fluvial response to paleo equatorial climate fluctuations during the late paleozoic ice age the maritimes basin of atlantic canada preserves a 12 km thick stratigraphic succession deposited within a low latitude predominantly continental setting during the late paleozoic this paper examines the utility of using such successions for paleoclimate analysis with specific reference to changes in fluvial style modern rivers in the subhumid and semiarid tropics preserve a suite of features that are distinct from those in humid and arid environments these features include an abundance of sedimentary structures formed under froude transcritical to supercritical flow conditions and the presence of in situ vegetation growing within the channel environment this fluvial style is indicative of prolonged low flow conditions punctuated by intense precipitation events in a strongly seasonal climatic setting fluvial channel bodies within the maritimes basin preserve a remarkably similar style compared with these modern systems suggesting that a subhumid strongly seasonal paleoclimate was the dominant imprint on parts of the preserved successions strongly seasonal deposits are concentrated within four discrete stratigraphic intervals e1 e4 ranging in duration from 2 to 6 m y these intervals are correlated across the entire basin and between basins characterized by markedly different tectonic regimes which suggests that a coherent regional climate signal is recorded intervals are separated by deposits characteristic of humid and arid river systems and the alternation between these different fluvial styles implies that several pronounced long term changes in precipitation and runoff regimes occurred during the carboniferous within the region furthermore these intervals broadly coincide with major periods of southern hemisphere glaciation which suggests that glaciation had a profound and controlling effect on paleotropical climate

climate warming in the latest permian and the permian triassic mass extinction high resolution oxygen isotope records document the timing and magnitude of global warming across the permian triassic p tr boundary oxygen isotope ratios measured on phosphate bound oxygen in conodont apatite from the meishan and shangsi sections south china decrease by 2 in the latest permian translating into low latitude surface water warming of 8 c the oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates suggesting that the addition of isotopically light carbon to the ocean atmosphere system by siberian traps volcanism and related processes resulted in higher greenhouse gas levels and global warming the major temperature rise started immediately before the main extinction phase with maximum and harmful temperatures documented in the latest permian meishan bed 27 the coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems in addition very warm climate conditions in the early triassic may have played a major role in the delayed recovery in the aftermath of the permian triassic crisis

earthquake swarms precursory to moderate to great earthquakes in the northeast india region abstract the northeast india region has seen ten m 7 1 2 earthquakes since 1897 including two great earthquakes of m 8 7 in 1897 and 1950 the last m 7 1 2 earthquake occurred on august 17 1952 with the exception of three earthquakes others are found to be associated with periods of background normal seismicity precursory swarms quiescence and mainshocks and the associated foreshocks and aftershocks the dataset has been critically examined for completeness considering the current capabilities for defining locations and also considering other parameters regression equations relating the mainshock magnitude mm the average magnitude of the largest two events in the swarm mp and the time interval mp between the beginning of the swarm and the mainshock have been developed these are mm 1 37mp 1 41 and mm 3log10tp 3 27 it is important to recognize precursory swarms and quiescence in real time indeed we believe we have recognized one such sequence in the vicinity of the arakan yoma fold belt on the basis of mp and tp values the lateral extent of swarm activity and the fact that no event of m 6 has occurred since 1975 in the preparation zone defined by the 1963 1965 swarm we estimate that an m 8 earthquake could occur at any time in the area bounded by 21 and 25 1 2 n and 93 and 96 e the focal depth of this impending earthquake is estimated to be 100 40 km in view of the focal depths of the other events in the swarm

a newly discovered earliest triassic chert at gaimao section guizhou southwestern china abstract the permian triassic ptb boundary section at gaimao huaxi district guiyang guizhou province records a unique lithological transition between the permian and triassic in south china thus bioclastic limestones of the changxing formation are overlain by radiolarian bearing siliceous rocks of the dalong formation and ultimately limestone mudstone alternations of the shabaowan formation conodont sampling of the section revealed well preserved elements that enabled a conodont biostratigraphy to be established the occurrences of hindeodus julfensis and hindeodus typicalis in changxing formation bioclastic limestone indicate a late permian age four conodont zones have been established in dalong and shabaowan formations in ascending order those are the isarcicella isarcica zone neogondolella or clarkina planata zone neogondolella krystyni zone and neospathodus dieneri zone the presence of typical griesbachian conodonts i isarcica and isarcicella staeschei in upper dalong formation indicates that this formation s radiolarian bearing siliceous mudrocks are of earliest triassic age and not restricted to the permian as previously thought thin section analysis reveals that the upper dalong formation contains spheroidal radiolarians but not a diverse assemblage of permian holdover taxa the new data proves that following the end permian mass extinction of radiolarian the abundance of these siliceous planktons was maintained at least locally enabling chert deposition to persist thus the gaimao section provides an exception to the early triassic chert gap the first of its kind in palaeo tethys and indicates that the end of chert deposition does not always mark the end permian mass extinction

a probabilistic assessment of earthquake hazard parameters in nw himalaya and the adjoining regions the maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of nw himalaya and the adjoining regions for this purpose we have prepared a reliable homogeneous and complete earthquake catalogue during the period 1500 2010 the technique used here allows the data to contain either historical or instrumental era or even a combination of the both in this study the earthquake hazard parameters which include maximum regional magnitude mmax mean seismic activity rate the parameter b or b log e of gutenberg richter g r frequency magnitude relationship the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900 2010 the uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters the earthquake hazard in the whole nw himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level tectonics and focal mechanism the annual probability of exceedance of earthquake activity rate of certain magnitude is also calculated for all seismogenic source zones the obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters it is observed that seismic hazard level is high in quetta kirthar sulaiman region in pakistan hindukush pamir himalaya region and uttarkashi chamoli region in himalayan frontal thrust belt the source zones that are expected to have maximum regional magnitude mmax of more than 8 0 are quetta southern pamir caucasus and kashmir himanchal pradesh which have experienced such magnitude of earthquakes in the past it is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity

the buday ah formation sultanate of oman a middle permian to early triassic oceanic record of the neotethys and the late induan microsphere bloom abstract the middle permian to lower triassic buday ah section exposed in the oman mountains is the first deep sea section to be described in the neotethys the oceanic sediments were deposited along the southern tethys margin in the newly formed hawasina basin it is one of the few places where true tethyan permian radiolarites are exposed that allow the documentation of ccd evolution through time the succession begins as oceanic crust pillow basalt with red ammonoid rich pelagic limestone occurring both above and within inter pillow cavities the new occurrence of clarkina postbitteri hongshuiensis indicates a late capitanian age for the carbonate the sharp change to overlying late capitanian to changhsingian radiolarite reflects rapid subsidence about 10 myrs after initial continental breakup that resulted in the formation of the neotethys ocean new conodonts indicate that the permian triassic boundary succession occurs in the first platy lime mudstone beds above a changhsingian siliceous to calcareous shale unit the platy lime mudstone beds include an upper griesbachian bloom of calcite filled spheres radiolarians that marks a potential world wide event new conodonts indicate an early olenekian age for overlying grey papery limestone that are devoid of both macrofossils and trace fossils indicating that recovery from the late permian extinction has not yet progressed within this deep water environment 13 c org isotope values have not been disturbed and they show a negative shift just below the permian triassic transition and a second one at the parvus zone level above the buday ah succession may represent the most distal and probably deepest permian and lower triassic depositional sequence within the basin

development of the palaeogeography of pangaea from late carboniferous to early permian abstract old and new well and poorly known lithofacies data of moscovian and artinskian age in the area limited by the arctic sea and central africa the atlantic ocean and the ural mountains have been plotted on present day maps the facies mapped and related environments allow the recognition of a series of different palaeogeographic palaeotectonic units including the late carboniferous to early permian deep sea to palaeo tethyan ocean west siberia kazakhstan continent and uralian kazakhstan tienshan arc uralian foredeep up to the closing arms of the uralian ocean precaspian basin russian platform donets rift basin caucasian moesian dobrogean polish oslo basinal belt syn tectonic hercynian foreland basin intramontane post hercynian basins iran anatolian hellenic dinaric carnic basin branching into the hungarian seaway apennine basin branching into the cantabrian and south portuguese basins oman iraq levantine sicily deep basin and inferred oceanic sea way south peri tethyan platform basins east arabian cratonic basin and north african intracratonic basins the subsidence sedimentation trends of these units were correlated and compared through lithostratigraphic logs bathymetric curves and uncorrected cumulative stratigraphic curves the sets of original and processed data were used to test two different palaeodynamic models a pangaea a model static from late carboniferous to triassic and a mobile pangaea b model with different dextral displacements between laurussia and gondwanaland in the same time interval the best fit for our data requires a strike slip offset of about 800 km from moscovian to artinskian time this model implies a first quasi pangaea or pangaea b assembly at the carboniferous permian transition an ephemeral pangaea b break up driven by an early permian oblique rift across the mediterranean to caribbean areas and a final pangaea a assembly in the mid to late permian the two palinspastic maps describing the model have been cross checked by comparison with an independent set of biogeographic features of late carboniferous and early permian overall floral reptile and marine benthic organism distribution is consistent with the early permian trans pangaea seaway inferred from facies and palaeodynamic analyses

identification of the guadalupian lopingian boundary in the permian in a bedded chert sequence south china abstract middle upper permian conodont biostratigraphy was examined in a bedded chert section in dachongling area of southeastern guangxi zhuang autonomous region south china four conodont zones were recognized namely jinogondolella granti zone clarkina postbitteri hongshuiensis zone clarkina postbitteri postbitteri zone and clarkina dukouensis zone in ascending order the four conodont zones can be correlated with those recognized previously in bathyal carbonate and lime chert sequences on the basis of the correlation we identified the guadalupian lopingian g l geochronostratigraphic boundary i e the basal boundary of lopingian series in the permian six radiolarian zones were also recognized in the same section namely pseudoalbaillella longtanensis zone pseudoalbaillella globosa zone follicucullus monacanthus zone follicucullus scholasticus zone follicucullus charveti zone and albaillella levis zone in ascending order correlations between radiolarian zones and conodont zones are shown here the ecological evolutionary process of conodonts and radiolarians changed abruptly through the inferred g l geochronostratigraphic boundary besides these a geochemical anomalous zone with the higher ce ce values occurred underlying the g l geochronostratigraphic boundary and petrological diagnoses around the g l boundary changed the abrupt change of ecological evolution in coincidence with the geochemical anomalous zone and change of petrological diagnoses might show the pre lopingian catastrophic event of marine faunas the reason of the event of marine faunas may be that a regression occurred at the end of the guadalupian

