first evidence of high pressure metamorphism in the cover series of the southern menderes massif tectonic and metamorphic implications for the evolution of sw turkey abstract the menderes massif occupies a large part of western turkey it is tectonically overlain by nappes of the izmir ankara suture zone including the bornova flysch zone on its northern flank the afyon zone on its eastern border and the lycian nappes on its southern flank the discovery of magnesiocarpholite kyanite assemblages in the mesozoic cover sequence of the southern menderes massif leads to the very first consideration that a major high pressure hp metamorphic event affected the massif during its alpine evolution estimations of minimum pressure temperature conditions about 10 12 kbar and 440 c suggest a minimum burial of 30 km for the metasedimentary rocks of the menderes massif similar to that for the eocene dilek blueschists which belong to the cycladic complex this finding of high pressure rocks within the menderes cover series as well as the recent description of low grade high pressure parageneses in the basal thrust sheets of the overlying lycian nappe complex has strong implications for the tectono metamorphic evolution of these units the characteristics of this high pressure metamorphism and the deformation features observed in the southern menderes massif allow consideration of a fast burial during alpine subduction and nappe stacking three high pressure units were piled up during the eocene collision of the sakarya continent and the tauride menderes block the lowermost unit consists of the imbricated core and cover of the menderes massif the intermediate unit is the cycladic blueschist complex dilek and samos regions and the uppermost unit is made of the lycian nappes the retrogression of high pressure parageneses from the menderes massif follows an isothermal decompression path and the associated deformation is characterized by a severe stretching oriented n s to ne sw during the high pressure event and its exhumation we propose a tectono metamorphic model in three main stages 1 the southward translation of the high pressure lycian nappes and the burial of the menderes and cycladic metasediments to a depth of at least 30 km to allow their eocene high pressure metamorphism 2 a northward continuum of deformation responsible for top to the north fabrics associated with the main menderes metamorphism peak paleocene eocene and its progressive cooling late eocene north verging folding thrusting imbrication of core and cover series and n s to ne sw intense stretching associated with the menderes high pressure metamorphism and its exhumation these top to the north to top to the northeast movements are probably related to the northward backthrusting of the lycian nappes reactivating the contact between the menderes massif and the lycian nappes as a top to the ne shear zone that allowed exhumation of the lycian high pressure rocks 3 oligo miocene n s extension during which the final exhumation of the metamorphic rocks along kilometre scale low angle detachments occurred

evolution of a tertiary volcanogenic trough in sw turkey the alakaya basins of the lycien belt field study of several stratigraphic sections from allochthonous thrust fault slices of sw turkey reveal that a deeply subsiding volcanogenic trough the alakaya basin existed during paleocene middle eocene times along the lycian belt the alakaya basin was located along a tectonically active zone of weakness between two relatively stable tectonic terrains the menderes massif to the northwest and the beydaglari continental platform to the southeast the basin was underlain by continental substratum all known outcrops of the alakaya sediments overlie platform carbonates of cretaceous age that correlate with the beydaglari shelf sediments the generation of the volcanogenic alakaya basin reflects a tensional period that culminated in middle eocene when basic volcanic activity took place the tensional stage was replaced by a compressional regime in late eocene and large scale overthrust faulting took place the alakaya basin was closed when the tefenni nappe from the north was emplaced on its sediments in late eocene the alakaya sediments overlying the tefenni nappe and underlying the cretaceous platform carbonates moved southeastward over a hundred kilometers onto the autochthonous sediments of the beydaglari terrain in miocene time the alakaya basin is analogous to the maden basin of se turkey thrust fault belt both basins were located along tectonically active belts the main stage of basin subsidence and volcanism was in middle eocene closure of both basins by large scale thrust faulting was in late eocene the creation and destruction of the volcanogenic alakaya basin may be related to the regional adjustments in plate motions in paleocene eocene times

deformation history of the high pressure lycian nappes and implications for tectonic evolution of sw turkey 1 in southwestern turkey the lycian nappe complex which overlies the autochthonous menderes massif and bey dag platform consists from base to top of metasediments a melange unit and an ophiolitic sequence fresh fe mg carpholite occurrence in the metasediments attests to a high pressure low temperature metamorphic event we report the distribution of fe mg carpholite and its breakdown products e g pyrophyllite and chloritoid on the bodrum peninsula south of the menderes crystalline massif the distribution of fe mg carpholite and its relics shows that the low grade high pressure metamorphism affected a widespread area in the lower units of the lycian nappes analysis of the ductile deformation in hp lt metasediments indicates shear senses top to the northeast to top to the east most of this deformation is contemporaneous with the retrogression of high pressure low temperature parageneses and is therefore coeval with exhumation from a depth of about 30 km at the top of the menderes massif cover series close to the contact with the lycian nappes similar eastward displacements are observed and trajectories of the stretching lineations are continuous from the lycian nappes to the menderes massif across the contact these observed movements are incompatible with the southward transport of the lycian nappes over the menderes massif we discuss the regional tectonic implications and conclude that the lycian nappes and the southernmost part of the menderes massif were exhumed in two stages 1 eocene top to the ne shear syn orogenic extension 2 miocene deformation contemporaneous with the aegean extension

palaeoenvironmental reconstruction and biostratinomic analysis of the jurassic yanliao lagerstatte in northeastern china abstract the middle upper jurassic yanliao lagerstatte contains numerous exceptionally preserved fossils of aquatic and land organisms including insects salamanders dinosaurs pterosaurs and mammaliaforms despite extensive study of the diversity and evolutionary implications of the biota the palaeoenvironmental setting and taphonomy of the fossils remain poorly understood we reconstruct both the palaeoenvironment of the daohugou area one of the most famous yanliao fossil areas and the biostratinomy of the fossils we use high resolution stratigraphic data from field investigation and excavations to document in detail the stratigraphic succession lithofacies facies associations and biostratinomic features of the lagerstatte our results show that frequent volcanic eruptions generated an extensive volcaniclastic apron and lake s in the studied area the frequent alternation of thin lacustrine deposits and thick volcaniclastic apron deposits indicates either that the studied area was located in the marginal regions of a single lake where the frequent influx of volcaniclastic apron material caused substantial fluctuations in lake area and thus the frequent lateral alternation of the two facies or that many short lived lakes developed on the volcaniclastic apron most terrestrial insects were preserved in the laminated normally graded siltstone claystone and tuff facies that form many thin intervals with deposits of graded sandstone siltstone and tuff in between within each interval the terrestrial insects occur in many laminae associated with abundant aquatic organisms but are particularly abundant in some laminae that directly underlie tuff of fallout origin most of these terrestrial insects are interpreted to have been killed in the area adjacent to the studied palaeolake s during volcanic eruptions their carcasses were transported by influxes of fresh volcaniclastic material primarily meteoric runoff and possibly minor distal pyroclastic flow into the palaeolake s and were buried in palaeolake deposits prior to extended decay probably due to a combination of rapid vertical settling ash fall and water turbulence

