multiple dolomitization and later hydrothermal alteration on the upper cambrian lower ordovician carbonates in the northern tarim basin china abstract thick upper cambrian lower ordovician carbonates were deposited on a shallow marine platform in the northern tarim basin which were extensively dolomitized particularly for the upper cambrian carbonates the resulting dolomite rocks are predominantly composed of matrix dolomites with minor cement dolomites based on petrographic textures matrix dolomites consist of very finely to finely crystalline nonplanar a to planar s dolomite md1 finely to medium crystalline planar e s dolomite md2 and finely to coarsely crystalline nonplanar a dolomite md3 minor cement dolomites include finely to medium crystalline planar s e dolomite cd1 and coarsely crystalline nonplanar saddle dolomite cd2 which partially or completely fill dissolution vugs and fractures these cements postdate matrix dolomites but predate later quartz and calcite infills origins of matrix and cement dolomites and other diagenetic minerals are interpreted on the basis of petrography isotopic geochemistry o c and sr and fluid inclusion microthermometry md1 dolomite was initially mediated by microbes and subsequently precipitated from slightly modified brines e g evaporated seawater in near surface to very shallow burial settings whereas md2 dolomite was formed from connate seawater in association with burial dissolution and localized mg concentration or cannibalization in shallow burial conditions md3 dolomite however was likely the result of intense recrystallization or neomorphism upon previously formed dolomites e g md1 or md2 dolomite as the host carbonates were deeply buried and influenced by later hydrothermal fluids subsequent cement dolomite and quartz crystals precipitated from higher temperature hydrothermal fluids which were contributed more or less by the extensive permian large igneous province lip activity in tarim basin as evidenced by less radiogenic sr in the cement and parts of matrix dolomites this extensive abnormal hydrothermal activity could also have resulted in recrystallization or neomorphism on the previous matrix dolomites faults fractures likely acted as important conduit networks which could have channeled the hydrothermal fluids from depths however the basin uplift triggered by the late hercynian orogeny from the late permian would have facilitated downward infiltration of meteoric water and dilution of hydrothermal fluids resulting in precipitation of later calcites in which lighter c and more radiogenic sr components demonstrate such a switch of fluid properties this study provides a useful analogue to understand the complicated dolomitizing processes and later hydrothermal alteration intimately related to the permian lip activity within tarim basin and elsewhere

a revised tsunami source model for the 1707 hoei earthquake and simulation of tsunami inundation of ryujin lake kyushu japan 1 based on many recent findings such as those for geodetic data from japan s geonet nationwide gps network and geological investigations of a tsunami inundated ryujin lake in kyushu we present a revised source rupture model for the great 1707 hoei earthquake that occurred in the nankai trough off southwestern japan the source rupture area of the new hoei earthquake source model extends further to the hyuga nada more than 70 km beyond the currently accepted location at the westernmost end of shikoku numerical simulation of the tsunami using a new source rupture model for the hoei earthquake explains the distribution of the very high tsunami observed along the pacific coast from western shikoku to kyushu more consistently a simulation of the tsunami runup into ryujin lake using the onshore tsunami estimated by the new model demonstrates a tsunami inundation process inflow and outflow speeds affect transport and deposition of sand in the lake and around the channel connecting it to the sea tsunamis from the 684 tenmu 1361 shokei and 1707 hoei earthquakes deposited sand in ryujin lake and around the channel connecting it to the sea but lesser tsunamis from other earthquakes were unable to reach ryujin lake this irregular behavior suggests that in addition to the regular nankai trough earthquake cycle of 100 150 years there is a hyperearthquake cycle of 300 500 years these greater earthquakes produce the largest tsunamis from western shikoku to kyushu

reexamination of the a d 869 jogan earthquake size from tsunami deposit distribution simulated flow depth and velocity the rupture parameters and magnitude of the a d 869 jogan earthquake a predecessor of the 2011 tohoku earthquake were previously estimated by matching tsunami deposit distributions with simulated inundation areas the tsunami inundation associated with the 2011 tohoku earthquake however extended farther inland than the sandy tsunami deposits numerical simulation of the 2011 tsunami indicated that flow depths and velocities were approximately 1 m and 0 6 m s respectively at the most inland sand deposit sites on the ishinomaki and sendai plains while these values depend on the assumed bottom roughness we used these values to compare tsunami deposits and inundation simulation of the 869 jogan earthquake from both uniform slip and 2011 type variable slip fault models the results showed that the rupture length of the 869 jogan earthquake was at least 200 km and its minimum moment magnitude was 8 6

formation of bedding parallel fibrous calcite veins in laminated source rocks of the eocene dongying depression a growth model based on petrographic observations abstract bedding parallel fibrous calcite veins commonly referred to as beefs are widely developed within eocene lacustrine laminated organic rich source rocks in the dongying depression of bohai bay basin east china understanding the formation of this type vein is essential to elucidate the diagenetic evolution and fluid migration in muddy source rocks this study investigates the mechanism s of growth of bedding parallel veins in hydrocarbon source rocks of the es4 upper and the es3 lower units in the dongying depression based on systematic observations of macro and micro scale features both in veins and their wall rocks combined with x ray diffraction and analyses of geochemical indicators the source rocks are heterogeneous in both composition and structure the beefs mainly occur in laminated rocks consisting of organic rich laminae which occur together with horizontally continuous banded lamalginites and rare carbonate rich laminae overall corresponding to high toc low carbonate contents and low maturity average ro 0 57 most beefs are embedded in the neighboring lamalginites of organic rich laminae with low clay mineral contents the beefs are products of diagenesis accompanying burial and both the initial fracture opening and subsequent dilation represent early stages of hydrocarbon generation and expulsion the presence of bedding parallel bituminite veins and the median plane or parting is evidence for horizontally oriented hydrofracturing due to fluid overpressure in turn fluid overpressure reflects the generation and primary migration of hydrocarbon bearing fluids hydrocarbon generation organic matter evolution and clay mineral dehydration illitization of smectite were responsible for the fluid overpressure crystal growth within the beefs was a continuous process with an antitaxial growth direction and there was no growth competition between adjacent fibres these observations indicate that the crystal growth and fracture dilation were synchronous and growth space was limited the force exerted by crystallizing vein fill contributed to the high fluid pressure suggesting that fibrous vein minerals actively promoted further dilation as the veins grew vein dilation accompanied the migration of hydrocarbon bearing fluids evinced by the occurrence of primary hydrocarbon inclusions found in the fibrous calcites therefore the hydrocarbon bearing fluids were present at the time of horizontal fluid flow from the start of fracture opening to the end of the dilation

the petrology and palaeoenvironment of the sortino group miocene of se sicily evidence for periodic emergence the sortino group of carbonates consists of three formations which developed on a shallow marine shelf during tortonian and lower messinian times the two lower formations contain three bioherms and are intercalated with thick volcaniclastic sequences the youngest formation is dominated by shoal water lagoonal and peri tidal carbonates early submarine lithification is well developed within the bioherms and consists of construction by both algae and invertebrates the development of peloidal micrites and isopachous fringe growth superimposed upon these are a series of both meteoric phreatic and vadose textures related to episodic emergence of the bioherms these features include bladed cements showing cathodoluminescence pendent cements brecciation alveolar texture and palaeosols the sicilian strata may be directly correlated with the maltese islands sequence and collectively exhibit the effects of fluctuating mediterranean sea levels at an early stage in the late miocene salinity crisis

relationship between the maximum extent of tsunami sand and the inundation limit of the 2011 tohoku oki tsunami on the sendai plain japan abstract this paper focuses on the relationship between the maximum extent of sandy tsunami deposits and inundation distance of the 2011 tohoku oki tsunami inundation limits of the tohoku oki tsunami were assessed over seven shore normal transects along the sendai coastal plain inundation distances were found to range from 0 6 to 4 0 km at the maximum extent of the tsunami deposit the sand unit ranged in thicknesses from 0 1 to 4 0 cm the maximum limit of the 0 5 cm thick sand layer extended to over 90 of the inundation distance where the inundation distance was less than 2 5 km this observation is consistent with previous studies that examined characteristics of recent tsunami events that had inundation distances of at least 2 km the maximum limit of the 0 5 cm thick sand layer extended to 3 km 57 76 of the inundation distance where the inundation distance was more than 2 5 km our results are important for estimating paleo tsunami inundation distances based on the landward extent of sand deposits and valuable for the assessment of future tsunami risks in other coastal areas in the world which have been devastated by huge tsunamis in the past

