Flank Margin Cave Development in Telogenetic Limestones of New Zealand

Coastal limestone outcrops, typically with advanced levels of diagenetic maturity (i.e., are telogenetic carbonates), were ex­amined on NorthIsland (Raglan Harbour, Kawhia Harbour, Napier, and Waipu Cove) and SouthIsland (Pohara, Paturau River, Punakaiki, Kakanui, and Kaikoura), New Zealand, to de­termine if flank margin caves, produced by mixing dissolution, were present. In coastal settings, caves in carbonate rock can be the outcome of pseudokarst process, primarily wave erosion, as well as karst processes not associated with freshand sea-water mixing suchas epikarst features and conduit-flow stream caves. Flank margin caves were successfully differentiated from other cave types by the following criteria: phreatic dissolutional mor­phologies at the wall rock and chamber scales; absence of high-velocity, turbulent-flow wall sculpture and sediment deposits; and lack of integration of adjacent caves into a continuous flow path. The active tectonics of New Zealand creates a variable sea-level situation. The relatively short time of sea-level stability lim­its the size of the New Zealand flank margin caves compared to tectonically-stable environments, suchas the Bahamas, where glacioeustasy alone controls sea-level stability. Uplift events can be identified as slow and steady when the flank margin caves are uniformly elongated in the vertical direction, and episodic when the flank margin caves show widening and tube develop­ment at discrete horizons that cut across rock structure. New Zealand flank margin caves contain information on uplift dura­tion and rates independent of other commonly used measures, and therefore can provide a calibration to other methods

Quaternary glacial cycles: Karst processes and the global CO2 budget

Extensive research has been conducted investigating the relationship between karst processes, carbonate deposition and the global carbon cycle. However, little work has been done looking into the relationship between glaciations, subsequent sea level changes, and aerially exposed land masses in relation to karstic processes and the global carbon budget. During glaciations sea-level exposed the world’s carbonate platforms. With the sub-aerial exposure of the platforms, karst processes can occur, and the dissolution of carbonate material can commence, resulting in the drawdown of CO2 from the atmosphere as HCO3−. Furthermore, the material on the platform surfaces is primarily aragonite which is more readily soluble than calcite allowing karst processes to occur more quickly. During glaciations arctic carbonates and some of the temperate carbonates are blanketed in ice, effectively removing those areas from karst processes. Given the higher solubility of aragonite, and the extent of carbonate platforms exposed during glaciations, this dissolution balances the CO2 no longer taken up by karst processes at higher latitudes that were covered during the last glacial maximum The balance is within 0.001 GtC / yr, using soil pCO2 (0.005 GtC/yr assuming atmospheric pCO2) which is a difference of <1% of the total amount of atmospheric CO2 removed in a year by karst processes. Denudation was calculated using the maximum potential dissolution formulas of Gombert (2002). On a year to year basis the net amount of atmospheric carbon removed through karstic processes is equivalent between the last glacial maximum and the present day, however, the earth has spent more time in a glacial configuration during the Quaternary, which suggests that there is a net drawdown of atmospheric carbon during glaciations from karst processes, which may serve as a feedback to prolong glacial episodes. This research has significance for understanding the global carbon budget during the Quaternary.Keywords: Karst, Global Carbon Budget, Quaternary, Last Glacial Maximum, Carbonate Dissolution.DOI: 10.3986/ac.v42i2-3.66

Blow Hole Cave: An Unroofed Cave on San Salvador Island, the Bahamas, and its Importance for Detection of Paleokarst Caves on Fossil Carbonate Platforms

Prispevek obravnava podobnosti v razvoju krasa kvartarne karbonatne platforme na otoku San Salvador in devonske karbonatne platforme na platoju Krásná na Moravskem. Za obe območji so značilne jame, katerih nastanek lahko razložimo s "flank margin" modelom in so nastale v območju sladkovodnih leč med obdobji relativno visoke morske gladine, v času relativno stabilne halokline, kar potrjujejo različne študije jamskih zapolnitev. V obeh primerih so jamske sedimentne zapolnitve genetsko primerljive - obalni in eolski sedimenti ter breče.The comparative study of a Quaternary carbonate platform (San Salvador Island, the Bahamas) and a Devonian Carbonate Platform (Krásná Elevation, Moravia) indicates a great similarity in karst evolution. Caves on both sites are interpreted as flank margin caves associated with a freshwater lens and halocline stabilised during sea-level highstands. The sedimentary fill of both caves is genetically comparable - beach and aeolian sediments with bodies of breccias

Geology of New Providence Island, Bahamas: A Field Trip Guide

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Geology of Cat Island, Bahamas: A Field Trip Guide

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Pleistocene and Holocene Carbonate Environments on San Salvador Island, Bahamas: A Field Trip Guide

Although isolated and small in size, San Salvador Island is in many ways a unique place - an all carbonates setting on a small, tectonically stable platform, surrounded by deep oceanic waters, and an historical footnote as the widely accepted first landing site of Christopher Columbus in the New World in 1492. Columbus\u27 stay here was brief, and the major events of subsequent history largely have passed San Salvador by. This is not a tourist island; the natural beauty, floras, and faunas of the Bahamas are well preserved here. The overview theme of this series of field excursions on San Salvador will be interpretation of paleodepositional environments for the well-exposed Pleistocene and Holocene carbonate rocks that cap the island and recognition of modem analogues from the varied carbonate environments found on the island and its surrounding shelf. Questions of sea level history, diagenetic change, and the surficial processes operating on carbonate island terranes also will be considered. Our trip will begin with a low-attitude overflight to view features of the main Bahama platform enroute to San Salvador, which lies just beyond the eastern edge of the platform. The field trip leaders all have been working on San Salvador and elsewhere in the Bahamas for the past decade. We have experienced the good and the bad - a pleasant tropical climate, warm and alive marine waters, a generally unspoiled setting, and the friendly Bahamian people, along with sometimes fierce no-see-um attacks, sun-burnt skin, and unexpected soakings from tropical storms. Throughout, the experiences have been rewarding and the challenges of geologic interpretation great. We look forward to sharing some of our findings and experiences with you. Welcome to the Bahamas and San Salvador Island! See other Smith authored Field Trip Guides of Gerace Research Centre

Geology of Rum Cay, Bahamas: A Field Trip Guide

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Performance of the LHCb vertex locator

The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7 mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 μm is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n+-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 μm for translations in the plane transverse to the beam. A primary vertex resolution of 13 μm in the transverse plane and 71 μm along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 μm is achieved for particles with transverse momentum greater than 1 GeV/c

Precision luminosity measurements at LHCb

Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy √s. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for √s = 2.76, 7 and 8 TeV (proton-proton collisions) and for √sNN = 5 TeV (proton-lead collisions). Both the "van der Meer scan" and "beam-gas imaging" luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves significantly the consistency of the results. For proton-proton interactions at √s = 8 TeV a relative precision of the luminosity calibration of 1.47% is obtained using van der Meer scans and 1.43% using beam-gas imaging, resulting in a combined precision of 1.12%. Applying the calibration to the full data set determines the luminosity with a precision of 1.16%. This represents the most precise luminosity measurement achieved so far at a bunched-beam hadron collider