deep water facies processes and models a review and classification scheme for modern and ancient sediments abstract a review of previous work on modern and ancient deep water facies processes and models is presented with a new classification scheme involving 40 distinct facies related to 15 conceptually distinct facies groups these facies are fixed points in a spectrum of facies generated in a process continuum from resedimentation processes through semi permanent bottom currents to pelagic settling in essence the scheme is descriptive of the sedimentary attributes of sediments although it is designed to aid interpretation of possible sediment transport deposition processes the classification scheme is three tier with facies classes groups and constituent facies and is hierarchical to allow flexibility in its use there are seven facies classes with classes a e defined largely on the basis of grain size differences class f on the basis of internal organization and class g on composition the facies classes are class a gravels muddy gravels gravelly muds and pebbly sands with 5 gravel grade class b sands with 80 sand grade and 80 mud 40 silt and 0 20 sand class e muds and clays with 95 mud grade for the purpose of large scale mapping or reconnaissance fieldwork either the level of facies classes or groups may be appropriate whereas for more detailed sedimentology the more detailed facies level will be necessary

shallow water eruption fed mafic pyroclastic deposits along a paleoproterozoic coastline kangerluluk volcano sedimentary sequence southeast greenland abstract the 200 300 m thick volcano sedimentary sequence at kangerluluk is part of the psammite zone one of four major zones which constitute the 1 8 ga ketilidian orogen in south greenland three lithofacies are emphasized in the study 1 the conglomerate sandstone 2 the volcanic and 3 the pyroclastic lithofacies the 2 40 m thick conglomerate sandstone lithofacies represents a subaerial to subaqueous fan delta deposit matrix and clast supported conglomerates are interpreted as debris flow and longitudinal gravel bar deposits erosive based conglomerate channel fills attest to stream incision trough crossbedded sandstone interpreted as lunate megaripples planar bedded sandstone indicative of upper flow regime bar top sands and small scale trough crossbeds reflecting ripples follow up section form collectively with the conglomerate 0 40 2 50 m thick fining upward sequences the sandstone dominated unit up section from the conglomerates and composed of planar and low angle crossbeds minor ripples and graded beds as well as mudstone is indicative of a lower shoreface deposit below normal wave base the clastic sedimentary rocks are suggestive of a fan delta setting the 100 200 m thick volcanic lithofacies composed of pillowed and pillow brecciated lava flows is consistent with shallow water deposition interstratification of lava flows with both conglomerate sandstone and pyroclastic lithofacies intrusion of dykes into volcaniclastic rocks and peperite formation accentuate contemporaneity between volcanism and sedimentation and is a common feature of island arcs the 1 50 m thick pyroclastic lithofacies with sharp depositional contacts to the overlying volcanic and underlying conglomerate sandstone lithofacies was emplaced in a subaqueous setting the lithofacies is divided into a planar to crossbedded tuff lapilli tuff and a bedded lapilli tuff breccia whereby both deposits are inferred to result from shallow water surtseyan type eruptions the 5 15 m thick bedded lapilli tuff breccia with abundant bomb sag structures and graded beds is considered a result of subaqueous eruptions strong enough to form an insulating steam cupola characterized by ballistically emplaced bombs that rapidly collapsed allowing for transport via mass flow processes the deposits are considered proximal to the vent the 2 50 cm thick planar to crossbedded tuff lapilli tuff featuring abundant euhedral and broken crystals of feldspar 2cm and minor pyroxene 1 cm are massive graded crossbedded and stratified the planar but laterally discontinuous beds characterized by abundant low angle scours are interpreted as low to high concentration sediment gravity flows produced directly from subaqueous tephra jets that collapsed due to massive water ingestion local breccia size pyroclasts disrupting beds are interpreted as bomb sags the mafic eruption fed surtseyan type deposits postulated to be a subaqueous counterpart of cold subaerial base surges originate from subaqueous tuff cones formed along a rugged volcanic dominated shoreline featuring high energy fan deltas

time scales of intra oceanic arc magmatism from combined u th and u th he zircon geochronology of dominica lesser antilles the island of dominica located in the intra oceanic lesser antilles arc has produced a series of intermediate mostly andesitic lava domes and ignimbrites since the early pleistocene u th he eruption ages from centers across the island range from 3 to 770 ka with at least 10 eruptions occurring in the last 80 ka three eruptions occurred near the southern tip of dominica plat pays volcanic complex in the past 15 ka alone zircon u th ages from individual centers range from near eruption to secular equilibrium implicating protracted storage and recycling of zircons within the crust overlapping zircon crystallization peaks within deposits from geographically separated vents up to 40 km apart indicate that magma associated with separate volcanic edifices crystallized zircon contemporaneously two lava domes from the southern sector of the island display exclusively young zircon rim ages 50 ka with narrow crystallization peaks consistent with the construction of a new magma reservoir the younging of eruption and crystallization ages implies that the magmatic foci leading to the construction of this reservoir have migrated southward arc parallel over time overall our data support geochemical models for the ongoing construction of a silicic intrusive complex consisting of varying amounts of crystal mush beneath the island u pb zircon ages 1 2 ma indicate that accumulation of this complex is entirely quaternary in age together zircon u th and u pb ages for dominica suggest that the magmatic processes and time scales operating in intra oceanic arcs are similar to those documented for continental arcs

