palaeoenvironmental change during the end guadalupian permian mass extinction in sichuan china abstract the end guadalupian mass extinction has been investigated in sichuan province sw china in the south of the province the platform carbonates of the maokou formation are overlain by the emeishan flood basalts a possible factor in the extinction event and in the north of the province the formation is succeeded by shallow marine carbonates of the wuchiaping formation late permian the extinction event is primarily recorded by the loss of fusulinaceans and possibly by species level turnover amongst calcareous algae the high diversity middle permian microfossil assemblages are last seen beneath a surface recording widespread emergence and karstification in northern sichuan emergence occurred early in the capitanian stage and the succeeding strata record restricted hypersaline deposition that preceded the deposition of a thick ash horizon the wangpo bed these mid capitanian arid conditions are replaced by humid conditions towards the end of the stage as indicated by the development of a widespread coal seam in southern sichuan only a thin development of this humid coaly facies is seen developed atop the maokou karstic surface and below the oldest flood basalt the guadalupian interval saw the development of large c isotope excursions in the carbonate record these include a positive then negative swing late in the capitanian and a newly discovered negative spike superimposed on an early capitanian heavy interval this spike may be a global phenomenon but the magnitude 8 may have been exaggerated by an increased contribution from light respired c derived from soils during relative sea level fall a plethora of environmental factors approximately coincide with the extinction event including regression acidic volcanism and flood basalt volcanism making it difficult to unravel the relative significance of each

age and duration of the emeishan flood volcanism sw china geochemistry and shrimp zircon u pb dating of silicic ignimbrites post volcanic xuanwei formation and clay tuff at the chaotian section abstract the age and duration of the emeishan basalts sw china remain poorly constrained largely due to the severe thermo tectonic overprinting of the ar ar system and failure to obtain zircon separates from erupted basalts in an attempt to solve this problem geochemical analyses and shrimp zircon u pb dating have been carried out on rare felsic ignimbrite in the uppermost of the emeishan lava succession the xuanwei formation which immediately overlies the emeishan basalts and a clay tuff at the middle late permian boundary at the chaotian section clastic rocks of the lowermost xuanwei formation group 1 in eastern emeishan large igneous province lip have a geochemical affinity to the emeishan felsic volcanic rocks whereas the overlying sediments group 2 are compositionally more akin to mafic components of the emeishan traps this is the reverse of volcanic sequence of the central emeishan lip where the felsic extrusives sit above predominant mafic rocks it is likely that the clastic rocks are water transported sediments resulting from erosion of the volcanic rocks in the center of the emeishan lip this interpretation is further supported by the general agreement between the age of the lowermost xuanwei formation 257 4 ma 260 5 ma and that of the silicic ignimbrite 263 4 ma and the clay tuff at the middle late permian boundary at chaotian 260 5 ma these ages interpreted as the termination age of the emeishan volcanism are indistinguishable within error from the middle late permian boundary age 260 4 0 4 ma and the main stage 259 262 3 ma of the emeishan volcanism inferred from dating of mafic and alkaline intrusions in the emeishan lip all these suggest that the emplacement of the emeishan volcanism took place over a very short interval moreover the temporal link and geochemical analyses suggest that the chaotian clay at the middle late permian boundary was genetically related to the emeishan silicic volcanism this together with the fact at that both the emeishan basalts and the chaotian clay rest on the maokou formation leads us to infer that the emeishan basalt was emplaced at the middle late permian boundary in this sense the emeishan volcanism can be regarded as a boundary event and its age is presumed at 260 ma although more precise dating is required both stratigraphic correlation and chronologic data presented in this paper lend supports to the notion that the emeishan volcanism was one of likely causes of the end guadalupian mass extinction