crustal deformation and block kinematics in transition from collision to subduction global positioning system measurements in northern taiwan 1995 2005 1 we present global positioning system gps measurements for the period 1995 2005 at 125 campaign surveyed sites in northern taiwan based on elastic rotating block modeling analyses derived from the gps data we describe the transitional tectonics from arc continent luzon chinese collision to the converging ryukyu trench subduction and back arc opening along the chinese continental margin station velocities relative to station s01r in the chinese stable continental margin were estimated from coordinate time series of each station by using the weighted least squares technique we found two distinct deformation patterns in two geological areas which are basically separated by the surface projection of the nw trending boundary of the subducting philippine sea plate across northern taiwan 1 a waning collision area to the west and 2 a transition zone to the east in the waning collision area the horizontal velocity field shows vectors of 0 3 7 3 mm yr toward the nw in the foothills and the hsuehshan range of northwestern taiwan the tectonic blocks represent a significant nw se internal contraction along with a small block rotation rate 3 0 myr the transition zone can be further divided into an outer range and inner range with distinguishing rotation rates and deformation behaviors in the outer range of the transition zone velocities of 1 0 7 8 mm yr from south to north rotating from 008 to 143 is found in the northernmost foothills and the hsuehshan range the tectonic blocks within the outer range are characterized by a coherent rotation low internal strain rate of 0 10 strain yr with an angular velocity of 5 1 myr where the euler pole is located near its southeastern boundary in the inner range of transition zone a larger clockwise rotation from west to east with horizontal velocities of 9 3 41 2 mm yr from 053 to 146 are found in the northernmost central range the tectonic blocks of the inner range reveal a remarkable nw se internal extension with an ultrarapid clockwise rotation 47 3 myr where the euler pole is near the southern boundary of the range close to the collision comer with the colliding luzon arc the trench roll back together with back arc opening are interpreted to be substantially superposed on the arc continent collision induced rotation in the transition zone with particular regard to the inner range of the northeast taiwan mountain belt

sector zoning in calcite cement crystals implications for trace element distributions in carbonates abstract compositional sector zoning in calcite cement crystals from a sedimentary limestone is represented by differences of mg content of over 1300 ppm or 95 and of sr and mn contents of up to 400 ppm or roughly 50 and 80 respectively between crystallographically nonequivalent time synchronous growth sectors 10 1 1 sectors are enriched with both mg and mn relative to 10 1 4 sectors and other sectors show both greater and lesser enrichment this systematic zoning pattern requires effective distribution coefficients for these trace elements to have been different for growth on different faces differential growth rate effects for nonequivalent faces are shown to be unimportant relative to differential growth face element preferences surface crystal structure and differing coordination environments are regarded as the principal factors influencing sector related elemental partitioning differences in calcite and dolomite

tsunami sedimentation associated with the lisbon earthquake of 1 november ad 1755 boca do rio algarve portugal a description is given of a distinctive marine deposit at boca do rio on the algarve coast of portugal it is proposed here that the sediment accumulation was deposited by the tsunami generated by the lisbon earthquake of 1 november ad 1755 the deposit exhibits sedimentary characteristics quite unlike other coastal sediment accumulations that are deposited by more moderate wave regimes these include laterally continuous sand layers chaotic pebble horizons large amounts of gravel sized shell debris and distinctive assemblages of marine microfossils a preliminary attempt is made here to use the empirical field and laboratory data to define more clearly the processes of coastal sedimentation that characterize tsunami runup the use of tsunami sediments as time synchronous marker horizons is also discussed

burial dominated cementation in non tropical carbonates of the oligocene te kuiti group new zealand abstract cementation of bryozoan echinoid benthic foraminiferal temperate shelf carbonates of the oligocene te kuiti group north island new zealand occurred mainly during subsurface burial the calcite cements in the limestones are dominated by equant and syntaxial rim spar which typically becomes ferroan given an iron supply and compared to the skeletal material with normal marine 18o values from 2 to 1 more depleted in 18o with depth of burial the 18o composition of bulk cement samples ranging from 1 to 7 these trends reflect the establishment in pore waters during sediment burial of reducing conditions and gradually increasing temperatures 20 50 c respectively the 13c values 0 to 3 of the cements remain the same as the host marine shells suggesting the source of carbon in the cements was simply redistributed marine carbonate derived from shell dissolution two gradational burial diagenetic environments influenced by marine derived porewaters are arbitrarily distinguished shallow burial phase and moderate burial phase during the shallow burial phase down to 500 600 m sub bottom depth the carbonates lost at least 25 of their original porosity by mechanical compaction and were selectively cemented by non ferroan or usually ferroan variably luminescent slightly 18o depleted sparry calcite cement 18o 2 to 4 mainly as syntaxial rims about echinoid grains these shallow burial cements form less than about 10 of total cement in the majority of the limestones and their source was probably mainly mild intergranular dissolution of calcitic skeletal fragments accompanying the onset of chemical compaction during the moderate burial phase between about 600 and 1100 m sub bottom depth porosity loss continued typically to about 70 of its original value as a result of pressure solution of calcitic bioclasts associated with more advanced stages of chemical compaction this involved development of a wide variety of non sutured and microstylolitic solution seams including both single and composite wispy or continuous bedding parallel types and non parallel reticulate forms the released carbonate was precipitated as ferroan or non ferroan where iron supply was negligible dull luminescent strongly 18o depleted 18o 4 to 7 mainly equant calcite spar cement occluding available pore space in the limestones

numerical models of tsunami sediment transport current understanding and future directions abstract researchers who study tsunami deposits share common ultimate goals of their work which are to better assess the magnitude information of paleotsunamis and to contribute to the assessment of future tsunami risks numerical modeling of tsunami sediment transport is an important piece of interdisciplinary research that fills the gap between geological studies and practical utilization of tsunami deposits forward and inverse numerical models that address tsunami transport of sand and boulders have been developed over the last two decades forward models are capable of delineating the time evolution of tsunami hydrodynamics sediment transport and the resulting morphological changes associated with erosion and deposition inverse models estimate tsunami characteristics such as flow speed and depth from deposits numerical modeling can be used not only to quantify paleotsunamis but also to enhance our understanding of tsunami sedimentology and hydrodynamics to make progress towards the ultimate goal of improved tsunami risk assessment development of an in depth mutual understanding between modelers and geologists of the advantages limitations and uncertainties in both numerical modeling and geological records is an important challenge

sims oxygen isotopes indicate phanerozoic fluids permeated a precambrian gold deposit abstract the reef deposit is an anomalous au cu occurrence in the paleoproterozoic terranes of northern wisconsin better known as host to significant cu zn volcanogenic massive sulfide vms deposits previous work using lead isotopes and fluid inclusions has identified a protracted development of the mineralization from initial formation as the root zone veins of a vms deposit during the penokean orogeny 1 9 1 8 ga with the most recent mineralization remobilization activity associated with late paleozoic mississippi valley type mvt fluid flow haroldson et al 2018a 2018b here we use the oxygen isotope history of the reef deposit to verify and further examine the deposit s protracted development laser fluorination oxygen isotope measurements of primary mineralized quartz veins range in 18o from 6 8 to 10 0 vsmow and a trend is observed of increasing 18o values of parallel vein zones along a 400 m traverse from northwest to southeast likely from a temperature gradient during initial formation temperature estimates for a vms deposit setting 230 to 400 c are consistent with a hydrothermally shifted formation fluid using seawater 18o estimates during the penokean orogeny and evolving to higher 18o by incorporation of magmatic fluids or interaction with local crust in situ oxygen isotope measurement by secondary ion mass spectrometer sims of cross cutting quartz and carbonate range in 18o from 19 4 to 28 4 for quartz 25 3 to 28 1 for dolomite and 9 6 to 29 3 vsmow for calcite high 18o values 19 are measured in a crustiform textured quartz stockwork microveinlet in dolomite observed in late carbonate microveinlets and calcite in settings associated with the late quartz and dolomite and a separate calcite only setting directly linked with gold mineralization remobilization