sedimentary record of explosive silicic volcanism in a cretaceous deep marine conglomerate succession northern antarctic peninsula lower cretaceous conglomeratic strata exposed on southern sobral peninsula were deposited on a deep marine apron in the back arc larsen basin close to its faulted boundary with the antarctic peninsula magmatic arc the succession is dominated by amalgamated beds of clast supported conglomerate which together with minor intercalated sandstones consist of varied but largely basaltic to andesitic volcanic material and clasts derived from the palaeozoic triassic meta sedimentary basement of the arc most of the volcanic clasts are thought to have been derived from lithified volcanic successions or older synvolcanic deposits rather than from sites of coeval eruption these mixed provenance strata enclose a number of intervals consisting mainly of inverse normally graded conglomerate and graded stratified pebbly sandstone in which the sand fraction is dominated by crystals and vitric grains considered to have been redeposited in the immediate aftermath of explosive silicic arc volcanism like syneruption deposits on non marine volcaniclastic aprons these intervals are more sand prone than the enclosing strata and appear to show evidence of unusually rapid aggradation plagioclase from one such interval has yielded 40ar 39ar ages concordant at 121 ma similar to those obtained from the non marine cerro negro formation deposited within the magmatic arc it is suggested that the two successions can be viewed as counterparts both recording a history of mainly basaltic to andesitic volcanism punctuated by relatively infrequent explosive silicic eruptions whereas the cerro negro formation consists mainly of syneruption deposits most of the volcaniclastic material delivered to the eruption distal deep marine apron appears to have been derived by normal degradation processes only rare silicic eruptions were capable of supplying pyroclastic material rapidly enough and in sufficient quantities to produce compositionally distinct syneruption intervals

stratigraphy and palaeoenvironment of the lower middle oligocene units in the northern part of the western taurides incesu area isparta turkey abstract this study describes the stratigraphic and palaeoenvironmental significance of the lower middle oligocene sediments based on the fauna from the delikarkasi formation and the microflora from the incesu formation of the incesu area northern part of the western taurides isparta province turkey in the area the oligocene sediments show a regressive succession which begins with the limestones of the delikarkasi formation indicating marine conditions followed by conglomerates sandstones and coaly mudstones of alluvial and fluvial shallow marine continental origin a well preserved foraminiferal assemblage including nummulites intermedius nummulites vascus and halkyardia maxima proves an early oligocene age for the delikarkasi formation due to palynological markers such as boehlensipollis hohli slowakipollis hippophaeoides dicolpopollis kockelii magnolipollis neogenicus ssp minor plicapollis pseudoexcelsus caryapollenites simplex and intratriporopollenites instructus the incesu formation which concordantly rests on the delikarkasi formation may be assigned to the early middle oligocene from the palynomorph assemblage three zones have been recognised according to abundance of species zone 1 is characterized by predominance of c simplex and momipites punctatus and rarely presence of tricolpate and tricolporate pollen zone 2 consists mainly of inaperturopollenites dubius leiotriletes maxoides ssp maximus verrucatosporites favus verrucatosporites alienus and infrequently marine dinoflagellate cysts zone 3 is characterized by a high percentage of ferns such as echinatisporis chattensis and polypodiaceoisporites saxonicus the presence of marine dinoflagellate cysts like apectodinium sp and cleistosphaeridium sp back mangrove elements such as acrostichum aureum and lepidocaryoid palms e g longapertites discordis longapertites punctatus and longapertites psilatus in the sediments of the incesu formation imply coastal or near coastal conditions terrestrial palynomorphs in more inland settings were transported by running water towards the sea conifers are represented by poorly preserved and rare pollen grains of pityosporites cathayapollis and piceapollis which may have been transported by wind in this study the terrestrial climate of the incesu formation is also discussed on the basis of the coexistence approach method the climate was warm at the coast over 20 c as evidenced by a aureum and lepidocaryoid palms whereas there was a mean annual temperature of 17 2 17 4 c must be assumed for the upland environment s

a magmatic hydrothermal lacustrine exhalite from the permian lucaogou formation santanghu basin nw china the volcanogenic origin of fine grained clastic sedimentary rocks abstract shales in the middle permian lucaogou formation in the intracontinental santanghu rift basin have been considered as typical organic rich profundal shales for decades our study of well cores using petrographic microscope and scanning electron microscopy suggests an otherwise complex hydrovolcanic and hydrothermal origin this paper describes characteristics of a particular type of the shales composed of fine grained detrital minerals and lithic grains some of them are orthopyroxene calcite peralkaline feldspars and analcime that are interpreted as derived from peralkaline alkaline carbonatite pyroxenite analcime phonolite and andesite whereas others are quartz dolomite ankerite serpentine and calcite that were precipitated from syndepositional or penecontemporary hydrothermal fluids grain size ranges from 0 001 to 2 mm mostly 0 01 0 1 mm well developed laminae are mostly 0 5 3 mm thick and alternate with tuffaceous dolomicrite the rocks are interpreted as sublacustrine hydrovolcanic deposits which had been altered by syndepositional hydrothermal fluids the interpretation is substantiated by abundant cone shaped stratigraphic buildups on seismic sections in the basin this study shows an ancient example of volcanic hydrothermal deposits in a rift basin

revised chronostratigraphy of recurrent ignimbritic eruptions in dominica lesser antilles arc implications on the behavior of the magma plumbing system ignimbritic eruptions represent catastrophic events due to the magma volume involved and the related consequences on earth s environment in relation with the released gases and the tephra dispersal dominica has been recognized as hosting one of the major ignimbritic eruptions of the last 200 ky in the lesser antilles arc called the roseau tuff but more recent works have evidenced several pumiceous events instead of a single large one here we propose a revised chronostratigraphy of the explosive activity that occurred in the last tens of thousands years based on three field trips new 14c ages detailed lithological and geochemical investigations in particular a precise characterization of trace element glass chemistry this eruptive history reconstruction is mainly based on outcrops along the coast and in the valley since the luxury vegetation in the center of the island mostly precludes sections close to the central volcanic centers we thus confirm that the roseau event has been overestimated and that we may recognize five main ignimbritic events grande savane layou 51 ka grand bay roseau 33 ka grand fond 24 ka we discuss the possible volcanic center at their origin in addition to correlations with some plinian events of lower magnitude that were identified in the roseau valley and in the southern part of dominica this study may help to better constrain the eruptive history of the most active volcanic island of the lesser antilles arc which has important implications on hazard mitigation