syn tectonic sedimentation in a neogene strike slip basin containing a stacked gilbert type delta se spain abstract the pliocene sedimentation in the cerro blanco ei barranquete subbasin cbb subbasin that forms part of the larger almeria nijar carboneras basin anc basin is controlled by a releasing overstep and a restraining zone in the ne trending serrata strike slip fault zone the sedimentary development of this subbasin can be considered in three stages of a fault kinematic model during stage i a wave influenced shoaling zone was present in front of an emergent serrata cape to the ne with a basin to the sw and w uplift of the shoaling zone in a restraining n080e trending cerro blanco fault zone cb fault zone is evidenced by the following syn tectonic sedimentary phenomena a a rotational unconformity towards the nw b four deepening pulses in the shallow water zone c massflow deposits originating from a near coastal zone possibly triggered by tectonic pulses during stage ii the uplifted zone became increasingly shallow and finally emerged quartz pebbles in the sediments that indicate a land connection between the serrata cape and the metamorphic basement in the north differentiate this stage from the previous one prograding shoreline deposits marked the outbuilding of the serrata cape towards the sw an episodically subsiding zone due to a releasing overstep between the sinistral n040e trending nw serrata boundary fault nwsb fault and b fault during stage ila is indicated by a southwestward outbuilding fandelta during this stage there was only one depocentre during stage ilb the depocentre of the subsiding zone split up this shifting of depocentres is explained according to the releasing overstep model by an increase of the overlap between the nwsb fault and the b fault during stage iii the cbb subbasin became continental and was inverted as demonstrated by its present day relief the area was severely faulted by n040e trending r and y shears on a metre scale which led to an estimated cumulative sinistral displacement of 2 km since fandelta deposition the present day activity of the nwsb fault is shown by sinistrally deflected stream courses and pressure ridges

depositional environment sequence stratigraphy and geochemistry of lower cretaceous carbonates fahliyan formation south west iran abstract the fahliyan formation is a carbonate sequence of lower cretaceous berriasian hauterivian age and was deposited in the zagros sedimentary basin iran in this investigation the fahliyan formation at the type section and in the subsurface has been studied facies analysis and petrographic studies led to the recognition of 10 microfacies that were deposited in three facies belts lagoon shoal and open marine the observed facies patterns indicate a carbonate rimmed shelf depositional environment based on field observations microfacies analysis and sequence stratigraphic concepts two third order sequences in the type section and three third order sequences in the subsurface section were identified the transgressive deposits display a predominance of deep subtidal facies while highstand deposits show shallow subtidal facies some petrographic evidence such as an abundance of aragonite skeletal and non skeletal components shows that this formation was deposited in a sub tropical environment with original aragonite mineralogy geochemical evidence such as high sr na ratios also support original aragonite mineralogy 18o and 13c values suggests that alteration occurred during burial diagenesis in a closed system with low water rock interaction palaeotemperature calculation based on the heaviest oxygen isotope value in micritic samples of the fahliyan limestone shows that ambient water temperature was around 24 c during the deposition of this formation

facies analysis and sea level change at the guadalupian lopingian global stratotype laibin south china and its bearing on the end guadalupian mass extinction abstract the guadalupian lopingian boundary stratotype at penglaitan and the nearby tieqiao section near laibin south china record a series of major environmental changes within the jiangnan basin during a mid permian biotic crisis the sequence stratigraphic petrographic and palaeontological record of these sections has been studied and the associated strontium isotopic fluctuations have been assayed mass extinction of fusulinid foraminifers is most clearly associated in time with onset of volcanism and a relative sea level fall that led to the establishment of mid ramp conditions laibin limestone in settings that were previously dominated by radiolarian mudstones the regression also coincides with a low point of 87 sr 86 sr ratios the lowstand deposits contain mafic scoriaceous grains that record pyroclastic volcanism probably centred in the emeishan flood basalt province 800 km to the west of laibin thus unusually violent eruptions associated with flood basalts in this province may have contributed to the environmental stresses responsible for the extinction event subsequent environmental changes included transgression spread of dysoxic waters indicated by populations of small pyrite framboids and a major negative c isotope excursion all these phenomena have been previously related to the end guadalupian extinction but they in fact post date the crisis because a post extinction fauna of foraminifers is encountered at this time