massive vein filling gas hydrate relation to ongoing gas migration from the deep subsurface in the gulf of mexico abstract a gas hydrate mound that contains massive vein filling structure ii gas hydrate occurs on the upper continental slope 540 m water depth of the gulf of mexico southwest of the mississippi delta the mound is located in the green canyon gc block 185 adjacent to jolliet field in gc 184 jolliet field contains oil and gas that filled fault traps caused by salt deformation during late pleistocene holocene time in contrast to reservoir oil in jolliet field which shows bacterial oxidation effects the c 1 c 5 reservoir gas is unaltered by bacterial oxidation disassociated gas is assumed to have recently entered from the subsurface hydrocarbon system vertical migration of gas along faults is ongoing manifested on the sea floor by gas vents gas hydrate complex chemosynthetic communities and by a large gas plume that extends from the vents to the sea surface the isotopic properties of c 1 c 5 hydrocarbons from reservoirs gas vents and gas hydrate correlate closely although outcropping gas hydrate is transiently stable because of variations in seawater temperature the bulk of buried gas hydrate at gc 185 is stable and perhaps increasing in volume because of the copious gas flux the massive accumulation of gas hydrate at the gc 185 site is attributed to the gas that has recently entered the vents largely from jolliet field and to the synchronous activation of fault conduits allowing gas migration to the sea floor synchronous late gas charge and faulting could also explain the wide distribution of gas hydrate across the upper gulf slope

geological evidence and sediment transport modelling for the 1946 and 1960 tsunamis in shinmachi hilo hawaii abstract the japanese community of shinmachi established on low lying land between downtown hilo and waiakea hawaii was obliterated by the 1946 aleutian tsunami but was rebuilt only to be destroyed again by the 1960 chilean tsunami the aim of this study was to find out if any geological evidence of these well documented events had been preserved in the sedimentary record in wailoa river state park which replaced shinmachi after the 1960 tsunami this was achieved by collecting cores in the park and performing sedimentological chronological and geochemical analyses the latter also processed by principal component analysis sediment transport modelling was carried out for both tsunamis to infer the source of the sediment and areas of deposition on land the field survey revealed two distinct units within peat and soil a thin lower unit composed of weathered basalt fragments within mud unit 1 and an upper unit dominated by fine volcanic sand within fine silt exhibiting subtle upward fining and coarsening unit 2 consisting of unit 2a and unit 2b although these two anomalous units only occur on the western shore of waiakea mill pond analysis with an itrax core scanner shows that unit 1 is characterised by high mn fe rb la and ce counts combined with elevated magnetic susceptibility based on its chemical and sedimentological characteristics unit 1 is attributed to a flood event in wailoa river that occurred around 1520 1660 ce most probably as a result of a tropical storm the sharp lower contact of unit 2 coincides with the appearance of arsenic contemporaneous with an increase in ca sr si ti k zr mn fe la and ce in this study as is used as a chronological and source material marker as it is known to have been released into wailoa river estuary and waiakea mill pond by the canec factory between 1932 and 1963 thus not only the chemical and sedimentological evidence but also sediment transport modelling corroborating the historical record suggest that unit 2a was deposited by the 1946 tsunami and the sediment most likely originated from wailoa river estuary beach and nearshore seafloor the upper part of this unit unit 2b is believed to have been deposited by the 1960 tsunami as suggested by sediment transport modelling although limited accommodation space is likely to have resulted in the thin deposit 3 cm thickness present at that site limited accommodation space on the island of hawaii has led to only rare locations where tsunami deposits are preserved despite the repeated occurrence of tsunamis affecting the island

the potential benefits to the basin modeling enterprise of modularization and incorporating organic and inorganic chemical change mineral and hydrocarbon resources in basins are produced by fluid movements whose nature is not fully understood flow models in realistically defined basins that predict chemical change are needed to make progress but these models will be difficult to develop and keep vital two simple examples are given to illustrate what is required and the challenges to basin modeling are then outlined it is argued that the best strategy is to modularize existing physical and chemical codes and place as many of these modules as possible in the public domain this will keep the modeling enterprise open to the new entry and continuing invigoration

tsunami deposits and recurrence on a typhoon prone coast of northern taiwan from the last millennium abstract widely known for its hazardous history taiwan holds valuable records of nw pacific tsunamis and typhoons despite the similarity between tsunami and typhoon deposits historical accounts enabled the identification of the 1867 tsunami deposit on the northern coast through matching with the record setting inundation however the identification of prehistoric tsunami deposits has been hindered by severe sediment reworking and post depositional changes produced by the typhoon prone tropical and humid climate in this study we investigated the upper holocene facies and their sediment sources and radiocarbon ages on distal floodplains and rocky backshores of the northern coast where sediment reworking is less intense four decimetre thick gravelly layers were identified intercalated with fluvial mud and colluvium the gravelly layers are composed of beach derived quartz rich sand and rounded gravels of the sedimentary basement rocks longshore drift andesite and stranded pumice the remarkable layer thickness gravel size and quartz richness were determined to have endured post depositional changes the event layers are sharp based matrix supported and poorly sorted and have recorded scouring sediment entrainment and rapid fallout of suspension rich turbulent flows that probably originated with tsunamis the event layers occur 0 5 0 8 km inland and 3 11 5 m above sea level matching the 1867 tsunami inundation and wave height respectively radiocarbon dating tied the event layers to the 1867 tsunami and three prehistoric events that occurred in the periods 1545 to 1810 1293 to 1414 and 1090 to 1235 representing a recurrence interval of 83 436 years over the last millennium

burial dolomitization and porosity development in a mixed carbonate clastic sequence an example from the bowland basin northern england widespread dolomitization and leaching occur in the asbian to brigantian dinantian sequence of the bowland basin within this mudrock dominated succession dolomite is developed in calcarenites and limestone breccia conglomerates deposited in a carbonate slope environment pendleside limestone and also within graded quartz wackes deposited by density currents in a generally starved basin environment pendleside sandstone the dolomitized intervals range in thickness from less than one metre to several tens of metres and have a stratabound nature all stages of calcite cement pre date dolomitization and calcite veins are dolomitized dolomite crystals replace neomorphic spar and may also contain insoluble residues that were concentrated along stylolites thus dolomitization was a late stage process within the carbonate diagenetic sequence a late stage diagenetic origin is also indicated within the sandstones with dolomite post dating the development of quartz overgrowths six main textural styles of dolomite are observed 1 scattered 2 mosaic 3 subhedral to euhedral rhombic 4 microcrystalline 5 single crystal and 6 saddle the style of dolomite developed is dependent on the host rock mineralogy on whether it is space filling or replacive and also on temperature chemically the dolomite varies from near stoichiometric compositions to ankeritic varieties containing up to 20 mole feco3 generally the dolomites have isotopic compositions depleted in 18o compared to the host limestone with similar or lighter 13c values initial dolomite was of the scattered type but with progressive replacement of the host a mosaic dolostone with a sucrosic texture was produced there was a general increase in the fe and mn content and reduction in 18o ratio of the crystals during dolomitization leaching is restricted to partly dolomitized horizons where calcite feldspars micas clays and to some extent dolomite have been leached this has produced biomouldic and vuggy secondary porosity within the carbonates whereas in the sandstones honeycombed corroded and floating grains associated with oversized pores occur porosity within both carbonates and sandstones is reduced by ferroan dolomite ankerite cements field petrographic and chemical characteristics indicate that dolomitizing solutions were predominantly derived from the enclosing mudrocks bowland shales during intermediate deep burial fluid migration out of the mudrocks would have been sided by dehydration reactions and overpressure the fluids migrating along the most permeable horizons the coarse grained carbonates and sandstones that are now dolomitized and contain secondary porosity