direct radiometric dating of the devonian mississippian time scale boundary using the re os black shale geochronometer many phanerozoic time scale boundaries are characterized by oceanic anoxia and mass extinction events with the deposition of black shale the re os isotope system in black shale can be used to provide depositional ages for these rocks thus yielding direct radiometric ages for time scale boundaries we demonstrate that the re os black shale geochronometer can yield precise ages useful for time scale research through study of the devonian mississippian boundary within the exshaw formation canada the re os date determined places the devonian mississippian boundary at 361 3 2 4 ma 2 including uncertainty model 1 mean square of weighted deviates 1 2 in accord with recent calibration interpolated from u pb zircon dates 360 7 0 7 ma for the hasselbachtal section germany

large scale phreatomagmatic silicic volcanism a case study from new zealand abstract pyroclastic deposits of the 20 000 year old wairakei formation occur in the region surrounding lake taupo in the central north island of new zealand recent advances in the correlation of both proximal and distal equivalents of the wairakei deposits show that they were the result of one large eruption the ash layers once covered most of new zealand they are also present in deep sea cores from the sw pacific and on the chatham islands the dispersal and grain size parameters of the ash fall members indicate that their vent area was within the taupo volcano tectonic depression which for a long period has contained a large lake the wairakei eruption is interpreted to have been phreatomagmatic throughout each phase of the eruption sequence generated its own characteristic deposits the sequence of events can be summarized as follows 1 eruption and deposition of a white fine grained bedded fall deposit 2 eruption and deposition of a medium grained pumice fall deposit 3 generation of ultra fine wet ash clouds with a fall deposit accumulating largely as aggregates and accretionary lapilli accompanied by base surges 4 formation of water cooled pyroclastic flows and deposition of an extensive ignimbrite 5 return to a dominantly vertical eruption column and deposition of a medium grained bedded ash fall immediately followed by another wet ultra fine fall deposit charged with accretionary lapilli finally 6 an ignimbrite less widespread than that of phase 4 was produced co ignimbrite fall deposits of fine vitric dust and medium grained pumice were laid down over a huge area there may have been a short hiatus in activity between phases 4 and 5

extensional v contractional origin for the southern menderes shear zone sw turkey tectonic and metamorphic implications the southern menderes massif in southwest turkey consists mainly of orthogneisses and overlying palaeozoic middle paleocene schists and marbles the contact between the two distinct rock types is almost everywhere structural herein named the southern menderes shear zone a s facing high angle ductile shear zone that separates metamorphic rocks of differing grade although there is a consensus that the shear zone was associated with top to the s ssw shearing and is of tertiary age its origin and nature have been highly debated over the last decade some claim the contact is a thrust fault while others have argued for an extensional shear zone integration of field and microstructural data the identification of different fabrics associated kinematics and overprinting relationships with fission track thermochronology and the p t paths of the rocks above and below the shear zone supports the conclusion that the southern menderes shear zone is an extensional shear zone and not a thrust the data are consistent with a model that the exhumation and cooling of the southern menderes massif occurred after a period of extensional deformation pervasive top to the n nne high temperature medium pressure ductile shear structures d 2 deformation overprint an early hp event d 1 deformation the subsequent top to the s ssw greenschist shear band foliation d 3 deformation developed mostly around the orthogniess schist contact and forms the most characteristic features of the massif the top to the n nne structures are attributed to the main alpine constructional deformation that developed during back thrusting of the lycian nappes during the latest palaeogene collision between the sakarya continent and the anatolide tauride platform across the neotethyan ocean the top to the s ssw structures are interpreted to be the result of the exhumation of the massif during the activity of the southern menderes shear zone the presence of these two distinct fabrics with differing kinematics suggests that the southern menderes shear zone operated as a top to the n nne thrust fault during early alpine contractional deformation but was later reactivated with an opposite sense of movement top to the s ssw during subsequent oligocene miocene extensional collapse

post collisional adakite like magmatism in the agvanis massif and implications for the evolution of the eocene magmatism in the eastern pontides ne turkey abstract in the anatolia the caucasus and northwest iran the eocene epoch is characterized by widespread basic to acidic magmatism whose temporal and spatial evolutions and origin are poorly understood in this paper we provide geochronological and geochemical data on a suite of early eocene intrusions from northeast turkey and discuss their origin within a regional tectonic framework post to late collisional moderate to small bodies of quartz diorite and leucogranodiorite as well as later dacite porphyries intrude permo triassic low grade metamorphic rocks in the southern part of the eastern pontides very close to the neo tethyan izmir ankara erzincan suture in places the intrusives display well developed subsolidus foliations indicating on going penetrative deformation during and shortly after emplacement different emplacement depths were inferred based on the contact metamorphic mineral assemblages al in hornblende barometry and igneous textures quartz diorite 14 16 km vs dacitic porphyries 7 km biotite and hornblende ar ar and zircon u pb data indicate that the compositionally and texturally different intrusives were emplaced at 51 ma ypresian three lines of evidence indicate that the early eocene represents a tectonically active time with high exhumation rates 0 6 cm a 1 i the quartz diorite and dacitic porphyries were emplaced at different crustal depths ii the emplacement ages of these texturally distinct intrusive rocks are geochronologically undistinguishable and iii intrusive rocks locally show a well developed foliation the intrusive rocks display high abundances of al 2 o 3 sr ba lrees and low abundances of y sc and hrees and are similar to high silica adakites from supra subduction zone settings the geochemical features imply a residual and or fractionating assemblage rich in hornblende garnet pyroxene and poor in plagioclase all rock types display similar sr nd isotopic characteristics with initial e nd and 87 sr 86 sr values ranging from 1 0 to 1 1 and from 0 70421 to 0 70494 respectively these three coeval rock groups quartz diorite leucogranodiorite and dacite porphyries were generated from a similar source by variable degrees of partial melting and fractionation these data together with those from the literature clearly reveal that the adakitic signature is common in paleocene to early eocene igneous rocks in northern turkey on both sides of the izmir ankara erzincan suture but disappears towards the middle eocene regional geological constraints indicate that the continental collision between the pontides and the anatolide tauride block occurred in the paleocene and that the middle eocene represents a period of major extension characterized by a marine transgression we therefore suggest that the early eocene adakitic magmatism in northern turkey resulted from the presence of a thickened continental crust following the continental collision along the neo tethyan izmir ankara erzincan suture whereas the voluminous middle eocene magmatism was related to extensional collapse of a thickened orogen

