Modern and Pleistocene polar carbonates occur in East Antarctica in shelf, coast, lakes and marginal to underneath glaciers, associated mainly with glacigene muds, boulder tills and diamictites. Shelf carbonates (in Prydz Bay) are calcitic and unlithified, and consist mainly of sponges, bryozoans, echinoderms, bivalves and diatoms. Coastal carbonates (in the Vestfold Hills) are calcitic and contain faunal assemblages similar to those on the shelf, with calcareous algae, microbial mats, minor peloids and cements. Lake carbonates are aragonitic micrites and peloids. Carbonates close to glaciers (the Løken Moraines) are aragonitic and contain abundant ooids with intragranular fibrous cements. Subglacial carbonates are aragonitic micrites and peloids. Carbonate mineralogy changes from mainly low-Mg calcite in marine shelf to aragonite in brackish to freshwater dominated inland regions.

Antarctic carbonate δ¹⁸O values (4.5 to −47‰ PDB) vary markedly due to frigid temperatures (0 to −2°C) and salinity (0 to 35‰) changes, as a result of meltwater dilution from adjacent glaciers. Their δ¹³C values (−9 to 8‰ PDB) also vary markedly due to exposure to atmospheric CO₂, the circulation of water masses and reaction of carbonate with CO₂ trapped in glacial ice.

The regional distribution of carbonate sediments and their sedimentology, mineralogy, and δ¹⁸O and δ¹³C compositions indicate three types of glacial environments of formation. The first corresponds to a glacial stage and the formation of subglacial and bank carbonates, when the Antarctic ice sheet expanded onto the inner shelves. The second corresponds to interglacial stages and the formation of ice-marginal carbonates, during the retreat of the ice sheet from the inner shelf grounding line and accompanying the discharge of appreciable meltwater. The third corresponds to an interglacial oasis and the formation of coastal carbonates, proximal to distal lacustrine carbonates, and distal subglacial carbonates.

The complete meltdown of the Greenland and Antarctic ice sheets would raise the sea level 65 meters, whereas a partial meltdown only a few tens of meters. Eustatic sea level rates of changes in Greenland since 2003 show a net ice mass reduction of 96 gigatons per year; with this, geologists are called upon to add a historical perspective upon these changes.

Pre-Neogene continental rearrangements occurred at numerous episodes, masking the net effects of eustatic level fluctuations. Glacial advance is prominent during late Precambrian, late Carboniferous and Pleistocene. Greenhouse events and temperature increases are evident during the Devonian and Cretaceous. Paleo-continental landmass positions reveal a direct relationship to icehouse and greenhouse events. The restriction of global oceanic circulation at the equator brings about icehouse events. Absolute rates of change for comparison purposes to the present are currently impossible due to the multivariate effects (1) tectonic plate motion world wide; (2) variations in sedimentary processes; (3) diagenetic change in sedimentary rock; (4) subsidence, on the resultant stratigraphic record.

Since carbonate reefs reach the top of the subsea or photic zone, carbonate reef growth is an ideal indicator of sea level change. Carbonate deposits at the Caribbean — South America plate boundary are a prime example that plate motion can greatly supersede sea level fluctuations. The best areas to use carbonate reef data is along the Florida-Bahamas-Caribbean passive margins of the Atlantic basin, where Neogene tectonics and carbonate deposition were stable. The carbon dioxide levels were much greater above the K/T boundary, creating an environment devoid of significant carbonate buildups. The earliest significant quantitative sea-level rate of change data is derived from wells drilled into stable carbonate platforms of the late Neogene 2–7 Ma, when carbon dioxide levels decreased in the atmosphere. Cores show rates of paleo sea level rise averaging 10 to 20 cm/100yr versus currently between 17–32cm/100yr. The rate increase has nearly doubled within the past 14 years. This increased rate of change in sea-level has been recently highlighted at the 2007 Intergovernmental Panel on Climate Change in Paris, France.

In the past, rapid warming caused extreme increase in eustatic sea level rates of change reflected in geochemical data from carbonate Holocene reef cores from the west side of Barbados Island, drowned reefs off the, Florida coast, and from Bermuda. The measuring sea level changes of 1–2m/100yr are evident from 13,000–17,000 years ago. The warming is attributed to solar irradiance at glacial maximum during the Wisconsinan 14,000–20,000 years before present when sea level was as much as −175 meters lower than today. This lowered sea level evidence is derived from Holocene reefs south of the Great Barrier Reef in Australia. Bluemle (2001) characterizes the Holocene as a sequence of ten or more global scale “little ice ages” fairly irregularly spaced, each lasting a few centuries and separated by global warming events shown from the ice core data. Friedman (2005) noted an overall cooling trend in ocean waters based on Red Sea beach rock geochemical data from 7,000 to 2,000 years ago. Through all the erratic temperature swings over the past 4,000 years geochemical data from Holocene reef cores from Florida show a sea level rise of 12cm/100yr., typical of stable geological and climatological periods.

