eolian deposition in the northeast pacific ocean cenozoic history of atmospheric circulation the mass accumulation rate and grain size distribution of the total eolian component of north pacific pelagic clays have been used to evaluate changes in eolian sedimentation and in the intensity of atmospheric circulation that have occurred during the past 70 m y eolian deposition was relatively low approximately 12 mg cm2 1 000 yr in the late cretaceous and paleocene reflecting an increasingly humid environment a peak in accumulation rates across the paleocene eocene boundary may be the result of episodic volcanism in mexico a sharp decrease in grain size across the paleocene eocene boundary is not readily interpreted fine eolian grain size and the low accumulation rates averaging 8 mg cm2 1 000 yr in the eocene and early oligocene are in agreement with low early tertiary thermal gradients and less vigorous atmospheric circulation large increases in grain size between 37 and 30 m y ago 20 and 10 m y ago and 5 m y ago to the present suggest that atmospheric circulation intensified by a factor of 1 5 1 8 and 1 4 respectively at these times eolian accumulation rates increased from 8 mg cm2 1 000 yr at the eocene oligocene boundary to approximately 25 mg cm2 1 000 yr at the end of the miocene with significant changes at 25 and 13 m y ago increased rates about 25 m y ago probably reflect movement of the core site into the influence of the westerlies and the increase 13 m y ago appears to be a response to steepening thermal gradients and intensifying atmospheric circulation resulting from major expansion of antarctic ice in the mid miocene along with a general increase in global aridity in the late cenozoic an order of magnitude increase in eolian accumulation rates 25 to 226 mg cm2 1 000 yr in pliocene pleistocene time coincides with the onset of northern hemisphere glaciation and consequent climatic deterioration the large increase in accumulation rates in pliocene pleistocene time coincides with a relatively smal increase in the intensity of atmospheric circulation compared to that in oligocene and miocene time suggesting that the increased deposition rates were the result of an increase in global aridity in glacial times rather than a further increase in the vigor of the global wind systems

terreneuvian small shelly faunas of east yunnan south china and their biostratigraphic implications the study discusses the detailed composition of terreneuvian small shelly fossil ssf assemblages of eastern yunnan province meishucun xianfeng and huize regions the described sections represent shallow water deposits of the yangtze platform that include a number of stratigraphical hiati the reported ssf assemblages can be assigned to the regional ssf biozones i iii anabarites trisulcatus protohertzina anabarica assemblage zone paragloborilus subglobosus purella squamulosa assemblage zone watsonella crosbyi assemblage zone zones ii and iii are slightly redefined based on new data two subzones of zone ii are proposed here namely annelitellus yangtzensis obtusoconus honorabilis subzone and maikhanella cambriana oelandiella korobkovi subzone claviconchella qianyii gen et sp nov and bubiites simplex gen et sp nov are reported here we also provide a critical revision of the ssf distribution for the well known meishucun section the correlation scheme for east yunnan documents the extent and duration of stratigraphical hiati the distribution of ssfs and the lithological characterization indicate three major events of exposure of the carbonate platform resulting in sedimentary breaks and possible karstification this prompts new consideration of the previously described stable isotope stratigraphy of shallow platform strata considering the complexity of the terreneuvian earth history as well as the uniqueness of ssf an integration of sedimentology geochemistry and paleontology is needed for future ssf study

a link in the chain of the cambrian zooplankton bradoriid arthropods invade the water column bradoriids are small bivalved arthropods that had global distribution for about 20 million years beginning at cambrian epoch 2 c 521 ma the majority of bradoriids are considered to be benthic favouring oxygenated waters as suggested by their anatomy lithofacies distribution faunal associates and provinciality most bradoriids were extinct by the end of the drumian age middle of cambrian epoch 3 the post drumian is characterized by widespread dysoxic shelf lithofacies in southern britain and scandinavia and by the abundance of phosphatocopid arthropods this interval is also associated with two bradoriid species with wide intercontinental distribution anabarochilina primordialis which had a geographical range from the palaeo tropics to high southern palaeo latitude and anabarochilina australis which extended through the palaeo tropics from laurentia to gondwana the wide environmental and geographical range of these species coupled with a carapace anatomy that suggests an active lifestyle is used to infer a zooplanktonic lifestyle a possible driver of this widespread cambrian bradoriid zooplankton was sea level rise coupled to the periodic spread of low oxygen conditions onto continental shelves acting in tandem with anatomical pre adaptations for swimming parallels exist with the myodocope ostracod colonization of the water column during silurian time which may also have been influenced by extrinsic environmental controls acting on anatomical pre adaptations for swimming similar biological and environmental mechanisms may have facilitated arthropod zooplankton colonizations across phanerozoic time

breccias and ores part 1 history organization and petrography of breccias abstract although the term breccia is one of the oldest rock names still in use and proliferating in its application a satisfactory definition remains problematic and an overall classification of breccias is non existent the names of breccia varieties several hundred please the heart rather than the computer and there is little interdisciplinary correlation among the more than fifty specialized schools of breccia study this contribution reviews briefly the history of breccia research and provides a list of the present study trends complete with references with emphasis on ore associated breccias wherever possible conventional breccia definitions and their shortcomings are discussed and a case is made for the introduction of the petrographic category of coarse fragmentites of which the typical sedimentary breccias and conglomerates as well as volcanic tectonic hydrothermal impact and other fragmental materials are members whether designated or not as breccia in the conventional literature this is followed by a proposed rational organization classification of coarse fragmentites and breccias based on the regime of formation and architecture fabric gefuge two fundamental end member sequences a b and a transitional suite c can be recognized a disaggregation fragmentites d breccias produced from a solid progenitor by increasing rate of fracturing expansion rotation mixing and attrition the transitional sequence is crackle mosaic rubble melange milled breccia b aggregation fragmentites a breccias generated by gathering aggregation and accumulation of originally dispersed fragments at the site of deposition these materials form a sequence ranging from tightly packed fragment supported matrix free fragmentites through matrix infilled matrix supported fragmentites to lonestone rocks c in transport fragmentites t breccias formed by redeposition of an aggregate gathered in an earlier phase of development as an a fragmentite or by transportation and redeposition of an advanced member i e rubble melange or milled fragmental aggregate of a d fragmentite examples of metallic mineralizations coeval with or superimposed on the fragmentite sequences are reviewed

a suggestion for the origin of mesoscopic fabric in accretionary melange based on features observed in the chrystalls beach complex south island new zealand the chrystalls beach complex a probable accretionary melange of triassic age cropping out in south island new zealand contains a distinctive set of mesoscopic structures all of which contribute to the typically chaotic appearance of the melange these structures are 1 soft sediment bedding pull aparts 2 weakly developed slaty cleavage 3 folds in dismembered bedding with slaty cleavage as the axial surface foliation and 4 quartz fiber lineated shear surfaces analysis of overprinting relations indicates that these structures formed during a single progressive deformation rather than in several discrete events as such they record a change in response to incremental strain from initial ductile behavior toward one dominated by brittle failure it is suggested that this variation resulted from progressive dewatering during shallow level accretion at the base of an inner trench slope

discovering geochemical patterns using self organizing neural networks a new perspective for sedimentary provenance analysis abstract an unsupervised neural network technique growing cell structures gcs was used to visualize geochemical differences between sandstones of four different sedimentary provenance groups p1 mafic p2 intermediate p3 felsic and p4 recycled multidimensional data of four sandstone data sets comprising major elements log normalized major elements trace elements and high field strength elements hfse were projected into colored two dimensional maps that can be visually and quantitatively interpreted the cluster structure and variable distributions produced show that each sedimentary provenance group can be distinguished in the neural maps according to a unique combination of major or trace element concentrations in these terms the distinguishing features of each provenance group are p1 high fe2o3t tio2 mgo mno cao p2o5 sc v cr and cu p2 intermediate fe2o3t tio2 mgo mno cao sc v and cu p3 intermediate to high k2o intermediate sio2 and al2o3 low fe2o3t and tio2 and intermediate to low nb rb and th p4 high sio2 y nb rb th ba and zr coupled with low al2o3 cao na2o fe2o3t mgo mno and tio2 the elemental associations in p1 p2 and p3 reflect petrogenetic evolution of first cycle sources whereas the associations in p4 are compatible with the combined effects of recycling weathering and heavy mineral concentration

interplay between fluid flow and fault fracture mesh generation within underthrust sediments geochemical evidence from the chrystalls beach complex new zealand the chrystalls beach complex in the otago schist on the south island of new zealand is a melange comprising sheared trench fill sediments and fragments of oceanic crust it represents an exhumed analogue for underthrust sediments actively deforming along modern subduction thrust interfaces the melange is cross cut by a fault fracture mesh comprising subvertical extension veins and subhorizontal slickenfibre coated shear surfaces both shear and extension veins have a crack seal microstructure indicating episodic growth shear veins are associated with pressure solution selvages along the shear surface whereas wall rock alteration is not observed adjacent to extension veins electron microprobe analyses of selvage seams indicate dissolution of silica from the immediate surroundings of slickenfibre shear veins and therefore these slickenfibres probably grew by local dissolution precipitation of silica on the contrary no depletion or addition of silica is detected around extension veins indicating these veins grew by precipitation from advecting fluids oxygen isotope ratios measured in vein quartz show that shear and extension veins both precipitated from an aqueous fluid with 7 18o 10 consistent with a fluid derived from low grade metamorphic dehydration reactions fluid pressure therefore probably increased as fluids were introduced to a relatively impermeable melange with increasing metamorphic grade and decreasing porosity fault fracture mesh generation therefore involved localized shear assisted by dissolution precipitation creep and concomitant extension fracturing this led in turn to transient permeability associated with a fluid pressure drop allowing episodic vein growth this process may be analogous to geophysically observed episodic tremor and slow slip which also involves a mixture of deformation styles that put together achieve shear slip along the subduction thrust interface