sedimentology of the minoan deep sea tephra layer in the aegean and eastern mediterranean the minoan eruption of santorini resulted in deposition of pyroclastic material over a large area of the aegean sea and eastern mediterranean the eruptive activity commenced with a plinian phase which was followed by a phreatomagmatic phase and ended with numerous pyroclastic flows we present a sedimentological study of the minoan ash deposits found in cores taken throughout the region the cores are divided into three groups 1 those from the sub marine slopes immediately surrounding santorini 2 those from the aegean sea where the topography consists of many steep sided basins and 3 those from the eastern mediterranean where the topography is relatively flat and smooth this last group is designated the distal ash zone the deposits from the aegean sea have been remobilised as turbidity currents grain size distribution analysis reveals that these deposits are bimodal the mdo of the coarse population increasing away from source whilst that of the fine population remains uniform irrespective of distance from source the bimodality is caused by a combination of aggregation of fine particles in ash clouds produced during the last two phases of the eruptive activity and mixing of the coarse plinian and fine phreatomagmatic and co ignimbrite deposits within the turbidity current an unusual feature found in two of the cores is a coarse density sorted layer beneath the bouma a division of several turbidite units this is interpreted as an example of a flow head deposit as described by sparks and wilson 1983 the deposits from the distal ash fall zone are fine grained and unimodal containing phreatomagmatic and co ignimbrite material they show only very minor remobilisation of the original air fall ash due to the flat topography of the area the mdo of the deposit remains uniform irrespective of distance from source and is very similar to that of the fine population found in the bimodal aegean deposits this is interpreted as the result of aggregation of fines in the phreatomagmatic and co ignimbrite ash clouds the deposits in both areas have been extensively bioturbated a study of dispersed ash in the cores to reconstruct the original thickness of the ash layers suggests that ash layers less than 0 62 cm thick will be completely dispersed in the surrounding sediment whilst those thicker than 2 5 cm will be preserved as discrete layers the base being unaffected by bioturbation the deposits on the submarine slopes of santorini were not originally deposited as air fall ash but are derived from the erosion of coastal exposures of non welded ignimbrite they form storm sand layers and are typical of the type of deposit that may be formed by rapid erosion of fresh pyroclastic material after the eruption of an island arc volcano

kinematics of the central taurides during neotethys closure and collision the nappes in the sultan mountains turkey in the central taurides the sultan mountains comprise in ascending order the cimendere unit and the aksehir doganhisar cay nappes composed of metasedimentary sequences deposited from cambrian to tertiary the overthrust of the cay nappe on the lutetian celeptas formation representing the uppermost stratigraphic position in the cimendere unit indicates that the latest nappe emplacement occurred during the middle eocene the oligocene and miocene rocks are in post tectonic facies in the west central taurides the kinematic data from these nappes related to closure of the neotethys reveal a top ne shear sense in the northwest part and a top se shear sense in the southeast part of the sultan mountains the sultan mountains are located in the north part of the isparta angle which was tectonically assembled by the lycian hoyran beysehir hadim and antalya allochthons on the bey daglari and anamas akseki autochthons from the latest cretaceous to the late pliocene the previous paleomagnetic data showed that the west and east subsections of the isparta angle were subjected to post eocene 30 40 anticlockwise and clockwise rotations respectively in consideration of these paleomagnetic data the kinematic data measured in the sultan mountains might be restored into approximately e w trending linear fabric associated with a top e shear sense these new kinematic data from the nappes in the sultan mountains disagree with the existing tectonic models that suggest n s nappe translation over the central taurides during the latest cretaceous middle eocene the alternative tectonic model for the antalya nappes in the core of the isparta angle related to east west compression suggests westward and eastward nappe emplacements on the surrounding autochthons however the new kinematic data presented here point consistently to a top e shear sense in all tectonostratigraphic units in the sultan mountains currently located in the north part of the anamas akseki autochthon

tectonic transport directions of the lycian nappes in southwest turkey constrained by kinematic indicators abstract the orientation asymmetry and cross cutting relationships of the structures along the contact zone between the lycian nappes and the menderes massif suggest the presence of three deformation phases in the milas region of southwest turkey the first deformation phase d1 is characterized by a ductile deformation with top to the ne sense of shear structural data of the first deformation measured along the uppermost part of the menderes massif and the base of the lycian nappes suggest that the lowermost unit of the lycian nappes was emplaced initially from southwest to northeast onto the menderes massif during the early eocene the second deformation phase d2 is also ductile in nature and is characterized by an e w trending stretching lineation with a bivergent sense of shear which is probably related to the load of the overlying nappes a third deformation phase d3 is characterized by south dipping normal faults with top to the s sense of movement this third deformation phase can be related to southward movement of the lycian nappes along a low angle decollement zone the tectonic contact between the menderes massif and the lycian nappes and their strongly deformed rocks are unconformably covered by approximately flat lying coal bearing early middle miocene sedimentary rocks which constrains the upper time limit for all three deformation phases

late quaternary explosive silicic volcanism on st lucia west indies many explosive eruptions of dacitic magmas have occurred on st lucia during the late quaternary these have produced widespread aprons and fans of pumice flow and ash flow deposits radiating around the central highlands with co eruptive air fall and surge layers interbedded with palaeosols and epiclastic deposits vents in the highlands have not been located because of the dense tropical jungle but we suspect they are now plugged by lava domes surrounded by aprons of block and ash flow deposits young magmatically related dacitic lava domes have been extruded in the qualibou depression the pumice succession can be divided into older quartz poor deposits forming the choiseul pumice and younger crystal rich deposits with abundant large quartz which are called the belfond pumice the choiseul pumice groups together scattered remnants of the products of many eruptions of different low silica dacitic magma types the belfond pumice is the product of several eruptions of a high silica magma type and 14 c ages have dated these between 20900 to 34200 years b p the pumice flow deposits occur as small volume valley fills a granulometric study of belfond pumice flow deposits shows them to be strongly depleted in finer ash and vitric components it is suggested that the narrow winding and vegetated valleys on the island locally induced turbulence and the flows moved with large highly fluidized and inflated heads resulting in substantial loss of fine vitric ash one ash flow deposit which is extremely rich in crystals and carbonized vegetation is highly depleted in fines and shows enhanced vitric losses this flow may have been a much more violent ash hurricane or blast which surmounted topography ingesting large amounts of lush vegetation ignition of this released the large quantities of gas needed to elutriate most of the fines a model is suggested for the recent volcanic activity on st lucia in which separate batches of silicic magma each having a distinctive petrological and chemical character rose into high level chambers over a large area eruptions of volatile rich magma led to highly explosive pumice forming activity from vents in the central highlands degassed and more crystal rich magma was extruded later from the same vents or in the attenuated flank of the qualibou depression to from lava dome complexes