The Questions remains: Is the current rate change of sea level significant or, just another unanswered anomaly from the cycle curve?

A set of 370 tests of the irregular echinoid speciesEchinocyamus pusillus from 15 European locations (Baltic Sea, North Sea, Atlantic Ocean, Mediterranean Sea), representing a salinity range between 22 and 39% and a variability in annual average temperatures between 9.5 and 20°C, were analyzed for their Mg content by X-ray diffraction. For 50 of these samples — from all sampled sites — the δ¹⁸O and δ¹³C values were measured additionally. The data are discussed in the context of physiological and environmental (salinity, temperature) control.

The Mg content of the skeletons strongly correlates with the average annual temperature but not with salinity while the δ¹⁸O values seem to be influenced by physiological as well as environmental parameters. The oxygen and partly also the carbon isotope data are clearly correlated with the salinity, reflecting the dominant influence of the isotopic composition of the ambient seawater. On the other hand, for samples from biotopes with constant salinity but varying temperatures the temperature dependency on¹⁸O fractionation is clearly monitored in the skeletons. However, for most of the non-Mediterranean samples the measured δ¹⁸O values are more positive than the expected equilibrium values, probably as a result of vital effects. The degree of this disequilibrium decreases with increasing temperature, with sea urchins from the warmest marine environments of the eastem Mediterranean Sea precipitating their skeletons in or near equilibrium.

Easier access to most of spectacular sedimentological features of Midyan region along the northern coast of Red Sea has enabled a more detailed examination of the Miocene succession that could not have been possible except from deep subsurface drilling. The Wadi Waqb member of Jabal Kibrit Formation hosted the Wadi Waqb reservoir in this region. In this study the microfacies of the exposed discontinuous fringing rhodolith and coral reef complex of Wadi Waqb member that seated unconformably on steep cliffs of granitic basement are investigated. Four microfacies were recognized as follows: MF-1) Quartz-peloid packstone and Red algal bioclastic boundstone, MF-2) Bioturbated rhodophyte-bioclastic grainstone, MF-3) Calc-allochemic sandstone, and MF-4) Intraclastic wackestone.

Microfacies 1 and 2 are considered to be deposited at the upper and mid reef front. The depositional environment of the MF-3 is considered to have occurred in periodical flash floods and microfacies 4 is considered to be a lower reef front deposit. Careful microfacies analysis of mixed reefal carbonate and siliciclastic deposits provides a better understanding of how and why carbonate microfacies develop.

This paper presents a model that integrates sequence stratigraphic concepts with a fabric and growth form classification of Smackover microbial buildups to aid in understanding the distribution of reservoir quality in the updip basement ridge play of southwest Alabama. Microbial growth forms and fabrics, early diagenetic processes, and resulting reservoir quality are all ultimately controlled by the rate of relative sealevel change, position of sea level with respect to exposed Paleozoic basement, and position in an inner ramp setting. The microbial classification divides fabrics and growth forms into five “types,” which developed in response to changes in water energy, sedimentation rate, and substrate. Layered thrombolite with characteristic mm/cm-scale crypts characterize Type I buildups. Reticulate and “chaotic” thrombolite comprise Type II buildups. In the updip basement ridge play, the Smackover sea did not flood the Paleozoic basement until deposition of the sediments associated with the late transgressive systems tract. Layered and reticulate thrombolite buildups (Types I and II) grew directly on Paleozoic basement and formed in reponse to late transgressive systems tract catch-up conditions when sedimentation rates were low and water energies were moderate to high. Both Type I and II buildups occur on low and high relief basement structures. Type III buildups are characterized by dendroidal thrombolites. On low relief basement structures, dendroidal thrombolite buildups (Type III) typically overlie Type I and II buildups. Type III buildups are absent on high relief structures. Dendritic thrombolites grew in early highstand systems tract keep-up conditions when sedimentation rates were slightly elevated and water energy low. These conditions occurred on the tops of low-relief basement structures associated with early highstand systems tract deposition. Type IV microbialite are composed of isolated stromatolitic crusts that acted as binders to Type V oncoidal packstone/grainstones that grew on soft to firm substrates in high-energy conditions. Abundant in the late highstand systems tract deposits, Type IV (isolated crusts) and V (oncoid) microbialite are found in upper Smackover shoal, lagoon, and tidal flat facies.