correlation of the cambrian evolutionary radiation geochronology evolutionary stasis of earliest cambrian terreneuvian small shelly fossil ssf taxa and chronostratigraphic significance early faunas with watsonella crosbyi with or without aldanella spp have been equated with the siberian tommotian stage uppermost terreneuvian and used to define a proposed cambrian stage 2 base much earlier terreneuvian occurrences are now shown by recovery of these micromolluscs below the i carbon excursion in the siberian nemakit daldynian stage and comparable 13 c excursions in the middle meishucunian china and middle chapel island formation avalonia this 13 c excursion a reliable stage 2 marker lies in a c 10 ma interval in the cambrian radiation in which long ranged small shelly fossil taxa provide limited biostratigraphic resolution

global correlation of the early cambrian of south australia shelly fauna of the dailyatia odyssei zone a lack of well resolved biostratigraphic data has prevented robust regional and global correlation of lower cambrian successions from south australia a new early cambrian biostratigraphy based on data derived from 21 measured stratigraphic sections and drill cores 11 described herein reveals the abundance and diversity of shelly fauna from the arrowie basin and the value of early cambrian small shelly fossils ssf for biostratigraphic studies here we examine shelly fauna associated with the youngest of three recently established biozones the dailyatia odyssei taxon range zone hereafter d odyssei zone and their correlative potential the d odyssei zone features a diverse suite of tommotiids organophosphatic brachiopods bradoriid arthropods molluscs and phosphatic problematica this fauna permits strong correlation often at species level with other major early cambrian terranes particularly antarctica south china and laurentia and suggest a cambrian series 2 stages 3 4 age for the d odyssei zone bradoriids have proven to be useful biostratigraphic tools four new species and three new genera are described herein acutobalteus sinuosus gen et sp nov eozhexiella adnyamathanha gen et sp nov manawarra jonesi gen et sp nov and mongolitubulus descensus sp nov the description of eohadrotreta sp cf zhenbaensis represents the first occurrence of the acrotretoid brachiopod eohadrotreta from australia

early cambrian chronostratigraphy and geochronology of south australia abstract the most successful chronostratigraphic correlation methods enlist multiple proxies such as biostratigraphy and chemostratigraphy to constrain the timing of globally important bio and geo events here we present the first regional high resolution shelly fossil biostratigraphy integrated with 13c chemostratigraphy and corresponding 18o data from the traditional lower cambrian terreneuvian and provisional cambrian series 2 of south australia the global zhuce shice positive excursions ii and iii and the care are captured in lower cambrian successions from the arrowie and stansbury basins the south australian shelly fossil biostratigraphy has a consistent relationship with the 13c results bolstering interpretation identification and correlation of the excursions positive excursion ii straddles the boundary between the kulparina rostrata and micrina etheridgei zones and the care straddles the boundary between the m etheridgei and dailyatia odyssei zones peaking in the lower parts of the latter zone new ca tims zircon dates from the upper hawker group and billy creek formation provide geochronologic calibration points for the upper d odyssei zone and corresponding chemostratigraphic curve embedding the lower cambrian successions from south australia into a global chronostratigraphic context this multi proxy investigation demonstrates the power of integrated methods for developing regional biostratigraphic schemes and facilitating robust global correlation of lower cambrian successions from south australia part of east gondwana with coeval terranes on other cambrian palaeocontinents including south and north china siberia laurentia avalonia and west gondwana

neogene changes in southern ocean sedimentation based on mass accumulation rates at four continental margins 1 high resolution mass accumulation rates mar were determined from lithologic logs based on downhole log and continuous core data for six sites at four continental margins around the southern ocean total mar was calculated at ocean drilling program odp site 1095 on the margin of the antarctic peninsula and odp site 1165 on the margin of prydz bay antarctica carbonate and noncarbonate terrigenous mar were calculated for odp sites 1123 and 1124 east of new zealand and sites 1168 and 1172 west and southeast of tasmania shifts in carbonate mar are seen around tasmania and new zealand at 23 and 14 ma suggesting changes in deep water circulation and surface carbonate productivity at these times carbonate mar dropped at sites 1124 and 1168 at 23 ma and increased at 14 ma at sites 1123 1168 and 1172 the overall character of total mar at antarctic sites 1095 and 1165 is a continual and relatively constant decrease in total mar during the neogene with periods of stepwise decrease one such decrease is seen at 14 ma at site 1165 coincident with increased carbonate mar in new zealand and tasmania sites 1123 1124 1168 and 1172 and likely related to mid miocene expansion of the east antarctic ice sheet another step drop in total mar is seen at 9 ma at site 1165 possibly reflecting diversion of sediment to a newly formed prydz channel fan

census of the indian springs lagerstatte poleta formation cambrian western nevada usa abstract intervals of exceptional fossil preservation collectively termed the indian springs lagerstatte occur in the middle member of the poleta formation cambrian series 2 stage 3 in esmeralda county nevada usa the preserved macrofauna and taphonomic modes are similar to those of the spence shale lagerstatte of utah cambrian series 3 the indian springs macrofauna mostly consists of biomineralizing organisms such as trilobites helicoplacoids hyolithids and inarticulate brachiopods multi element taxa such as helicoplacoids and chancelloriids are commonly articulated examples of preserved nonbiomineralized anatomy include mantle setae of brachiopods demosponge skeletons hyolithid gut tracts trilobite appendages algae cyanobacteria and body parts of nonbiomineralizing arthropods the indian springs lagerstatte is dominated by fine siliciclastics and was deposited in an offshore shelf setting subjected to storm initiated sediment pulses exceptional preservation was facilitated by obrution type deposition presumably in dysoxic or anoxic muds and in environments where organismic remains were removed from durophagous carnivores and scavengers including bioturbators

continuous metamorphic gradient documented by graphitization and k ar age southeast otago new zealand the chrystalls beach brighton coastal section southwest of dunedin new zealand exposes otago schist including the weakly metamorphosed triassic accretionary melange of the chrystalls beach complex and higher grade rocks of a largely felsic arc derived provenance melange zones contain pelagic sediments some of which are manganiferous and metabasites the grade of metamorphism increases progressively from southwest to northeast four mineral zones are recognized largely on the basis of mineral assemblages in psammitic and semipelitic rocks pumpellyite chlorite pumpellyite actinolite epidote actinolite and biotite d 002 data for carbonaceous material b 0 values for phengite and metamorphic phengite k ar ages are reported for 32 pelitic and semipelitic samples remarkably tight correlations are revealed between d 002 for progressively graphitized carbonaceous material k ar ages that range from 184 6 to 138 7 ma and linear distance along the section both the d 002 values and the k ar ages decrease progressively toward the northeast through the four mineral zones and with progressive textural changes all rocks cropping out in the section have undergone a coherent episode of progressive metamorphism associated with terrane collision and have not been disturbed by any later major displacements a convex trend for phengite b 0 values plotted against advancing graphitization suggests p t conditions during metamorphism as in the high pressure intermediate facies series the age of the metamorphic peak is inferred to be 175 155 ma middle to late jurassic with cooling to the mica closure temperature at 155 135 ma late jurassic to early cretaceous unloading denudation and cooling were accompanied by localized hydrothermal events the oldest covering strata were deposited at ca 100 ma and denudation was completed by ca 75 80 ma middle triassic radiolarian nodules in melange zones are dated as preceding the metamorphic peak by about 65 ma associated turbidites contain suspected late middle to early late triassic tube fossils

climatic responses to tropical sea surface temperature changes on a greenhouse earth the uncertainty associated with tropical sea surface temperatures ssts during past greenhouse climates may have important and unaccounted for effects we explore early paleogene climatic sensitivity to changes in tropical subtropical ssts with a general circulation model we demonstrate that tropical sst changes have local and far field climatic effects underscoring their importance in understanding greenhouse climates the responses of winds upwelling and surface water balance to tropical sst changes are substantial our results indicate that current tropical sst reconstructions may have a significant cool bias despite corrections and that the existence of hot 30 c tropical ssts may be realistic for greenhouse climate intervals including the eocene

paterimitra pyramidalis laurie 1986 the first tommotiid discovered from the early cambrian of north china abstract the eccentrothecimorph tommotiid paterimitra pyramidalis laurie 1986 was previously only known from lower cambrian rocks of the northern territory and south australia herein we document the first occurrence of p pyramidalis from the xinji formation in the shuiyu section at ruicheng county shanxi province located at the southwestern margin of the north china platform this represents the first report of a tommotiid taxon from lower cambrian strata of the north china platform all three sclerite types that characterise the scleritome of p pyramidalis have been recovered and are described permitting definitive identification to species level the discovery of p pyramidalis from the north china platform not only greatly extends the palaeogeographic range of this distinctive tommotiid taxon but also supports planktotrophic development of larvae in paterimitra as a stem group brachiopod the discovery of p pyramidalis supports a cambrian epoch 2 late age 3 to early age 4 age for the shelly fossil fauna from the xinji formation and indicates a close palaeogeographic position between the north china platform and australian east gondwana during the early cambrian