paleophysiology and end permian mass extinction physiological research aimed at understanding current global change provides a basis for evaluating selective survivorship associated with permo triassic mass extinction comparative physiology links paleontological and paleoenvironmental observations supporting the hypothesis that an end permian trigger most likely siberian trap volcanism touched off a set of physically linked perturbations that acted synergistically to disrupt the metabolisms of latest permian organisms global warming anoxia and toxic sulfide probably all contributed to end permian mass mortality but hypercapnia physiological effects of elevated pco2 best accounts for the selective survival of marine invertebrates paleophysiological perspectives further suggest that persistent or recurring hypercapnia global warmth also played a principal role in delayed triassic recovery more generally physiology provides an important way of paleobiological knowing in the age of earth system science 2007 elsevier b v all rights reserved

testing periodicity of depositional cyclicity cisco group virgilian and wolfcampian texas abstract periodicities of 15 cyclic sections of the cisco group are tested through gamma and spectral analyses the sections are composed of marine and nonmarine carbonate and siliciclastic rocks deposited on the eastern shelf north central texas in late pennsylvanian and early permian time gamma analysis generates facies dependent thickness time conversion factors s to construct corrected time series which are more realistic than the uncorrected series obtained by proportional conversion positive and stable s and improved resolution of the corrected spectra indicate successful tuning on the cisco spectra a short eccentricity peak 95 131 ky is the most prominent and persistent long eccentricity 413 ky and obliquity 34 and 43 ky peaks are persistent and precessional index peaks 17 and 21 ky are less persistent a persistent peak of period 50 80 ky may be a combination tone between obliquity and precessional index cycles non milankovitch peaks are sporadic the validity of gamma and spectral results is indicated by consistent estimated ages among the cisco sections and reasonable effective sedimentation rates calculated on the basis of milankovitch spectral calibrations the results combined with geologic evidence suggest that the cisco cyclicity was controlled dominantly by milankovitch climatic forcing

contrasting microbial community changes during mass extinctions at the middle late permian and permian triassic boundaries abstract microbial communities are known to expand as a result of environmental deterioration during mass extinctions but differences in microbial community changes between extinction events and their underlying causes have received little study to date here we present a systematic investigation of microbial lipid biomarkers spanning 20 myr middle permian to early triassic at shangsi south china to contrast microbial changes associated with the guadalupian lopingian boundary glb and permian triassic boundary ptb mass extinctions high resolution analysis of the ptb crisis interval reveals a distinct succession of microbial communities based on secular variation in moretanes 2 methylhopanes aryl isoprenoids steranes n alkyl cyclohexanes and other biomarkers the first episode of the ptb mass extinction me1 was associated with increases in red algae and nitrogen fixing bacteria along with evidence for enhanced wildfires and elevated soil erosion whereas the second episode was associated with expansions of green sulfur bacteria nitrogen fixing bacteria and acritarchs coinciding with climatic hyperwarming ocean stratification and seawater acidification this pattern of microbial community change suggests that marine environmental deterioration was greater during the second extinction episode me2 the glb shows more limited changes in microbial community composition and more limited environmental deterioration than the ptb consistent with differences in species level extinction rates 71 vs 90 respectively microbial biomarker records have the potential to refine our understanding of the nature of these crises and to provide insights concerning possible outcomes of present day anthropogenic stresses on earth s ecosystems

permian radiolarian faunas from thailand and their paleogeographic significance abstract chert and fine grained clastic rocks in thailand contain rich permian radiolarian faunas we have discriminated eight radiolarian assemblages in these rocks pseudoalbaillella bulbosa upper carboniferous to lowermost permian gzhelian to asselian pseudoalbaillella simplex lowermost permian asselian pseudoalbaillella lomentaria lower permian asselian to sakmarian pseudoalbaillella scalprata lower permian sakmarian follicucullus monacanthus middle permian wordian follicucullus porrectus upper middle to lowermost upper permian capitanian to lower wuchiapingian neoalbaillella ornithoformis upper permian wuchiapingian and neoalbaillella optima upper permian changsingian assemblages in stratigraphic order these radiolarians have a potential to contribute to understanding the history of the paleotethys based on the radiolarian biostratigraphy and lithological characteristics lower to lower upper permian radiolarian bearing cherts are thought to have been deposited in a pelagic environment in a deep basin far from land the uppermost permian radiolarian bearing cherts however reveal differences in their depositional environments in northern thailand the uppermost permian to middle triassic radiolarian chert was deposited in a pelagic basin while in eastern thailand the uppermost permian chert and the conformably overlying clastic rocks show a change in depositional environment across the p t boundary from a deep pelagic or hemipelagic to shallow seas in the triassic

end permian mass extinction in the oceans an ancient analog for the twenty first century the greatest loss of biodiversity in the history of animal life occurred at the end of the permian period 252 million years ago this biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of earth s largest continental flood basalt provinces the siberian traps volatile release from basaltic magma and sedimentary strata during emplacement of the siberian traps can account for most end permian paleontological and geochemical observations climate change and perhaps destruction of the ozone layer can explain extinctions on land whereas changes in ocean oxygen levels co2 ph and temperature can account for extinction selectivity across marine animals these emerging insights from geology geochemistry and paleobiology suggest that the end permian extinction may serve as an important ancient analog for twenty first century oceans

a precis on pre alpine tectonic history of tethyan paleooceans abstract the history of the mediterranean belt saw the emergence evolution and disappearance of several successively existing oceans these were fairly large oceanic crust basins homologues of the present oceans throughout the phanerozoic they separated the northern eurasian from the southern gondwanan continents with geologically established paleomargins that resemble the present continental margins phanerozoic time was marked by the destruction of the southern gondwanan margin of the tethys and accretion of the northern eurasian continental margin the history of the present day eurasia was greatly influenced by the indosinian orogeny which is considered to be on a level with the caledonian hercynian and alpine orogenies

permian age from radiolarites of the hawasina nappes oman mountains the hawasina napper of the oman mountains yielded permian radiolarians from cherts stratigraphically overlying a thick volcanic basement al jil formation at the base of the hamrat duru group this fauna represents the first permian radiolarians and radiolarites in the central and western tethyan realm a permain age for pelagic sequences within the hawasina complex of oman has major significance for regional paleogeographic reconstruction a clear differentiation between platform reefal sediments and basin radiolarites from the base of the late permian 255 ma is implied it suggests a flexure of the platform during permian time the present data implies that a zone of rifting was already developed adjacent to the northeast gondwana platform margin during the late permian the hamrat duru basin corresponds to an opening intracontinental rift area sphenochasm between arabia and northeast gondwana a reentrant of the paleo tethys

the permo triassic extinction the end permian mass extinction brought the palaeozoic great experiment in marine life to a close during an interval of intense climatic tectonic and geochemical change improved knowledge of latest permian faunas coupled with recent advances in isotopic studies and biostratigraphy have greatly enhanced our understanding of the events of 250 million years ago and have begun to provide answers to many questions about the causes of extinction

structural and tectono stratigraphic review of the sicilian orogen and new insights from analogue modeling abstract the apennines sicilian maghrebian fold and thrust belt originated from the subduction of the alpine tethys and the later collision of drifted continental blocks against the african and apulian paleomargins from north to south the sicilian fold and thrust belt sftb is divided in four main tectono stratigraphic domains 1 the calabro peloritani terrane drifted from the european margin 2 the remnants of the alpine tethys accretionary wedge atw related to the subduction of the tethys 3 the folded and thrusted platform panormide and deep water imerese sicanian series of the offscrapped african margin and 4 the african foreland hyblean unfortunately scarce quality seismic lines and outcrops of key tectono stratigraphic units make the structure and dynamic evolution of the central eastern part of the sftb controversial first this study outlines through a review of the tectono stratigraphic evolution of the central eastern sector of the sicilian orogen the major remaining issues concerning 1 the occurrence of inferred alpine tethys units far from the region where the remnants of the atw outcrop nebrodi mountains both in a forearc position above the peloritani block to the north and in an active foreland context along the present day southern front of the belt and 2 the diverging tectonic styles from stacked large scale tectonic nappes to foreland imbricated thrust systems rooted into a main basal decollement secondly new constraints are given using analogue modeling to test mechanically the hypothesized structural and tectono stratigraphic evolution of the sftb the experiment simulates the orogenic evolution of the sftb at crustal scale from the oligocene tethys subduction to the middle miocene late pliocene continental collision between the european and african paleomargins the tectono stratigraphic synthesis is used to model the first order mechanical stratigraphy of the sedimentary units involved in the sicilian belt as well as the imprint of the african margin structural inheritance the experiments succeed in reproducing the general structure and tectono stratigraphic evolution of the sftb in particular the models support field observations hypothesing a gravity driven origin of the inferred alpine tethys units intercalated within the forearc and foreland syntectonic sedimentation moreover the model testifies of the main tectonic steps that led to the sftb building first a low tapered accretionary wedge was accreted above the alpine tethys oceanic crust from the oligocene to the early miocene the following underthrusting of the stretched african continental margin and its frontal panormide platform shortened and thickened the accretionary wedge this phase provided favorable conditions for significant pulses of reworked alpine tethys units that intercalated within the forearc and foredeep successions during the middle miocene the decollement of the african meso cenozoic cover panormide platform and imerese sicanian deep water basin enhanced a deep seated deformation phase along with duplexing of the panormide platform beneath the alpine tethys wedge leading to its emersion since the late messinian activation of basement faults led to a generalized emersion of the orogenic units through large wavelength fold culminations accompanied by syn tectonic deposition at their southern limbs concurrently the prism front was partly indented to the southeast by the thick and locally already emerged hyblean platform

