methana the westernmost active volcanic system of the south aegean arc greece insight from fluids geochemistry abstract an extensive geochemical survey of the fluids released by the volcanic geothermal system of methana was undertaken gases were characterized based on the chemical and isotopic helium he and carbon c analysis of 27 samples carbon dioxide soil gas concentration and fluxes were measured at 179 sampling sites throughout the peninsula forty samples of thermal and cold groundwaters were also sampled and analysed to characterize the geochemistry of the aquifers gases of hydrothermal origin gave a preliminary geothermometric estimate of about 210 c the he isotope composition indicated mantle contributions of up to 40 and the c isotope composition of co 2 indicated that it predominantly 90 originated from limestone decomposition the groundwater composition was suggestive of mixing between meteoric and hydrothermally modified sea water endmembers and water rock interaction processes limited to simple rock dissolution driven by an increased endogenous co 2 content all of the thermal manifestations and anomalous degassing areas although of limited extent were spatially correlated with the main active tectonic system of the area the total co 2 output of the volcanic system has been preliminary estimated to be less than 0 05 kg s 1 although this value is very low compared to those of other volcanic systems anomalous co 2 degassing at methana which is currently restricted to limited areas and at present is the only volcanic risk of the peninsula is a potential gas hazard that warrants further assessment in future studies

three dimensional p and s velocity structure in the coalinga region california the coalinga earthquake sequence of 1983 provided a unique opportunity to perform a three dimensional velocity and hypocenter inversion in an area of complex three dimensional structure dominated by folding and blind thrusts additionally since other varied geological and geophysical studies have been completed in this area the three dimensional inversion solution could be compared to other interpretations inversion of 7696 p and 1511 s first arrivals from earthquakes and 696 p first arrivals from refraction shots produced a three dimensional velocity model with grid spacing of 1 2 km in the hypocentral area the overall shape and location of velocity features correspond well to the mapped surface geology the three dimensional inversion yields details of folds where the resolution is good and the general shape where resolution is lower the amounts of structural relief inferred for the local folds are similar to values inferred from geologic data the three dimensional velocity solution has several distinctive features there is a linear high velocity body 6 1 6 5 km s about 25 km long from 6 to 8 km depth that may represent a fragment of coast range ophiolite a shallow low velocity zone lvz which extends for 20 km along the fold axis at about 6 km depth and correlates with lvzs observed in both the refraction and the reflection data may indicate high pore pressure caused by lateral compressive strain deeper lvzs occur within inferred franciscan material and are characterized by horizontal or southwest dipping zones of varied thickness 4 8 km wide and 5 10 km long these lvzs may represent multiple thrust faults their locations and geometry are consistent with thrust faults inferred with seismic reflection data the three dimensional velocity solution compares well to prior two dimensional seismic reflection and refraction models and observed gravity the shape of the inferred sedimentary section agrees well with the reflections from the cenozoic strata compared to the refraction model the three dimensional solution has similar velocities and similar locations of velocity features but is more detailed in the hypocentral zone where it uses more data the gravity computed from the three dimensional velocities is similar to the observed gravity in both shape and amplitude both a simple one dimensional initial model and a complex initial model derived from the refraction interpretation were tried a simple starting model gave the best results the s velocity solution has different resolution than the p velocity solution because it uses a different set of stations and it has lower resolution because it uses fewer arrival times while the general patterns of velocity variation are similar for both vp and vs the vs solution tends to have more smearing of velocity features and can have somewhat different locations of velocity features

3d crustal structure in the neotectonic basin of the gulf of saronikos greece an on offshore seismic network consisting of 36 three component stand alone digital stations was deployed in the area of the saronikos gulf in the vicinity of athens greece in the fall of 2001 in the present study from an initial set of more than 1000 micro earthquakes 374 were selected and 6666 p and s wave arrivals were inverted based on a 3d linearized tomography algorithm in order to determine the 3d velocity structure of the region the resulting 3d velocity distribution in agreement to the micro seismicity distribution reflects the saronikos structure down to a depth of 12 km so the neotectonic basin of the saronikos gulf is divided in two parts by a central platform which implies the existence of a nne ssw trending rupture zone this zone is probably the offshore extension of a large thrust belt dominating the adjacent onshore areas due to their different structure the two basins are dominated by different velocity values in comparison to the central platform the western part is characterised by higher seismic activity than the eastern one furthermore the western saronikos gulf is divided in a northern and a southern part by a well defined rupture zone trending e w this seems to be the extension of the corinthiakos gulf fault zone at the depth of 17 km the velocity increases considerably and the crustal thickness is restricted down to 20 km this dunexpectedt low thickness in the region of saronikos gulf seems to be the result of the extensional stress field which dominates the region as well as of the emergence of the mantle material along the volcanic arc which clearly appears at the depth of 12 km yet the lack of deep events and hence the poor resolution below the depth of 17 km does not support a definite conclusion about the crust mantle boundary in this region d 2005 elsevier b v all rights reserved

upper holocene sea level changes in the west saronic gulf greece abstract along the peloponnesian coast of the saronic gulf and on the coast of aegina and poros islands submerged coastal geomorphological features related directly with submerged ancient coastal constructions indicate three distinct sea levels submerged tidal notches incised on the carbonate basement beachrocks formed in the intertidal zone and archaeological indicators such as the ancient harbour installations in kenchreai and epidaurus and on aegina island the extended coastal buildings and constructions in agios vlasis psifta and palaiokastro methana and vagionia on poros island are used to determine the age and magnitude of submersion and the extent of the upper holocene marine transgression by the correlation of geomorphological historical and archaeological indications three distinct sea levels were identified at 3 30 0 15 m 0 90 0 15 m and 0 55 0 05 m initial change in sea level occurred definitely after ad 400 100 the intermediate change is dated between ad 1586 and 1839 and the most recent change after 1839 sea transgression followed a long period of sea level stability which lasted at least 2200 years from the middle bronze age to the late roman period

