458 research outputs found
Lacustrine carbonate platforms:Facies, cycles, and tectonosedimentary models for the presalt Lagoa Feia Group (Lower Cretaceous), Campos Basin, Brazil
Where My Girls At?
The essays, artistic pieces, and interviews gathered in this anthology explore both the role of art and visual culture as well as artistic practices in contemporary feminist movements. The art historians, literary scholars, artists, activists, and students and scholars of American Studies included in this collection examine contemporary art and artivism and its capacity to inspire change, reformulate feminist ideas, and reimagine feminist aesthetics. With contributions by young scholars, students, activists, and artists, the collection seeks to display a broad range of perspectives. Recurring themes are the ambivalent labeling of art and artistic or activist practices as âfeministâ as well as the role of intersectionality in feminism and art. This edited volume brings together the diverse strands of thought and practice that contemporary feminist art and culture embrace and hopes to contribute to ongoing discussions at the intersection of art and feminist politics
THE CALLOVIAN UNCONFORMITY AND THE OPHIOLITE OBDUCTION ONTO THE PELAGONIAN CARBONATE PLATFORM OF THE INTERNAL HELLENIDES
The carbonate-platform-complex and the oceanic formations of the central Pelagonian zone of the Hellenides evolved in response to a sequence of plate tectonic episodes of ocean spreading, plate convergence and ophiolite obduction. The biostratigraphies of the carbonate platform and the oceanic successions, show that the Triassic-Early Jurassic platform was coeval with an ocean where pillow basalts and radiolarian cherts were being deposited. After convergence began during late Early- Jurassic - Middle Jurassic time, the oceanic leading edge of the Pelagonian plate was subducted beneath the leading edge of the oceanic, overriding plate. The platform subsided while a supra-subduction, volcanic-island-arc evolved. Biostratigraphic and geochemical evidence shows that the platform and the oceanic floor, temporarily became subaerially exposed during Callovian time. This âCallovian eventâ is suggested to have taken place as oceanic lithosphere first made compressional, tectonic contact with the carbonate platform, initiating a basal detachment fault, along which the platform was thrust upwards. The central Pelagonian zone became an extensive land area that was supplied with laterite from an ophiolite highland. A similar emergence of Vardar ophiolite most likely took place in the Guevgueli area. The Callovian emergence shows that the initial ophiolite obduction onto the platform took place about 25 million years before the final emplacement of the ophiolite during Valanginian time
Influences of salinity on the physiology and distribution of the Arctic coralline algae, Lithothamnion glaciale (Corallinales, Rhodophyta)
In Greenland, free-living red coralline algae contribute to and dominate marine habitats along the coastline. Lithothamnion glaciale dominates coralline algae beds in many regions of the Arctic, but never in GodthĂ„bsfjord, Greenland, where Clathromorphum sp. is dominant. To investigate environmental impacts on coralline algae distribution, calcification and primary productivity were measured in situ during summers of 2015 and 2016, and annual patterns of productivity in L. glaciale were monitored in laboratory-based mesocosm experiments where temperature and salinity were manipulated to mimic high glacial melt. The results of field and cold-room measurements indicate that both L. glaciale and Clathromorphum sp. had low calcification and photosynthetic rates during the Greenland summer (2015 and 2016), with maximum of 1.225 ± 0.17 or 0.002 ± 0.023 ÎŒmol CaCO3 · g-1 · h-1 and -0.007 ±0.003 or -0.004 ± 0.001 mg O2 · L-1 · h-1 in each species respectively. Mesocosm experiments indicate L. glaciale is a seasonal responder; photosynthetic and calcification rates increase with annual light cycles. Furthermore, metabolic processes in L. glaciale were negatively influenced by low salinity; positive growth rates only occurred in marine treatments where individuals accumulated an average of 1.85 ± 1.73 mg · d-1 of biomass through summer. These results indicate high freshwater input to the GodthĂ„bsfjord region may drive the low abundance of L. glaciale, and could decrease species distribution as climate change increases freshwater input to the Arctic marine system via enhanced ice sheet runoff and glacier calving.Peer reviewedFinal Accepted Versio