distinguishing the roles of autogenic versus allogenic processes in cyclic sedimentation cisco group virgilian and wolfcampian north central texas meter scale transgressive regressive cycles of the subsurface cisco group are composed of marine and nonmarine carbonate and siliciclastic rocks deposited on the eastern shelf of the midland basin during late pennsylvanian and early permian time five cycle types are characterized by thickness magnitude order and principal lithofacies cycle magnitude is defined as the maximum facies shift in a cycle indicating extent of shoreline migration cisco cycles belong to three orders minor intermediate and major and they are superimposed and form a stratigraphic hierarchy each order of cycles has a distinct range of thickness and possibly duration a cycle is also divided into a lower sand poor interval during which coarse siliciclastic supply at the depositional site was diminishing and an upper sand rich interval during which coarse siliciclastic supply was high regional thickness and lithofacies variations of sand rich intervals indicate that progradational infilling at a depositional site lagged marine regression suggesting a delay in sediment supply from the upland source relative to the time of base level fall regional systematic variations in cycle abundance continuity and characteristics along depositional dip and strike record the interplay among regional topography pattern of siliciclastic supply and shelf subsidence which controlled distribution of depocenters and bypass zones and thus stratigraphic completeness and resolution regional persistence of cycles suggests a eustatic control on regional ordered transgressive regressive events in contrast local variations of cycle characters suggest controls by local topography and depositional dynamics which determined depositional loci differential compaction and erosion a predominantly autocyclic cisco record in the upper platform does not imply the absence of allogenic processes an allocyclic cisco record in the lower platform contains abundant autocyclic imprints because allogenic controls on cyclic sedimentation were accomplished through local autogenic processes distinguishing the roles of autogenic versus allogenic processes in cyclic sedimentation is an important step in establishing a high resolution meter scale chronostratigraphy of any sedimentary record 1

on the mesozoic ionian basin summary new seismic reflection profiles of the italian deep crust project crop provide new insights on the structure of the ionian sea in spite of the apennines and hellenides neogene subduction zones two conjugate passive continental margins are preserved at the margins of the ionian sea along the malta escarpment to the southwest and the apulian escarpment to the northeast the ionian sea is likely to be a remnant of the mesozoic tethys ocean confined by these two conjugate passive continental margins the transition from continental to oceanic crust appears sharper to the northeast than to the southwest the basin between southeast sicily and southwest puglia was about 330 km wide and suggests a low spreading rate the inferred oceanic ridge should have been flattened by thermal cooling and buried by later sediments based on stratigraphic and structural constraints to the north in the apennines belt the ocean continued to the northwest this palaeogeography is supported by the seismicity of the apennines slab underneath the southern tyrrhenian sea which implies downgoing oceanic lithosphere the adjacent absence or paucity of deep seismicity does not imply absence of subduction but rather it can be interpreted as due to the more ductile behaviour of the subducted continental lithosphere surprisingly we note that where the oceanic inherited basin is subducting underneath the apennines in the hangingwall of the subduction hinge there are outcropping slices of continental crystalline basement previously deformed by the alpine orogen

conodont biostratigraphy across the permian triassic boundary at chaotian in northern sichuan china abstract detailed conodont biostratigraphy of the permian triassic boundary ptb interval was analyzed at the fossiliferous chaotian section in northern sichuan china the ptb interval at chaotian is composed of the uppermost permian mudstone limestone of the dalong formation and the lowermost triassic marl limestone of the feixianguan formation both representing deep basinal facies the ptb interval is enriched in ammonoids and conodonts and is divided into 6 conodont zones including 1 clarkina changxingensis changxingensis c subcarinata assemblage zone 2 c postwangi c sp b assemblage zone 3 c taylorae c zhejiangensis c changxingensis yini assemblage zone 4 barren intra zone 5 hindeodus parvus zone and 6 isarcicella zone in ascending order the first four zones correspond to the changhsingian whereas the latter two to the lower induan griesbachian the first occurrence fo of h parvus in the lowermost feixianguan formation is regarded as the conodont biostratigraphic boundary from the uppermost dalong formation various taxa of the genus clarkina occurred abundantly and suddenly disappeared at the top of the dalong formation therefore the top of the dalong formation is interpreted as a horizon of the eventostratigraphic boundary on the basis of conodont zones the chaotian section is correlated with the shangsi and meishan gssp of the ptb sections in south china and the zal section in iran

platinum element group variations at the permo triassic boundary in kashmir and british columbia and their significance abstract the end permian marks the greatest extinction in the geological record but there is no consensus on whether it was caused by terrestrial or extraterrestrial factors platinum group elements pge can readily separate extraterrestrial from terrestrial sources and the few studies so far from china and europe indicate terrestrial sources for the pge we report here detailed pge analyses of two expanded sections from the late permian northern and southern hemispheres that allow separate events to be distinguished and confirm a terrestrial source for the pge these sources are either contemporaneous seawater or older basaltic volcanics associated with the sections and the pge were precipitated by a possible combination of development of anoxia in the oceans and post depositional redistribution the pge content in sections at the permo triassic boundary is the result of geochemical and lithological control on metal precipitation that is found in many other black shales throughout geological time

recurrence models and parkfield california earthquakes main shocks of the earthquake sequences that occurred on the parkfield section of the san andreas fault in central california in 1922 1934 and 1966 are characterized by southeast rupture expansion over the same 20 to 30 km long section of the fault whereas the seismic moments for the 1922 and 1934 events are identical to within a precision of 10 the seismic moment for 1966 is 20 greater than for the earlier events to within a precision of 20 the parkfield area seismicity in general seems well described by a recurring moderate size characteristic earthquake repeating the same epicenter magnitude seismic moment rupture area and southeast direction of rupture expansion an unexplained 10 year advance of the 1934 event is the only discrepancy in the hypothesis that the parkfield earthquakes in 1857 1881 1901 1922 1934 and 1966 represent a strictly periodic process assuming the strictly periodic model and the absence since 1966 of the perturbations hypothesized for the 1922 to 1934 period the next characteristic parkfield earthquake should occur between 1983 and 1993

walther s law climate change and upper paleozoic cyclostratigraphy in the ancestral rocky mountains geologists routinely apply walther9s law in interpreting paleoenvironments and paleogeographic scenarios from stratigraphic successions the application of walther9s law however may be problematic in strata that have been influenced by significant and geologically rapid climate change such climatic fluctuation can force depositional environments to change fundamentally rather than migrate laterally resulting in a stratigraphic succession wherein depositional facies vertically superposed rarely or never coexisted laterally upper pennsylvanian carbonate siliciclastic cycles deposited in basins of the southern ancestral rocky mountains display stratigraphic relations that cannot be explained by autogenic and or glacioeustatic mechanisms alone rather intracyclic glacial interglacial climate change was a significant influence cycles of the northern pedregosa basin for example comprise eolian marine siltstone in sharp contact with subtidal peritidal carbonate facies absence of facies mixing suggests a climatic control on silt influx cycles of the western orogrande basin comprise deltaic siliciclastic strata in sharp contact with subtidal peritidal carbonate facies absence of facies mixing truncated siliciclastic progradation and carbonate facies with emergence features similarly support a climatic influence on the siliciclastic component in both systems intracyclic glacial interglacial climatic shift reconfigured depositional environments in cases such as these application of walther9s law could produce erroneous conclusions severe glacial interglacial climate change helps explain the pervasive association of mixed carbonate siliciclastic cyclicity that typifies upper paleozoic strata in many parts of the world

the prelude of the end permian mass extinction predates a postulated bolide impact the mass extinction at the permian triassic boundary ptb is said to have been abrupt and probably caused by an extraterrestrial impact however evidence from the global stratotype section and point gssp of the base of the induan at meishan china shows that the biotic crisis began prior to the level in beds 25 and 26 at which the postulated impact event occurred evidence of such an earlier biotic crisis occurs in other sections in south china and in central and western tethyan regions this event is characterized by the extinction of a range of faunas including corals deep water radiolarians most fusulinids and pseudotirolitid ammonoids and many permian brachiopods in all sections this extinction level is usually a few decimeters to meters below that of the main mass extinction in the event beds 25 and 26 at meishan and their correlatives elsewhere this earlier extinction event happened before the postulated bolide impact at the level of beds 25 and 26 and constrains interpretation of the mechanisms that brought about this greatest mass extinction

motion of africa and adria since the permian paleomagnetic and paleoclimatic constraints from northern libya abstract paleomagnetic and biostratigraphic data from the al azizia formation of northwestern libya consisting of uppermost middle triassic lowermost upper triassic limestones shed new light on the latitudinal drift of africa and adria and related climatic changes a characteristic component of magnetization carried by magnetite delineates paleomagnetic poles which are coincident with coeval poles from the southern alps data from this study and the literature are integrated showing that relatively unrotated remnants of the adria margin like the southern alps e g the dolomites istria gargano apulia and iblei moved in close conjunction with africa since at least permian times a permian cenozoic apparent polar wander apw curve for africa adria is constructed the paleolatitude trend for northern libya calculated from this apw superposed to the zonal latitudinal bands of relative aridity and humidity typical of modern day climate predicts that northern libya drifted northwards from the equatorial belt to the arid tropic during the triassic and crossed the humid subequatorial arid subtropical boundary zone at late triassic times this inference is fully supported by permo triassic palynological and facies analysis from this study and the literature we conclude that a zonal climate model coupled with paleomagnetically constrained paleogeographic reconstructions provides a powerful null hypothesis for understanding past climatic conditions

ostracode eyes as paleoenvironmental indicators physical limits of vision in some podocopids ocular structures are adapted to light conditions and in fossils they may be useful in reconstructing water depth maximum water depth x at which benthic podocopid ostracodes could have useful vision in downwelling sunlight is limited by the ability to distinguish light from dark which is ultimately limited by statistical fluctuations noise in the numbers of photons captured downwelling light is attenuated exponentially therefore it can be shown that where i 0 is the intensity of sunlight just below the ocean9s surface a r is the area of a rhabdom t is the sampling time of the eye n is the minimum number of photons per sampling time for discrimination between light and dark k is the vertical attenuation coefficient v is the frequency of light and h is planck9s constant all quantities are known except t and n t is about 100 milliseconds ms for similar organisms and gaussian statistics indicate that n is about 4 ms regardless t and n are arguments of a logarithm and the calculation is not very sensitive to their values vision with sunlight in podocopid ostracodes should be according to the above limited to the upper 280m in clear ocean water and to about 85m in coastal water the eye structures already are among the most efficient known and modification could produce little improvement for vision in dimmer light the method has application to fossil ostracodes and other groups with eye structures that permit the measurement of the aperture focal length and estimates of the rhabdom size