video cathodoluminescence microscopy of diagenetic cements and its applications abstract diagenetic studies of sedimentary rocks using cold cathodoluminescence cl microscopy have been severely limited because of the very low intensity of visible luminescent emissions which required long photographic exposure times and because of the difficulty in obtaining quantitative data from cl observations the solution to this problem is to fit the microscope with a high sensitivity digital colour video camera linked to a computer with image enhancement and image analysis software the new technique described in this paper produces digital cl images of consistent high quality both quickly and cheaply controls the capture and editing of cl images to reveal detailed textural information even from minerals exhibiting low level luminescence such as quartz acquires quantitative information on pore systems and the abundance of cement zones from cl images examples are presented to demonstrate the high quality of images produced in this way and the range of uses to which the new technique can be applied the ability to image exactly the same field of view in both plane polarised light and cl is a particular advantage image analysis techniques have been developed to give a statistical characterisation of both pore systems and cement phases that infill them the abundance of contrasting cement zones seen in cl can be measured and the abundance of cement phases can be mapped across a reservoir the history of porosity occlusion can be reconstructed quantitatively and integrated with burial history and hydrocarbon migration porosity can be measured accurately and since the technique obtains data on pore geometry as well as abundance the pore system can be characterised by pore size distributions and pseudo capillary pressure curves this also opens the possibility of estimating permeability from thin sections

petrography and geochemistry of the magnesites and dolostones of the ediacaran ibor group 635 to 542 ma western spain evidences of their hydrothermal origin the ediacaran deposits between 635 and 542 ma of the central zone of the iberian massif consist of alternating siliciclastic and carbonate beds these carbonates are dolostones and magnesites which are interpreted to have been formed by the replacement of primary peritidal limestones through petrographic and geochemical analyses we recognize different types of dolomites d1 to d4 and magnesites m1 and m2 despite distinct petrographic features of the four types of dolomite their oxygen and carbon isotopes overlap with 18o values ranging from 15 45 to 17 51 smow and 13c from 0 13 to 3 21 pdb sr isotope values for d1 and d2 range from 0 7028 to 0 7091 magnesites m1 and m2 show oxygen values higher than 17 87 0 and 13c values show the same variability as for the dolomites d3 and d4 oxygen isotope values are between 18 91 and 19 61 and the carbon isotope values range are similar to the other diagenetic phases sr isotope values for the magnesites and late dolomites d3 and d4 are 0 7095 to 0 7104 being higher than those of the d1 and d2 dolomites d1 is a relatively early dolomite phase formed by the replacement of fine grained peritidal limestones the coarser crystal size of d2 which shows similar geochemical features as d1 suggests formation by dolomitization of coarser grained limestones the replacement of d1 and d2 by m1 and m2 advanced along stylolites fractures and bedding planes this replacement is interpreted to have occurred by hydrothermal fluids which is suggested by the presence of talc and forsterite d3 a coarse dolomite completely destroyed any previous texture and d4 dolomite cement post dates magnesite formation interactions of hydrothermal fluids with the prior carbonates reset the oxygen isotopes of the earlier dolomite the study of these magnesites and related dolostones may offer new insights into the model of formation of sparry magnesites hosted by mixed siliciclastic carbonate platform deposits the establishment of the factors and mechanism that control the diagenetic evolution of these carbonates has a great importance in order to understand and predicts porosity and permeability variations of rocks formed under similar geological conditions

sedimentary features observed in the tsunami deposits at rikuzentakata city abstract the march 11 2011 tohoku oki tsunami triggered by an earthquake off the east coast of northeastern honshu island tohoku region japan deposited large amounts of sediment on land including the sendai plain and sanriku coast this study reports on the characteristics of the tsunami deposits in rikuzentakata city southeastern iwate prefecture northeastern japan a field survey identified the inundation pattern of the tsunami in this region and the facies model of the tsunami deposits at the bay head deltas of estuarine systems the tsunami deposits in rikuzentakata city generally consist of one to four units that represent a discrete runup or backwash flow each unit is characterized by initial inverse grading and successive normal grading that correspond to the accelerating and decelerating stages of the flow respectively an internal erosional surface often developed between the inverse graded and normal graded units it corresponds to the maximum shear velocity of the flow and truncates the underlying inverse graded unit in the case of the runup unit silty fine grained drapes overlay the graded sandy interval a correlation of the sedimentary structures and grain fabric analysis revealed that the tohoku oki tsunami inundated rikuzentakata city at least twice and that the flow velocity exceeded 2 4 m s paleontological analysis of the sediment and kriging estimation of the total volume of the tsunami deposit implied that the sediments were sourced not only from eroded beach sands but also from the seafloor of hirota bay or more offshore regions

a coupled fluid inclusion and stable isotope record of paleofluids in the monterey formation california determining the history of fossil hydrologic systems that is recorded in vein minerals can be complicated by heterogeneity in the oxygen and carbon isotope compositions at millimeter and smaller scales several samples of diagenetic dolomite from two location in the miocene monterey formation california have 18o and 13c values that vary over a few millimeters by 28 and 6 5 respectively relative to the pee dee belemnite isotope standard these variations reflect episodic flow and mixing of waters from different sources with distinct diagenetic histories on the other hand isotopic conpositions of dolomite in samples with gradual shifts in isotopic compositions and correlated 18o and 13c values may have been controlled by mass diffusion and thermal conduction between episodic flow events primary fluid inclusion assemblages from samples collected at one location yielded homogenization temperatures of 87 8 3 6 c 2 these temperatures were combined with measured 18o values very nearly collocated in each dolomite sample to show that 18owater values ranged between 0 8 and 2 5 relative to standard mean ocean water the samples from this monterey formation dolomite thus indicate their precipitation from water more enriched in 18o than late miocene and younger seawater and must reflect modification of the 18o values of the involved waters by mineral dehydration reactions prior to dolomite precipitation samples from the other location contain no primary fluid inclusion assemblages and few abrupt shifts in isotopic compositions perhaps reflecting recrystallization small scale variations in isotopic compositions of vein minerals could be interpreted as the result of a changing regional hydrologic pattern but we think such an interpretation for the monterey formation samples would be incorrect instead we infer that these variations provide important information about localized effects on the ancient hydrologic system and that these effects bear on the origins of the paleofluids responsible for the mineral precipitation

stratigraphic evidence for pre 2004 tsunamis in southwestern thailand abstract the 2004 sumatra andaman earthquake and the associated indian ocean tsunami vastly exceeded the size of their predecessors from the previous two centuries or more we sought clues on how often large tsunamis occur by taking 9 shallow cores 0 5 2 0 km inland from the modern shore on a holocene beach ridge plain of phra thong island 125 km north of phuket we tentatively correlated one sand sheet among these cores and found a second sand bed beneath in one of the cores we infer that these deposits represent two pre 2004 tsunamis the island s setting precludes river floods and tends to rule out storms as causes of the sand deposition establishment of the beach ridge plain requires that both the inferred tsunamis occurred after holocene sea levels approached their present position radiocarbon ages of bulk soil samples are consistent with this conclusion though root penetration into soil samples probably makes the ages appear younger one inferred tsunami occurred before ad 1300 and the other occurred before ad 1900 based on the age estimates the tsunamis probably originated along the sunda megathrust from where tsunamis can travel directly to the thailand coast

chemical controls of cathodoluminescence of natural dolomites and calcites new data and review calcites and dolomites from the late precambrian bonahaven formation of scotland exhibit luminescence when mnco3 0 03 wt dolomite or 0 06 wt calcite and feco3 2 2 5 wt dolomite comparison with other published data shows close similarity in the position of fe quenching in dolomite but more variability in the position of mn activation in calcites and dolomites and the onset of fe quenching in calcites these anomalies are thought to relate to chemical controls subsidiary to the dominant factors of fe and mn concentration it is not practical to make a useful comparison between operating conditions of different luminescence instruments because of differences in design and an inability to measure routinely the current actually on the specimen surface

