monitored by the foreland rapid exhumation of metamorphic terranes is most likely in the steady state where erosion balances accretion a constructive state where mass addition is greater than mass loss results in crustal thickening and initially little exhumation a destructive state where mass loss outweighs mass addition results in slow exhumation or subsidence of metamorphic rocks in the orogen depending on whether mass is removed by erosion or by extension p t t data on peak metamorphism pluton emplacement uplift exhumation and cooling can be used in conjunction with data from the foreland to distinguish among these various states the topography and strength of the inherited rifted margin play an important role in localizing zones of exhumation and uplift within the orogen application of this model to the central and southern appalachians suggests that during the constructive phases of the taconian and acadian orogenies overthrust loads accumulated mainly on the seaward side of the ocean continent transition as marked by the bouguer gravity gradient between the acadian and alleghanian orogenies the appalachian orogen was probably in a steady state with uplift and exhumation of rocks in the orogen but little subsidence of the foreland or advance of thrusts toward the craton the constructive stage of the alleghanian orogeny achieved the critical topography necessary to drive crystalline thrust sheets over the craton this resulted in widespread uplift and westward transport of older metamorphic rocks post orogenic unroofing of the southern appalachians is compatible with the predictions of flexural models the post orogenic unroofing history of the central appalachians and ouachitas probably reflects mesozoic extension in these areas

in search of the harbours new evidence of late roman and byzantine harbours of ephesus abstract ephesus greek name ephesos in western turkey was an important harbour city during antiquity the progradation of the kucuk menderes delta has continuously shifted the coastline westwards thus along with the delta progradation new harbour sites had to be established in a western direction historical sources refer to different harbours while much is known about the roman and older ones the exact location of the ports and the coastline in late roman and byzantine times is still an open question this article presents the results of geoarchaeological research in the area located along the southern flank of the kucuk menderes graben near ephesus sediments from cores were examined with geochemical sedimentological and microfaunal analyses these data were combined with the study of ancient maps and satellite images the chronological framework was rendered by ams 14 c ages and diagnostic ceramics the farthermost inland shoreline dates from 5000 bc since then delta progradation has continuously shifted the shoreline westwards canakgol today a little lake to the west of the city of ephesus is identified as the harbour site in late roman and byzantine times this harbour persisted at least until the 16th century ad further a landing site with a pier was discovered west of canakgol presumably dating to the late byzantine ottoman times

passive margin evolution initiation of subduction and the wilson cycle we have constructed finite element models at various stages of passive margin evolution in which we have incorporated the system of forces acting on the margin depth dependent rheological properties and lateral variations across the margin we have studied the interrelations between age dependent forces geometry and rheology to decipher their net effect on the state of stress at passive margins lithospheric flexure induced by sediment loading dominates the state of stress at passive margins this study has shown that if after a short evolution of the margin time span a few tens of million years subduction has not yet started continued aging of the passive margin alone does not result in conditions more favourable for transformation into an active margin although much geological evidence is available in support of the key role small ocean basins play in orogeny and ophiolite emplacement evolutionary frameworks of the wilson cycle usually are cast in terms of opening and closing of wide ocean basins we propose a more limited role for large oceans in the wilson cycle concept

magnetic signatures of zones of fractures in igneous metamorphic rocks with and example from southeastern new england reply abstract elongate negative magnetic anomalies in the northern hemisphere can be related to zones of fractured bedrock a magnetic model with induced magnetization of a horizontal plate that is separated by a nonmagnetic gap can reproduce observed magnetic lows model anomalies show the dependence of the intensity of the magnetic lows on parameters such as magnetic susceptibility width of the nonmagnetic gap and dip angle of the fracture zone the magnetic low is superposed by a larger regional low which increases with the thickness of the magnetized plate the strike direction of the fracture zone and the inclination of the ambient magnetic field also control the anomaly so that new sets of model curves are necessary for each new field case depending on location and orientation of the fractures the model has been tested over a negative magnetic anomaly in southern new england with ground and aeromagnetics the coincidence with a zone of fractures known as the watch hill lineament has been documented with detailed geological mapping remote sensing and fracture trace analysis a good agreement between the model anomaly and the observed anomalies on the ground and from the air is possible with observed magnetic susceptibilities between 0 4 10 3 and 1 2 10 3 cgs the anomaly width ranges between 1 4 km and a few tens of meters a detailed analysis of intersecting fractures allows a distinction of older from younger anomaly trends this zone of fractures associated with the magnetic anomaly is believed to be part of a major fault zone its northeastern extension is the margin of the narragansett basin which is filled with sediments of carboniferous age while there have been many suggestions for its origin the results of this study favor the formation of a pull apart basin after the area was subjected to extensional stress