estimating greater paleodepths with ostracodes especially in past thermospheric oceans abstract modern ostracodes show significant morphologic and taxonomic changes with increasing depth deep psychrospheric faunas are less diverse and more cosmopolitan than shallow faunas individuals are larger rarer and blind their carapaces seem better designed relative to the mass of construction material used speciation is slower taxa are older longer ranging and for the most part now confined to abyssal and bathyal environments deep thermospheric ostracodes found in pre psychrospheric oceans or isolated basins are different their deep origin seems related to the ability of shelf species to submerge past what is a formidable thermal barrier to test morphologic changes that reflect faunal submergence in thermospheric oceans such as existed in the atlantic before about 40 m y b p the basis for an adaptive structural theory is explored this leads to a search for limits expressive of rapid change both in the structure of morphology and in water mass structure examination of the ostracodes from core samples of cretaceous age from nine d s d p sites in the south atlantic suggests that the rio grande rise walvis ridge aseismic system has both been a water mass barrier and yet remained deep at least mid bathyal over the last 100 m y no evidence of either shallow ostracodes from the shelves of africa south america or those of islands were found indicating that models proposed previously that there would have been an archipelago or shallow submerged causeway across the rio grande rise walvis ridge during the late cretaceous are probably in error

cycle symmetry and its causes cisco group virgilian and wolfcampian texas abstract 181 transgressive regressive cycles composed of nonmarine and marine carbonate and siliciclastic rocks of the cisco group on the eastern shelf texas display complex characteristics at both hemicycle and full cycle scales they are delineated on the basis of successive changes of depositional environments stratal boundary relations and stratigraphic position transgressive and regressive stratigraphic environment gradients are defined as the magnitude of environmental shift divided by thickness for each hemicycle they indicate the rates of lateral environmental shifts during transgression and regression cycle symmetry index is defined as the ratio between transgressive and regressive stratigraphic environment gradients it provides a measure of stratigraphic response to controlli g processes most cisco cycles are asymmetrical with steep transgressive and shallow regressive stratigraphic environment gradients indicating cyclic but asymmetrical variations of major allogenic processes over a cycle interval these systematic variations are delineated from climate sensitive rock types stratal thickness and sedimentary features the relative dominance of processes controlling accommodation i e glacio eustasy and basement subsidence versus those controlling sedimentation i e climate upland sediment yield and sediment supply at the depositional site determines cycle symmetry a formulated relation between cycle symmetry index i e stratigraphic response and rates of these processes demonstrates that transgressive sedimentation is controlled by sediment supply whe eas regressive sedimentation is controlled by accommodation this relation is potentially useful in quantitatively predicting stratigraphic responses to specific allogenic processes in cyclic sedimentation five cisco cycle types defined by the type of component lithofacies display the stratigraphic response mainly to noncyclic allogenic and autogenic processes the cycle types have varying magnitude thickness and symmetry they also vary in lateral extent and in abundance a process response model of cyclic sedimentation of the cisco group on the eastern shelf is established it emphasizes the interplay between autogenic and allogenic processes at the sub cycle scale understanding interactions among glacio eustasy climate shelf subsidence sediment supply and depositional dynamics during various stages of transgression and regression is central to a clearer comprehension of the observed variations in cycle characteristics

evolution of permian conodont provincialism and its significance in global correlation and paleoclimate implication the main components of asselian through artinskian conodont faunas found around the world are basically the same and the provincialism is indicated only by less common endemic elements such as gondolelloides and new genus a henderson in north pangea sweetognathus bucaramangus around the equator and vjalovognathus in eastern gondwana provincialism is marked by differences at the species level of mesogondolella neostreptognathodus and sweetognathus during the kungurian and becomes very distinct with differences at the genus level during the guadalupian and lopingian three provinces of permian conodonts referred to as the north cool water province ncwp the equatorial warm water province ewwp and the peri gondwana cool water province gcwp are recognized the ncwp is marked by gondolelloides in the early cisuralian dominance of neostreptognathodus and no or rare sweetognathus in the late cisuralian dominance of merrillina and mesogondolella and absence of sweetognathus in the guadalupian and dominance of merrillina and mesogondolella and absence of iranognathus in the lopingian the ewwp is characterized by the absence of gondolelloides and vjalovognathus in the cisuralian abundance of sweetognathus and pseudosweetognathus in the kungurian late cisuralian jinogondolella and sweetognathus in the guadalupian and clarkina and iranognathus in the lopingian the gcwp is marked by vjalovognathus merrillina in the cisuralian vjalovognathus merrillina and mesogondolella in the guadalupian and vjalovognathus and merrillina in the lopingian mixed faunas are recognized in regions bordering between the ewwp and gcwp including western timor during the artinskian pamirs during the kungurian and the salt range during the guadalupian and lopingian three different conodont zonations are proposed one for each of the three conodont provinces four potential horizons for inter provincial correlation of permian conodonts are recognized they are in ascending order 1 the first appearance of sweetognathus whitei which is closely related to the last occurrence of carboniferous type conodonts such as streptognathodus and adetognathus 2 the first appearance of neostreptognathodus pequopensis 3 the base of the jinogondolella nankingensis zone and 4 the base of the clarkina postbitteri iranognathus erwini zone the spatial and temporal distribution pattern of permian conodonts suggests that temperature is the primary controlling factor evolution of permian conodont provincialism reveals a glaciation during the asselian and sakmarian a global warming during the artinskian a climate cooling in north pangea during the kungurian a continuation of kungurian climate trends in the guadalupian a relatively minor warming during the wuchiapingian a returned cooling in the changhsingian and lower and middle griesbachian and a global warming in the late griesbachian which ended the permian conodont lineage

survival strategies of brachiopod faunas from the end permian mass extinction abstract global reviews reveal that 102 brachiopod species including 40 indeterminate species belonging to 43 genera within 27 families survived the end permian mass extinction in south china the himalayan regions southern tibet nepal salt range and kashmir southern alps italy arctic canada western usa and western australia of these the surviving brachiopods are most abundant and widespread in south china where they occur in 32 of the 42 permian triassic p t boundary sections around the world brachiopod faunas are the most abundant and diverse post extinction survivors and their appearance above the end permian mass extinction horizon somewhat masks recognition of the end permian extinction these surviving brachiopods occur in three stratal intervals corresponding to the mixed fauna beds mfb hereafter 1 3 of the p t boundary beds a sharp drop in diversity of the brachiopod faunas coincides with the widely accepted end permian mass extinction horizon the post extinction brachiopods were also affected by a subsequent crisis corresponding to the boundary between mfb 2 and mfb 3 so that most survivors were extinct approximately 0 7 ma after the end permian mass extinction the surviving brachiopods were mainly productida followed by spiriferida in particular small chonetids chonetid like productellids and smooth thin shelled ambocollid spiriferids are most abundant lingula is extraordinarily abundant and widespread approximately 0 7 ma after the greatest extinction when many regions became devoid of articulate brachiopods widespread broadly adapted and small sized taxa preferentially survived frequent intrageneric speciation of widespread widely adapted generalist genera enabled survival brachiopods to occupy rapidly and efficiently vacant ecospace in the aftermath of the end permian extinction the ecological habitats of the post extinction brachiopods are subdivided into nearshore epeiric sea restricted carbonate platform open carbonate platform ramp and outer shelf environments of these the survival brachiopods are most diverse in the open platform environments the nearshore zone provided ideal habitats for the nonarticulated brachiopods to occupy whereas the survivors in the outer shelf are predominantly chonetids and chonetid like productellids the most successful survivors the productid brachiopods are widely distributed in six types of ecological habitats and thus have no apparent preference for specific environments the end permian extinction resulted in the movement of biogeographical provinces towards the palaeo equator the brachiopods survived mostly in the palaeo equatorial provinces and along the southern margins of the palaeo tethys ocean

tectonic history of the western tethys since the late triassic the tectonic history of the western tethys since the late triassic is illustrated through a set of computer generated plate reconstructions which are based on a rigorous plate motions model of this region the model is constrained by the atlantic plate kinematics and on land geologic evidence and defines 13 tectonic phases spanning the time interval from the late ladinian 230 ma to the present the kinematics associated with the late triassic western tethyan rifts produced the detachment of a large composite fragment from the northern margin of gondwana it can be considered as the eastern propagation of the central pangea breakup during the early jurassic these rift zones became inactive while new zones of extension formed along the southern margin of eurasia the eastern margin of iberia and within the rifted northern gondwana fragment itself plate motions associated with the first two extensional centers can still be considered as an eastern branch of the central atlantic plate kinematics conversely the kinematic parameters of the latter rift result from the composition of the euler rotation describing the central pangea breakup and the euler pole of closure of the paleo tethys ocean the late triassic early jurassic rifting phases determined the formation of a number of independent microplates at the interface between africa and eurasia starting from the early cretaceous convergence between africa and eurasia triggered further deformation within the dispersed continental fragments and the formation of backarc basins at the active margins ultimately leading to an increase in the number of tectonic elements that were moving independently in the western tethyan region during the late cretaceous and the cenozoic the proposed tectonic evolution of the western tethys area is compatible with both global scale plate kinematics and geological constraints from on land data observed across the present day mosaic of displaced terranes surrounding the mediterranean region

permian circumpacific deep water faunas from the western tethys sicily italy new evidences for the position of the permian tethys abstract circumpacific deep water faunas characterized mainly by radiolarians paleopsychrospheric ostracods and conodonts were found in the early middle and late permian deposits pertaining to the sicanian paleogeographic domain of western sicily near the western end of the eurasiatic tethys similar permian deep water faunas are known from the phyllite unit of crete and from oman in the latter area partly above oceanic crust all these occurrences indicate the presence of a late paleozoic tethys ocean immediately north of gondwana