combining finite strain analysis and illite crystallinity to examine strain variation in a shale detachment zone abstract determining the physical conditions and material properties of low grade sub green schist facies deformation accurately is problematic due to the lack of adequate strain indicators and mineral equilibrium assemblages with established relationships to pressure and temperature conditions for low grade deformation proxies such as illite crystallinity are often used to provide broad constraints on these conditions the relationship between illite crystallinity and temperature remains qualitative however it has been suggested that illite crystallinity may be a more appropriate proxy for tectonic strain at low temperatures recent work on an exposed shale detachment zone in the khao khwang fold thrust belt has described strain partitioning into shale dominated shear domains which delineate coarser grained fault domains this strain partitioning is a key influence in the development of the complex three dimensional shear zone networks which characterise the multiple shale detachment zones in the area here we apply both the fry method of finite strain analysis and illite crystallinity by x ray diffraction analysis to examine the potential strain variations between different shear and fault domains shear domains show less variable and higher grade illite crystallinity values while the fry method results show higher strain values in these shear domains this is confirmed by qemscan mineral mapping of each domain type where shear domains show a far more developed tectonic fabric indicating a much higher degree of strain is accommodated continually throughout these relatively thin shear zones the fault domains they delineate by contrast show far less internal strain which is accommodated discontinuously by discrete low offset fault planes data from our results also show a remarkably strong correlation between illite crystallinity and finite strain and while the small number of samples involved in this study leads us to caution the over interpretation of these results it points to a strong relationship between illite crystallinity and finite strain at low temperatures if further investigated and quantified this relationship could provide a powerful and inexpensive tool for strain determination in fine grained rocks

the middle lower cambrian ovetian lunagraulos n gen from spain and the oldest trilobite records the type material of agraulos antiquus sdzuy 1961 from the la herreria formation northern spain is revised together with additional material and included in the new genus lunagraulos the stratigraphical range of lunagraulos antiquus sdzuy 1961 occurring below that of the trilobite species of the genera lunolenus metadoxides and dolerolenus in the type locality of los barrios de luna in the province of leon northern spain and the accompanying ichnofossil assemblage demonstrate an ovetian age lower part of cambrian stage 3 currently being discussed by the international subcommission on cambrian stratigraphy for this species moreover the trilobite lunagraulos tamamensis n gen n sp is found in the tamames sandstone near the village of la rinconada in the province of salamanca central spain the biostratigraphical position of this new taxon and its accompanying ichnoassemblage is also analysed and assigned to the lowermost ovetian stage the genus lunagraulos is therefore the oldest agraulid found in the fossil record the exceptional presence of lunagraulos in a marine coarse siliciclastic succession a facies rather typical for the ichnofossils cruziana and rusophycus some of the oldest signs of trilobite activity suggests that first trilobite representatives may have inhabited high to middle energy marine environments this hypothesis may also explain both the taxonomic and biostratigraphic heterogeneity of the first trilobite genera appearing across the world due to preservation problems in this type of facies comparison of the lunagraulo s biostratigraphy with other coeval spanish fossil assemblages allows us to propose its intercontinental correlation with the oldest records of currently known trilobites

first report of the early cambrian stem group brachiopod mickwitzia from east gondwana abstract the first mickwitziid brachiopod mickwitzia sp from east gondwana is described from the lower cambrian ajax limestone mt scott range in south australia the shells are fragmentary but preserve sufficient details of morphology and micro structure to allow positive identification to genus the morphology of the dorsal valve apex and the extended cones on the internal surface indicate a close affinity with mickwitzia muralensis walcott 1913 from the early cambrian of british columbia but scarcity of material precludes detailed comparison this find extends the known range of the pivotal stem group brachiopod mickwitzia to east gondwana

chronology of early cambrian biomineralization data on the first appearances of major animal groups with mineralized skeletons on the siberian platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the cambrian radiation popularly known as the cambrian explosion with a higher precision and provide a basis for the definition of cambrian stages 2 to 4 the lophotrochozoa and probably chaetognatha were first among protostomians to achieve biomineralization during the terreneuvian epoch mainly the fortunian age fast evolutionary radiation within the lophotrochozoa was followed by radiation of the sclerotized and biomineralized ecdysozoa during stage 3 the first mineralized skeletons of the deuterostomia represented by echinoderms appeared in the middle of cambrian stage 3 the fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late neoproterozoic but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians the distribution of calcium carbonate skeletal mineralogies from the upper ediacaran to lower cambrian reflects fluctuations in the global ocean chemistry and shows that the cambrian radiation occurred mainly during a time of aragonite and high magnesium calcite seas

tectonic significance of ductile deformation in low grade sandstones in the mesozoic otago subduction wedge new zealand this study demonstrates how ductile strain measurements can determine the tectonic evolution of a large and long lived subduction wedge we provide a synthesis of the geology of the south island of new zealand with an emphasis on a wedge tectonics perspective that contrasts with a traditional view that interprets new zealand geology in the context of terrane collision and accretion we argue that the otago subduction wedge evolved in a steady fashion throughout its 290 to 105 ma history in response to accretion of trench fill and abyssal plain sediments and slow erosion of a subaerially exposed forearc high maximum temperatures for rocks in the flanks of the forearc high were no greater than 150 to 300 c with solution mass transfer active as the dominant ductile mechanism the 54 studied samples provide information about the absolute ductile strains acquired all along their flow path from the site of accretion to exhumation in the forearc high we use tensor averages to estimate strain at a regional scale these show plane strain uniaxial flattening given that the tensor averages for sy and sx are close to one on average sz is approximately 0 77 and this is balanced by a mass loss of about 23 percent the average z direction is sub horizontal in the prowedge and moderately plunging in the retrowedge a difference attributed to spatial variations in the mode of accretion we infer that rocks presently in the pro side of the otago high were sourced by frontal accretion and those in the retro side were underplated this result highlights the important role of accretion in determining the style of within wedge deformation and also demonstrates the benefit of using a tensor averaging approach to examine regional strain

fractal vein distributions within a fault fracture mesh in an exhumed accretionary melange chrystalls beach complex new zealand a well developed fault fracture mesh is observed in the chrystalls beach complex an accretionary melange within the otago schist on the south island of new zealand in this study an analysis of vein thicknesses and clustering of veins is presented both shear and extension veins have a power law thickness distribution measures of vein spacing best fit a power law distribution but a small data set limits this interpretation to a small fractal range vein clustering varies from random to moderately clustered between outcrops and is the greatest where a large proportion of relatively competent blocks occurs within the melange fractures are distributed within the melange matrix and this localized deformation requires heterogeneity in rheology and or fluid pressure distribution whereas pervasive distributed deformation occurs in relatively homogeneous rock the overall trend of this deformation being mainly accommodated by thin veins required that new fractures formed preferentially over refracturing existing veins which highlights the distributed nature of deformation within a fault fracture mesh the predominance of new fractures may result from vein material being stronger than the cleaved wall rock such that wall rock failure occurred instead of reopening of pre existing shear and extension veins

first occurrence of a new ocruranus like helcionelloid mollusc from the lower cambrian of east gondwana a new cap shaped mollusc emargimantus angulatus gen et sp nov is described from the arrowie basin of south australia the new species is closely comparable to mollusc species from south china and north east greenland previously described under the generic name ocruranus liu a genus recently reinterpreted as a multiplated possibly polyplacophoran mollusc emargimantus is interpreted as a univalved helcionelloid mollusc and differs from ocruranus in both morphology and function e angulatus represents the first discovery of ocruranus like helcionelloids in the lower cambrian of eastern gondwana and demonstrates that these molluscs had a global distribution during the early cambrian

extraction of high resolution carbonate data for palaeoclimate reconstruction temporal variations in the calcium carbonate content of deepsea sediments provide direct stratigraphic as well as important palaeoenvironmental information relating to the global carbon cycle here i present an algorithm that allows carbonate content and porosity to be accurately predicted from saturated bulk density in equatorial pelagic carbonates applying the algorithm to continuous laboratory measurements of density made on dsdp and oop cores yields a nearly continuous carbonate record for the upper 200 m of the sediment section long ultra high resolution carbonate curves of this type should yield new insight into the evolution of the carbon chemistry of the oceans as well as the role of external milankovitch forcing in the development of the carbonate system the algorithm can also be applied to quantitative high resolution seismic data thereby enabling detailed carbonate records to be extracted from remotely derived geophysical data

sedimentary phosphorus record from the oman margin new evidence of high productivity during glacial periods 1 the northern region of the arabian sea is one of the biologically most fertile regions of the world oceans with present productivity rates varying between 150 and 2500 mgc m2 day madhupratap et al 1996 this is related to the influence of the southwesterly summer monsoon which causes vigorous upwelling along the oman margin upwelling ceases during northeasterly winter monsoon activity productivity rates however remain relatively high about 800 mgc m2 day related to deep water mixing madhupratap et al 1996 the goal of this study is to verify if during the last glacial period a period in which winter monsoon conditions prevailed productivity rates were similarly high with an analysis of phosphorus phases stable nitrogen isotopes organic matter content and bulk mineralogy of the upper 10 m of the cores of odp hole 724c corresponding to the last 140 000 years sample resolution is 5 kyr we provide new evidence of high productivity during this last glacial period marine isotopic stages 2 3 and 4 this was probably related to the combined effect of 1 increased eolian input of iron containing dust due to dryness on the adjacent continent and stronger winter monsoon and 2 regeneration and diffusion of dissolved phosphorus from the sediments to the water column due to variations in the position and intensity of the oxygen minimum zone these findings suggest that there is no one to one relationship between summer monsoon activity and productivity which emerges to be a quasi persistent phenomenon across glacial and interglacial stages