evolution of a plume influenced source to sink system an example from the coupled central emeishan large igneous province and adjacent western yangtze cratonic basin in the late permian sw china abstract source to sink paleogeography in a time constrained sequence stratigraphic framework has been reconstructed for the non marine to marine transitional lopingian strata late permian in the western yangtze cratonic basin wycb and the adjacent inner zone of the emeishan large igneous province elip in order to reveal the evolution of a mantle plume influenced cratonic basin the lopingian coal bearing strata can be subdivided into seventeen 4th order sequences and three 3rd order composite sequences representing 6 76 myr paleogeographic reconstructions of the wycb demonstrate the existence of n s trending terrestrial transitional and marine facies belts distributed west to east away from the central elip geomorphological analysis indicates that the western boundary of the source area coincided with the major axis of the uplifted central elip based on sediment flux estimates and modeling bqart model relief of the central elip increased from near sea level in the earliest late permian and reached equilibrium at about 200 m in the latest permian sediment volume backfilling analysis indicates that total tectonic uplift of the central elip in the late permian was more than 500 m evolution of the coupled central elip and wycb can be subdivided into three stages pre eruptive uplift stage pre and syn eruptive subsidence stage and syn and post eruptive uplift stage post eruptive basin filling was controlled by sediment supply that was related to tectonic uplift drainage topography and climate change and basin accommodation that was related to sea level fluctuations and plume induced syn sedimentary tectonics

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

sedimentation and lithofacies paleogeography in southwestern china before and after the emeishan flood volcanism new insights into surface response to mantle plume activity abstract investigations into permian sedimentation and reconstruction of paleogeography in sw china are aimed at characterizing sedimentary responses to the emeishan mantle plume in addition to erosional features on the sediments underlying the uplifted emeishan basalts unusual depositions of permian age are also present in the emeishan large igneous province lip specifically carbonate gravity flows and submarine incised canyon fillings were developed in the western margin of the postulated uplifted area and rifting trenches were developed along the eastern margin alluvial fan deposits occur at the boundary between the inner and intermediate zones these depositions all rest on the maokou formation and are in turn covered by the emeishan basalts implying synchronism between crustal uplift and depositional events these deposits and the associated extension and normal faulting along the margin of and within the lip represent sedimentary features resulting from dynamic behavior of mantle plume com

sedimentary evidence for a rapid kilometer scale crustal doming prior to the eruption of the emeishan flood basalts biostratigraphic and sedimentologic investigations in 67 sections have been carried out for the middle permian maokou formation that immediately underlies the emeishan flood basalts in southwest china the results suggest a domal crustal thinning before the emplacement of the emeishan large igneous province variably thinned carbonates in the maokou formation are capped by a subaerial unconformity which is generally manifested by karst paleotopography paleoweathering zone or locally by relict gravels and basal conglomerates provenance analysis indicates that these gravels and conglomerates were mainly derived from the uppermost maokou formation therefore the stratigraphic thinning likely resulted from differential erosion due to regional uplift iso thickness contours of the maokou formation delineate a subcircular uplifted area in accordance with the crustal doming caused by a starting mantle plume as predicted by experimental and numerical modeling the duration of this uplift is estimated to be less than 3 myr and the magnitude of uplift is greater than 1000 m the sedimentary records therefore provide independent supporting evidence for the mantle plume initiation model for the generation of the emeishan flood basalts

quaternary cave levels in peninsular florida abstract the hypothesis that caves in the florida peninsula are tied to quaternary sea levels was proposed by hydrogeologists without data some 40 years ago the hypothesis is a version of glacial control of cave levels which is the logical combination of the water table theory of speleogenesis and the concept that base level positions the water table at the usa type example of glacial control of cave levels mammoth cave in the paleozoic rocks of kentucky the intermediary is base level determined by rivers by hypothesis the intermediary for florida is glacioeustatic sea level this paper presents elevation data that supports this hypothesis recent cave surveys in the air filled caves and spot elevations from archived maps reveal prominent levels of passages centered at 5 12 21 and 30 m above sea level over broad areas they do not follow the large scale structure of the floridan aquifer instead they align with nearby coastal marine terraces identified as modal peaks on frequency plots from various topographic data bases levels matching with the three highest terraces wicomico penholoway and talbott are particularly clear lower levels if they accord with sea level stands are likely composites data from cavities encountered in drilled wells e g bit drops and spot elevations from archived underwater cave maps demonstrate passage levels at depths of 15 30 70 and 90 120 m below the modern water table the depths below water table are similar to the depths below sea level of distant submerged terraces and paleoshoreline features identified using multibeam bathymetric data in the gulf of mexico the cave bit drop and terrace data are all consistent with the concept that quaternary sea level is the fundamental control on the cave scale porosity within the floridan aquifer this conclusion does not rule out the possibility that lithologically favored positions paleokarst features and confining units and mixing zones are also involved in the location of caves levels in this near coastal environment