a major anomaly in the carbon cycle during the late cisuralian permian timing underlying triggers and implications abstract the kungurian late cisuralian is associated with elevated atmospheric p co 2 levels and numerous substantial changes in the ocean and terrestrial systems but carbon cycle perturbations through this time interval are poorly understood here three well dated organic carbon isotope 13 c org curves from south china paired with their respective carbonate carbon isotope 13 c carb data published before are presented for the first time their comparison demonstrates that a prominent rapid and synchronous negative excursion in 13 c org and 13 c carb occurred in the early kungurian the herein proposed kcie event dated to ca 277 9 277 4 ma a comparable shift is observed in other deeper water marine sections in south china and two terrestrial sections in north china and eastern australia based on carbon mass balance calculations and a review of concurrent geological records we propose that the kcie event was driven by an intensive volcanism of a large igneous province in northern gondwana dissociation of voluminous methane hydrates induced by this volcanism and the ensuing worldwide conflagrations predicted elevated production of greenhouse gases involved would have warmed the earth and further resulted in ocean stagnation anoxia and acidification all of which are in conformity with the documented sedimentological geochemical and palaeontological data this major anomaly in the carbon cycle in the late cisuralian is considered here to play a key role to promote the transition of the earth to a greenhouse mode

case 23 nomination of precursory seismic quiescence as a significant precursor several cases of extremely strong quiescences have been investigated in great detail and it was found that they are statistically highly significant and that they cannot be reasonably explained by catalog heterogeneity several additional cases of quantitatively measured quiescence have been documented the method of measuring quiescence has progressed from using visual means to using a quantitative approach and the understanding of the noise sources has significantly advanced during the last few years therefore i feel that quiescence is a real phenomenon and the method to detect it has matured to a point that is acceptable for the list of significant precursors although considerably more work needs to be done to understand this parameter and its role in the earthquake generation process

occurrence of anomalous seismic activity preceding large to great earthquakes in northeast india region with special reference to 6 august 1988 abstract seismicity database from 1860 to 1985 of northeast india region bounded by the area 20 32 n and 82 100 e have been analyzed for the identification of precursory swarm anomalous seismic activity preceding large to great earthquakes with m 7 5 it is observed that with the exception of three earthquakes 1908 1912 and 1918 the large earthquakes of 1897 1946 1947 1950 and 1951 1952 were preceded by well developed epoch of swarm anomalous seismic activity in space and time well before their occurrence the seismicity is observed to fluctuate in the order of low high low ranging from 0 0 5 01 33 to 0 0 7 events year prior to these mainshocks during the epochs of normal background swarm anomalous and gap quiescence respectively the duration of precursory gap is observed to vary from 11 to 17 years for mainshocks of m 7 5 8 0 and from 23 to 27 years for m 8 7 and this period is dependent on the magnitude of the mainshocks using the values of magnitude of mainshock m m average magnitude of swarm m p and the precursory time gap t p the following predictive equations are established for the region m m 1 37 m p 1 40 m m 3 log t p 3 27 all the major earthquakes with m b 6 1 occurred during 1963 1988 have been investigated for their association with anomalous seismicity precursory swarms using the events with cutoff magnitude m b 4 5 eleven such events have occurred in the region during the period except one earthquake of 29 may 1976 all the remaining 10 earthquakes were associated in some forms of anomalous seismicity epochs well defined patterns of anomalous seismicity are observed prior to 1964 1965 12 august 1976 and 30 december 1984 m b 5 6 all these mainshocks are preceded by seismicity patterns in the order of low high low similar to that observed prior to the mainshocks from 1897 to 1962 the anomalous seismicity epoch is delineated with extremely high annual earthquake frequency which was preceded and followed by extremely low seismicity epochs of background and gap quiescence phases consequently seismicity rates during anomalous seismicity epoch have always been above normal 1 event year whereas it is always below normal during the preceding and the following epochs a prediction was made using the 1964 swarm based on the m p and t p values that a large earthquake with m 8 0 5 with focal depth 100 40 km could occur any time from 1986 to 1990 in an area bound by 21 25 5 n latitudes and 93 96 e longitude in arakan yoma fold belt it is interesting to note that the 6 august 1988 earthquake with magnitude 7 5 and focal depth 115 km had occurred within the delineated zone in addition three consecutive swarm activities are identified in a limited area within the eastern syntaxis and these were not followed by any mainshock till date and could be potential zone for future earthquake

sediments facies tracts and variations in sedimentation rates of holocene platform carbonate sediments and associated deposits northern belize implications for representative sedimentation rates full text is not available on soar publisher s website http jsedres geoscienceworld org cgi content abstract 74 4 498 doi 10 1306 012004740498

conodont biostratigraphy of uppermost triassic deep water calcilutites from pizzo mondello sicani mountains evidence for rhaetian pelagites in sicily abstract rhaetian pelagites are described for the first time from western sicily in the pizzo mondello area sosio valley sicani mountains where a thick pile of upper triassic cherty calcilutites outcrops the upper triassic pelagic calcilutites of pizzo mondello are divided into three lithostratigraphic units the lower unit consists of a few meters of dark gray marls and clay marlstones equivalent to the mufara fm of carnian age followed by halobia bearing cherty limestones about 300 m thick of late carnian late norian age the upper unit consists of white calcilutites and grey greenish marls containing the conodonts misikella posthernsteini and zieglericonus rhaeticus of rhaetian age these rhaetian deposits are here informally named as portella gebbia limestone in the pizzo mondello succession the norian rhaetian boundary sensu kozur and mock 1991 can be approximated along the lowermost calcilutite bed of portella gebbia limestone containing the first occurrence of m posthernsteini

upper triassic platform margin biofacies and the paleogeography of southern apennines abstract the upper triassic dolomitic successions of the monti della maddalena area southern apennines consist of white heavily recrystallized and cataclastic dolomites generally unsuitable for detailed facies analysis nevertheless evidences of bioconstructions can be found in several localities these evidences are represented by rudstones and possibly boundstones whose main components are fragments of sponges sphinctozoans inozoans chaetetids and corals generally encrusted by foraminifera red algae and problematica this association is much more diversified with respect to that of the microbial serpulid buildups which characterize the platform margin facies of most upper triassic successions of the southern apennines the monti della maddalena biofacies can be more readily compared with the bioconstructed facies of sicily and in general with the dachstein type reef of the tethyan realm the studied successions are interpreted according to the model of cirilli et al 1999 as formed at the margin of a carbonate platform facing a deep basin having good connection with the open sea while the microbial serpulid buildups formed on the margin of intraplatform restricted troughs with poorly oxygenated bottom waters our study discusses the relative paleogeographic position of the apennine platforms and the lagonegro basin the overall picture of the bioconstructed triassic facies distribution in southern apennines together with biofacies data from resedimented facies of lucania are compatible with paleogeographic reconstructions interpreting the monti della maddalena successions as representing the more external sector of the apennine platforms system flanking the lagonegro basin the latter bordered on its external side by apulia was part of a deep mesozoic domain comprising the imerese sicani basin of sicily and connected westward with the east mediterranean branch of western tethys our data exclude the possibility that the lagonegro basin was located in an internal position with respect to all the apenninic and apulian platforms system

early triassic induan olenekian conodont biostratigraphy global anoxia carbon isotope excursions and environmental perturbations new data from western australian gondwana the early triassic induan olenekian stage boundary dienerian smithian sub stage boundary has been identified at a depth of 2719 25m in the petroleum exploration well senecio 1 located in the northern perth basin western australia conodont faunas represent three conodont zones in ascending order the neospathodus dieneri zone the neospathodus waageni eowaageni zone and the neospathodus waageni waageni zone the induan olenekian dienerian smithian boundary is placed at the base of the neospathodus waageni eowaageni zone equivalent to the first appearance of neospathodus ex gr waageni utilised elsewhere and adopted by the iugs ics triassic subcommission to define the base of the olenekian bulk kerogen 13c carbon isotopes define a positive peak of c 4 per mille that essentially coincides with the induan olenekian boundary as seen in proposed global stratotype sections and points gssps in south china and spiti india demonstrating the global utility of this level for correlation an anoxic zone is recognised in the lower part of the senecio 1 core and the upper limit of this zone is dated as late induan late dienerian temporal and spatial mapping of marine anoxia and dysoxia globally demonstrates that pulses of dysoxia anoxia affected shallow marine zones at different times in different locations dysoxia anoxia in the shallow marine environment appeared in the latest permian at the extinction level later than in the deep marine environment and appears to be largely restricted to the induan griesbachian and dienerian and early olenekian smithian temporally and geographically restricted upwelling of an oxygen minimum zone into the ocean surface layer due to environmental perturbations including extreme global warming increased terrestrial chemical weathering intensity and continental erosion sea level rise and changes in marine nutrient inventories and productivity rates is interpreted as a likely cause of observed variation in shallow marine dysoxia anoxia in the early triassic

catastrophic dispersion of coal fly ash into oceans during the latest permian extinction the eruption of the siberian trap flood basalts resulted in the heating and combustion of coals and organic rich sediments at the time of the permian mass extinction the presence of char in distant lake sediments linked to the eruption suggests that fly ash could have been generated by the coal combustion and then dispersed globally creating toxic marine conditions

search for evidence of impact at the permian triassic boundary in antarctica and australia life on earth was almost destroyed some 250 m y ago in the most profound of all known mass extinction events we investigated the possible role of impact by an extraterrestrial bolide through chemical and mineralogical characterization of boundary breccias search for shocked quartz and analysis for iridium in permian triassic boundary sections at graphite peak and mount crean antarctica and wybung head australia thin claystone breccias at the isotopically and paleobotanically defined boundary at all three locations are interpreted as redeposited soil rather than impact ejecta the breccias at all three locations also yielded shocked quartz but it is an order of magnitude less abundant 0 2 vol and smaller only as much as 176 micrometers m diameter than shocked quartz at some cretaceous tertiary boundary sites faint iridium anomalies were detected up to 134 pg g 1 these values are an order of magnitude less than iridium anomalies at some cretaceous tertiary boundary sites furthermore peak iridium values are as much as 1 m below the isotopically and paleobotanically defined boundary the idea that impact caused the extinctions thus remains to be demonstrated convincingly