high resolution 104 years deep sea foraminiferal stable isotope records of the eocene oligocene climate transition we have constructed high resolution 104 105 years benthic foraminiferal 13c and 18o records for the upper eocene through lower oligocene of two pelagic sequences deep sea drilling project dsdp site 522 in the angola basin south atlantic ocean and ocean drilling program odp site 744 in the southern indian ocean these records provide improved constraints on both the timing and magnitude of marine oxygen and carbon isotope events from 30 to 35 ma the oxygen isotope records indicate that the ubiquitous 18o increase oi 1 which marks the rapid expansion of continental ice sheets and a minimum of 3 to 4 c of cooling of bottom waters in the earliest oligocene 33 6 ma occurred in 350 kyr more than half the transition occurred over the final 40 50 kyr this period of lower temperatures and widespread continental glaciation persisted for roughly 400 kyr i e the duration of magnetochron c13n these records also indicate that this interval was characterized by at least two 100 kyr waxing and waning cycles oi 1a and oi 1b and possibly several higher frequency events the benthic foraminiferal 13c records show a positive 0 8 excursion that is nearly isochronous with the oi 1 oxygen isotope increase similar magnitude 13c increases at other sites indicate this was a global phenomenon suggestive of an unusually large perturbation to the carbon cycle this excursion was followed by smaller amplitude 13c oscillations with periods of roughly 400 kyr we suspect that the ubiquitous oi 1 13c excursion resulted from a brief but substantial increase in export production and carbon burial

tectonic and paleobiogeographic significance of radiolarian microfaunas in the permian to mesozoic basement rocks of the north island new zealand abstract from the terranes sutured to the new zealand gondwana margin in mid cretaceous time the murihiku waipapa torlesse and mata river terranes have yielded tectonically and paleographically significant radiolarian faunas a late jurassic fauna from the murihiku forearc terrane is more cosmopolitan than coeval faunas from the waipapa faunas from the terranes east of the murihiku which all show evidence of accretion tectonics can be subdivided into ocean floor assemblages and assemblages of terrigenous clastic deposits waipapa ocean floor assemblages are typically tethyan while the terrigenous clastic assemblages are non tethyan possibly of southern hemisphere high latitude origin ocean floor assemblages show the same eastward younging trends opposed to the westward sedimentological younging due to imbrication as do the assemblages of the terrigenous clastics but are always a few tens of million years older radiolarians from ophiolites tangihua volcanics and matakaoa volcanics indicate that significant portions of the ocean floor obducted onto new zealand in late oligocene to earliest miocene time were of late cretaceous to early tertiary age

the relative roles of boudinage and structural slicing in the disruption of layered rock sequences the dominant micro and mesoscopic structural features of many melanges fault zones and other disrupted rock sequences are anastomosing shear surfaces these surfaces progressively dismember and isolate sections of stiffer lithologies within more ductile matrix in a process referred to here as structural slicing this process is distinct from classical boudinage and when recognized as such may provide a means for differentiating normal boudinaged schist and gneiss terranes from metamorphosed melanges in many sheared melanges structural slicing dominates over both sedimentary processes olistostromal deposition soft sediment deformation and other tectonic processes folding boudinage in the formation of blocks and control of the overall melange geometry this is true at all scales of observation from the production of small clasts to the definition of kilometer scale knockers

neoproterozoic to early cambrian small shelly fossil assemblages and a revised biostratigraphic correlation of the yangtze platform china abstract small shelly fossils ssfs occur widely on the yangtze platform and have great potential for biostratigraphic subdivision of pre trilobitic early cambrian strata based on the ssf record of the shallow water realm five biozones can be recognized for the meishucunian stage in ascending order the biozones are anabarites trisulcatus protohertzina anabarica assemblage zone paragloborilus subglobosus purella squamulosa assemblage zone watsonella crosbyi assemblage zone formerly heraultipegma yunnanensis zone poorly fossiliferous interzone sinosachites flabelliformis tannuolina zhangwentangi assemblage zone in addition one ssf biozone is recognized for the overlying qiongzhusian stage pelagiella subangulata taxon range zone the formerly used siphogonuchites triangularis paragloborilus subglobosus zone and heraultipegma yunnanensis zone are discussed and redefined approximately 80 species of ssfs were screened for their spatial and temporal distribution on the yangtze platform variations in lithofacies and biofacies can be recognized throughout the yangtze platform extending over an area of 2000 900 km in a deeper water shelf setting the first zone is represented by the protohertzina anabarica kaiyangites novilis assemblage zone while younger zones are not recognized in the southern region at the northern platform margin the qiongzhusian is represented by the ninella tarimensis cambroclavus fangxianensis assemblage zone and the rhombocorniculum cancellatum taxon range zone the southeastern shaanxi western hubei region followed a slightly different lithological and faunal development than the rest of yangtze platform indicating a stronger similarity with parts of east gondwana some taxa such as w crosbyi p subangulata r cancellatum microdictyon effusum a trisulcatus protohertzina unguliformis and p anabarica occur nearly worldwide and support an international correlation of early cambrian sequences between the yangtze platform and smaller west gondwanan blocks siberia newfoundland and australia the six investigated zones of the yangtze platform comprise an interval spanning the early nemakit daldynian to the late atdabanian early botoman stage on the siberian platform palaeobiogeographic analysis revealed a strong taxic similarity between the yangtze platform and the tarim platform a smaller number of species are shared with other west gondwanan platform fragments such as india and iran palaeobiogeographic results do not support the previously reported position of the south china block between australia and siberia during the early cambrian

determining the composition of late quaternary marine sediments from nuv vis and nir diffuse reflectance spectra abstract as the length of marine cores increases and sampling intervals decrease the need for rapid and inexpensive means of determining sediment composition has become apparent in this study we examine one potentially useful technique for assessing compositional changes in marine cores diffuse reflectance spectrophotometry we examined nearultraviolet visible and near infrared reflectance spectra from five data sets each data set consists of calibration samples and test samples the calibration samples spectra were related to a sediment component using multiple linear regression the resulting regression or calibration equations were then evaluated using the test samples calibration equations were written relating spectra to several sediment components including carbonate atlantic and east pacific rise odp site 847 organic carbon content atlantic and east pacific rise and opal content east pacific rise the correlation coefficients for the regression equations ranged from a high of 0 99 for carbonate and opal at odp site 847 to a low of 0 97 for atlantic carbonate indicating that spectral variations are highly correlated to sediment composition all of the equations include a substantial number of variables from shorter visible and longer near ultraviolet wavelengths suggesting that these wavelengths are especially important for devices designed specifically to scan marine cores although equations for estimating organic and carbonate content appear independent of other sediment components the opal equation is strongly dependent on carbonate content indicating that opal concentration is correlated to carbonate content tests of the calibration equations indicated that all our equations reasonably estimate the pattern of changes either down core or in surface sediments where our spectral estimates have difficulty is with absolute values frequently over or underestimating observed values by a substantial amount within these limitations diffuse reflectance spectrophotometry can be a useful tool for characterizing marine cores and as our understanding of the relationship between spectra and mineralogy improves so will estimates of absolute values

watsonella crosbyi from the lower cambrian terreneuvian stage 2 normanville group in south australia correlation of lower cambrian strata is often confounded by provincialism of key fauna the widespread occurrence of the micromollusc watsonella crosbyi grabau 1900 is therefore an important biostratigraphic signpost with potential for international correlation of lower cambrian successions previous correlations of w crosbyi from australia normanville group suggested an atdabanian to botoman equivalent age however in the upper part of the mount terrible formation stratigraphic ranges of w crosbyi and aldanella sp cf golubevi overlap prior to the incoming of vertically burrowed piperock which is indicative of an age no earlier than cambrian stage 2 the stratigraphic range of w crosbyi in the normanville group south australia correlates with the ranges of the taxon in china france mongolia and siberia though not newfoundland the new australian data add further support for considering the first occurrence of w crosbyi a good potential candidate for defining the base of cambrian stage 2 the stratigraphic range of w crosbyi through the lower cambrian normanville group has been determined based on collections from measured sections although rare w crosbyi is part of an assemblage of micromolluscs including bemella sp parailsanella sp cf murenica and a sinistral form of aldanella a sp cf a golubevi other fauna present include australohalkieria sp eremactis mawsoni chancelloriids and cupitheca sp

the development of the sw pacific margin of gondwana correlations between the rangitata and new england orogens prior to formation of the tasman sea the late paleozoic mesozoic rangitata orogen of new zealand and new caledonia abutted the paleozoic new england orogen of eastern australia comparison of the record of permian cretaceous igneous and deformational events from the two orogens suggests that their tectonic evolution was interrelated and is a consequence of convergent plate interaction along the southwest pacific margin of gondwana the following relations are proposed 1 termination of arc volcanism and widespread sedimentation in new england together with the onset of regional deformation and crustal anatexis were synchronous with the commencement of volcanism and sedimentation within the rangitata orogen 2 early permian andesitic volcanism in eastern new england represents an along strike extension of the brook street terrane of new zealand 3 late permian regional deformation in new england coincides with both a break in subduction related igneous activity in the new england and rangitata orogens and a shift in the locus of this activity 4 late permian triassic calc alkaline igneous activity in new england correlates with a phase of relatively continuous accumulation of pyroclastic material in the forearc basin of the rangitata orogen 5 cessation of plutonism in new england corresponds with commencement of formation of the esk head melange in new zealand and the probable commencement of juxtaposition of the te anau and alpine assemblage 6 late cretaceous epizonal plutons intruded into the new england orogen are similar in character and age to those emplaced during the final phases of rangitata orogenesis and both appear to mark initial stages of rifting associated with formation of the tasman sea the generation of permian and triassic igneous activity in eastern new england by convergent plate interaction results on present reconstructions of the gondwana margin in an excessively wide arc trench gap succession for the position of the trench is constrained to east of new caledonia from the permian onward this suggests there may have been some rearrangement of tectonic elements along the margin resulting in widening of the lord howe rise between australia and new caledonia in the period between termination of igneous activity in new england and formation of the tasman sea in the late cretaceous