archean magmatism in the kaminak lake area district of keewatin northwest territories ages of the carbonatite bearing alkaline complex and some host granitoid rocks u pb zircon data obtained on the ion microprobe shrimp have yielded an age of 2700 11 ma for tonalite of the kaminak batholith where it is intruded by a carbonatite bearing alkaline complex at kaminak lake northwest territories canada and a crystallization age of 2659 5 ma for the alkaline intrusion relatively undisturbed age spectra determined by laser probe 40ar 39ar analysis of hornblende from a gabbro and from a second tonalite of the batholith yielded cooling or minimum ages of 2727 14 and 2599 9 ma respectively spectra for hornblendes from two other gabbros suggest overprinting more recent than 2 04 ga with a minimum cooling age of 2 69 0 09 ga in one case and with incorporation of excess argon a maximum cooling age of 2 80 0 03 ga in the other correlation of these data with those recently reported by other workers indicates that the volcanic sequence and the plutonic granitoid units of the kaminak lake granitoid greenstone belt are approximately coeval plutonic units bot

an autochthonous glossopterid flora with latest permian palynomorphs and its depositional setting in the dicynodon assemblage zone of the southern karoo basin south africa article i nfo the discovery of a plant fossil assemblage situated 70 m below the vertebrate defined permian triassic boundary allows for the characterization of part of the late permian landscape in the southern karoo basin the megafloral and microfloral assemblages are preserved in association with an o horizon above a weakly developed palaeosol exposed in both new and old wapadsberg pass eastern cape province south africa stable isotope geochemical evidence indicates that pedogenesis occurred under conditions of a high regional water table and the palaeosol was entombed by overbank or avulsion deposits in an aggradational landscape that includes tuffite the low diversity macroflora contains gymnospermous glossopteris and sphenopsid phyllotheca trizygia elements that include vegetative axial leaf and reproductive strobilar remains glossopteris leaves are microphyllous and may reflect the taxon s physiological response to purported climate perturbation or wetland edaphic conditions and exhibit a range of plant animal interactions palynological residues contain sphenophyllalean cuticles and the microfloral assemblage is consistent with a low diversity glossoperid dominated woodland with a sphenopsid understory extrabasinal elements include representa tives of peltasperms alisporites corystosperms falcisporites and conifers lueckisporites pollen conforming to lunatisporites pellucidus is present in the assemblage and is considered an indicator taxon for the latest permian to early triassic when compared to palynological assemblage zones in australia the wapadsberg pass flora is assigned a late changhsingian age and therefore represents the youngest autochthonous glossopteris dominated flora to be reported from gondwana these results extend a palynostratigraphic framework across the southern hemisphere that complements other zonations presently applied to the karoo basin succession

radiometric dating demonstrates that permian spore pollen zones of australia and south africa are diachronous abstract the well refined permian palynozonation of western and eastern australia is the current standard biostratigraphic scheme for the southern hemisphere but intra gondwanan floristic provincialism means that several stratigraphically useful palynomorph taxa are rare or absent elsewhere in gondwana radio isotopic ages for both australia and the main karoo basin of south africa demonstrate that key marker taxa appear diachronously in the two countries or they are absent in one of the countries the establishment of new plant taxa in the gondwanan permian realm was strongly tied to palaeolatitude with floral distributions primarily affected by temperature precipitation and seasonality this spatio temporal variation of floras hinders global biostratigraphic correlations both south africa and australia have excellent long ranging permo triassic terrestrial sedimentary successions and although vertebrate biostratigraphy has been the focus of much research endeavour in the south african karoo palynological studies have lagged accordingly a new south african palynozonation should be established that is based on the first appearances of key index taxa in the main karoo basin rather than elsewhere in gondwana in the interim the diachronous ranges of palynomorphs must be considered when correlating south african rocks to other global sections by means of the australian spore pollen zonation

lithostratigraphic subdivision of the karoo rocks of the luwegu basin tanzania and their biostratigraphic classification based on microfloras macrofloras fossil woods and vertebrates for the first time a comprehensive stratigraphic classification of the karoo deposits of the luwegu basin in southern tanzania is presented the karoo strata attain a total thickness of almost 6000 metres and are composed of deltaic lacustrine and fluvial deposits the sedimentary sequence has been subdivided into nine major lithostratigraphic units the results of biostratigraphic investigations microfloras macrofloras fossil woods vertebrates indicate that the karoo sequence ranges in age from upper permian to lower jurassic the palynological sequence comprises microfloras of the upper permian the upper triassic onslow and ipswich type and the lower jurassic their age is assessed from correlation with palynofloras of malagasy australia and zimbabwe resulting from this regional as well as intercontinental correlations with the karoo strata of east and south africa the karoo type strata of north africa and the gondwana sequences of australia and india can be proposed furthermore on the base of radiometric datings of hitherto unknown occurrences of volcanic rocks a karoo volcanism and an early tertiary volcanism can be distinguished

no gap in the middle permian record of terrestrial vertebrates during the permian tetrapods showed a major transition from basal synapsid dominated faunas in the first half to therapsid dominated faunas in the second the transition was significant in marking the beginning of richer and more complex communities a precursor to modern terrestrial ecosystems this changeover may have been gradual or abrupt but its study has been complicated by the postulated occurrence of a substantial hiatus in the fossil record termed olson9s gap which obscured the nature of the turnover new evidence from redating of key tetrapod bearing units of the american southwest and european russia confirms that there is no gap in the fossil record of permian tetrapods indeed evidence for substantial sampling bias in the permian tetrapod fossil record as a whole is queried

sm nd studies of archaean metasediments and metavolcanics from west greenland and their implications for the earth s early history metasedimentary and metavolcanic rocks from the archaean of west greenland have been examined for evidence of crustal components greater than 3 8 ga in age and for their compatibility with the presently adopted bulk earth sm nd parameters sm nd isotopic data have been obtained for the garbenschiefer metagabbro unit metasediments from the isua supracrustal belt gneisses interior to the isua belt and metasediments from the malene supracrustal belt using estimates of emplacement age t of between 3 77 and 3 67 ga for the parental volcanics to the garbenschiefer unit initial143nd 144nd ratios yield positiveendt values between 1 0 and 3 1 relative to the chur parameters for seven out of eight samples model sm nd ages for the isua gneisses and metasediments are only compatible with their estimated stratigraphic ages if their sources were ca 2end relative to chur at those times similarly model sm nd ages for the malene samples are only compatible with stratigraphic age constraints when based on a source evolution with positiveendt implications of these results for the early development of the earth s mantle are discussed