genetically related alluvial deposits across active fault zones an example of alluvial fan terrace correlation from the upper quaternary of the southern po basin italy integrated studies of alluvial fan systems and related intramontane valley deposits provide potentially useful tools for understanding the character of alluvial sedimentation and its control in fault controlled piedmont zones an example is reported from the uppermost quaternary alluvial deposits of the northern apennines and the southern margin of the po basin a distinctive cyclicity characterizes both the outcropping and the buried units in the study area in intramontane valleys individual cycles consist of regular alternations of sections displaying high and low terrace preservation in the subsurface a rhythmic alternation of coarse grained bodies and laterally extensive pelitic horizons occurs at various scales and represents the basic cyclic motif of the depositional system the correlation between the terrace sequences and the depositional cycles in the subsurface allows the differentiation of distinct sequences with a characteristic internal architecture in the lower part of sequences poorly preserved terrace deposits are laterally correlatable with alluvial fan gravel bodies whereas highly preserved terrace deposits are correlated laterally with predominantly floodplain sediments in the upper part of sequences reliable correlation lines have been constructed using 14c dating thrust tectonics and climate exerted a major control on sequence development deep valley excavation with subsequent low terrace preservation occurred in response to relief rejuvenation during successive thrusting events on the other hand decreasing erosion related to periods of minor tectonic activity led to terrace preservation in the intramontane valleys the coeval episodes of alluvial fan growth and abandonment recorded at the basin margin are interpreted to reflect changes in the efficiency of the drainage system due to variations of tectonic uplift in the adjacent areas alternating phases of deglaciation and renewed glaciation however are inferred to have played a major role in controlling the amount and type of sediment delivered to the alluvial fan complexes

reinterpretation of middle cambrian stratigraphy of the rifted western laurentian margin burgess shale formation and contiguous units sauk ii megasequence rocky mountains canada abstract until recently research on the renowned fossil animals of the burgess shale has advanced to a greater degree than an understanding of the rocks in which they are found studies addressing lithostratigraphy and hydrothermal petrography of the so called inner carbonate belt and adjacent chancellor group however have begun to re evaluate long standing hypotheses on the middle cambrian of western canada tectonic activity along the kicking horse rim buried remnants of neoproterozoic rifting during the cambrian period had more influence on local sedimentation than previously thought notably large scale collapse of the cathedral carbonate platform margin at 509 ma bp is evidence of reactivated basement faults these failures produced listric megatruncation surfaces having near vertical escarpments 150 m in height where they terminate against the platform the majority of what have been interpreted as shed olistoliths from the cathedral platform margin is herein shown instead to be carbonate mud mounds these grew in situ along the face of the cathedral escarpment and are associated with fossiliferous intervals in overlying basinal mudstones at three distinct stratigraphic horizons two within the burgess shale during the delamaran and marjuman stages the mounds nucleated where deep seated normal faults intersected the seafloor building primarily during periods of relative sea level transgression mound growth is associated with syndepositional exhalative activity inferred from stratigraphic relations sedimentology and geochemistry the new name monarch formation is proposed for the initial post collapse beds and mounds deposited against the cathedral escarpment early glossopleura zone the variably defined term takakkaw tongue is thereby confined to pre collapse slope deposits coeval to and correlative with the cathedral formation

pre eruptive uplift in the emeishan in their correspondence he and colleagues question our conclusion of little or no uplift preceding emeishan volcanism that we reported in our letter1 debate concerns the nature of the contact between the maokou limestone and emeishan volcanics the depositional environment and volumetric significance of mafic hydromagmatic deposits mhds and evidence for symmetrical domal thinning mhds in the daqiao section are separated from the maokou limestone by 100 m of subaerial basaltic lavas but elsewhere mhds previously interpreted as basal conglomerates2 3 directly overlie the maokou2 3 mhds thus feature strongly in basal sections of the emeishan lava succession as also recently shown4 elsewhere in the emeishan an irregular surface at the top of the maokou limestone has been interpreted as an erosional unconformity2 3 but clastic deposits presented as evidence of this erosion2 3 are mhds produced by explosive magma water interaction1 a clear demonstration that this irregular top surface is an erosional truncation of limestone reef facies slope rim flat lagoonal is currently lacking but is critical because reefs and carbonate platforms show considerable natural relief of tens of metres the persistent hot wet climate since the oligocene has produced well developed weathering profiles on exposed palaeozoic marine sedimentary sequences5 but weathering and karst relief of the uppermost maokou limestone underlying the flood basalts have not been properly documented nor shown to be of middle permian age and immediately preceding emplacement of the large igneous province

