Query: limestone

title: The permeability of stylolite bearing limestone
abstract: Stylolites are planar features that form due to intergranular pressure solution. Due to their planar geometry and relative abundance in limestone reservoirs, their impact on regional fluid flow has attracted considerable interest. We present laboratory permeability data that show that stylolites can be considered as conduits for flow in the stylolite bearing limestones measured. A combination of analysis techniques shows that this is due to a zone that surrounds these stylolites that is more porous and contains larger pores than the host rock. Our data also show that the water permeability of a sample containing a stylolite parallel to fluid flow is typically lower than its permeability to gas, explained here as a result of the expansion of minor amounts of clay found in the stylolite, and that, due to their microstructural similarities, tectonic and sedimentary stylolites affect sample permeability similarly. Finally, we show that the permeability anisotropy that develops in the rock mass due to the presence of sedimentary stylolites makes it appear as though the stylolites are acting as barriers to fluid flow, and may explain the discrepancy between laboratory measurements and field scale observations. This approach can provide estimates for the equivalent permeability, and permeability anisotropy, for stylolite bearing limestone reservoirs worldwide.

title: Saltwater Intrusion as Potential Driver of Phosphorus Release from Limestone Bedrock in a Coastal Aquifer
abstract: An important but often overlooked consequence of saltwater intrusion is the potential increase of groundwater soluble reactive phosphorus concentrations. The phosphorus sorption dynamics of two limestone rocks of different composition were investigated by simulating seawater intrusion over a wide range of mixing ratios between freshwater and saltwater. Both rocks exhibited a logarithmic loss of sorption efficiency in mixtures containing more than approximately 3 mM Cl concentration (100 mg Cl /L; about

title: Megascopic processes reflected in the microscopic realm: sedimentary and biotic dynamics of the Middle Ordovician "orthoceratite limestone" at Kinnekulle, Sweden
abstract: The Middle Ordovician (Dapingian middle Darriwilian) "orthoceratite limestone" is documented in its traditional type area at Kinnekulle in the province of Vastergotland in southern Sweden. Detailed field studies combined with systematic qualitative and quantitative analyses of carbonate microfacies at high stratigraphic resolution show that this suite of cool water carbonate rocks is more variable than is suggested by its overall homogeneous macroscopic appearance. Long term changes in carbonate textures and fossil grain assemblages, together with pervasive rhythmic/cyclic patterns, suggest a strong influence from sea level on microfacies characteristics. Assessment of the results in light of regional facies patterns indicates that the cool water "orthoceratite limestone" behaved much like "model" siliciclastic sedimentary systems, in that carbonate texture varied with depositional depth as particle size of siliclastics does. Carbonate texture thus appears to reflect absolute depth well, whereas grain assemblages record high frequency cycles of changes in both sea level and substrate conditions. A relative sea level curve compiled from the collective data shows excellent agreement with previously published curves based on different proxies. The most important factor for the long term establishment and regional dominance of the "orthoceratite limestone" throughout much of the Early and Middle Ordovician appears to have been a limited terrigenous sediment input to the Baltoscandian paleobasin. Hence, much of the regional facies zonation may reflect distance from weathering sources rather than bathymetric conditions.

title: Inelastic Compaction in High Porosity Limestone Monitored Using Acoustic Emissions: Compaction in Limestone Monitored by AE
abstract: We performed a systematic investigation of mechanical compaction and strain localization in Saint Maximin limestone, a quartz rich, high porosity (37% limestone from France. Our new data show that the presence of a significant proportion of secondary mineral (i.e. quartz) did not impact the mechanical strength of the limestone in both the brittle faulting and cataclastic flow regimes, but that the presence of water exerted a significant weakening effect. In contrast to previously published studies on deformation in limestones, inelastic compaction in Saint Maximin limestone was accompanied by abundant acoustic emission (AE) activity. The location of AE hypocenters during triaxial experiments revealed the presence of compaction localization. Two failure modes were identified in agreement with microstructural analysis and X ray computed tomography imaging: compactive shear bands developed at low confinement and complex diffuse compaction bands formed at higher confinement. Microstructural observations on deformed samples suggest that the recorded AE activity associated with inelastic compaction, unusual for a porous limestone, could have been due to microcracking at the quartz grain interfaces. Similar to published data on high porosity macroporous limestones, the crushing of calcite grains was the dominant micromechanism of inelastic compaction in Saint Maximin limestone. New P wave velocity data show that the effect of microcracking was dominant near the yield point and resulted in a decrease in P wave velocity, while porosity reduction resulted in a significant increase in P wave velocity beyond a few percent of plastic volumetric strain. These new data highlight the complex interplay between mineralogy, rock microstructure, and strain localization in porous rocks.

title: Dispersion and attenuation measurements of the elastic moduli of a dual porosity limestone

title: Tropical limestone forest resilience and late Pleistocene foraging during MIS 2 in the Trang An massif, Vietnam
abstract: In this paper we present a multi proxy study of tropical limestone forest and its utilization by human groups during the significant climatic and environmental upheavals of MIS 2 (29 11.7 kBP) Our data are drawn from new field research within the Trang An World Heritage property on the edge of the Red River Delta, northern Vietnam. Key findings from this study include 1) that limestone forest formations were resilient to the large scale landscape transformation of the Sunda continent at the end of the last glaciation; 2) that prehistoric human groups were probably present in this habitat through out MIS 2; and 3) that the forested, insular, karst of Trang An provided foragers with a stable resource base in a wider changing landscape during the late Pleistocene and into the Holocene. These results have implications for our understanding of the prehistoric utilization of karst environments, and resonance for their conservation in the face of climate and environmental change today.