How do thrombolites form? Multiphase construction of lacustrine microbialites, Purbeck Limestone Group, (Jurassic), Dorset, UK
AbstractThis paper examines how nonâmarine thrombolites are formed through a complex, multiphase process of microbial framework construction, erosion, cementation, recrystallization and episodes of internal sedimentation. Recognition of such phases of thrombolite construction provides a framework for the interpretation of the fluctuating environmental conditions leading to their formation. Microbialite frameworks are examined in detail from the Purbeck Limestone Group and their affinities and palaeoâenvironmental significance assessed. Three types of thrombolite, one stromatolite and a leolite are described and interpreted. The thrombolite frameworks include: a peloidal mesoclotted type, a thrombolite constructed by the filamentous alga Cladophorites and a type with concentrically laminated micritic mesoclots. Physical and chemical erosion led to extensive early cavity formation within the frameworks. Early calcite rim cements with associated spherulites then developed over the microbial frameworks and these were reworked into cavities. Frameworks were also replaced by chalcedonic quartz and calcite spherulites. Internal sediments comprise peloids, intraclasts and brackishâwater molluscs and ostracods, together with their debris. The thrombolites grew in moderateâenergy to highâenergy shallow, lacustrine, microbial mounds whereas stromatolites occurred in deeperâwater settings. A brackishâwater, lacustrine setting is indicated by the preserved macroâbiota, microbes, absence of charophytes and syndepositional evaporites, and negative stable carbon and oxygen isotope ratios. Strontium isotopes suggest that the carbonateârich waters were fed from erosion of MidâLower Jurassic limestones on the western basin margin with possible mixing with waters from nearby uplifted Upper Jurassic limestones and with Late Jurassic seawater. The research indicates that nonâmarine thrombolites have a complex, multiphase origin resulting in a diverse succession of textures and structures relating to microbially induced and influenced construction, dissolution, cementation, recrystallization and mineral replacement which have not been previously recorded and indicate the major differences between marine and nonâmarine thrombolites.</jats:p
Boring bivalve traces in modern reef and deeper-water macroid and rhodolith beds
Macroids and rhodoliths, made by encrusting acervulinid foraminifera and coralline algae, are widely recognized as
bioengineers providing relatively stable microhabitats and increasing biodiversity for other species. Macroid and
rhodolith beds occur in different depositional settings at various localities and bathymetries worldwide. Six case
studies of macroid/rhodolith beds from 0 to 117m water depth in the Pacific Ocean (northern Central Ryukyu
Islands, French Polynesia), eastern Australia (Fraser Island, One Tree Reef, Lizard Island), and the Mediterranean Sea
(southeastern Spain) show that nodules in the beds are perforated by small-sized boring bivalve traces
(Gastrochanolites). On average, boring bivalve shells (gastrochaenids and mytilids) are more slender and smaller than
those living inside shallow-water rocky substrates. In the Pacific, Gastrochaena cuneiformis, Gastrochaena sp., Leiosolenus
malaccanus, L. mucronatus, L. spp., and Lithophaga/Leiosolenus sp., for the first time identified below 20m water depth,
occur as juvenile forms along with rare small-sized adults. In deep-water macroids and rhodoliths the boring bivalves
are larger than the shallower counterparts in which growth of juveniles is probably restrained by higher overturn rates
of host nodules. In general, most boring bivalves are juveniles that grew faster than the acervulinid foraminiferal and
coralline red algal hosts and rarely reached the adult stage. As a consequence of phenotypic plasticity, small-sized
adults with slow growth rates coexist with juveniles. Below wave base macroids and rhodoliths had the highest
amounts of bioerosion, mainly produced by sponges and polychaete worms. These modern observations provide
bases for paleobiological inferences in fossil occurrences.Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)
Japan Society for the Promotion of Science
Grants-in-Aid for Scientific Research (KAKENHI)