giant radiating mafic dyke swarm of the emeishan large igneous province identifying the mantle plume centre in many continental large igneous provinces giant radiating dyke swarms are typically interpreted to result from the arrival of a mantle plume at the base of the lithosphere mafic dyke swarms in the emeishan large igneous province elip have not received much attention prior to this study we show that the geochemical characteristics and geochronological data of the mafic dykes are broadly similar to those of the spatially associated lavas suggesting they were derived from a common parental magma based on the regional geological data and our field observations we mapped the spatial distribution patterns of mafic dyke swarms in the elip and recognized six dyke sub swarms forming an overall radiating dyke swarm and converging in the yongren area yunnan province this location coincides with the maximum pre eruptive domal uplift and is close to the locations of high temperature picrites our study suggests that the yongren area may represent the mantle plume centre during the peak of emeishan magmatism

numerical modelling of a mantle plume the plume head lithosphere interaction in the formation of an oceanic large igneous province abstract the thermomechanical processes associated with formation of large igneous provinces lips remain poorly understood owing to fundamental difficulties in simulating plume lithosphere interactions in current numerical models these models which aim to simulate the rise of mantle plume and the spread of plume head material imply a mechanically over simplified lithosphere and commonly a flat lithosphere zero vertical displacement as the upper boundary condition we propose a new numerical model derived from lithospheric scale models it has a high numerical resolution in the lithospheric domain and explicitly accounts for 1 free upper surface boundary condition 2 elastic plastic ductile lithospheric rheology including surface faulting and 3 vertical strength variations in the lithosphere we study the final stages of plume ascent and we focus on surface and lithospheric evolution and intra plate strain localisations the experiments predict that the first surface elevation occurs in less than 0 2 ma after plume initiation at 400 km depth variation of rheological parameters results in different surface elevations 500 2500 m ascent 2 10 m yr and base plate strain rates 10 12 10 15 s 1 fast 0 2 0 3 m yr plume head flattening starts at the moment when the plume head reaches the base of the lithosphere it leads to large scale extension and deep normal faulting at the centre of the plateau and to strong thermomechanical erosion at its base the erosion is maximal not under the plume centre as was predicted before but in two large bordering zones our study locally is the igneous province of the caribbean plate where the pre existing farallon lithosphere has been affected by the galapagos hotspot activity that generated thermal perturbations and crustal thickening with two main episodes of volcanism and underplating

the guadalupian lopingian boundary mudstones at chaotian sw china are clastic rocks rather than acidic tuffs implication for a temporal coincidence between the end guadalupian mass extinction and the emeishan volcanism abstract previous studies on the temporal link between the end guadalupian mass extinction event and emeishan flood volcanism were mainly based on geochronological and bio and chemostratigraphic correlation techniques wignall et al 2009 the absence of material based hard evidence that directly links the extinction with the emeishan volcanism remains a major obstacle regardless of the indication of coincidence in timing isozaki et al 2007 the emeishan basalts overlie permian platform carbonates that may contain a record of the end guadalupian mass extinction and erosional product of this province this paper presents mineralogy and geochemistry of mudstones from the guadalupian lopingian boundary g lb at chaotian sw china results indicate that these g lb mudstones are not air fall acidic tuff as previously thought but likely represent clastic rocks derived from erosional deposits of the emeishan large igneous province elip mudstones of the lower part group 1 have a geochemical affinity to the emeishan felsic volcanic rocks whereas mudstones of the upper part group 2 are compositionally akin to mafic components of the emeishan traps this chemostratigraphic sequence resembles the xuanwei formation which sits on the emeishan basalts he et al 2007 these data therefore indicate that the lower part of the mudstones at the chaotian g lb section the lowermost part of xuanwei and longtan formations and the emeishan felsic extrusives broadly constitute an isochron horizon throughout the elip and adjacent region suggesting a short duration for the emeishan volcanism a temporal coincidence between emeishan volcanism and the end guadalupian mass extinction are therefore inferred thus providing support for a cause and effect relationship