the methana volcano geothermal resource greece and its relationship to regional tectonics abstract geophysical methods of analysis were applied in order to investigate the deep structure and the geothermal potential of the methana volcano ne peloponnesus greece the study is based on a re evaluation and reinterpretation of legacy magnetotelluric mt data with modern analysis methods as well as 3 d inversion of aeromagnetic data constrained by in situ measurements of magnetic susceptibility magmatic systems are located in regions of active tectonic processes that often play a controlling role the mt method is effective in delineating low resistivity functional elements of volcanic systems such as magma chambers vents thermal fluid reservoirs and thermal fluid circulation conduits the latter two of which are typically associated with active faults the aeromagnetic data can assist in mapping the configuration hence emplacement modes of volcanic rocks at depth accordingly the joint interpretation of these lines of evidence together with structural and geochemical information is expected to allow insight into the influence of contemporary tectonics on the inception and evolution of the volcano the contemporary stress field is mainly extensional nne ssw oriented and overall homogeneous in the area of methana it allows for the formation of wnw ese north easterly dipping normal faults w e faults consistent with the synthetic dextral r shear direction of riedel s shear theory and nw se faults consistent with the antithetic sinistral r shear direction all such features have been mapped on methana peninsula the magnetotelluric data imaged a significant geothermal reservoir developing around an intersection of the three active fault zones normal r and r at depths of 1 1 5 km below the centre of the peninsula as well as elongate epiphenomenal conductivity anomalies associated with the circulation of thermal fluids along all three fault zones the 3 d magnetic susceptibility model strongly suggests that the intrusion and emplacement of magmas were guided by the same active fault zones with particular reference to the r and r shears whose influence is imprinted on the configuration of volcanic rocks at depth the joint interpretation of all lines of evidence indicates that magmatism and volcanism at methana are almost completely controlled by tectonic activity in a manner analogous to the situation of the large santorini volcanic complex it also indicates that the reservoir is replenished through the weak permeable zone created by the intersection of the r and r shears which is very probably collocated with the main vent of intrusive magmatic activity and may connect with a shallow magma chamber at depths greater than 4 5 km the apparently common origin and similarities differences in the circulation paths of thermal fluids may amply explain both the individual characteristics and similarities differences in the chemical composition of thermal spring discharges which have been reported by hitherto geochemical investigations

pennsylvanian and cisuralian palynofloras from the los sauces area la rioja province argentina chronological and paleoecological significance abstract three outcrops of the libertad and sauces formations from the los sauces area la rioja province western argentina yielded the nine palynoassemblages studied here two assemblage zones are defined on the basis of the stratigraphic distribution and ranges of seventy five species of palynomorphs 42 species of spores 32 pollen taxa and one fungus only thirteen species are common to both assemblages and ten species are first records for the paganzo basin assemblage 1 from the libertad formation is dominated by trilete spores of cristatisporites lycophyte and punctatisporites pteridophyte monosaccate pollen coniferales cordaitales is frequently present pteridosperms mostly represented by cyclogranisporites are especially abundant in one level together with scarce striate bisaccate pollen grains assemblage 2 of the sauces formation is dominated by trilete spores related to the pteridophyta e g horriditriletes converrucosisporites granulatisporites and sphenophyta monosaccate cordaitales coniferales and taeniate and non taeniate bisaccate pollen grains pteridospermales coniferales are equally subordinated monosulcate pollen cycadophyta and fungi portalites gondwanensis are rare assemblage 1 is mainly moscovian assemblage 2 asselian sakmarian this interpretation is based on correlation of assemblage 1 to the dmb mid pennsylvanian and assemblage 2 to the fs early cisuralian biozones of the paganzo basin argentina the taxonomic composition of the ahrensisporites cristatus crucisaccites monoletus mid late pennsylvanian and the protohaploxypinus goraiensis subzone asselian sakmarian of the vittatina costabilis early cisuralian biozones of the parana basin brazil support this correlation the continental freshwater depositional setting of this part of the paganzo basin is supported by the dominance of terrestrial palynomorphs and phytoclasts the presence of coal and carbonaceous shales and the occurrence of plant megafossils and plant debris in the sediments the floristic changes between assemblages 1 and 2 are consistent with the interpretation of climatic amelioration associated with paleogeographic changes in gondwana occurring during the pennsylvanian and cisuralian

abnormal pollen grains an outcome of deteriorating atmospheric conditions around the permian triassic boundary records of abnormal gymnosperm pollen morphotypes from coeval localities in russia and nw china provide independent and unique evidence of deteriorating atmospheric conditions at the close of the permian although at similar palaeolatitude the vologda region of european russia and the junggar basin of xinjiang province china were thousands of kilometres apart and on different tectonic plates the co occurrence of the megaspore otynisporites eotriassicus fuglewicz 1977 and its restricted distribution elsewhere in marine sections with either late permian ammonoids or the basal triassic conodont marker hindeodus parvus confirms the age range and correlation of the russian and nw chinese sections in three chinese sections rapid changes in carbon isotopic 13 c org composition of between 4 and 10 occur over the intervals showing abnormal pollen these patterns reflect bioclastic facies contributions responding to local environmental changes they are nevertheless coincident with global perturbations in the atmosphere caused by extensive volcanic activity around the permian triassic boundary