evidence for major environmental perturbation prior to and during the toarcian early jurassic oceanic anoxic event from the lusitanian basin portugal the timing and causal relationships between the pronounced negative c isotope excursion and paleoenvironmental perturbations associated with the toarcian oceanic anoxic event early jurassic remain unclear particularly because biotic crises and carbonate production decrease appear to have been initiated earlier than the main c isotope anomaly here we present a new quantification of late pliensbachian early toarcian calcareous nannofossils abundance and size from the peniche reference section portugal together with o and c isotope records of well preserved brachiopod shells from the same section the brachiopod shell 13c curve parallels that of bulk carbonate and records two pronounced negative isotopic excursions close to the pliensbachian toarcian boundary 2 and during the toarcian oceanic anoxic event 3 5 our results indicate that both c isotope negative excursions were characteristic of benthic and shallow water environments suggesting that these two carbon cycle perturbations affected all epioceanic reservoirs coeval shifts toward lower values of brachiopod oxygen isotope compositions and closely correlated northward migrations of mediterranean ammonite fauna suggest that both events coincided with major rises in seawater temperatures probably as a result of increased co2 levels and enhanced greenhouse conditions co2 induced changes in seawater chemistry likely affected the calcification potential of both neritic and pelagic systems as evidenced by synchronous drops of platform derived carbonate accumulation and drastic reductions in size 3 m of the main pelagic carbonate producer schizosphaerella we suggest that the early toarcian paleoenvironmental crisis occurred in two distinct episodes that were most likely related to two successive phases of intense volcanic degassing in the karoo ferrar province

the control of cathodoluminescence in dolomite by iron and manganese variations in the cathodoluminescent properties of carbonates are usually attributed to differing proportions of manganese mn2 as the most important activator and iron fe2 as the main inhibitor of luminescence interactions between manganese and iron concentrations and the luminescent properties of dolomite are demonstrated by petrographic and chemical analyses of 86 samples of dolomite representing a range of depositional environments and ages cambrian to cretaceous and a wide geographical distribution north america and europe iron and manganese are positively correlated in the dolomites with the former showing a greater range of variation very small amounts of manganese are sufficient to activate the luminescence and as little as 100 ppm mn2 is present in highly luminescing samples the intensity of luminescence is not proportional to the manganese concentration iron begins to quench luminescence as its concentration reaches 10 000 ppm above that level luminescence is rapidly lost and total extinction occurs among samples containing more than 15 000 ppm fe2 regardless of the manganese concentration

cathodoluminescent bimineralic ooids from the pleistocene of the florida continental shelf a bored and encrusted late pleistocene ooid grainstone was recovered from the seafloor at a depth of approximately 40 m on the outer continental shelf of eastern florida ooid cortices are dominantly bimineralic generally consisting of inner layers of radial magnesian calcite and outer layers of tangential aragonite ooid nuclei are dominantly rounded cryptocrystalline grains although quartz grains and a variety of skeletal grains also occur as nuclei ooids are partially cemented by blocky calcite and interparticle porosity is partially filled by micrite radial cortex layers are composed of brightly cathodoluminescent magnesian calcite having a composition of approximately 12 mol mgco3 and 1000 ppm strontium the iron and manganese concentrations in radial cortex layers are generally in the range of 500 1000 ppm and 100 250 ppm respectively tangential cortex layers are composed of noncathodoluminescent aragonite containing approximately 11 500 ppm strontium and less than 0 5 mol mgco3 iron concentrations in tangential cortex layers are generally in the range of 150 400 ppm and manganese concentrations are generally below the detection limit of 100 ppm echinoderm skeletal fragments which are present as accessory grains are composed of brightly cathodoluminescent magnesian calcite some ooid nuclei and the thin outer edges of some blocky calcite cement are cathodoluminescent micrite matrix and the bulk of blocky calcite cement are noncathodoluminescent ooids do not exhibit textural evidence of recrystallization the ooid grainstone underwent an episode of meteoric diagenesis but ooid cortices were not affected by the event we propose a previously unrecognized process by which the magnesian calcite cortex layers underwent diagenetic alteration in oxygen depleted seawater during this diagenesis magnesium was lost and manganese was incorporated without apparent textural alteration and without mineralogical stabilization thus we suggest that cathodoluminescence may result from diagenetic alteration on the sea floor

geochemical characteristics of upper jurassic lower cretaceous platform carbonates in hazine magara gumushane northeast turkey implications for dolomitization and recrystallization1 the upper jurassic lower cretaceous berdiga formation of the eastern pontides turkey represents a carbonate platform succession composed of pervasively dolomitized intra shelf to deep shelf fac

geological records of western pacific tsunamis in northern taiwan ad 1867 and earlier event deposits abstract located in the western circum pacific seismic zone taiwan is an ideal area for recording tsunamis that originate in the tectonically and volcanically active systems of the ryukyu arc okinawa trough and luzon arc however because of taiwan s short historical record there is only credible evidence for one disastrous tsunami which occurred in northern taiwan in ad 1867 to better understand the western pacific tsunamis an upper holocene deposit of a coastal plain inundated by the ad 1867 tsunami was investigated to search for geological evidence of tsunamis based on facies characteristics and sediment composition we identified two sharp based decimetre thick marine quartzose sandy layers that fine upward and landward intercalated with floodplain marsh sand and mud the fluvium are rusty red rich in volcanic clasts and fe and comparable to modern riverine sediments of local andesitic provenance extending 0 8 km inland the marine quartzose sandy layers are light coloured and rich in quartz and si have high ca ti values and are comparable to the modern beach dune sediments of regional siliciclastic provenance radiocarbon dating indicates that the marine sandy layers are correlated with the ad 1867 tsunami and an older event at the boundary between the 17th and 18th centuries both events were probably associated with reported earthquakes involving normal faulting in addition the distribution patterns of the two marine sandy layers are similar suggesting that the inundation distances run ups and flow heights of the two events are comparable this indicates that the disastrous tsunamis were frequent in the area between northern taiwan and the okinawa trough of the western circum pacific seismic zone

paleotsunami evidence on kaua i and numerical modeling of a great aleutian tsunami the hawaiian islands location in the middle of the pacific ocean is threatened by tsunamis from great earthquakes in nearly all directions historical great earthquakes mw 8 5 in the last 100 years have produced large inundations and loss of life in the islands but cannot account for a substantial 600 m3 paleotsunami deposit in the makauwahi sinkhole on the island of kaua i using high resolution bathymetry and topography we model tsunami inundation of the sinkhole caused by an earthquake with a moment magnitude of mw 9 25 located in the eastern aleutians a preponderance of evidence indicates that a giant earthquake in the eastern aleutian islands circa 1425 1665 a d located between the source regions of the 1946 and 1957 great tsunamigenic earthquakes created the paleotsunami deposit in kaua i a tsunami deposit in the aleutians dated circa 1530 1660 a d is consistent with this eastern aleutian source region

hydrocarbon generation migration and venting in a portion of the offshore louisiana gulf of mexico basin the offshore louisiana gulf of mexico is one of the earth s most active margins the erosional debris of an entire continent is depositing there in places at over 2 km ma sediments have accumulated to over 16 km thickness temperatures at the base of this section are hotter than those in a pizza oven 300 c hydrocarbons are maturing brines expelling reservoirs filling hydrates accumulating and gas and oil migrating into the ocean and all this is happening today