melange rheology and seismic style shear displacements in crustal fault zones are accommodated by a range of seismic styles including standard earthquakes non volcanic tremor and continuous and transitory aseismic slip subduction channel shear zones containing highly sheared fluid saturated trench fill sediments intermingled with fragments of oceanic crust are commonly inferred to occur along active subduction megathrusts if this interpretation is correct these plate boundary faults are not discrete planes but may resemble the melange shear zones commonly found in exhumed subduction related rock assemblages melange deformation appears to depend critically on the ratio of competent to incompetent material with shear surfaces localized along lithological contacts or within competent domains while matrix flow accommodates shearing by distributed strain if the style of strain and or displacement accommodation in a melange reflects the partitioning between aseismic and seismic slip the proportion of competent material seems likely to be a significant factor affecting seismic style within subduction channel shear zones and along comparable mixed lithology fault zones

back scattered electron imagery of the tectonic fabrics of some fine grained sediments implications for fabric nomenclature and deformation processes back scattered electron investigations of argille scagliose mudstones from the barbados forearc sampled during ocean drilling program leg 110 and the matrix of the okitsu melange southwest japan indicate a variety of microfabric geometries and deformation mechanisms despite the similarity of their mesoscopic scaly fabrics in the okitsu melange the scaly fabric is the mesoscopic expression of an anastomosing microfabric whereas the detailed geometry of scaly fabrics is unrelated to the microfabric in the argille scagliose and leg 110 mudstones care must be taken in the classification and interpretation of scaly fabrics in light of these data and future studies should focus on microstructural investigations

facies phosphate and fossil preservation potential across a lower cambrian carbonate shelf arrowie basin south australia abstract the effects of sedimentological depositional and taphonomic processes on preservation potential of cambrian small shelly fossils ssf have important implications for their utility in biostratigraphy and high resolution correlation to investigate the effects of these processes on fossil occurrence detailed microfacies analysis biostratigraphic data and multivariate analyses are integrated from an exemplar stratigraphic section intersecting a suite of lower cambrian carbonate palaeoenvironments in the northern flinders ranges south australia the succession deepens upsection across a low gradient shallow marine shelf six depositional facies sequences are identified ranging from protected fs1 and open fs2 shelf lagoonal systems high energy inner ramp shoal complex fs3 mid shelf fs4 mid to outer shelf fs5 and outer shelf fs6 environments non metric multi dimensional scaling ordination and two way cluster analysis reveal an underlying bathymetric gradient as the main control on the distribution of ssfs unlike groups that produced primary organophosphatic biominerals taxa that built calcareous skeletons are more taphonomically controlled which is further exacerbated by sampling and processing biases a strong facies association with condensed and reworked horizons suggests the stratigraphic occurrence of calcareous groups reflects conditions conducive to preservation phosphogenesis and phosphatization rather than true stratigraphic ranges consequently organophosphatic taxa should take precedence in the erection of biostratigraphic zones for subdivision of lower cambrian successions

a hyolithid without helens preserving the oldest hyolith muscle scars palaeobiology of paramicrocornus from the shujingtuo formation cambrian series 2 of south china the hyolithid paramicrocornus zhenbaensis from the lower cambrian cambrian series 2 shuijingtuo formation of southern shaanxi and western hubei provinces of the yangtze platform is well preserved

systematics and biogeography of some early cambrian series 2 bradoriids arthropoda from laurentia greenland bradoriid arthropods are described from the kap troedsson and henson gletscher formations of north greenland and the bastion formation of north east greenland cambrian series 2 stage 4 hipponicharion skovstedi n sp and beyrichona avannga n sp represent species of genera originally described from avalonia new brunswick that are characteristic of middle latitude assemblages in the early cambrian they are described for the first time from low latitude environments in the early cambrian of laurentia where they occur together in a middle to upper carbonate ramp succession navarana n gen is proposed for a rare hipponicharionid currently known only from north greenland

late cenozoic changes in atmospheric circulation deduced from north pacific eolian sediments abstract isolation and analysis of the eolian component of late cenozoic pelagic sediments from the north pacific provides direct information concerning changes in atmospheric circulation a 50 increase in intensity of both the prevailing westerlies and the tradewinds coincides with increasing pole to equator temperature gradients resulting from the onset of northern hemisphere glaciation at the same time the mass flux of dust from continents to the north pacific increased by a factor of 4 5 apparently reflecting significantly increased continental aridity associated with the late cenozoic glacial ages

evaluating optical lightness as a proxy for carbonate content in marine sediment cores abstract optical lightness is increasingly being used as a proxy for the carbonate content of marine sediment we compared three measurements of optical lightness gray scale brightness and l to carbonate content to test the reliability of these measurements as carbonate content proxies in five piston cores from isotope stages 1 though 6 0 130 ka all measures of optical lightness are reasonable proxies of relative but not absolute changes in carbonate content in contrast in the upper sediments of odp hole 997a which are holocene to pliocene in age lightness values in only the top 10 m of the 180 m analyzed exhibit a strong correlation to carbonate content to better understand which factors control the optical lightness of sediments we analyzed samples in which carbonate content remained constant while the composition of three common clay minerals chlorite illite and kaolinite was varied kaolinite even at a concentration of 20 did not significantly change optical lightness however 20 illite reduced optical lightness by 30 and 20 chlorite reduced lightness by 20 we conclude that regional and temporal changes in the composition of the non carbonate sediment fraction may significantly alter the relationship between lightness and carbonate content we recommend that care must be taken when applying these measures to sediment sequences which span long time intervals or to sediment samples taken over a broad geographical areas

the problematic fossil triplicatella from the early cambrian of greenland canada and siberia the problematic fossil triplicatella from the early cambrian of greenland canada and siberia

on the origin of hyolith helens abstract helens the curved lateral spines inserted between the conch and operculum of some hyoliths are a unique morphological adaptation characterizing the order hyolithida these structures are paired movable and had a mechanical function probably related to orienting the hyolith conch and lifting its aperture above the sea floor we show that helens are intimately associated with the hyolith opercula and are structurally comparable to the rod like units that constitute the clavicles internal wall like structures of the hyolithid operculum that probably evolved to secure the operculum from lateral displacement in the conch aperture in some early cambrian hyolith taxa that lack helens such as paramicrocornus new clavicle rods are added in the gap separating the clavicles from the cardinal processes the same position where helens are inserted in later hyolithids we also show that the size of incipient helens at the earliest ontogenetic stage matches the size of the clavicles in associated opercula we propose that helens are modified clavicle rods that were detached from the operculum and developed into lateral spines through allometric growth during early ontogeny further we suggest a four step model for the evolution of hyolithid hyoliths from orthothecid ancestors 1 externally fitting operculum 2 stabilizing radially arranged structures on the inside of the operculum 3 ligula and folded operculum 4 detachment of clavicle rods and origin of helens

late cenozoic eolian deposition in the north pacific asian drying tibetan uplift and cooling of the northern hemisphere a newly constructed record of eolian dust accumulation from the central north pacific shows that dust deposition increased by an order of magnitude quite rapidly at 3 6 ma we associate this sudden drying with the uplift of at least the northern portion of the tibetan plateau shutting off the indian ocean moisture source to central and western china this ten fold increase in atmospheric dust loading appears to be associated with the 1 m y long shift toward heavy 18o values that occurred at 3 6 2 6 ma the dust grain size record of wind intensity begins its late cenozoic coarsening a million years before the drying event at 4 5 ma the northern hemisphere cooling that results in intensification of the subpolar westerly winds may have as its ultimate cause the drawdown of atmospheric co2 in the latest miocene and the early pliocene closing of the panamanian seaway

frequency size distribution of competent lenses in a block in matrix melange imposed length scales of brittle deformation 1 this study explores the frequency size distribution of competent lenses phacoids in the chrystalls beach complex a melange shear zone within the otago schist accretion collision assemblage new zealand the distribution of phacoids within a cleaved pelitic matrix follows a power law distribution with exponent 1 18 d 2 37 2 d at outcrop scale whereas distributions at thin section scale have higher d than the outcrop they were sampled from d relates to volume fraction and distribution of competent material where high d correlates with small aspect ratio phacoids and high matrix volume fraction in outcrops which experienced mixed continuous discontinuous deformation d 1 4 0 2 it is suggested that d 1 4 indicates dominant continuous deformation whereas d 1 4 is indicative of localized deformation on shear discontinuities in this melange d therefore appears a function of dominant deformation style actively deforming melange shear zones likely exhibit a range of seismic styles and earthquake magnitudes at length scales limited by lithological layering and shear zone thickness a hypothesis is suggested where strongly coupled shear zone segments may be distinguished by a high volume fraction of competent material low d while aseismically creeping regions are characterized by a high proportion of incompetent rock high d as the b value in the gutenberg richter frequency magnitude relationship also tends to be high in coupled and low in creeping fault segments it may be that d is analogous to b and the b value is also related to the ratio of incompetent competent material and dominant fault zone deformation style

foliated breccias in the active portuguese bend landslide complex california bearing on melange genesis the active portion of the portuguese bend landslide complex is approximately 3 km2 in area and 30 50 m thick measured displacement rates range from less than 1 to greater than 30 mm day on different parts of the landslide with total displacements over the last 30 yrs ranging from about 10 to greater than 150 m six types of breccia each locally with a foliated matrix were recognized in the active landslide complex and are absent outside the landslide complex slide body breccias are of two types the first formed by extensional fracturing during bulk pure shear at the top of the landslide slide top breccia and the second by flow of tuffaceous shales and fracture of embedded siliceous shales during simple shear deep in the landslide to the basal decollement slide bottom breccias slide margin breccias also in simple shear are produced on the lateral margins of individual slide blocks accompanying wrench fault motion other breccias fault ramp breccias are formed during motion over ramps coll