whole rock and nd isotopic geochemistry of neoarchaean granitoids and their bearing on the evolution of the central hearne supracrustal belt western churchill province canada abstract the central hearne supracrustal belt chsb hearne domain western churchill province forms a large ca 30 000 km2 greenschist grade neoarchaean 2711 2660 ma terrane of predominant metavolcanic and less common metasedimentary rocks intruded by three groups of plutonic rocks pre tectonic group 1 plutons 2690 ma include rare gabbro dominant diorite to tonalite and rare granodiorite and granite these intrude and incorporate angular inclusions of cogenetic volcanic rocks and have variably developed foliations syn tectonic group 2 plutons 2690 2679 ma comprise rare gabbro and diorite predominant tonalite and granodiorite and rare granite and exhibit n s trending ductiley deformed supracrustal schlieren rich intrusive margins post tectonic group 3 plutons are rare and comprise either potassic biotite monzogranite or alkalic nepheline syenite and rare carbonatite abundant tonalite to granodiorite biotite hornblende bearing mineralogies and metaluminous and generally low medium k2o compositions indicate that most rocks are i or m type granitoids molecular na ca k variations and afm indices indicate transitional calc alkaline trondjhemitic trends with both tholeitic and calc alkaline affinities rare earth and incompatible element variations suggest that most granitoids exhibit volcanic arc or tonalite trondhjemite granodiorite ttg like abundances with multi element patterns varying gradationally from la poor lan ybn 12 nd isotopic values overlap with contemporaneous depleted mantle indicating that the granitoids represent melts derived from predominantly juvenile mantle or crust la poor rocks likely formed through low p anatexis of amphibolitic crust with plagioclase amphibole clinopyroxene present whereas high la rocks were generated via high p partial melting of a garnet clinopyroxene bearing protolith plausibly a subducted slab granitoid evolution from early dominant low p tholeiitic and calc alkaline melts to later predominant high p high al2o3 ttg melts reflects a change in the tectonomagmatic setting at ca 2690 ma construction of proto arc crust from ca 2711 2690 ma and extension of the leading edge of normal ca 40 km archaean oceanic crust in response to lithospheric processes analogous to those of the eocene sw pacific ocean resulted in asthenospheric upwelling intrusion of mantle derived melts into the lower crust and their subsequent ascent and fractionation partial melting at the base of the extended thick oceanic crust likely yielded sparse high la melts at this time at ca 2690 ma a change from an extensional to a shortening regime resulted in initiation of subduction of adjacent oceanic lithosphere partial melting of the eclogitic downgoing slab and generation of voluminous high p la rich granitoid magmas this yielded less abundant low p la poor melts emplaced into the infant arc crust during and following tectonism the complete sequence was intruded by late potassic granites derived from tonalitic lower crust and alkalic magmas that originated in the lithospheric mantle

an upper paleozoic bio chronostratigraphic scheme for the western margin of gondwana abstract the carboniferous and permian fossiliferous sequences of the central western argentina contain abundant plant remains palynomorphs and invertebrates they include a continuous record of large distribution in the paganzo rio blanco calingasta uspallata and san rafael basins the most recent biostratigraphic schemes recognize a floristic succession represented by the biozones archaeosigillaria frenguellia af biozone frenguellia eximia nothorhacopteris kellaybelenensis cordaicarpus cesarii fnc biozone nothorhacopteris botrychiopsis ginkgophyllum nbg biozone interval biozone and gangamopteris biozone the associated palynological record is represented by the biozones reticulatisporites magnidictyus verrucosisporites quasigobbetti mq biozone raistrickia densa convolutispora muriornata dm biozone pakhapites fusus vittatina subsaccata fs biozone and lueckisporites weylandites lw biozone the precise age of the upper paleozoic western gondwanan biozones has been under discussion and remains controversial to date in some regions the main issue hampering an integrated comparison of the gondwanan biozones was its imprecise chronostratigraphic framework however new studies in some argentinian stratigraphic sections bearing floras and faunas have yielded several radiometric ages from these 206 pb 238 u zircon datings it is possible to determine the chronostratigraphic range of many fossiliferous assemblages in this sector of gondwana in this way the af and mq biozones are restricted to the late mississippian and they would be not younger than 335 ma according to radiometric ages 206 pb 238 u ages suggest that the nbg dma and dmb biozones characterize the late serpukhovian glacial deposits and persisted up to the late bashkirian beds containing the interval and dmc biozones have yielded 206 pb 238 u ages of 312 82 0 11 ma and 310 71 0 1 ma which would indicate that both zones characterize the moscovian the remains of gangamopteris biozone found in the paganzo basin overlie basalt levels ranging between 308 6 and 293 6 ma therefore the incoming of the first glossopterids was closely associated to the carboniferous permian boundary in this part of gondwana the data presented in this paper are used for establishing comparisons with other gondwanan biozones constrained by absolute ages

temporal evolution of the neoarchean central hearne supracrustal belt rapid generation of juvenile crust in a suprasubduction zone setting abstract new u pb zircon ages are reported for 17 volcanic plutonic and sedimentary rocks from the neoarchean central hearne supracrustal belt in the western churchill province of the canadian shield the central hearne supracrustal belt historically referred to as the rankin ennadai greenstone belt is a major granite greenstone terrain with a strike length of over 700 km this study focused on the central and eastern segments of the belt in the kaminak lake area represents the first detailed chronological study of this extensive greenstone belt the geochronological data indicate rapid formation of crust between 2711 and 2667 ma rocks of the oldest assemblage i formed between 2711 and 2691 ma and consist of mixed tholeiitic and calc alkaline mafic and felsic submarine to subaerial volcanic rocks minor plutonic rocks group 1 are associated with this interval a younger assemblage ii of volcanic rock with significant calc alkaline plutonic rocks group 2 developed between 2686 and 2679 ma a period of deformation d1 locally separates the two assemblages major regional penetrative deformation and metamorphism developed during the latter stages of the plutonic event at ca 2680 ma an extensive belt of metasedimentary rocks and associated iron formation was deposited after 2681 ma based on ages of detrital zircon the youngest events include intrusion of 2666 4 1 1 ma post deformational granite group 3 2659 ma carbonatite can j earth sci 29 1992 896 and deposition of post 2660 ma conglomerates and arenites of possible timiskiming type there is no indication of contributions from mesoarchean crust either in inherited grains in igneous rocks or as detrital grains in sedimentary rocks although the evolutionary sequence has parallels to greenstone belts such as the abitibi belt in terms of the rock types and relative timing of events there are some differences we envision development of the belt in an extensional oceanic suprasubduction environment

a new u pb zircon age dating and palynological data from a lower permian section of the southernmost parana basin brazil biochronostratigraphical and geochronological implications for gondwanan correlations abstract index species useful for correlations with the international stratigraphical column are rare or absent in the pennsylvanian permian strata of the parana basin in brazil preventing accuracy in geochronologic assignments besides absolute datings are very scarce in comparison with other gondwana basins this paper presents palynological data from an outcrop on the surroundings of the candiota coal mine southmost brazil from several levels of the rio bonito and palermo formations the presence of certain index species of spore pollen allowed the recognition of two permian palynozones the vittatina costabilis and the lueckisporites virkkiae zones furthermore u pb in zircons from a volcaniclastic level interbedded in the coal strata of the former unit was analyzed through la mc icp ms method providing a new absolute age dating of 281 4 3 4 ma cisuralian early permian this dating is assumed as the oldest occurrence of the l virkkiae zone in parana basin which contains index species that are widespread in other gondwana basins a well distributed surface boundary occurs in this section also allowing local and regional correlations these new biostratigraphical and geochronological data are integrated in order to offer a deep analysis on the stratigraphical significance for correlations across the occidental gondwana