25247083Erasmus+FAR2012-2017FIR2016FIR2018PRIN "Biotic resilience to global change: biomineralization of planktonic and benthic calcifiers in the past, present and future"
2017RX9XXXYBioMed Central-Prepay Membership at the University of FerraraJunta de AndalucĂa
RNM 190Committee on ResearchMuseum of PaleontologyDepartment of Integrative Biology, UC BerkeleyUC Pacific Rim Projec
Influence of extensional faults and relay ramp on palaeotopography and lacustrine carbonate facies: Purbeck Limestone Group (Upper Jurassic - Lower Cretaceous), Wessex Basin, UK
AbstractLacustrine carbonate facies distribution is controlled by multiple environmental parameters including climate, hydrology, and tectonic setting, but few published models address this complexity. In this study, seismic and borehole data, integrated with outcrop logging, correlations, and facies models, are used to create a new tectonoâsedimentary model demonstrating how extensional faults, linked by a relay ramp, control distribution of lacustrine carbonate facies in the Upper Jurassic to Lower Cretaceous Purbeck Limestone Group (Wessex Basin, UK). Accumulation occurred in halfâgraben subâbasins south of two extensional eastâwest faults, with widespread subaerial emergence of footwall blocks to the north. The lacustrine limestones of the lowest unit of this Group are characterised by inâsitu microbial mounds within bedded interâmound packstonesâgrainstones. Mounds occur in three depositional intervals separated by paleosols. The distribution of facies indicates more brackishâwater conditions shoreward to the west, and more hypersaline conditions basinward to the east. The relay ramp hosts extensive microbial carbonate buildups formed in response to carbonateârich waters sourced from the northern limestone footwall blocks that fed into extensive shallowâwater areas on the lowâangle relay ramp slope.</jats:p
Brackish to hypersaline facies in lacustrine carbonates: Purbeck Limestone Group, Upper Jurassic-Lower Cretaceous, Wessex Basin, Dorset, UK
Variations in architecture and cyclicity in fault-bounded carbonate platforms: Early Miocene Red Sea Rift, NW Saudi Arabia
The Early Miocene was a period of active rifting and carbonate platform development in the Midyan Peninsula, NW Saudi Arabia. However, there is no published literatures available dealing with detail characterization of the different carbonate platforms in this study area. Therefore, this study aims at presenting new stratigraphic architectural models that illustrate the formation of different carbonate platforms in the region and its forcing mechanisms that likely drove their formation. This study identified the following features formed during active rifting: a) a Late Aquitanian (N4) fault-block hangingwall dipslope carbonate ramp b) a Late Burdigalian (N7-N8) isolated normal fault-controlled carbonate platform with associated slope deposits, and c) a Late Burdigalian (N7-N8) attached fault-bounded, rimmed shelf developed on a footwall fault-tip within a basin margin structural relay zone formed coinciding with the second stage of rifting. Variations in cyclicity have been observed within the internal stratigraphic architecture of each platform and also between platforms. High-resolution sequence stratigraphic analysis show parasequences observed as the smallest depositional packages (meter-scale cycles) within the platforms. The hangingwall dipslope carbonate ramp and the attached platform demonstrate aggradational-progradational parasequence stacking patterns. These locations appear to have been more sensitive to eustatic cyclicities, despite the active tectonic setting. The isolated, fault-controlled carbonate platform reveals disorganized stratal geometries in both platform-top and slope facies, suggesting a more complex interplay of rates of tectonic uplift and subsidence, variation in carbonate productivity, and resedimentation of carbonates, such that any sea-level cyclicity is obscure. This study explores the interplay between different forcing mechanisms in the evolution of carbonate platforms in active extensional tectonic regions. Characterization of detailed parasequence-scale internal architecture allows the spatial variation in syn-depositional relative base-level changes to be inferred and is critical for understanding the development of rift basin carbonate platforms. Such concepts may be useful for the prediction of subsurface facies relationships beyond interwell areas in hydrocarbon exploration and reservoir modeling activities
- âŠ