diffuse spectral reflectance as a proxy for percent carbonate content in north atlantic sediments diffuse reflectance records from fern drift in the north atlantic faithfully record sediment percent carbonate a high resolu tion reflectance based age model for these sediments derived from an orbitally tuned age model for western equatorial atlantic ceara rise sediments was generated by spectral frequency mapping power spectra of the fern drift record indicate statistically significant sub milankovitch cyclicity at 7 6 8 4 and 4 8 6 1 kyr we infer that these 8 and 5 kyr cycles document a linkage between north and equa torial atlantic climate given our ability to correlate these records these climate cycles influence atlantic basin carbonate prior to the intensification of northern hemisphere glaciation and thus must arise from some portion of the climate system other than the dynamics of large ice sheets the presence of these peaks which could be related to equatorial clipped precession implies a possible non linear response to milankovitch forcing abstract diffuse reflectance records from feni drift in the north atlantic faithfully record sediment percent carbonate a high resolu tion reflectance based age model for these sediments derived from an orbitally tuned age model for western equatorial atlantic ceara rise sediments was generated by spectral frequency mapping power spectra of the feni drift record indicate statistically significant sub milankovitch cyclicity at 7 6 8 4 and 4 8 6 1 kyr we infer that these 8 and 5 kyr cycles document a linkage between north and equa torial atlantic climate given our ability to correlate these records these climate cycles influence atlantic basin carbonate prior to the intensification of northern hemisphere glaciation and thus must arise from some portion of the climate system other than the dynamics of large ice sheets the presence of these peaks which could be related to equatorial clipped precession implies a possible non linear response to milankovitch forcing

heat transport deep waters and thermal gradients coupled simulation of an eocene greenhouse climate for the first time a coupled general circulation model with interactive and dynamical atmospheric oceanic and sea ice components is used to simulate an eocene 50 ma greenhouse climate we introduce efficient ocean spin up methods for coupled paleoclimate modeling sea surface temperatures ssts and salinities evolve unconstrained producing the first proxy data independent estimates for these eocene climate parameters tropical and extratropical model predicted ssts are warmer than modern values by 3 and 5 c respectively salinity driven deep water formation occurs in the north atlantic and tethys the zonal average overturning circulation is weaker than modern eocene ocean heat transport is 0 6 pw less than modern in the northern hemisphere and 0 4 pw greater in the southern hemisphere the model predicted near modern vertical and meridional eocene temperature gradients imply that the dominant theory for maintaining low gradients increased ocean heat transport is incorrect or incomplete and other mechanisms should be explored

biogeography and affinities of the bradoriid arthropods cosmopolitan microbenthos of the cambrian seas abstract this paper reviews the global biogeography and affinities of the bradoriida a group of cambrian early ordovician arthropods bradoriida appear in the fossil record during the early cambrian just prior to the earliest trilobite faunas seven families may form a natural monophyletic group of bradoriida sensu stricto comprising cambriidae kunmingellidae comptalutidae bradoriidae hipponicharionidae beyrichonidae and svealutidae amongst the bradoriida sensu lato some forms that lie outside these families have carapace designs that suggest an ostracod affinity particularly altajanella and vojbokalina bradoriida formed a major element of the cambrian evolutionary fauna and are components of the chengjiang burgess shale and buen formation lagerstatten bradoriida achieved global distribution from the atdabanian early cambrian their diversity peaked during the early and middle cambrian with highest diversity at the species and genus level amongst the palaeo tropical faunas of the south china 17 genera and east gondwana palaeocontinental regions 23 genera by contrast laurentian faunas were of much lower diversity 10 genera for the whole cambrian bradoriid diversity declined rapidly from the latest middle cambrian a trend that may be related to the major extinction of trilobites at the base of the late cambrian the youngest bradoriida comprise a few rare ordovician forms bradoriids appear to have occupied well oxygenated marine shelf facies the biogeographical patterns of early and middle cambrian bradoriida suggest climatic control on their distribution temperate and tropical faunas together with palaeogeographical constraints that also reflect trilobite provinciality kunmingellids and comptalutids were restricted to palaeo tropical subtropical sites but migrated between south china siberia and eastern gondwana palaeocontinents they are absent from the mid and high latitude faunas of the western gondwana avalonia and baltica palaeocontinental areas that were dominated by hipponicharionids beyrichonids and bradoriidae the laurentia palaeocontinent was isolated from the main zones of bradoriid diversity but its faunas include a number of early and middle cambrian bradoriidae indota bradoria walcottella and the region was colonised by cosmopolitan cambriids during the early cambrian and by supposed pelagic svealutids liangshanella and anabarochilina during the middle cambrian the genera walcottella dielymella and bullaluta were endemic to laurentia one species of anabarochilina that possibly dwelt near the sea surface achieved an equatorial to high southern latitude 70 s distribution during the late middle cambrian lejopyge laevigata biozone perhaps reflecting a reduced latitudinal temperature gradient for near surface ocean waters

the gundahl complex of the new england fold belt eastern australia a tectonic melange formed in a palaeozoic subduction complex abstract the new england fold belt of eastern australia preserves a palaeozoic fore arc terrain with a magmatic arc fore arc basin and a subduction complex the gundahl complex is a tectonic melange of regional extent in the subduction complex the matrix and slabs of the gundahl complex have six mappable lithofacies argillite greywacke argillite greywacke argillite tuff bedded chert and greenstone the argillite matrix is pervasively sheared with many slickensided shear fractures locally the matrix is formed by highly sheared greenstone greywacke and greenstone blocks are affected by internal shear zones and the blocks themselves pinch and swell folds in places with axial surface spaced cleavage are common within those slabs comprised of well bedded sequences bedding plane shear and faulting at a high angle to bedding also occur in these slabs on a map scale much of the gundahl complex comprises slabs up to 10 km long in imbricate fault bounded slices which repeat the disrupted pre melange stratigraphic sequence elsewhere there are lithologically distinctive blocks containing thick coherent sequences which are structurally incorporated into the gundahl complex the unit is believed to have formed by accretion imbrication and subsequent tectonic disruption of arc derived sediments and less abundant pelagic sediment and greenstone in an ancient subduction complex

geology of the seismogenic subduction thrust interface a microseismically active layer of underthrust sediments is commonly inferred along subduction thrust interfaces the exhumed chrystalls beach complex in the otago schist new zealand may be analogous to an actively deforming underthrust rock assemblage the complex contains asymmetric competent lenses of sandstone chert and basalt enclosed in a cleaved mudstone matrix continuous fabrics such as folds boudins and asymmetric phacoids formed by distributed cataclasis and dissolution precipitation creep discontinuous deformation is evident in an extensive fault fracture mesh involving mutually cross cutting subvertical extension veins and subhorizontal slickenfibre shear surfaces the hikurangi margin provides an example of along strike variations in seismic style possibly related to heterogeneous fluid pressure state and interface geology in both the ancient and active subduction related shear zone fluid pressure state appears to be a critical control on frictional failure which primarily occurs on weak fluid overpressured discontinuities continuous aseismic deformation occurs where other mineral deformation mechanisms such as dissolution precipitation creep are preferred the geometry and composition of the underthrust rock assemblage appear to be first order controls on megathrust fluid pressure distribution bulk rheology and dominant deformation mechanism and thus may be significant controls on megathrust seismic style

the scleritome of eccentrotheca from the lower cambrian of south australia lophophorate affinities and implications for tommotiid phylogeny the first partially articulated scleritome of a tommotiid eccentrotheca sp is described from the lower cambrian of south australia the eccentrotheca scleritome consists of individual sclerites fused in a spiral arrangement forming a tapering tube shaped skeleton with an inclined apical aperture and a circular to subcircular cross section traditionally tommotiid sclerites have been assumed to form a dorsal armor of imbricating phosphatic plates in slug like bilaterians analogous to the calcareous sclerites of halkieriids the structure of the eceentrotheca scleritome is here reinterpreted as a tube composed of independent irregularly shaped sclerites growing by basal marginal accretion that were successively fused to form a rigid protective tubular structure the asymmetrical shape and sometimes acute inclination of the apical aperture suggests that the apical part of the scleritome was cemented to a hard surface via a basal disc from which it projected vertically rather than being a vagrant member of the benthos eccentrotheca most likely represented a sessile vermiform filter feeder the new data suggest that the affinities of eccentrotheca and possibly some other problematic tommotiids lie with the lophophorates i e the phoronids and brachiopods a clade that also possesses a phosphatic shell chemistry and a sessile life habit

shear veins observed within anisotropic fabric at high angles to the maximum compressive stress some faults seem to slip at unusually high angles 45 relative to the orientation of the greatest principal compressive stress1 2 3 4 5 this implies that these faults are extremely weak compared with the surrounding rock6 laboratory friction experiments and theoretical models suggest that the weakness may result from slip on a pre existing frictionally weak surface7 8 9 weakening from chemical reactions10 elevated fluid pressure11 12 13 or dissolution precipitation creep14 15 here we describe shear veins within the chrystalls beach accretionary melange new zealand the melange is a highly sheared assemblage of relatively competent rock within a cleaved anisotropic mudstone matrix the orientation of the shear veins compared with the direction of hydrothermal extension veins that formed contemporaneously indicates that they were active at an angle of 80 5 to the greatest principal compressive stress we show that the shear veins developed incrementally along the cleavage planes of the matrix thus we suggest that episodic slip was facilitated by the anisotropic internal fabric in a fluid overpressured heterogeneous shear zone a similar mechanism may accommodate shear at high angles to the greatest principal compressive stress in a range of tectonic settings we therefore conclude that incremental slip along a pre existing planar fabric coupled to high fluid pressure and dissolution precipitation creep may explain active slip on severely misoriented faults