high precision temporal calibration of late permian vertebrate biostratigraphy u pb zircon constraints from the karoo supergroup south africa therapsid and other tetrapod fossils from the south african karoo supergroup provide the most detailed and best studied terrestrial vertebrate record of the middle and late permian the resulting biostratigraphic scheme has global applicability establishing a temporal framework for these faunas has proven difficult magnetostratigraphy has been hampered by a jurassic overprint and intercorrelation with permian marine sequences has been equivocal here we report u pb zircon isotope dilution thermal ionization mass spectrometry id tims dates for five volcanic ashes interbedded with fossils from the pristerognathus tropidostoma and cistecephalus vertebrate biozones of the beaufort group this temporal framework allows correlation to marine zonations and improves understanding of rates of faunal evolution and patterns of basin evolution our results identify no correlative vertebrate extinctions in the karoo supergroup to the marine end guadalupian mass extinction and raise the question of whether there is any record of a terrestrial extinction related to the emeishan large igneous province

back arcs basins and p wave crustal velocity in the ionian and aegean regions tomographic images of the lower crust and uppermost mantle beneath the central mediterranean have been obtained from arrival times of regional earthquakes we find a low velocity belt at about 25 km beneath the hellenic arc a low velocity anomaly at a depth of 40 km extends under the aegean back arc basin high velocities are present at moho depth beneath the ionian sea close to the calabrian and aegean arcs and under the aegean sea the results suggest a close relation between p wave crustal velocity and the subduction systems of the studied area

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

permian phytogeography in gondwana abstract phytogeographic patterns based on multivariate techniques multidimensional scaling are proposed for the permian vegetation of gondwana this approach requires a data set with broad geographic coverage based on generic composition and with good time control in general strong phytogeographic differentiation can be observed throughout the permian in order to identify short term phytogeographic patterns the permian period was informally divided into five time slices in the permian stage i earliest permian the vegetation was strongly influenced by glacial conditions a very impoverished vegetation is seen except in patagonia and parts of south america four units were identified patagonia nothosouthamerica australia and indo africa by far patagonia was the most diverse and had the most favourable climatic conditions perhaps as a result of palaeogeographic separation from western gondwana nothosouthamerica which included plant assemblages from nw argentina and brazil perhaps as two subunits is a mid latitude area with glacial influence in the brazilian sector indo africa had a much lower diversity occupying high latitudes whereas australia had the lowest diversity of all the vegetational regions in stage i the early permian stage ii shows a more diversified and expanded plant cover vegetation of eastern and western gondwana was differentiated patagonia and south america including a brazilian and nw argentinean unit had the richest plant assemblages whereas africa indo australia and antarctica as separate units are less diverse probably due to late glacial influence by the late early permian stage iii gondwana shows much more ameliorated climatic conditions basically due to drifting into more temperate latitudes as well as increased moisture resulting in expansion of peat forming areas this is immediately reflected in the vegetation as shown by diversified plant assemblages even in antarctica nonetheless a differentiation is again observed between eastern gondwana patagonian and south american units and the western sector indo australian and antarctic units whereas africa would probably represent an ecotone beginning in the late permian stage iv there was a decrease in the number of plant assemblages and diversity indicating a deterioration in climate resulting from generally drier conditions latitudinal differentiation can be observed with antarctica as a polar unit afro australia at high latitudes whereas the south american indian and patagonian units are located in middle latitudes finally in permian stage v latest permian a south american unit can be differentiated clearly from the rest africa and indo australia antarctica is interpreted again as a discrete unit in the stage v time slice eastern gondwana returns to more humid climatic conditions allowing the formation of extended peat swamps whereas the western sector is affected by seasonal and strong droughtness this kind of phytogeographic approach has proven useful for detecting some palaeogeographic problems such as those involving the patagonian subcontinent in this regard palaeogeographic reconstructions and palaeoclimatic models should be tested against these phytogeographic patterns

holocene record of slip predictable earthquakes on the kenchreai fault gulf of corinth greece abstract we present the quaternary slip history of the kenchreai fault gulf of corinth based on geomorphological palaeoseismological geo archaeological data and literally determined events we also applied a series of geomorphic indices such as the hypsometric curve asymmetry factor the stream length gradient index sl the valley floor width to valley height ratio vf the drainage basin shape bs and the mountain front sinuosity smf in drainage basins flowing perpendicular to the fault these indices are representative for longer time period and are analyzed as follows values of sl are relatively high close to the fault trace smf values range from 1 01 to 1 85 vf mean values range between 0 29 and 1 07 bs values range from 1 16 to 4 78 lateral fault growth was likely achieved by propagation primarily towards east while its western end appears to act as persistent barrier the holocene palaeoseismic history of the fault investigated by a palaeoseismological trench and 14 c dating of ten samples suggest four linear morphogenic earthquakes in the last 10 ka the kenchreai fault displays a holocene slip rate in the order of 0 15 mm a 1 and a recurrence interval ranging between 1300 and 4700 years thus the fault is classified as a fault of moderate activity with moderate to well developed geomorphic evidence of activity and an overall slip predictable earthquake model

the age and pb loss behaviour of zircons from the isua supracrustal belt as determined by ion microprobe ion microprobe uthpb analyses of zircons from a conglomeratic metavolcanic unit in the isua supracrustal belt of west greenland show that their magmatic age is3807 1ma and failed to detect any older zircon cores or xenocrysts low u areas within zircons at a 30 m scale lost only small amounts of radiogenic pb and only in the recent past whereas high u areas within grains lost much greater proportions of their pb both recently and as early as the archaean some areas in the zircons have concordant upb and thpb ages the ion probe results agree with earlier determinations for the isua supracrustals and clarify minor discrepancies between previous multigrain and single crystal analyses

tomography of the crust and upper mantle in southeast europe compressional velocity structure of the crust and the upper mantle in southeastern europe broader aegean area is studied by inverting residuals of the first p arrivals from earthquakes in this region 16 e 31 e 34 n 43 n the data used are from regional events recorded by the permanent network of stations during the period 1971 1987 enriched with data from experiments with portable seismographs in four regions of this broad area this study confirms the strong variations of crustal thickness in this area as well as the subduction of the eastern mediterranean lithosphere under the southern aegean and gives further detailed information on the crustal and upper mantle structure of the area important new information is the existence of a low velocity crustal layer in western greece and albania and that the velocity anomaly in the mantle under the southern aegean extends much farther and deeper to the northeast than the benioff zone of the intermediate depth earthquakes indicates furthermore evidence is presented about the possible existence of older subduction in the northern aegean and about the influence of the tectonic regime on the velocity field