evidence of coastal seiche excitation by tide generated internal solitary waves coastal seiches at magueyes island puerto rico occur in distinct fortnightly groups with maximum seiche activity following new and full moon by 7 days the size of the fortnightly groups depends upon the amplitude of the preceding spring tide and upon the caribbean surface water temperature temperature records from the upper thermocline on the slope seaward of the shelf edge off magueyes island indicate the arrival of semidiurnal packets of negative internal solitary waves we suggest that these internal waves are generated by tides in the southeastern caribbean sea and that they are responsible for exciting the coastal seiches this hypothesis is supported by the characteristics of coastal seiching at puerto princesa on palawan island in the philippines which indicate excitation by the sulu sea internal waves reported by apel holbrook and tsai 1980

no pre eruptive uplift in the emeishan large igneous province new evidences from its inner zone dali area southwest china abstract the permian emeishan large igneous province elip in southwest china has been considered a typical example of crustal domal uplift caused by mantle plume upwelling prior to the onset of volcanism however this model has been questioned by the discovery of hydromagmatic volcaniclastic deposits formed in a marine environment located near the central elip area the inner zone which is inferred to be the zone of maximum uplift the volcanology of the inner zone has thus far been poorly documented fueling the debate about whether or not pre eruptive uplift occurred prior to plume upwelling understanding the volcanology of this inner zone is therefore critical in constraining the eruption environment of the central elip our work has revealed new volcanological observations in the inner zone dali area which can systematically constrain volcanism and paleoenvironment the basal succession of the sequence is a thick pillow lavas pile with hyaloclastites implying an initial deeper submarine stage of eruptions limestones and submarine fallout tuffs are interbedded with these pillow lavas above that abundant mafic volcaniclastic products developed which contain palagonite rimmed lapilli tuffs base surge deposits and peperites suggesting hydroclastic volcanism in a shallower submarine environment the upper succession of the sequence preserves columnar jointed lava flows and subaerial fallout tuffs reflecting subaerial volcanism after the volcanic center emerged above the sea level these abundant and systematic natures of this evidence suggest that the initial volcanism of the central elip occurred in a deep submarine environment the submarine to subaerial transition is caused by progressive emplacement of voluminous magmatic products infilling the inner zone during the continuous emplacement of elip rather than by crustal doming prior to the onset of volcanisms

volcanism mass extinction and carbon isotope fluctuations in the middle permian of china the 260 million year old emeishan volcanic province of southwest china overlies and is interbedded with middle permian carbonates that contain a record of the guadalupian mass extinction sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations these show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae the temporal coincidence of these two phenomena supports the idea of a cause and effect relationship the crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean atmosphere carbon cycle

reply to comment on paleokarst on the top of the maokou formation further evidence for domal crustal uplift prior to the emeishan flood volcanism by bin he yi gang xu jun peng guan yu ting zhong lithos 119 1 9 2010 we welcome the comments of ukstins peate et al 2011 on our recent paper he et al 2010a which provide us with an opportunity to extend our discussion on paleokarst between themaokou formation and theemeishanbasalts ukstins peate et al 2011 question the existence of karstic surface of the maokou limestone described by he et al 2010a instead theycontend that the earliest emeishanmagmaswereeruptedat or below sea level in the center of the emeishan large igneous province elip rejecting the pre volcanic domal uplift model proposed by he et al 2003 their arguments are largely basedon their interpretations of field observations such as a sedimentary continuity across the guadalupian lopingian boundary g lb in the center of the elip and b the faulted contact between emeishan basalt andmaokou formation however aswewill showbelow wedispute thesefieldobservations and ukstins peate et al s interpretation of the temporal and spatial frameworks of our and others results in this reply we will clarify using specific examples some key aspects of their questions about the paleokarst on the maokou formation and its relationship to plumeinduced uplift in the elip