origin and tectonic setting of some melange units in turkey a geologic study of three different melange belts in turkey revealed that the melange units in these belts were formed by gravity sliding in basins underlain by continental basement rather than by tectonic crushing in trenches mafic volcanic activity is a characteristic feature of such basins which are located on continental margins adjacent to tectonically active belts the peridotite and gabbro blocks of the melange units were transported but some of the basalts radiolarites and mudstones originated within the basins and hence are not part of an ophiolite suite

ignimbrite depositional facies the anatomy of a pyroclastic flow a model is presented for the depositional regimes in a pyroclastic flow to explain the origin of facies in the taupo ignimbrite and to compare these with other published examples in this model a pyroclastic flow consists of a head a body and a tail the head which is where fluidization caused by air ingestion occurs generates layer 1 deposits on lithological grounds these are divided into layers 1 p which is fines depleted and rich in pumice and 1 h which is fines depleted and rich in lithics and crystals layer 1 p represents material thrown forwards from the flow head and is termed the jetted deposits layer 1 h represents material sedimented from within the flow head and is termed the ground layer the body represents the bulk of the flow and the tail is its trailing part which is slowed by ground friction these parts generate the layer 2 deposits which include the valley pond ignimbrite and its associated ignimbrite veneer deposit localized depositional modes within the body and tail generate distinctive coarse pumice concentration zones and pumiceous lee side lenses behind obstacles at its outer limits all of the flow on interfluves is affected by air ingestion fluidization producing the distant facies which combines features of both layer 1 and 2 deposits one important conclusion of this work is that the thicknesses and compositions of the various facies are not related in any simple way to the thickness and composition of the parent flow

submarine volcaniclastic rocks in this chapter we are concerned with underwater volcaniclastic eruptions and products as well as pyroclastic flows and debris generated on land and transported by mass flowage into the sea submarine fallout deposits derived from land based eruptions are treated in chapter 7 clastic materials redistributed as mass flows or turbidity currents originating from the rapid build up of tephra and epiclastic volcanic debris along coastal parts of volcanoes are also discussed in various places throughout the text e g chap 13

sedimentary signatures of the entrance of coarse grained volcaniclastic flows into the sea the example of the breccia units of the las palmas detritic formation mio pliocene gran canaria eastern atlantic spain abstract the transformations of volcaniclastic gravity flows entering the sea remain poorly understood they are recorded by sedimentary signatures in the volcaniclastic sedimentation of the mio pliocene las palmas detritic formation lpdf of the volcanic island of gran canaria these gravity flows are contemporaneous with an erosive period on the island succeeding the emplacement of the fataga volcanic group and the beginning of the evolution of the roque nublo stratovolcano the sedimentary section that crops out at the mouth of a paleobarranco at las cuevas del guincho comprises subtidal calcareous and clastic sediments affected by wave and storm action units 1 and 3 beach gravels unit 4 volcaniclastic deposits represented by reworked phonolitic pyroclastic deposits unit 1 breccia deposits that contain juvenile and phonolitic gravels and blocks mainly incorporated at the shoreline unit 2 and a debris avalanche deposit at the top unit 5 the breccia deposits display a reversely graded base which disappears distally as a result of seawater incorporation and liquidization of the volcaniclastic mass and mixing with marine sediment this breccia unit is interpreted as having been emplaced by a granular mass flow after transformation of a block and ash flow deposit that entered the sea in the debris avalanche deposits thermal quenching of juvenile basaltic lava clasts and large inclined clastic intrusions of underlying marine sediments suggest that the debris avalanche entered the sea rapid subaqueous emplacement of the granular mass flow and of the debris avalanche deformed the sedimentary substratum water incorporation reduced the influence of the volcaniclastic flows on the substratum ams data confirm the effect of water ingestion and correlative loss of cohesion and allow also reconstruction of paleoflow directions that were normal to the paleoshoreline of the northern coast of gran canaria all these volcaniclastic gravity flow deposits and their textural characteristics are particularly useful in the reconstruction of processes that occur at the subaerial submarine transition and for the location of ancient shorelines

the behaviour of subaerially produced pyroclastic flows in a subaqueous environment evidence from the roseau eruption dominica west indies abstract the roseau tephra 30 000 yrs b p with its source on the island of dominica represents the largest eruption in the caribbean in the last 200 000 years pyroclastic flows generated by the eruption flowed offshore into the grenada basin giving rise to a widespread layer of sediment gravity flow deposits on land the flow deposits are valley ponded and their granulometric characteristics allow them to be classified as weakly fines depleted ignimbrites offshore the characteristics of the sediment gravity flow deposits are consistent with deposition by numerous small scale events rather than a single large scale event a comparison of the on land and offshore deposits reveals an increase in the crystal lithic ratio in the latter this change can be best explained by the fragmentation of hot pyroclastic material as the subaerial flows mixed with water mixing and fragmentation occurred not at the air water interface but as flows descended the steep submarine slopes of the island of dominica

calderas or gravity slide structures in the lesser antilles island arc abstract large arcuate depressions up to about 10 km in diameter on the back arc side of st lucia dominica and st vincent in the lesser antilles arc are discussed the qualibou depression on st lucia has been previously described as a caldera partly because it was believed to be the source of ignimbrites on the island remapping and stratigraphic studies of these ignimbrites show they were not erupted from the depression but from central vents in the highland rainforests and are much younger dominica is geologically similar and has two scarped depressions at the southern end of the island soufriere volcano st vincent has a prominent arcuate scarp opening to the west the southern half of which has been buried under the youngest volcanic products of the volcano we interpret these structures as the root zones of gravity slides perhaps eruption related and triggered by magmatic inflation post slide activity lava domes and fumaroles has occurred within them due to reduction in lithostatic load and pressure release on the flanks of these island volcanic complexes the presence of these structures only on the western coasts is correlated with the steeper 9 slopes into the grenada basin in contrast to the 1 submarine slopes of the atlantic side