3820 ma zircons from a tonalitic armisoq gneiss in the godthab district of southern west greenland abstract zircons from a sample of the tonalitic amitsoq gneisses near godthhb west greenland exhibit several stages of crystal growth measurements of the u th pb isotopic composition of 30 m areas within individual grains using the ion microprobe shrimp reveal that components of magmatic zircon from the original igneous protolith are at least 3822 5 ma l old slightly but significantly older than the age of zircons from a fclsic volcanic unit in the isua supracrustal belt as measured at high precision by the same technique and older than all ages previously determined by mineral and whole rock isotopic techniques for amitsoq gneisses at godthab and at isukasia overgrowths of younger zircon formed at ca 3630 ma coinciding with an episode of major pb loss from the older grains these results indicate that previous whole rock isochron ages refer to later isotopic redistribution and or that other phases of the amitsoq gneisses intruded during this later period and dominate the isotopic systematics comparison of the ion probe results with previous conventional u th pb data for the same zircon sample demonstrates the strong influence of discordant high uranium parts of zircon on the mean isotopic composition of multi grain samples

geology and age of the late archean keivy alkaline province northeastern baltic shield abstract the keivy alkaline province kola peninsula consists of six peralkaline granite bodies alkaline syenogranite dikes and two nepheline syenite intrusions emplaced between the tonalite trondhjemite granodiorite basement and the supracrustal keivy terrane u pb zircon ages for the keivy alkaline province range from 2613 to 2682 ma and for the spatially associated gabbro anorthosite complexes from 2659 to 2668 ma the keivy alkaline granitoids are geochemically different from other late archean alkaline rocks inferred to have been emplaced in subduction zone settings the keivy alkaline province may represent the earliest example of magmatism associated with continental rifting and the involvement of a mantle plume with oceanic island basalt like characteristics

stratigraphy sedimentology and physical volcanology of the henik group central ennadai rankin greenstone belt northwest territories canada late archean paleogeography of the hearne province and tectonic implications abstract extensive areas of the hearne and rae provinces are underlain by archean metavolcanic and metasedimentary rocks in the rae province supracrustal sequences with prominent continental to shallow water quartz arenites have been interpreted by others as rift and passive margin deposits in the hearne province to the southeast the ennadai rankin greenstone belt is exposed in an area ca 700 200 km forming the second largest greenstone belt in canada it comprises mainly greenschist facies grade mafic and felsic volcanic siliciclastic chemogenic and volcaniclastic rocks stratigraphic sedimentologic and physical volcanologic data based on 1 50 000 scale mapping in the central part of the belt indicate deposition in a subaqueous mafic volcanic plateau slope basin system that was well removed from a continental influence water depth was below storm wave base as indicated by preservation of delicate lamination in pelitic and iron formation units absence of features suggestive of subaerial exposure oscillatory flow or tidal currents and lack of interfingering rocks that could represent laterally adjacent shelf coastal or continental environments reconnaissance level regional geologic and geochronologic data indicate an overall pattern of supracrustal deposition in the hearne province consisting of a large mafic volcanic plain isolated felsic volcanic centres with lenses and belts of deep water sedimentary rocks at least two speculative yet testable tectonic models are consistent with the inferred paleogeography for both the rae province is considered to be the western continental hinterland to the ensimatic hearne province the rae and hearne provinces may record late archean continental extension sea floor spreading oceanic volcanic arc growth diachronous back arc spreading and collapse and arc continent collision with thrusting of oceanic rocks on to attenuated rae crust alternatively the hearne province may represent northwestward accretion of multiple volcanic arc trench pairs

evidence for late palaeozoic glaciation in southern tanzania abstract new observations from basal karoo beds of the ruhuhu basin in southern tanzania prove the existence of the late palaeozoic glaciation in the region bordering lake nyasa evidence for the glaciation includes the identification of tillites and varved lacustrine siltstones with dropstones the tillites contain abundant striated and facetted pebbles and cobbles floating in a rock flour matrix consisting of finely ground quartz and feldspar features supporting subglacial transport of the rudaceous sediments are microstriations on clasts pressure flaked edges of grains and cleavage breakage observed under the sem the topography of the pre karoo surface suggests continental glaciation the onset of the glaciation was concomitant with late carboniferous to early permian taphrogenic movements which established the large ne trending karoo trough of tanzania

observations of shear wave splitting parameters in the western gulf of corinth focusing on the 2014 mw 5 0 earthquake abstract the western gulf of corinth located in central greece is an active neotectonic graben that features intense seismicity events recorded by dense local networks during 2014 including those belonging to an offshore swarm between nafpaktos and psathopyrgos were used to perform a shear wave splitting study with recordings that fulfill strict criteria the splitting parameters determined by visually inspecting polarigrams and hodograms are the polarization direction of the fast shear wave and the time delay between the two split shear waves over 960 observations were obtained for 13 stations in the area temporal variations of normalized time delays were investigated to extract patterns that indicate stress accumulation and release such patterns were identified in 5 stations where linear trends of increase followed by a decrease a couple of weeks before the mw 5 0 7th november 2014 earthquake were identified these observations highlight similarities with behavior of time delays before the occurrence of earthquakes in other areas nevertheless scattering of measurements poses a significant challenge in interpreting these variations the mean polarization direction of the fast shear wave in each station is consistent with the known regional maximum horizontal stress component i e wnw ese except for three stations located in the northern shore of the gulf which present a general ne sw polarization direction the former is interpreted with the anisotropic poro elasticity model where fluids within microcracks aligned with the regional stress regime affect shear wave splitting the latter are located in an area where faults of similar direction have been mapped which could indicate the presence of secondary local stress states