holocene indian ocean tsunami history in sri lanka sediment cores from karagan lagoon in southeastern sri lanka retrieved deposits from the a d 2004 indian ocean tsunami and older similar deposits that provide evidence for a tsunami 2417 152 cal calendar yr b p to 2925 98 cal yr b p and for six tsunamis between 4064 128 cal yr b p and 6665 110 cal yr b p a period for which the sediment record appears continuous radiocarbon dating indicates that the recurrence interval is variable ranging from 181 517 yr to 1045 334 yr with a mean recurrence interval of 434 40 yr during the ca 4000 7000 cal yr b p continuous interval assuming that these tsunamis were generated by giant earthquakes along the sumatra andaman subduction zone a reasonable assumption for this far field transoceanic location this record extends the giant earthquake history for the indian ocean region the longest recurrence interval of more than 1000 yr implies that earthquakes along the subduction zone may reach twice the size of the 2004 earthquake

low limit of mn2 activated cathodoluminescence of calcite state of the art in the literature the lower limit for mn2 activated cathodoluminescence cl of calcite is variously reputed to over a very wide range of values above 10 ppm mn our spectroscopic investigations of the cl response in natural calcite reveal that below 10 ppm manganese content mn2 activation is also present using the quantitative high resolution spectral analysis of cl qhrs cl an activation by mn2 in the range of 700 ppb is proved which cannot be determined visually so if not quenched the minimum mn2 content for mn2 activation is one atom in the irradiated calcite crystal lattice volume as the intrinsic background blue luminescence is used to determine non altered biogenic calcite the limit of mn2 activation plays an important role in the interpretation of diagenetic processes our results of spectroscopic analyses require a revision of current opinions about the diagenesis of calcite as revealed by cl investigation

isotopic composition of organic and inorganic carbon from the mesoproterozoic jixian group north china implications for biological and oceanic evolution a b s t r a c t analyses of marine carbon isotope profiles have provided much of our current understanding of the evolution of earth surface environments particularly in the latter portion of the proterozoic eon earlier mesoproterozoic successions however have received comparatively little attention due to the relatively subdued nature of carbon isotope variation in this study we present high resolution isotopic profiles from three sections in the yanshan basin north china craton that combined comprise the entirety of the early mesoproterozoic 1600 1400 ma calymmian period jixian group high resolution profiles of both carbonate and organic carbon provide critical data for global comparison and permit us to better con strain both the pattern and origin of isotopic variation in the mesoproterozoic marine carbonate rocks of the jixian group show generally muted isotopic variation with average values near 0 consistent with previous observations from the early mesoproterozoic data furthermore record an increase in isotopic variation through the succession that is interpreted to reflect a long term decrease in pco2 and conse quently in the isotopic buffering capacity of marine dissolved inorganic carbon dic by contrast the isotopic composition of marine organic matter suggests facies dependent differences in carbon cycling organic carbon compositions suggest a dominance of autotrophic carbon fixation and aerobic decom position in shallow water environments and increased remineralization by anaerobic heterotrophs in deeper water environments correlation between organic carbon composition and depositional environ ment are interpreted to reflect differences in carbon cycling within benthic microbial mats under low oxygen conditions and dynamically maintained stratification of marine waters

numerical modeling of the 2011 tohoku oki tsunami in the offshore and onshore of sendai plain japan abstract this paper examines the results of a numerical modeling of the 2011 tohoku oki earthquake tsunami to investigate its offshore propagation and inundation along a shore normal transect located in the center of the sendai plain the inundation distance flow depth and flow speed were compared with the available data measured during a post tsunami field survey and estimated from the video records the calculated inundation distance reached 4 5 5 5 km from the coastline which is comparable to the actual inundation distance the variation of tsunami heights from 2 4 6 m and flow speeds from 3 4 6 2 m s along the transect is generally consistent with the measured heights and estimated speeds the waveform on the beach showed that the wave train was composed of a high 10 11 m first wave followed by low 4 m waves considering the waveform and the topographic change the erosion of the beach and the sedimentation inland are explained mainly by the first wave in addition the calculated flow speed and friction velocities in the offshore may account for the formation of the possible tsunami deposits which were reported recently by a sea bottom survey the modeling results are generally consistent with the available data and are considered to be useful for understanding the inundation pattern and sedimentation process of the tohoku oki tsunami on the sendai plain

contractional transcurrent rotational and extensional tectonics examples from northern taiwan abstract contraction transcurrent faulting block rotation and even extension are four essential tectonic mechanisms involved in the progressive deformation of arcuate collision belts the neotectonic evolution of the taiwan mountain belt is mainly controlled by the oblique convergence between the eurasian plate and the philippine sea plate as well as the corner shape of the plate boundary based on field observations and tectonic analysis and taking geophysical data and experimental modelling into account we interpret the curved belt of northern taiwan in terms of contractional deformation with compression thrust sheet stacking folding and transcurrent faulting combined with increasing block rotation bookshelf type strike slip faulting and extension as a consequence the formation of the extensional taipei basin the division of conjugate strike slip faulted domains and the variable nature and distribution of paleostresses should not be interpreted in terms of distinct plio quaternary episodes but should reflect a single albeit complicated regional pattern of deformation our study demonstrates that in taiwan contractional extensional and transcurrent tectonics as well as rotations combine together and interact within a single complex framework the crescent shaped mountain belt develops in response to oblique indentation by an asymmetric wedge indenter the distribution nature and relative importance of these deformation modes are a function of the shape of the indenter and the average direction of convergence

process based modeling of tsunami inundation and sediment transport 1 the infrequent and unpredictable nature of tsunamis precludes the use of field experiments to measure the hydrodynamic and sediment transport processes that occur instead these processes are often approximated from laboratory numerical and theoretical studies or inferred from observations of the resultant sediment deposits here delft3d a three dimensional numerical model is used to simulate the inundation and sediment transport of a tsunami similar in magnitude to the 26 december 2004 indian ocean tsunami over one measured and three idealized morphologies the model is first shown to match well the observations taken at kuala meurisi sumatra and then used to examine in detail the processes that occur during the tsunami the model predicts that at a given cross shore location the onshore flow accelerates rapidly to a maximum as the wavefront passes and then gradually decelerates before reversing direction and flowing offshore the onshore flow does not tend to zero everywhere at maximum inundation but instead flow reversal occurs near the shoreline even as the wavefront continues to inundate landward while some sediment is eroded by the passing wavefront the suspension of sandy sediment is dominated by the long duration high velocity backwash that occurs along the beach face and offshore of the shoreline some of the sediment suspended during backwash is advected shoreward by the subsequent wave creating large spatial gradients in the suspended sediment concentrations which may not be in equilibrium with the local hydrodynamics the inundation and transport of sediment during a tsunami can be affected by complexities in the morphological profile and interactions between multiple waves and many of the hydrodynamic and sediment transport processes predicted here are similar to analogous processes previously observed in the swash zone

extensional collapse of the northern taiwan mountain belt as an active collision zone between the luzon arc and the china continental margin the taiwan mountain belt particularly its south central part is undergoing crustal shortening and rapid uplift the northern part of the orogen is however subjected to crustal stretching and rifting as a result of flipping of subduction from the northwest facing luzon arc system to the south facing ryukyu arc system taiwan and its neighboring southern ryukyu used to be part of the rifted china continental margin before the collision started in late miocene time engineered by the northwest movement of the philippine sea plate in the past 5 m y the north south trending luzon arc obliquely overrode the northeast southwest trending continental margin and tectonized it into a collision orogen that progressively enlarged and migrated from northeast to southwest following the southwest propagating collision the north dipping philippine sea plate which was subducting beneath the ryukyu arc also extended westward and caused flipping of subduction in the northern part of the collision orogen in consequence the orogen lost the compressive support by the colliding plates and became subjected to lithospheric stretching induced by the trench suction the collision orogen collapsed as a result of crustal thinning and its central part foundered into a deep submerged basin a whole spectrum of active tectonic scenarios ranging from orogenic buildup by collision to orogenic collapse by rifting and subsidence can be readily observed in the taiwan ryukyu area and provides a vivid example for the process of orogenic collapse