precursory seismic quiescence past present and future precursory seismic quiescence has played a major role in most of the succesful earthquake predictions made to date in addition to these successes the number of detailed post mainshock documentations of precursory quiescence is steadily growing these facts suggest that precursory quiescence will play an important role in earthquake prediction programs of the future for this reason it is important to critically evaluate the present state of knowledge concerning this phenomenon the history of observations of precursory seismic quiescence includes work on seismic gaps and seismic preconditions as well as actual studies of temporal quiescence these papers demonstrated the importance of quantitative evaluation of seismicity rates and the benefits of systematic analysis during the early 1980 s the impact of man made effects on seismicity rates was demonstrated for the first time despite progress in catalog understanding the identification and correction of man made seismicity changes remains as the major barrier to earthquake prediction using these data effects of man made changes are apparent in many past studies of seismicity patterns making the results difficult to evaluate recent experience with real time anomalies has demonstrated the necessity of determining the false alarm rates associated with quiescence precursors determination of false alarm rates depends on quantitative definitions of anomalies and statistical evaluations of their significance a number of successful predictions which have been made on the basis of seismic quiescence provide important lessons for present and future work there are many presently unanswered questions regarding seismic quiescence which must be answered before we can determine the reliability of this phenomena as a precursor

stress distribution pattern and swarm occurrences abstract at the himalayan trench three consecutive swarms i e the precursory swarm the main shock swarm and the aftershock swarm have been reported to occur in small epicentral regions in these swarms the magnitudes of the main shock events are one to two units higher than the other two these swarms appear to be related to each other in order to establish the relationship between the first two swarms focal mechanism studies for main shocks and the precursory swarms were carried out the study of the precursory swarm demonstrates the converging nature of stresses in the epicentral region of the main shock swarm this suggests that the stresses responsible for the precursory swarms are also the cause of the main shock swarms the aftershock swarms are the result of the interaction of the converging stresses with the outward stresses generated due to adjustment of faulted blocks during large earthquakes in view of the above it can be asserted that precursory swarms are precursors to the main shocks

permian artinskian to wuchapingian conodont biostratigraphy in the tieqiao section laibin area south china permian strata from the tieqiao section jiangnan basin south china contain several distinctive conodont assemblages early permian cisuralian assemblages are dominated by the genera sweetognathus pseudosweetognathus and hindeodus with rare neostreptognathodus and gullodus gondolellids are absent until the end of the kungurian stage in contrast to many parts of the world where gondolellids and neostreptognathodus are the dominant kungurian conodonts a conodont changeover is seen at tieqiao and coincided with a rise of sea level in the late kungurian to the early roadian the previously dominant sweetognathids were replaced by mesogondolellids the middle and late permian guadalupian and lopingian series witnessed dominance of gondolellids jinogondolella and clarkina the common presence of hindeodus and decimation of sweetognathus twenty main and seven subordinate conodont zones are recognised at tieqiao spanning the lower artinskian to the middle wuchiapingian stage the main first appearance datum zones are in ascending order by stage the sweetognathus sw whitei sw toriyamai and sw asymmetrica n sp zones for the artinskian the neostreptognathodus prayi sw guizhouensis sw iranicus sw adjunctus sw subsymmeticus and sw hanzhongensis zones for the kungurian the jinogondolella j nankingensis zone for the roadian the j aserrata zone for the wordian the j postserrata j shannoni j altudaensis j prexuanhanensis j xuanhanensis j granti and clarkina c hongshuiensis zones for the capitanian and the c postbitteri zone and c transcaucasica zone for the base and middle of the wuchiapingian the subordinate interval zones are the pseudosweetognathus ps costatus ps monocornus hindeodus h gulloides pseudohindeodus ramovsi gullodus g sicilianus g duani and h excavates zones in addition three new species gullodus tieqiaoensis n sp pseudohindeodus elliptica n sp and sweetognathus asymmetrica n sp are described age assignments for less common species e g g duani h catalanoi and pseudosweetognathus monocornus etc are reassessed based on a rich conodont collection

two episodes of environmental change at the permian triassic boundary of the gssp section meishan abstract high resolution stratigraphic records through the permian triassic boundary ptb interval of the global stratotype section and point gssp at meishan zhejiang province china reveal that the ptb crisis was not a single abrupt catastrophe a bed by bed analysis of environmental and biotic changes makes clear that the crisis can be resolved into two discrete episodes each consisting of three stages a unstably oscillating conditions b peak crisis conditions and c ameliorating conditions the first crisis episode commenced in bed 23 peaked in beds 24e 26 and ameliorated in beds 27 and 28 while the second crisis episode commenced in bed 29 peaked in beds 34 38 and ameliorated in beds 39 and higher the macroscopic mass extinctions happened not at the beginning nor the end of each cycle but at times when the crisis or perturbation of environments began these extinction events do not show detectable feedbacks to concurrent environmental changes in each episode cyanobacteria proliferation postdated the macroscopic extinction while proliferation of green sulfur bacteria predated the environmental crisis causational analysis between environmental and microbial changes show that geomicrobial functional groups exercised pronounced effects on the marine c n s cycles and ocean redox conditions during the ptb crisis it is possible thus that the microbial crises played an important role in strengthening or evening triggering the environmental crisis

iceberg rafting and scouring in the early permian shoalhaven group of new south wales australia evidence of heinrich like events abstract this paper describes multiple layers of ice rafted debris and an ice scour structure in early permian marine strata within the shoalhaven group of the sydney basin new south wales australia strata were deposited on a high latitude glacially influenced continental margin during the final stages of late palaeozoic glaciation between 277 and 260 ma poorly sorted ice rafted debris forming layers up to 1 25 m thick is common within inner to outer shelf and continental slope facies of the shoalhaven group more than 120 layers can be identified these are argued to record the enhanced delivery of debris by icebergs drifting north from marine based antarctic ice margins deformation structures in associated sediments are interpreted as iceberg scours and ice keel turbates associated glendonites record early diagenesis of organic rich sediment and bottom water temperatures close to freezing a speculative hypothesis relates layers of ice rafted debris within the shoalhaven group to multiple episodes of accelerated calving at the margins of a marine based early permian ice sheet in east antarctica these events may be analogous to late pleistocene heinrich events when huge armadas of icebergs were released from the marine based laurentide ice sheet and triggered abrupt changes in ocean circulation and climate similar forcing may have characterized the early permian ice ocean system regardless of the climatic significance of ice rafted layers this is the first time such facies have been documented in the pre pleistocene literature to date few ice scour structures and no ice keel turbates have been reported

anomalous seismicity and earthquake forecast in western nepal himalaya and its adjoining indian region precursory swarms associated with major earthquakes in the western nepal himalaya and its adjoining region bounded by 28 0 31 0 n and 79 5 82 2 e have been studied using seismicity data from 1963 to 2006 the delineation of preparation zones for future seismic disturbances is carried out using the temporal and the spatial distribution of earthquakes considering the events with cutoff magnitude m b 4 3 in four anomalous episodes normal background n anomalous swarm a precursory gap g and main shock sequence m respectively five cases of anomalous seismicity have been identified including two cases for which quiescence episodes still continue three moderate earthquakes of 1980 m b 6 1 bajhang 1984 m b 5 6 bajura and 1999 m b 6 6 chamoli in western nepal and its adjoining indian region were preceded by well defined patterns of anomalous seismicity precursory swarm two additional cases of anomalous seismicity patterns were observed 1 1999 2006 and 2 2003 2006 in these two cases no main shock has yet occurred however the seismicity from 1999 onwards has fluctuated from low to high to low as in the precursory sequences for previous earthquakes the occurrence of the swarm sequence followed by a quiescence phase which is still continuing is an indication of a precursory seismicity gap in the region from the predictive equations developed for the himalayan frontal arc it is estimated that an earthquake of m 6 5 0 5 may occur at any time up to 2011 in an area bounded by 29 3 30 5 n and 81 2 81 9 e in the focal depth range 10 30 km

low seasonality in central equatorial pangea during a late carboniferous highstand based on high resolution isotopic records of brachiopod shells the relationship between permian carboniferous glacial cycles and low latitude climate remains a subject of vigorous debate this study investigated seasonality and regional environmental variability in a portion of central equatorial pangea during a late pennsylvanian highstand using stable isotope and trace element analyses of brachiopod shells from the virgilian ames member of the conemaugh group in the appalachian basin u s a well preserved thick shelled neospirifer dunbari specimens were serially sampled across growth bands to elucidate a record of seasonal variability during the life of the organisms because neospirifer only colonized this marginal basin during near maximum highstands when stable near marine salinities were established these data are a direct proxy for intra annual climate fluctuations during interglacial times neospirifer specimens show remarkably little internal chemical variability with 18 o generally fluctuating by 0 4 or less and 13 c fluctuating by less than 1 5 within a single specimen moreover total 18 o variability between all specimens is only 1 5 this lack of variation reflects a homogeneous nonseasonal to weakly seasonal climate during the ames highstand both 18 o and 13 c are 1 5 lower than those of other virgilian specimens from regions with a more proximal connection to the open ocean suggesting at least moderate freshwater influence in the appalachian basin during this time although salinities remained close enough to marine levels to maintain stenohaline fauna thus brachiopod seasonal records indicate normal moist tropical conditions during this penultimate carboniferous interglacial with no evidence for strong monsoonal variations in temperature or rainfall

new permian triassic conodont data from selong tibet and the youngest occurrence of vjalovognathus the controversial biostratigraphy of the well known permo triassic p t boundary section at selong south tibet is reinvestigated based on large conodont samples the conodont data in this study confirm that the upper part of selong formation and the waagenites bed in the lower part of kangshare formation as changshingian age just above the waagenites bed the otoceras latilobatum bed is assigned to the basal triassic due to the presence of h parvus zone the discovery of vjalovognathus a cool temperature tolerant form in changshingian strata allows the youngest vjalovognathus species v carinatus sp nov to be described and a possible permian vjalovognathus evolutionary trend proposed in ascending order this is v australis late sakmarian early artinskian v shindyensis early kungurian v nicolli late kugurian early roadian and ultimately v carinatus sp nov changshingian the last species v carinatus sp nov is also found in the pre mass extinction beds at guryul ravine kashmir allowing correlation with south tibet