a new lower cambrian shelly fossil biostratigraphy for south australia abstract definition of early cambrian chronostratigraphic boundaries is problematic with many subdivisions still awaiting ratification integrated multi proxy data from well resolved regional scale schemes are ultimately the key to resolving broader issues of global correlation within the cambrian in australia early cambrian biostratigraphy has been based predominantly on trilobites phosphatic shelly fauna have great potential as biostratigraphic tools especially in pre trilobitic strata because they are widespread and readily preserved but they have remained underutilised here we demonstrate their value in a new biostratigraphic scheme for the early cambrian of south australia using a diverse shelly fauna including tommotiids brachiopods molluscs and bradoriids biostratigraphic data are derived from ten measured stratigraphic sections across the arrowie basin targeting hawker group carbonates including the wilkawillina wirrapowie and ajax limestones and the mernmerna formation the stratigraphic ranges of shelly fossils are predictable and repeatable across the arrowie basin allowing three discrete shelly biozones to be identified spanning terreneuvian stage 2 to series 2 stages 3 4 the kulparina rostrata zone new and part of the overlying micrina etheridgei zone new are pre trilobitic predominantly terreneuvian the cambrian series 2 stage 3 dailyatia odyssei zone new features a very diverse shelly fauna and will be described in detail in a separate publication these zones provide robust means to correlate terreneuvian series 2 successions in neighbouring coeval basins in australia particularly the stansbury basin wider correlation is possible throughout east gondwana and especially with south china

cenozoic mass accumulation rates in the equatorial pacific based on high resolution mineralogy of ocean drilling program leg 199 1 we use continuous mineralogy logs derived from multisensor track physical properties data and reflectance spectroscopy to calculate high resolution carbonate opal and terrigenous mass accumulation rates mar for the eight sites cored during ocean drilling program leg 199 in the equatorial pacific the largest change in equatorial pacific sedimentation patterns of the last 55 myr occurs at the greenhouse icehouse transition shortly after the eocene oligocene boundary calcite compensation depth deepened dramatically the equatorial zone of opal accumulation narrowed and the intertropical convergence zone shifted to the equator during the paleogene the opal equatorial accumulation bulge extended to about 12 n whereas the neogene bulge extended only to about 7 n very low eocene carbonate mar was followed by much higher oligocene and early miocene mar with the carbonate equatorial bulge extending to 4 n terrigenous mars indicate the paleoposition of the intertropical convergence zone and a pliocene pleistocene increase in asian dust flux

challenges in defining the base of cambrian series 2 and stage 3 formal subdivision of the cambrian system into four series and ten stages is in progress the base of cambrian stage 3 provisional which is conterminous with the base of cambrian series 2 provisional is expected to be placed at a horizon close to the first appearance of trilobites which marks the onset of the largest phase of the cambrian explosion conceptually an ideal boundary position would be marked by a significant and globally recognizable bioevent that divides the lower part of the cambrian system into a sub trilobitic terreneuvian series and a trilobite dominated series 2 if the level is to be identified principally through biostratigraphic means its position also needs to be recognizable using non biostratigraphic means and its correlation potential should be tested through detailed investigation of several continuous successions embracing the critical interval major difficulties in identifying a suitable horizon include strong biotic provincialism a plethora of regional unconformities and facies changes on different paleocontinents in the cambrian terreneuvian series 2 boundary interval levels that provide potential for intercontinental correlation include the first appearance position of trilobites and the approximately equivalent first appearance positions of certain small shelly fossil and acritarch species in addition a non biostratigraphic marker such as a stable carbon isotopic excursion may be useful as a correlation level cambrian series 2 and stage 3 are provisional stratigraphic units and their conterminous base was previously suggested to coincide to the appearance of trilobites compared to other potential chronostratigraphic indicators the first appearance of trilobites still has advantages for recognizing and correlating the base of stage 3 and should remain as the provisional primary marker for the boundary position

on stress and strain in a continuous discontinuous shear zone undergoing simple shear and volume loss i summarise observations within a continuous discontinuous shear zone to discuss the local stress and strain conditions experienced within a mixed rheology shear zone undergoing volume loss and deformation approximating simple shear the chrystalls beach complex new zealand comprises phacoids formed from dismembered beds by layer parallel extension enclosed within a relatively incompetent matrix local extension is generally subparallel to the regional direction of shortening and overall it appears that layer parallel extension is a geometrical necessity in low angle shear zones where significant flattening occurs in response to simple shear accompanied by volume loss preferential stress loading of phacoids is predicted by fibre loading theory and the failure of phacoids by brittle fracture is thereby governed by fibre stresses transferred from the matrix the principal stress orientations in a phacoid are likely rotated relative to the matrix and either parallel or perpendicular to the phacoid matrix interface as preferential loading of phacoids decreases the stress level in the matrix an increased volume fraction of phacoids increases the strength of the shear zone as a whole however only small matrix volume fractions are required for the composite to act nearly as weak as the matrix 2012 elsevier ltd all rights reserved

geologic and gravity evidence for thrust emplacement of the smartville ophiolite detailed structural relationships at the margins of ophiolites can provide important information about the mode of emplacement of ophiolitic terranes in this study we use geologic mapping and gravity data to determine the structural and tectonic relations between a middle to late jurassic volcanic arc complex the smartville ophiolite block and a pre late jurassic melange terrane in the northern sierra nevada foothills the volcanic arc complex overlies the melange along a complex fault zone although this fault zone is steeply dipping wherever it is observed map patterns suggest that the smartville upper volcanic unit was originally emplaced along a subhorizontal fault that has been subsequently deformed two dimensional interactive computer analysis of gravity data from over 200 stations shows that the smartville upper volcanic unit is a relatively shallow feature with a maximum thickness ranging from 0 5 to 3 km and that it was thrust as a sheet over the previously deformed melange both units were subsequently folded giving rise to the steeply dipping faults observed at the surface recognition of low angle thrusting along the northern margin of the smartville ophiolite block has important implications for the mode of emplacement of the block the most plausible mechanism for the thrusting of this particular oceanic island arc sequence onto the continental margin involves a subduction zone dipping westward beneath the smartville ophiolite block similar to the present day situation in the molucca sea collision zone

cambrian evolutionary radiation context correlation and chronostratigraphy overcoming deficiencies of the first appearance datum fad concept abstract use of the first appearance datum fad of a fossil to define a global chronostratigraphic unit s base can lead to intractable correlation and stability problems fads are diachronous they reflect species evolutionary history dispersal biofacies preservation collection and taxonomy the cambrian evolutionary radiation is characterised by diachronous fads biofacies controls and provincialism of taxa and ecological communities that confound a stable lower cambrian chronostratigraphy cambrian series and stage definitions require greater attention to assemblage zone successions and non biostratigraphic particularly carbon isotope correlation techniques such as those that define the ediacaran system base a redefined basal cambrian trichophycus pedum assemblage zone lies above the highest ediacaran type biotas vendobionts putative metazoans and calcareous problematica such as cloudina and the basal asteridium tornatum comasphaeridium velvetum zone acritarchs this definition and the likely close correspondence of evolutionary origin and local fad of t pedum preserves the fortune head newfoundland gssp of the cambrian base and allows the presence of sub cambrian branched ichnofossils the sub tommotian equivalent base of stage 2 a suggested laolinian stage should be defined by the i l4 zhuce 13 c positive peak bracketed by the lower ranges of watsonella crosbyi and aldanella attleborensis molluscs and the skiagia ornata fimbrioglomerella membranacea zone acritarchs the w crosbyi and a attleborensis fads cannot define a stage 2 base as they are diachronous even in the newfoundland type w crosbyi zone the series 2 base cannot be based on a species fad owing to the provincialism of skeletalised metazoans in the terreneuvian series 2 boundary interval and global heterochrony of the oldest trilobites a series 2 and stage 3 a suggested lenaldanian series and zhurinskyan stage new gssp base is proposed at the siberian lower atdabanian 13 c iv peak which correlates into south china avalonia and morocco and assigns the oldest trilobites to the terminal terreneuvian series

the emplacement and fault history of the coolac serpentinite lachlan fold belt southeastern australia abstract the tumut synclinorial zone located in the lachlan fold belt southeastern australia forms a fault bounded belt of early silurian volcanics and flyschoid metasediments of the tumut trough the mooney mooney fault system containing an extensive ultramafic belt known as the coolac serpentinite forms the eastern margin of the trough the ultramafics together with mafic volcanics and intrusive grabbroic rocks have been previously interpreted as early palaeozoic oceanic crust dismembered and obducted during late silurian deformation of the silurian trough sequence recent work however has unravelled a more complex history involving several periods of movement the ultramafics and early silurian volcanics are intruded by early silurian gabbro and syn kinematic late silurian granodiorite these intrusive relationships indicate that the ultramafic rocks were present in approximately their present structural position prior to deformation of the trough sequence the ultramafics therefore cannot represent early silurian oceanic crust obducted during the late silurian deformation they probably represent either early silurian or cambrian ordovician mantle derived material emplaced within a strike slip fault zone during early silurian oblique extension

diagenetic controls on the structural evolution of siliceous sediments in the golconda allochthon nevada u s a abstract a model is proposed that links the diagenesis of siliceous sedimentary rocks with deformation to explain the heterogeneous structural fabric of radiolarian cherts in the upper paleozoic golconda allochthon of nevada u s a numerous thrust faults slice the cherts into packets each with a unique set of internal structures fold geometries boudin profiles pressure solution features etc vary from packet to packet and layer to layer analogous variations in the diagenetically mixed siliceous sediments of the miocene monterey formation california suggest the cherts of the golconda allochthon were similarly mixed when they were deformed radiolarian sediments composed of biogenic silica opal a developed ductile structures and pressure solution features because of their high porosity weak lithification and the high solubility of disordered silica lowporosity strongly lithified relatively insoluble quartz cherts the final product of silica diagenesis deformed in a brittle fashion and developed fewer pressure solution features diagenetically intermediate ct cherts and ct porcelanites exhibited transitional behavior mixed diagenetic zones produced structures with layer by layer changes in structural style the dehydration of opal a and opal ct helped create the excess pore fluid pressures responsible for thrust faults hydraulic fractures dilation breccias and elastic intrusions the presence of ductile structures and numerous pressure solution features in the oldest cherts of the havallah sequence suggests that these cherts were deformed while diagenetically immature possibly within a long lived upper paleozoic accretionary prism