paleokarst on the top of the maokou formation further evidence for domal crustal uplift prior to the emeishan flood volcanism abstract the 260 ma emeishan large igneous province elip in southwest china has previously been demonstrated to provide compelling evidence for pre volcanic crustal doming in support of the mantle plume hypothesis however this has been questioned by ukstins peate and bryan 2008 by showing hydrothermal magmatic activity at the daqiao section to solve this argument a detailed characterization of the contact between the emeishan basalts and the maokou formation was carried out the contact is shown to be an unconformity which is characterized by paleokarst on top of the maokou formation including paleokarst relief sinkholes caves tower karst and its corresponding rocks such as kaolinite bauxite and ferruginous duricrust and collapsed breccias etc this paleokarst unconformity was in turn covered or infilled by the emeishan basalts and tuffs suggesting that uplift and erosion occurred prior to the eruption of the elip the extent of erosion of the maokou formation indicates the elip can be divided into three roughly concentric zones the inner intermediate and outer zones the paleokarst features on the top of maokou formation vary across the elip in the inner zone a likely sinkhole and an incision valley with 450 m relief in height are found in the intermediate zone various paleokarst landforms such as karst relief sinkholes and tower karsts are well developed some sinkholes that developed in the qixia formation below the maokou formation imply that the paleorelief is more than 350 m in height in the outer zone the paleokarstic surface is a paleo weathering layer with minor karstification and development of caves at 10 50 m this spatial variation of the paleokarst reflects variation of uplift height across the elip the extent of minimal uplift is estimated to be at least 450 m in the inner zone 350 m in the intermediate zone whereas uplift is minor tens 50 m in the outer zone the magnitude and shape of the uplift is roughly consistent with that predicted by mantle plume models the paleokarst was formed after the deposition of the maokou formation and the eruption of the emeishan basalts at the end guadalupian and indicates a short duration of uplift thus this study lends further support to domal uplift prior to the emeishan flood volcanism but also to the mantle plume initiation model for the generation of the elip

miocene unconformities in the central apennines geodynamic significance and sedimentary basin evolution abstract this paper shows the results obtained from an integrated study geology biostratigraphy and geochemistry carried out on the miocene edimentary deposits in central italy in order to define the timing of the sedimentary basin evolution this paper deals also with the causes of the unconformities recorded in these basins in the miocene deposits of the latina valley and the ernici simbruini mts several unconformities which distinguish different stratigraphic sequences have been recognized d 0 d 1 d 2 d 3 and d 4 for each unconformity a general description together with a geodynamical significance is provided in particular d 0 unconformity appears to be related to a regional tectonic event adria europe collision as a consequence the adria lithosphere folded and the area underwent a regional erosive event d 1 d 2 and d 3 unconformities have had a more local tectonic control since they represent the stratigraphic record of the migration of the apennines thrust belt foredeep system d 1 and d 2 unconformities are related to the late tortonian foredeep stage whereas d 3 is linked to the early messinian piggy back stage moreover the d 4 unconformity which took place during the messinian piggy back stage is strictly linked to the sea level drop of the messinian salinity crisis in this paper the genesis and evolution of a late tortonian foreland basin is also stressed latina valley foredeep basin finally taking into account sequence boundaries nannofossil biostratigraphy and geochemistry isotopic data a comparison with the curve of the 3rd order of the relative coastal onlap haq et al 1988 has been attempted in order to distinguish the unconformities controlled either by tectonic or eustatic processes

comment on paleokarst on the top of the maokou formation further evidence for domal crustal uplift prior to the emeishan flood volcanism a department of geoscience 121 trowbridge hall university of iowa iowa city ia 52242 usa b biogeoscience queensland university of technology brisbane queensland 4001 australia c department of earth and environment university of leeds leeds ls2 9jt uk d dougalearth ltd 12 nevilles cross villas durham dh1 4jr uk e department of earth sciences university of hong kong pokfulam road hong kong china