origin of dolostone reservoir rocks smackover formation oxfordian northeastern gulf coast u s a formation of regionally extensive dolostone reservoir rocks in the smackover can be understood despite the possible effects of recrystallization geochemical and petrographic data suggest that dolomitization took place in 1 seawater seepage 2 reflux 3 near surface mixed water 4 shallow burial mixed water and 5 deeper burial environments which overlapped in time and space to form a platform scale dolostone body composed of a complex mixture of dolomites seawater seepage and reflux dolomitization occurred in the near surface penecontemporaneously with deposition of the smackover and overlying haynesville formations dolomitization by seawater seepage occurred within an oolite grainstone sill which separated an intraplatform salt basin from the open sea seawater flowed landward through the sill in response to evaporitic drawdown of brines in the isolated intraplatform basin isolation of the salt basin occurred during the oxfordian when the shoreline retreated from the conecuh embayment dolomite located at the top of the smackover enriched in 18 o suggests additional dolomitization by reflux of hypersaline brines reflux occurred as buckner coastal sabkhas prograded over smackover oolite grainstone shoreface deposits vugs lined with shallow burial calcite and dolomite cements indicate flushing of the smackover grainstone aquifer with fresh water freshwater intrusion probably occurred following sea level lowstands during the late jurassic and early cretaceous leaching in the proximal portion of the freshwater aquifer produced excellent limestone reservoir rocks in the updip smackover dolomitization in the contemporaneous downdip mixed connate freshwater zone formed dolostone reservoir rocks with depleted isotopic compositions consistent with a shallow burial mixed water origin

mixing zone dolomites in the gully oolite lower carboniferous south wales the gully oolite at st lythams glamorgan is extensively dolomitized towards its base the dolomite is non ferroan and is both replacive and void filling in nature 18 o varies from 6 06 0 to 2 96 0 pdb and 13 c from 2 32 0 to 3 55 0 pdb with a marked covariation of 18 o and 13 c dolomitization is believed to have occurred within a mixing zone environment at salinities up to 50 of that of seawater the variation of dolomite isotopic composition versus depth in the sediment is explained in terms of successive upwards migration of the mixing zone and associated multiple phases of dolomitization the tops of these successive mixing zones coincide with evidence of sediment emergence and the presence of dolomite intraclasts implies that dolomitization occurred at shallow depths within the sediment this suggests dolomitization occurred in the absence of an overlying meteoric phreatic lens the high degree of dolomitization at st lythams as opposed to that occurring in modern mixing zones is related to 1 longer duration of the mixing zone environment in the sediment 2 the proximity of the mixing zone to the sediment surface 3 possible chemical differences between carboniferous and modern seawater particularly with respect to pco 2

cathodoluminescence in quaternary carbonate deposits abstract the cathodoluminescent oscillatory and sectoral growth zones common in crystals formed in ancient limestone successions in a variety of putative environments appear to be rare or absent from recent and pleistocene marine carbonate sequences the factors controlling cathodoluminescence and reasons for this disparity are examined the cathodoluminescent zones in the cements of ancient rocks have been interpreted as responses to variations in the redox potential of formative pore waters during crystal growth although similar cathodoluminescent behaviour is recorded from some deposits including travertines and quaternary speleothems formed in what are thought to have been strongly oxidizing environments the apparent absence of cathodoluminescence in the most recent and pleistocene marine deposits that presumably reflect deposition and diagenesis in environments that are also characteristically oxidized therefore seems anomalous the controlling influences on cathodoluminescence are reviewed together with evidence relating to observations of pleistocene marine deposits and likely conditions of formation but where it is present the mechanism s for its development remain elusive

the evolution of allochthonous salt along a megaregional profile across the northern gulf of mexico basin sequential restorations of a north south megaregional cross section across the north central gulf of mexico basin from east central louisiana to the abyssal plain define a dynamic complex history of sedimentation salt flowage and salt evacuation proprietary composite seismic profiles 590 km 33 wells and published depth to basement maps were used to constrain the section in depth thirteen sequential structural restorations incorporating both decompaction and isostatic subsidence thermal and tectonic were then constructed from the late cretaceous to the holocene the restorations highlight and constrain a protracted history of deformation that is primarily controlled by gravity and the progradation of cenozoic sediments over salt early stages of the tectonic history of the northern gulf of mexico basin were related to differential thermal subsidence resulting from early middle jurassic rifting during the cenozoic the evolution of the basin was dominated by the influx of large clastic depocenters which caused the basinward evacuation of autochthonous jurassic salt salt extrusion from the autochthonous layer was accomplished by inclined salt bodies which flowed into salt glaciers or sheets near the sea floor evacuation of allochthonous salt layers provided significant sediment accommodation and unusually thick sedimentary sections were deposited such as the terrebonne trough of southern louisiana 3 7 km of miocene strata salt sheet formation and evacuation occurred progressively basinward through time in response to basinward shifts of major cenozoic sedimentary depocenters as a salt sheet neared complete evacuation the underlying autochthonous salt layer would begin to evacuate providing additional sediment accommodation that caused autochthonous salt flowage basinward and the formation of the next allochthonous salt sheet basinward of the depocenter the area of autochthonous salt progressively decreased through time and currently represents at most 45 of its maximum along this transect the total area of salt through time was more stable with variations of only 30 from its maximum this relationship is a function of lateral salt flow into and out of the plane of section and possible salt dissolution the restorations indicate that very little translation or extension 1 46 occurred at the autochthonous salt level during the evolution of the basin the majority of translation or extension occurred above allochthonous salt sheets 25 and was compensated laterally by salt flow displacements above allochthonous salt sheets were driven by gravitational instabilities caused by the slope gradient

multistage dolomitization in the society cliffs formation northern baffin island northwest territories canada dolostones of the upper proterozoic society cliffs formation on northern baffin island are host to the nanisivik lead zinc sulfide deposits two distinct stages of dolomitization have occurred distinguished by their petrographic cathodoluminescence and isotopic characteristics 1 massive dolomitization of precursor carbonates and 2 late stage cementation sabkha facies of the lower member of the formation and laminated algal stromatolitic to massive dolostones of the upper member are isotopically similar 18o ranges from 1 5 to 6 5 13c from 1 7 to 3 1 pdb and 87sr 86sr averages 0 70761 petrographic and geochemical evidence indicates that these dolostones formed chiefly by seawater thermal convection beneath shale of the overlying victor bay formation although mixing of meteoric and marine water also could have occurred later fracture filling dolomitic cements have consistently lower 18o but 13c is similar to that in the host dolostones microtraverses of single fractures filled wit

reduction effect of tsunami sediment transport by a coastal forest numerical simulation of the 2011 tohoku tsunami on the sendai plain japan abstract we examined the effect of the coastal forest on tsunami sediment movement on the sendai plain japan during the 2011 tohoku tsunami using a numerical simulation of sediment transport to account for the variable roughness coefficient in the coastal forest a composite equivalent roughness coefficient was adopted the simulated mean concentration of suspended sediment wave height flow velocity and inundation limit were significantly reduced by the coastal forest for fine to medium sand the volumes of maximum deposition and erosion were reduced to 57 83 of those in the simulation without the coastal forest these reductions were particularly notable for fine sand the maximum extent and thickness of the sand layer were also reduced the simulated sediment thickness and extent with the coastal forest for finer grain sizes roughly agreed with the observations while the simulated results for coarser sand underestimated the observations the reduction of sediment transport due to the coastal forest suggests that land use conditions and the vegetation environment at the time of a tsunami should be considered when studying historical and paleo tsunamis using the geological evidence