skeletal fossils and microfacies analysis of the lowermost cambrian in the southwestern margin of the north china platform abstract the xinji and zhushadong formations are the oldest record of cambrian deposits in the southwestern margin of the north china platform the two lithostratigraphic units are carbonate dominated in lithology and are cambrian series 2 in age the basal unit the xinji formation yields diverse skeletal fossils including sponge spicules chancelloriid sclerites hyoliths micromolluscs trilobites echinoderm ossicles cambroclaves tianzhushanellids protoconodonts and other small shelly fossils the fossil assemblage as the earliest fauna of the cambrian in north china provides an important window to investigate the cambrian explosion in the region and contains fossil elements with biostratigraphical significance seven microfacies types of the xinji and zhushadong formations are recognized 1 phosphorized and selectively dolomitized bioclastic grainstone 2 dolomitized ooid grainstone 3 dolomitized peloid wackstone 4 lime mudstone preserved as dolomitic microsparite 5 siliciclastic wackstone 6 calcareous siltstone and 7 breccia the different microfacies are traced to three successive depositional environments beginning with a bioclastic shoal then a mixed depositional back shoal and finally an oolitic shoal the system of the shoal and back shoal is interpreted as representing the mixed siliciclastic carbonate deposition during the initial transgression of the north china platform as well as the early development of an epeiric environment

the operculum and mode of life of the lower cambrian hyolith cupitheca from south australia and north china the operculum of the problematic tubular fossil cupitheca holocyclata bengtson in bengtson et al 1990 is described for the first time based on collections from south australia and north china the phosphatized sub circular operculum exhibits well defined cardinal processes and a narrow cardinal shield unequivocally demonstrating that cupitheca is a hyolith probably an orthothecid c holocyclata has an almost global distribution in cambrian stages 3 4 the apical structure of the operculum is an elevated disc shaped platform with a concave base and a marginal rim that could represent the scar of a specialized larval attachment structure perhaps anchoring the larval hyolith to a sediment grain algae or other benthic substrate cupitheca probably had a pelagic larval stage and settled on the seafloor by attachment of the apical disc to suitable substrates before developing a free living benthic adult lifestyle this contrasting mode of life compared to other hyolith genera suggests that the group had already evolved a range of distinct lifestyles in the cambrian providing significant clues into their ecology and distribution

progressive development of block in matrix fabric in a shale dominated shear zone insights from the bobbio tectonic window northern apennines italy 1 block in matrix is a common fabric characterizing highly deformed to apparently chaotic rocks originated by sedimentary tectonic and mud diapiric processes in many exposed orogenic belts a true melange originates when this fabric is associated with mixing of rocks of different ages and provenance as that characterizing the main decollement shear zone developed between the highly allochthonous ligurian nappe and its substratum of foredeep deposits at the margins of the bobbio tectonic window trebbia valley northern apennines mixing of rocks by both mass transport processes and synsedimentary thrusting occurs at the front and tectonic erosion at the base of the nappe during its emplacement evidence of polyphased deformations spanning from liquefaction related and hydroplastic structures to pseudo hydrofracturing features and mineralized veining have been recognized within the marginal portions and along the sheared contacts of blocks encased within a scaly matrix crosscutting relationships testify a progressive deformation involving a transition from mesoscopic ductile to brittle conditions with the significant contribution of fluid overpressure a novel evolutionary scheme for block in matrix fabric development is here proposed involving the progressive dismembering of already highly deformed units originally developed in non to poorly lithified conditions through a generalized simple shearing achieved during the evolution of the shear zone coupled with strain hardening due to tectonic compaction synkinematic diagenesis and fluid expulsion

a new early cambrian bradoriid arthropoda assemblage from the northern flinders ranges south australia abstract a new assemblage of early cambrian bivalved arthropods bradoriida is described from the arrowie syncline in the northern flinders ranges south australia the well preserved largely endemic fauna comprises a total of six taxa including five new species jiucunella phaseloa sp nov jixinlingella daimonikoa sp nov mongolitubulus anthelios sp nov neokunmingella moroensis sp nov phasoia cf spicata opik 1968 and sinskolutella cuspidata sp nov this assemblage is derived from a carbonate sedimentary package representing a high energy shallow water archaeocyath renalcis biohermal facies of terreneuvian stage 2 age which transitions up section to a more restricted low energy intra shelf lagoonal environment that correlates with a cambrian series 2 stage 3 age the new taxon j phaseloa sp nov has a first appearance datum fad in shallow water biohermal facies of the hideaway well member of the wilkawillina limestone at a level 47 m below the fad of pelagiella subangulata which is taken to approximate the base of series 2 stage 3 in south australia along with liangshanella circumbolina this makes j phaseloa sp nov amongst the oldest bivalved arthropods in south australia and potentially greater gondwana the presence of 25 bradoriid taxa from the early cambrian of south australia suggests east gondwana represents a major centre of origin for the bradoriida

petrography and geochemistry of the carboniferous triassic trinity peninsula group west antarctica implications for provenance and tectonic setting the carboniferous triassic trinity peninsula group is a metasedimentary sequence that crops out widely in the northern antarctic peninsula these are some of the most extensive outcrops in the area and hold the key to evaluating the connections of the antarctic peninsula in gondwana however they are still poorly understood here we present our provenance study of the trinity peninsula group using petrographic and geochemical approaches in combination with cathodoluminescence of detrital quartz in order to constrain its source characteristics and tectonic setting using differences in modal composition and quartz cathodoluminescence characteristics we define three petrofacies derived from the progressive uplift and erosion of a volcano plutonic continental arc which exposed the plutonic metamorphic roots as indicated by major and trace elements the source is felsic with a composition ranging from tonalitic to granodioritic the relatively unweathered condition of the source area points to a dry and cold climate at the time of deposition but this does not necessarily mean that it was glaciated deposition of the sediments occurred within an active continental margin relatively close to the source area probably along the south patagonia antarctic peninsula sector of gondwana strong chronological petrological and chemical similarities with the sediments of the duque the york complex in patagonia suggest that they were derived from the same source

palaeoscolecid scleritome fragments with hadimopanella plates from the early cambrian of south australia phosphatized articulated palaeoscolecid scleritome fragments with attached hadimopanella gedik 1977 plates are described from the lower cambrian mernmerna formation of south australia hadimopanella is principally known from single isolated button shaped phosphatic sclerites the new articulated material from south australia reveals for the first time the configuration of plates referable to hadimopanella within the scleritome the scleritome fragments represent the main trunk sections of the cuticle with anterior and posterior terminations lacking each annulus on the trunk is ornamented by rows of irregularly alternating hadimopanella plates the large majority of plates display a single centrally located conical node referable to the form species h apicata wrona 1982 however individual plates display considerable morphological variation with plates situated along the flattened trunk margin identical to the form species h antarctica wrona 1987 the south australian material displays the detailed scleritome configuration of cuticular plates and platelets and demonstrates irrefutably that plates of the form species h apicata and h antarctica occur as mineralized cuticular elements on the same palaeoscolecid scleritome

schmidt hammer exposure age dating shd of late quaternary fluvial terraces in new zealand schmidt hammer sh r values are reported for surface clasts from numerically dated holocene and pleistocene fluvial terraces in the south island of new zealand the r values are combined with previously obtained weathering rind radiocarbon terrestrial cosmogenic nuclide and luminescence terrace ages to derive sh r value chronofunctions for greywacke clasts from four distinct locations our results show that different weathering rates affect the form of the sh r value versus age curve however a fundamental dependency between the two remains constant over timescales ranging from 102 to 105 years power law scaling constants suggest changes in clast weathering rates are primarily affected by climatic precipitation and temperature and sedimentologic variables source terrane petrology age uncertainties of 22 of the surface age suggest that schmidt hammer exposure age dating shd is a reliable calibrated age dating technique for fluvial terraces copyright 2013 john wiley sons ltd

incrementally developed slickenfibers geological record of repeating low stress drop seismic events an accretionary melange of triassic age ocean floor sediments exposed in the chrystalls beach complex south island new zealand comprises competent sandstone and chert phacoids set in a cleaved mudstone matrix deformed in a continuous discontinuous style at subgreenschist conditions deformation structures include a pervasive anastomosing fault fracture mesh of multiple shearing surfaces subparallel to cleavage coated with incrementally developed quartz calcite slickenfibers microstructural observations reveal slickenfiber growth by crack seal shear slip increments of 10 100 m with incremental slip transfer of the same order accommodated by opening of extension fractures that link en echelon slip surfaces individual slip surfaces can be traced for meters to tens of meters so that the ratio of average slip u to potential rupture length l predominantly lies within the range 10 6 u l 10 5 characteristic of microearthquakes obeying constant stress drop scaling with a low stress drop 30 kpa typical of low frequency earthquakes the host rock assemblage metamorphic environment inference of near lithostatic fluid overpressures low stress drop and mixed continuous discontinuous shearing resemble conditions and characteristics of low frequency earthquakes as identified within the seismic signals recorded during episodic tremor and slow slip events at the downdip end of the seismogenic subduction thrust interface and within accretionary prisms