architecture and morphology of the outer segment of a mixed tide and wave dominated incised valley revealed by hr seismic reflection profiling the paleo charente river france abstract we present new single channel high resolution seismic reflection profiles ground truthed by vibrocore data dedicated to the outer segment of an incised valley connected to the charente river french atlantic coast the present day charente is located about 50 km northward of the well known gironde estuary those river mouths are comparable in terms of marine hydrodynamic parameters but strongly differ by their water discharge and catchment area seismic data are processed and interpreted to develop a three dimensional seismic stratigraphic framework for the charente incised valley fill the channel network of the drowned charente valley is evidenced for the first time and shows a seaward distributary pattern which is likely influenced by neotectonic control incision depth and width of the charente and gironde incised valleys are similar supporting the idea that correlation between valley width and modern hydrology is poor the internal geometry of the charente valley fill shows in seismic lines high to middle angle dipping reflectors at the base and a top of sequence with an intervening low angle seismic unit this pattern is associated with a landward migration of the seismic unit depocentres sedimentary facies of the main seismic units suggests an upward and landward shift from estuarine mixed sands and muds to estuary mouth massive sands topped by fine marine sands the described sedimentary and seismic characters and the holocene age of the valley fill near the present day charente river mouth suggest that the drowned charente valley infill mainly corresponds to a single transgressive sequence emplaced during the last sea level rise beyond the local interest the dense seismic grid recorded across the charente drowned valley gives a seismic validation for the model of large valley fill proposed by ashley and sheridan ashley g m sheridan r e 1994 depositional model for valley fills on a passive continental margin in r w dalrymple r j boyd b a zaitlin eds incised valley systems origin and sedimentary sequences sepm soc sediment geol spec publ tulsa vol 51 pp 285 301 we propose that high low high internal reflection pattern succession represents the seismic sandwich in reference to the ashley and sheridan ashley g m sheridan r e 1994 depositional model for valley fills on a passive continental margin in r w dalrymple r j boyd b a zaitlin eds incised valley systems origin and sedimentary sequences sepm soc sediment geol spec publ tulsa vol 51 pp 285 301 sedimentary sandwich such seismic pattern is also recognized in the gironde valley mar geol 175 2001 183

geothermal constraints on emeishan mantle plume magmatism paleotemperature reconstruction of the sichuan basin sw china the middle late permian emeishan large igneous province elip in southwestern china represents a classic example of a mantle plume origin to constrain the thermal regime of the elip and contemporaneous magmatic activity in the northeastern sichuan basin maximum paleotemperature profiles of deep boreholes were reconstructed using vitrinite reflectance ro and apatite fission track data two heating patterns were identified 1 heating of the overlying lithosphere by magma storage regions and or magmatic activity related to the mantle plume which resulted in a relatively strong geothermal field and 2 direct heating of country rock by stock or basalt borehole ro data and reconstructed maximum paleotemperature profiles near the elip exhibit abrupt tectonothermal unconformities between the middle and late permian the profiles in the lower subsections i e pre middle permian exhibited significantly higher gradients than those in the upper subsections distal to the basalt province high paleo geotemperatures hereafter paleotemperatures were inferred despite deformation of the paleogeothermal curve due to deep faults and igneous rocks within the boreholes in contrast ro profiles from boreholes without igneous rocks i e late permian contained no break at the unconformity paleotemperature gradients of the upper and the lower subsections and erosion at the middle late permian unconformity revealed variations in the thermal regime the inferred spatial distribution of the paleothermal regime and the erosion magnitudes record the magmatic and tectonic thermal response to the emeishan mantle plume

re evaluating plume induced uplift in the emeishan large igneous province numerical and fluid dynamic modelling predicts that mantle plumes should generate a broad domal uplift 1 000 km wide 500 to 1 000 m high preceding volcanism in large igneous provinces the emeishan large igneous province southwest china has been offered as the best example of plume induced uplift where kilometre scale pre and syn volcanic relief was interpreted to develop in response to the impingement of a plume head here we document voluminous mafic hydromagmatic deposits and submarine extrusions that formed during the initiation and early stages of the emeishan large igneous province these deposits were previously interpreted to be alluvial fan sediments shed from a pre volcanic domal high the abundance of such deposits consisting of variable proportions of marine limestone and basaltic fragments strongly suggests that the bulk of this province was emplaced at sea level evidence for dynamic pre volcanic uplift as predicted by plume models is lacking and such a lack may be the more general case any positive relief that developed was more likely the result of the formation of a volcanic edifice and rapid accumulation of the volcanic pile thick alluvial fan sediments from the core of the emeishan large igneous province have been considered as critical field evidence in support of plume induced pre volcanic doming and uplift these sediments are now reinterpreted as mafic hydromagmatic deposits emplaced at sea level precluding dynamic pre volcanic uplift as predicted by mantle plume models