title: Investigations of a Cretaceous limestone with spectral induced polarization and scanning electron microscopy
abstract: Sara Johansson,1 Charlotte Sparrenbom,2 Gianluca Fiandaca,3 Anders Lindskog,2 Per Ivar Olsson,1 Torleif Dahlin1 and Hakan Rosqvist4 1Division of Engineering Geology, Lund University, P.O. Box 118, SE 22100 Lund, Sweden. E mail: sara.johansson@tg.lth.se 2Department of Geology, Lund University, Solvegatan 12, SE 22362 Lund, Sweden 3Department of Geoscience, Aarhus University, C.F. Mollers Alle 4, DK 8000, Aarhus C, Denmark 4Tyrens AB, Isbergs gata 15, SE 21119 Malmo, Sweden

title: Simulation of an experimental fire in an underground limestone quarry for the study of Paleolithic fires
abstract: Numerous fire marks occur on the walls of the Chauvet Pont d'Arc cave. Dating indicated that some of the fires were contemporary to the Aurignacian. Violent thermal shocks were observed in surprisingly narrow areas of the cave. This raises numerous archaeological questions about the function of the fires; the answers depend on the location of the hearths, and the intensity of the fires. Numerical simulation was used here to provide information about the behaviour of fires in such confined spaces. An underground non archaeological site, in a limestone quarry, was equipped to monitor fires in an environment similar to that of the Megaceros gallery of the Chauvet Pont d'Arc cave. The fire and the movement of heat and smoke in the quarry were simulated by the open source code "Fire Dynamics Simulator (FDS)" Results were validated on wall temperatures recorded behind and above the fire. The thermo mechanical impact of the fire on the rock was simulated with CAST3M software, providing the most probable zones for limestone spalling due to thermal gradients. The validated approach will, in a forthcoming study, be applied to the Chauvet Pont d'Arc cave, in which coupled simulations in the air and in the rock should indicate the location of the hearths and the intensity of the fires that generated the marks.

title: Coupling effect of Fe3+(aq) and biological, nano sized FeS coated limestone on the removal of redox sensitive contaminants (As, Sb and Cr) Implications for in situ passive treatment of acid mine drainage
abstract: Nano sized FeS particles have been shown to improve the adsorption performance in permeable reactive barrier (PRB) technologies that are used to treat acid mine drainage. To investigate the coupling effect of Fe3+ and biological nano sized FeS on removal of redox sensitive contaminants and the permeability of a limestone system, Fe reducing bacteria (FRB) and sulfate reducing bacteria (SRB) were used to form nano sized FeS coatings on limestone grains. For initial acidic solutions containing 0.5 mg/L As(V) Cr(VI) and Sb(V) retardation factors increase from 26, 5 and 7, respectively, in a limestone only (pristine) system to >367, 89 and 9, respectively, in an FeS coated limestone system, and to 345, 367 and 308, respectively, in an FeS Fe3+(aq) system. The permeability coefficient of the FeS coated limestone system is better than that of the pristine limestone system, but declines to two thirds of the pristine limestone system in the presence of Fe3+(aq) possibly due to the formation of secondary ferric hydroxides. XPS analysis suggests that the FeS particles are effective at reducing As(V) Sb(V) and Cr(VI) and removing them from solution. These results demonstrate that FeS particles improve retention of redox sensitive contaminants with and without Fe3+(aq) These new findings give new insights on the coupling effect of redox systems used in PRBs.

title: Mississippian reef development in the Cracoe Limestone Formation of the southern Askrigg Block, North Yorkshire, UK
abstract: The southern margin of the Askrigg Block around Cracoe, North Yorkshire, shows a transition from carbonate ramp to reef rimmed shelf margin, which, based on new foraminiferal/algal data, is now constrained to have initiated during the late Asbian. A late Holkerian to early Asbian ramp facies that included small mudmounds developed in comparatively deeper waters, in a transition zone between the proximal ramp, mudmound free carbonates of the Scaleber Quarry Limestone Member (Kilnsey Formation) and the distal Hodderense Limestone and lower Pendleside Limestone formations of the adjacent Craven Basin. The ramp is envisaged as structurally fragmented, associated with sudden thickness and facies changes. The late Asbian to early Brigantian apron reefs and isolated reef knolls of the Cracoe Limestone Formation include massive reef core and marginal reef flank facies, the latter also including development of small mudmounds on the deeper water toes of back reef flanks. The position of the apron/knoll reefs is constrained to the south (hangingwall) of the North Craven Fault, but it is syn depositional displacement on the Middle Craven Fault that accounts for the thick reefal development. Subsequent inversion of this structure during the early Brigantian caused uplift and abandonment of the reefs and subsequent burial by the Bowland Shale Formation.