sediment transport due to the 2011 tohoku oki tsunami at sendai results from numerical modeling abstract numerical modeling of sediment transport on the sendai plain in northeast japan which was caused by the 2011 tohoku oki tsunami was performed to investigate why onshore tsunami deposits included small amounts of marine materials and to explain the gap between the maximum inland extent of the recognizable sand layer and the limit of inundation the simulation results generally corresponded with the thicknesses of the deposits observed in the field by previous studies the simulation revealed that the tsunami caused a significant amount of erosion on the beach and in the coastal forest however erosion was significantly limited on the offshore seafloor in addition the bore of the highest tsunami wave offshore limited the amount of suspended sediment due to a steep bathymetric profile of the shoreface and a moderate initial drop in water level prior to the arrival of the bore this resulted in limited suspension and shoreward advection of the sediments and a minor contribution of the seafloor sediments to the onshore tsunami deposit visualization of the onshore sediment transport indicated that the sediment transport was significantly affected by artificial topographic features the flow speed and height varied across the topographic highs and sediments were trapped on the seaward side of these highs in coastal areas the sediment supply was limited due to the presence of engineered dikes along the coast in inland areas embankments of paved roadways caused increased deposition on the seaward sides of the embankments and less deposition on the leeward sides of the embankments although some aspects of the relevant physics were not fully implemented in the model in which uncertainties exist the results may explain the processes and consequences of sedimentation from a tsunami event

time and space distribution of coseismic slip of the 2011 tohoku earthquake as inferred from tsunami waveform data a multiple time window inversion of 53 high sampling tsunami waveforms on ocean bottom pressure global positioning system coastal wave and tide gauges shows a temporal and spatial slip distribution during the 2011 tohoku earthquake the fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface a very large slip approximately 25 m in the deep part off miyagi at a location similar to the previous 869 jogan earthquake model was responsible for the initial rise of tsunami waveforms and the recorded tsunami inundation in the sendai and ishinomaki plains a huge slip up to 69 m occurred in the shallow part near the trench axis 3 min after the rupture initiation this delayed shallow rupture extended for 400 km with more than a 10 m slip at a location similar to the 1896 sanriku tsunami earthquake and was responsible for the peak amplitudes of the tsunami waveforms and the maximum tsunami heights measured on the northern sanriku coast 100 km north of the largest slip the average slip on the entire fault was 9 5 m and the total seismic moment was 4 2 1022 n m m w 9 0 the large horizontal displacement of seafloor slope was responsible for 20 40 of tsunami amplitudes the 2011 deep slip alone could reproduce the distribution of the 869 tsunami deposits indicating that the 869 jogan earthquake source could be similar to the 2011 earthquake at least in the deep plate interface the large tsunami at the fukushima nuclear power station is due to either the combination of a deep and shallow slip or a triggering of a shallow slip by a deep slip which was not accounted for in the previous tsunami hazard assessments online material table of estimated slip for all subfaults at 0 5 min invervals

metamorphic evolution of the late archaean cadillac tectonic zone mcwatters abitibi belt quebec archaean greenstone belts are often cut by major shear zones for example the cadillac tectonic zone ctz of the southern abitibi region in north western quebec at mcwatters the ctz contains slices of metavolcanic units bounded by corridors of highly strained and altered rocks mineral assemblages of the metabasites record the metamorphic evolution of the ctz the mcwatters metabasalts and metagabbros have similar chemistry but different mineral assemblages consisting of variable amounts of actinolite hornblende chlorite albite epidote quartz carbonates titanite biotite rutile magnetite ilmenite and sulphides the different mineral assemblages which coexist in a single tectonic slice can be divided into three types characterized by a presence of hornblende and actinolite b presence of actinolite and epidote and c absence of amphibole and epidote partial replacements indicate that these mineral assemblages are not in equilibrium the hornblende of the least altered and deformed samples of the type a assemblage is a relict of a prograde metamorphic event contemporaneous with the development of the main schistosity the prograde conditions are estimated at p 5 kbar t 475 c with low pf the more altered and deformed samples of the type c assemblage record a later retrograde metamorphic event conditions of the later event are estimated at p 4 kbar t 400 c with higher pf widespread calcite precipitation occurred during a later episode the diversity of the mineral assemblages results from permeability variations along the high strain zones of the ctz

gas washing of oil along a regional transect offshore louisiana abstract gas chromatogram data for 219 oils in a 190 km n s transect offshore louisiana reveal a spatially coherent pattern of compositional change which is caused by gas washing near the louisiana shoreline as much as 91 of the original n alkanes have been removed from the oils the maximum intensity of depletion decreases southward in a nearly regular fashion to nil at the jolliet field 190 km offshore the oils show a parallel change in the maximum carbon number of the removed n alkanes implying that the pressure at which gas washing took place also decreased in the offshore direction the systematic change in maximum extent of depletion crosscuts tectonostratigraphic boundaries as well as oil source provinces models of gas washing suggest that the maximum depth of washing reflects the distribution of deeply buried continuous sands suggesting deep sands may have provided sites for efficient gas oil interaction

source model of the great 2011 tohoku earthquake estimated from tsunami waveforms and crustal deformation data the slip distribution of the 11 march 2011 tohoku earthquake is inferred from tsunami waveforms gps data and seafloor crustal deformation data the major slip region extends all the way to the trench and the large slip area extends 300 km long and 160 km wide the largest slip of 44 m is located up dip of the hypocenter the large slip amount about 41 m ruptured the plate interface near the trench the seismic moment calculated from the estimated slip distribution is 5 5 10 22 n m mw 9 1 the large tsunami due to the 2011 tohoku earthquake is generated from those large slip areas near the trench the additional uplift at the sedimentary wedge as suggested for the 1896 sanriku earthquake may have occurred during the 2011 tohoku earthquake too

tsunami generation by horizontal displacement of ocean bottom tsunami generation by an earthquake is generally modeled by water surface displacement identical to the vertical deformation of ocean bottom due to faulting the effect of horizontal deformation is usually neglected however when the tsunami source is on a steep slope and the horizontal displacement is large relative to the vertical displacement the effect becomes significant we show this for two recent earthquakes which generated much larger tsunamis than expected from seismic waves in the case of the 1994 june 2 java indonesia earthquake the focal mechanism was a very shallow dipping thrust and the source was near a very steep trench slope in the case of the 1994 nov 14 mindoro philippines earthquake strike slip faulting extended from ocean to land perpendicular to the coast line in both cases we found that the horizontal motion of slope had an important contribution to the tsunami generation

massive hydrothermal dolomites in the southwestern cantabrian zone spain and their relation to the late variscan evolution abstract large scale massive burial dolomitization affected upper carboniferous carbonates of the southwestern variscan cantabrian zone spain replacive and void filling dolomites formed and were post dated by calcite cementation the process of dolomitization was due to the circulation of hypersaline and hydrothermal marine derived brines controlled by rock anisotropies the dolomites probably formed in early permian time during post thrusting orocline formation in an extensional setting lithospheric delamination induced increased heat flow and allowed thermal convection of the fluids the dolomites from the cantabrian zone are excellently exposed and represent an interesting outcrop analogue for hydrocarbon reservoirs elsewhere in comparable geotectonic settings of the european variscan orogen large masses of similar dolomites could have formed if mg rich brines were available

slip distribution and seismic moment of the 2010 and 1960 chilean earthquakes inferred from tsunami waveforms and coastal geodetic data the slip distribution and seismic moment of the 2010 and 1960 chilean earthquakes were estimated from tsunami and coastal geodetic data these two earthquakes generated transoceanic tsunamis and the waveforms were recorded around the pacific ocean in addition coseismic coastal uplift and subsidence were measured around the source areas for the 27 february 2010 maule earthquake inversion of the tsunami waveforms recorded at nearby coastal tide gauge and deep ocean assessment and reporting of tsunamis dart stations combined with coastal geodetic data suggest two asperities a northern one beneath the coast of constitucion and a southern one around the arauco peninsula the total fault length is approximately 400 km with seismic moment of 1 7 1022 nm mw 8 8 the offshore dart tsunami waveforms require fault slips beneath the coasts but the exact locations are better estimated by coastal geodetic data the 22 may 1960 earthquake produced very large 30 m slip off valdivia joint inversion of tsunami waveforms at tide gauge stations in south america with coastal geodetic and leveling data shows total fault length of 800 km and seismic moment of 7 2 1022 nm mw 9 2 the seismic moment estimated from tsunami or joint inversion is similar to previous estimates from geodetic data but much smaller than the results from seismic data analysis