vegetation history across the permian triassic boundary in pakistan amb section salt range hypotheses about the permian triassic floral turnover range from a catastrophic extinction of terrestrial plant communities to a gradual change in floral composition punctuated by intervals indicating dramatic changes in the plant communities the shallow marine permian triassic succession in the amb valley salt range pakistan yields palynological suites together with well preserved cuticle fragments in a stratigraphically well constrained succession across the permian triassic boundary palynology and cuticle analysis indicate a mixed glossopteris dicroidium flora in the late permian for the first time dicroidium cuticles are documented from age constrained upper permian deposits on the indian subcontinent close to the permian triassic boundary several sporomorph taxa disappear however more than half of these taxa reappear in the overlying smithian to spathian succession the major floral change occurs towards the dienerian from the permian triassic boundary up to the middle dienerian a gradual increase of lycopod spore abundance and a decrease in pteridosperms and conifers are evident synchronously the generic richness of sporomorphs decreases the middle dienerian assemblages resemble the previously described spore spikes observed at the end permian norway and in the middle smithian pakistan and might reflect a similar ecological crisis

on the resolving power of tomographic images in the aegean area b the imaging of upper mantle heterogeneity by seismic tomography is strongly limited by the uneven global distribution both of seismic recording stations and earthquake sources this can result in a loss of resolution and significance in the final image particularly when a sparse data set contains few ray paths which intersect at sufficiently high angles in the volume of interest in order to investigate the theoretical resolving power of a previously published tomographic image of the aegean area synthetic tests of the inversion procedure using a ray path matrix obtained in this previous study for local and teleseismic p waves were carried out the aim was to examine the extent to which the shape of a synthetic lithospheric slab penetrating to different depths is inherently distorted by the tomographic imaging procedure and to compare the synthetic tomographic images with the results from the actual inversion the distortion is found to take the form of an artificial stretching of the lithospheric slab the maximum stretching factor as indicated by the downdip displacement of the peak amplitude of the synthetic high velocity anomaly is found to be a factor of 2 or so though the distortion is usually less than this the peak amplitude of the tomographic image of a lithospheric slab is found from the inversion of traveltime data to be at depths at or below 400 km this indicates that the high velocity lithospheric slab in the aegean penetrates deeper than the benioff zone seismicity of about 200 km however no constraints of the maximum depth of penetration could be established with the data set used in the present work

continental tholeiitic mafic rocks of the paleoproterozoic hurwitz group central hearne sub domain nunavut insight into the evolution of the hearne sub continental lithosphere the paleoproterozoic hurwitz group of the western churchill province is an erosional remnant of an areally extensive predominantly shallow water intracratonic basin comprised of four major sequences sequence 2 forming the central part of the stratigraphy contains the ameto formation a sequence of pillowed and massive basaltic rocks and associated gabbro sills termed the happotiyik member that are interlayered with subordinate deep water mudstones siltstones and diamictites whole rock geochemical data for the mafic rocks reveals a suite of homogeneous tholeiitic basalts with affinities to both continental and volcanic arc tholeiites compatible trace elements and large ion lithophile elements exhibit scattered behavior whereas all high field strength elements show a systematic increase with zr the rocks are large ion lithophile and light rare earth element enriched and have parallel primitive mantle normalized extended trace element patterns with prominent negative nb ta and ti anomalies end

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

historical coastal evolution of the ancient harbor of aegina in relation to the upper holocene relative sea level changes in the saronic gulf greece abstract the extensive ancient harbor installations today submerged on the seafront of kolona in aegina are associated with the great trading and maritime development of the island from the middle bronze age to the middle classical period based on geomorphological and archeological indications three distinct relative sea levels can be defined at depths of 3 17 0 05 m 0 97 0 05 m and 0 52 0 05 m the dating of the sea level changes based on archeological evidence and historical sources shows that the initial sea level change in aegina occurred certainly after ad 170 and most likely after ad 250 the intermediate change is dated between ad 1586 and ad 1839 and the most recent change occurred between 1839 and 1999 a transgression followed a long period of sea level stability that lasted at least 2200 years from the middle bronze age ca 3900 yr bp to the late roman period ca 1700 yr bp according to the paleogeographical reconstruction of the coast the ancient harbor installations stretch along 1600 m of coastline the north harbor is bounded by the north breakwater the riprap on the once wide sandy coast the detached west breakwater and the uplift morphology of the west end of kolona hill on the south coast the harbor installations comprise the fortified closed harbor with the shipsheds the commercial harbor which is entirely destroyed by the modern port the anchorage area that is bounded by the west breakwater and built of cone shaped piles of stones the tops of which once projected above the sea level and the south curved breakwater at its southernmost boundary

age and geological setting of the rankin inlet greenstone belt and its relationship to the gold endowment of the meliadine gold district nunavut canada abstract archean greenstone belts host a significant proportion of the world s gold typically in deposits that formed late during greenstone belt formation and cratonization however this is not always the case and in the multiply reworked western churchill province wcp orogenic lode gold deposition post dates greenstone belt formation by nearly one billion years the spatial link between proterozoic gold and archean greenstone belts in the wcp is thus particularly striking although its significance is still not fully understood the meliadine gold district 2 8 moz contained au in reserves plus an indicated and inferred resources of 5 8 moz au represents an important example of this deposit style and is hosted within the rankin inlet greenstone belt rigb which occupies a critical but controversial position along the largely inferred boundary between the hearne craton and the chesterfield block rigb felsic volcanic rocks ca 2 66 ga are structurally intercalated and broadly coeval with mafic volcanic and volcaniclastic rocks 2 66 2 64 ga turbidite 2 66 2 64 ga argillite auriferous banded iron formation successions and syn volcanic granodioritic to tonalitic intrusions 2 67 2 64 ga neoarchean basaltic to andesitic volcanic rocks possess calc alkaline to primitive arc like tholeiitic magmatic affinities along with lesser morb like basaltic compositions geochemically evolved lavas yield depleted 144nd 143nd ratios nd2 66 ga 1 1 to 1 6 that reflect variable interaction with an evolved and hitherto undocumented meso to neoarchean basement underlying the rigb whereas transitional arc like primitive tholeiitic and morb like basaltic samples overlap with the nd isotopic composition of depleted mantle at ca 2 66 ga nd2 66 ga 1 6 to 2 7 these neoarchean volcano sedimentary panels represent the main auriferous rock package within the meliadine gold district and are intercalated with deformed paleoproterozoic conglomerate 2 50 and 2 155 ga the latter are in turn unconformably overlain by a geochemically distinct pillowed basalt sequence and a unique carbonate siliciclastic package that presumably represent the remnants of paleoproterozoic basins and are not known to host gold the geological setting of gold deposits thus likely reflects this favourable neoarchean lithostratigraphy in addition to metamorphism and fluid focusing along the reactivated faults during the collision of the hearne and combined chesterfield block rae craton at 1 90 1 85 ga