tectonic history of the lagonegro domain and southern apennine thrust belt evolution abstract the tectonic history of the lagonegro domain in southern italy is an intriguing topic for the mesozoic mediterranean paleogeography and is important for reconstructions of the tethys previous interpretations postulate the paleogeographic position of a deep lagonegro molise sicilide basinal domain between the external apulia carbonate platform to the east and the internal apenninic carbonate platform i e the alburno cervati maddalena mountains to the west a second and separate deep basin more to the west was the home of the liguride units which cover extensive areas of the southern apennines following an extensive review of previously published concepts and on the base of the structural interpretation of the southern apennines thrust belt using additional subsurface data and extensive field mapping the authors now suggest that all deep basinal units of the southern apennines i e the ligurides the lagonegro units and the molise sicilide units derive from internal areas located to the west with respect to a coeval wide carbonate platform slope shallow basin complex which in its pre middle miocene reconstruction extended from apulia well beyond the present day tyrrhenian coast of southern italy the basinal units were first assembled as an accretionary wedge and overthrusted during the late miocene over the carbonate platform slope shallow basin complex the liguride lagonegro molise sicilide accretionary wedge was later cut by an envelopment thrust which overthrust the previously underlying platform complex over the previously emplaced complex accretionary wedge our hypothesis in part revives an old concept proposed by selli 1962 and requires further testing and research we conclude that paleogeographic reconstructions of the southern apennines and the mediterranean tethys are still in a state of flux

late palaeozoic global changes affecting high latitude environments and biotas an introduction abstract the late palaeozoic ice age lpia spanning approximately from 320 ma serpukhovian late mississippian to 290 ma mid sakmarian early permian represents the vegetated earth s largest and most long lasting regime of severe and multiple glaciations involving processes and patterns probably comparable to those of the last ice age accompanying the lpia occurred a number of broadly synchronous global environmental and biotic changes these global changes as briefly reviewed and summarized in this introductory paper comprised but are not limited to the following massive continental reorganization in the lead up to the final assembly of pangea resulting in profound changes in global palaeogeography palaeoceanography and palaeobiogeogarphy substantially lowered global atmospheric carbon dioxide concentrations p co 2 coupled with an unprecedented increase in atmospheric oxygen concentrations reaching earth s all time high in its last 600 million year history sharp global temperature and sea level drops albeit with considerable spatial and temporal variability throughout the ice age and apparently a prolonged period of global sluggish macro evolution with both low extinction and origination rates compared to other times in the aftermath of the lpia the world s climate entered into a transitional climate phase through the late early to middle permian before its transformation into a greenhouse state towards the end permian in recent years considerable amount of data and interpretations have been published concerning the physical evidence in support of the lpia its broad timeframe and eustatic and ecosystem responses from the lower latitudes but relatively less attention has been drawn to the impact of the ice age on late palaeozoic high latitude environments and biotas it is with this mission in mind that we have organized this special issue with the central focus on late palaeozoic high latitude regions of both hemispheres that is gondwana and northern eurasia our aim is to gather a set of papers that not only document the physical environmental changes that had occurred in the polar regions of gondwana and northern eurasia during the lpia but also review on the biotic responses at different taxonomic ecological and spatial scales to these physical changes in a refined chronological timeframe this introductory paper is designed to provide a global context for the special issue with a brief review of key late palaeozoic global environmental changes including changes in global land sea configurations atmospheric chemistry global climate regimes global ocean circulation patterns and sea levels and large scale biotic biogeographic and evolutionary responses followed by a summary of what we see as unresolved scientific issues and various working hypotheses concerning late palaeozoic global changes and in particular the lpia as a possible reference to future research

synchrony and causal relations between permian triassic boundary crises and siberian flood volcanism the permian triassic boundary records the most severe mass extinctions in earth9s history siberian flood volcanism the most profuse known such subaerial event produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less analysis of 40 ar 39 ar data from two tuffs in southern china yielded a date of 250 0 0 2 million years ago for the permian triassic boundary which is comparable to the inception of main stage siberian flood volcanism at 250 0 0 3 million years ago volcanogenic sulfate aerosols and the dynamic effects of the siberian plume likely contributed to environmental extrema that led to the mass extinctions

early triassic oceanic red beds coupled with deep sea oxidation in south tethys abstract carbonate oceanic red beds orbs are unusual in phanerozoic shelf settings but can be widespread during discrete intervals several scenarios have been invoked to explain the origin of these orbs but there remains uncertainty about the process by which the red pigmentation of orbs forms here we propose that the occurrence of orbs at intermediate water depths in shelf regions is controlled by fluctuations in the redox state of deeper waters we have examined early triassic peri gondwana shelf sections in south tibet which show the development of spathian late early triassic orbs at intermediate water depths the red color of these orbs is imparted by randomly dispersed hematite crystals that are microns in size showing weak alteration by late burial diagenesis widespread anoxia in both shelf seas and the oceanic realm was well developed in the early triassic synchronous occurrence of spathian orbs in deep shelf regions is closely related to the improved oxidation in deeper settings from anoxia to dysoxia based on changes in the redox proxy of pyrite framboid sizes it is therefore inferred that prolonged deep water anoxia might serve as source of fe ii for the formation of orbs when intensified upwelling develops the global occurrence of early triassic orbs is coincident with the significant rebound of biodiversity after the permian triassic mass extinction indicating the occurrence of orbs marks the terminal stage of an oceanic anoxic event and orbs can serve as an indicator of the ameliorated marine ecosystem

transgressive wave ravinement on an epicontinental shelf as recorded by an upper pennsylvanian soil nodule conglomerate sandstone unit kansas and oklahoma u s a abstract a thin 3 25 cm persistent conglomerate sandstone unit occurs at the base of the transgressive systems tract of an upper pennsylvanian cyclothem below a transgressive limestone in outcrop and subsurface in se kansas and ne oklahoma it has an erosional base and a sharp top and is composed of calcitic clasts some shell fragments and quartz sand and rare coal fragments clasts are rounded equant to elongate coarse sand to pebble sized and moderately to well sorted they are micritic to microsparitic or radial fibrous calcite grains and pisoids micritic and microsparitic clasts are heterogeneous and contain rounded to elongate moulds and radiating or concentric spar or micrite filled cracks pisoids have micrite cores and superficial calcite or clay rims the clasts have similar texture and composition to the calcitic nodules and rhizoconcretions in underlying paleosols and thus were probably derived from these soil nodules upper shoreface erosion during shoreline transgression excavated the underlying paleosols and eroded coeval transgressive deposits landwards of the shoreline the eroded sediments were then reworked and transported to the lower shoreface and inner shelf by storm return flows to be deposited as a soil nodule conglomerate sandstone unit its base is an amalgamated surface of wave ravinement and initial transgression as well as the lower sequence boundary the widespread conglomerate sandstone unit suggests extensive transgressive wave ravinement on an epicontinental shelf the transgressive record composed of upward deepening dominantly fine grained lithofacies defines a new type t c4 of transgressive record which is composed of mixed carbonate and siliciclastic lithofacies with a simple transgressive lag on a low relief shelf

characteristics of earthquake sequence in northern himalayan region of south central tibet precursor search and location of potential area of future earthquake abstract this paper reports that three earthquake sequence occurred in 1996 m b 5 9 1998 m b 5 8 and 2004 2005 m b 6 2 6 3 were observed preceding the anomalous seismic activity the nature of anomalous seismicity associated with these earthquakes have been investigated considering earthquakes with m b 4 1 cut off magnitude for this region in four seismic episodes nagm normal background n anomalous swarm a precursory gap g and mainshock sequence m respectively it is established here that the anomalous seismicity swarm patterns follow episodes of relatively very low seismic activity and it is an important finding to visualize that an area might be preparing for the occurrence of a forthcoming mainshock such anomalous seismic patterns were observed prior to medium size mainshocks that occurred from 1963 to 2006 in south central tibet sct region to the north of central himalaya from these observations it may be inferred here that the patterns of anomalous seismicity earthquake swarms may be considered as an important parameter precursor for the forecasting of long range earthquake hazards in the sct region in consideration of spatial and the temporal clustering of swarm events that are prominent and confined in a vertical column of 10 45 km enabled to locate potential area enclosed by 29 6 30 1 n and 87 8 88 1 e where future earthquake of magnitude 6 0 and above in the depth range 25 15 km may be seated in view of this multi parameter short term precursory signals monitoring is suggested for the delineated preparatory area to make earthquake prediction forecasting programs more meaningful

brachiopods from the permian triassic boundary beds at the selong xishan section xizang tibet china the brachiopods from the waagenites bed and the upper part of the coral bed above and below the permian triassic sequence boundary at the selong xishan section of southern xizang suggest a rich brachiopod fauna existing in selong and a rapid invasion of tethyan brachiopods into the himalayas at the very end of the permian a transgression beginning from the waagenites bed and a rapid flooding at the beginning of the triassic is reflected by changes in composition of the permian brachiopod assemblages in selong however the dominant forms in the permian triassic sequence boundary beds including krotovia spiriferella and neospirifer extend from the underlying beds of the selong group without significant evolutionary change a brief discussion of each taxon and descriptions of two new species stenoscisma selongensis and martinia attenuatelloides are presented