obduction subduction and collision as reflected in the upper cretaceous lower eocene sedimentary record of western turkey late cretaceous early eocene tethyan evolution of western turkey is characterized by ophiolite obduction high pressure low temperature metamorphism subduction arc magmatism and continent continent collision the imprints of these events in the upper cretaceous lower eocene sedimentary record of western anatolia are studied in thirty eight well described stratigraphic sections during the late cretaceous period western turkey consisted of two continents the pontides in the north and the anatolide taurides in the south these continental masses were separated by the izmir ankara neo tethyan ocean during the convergence the pontides formed the upper plate the anatolide taurides the lower plate the arc magmatism in the pontides along the black sea coast is biostratigraphically tightly constrained in time between the late turonian and latest campanian ophiolite obduction over the passive margin of the anatolide tauride block started in the santonian soon after the inception of subduction in the turonian as a result large areas of the anatolide tauride block subsided and became a region of pelagic carbonate sedimentation during the campanian the leading margin of the anatolide tauride block was buried deeply and was deformed and metamorphosed to blueschist facies during campanian times the campanian arc volcanic rocks in the pontides are conformably overlain by shaley limestone of maastrichtian palaeocene age however maastrichtian sedimentary sequences north of the tethyan suture are of fore arc type suggesting that although arc magmatism ceased by the end of the campanian age continent continent collision was delayed until palaeocene time when there was a change from marine to continental sedimentation in the fore arc basins the interval between the end of the arc magmatism and continent continent collision may have been related to a northward jump of the subduction zone at the end of campanian time or to continued obduction during the maastrichtian

processes of late cretaceous to late miocene episodic thrust sheet translation in the lycian taurides sw turkey the lycian taurides of sw turkey consist of an allochthonous mesozoic passive margin succession that was episodically detached from its autochthon and translated southeastwards between latest cretaceous to late miocene times a combination of structural analysis sedimentology palaeontology and geochemistry allows subdivision of this orogenic event into 1 latest cretaceous trench passive margin collision causing ophiolite obduction and detachment of the koycegyiz thrust sheet 2 mid late eocene continent continent collision renewing southeastwards thrusting and causing detachment of the teke dere thrust sheet and yavus thrust sheets 3 miocene extensional collapse of the orogen with southeastwards translation of the allochthon coeval with rift basin formation in the hinterland

fluidization of wet sediments during the emplacement and cooling of various igneous bodies during the emplacement and cooling of igneous bodies fluidization of wet sediment by water vapour may occur by heating or by pressure relief during the opening of fractures momentary fluidization causes sediment reconstitution and local transport continuous fluidization can result in substantial sediment displacement theoretical considerations show that fluidization due to heating is not likely to occur at depths where pressure is much greater than 312 bars studies of the emplacement of sills of andesite ayrshire fluid rhyolite ramsey island and viscous rhyolite moelwyn hills recognize a wide range of phenomena attributable to wet sediment fluidization and in places modify existing interpretations the transgressive bases of the subaqueously welded ash flow tuffs of the capel curig volcanic formation are consistent with emplacement attended by fluidization of the subjacent sediment evidently fluidization is a means by which large volumes of wet sediment can be replaced by igneous material with minimal disturbance of the remaining host also fluidization can result in exceptionally complex contact relationships between sedimentary host and intrusive rocks and can cause fractures formed during cooling to be thoroughly pervaded by sediment fluidization is commonly associated with the formation of peperites

lycian melange southwestern turkey an emplaced late cretaceous accretionary complex the lycian thrust belt is an important part of the tethyan orogenic belt in the eastern mediterranean region it includes a unit of internally disrupted thin skinned thrust sheets layered tectonic melange and a melange rich in ophiolitic material ophiolitic melange the layered tectonic melange is dominated by mesozoic distal deep water sedimentary rocks and the ophiolitic melange includes disrupted thrust sheets of early mesozoic shallow water limestone and blocks of basalt of both mid ocean ridge and within plate geochemical affinities a complete record of closure of a tethyan oceanic basin began with late cretaceous intraoceanic subduction followed by latest cretaceous trench continental collision and ended with mid tertiary continental collision and orogenic collapse

neotethyan closure history of western anatolia a geodynamic discussion this paper addresses the lithosphere scale subduction collision history of the eastern termination of the aegean retreating subduction system i e western anatolia although there is some general consensus on the protracted subduction evolution of the aegean since the early cenozoic at least correlation with western anatolia has been widely debated for more than several decades in western anatolia three main tectonic configurations have been envisaged in the past years to reconstruct slab dynamics during the closure of the neotethyan oceanic realm since the late cretaceous some authors have suggested an aegean type scenario with the continuous subduction of a single lithospheric slab punctuated by episodic slab roll back and trench retreat whereas others assumed a discontinuous subduction history marked by intermittent slab break off during either the campanian ca 75 ma or the early eocene ca 55 50 ma the third view implies three partly contemporaneous subduction zones our review of these models points to key debated aspects that can be re evaluated in the light of multidisciplinary constraints from the literature our discussion leads us to address the timing of subduction initiation the existence of hypothetical ocean basins the number of intervening subduction zones between the taurides and the pontides the palaeogeographic origin of tectonic units and the possibility for slab break off during either the campanian or the early eocene thence we put forward a favoured tectonic scenario featuring two successive phases of subduction of a single lithospheric slab and episodic accretion of two continental domains separated by a continental trough representing the eastern end of the cycladic ocean of the aegean the lack of univocal evidence for slab break off in western anatolia and southward younging hp lt metamorphism in continental tectonic units from 85 70 to 50 ma in the late cretaceous palaeogene period suggests continuous subduction since 110 ma marked by roll back episodes in the palaeocene and the oligo miocene and slab tearing below western anatolia during the miocene

isolated pods of subaqueous welded ash flow tuff a distal facies of the capel curig volcanic formation ordovician north wales acidic welded tuffs of the capel curig volcanic formation were deposited from ash flows that transgressed from a proximal subaerial to a distal submarine environment isolated pods of welded tuff enveloped by marine sediments represent a distal facies of the formation deposited beyond the limits of the continuous ash flow tuff sheets various mechanisms for the separation of the tuff pods from a parent flow are discussed and it is concluded that it is most likely that the formation of the pods was due to disruption of a subaqueous ash flow during transport rather than by downslope collapse at the front of a previously deposited ash flow tuff sheet