permian triassic boundary in the central transantarctic mountains antarctica the permian triassic boundary occurs within a relatively complete terrestrial sequence in the shackleton glacier area of the central transantarctic mountains the boundary is within a 7 to 10 m thick interval between the permian glossopteris flora and the lower triassic lystrosaurus fauna this interval representing on the order of 200 k y records some of the events that occurred in the transition from the permian to triassic in the best documented section at graphite peak in the beardmore glacier region protohaploxypinus microcorpus zone palynomorphs which we assign to the latest permian record the declining glossopteris flora and occur near the top of the buckley coal measures just below a previously reported major negative 13c excursion in the shackleton glacier area the permian glossopteris flora including fossil wood roots and leaves occurs within the lower part of the fremouw formation the antarctic lystrosaurus assemblage of early triassic age has several species in common with the south african fauna that lived 20 to 35 closer to the equator the migration of vertebrates from southern africa into antarctica in the early triassic supports hypotheses of runaway greenhouse warming possibly related to co2 emissions from siberian flood basalts and large methane gas releases changes in flora bracketing the first of the major negative 13c anomalies near the boundary in antarctica and in east greenland support the hypothesis that a global event perhaps through mutations caused by enhanced ultraviolet radiation may have played a role in the destruction of floras

structural patterns and tectonic evolution of supracrustal domains in the archean slave province canada a new plate tectonic model accounts for lithological relations and regional structural patterns in late archean supracrustal domains of the slave province multiple dykes and pillowed mafic flows most common in the western part of the province suggest sea floor spreading the mafic volcanics lying in narrow homoclinal belts stratigraphically below more extensive turbidites are viewed as megaxenolithic remnants of oceanic crust preserved on the periphery of granitoid plutons and blocks of sialic crust closure of an oceanic basin was marked by emplacement of the granitoid plutons and coeval felsic volcanics the latter predominating over mafic volcanics in northeastern domains the felsic calc alkaline magmas may have risen from a shallow dipping subduction zone westerly verging folds westerly convex fold arcs and inclinations of later foliations particularly in lower level rocks of higher metamorphic grade are in accord with underthrusting to the east the zone of underthrusting shifted progressi

3 d velocity structure beneath the crust and upper mantle of aegean sea region the region of the aegean sea and the surrounding areas in the eastern mediterranean lies on the boundary zone between the eurasian and the african plates it is a zone of widespread extensive deformation and therefore reveals a high level of seismicity

unsupported radiogenic pb in zircon a cause of anomalously high pb pb u pb and th pb ages ion microprobe u th pb isotopic analyses of zircons from a granodioritic orthogneiss from the napier complex mount sones enderby land antarctica have identified an unambiguous example of unsupported radiogenic pb in a 3 950 ma old crystal at one 40 m spot on the crystal an unusually large heterogeneity in pb content was found the concentration of radiogenic pb ranging from 5 to 50 percent higher than could have been generated in 3 950 ma by radioactive decay of the co existing u and th this relative excess of radiogenic pb is attributed to pb gain rather than to u and th loss because first the pb content varied by more than the u or th contents and secondly changes in the pb u pb th and pb isotopic composition correlated directly with changes in the pb concentration the individual 207pb 206pb apparent ages ranged from 4 000 ma to 4 145 ma all greater than the inferred age of the crystal a correlation between 207pb 206pb and pb u shows that the pb excess has not resulted from recent pb movement the spot apparently gained radiogenic pb about 2 500 ma ago at the same time as the majority of the other zircons in the rock suffered substantial pb loss the pb movement occurred in response to a discrete geologic event reverse discordance is a phenomenon that must be considered when interpreting zircon u pb ages especially 207pb 206pb ages of single crystals or portions of crystals

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

resolving the age of madumabisa fossil vertebrates palynological evidence from the mid zambezi basin of zambia age estimates for permian rocks in the mid zambezi basin of zambia have thus far yielded ambiguous results previously studied palynoassemblages from the madumabisa formation resemble spore pollen suites from both the cistecephalus zone of north luangwa lopingian and the palynological assemblage sub zone iv h of zimbabwe proposed as guadalupian in order to improve age estimates and refine the biostratigraphy of the madumabisa formation this formation together with the underlying gwembe formation were sampled for palynomorphs assemblages from the gwembe formation are dominated by trilete spores with less common striate and non striate bisaccate pollen whereas the overlying madumabisa formation palaeoflora is composed predominantly of striate bisaccates ferns pteridosperms lycopods sphenophytes glossopterids and conifers are represented in the palynofloras the upper gwembe formation palynoassemblage can be correlated with the didecitriletes ericianus zone of backhouse 1991 the guttulapollenites hannonicus protohaploxypinus rugatus zone zone vi of aitken 1998 assemblage zone iii of the mid zambezi basin zimbabwe and biozone kk 3 in the kalahari karoo basin botswana suggesting a guadalupian wordian capitanian age the upper madumabisa formation palynoassemblage can be placed in the upper dulhuntyispora parvithola zone of backhouse 1991 app5 of price 1997 dated as wuchiapingian lopingian and correlates with assemblage 2 of the moatize minjova basin mozambique and the mckinnon member palynofloras of east antarctica it also resembles daptocephalus formerly dicynodon assemblage zone palynofloras of the lower and middle balfour formation in the karoo basin south africa and is suggested to be lopingian wuchiapingian changhsingian in age although these palynological assemblages place lower and upper age constraints on madumabisa formation vertebrate fossils uncertainty remains as to the exact correlation between the madumabisa vertebrate assemblages and the assemblage zones of the main karoo basin