milankovitch climatic signals in lower triassic olenekian peritidal carbonate successions nanpanjiang basin south china abstract meter scale peritidal carbonate strata from an isolated platform in the nanpanjiang basin of south china were tested for the presence of periodic or quasi periodic climatic signals these signals provide information on factors controlling cyclic sedimentation in the equatorial eastern tethys during the early triassic greenhouse period parasequences are composed of shallowing upward successions of subtidal facies including skeletal packstone and grainstone calcimicrobial boundstone and oolitic packstone and grainstone intertidal laminated lutite and ribbon rock and rare supratidal microbial laminite parasequence stacking patterns display three orders of cyclicity suggesting hierarchical stratigraphic relationships gamma analysis of kominz and bond earth planet sci lett 48 1990 233 244 was used to estimate facies dependent thickness time conversion factors i e s and to construct tuned and untuned time series for two stratigraphic sections spectra of these time series indicate the presence of quasi periodic signals with prominent short eccentricity 94 9 131 2 kyr short obliquity 35 8 kyr and long precessional index 21 2 kyr peaks and minor long eccentricity 412 9 kyr long obliquity 45 3 kyr short precessional index 17 7 kyr and constructional tone 9 7 kyr peaks when calibrated on the tuned spectra thus milankovitch climatic forcing probably greatly influenced sedimentation the calibration indicates that the subtidal facies has a sedimentation rate of 24 6 30 7 cm kyr and the intertidal supratidal facies has a rate of 2 7 6 0 cm kyr the estimated duration of deposition of the two sections is 1139 1423 kyr and corresponds to a stratigraphic completeness of 32 92 the completeness is much greater than that of icehouse stratigraphic records we speculate that variations in carbonate productivity and environmental conditions driven by milankovitch climatic forcing combined with low amplitude sea level fluctuations were likely major controls on cyclic sedimentation furthermore evolutional spectra of the two sections show that dominant milankovitch climatic forcings varied from short eccentricity obliquity to long precessional index during the course of sedimentation some spectral differences between the two sections suggest variations in depositional recording mechanisms of milankovitch climatic signals between platform interior and windward platform margin

climatic implications from the sequential changes in diversity and biogeographic affinities for brachiopods and bivalves in the permian of eastern australia and new zealand abstract brachiopoda and bivalvia of successive macro invertebrate zones of eastern australia and new zealand are analysed to demonstrate a sequence of climatic change throughout the permian period reflecting glacial episodes separated by warmer intervals three such glacial intervals are indicated for the early cisuralian permian a long asselian episode a brief artinskian episode and a substantial kungurian interval followed by a cold roadian interval middle permian guadalupian and a very late permian lopingian episode markedly warmer intervals developed in the possibly late asselian baigendzinian and much of the lopingian in addition relatively long cool times allowed the flourishing and comparative diversification of eastern australian faunas at several stages

permo triassic boundary superanoxia and stratified superocean records from lost deep sea pelagic cherts of japan and british columbia canada recorded a long term and worldwide deep sea anoxic oxygen depleted event across the permo triassic or paleozoic and mesozoic boundary 251 2 million years ago the symmetry in lithostratigraphy and redox condition of the boundary sections suggest that the superocean panthalassa became totally stratified for nearly 20 million years across the boundary the timing of onset climax and termination of the oceanic stratification correspond to global biotic events including the end guadalupian decline the end permian extinction and mid triassic recovery

earthquake triggering during preparation for great earthquakes seismic quiescence has been proposed as a precursor to many large earthquakes in this paper we present two cases in which precursory quiescence is interrupted several years prior to great earthquakes by triggered events in the upcoming rupture areas this triggering results in complex precursory patterns which include seismic quiescence and triggered events prior to the kermadec earthquake of 1976 ms 8 0 events in the rupture zone were triggered by a quake on the outer rise and one near the future mainshock epicenter events were triggered by an earthquake on an adjacent segment of the plate interface and by one near the epicenter of the new hebrides earthquake of 1980 ms 8 0 we propose that two preconditions must be fulfilled for triggering to occur first the stress in the region must be close to the failure stress and second nearby events must occur which are large enough to affect the stress field but not large enough to cause an immediate mainshock

the relationships between soft sediment deformation structures and synsedimentary extensional tectonics in upper triassic deep water carbonate succession southern tethyan rifted continental margin central sicily abstract we describe soft sediment deformation structures into the upper triassic cherty limestone outcropping in the pizzo lupo section central sicily italy pertaining to the deep water palaeodomain of the southern tethyan margin in the study section mainly consisting of thin bedded mudstone marl alternations with bedded chert intercalations some lithofacies have been separated on the basis of the abundance of the calcium carbonate clay content and the overall textural features the deformational structures displaying different deformational styles as folded and faulted beds disturbed layers clastic dikes and slumps occur mainly in the deformed horizons that involve marl dominated lithofacies small scale water escape structures involve beds with nodular fabric synsedimentary faults affect the mud limestone dominated lithofacies which are characterized by fault rotating blocks producing lateral thinning these bodies appear to have moved coherently along an overall planar surface we relate these soft sediment deformations to slump sheets associated with down slope sliding of sedimentary masses the deformation mechanism and driving force for these soft sediment deformations are due essentially to gravitational instability and dewatering detailing rotational slump and translational glide slides and water escape are the main processes causing the distinguished deformational styles the synsedimentary extensional tectonics that affected the upper triassic pelagic deposits was the triggering process responsible for the instability of the seafloor inducing loss of coherence of the unconsolidated sediments on the sea bottom developing a large number of gravity driven slides the analysis of both of these ssdss and their relationships with the structural scenario allow us to hypothesise that they are seismically induced

characteristics stratigraphic architecture and time framework of multi order mixed siliciclastic and carbonate depositional sequences outcropping cisco group late pennsylvanian and early permian eastern shelf north central texas usa abstract the cisco group on the eastern shelf of the midland basin is composed of fluvial deltaic shelf shelf margin and slope to basin carbonate and siliciclastic rocks sedimentologic and stratigraphic analyses of 181 meter to decimeter scale depositional sequences exposed in the up dip shelf indicated that the siliciclastic and carbonate parasequences in the transgressive systems tracts tst are thin and upward deepening whereas those in highstand systems tracts hst are thick and upward shallowing the sequences can be subdivided into five types on the basis of principal lithofacies and exhibit variable magnitude of facies shift corresponding to variable extents of marine transgression and regression on the shelf the sequence stacking patterns and their regional persistence suggest a three level sequence hierarchy controlled by eustasy whereas local and regional changes in lithology thickness and sequence type magnitude and absence were controlled by interplay of eustasy differential shelf subsidence depositional topography and pattern of siliciclastic supply the outcropping cisco group is highly incomplete with an estimated 6 11 stratigraphic completeness the average duration of deposition of the major third order sequences is estimated as 67 102 ka on the up dip shelf and increases down dip while the average duration of the major sequence boundaries sb is estimated as 831 1066 ka and decreases down dip the nondepositional and erosional hiatus on the up dip shelf was represented by lowstand deltaic systems in the basin and slope

palaeoenvironments of the permian triassic transition sections in kashmir india abstract detailed measurements of two permian triassic boundary sections at guryul ravine and pahlgam in kashmir indicate continuous sedimentation across the boundary though with a marked change from shallow storm influenced shelf to deeper shelf below wave base successive shell beds through the 2 5 m thick transitional latest permian section at guryul formed as in situ accumulations with little sign of either erosional breaks or condensation faunal change takes place gradually in the late permian transition beds as elsewhere in the tethyan sections there is no major event layer at the permian triassic boundary and little evidence for dysaerobic conditions both the kashmir and east greenland permian triassic sections have sedimentation rates that are orders of magnitude greater than at the condensed meishan reference section they show that the end permian extinction was associated with transgression but not with immediate onset of anoxic conditions macrofaunal extinction seems associated with reduction in primary production which would also explain the dwarfism of fossils found in all permian triassic sections studied so far

constrains on the origin and history of the eastern mediterranean basin abstract the basin formed along the northern passive margin of gondwanaland as a relict of the mesozoic neotethys in early mesozoic time though direct information from the basin itself is meagre the geology of its passive margins and the regional framework of the tethys evolution constrain the formation and history of the basin the eastern mediterranean and its passive margins are interpreted to have formed as a result of several faulting and continental breakup phases from early permian to middle jurassic times before pangaea s complete disintegration this led to the detachment of the eratosthenes and tauride blocks from the margins of the levant and herodotus basins respectively the latter merged in the northeast with the cyprus basin that extended along arabia s northern margin the main rifting probably occurred in the triassic leading to seafloor spreading in the herodotus and cyprus basins while along the levant margin important rifting also occurred in the jurassic during the initial rifting stages extension perpendicular to the levant margin was important but subsequently the tauride block drifted mainly northward the existence of the passive margins and slopes of the eastern mediterranean is documented at least from the end of the middle jurassic until then the basin was probably narrow 200 300 km but during the main phase of the africa laurasia separation it grew to twice its present width or more this scenario depends critically on the interpretation that the tauride block was originally located next to northeastern africa on the western side of the eratosthenes block plate convergence and consumption of the northern portion of the basin have taken place since mid cretaceous times but the active convergent boundary on its northern side formed only in the neogene by modification of earlier structures some intra plate deformation also took place especially in the neogene but it hardly changed the original configuration of the remaining portion of the basin

a possible bridge between adria and africa new palaeobiogeographic and stratigraphic constraints on the mesozoic palaeogeography of the central mediterranean area abstract dinosaur records in central and southern italy testify to the occurrence of a diverse dinosaur fauna on the apennine and apulian carbonate platforms at least from the tithonian to the santonian most of the palaeogeographic reconstructions show these domains as topographically isolated areas separated by deep pelagic basins and far from emerged continental areas thus they hardly justify the long lasting occurrence of these terrestrial vertebrates recent studies on the mesozoic panormide carbonate platform western sicily yielded important stratigraphical and palaeontological data which provide evidence for a convincing explanation of this unresolved problem the recent discovery of a theropod bone in mid cretaceous peritidal levels of the panormide platform as well as the anomalous subsidence of this palaeogeographic domain strongly support the existence of a crustal sector filtering bridge which connected africa to adria

on the possibilities of premonitory swarms for three sequences of earthquakes of the burma szechwan region abstract short term spatial and temporal variations in seismicity prior to the three sequences of earthquakes of m b 5 8 of the burma szechwan region are studied six years 1971 1976 of isc seismicity data as reported in the regional catalogue of earthquakes are considered during the period six earthquakes of body wave magnitude m b 5 8 occurred in four sequences of these three sequences are preceded by swarm activity in the epicentral regions evison 1977b suggested that the swarm before the sequences of large shocks is a possible long term precursor he derived the conclusion by analyzing earthquakes in new zealand and california the analysis of the seismicity data for the region under investigation supports evison s view and suggests that a relation between swarms and sequences of large events exists the precursory time period i e the time from beginning of the swarm to the main shock for the szechwan earthquakes of m b 5 9 feb 6 1973 and m b 5 8 may 10 1974 and the burma earthquake of m b 6 2 aug 12 1976 are 305 317 and 440 days respectively