origin of the allochthons in the lycien belt southwest turkey abstract the lycien belt of southwest turkey lies between the menderes metamorphic massif to the northwest and the bey da lari carbonate platform to the southeast the belt is characterized by thrust faults melanges and peridotites stratigraphic and structural relationships suggest that the allochthons of the lycien belt were derived from two distinct tectonic terrains the koyce iz and elmali thrust slices were from south of the massif the tefenni nappe originated far north of the menderes massif the latter incorporates platform sediments melanges and ophiolites represent the edge of a continental platform opening into the tethys oceanic realm correlation of the elmali and koyce iz thrust slices and autochthonous tectonic elements shows that the lycien belt between the menderes massif and the bey da lari was a tectonically active zone of weakness the belt which may be at the extension of the ionian zone was subjected to repeated cycles of deep basin subsidence and intense deformation in triassic jurassic early cretaceous and tertiary times the tefenni nappe passed over the menderes massif and emplaced onto the lycien terrain in the late eocene the lycien terrain was subsequently fragmented and overthrusted southeastward onto the bey da lari shelf sediments in late miocene time

quaternary fluvial tufas of sarikavak area southwestern turkey facies and depositional systems abstract in the quaternary sarikavak fluvial tufa deposits situated in south western turkey different facies have been identified and their mutual relationships have been unravelled this tufa formation is located at the northern part of acigol graben the development of the sarikavak tufas represents typical fluvial and fluvio palustrine environments in total eight tufa lithofacies have been differentiated namely moss tufa facies oncolitic tufa facies stromatolitic tufa facies phytoclastic tufa facies intraclastic tufa facies extra formational clastic tufa facies sapropelitic tufa facies and palaeosol preliminary u th datings indicate that these deposits formed prior to 219 ka and continued until 80 ka mis 7 till 5 13c signatures 0 78 to 1 63 v pdb best can be explained by limestone dissolution processes or respiration from c4 plant vegetation into the soil or both for that reason the sarikavak tufa deposits can be classified as travitufa which precipitated in a distal facies system of travertine occurrences 18o values 7 49 to 10 83 v pdb of the whole data set reflect some significant changes which is interpreted in terms of temperature variations reflecting warm and cold periods among mis 7 interglacial mis 6 glacial and mis 5 interglacial the development of the sarikavak tufa deposits are related to the maymundagi fault that borders the acigol graben in the north this fault and its synthetic fault segments play a pivotal role with regard to the palaeo flow direction of water and control the basin topography these structural structures are likely responsible for all active and ancient springs in the study area as well as their respective carbonate precipitates

insights from the talysh of azerbaijan into the paleogene evolution of the south caspian region the age and mode of formation of the south caspian basin are disputed an 10 km thick predominantly middle eocene clastic and volcanic succession is exposed in the talysh mountains of azerbaijan at its western margin here high k alkali basalts pass laterally to the east and southeast into volcanogenic sandstone dominated turbidity current and debris flow deposits these southeasterly directed depositional systems accumulated in water depths generally greater than 200 m and fed directly into the western south caspian basin new ar ar ages cluster around 39 ma with an upper 1400 m thick volcanic interval being deposited in 2 2 0 2 m y we interpret that this rapid deposition and magmatism records a major back arc extensional transtensional event in the talysh north of the north dipping neotethyan subduction zone this event is recognized across much of southwest asia and may indicate a period of significant basin formation within the adjacent south caspian basin a transition into upper eocene lower oligocene strata dominated by fine grained turbidity current and hemipelagic sediments with slope instability features is interpreted to mark the end of rifting and volcanism in the talysh and the start of the arabia eurasia collision overlying oligocene coarse clastic rocks are interpreted as the erosional products of localized topography created by the further propagation of compressional deformation into the talysh region

entrance of hot pyroclastic flows into the sea experimental observations the entrance of hot pyroclastic flows into water has been observed in a series of experiments in which shooting granular flows of hot ignimbrite ash 403 c of bulk density near that of water run down a smooth chute and enter a water filled tank at an angle of 26 flows of relatively cool ash 250 c mixing across the water surface over some distance from shore generates steam explosions forming fountains of wet and dry ash and convectively rising fine ash plumes steam explosions increase in strength and lateral extent towards higher ash temperatures and mass fluxes the explosions generate water waves that remain driven by massive fountain fallout across some distance from shore the ash fountains feed pyroclastic surges which advance down tank over water at high speeds underwater plumes of sediment falling from the ash fountains and surges drop coarse load onto the floor whereas the finer load forms a turbidity current high temperature and poor size sorting of pyroclastic flows are key parameters that determine the processes of interaction with water and the associated hazards poor sorting allows for the formation of ash cloud surges moving over water even from cool flows high temperatures cause littoral explosions and facilitate extensive mass transport over water all flows generate tsunami waves by different mechanisms

application of actualistic models to unravel primary volcanic control on sedimentation taveyanne sandstones oligocene northalpine foreland basin abstract this work is focused on the taveyanne sandstones gres de taveyanne an oligocene volcaniclastic turbidite sequence cropping out in the northern alpine molassa between se france and central switzerland with the aim to investigate the temporal relationship between volcanic activity and sediment supply detailed stratigraphic sedimentological and petrographic xrd analyses on mudstones and point counts on sandstones studies conducted on three sections col de l oulette and flaine in se france taveyanne in sw switzerland allow a discrimination of three main facies among which only one is extremely enriched in volcaniclastic detritus and characterized by features similar to those of disaggregated pyroclastic density current deposits the other two facies are characterized by variable to no volcanic detritus but supplied by crystalline and sedimentary detritus such sediment trends are similar to those of modern volcanically controlled source to sink systems this allows a reinterpretation of the taveyanne sandstones as a syn volcanic turbidite system episodically supplied by large amounts of volcanic detritus which periodically modified the drainage paths moreover the well known temporal and spatial persistence of such modifications in modern settings leads to conciliate the syn volcanic supply with the location of the volcanic centers in the internal part of the alps without invoking particular climatic and tectonic conditions controlling foreland sedimentation