Classification of microbial types is significant to hydrocarbon exploration and production in southwest Alabama. Types I, II, and III buildups are the best fabrics for productive reservoirs. Of these, Type III buildups are the highest quality reservoir rocks. Dolomitized reticulate and dendritic fabrics result in well-connected intercrystalline and vuggy porosity. Type IV and V microbialite are poor reservoir rocks because Type IV forms are often isolated, and the moldic porosity associated with Type V oncoids are typically not well connected.

Extensive precipitation of aragonite and high-Mg calcite (12–14% MgCO₃) cements in the intertidal sediments of the Gulf of Aqaba, Egypt and the Arabian Gulf, Qatar results in the formation of dominant beachrock exposures. The 20–60 cm thick beachrocks in both areas are parallel to the shoreline and slope gently seaward. The 14 C dating values show that the cement of the Gulf of Aqaba beachrock (2470±60y) are rather older than those of the Arabian Gulf (1360±45y). Framework grains in the Gulf of Aqaba beachrock are moderate to unsorted coarse terrigenous rock fragments, which differ than the unsorted carbonate particles of the Arabian Gulf beachrock. Carbonate cements in both the Aqaba and the Arabian Gulfs display the same architecture, which comprises: 1) thin isopachous crust made up of high-Mg calcite mosaics and/or aragonite needles that surround grains and 2) intergranular cryptocrystalline high-Mg calcites, which fill the rest of the pores. Minor dolomite mosaics may associate with the intergranular cement. The co-existence of the aragonite needles, of the isopachous crust, with the micritized grains and micritic envelopes is evidence that marine phreatic processes are dominant in the intertidal zone and that lithification has started in this zone. The bi-mineralic composition of the isopachous crust in the Aquaba beachrock is attributed mainly to kinetic factors (i.e. the rate of supply of carbonate ions) and to the composition of the substrate and/or organic control in the beachrock of the Arabian Gulf. Some physico-chemical, kinetic, hydrologic and biologic factors are believed to be effective in controlling the precipitation rates of the isopachous cement. The oxygen and carbon isotopic composition of the intergranular high-Mg calcite cement of the Aqaba Gulf (+2.0 to −1.6 and +2.9 to +4.4‰ PDB respectively) is in accord with their precipitation in equilibrium with marine water. However, the relatively depleted δ¹⁸O (−0.5 to −3 ‰ PDB) and δ¹³C (+0.3 to 2.2 ‰ PDB) values of the intergranular high-Mg calcite cement of the beachrock of the Arabian Gulf is attributed to extraneous source of bicarbonate ions. The minor dolomite rhombs are formed directly from seawater within microenvironments created in response to the release of Mg²⁺ ions to the pore water following the partial dissolution of some high-Mg calcite carbonate particles.

Fluorescent dye tracer breakthrough curves (TBCs) obtained from quantitative traces in karst flow systems record multiple processes, including advection, dispersion, diffusion, mixing, adsorption, and chemical reaction. In this study, TBCs were recorded from small, bench-scale physical models in an attempt to isolate, understand, and quantify some of these processes under full-pipe flow conditions. Dye traces were conducted through a suite of geometries constructed out of Pyrex glass. These geometries consisted of (1) linear conduits, of varying length and diameter, (2) single and dual mixing chambers, and (3) a single chamber with an immobile region. Each glass system was connected to a constant flow apparatus. Dye was then injected with a syringe, allowed to flow through the system, and be naturally or artificially mixed in the process. Solute breakthrough was recorded in a scanning spectrofluorophotometer and the resulting TBC was analyzed. Independent variables examined in each of the three settings were discharge (Q) and dye concentration (C_o). Artificial mixing rates (R_M), induced by magnetic stirrers in settings (2) and (3), were also considered. Initial runs varied Q from 0.75 to 1.25 mL/s, with constant R_M ranging from 0 to 360 revolutions per minute (rpm). Preliminary data yield realistic-looking breakthrough curves with steeply rising leading edges, a peak, and an asymmetric, exponential tail. Analysis of laboratory variables with respect to hydraulic parameters extracted from each TBC suggests that discharge and mixing rate alone can differentiate conduit complexity at the laboratory scale.

Micritic limestones form part of cyclic alternations of limestones- marls/shales in many offshore facies of epeiric seas and their origin has been, and still is, subject to controversy. As an example from the offshore ramp facies, the origin of Lower Lias micritic limestones of SW Britain has been investigated. The very continuous limestone beds show many petrographic and geochemical similarities to isolated nodules, which occur within the marls and are interpreted as being of diagenetic origin. Displacive growth of the microspar crystals was the most important process that occurred during the near-surface formation of the central part of limestone beds, but their edges formed during later burial. The carbon isotopic values (+1.1‰ to −3.4‰ (PDB)) of the central part of the limestone beds and nodules suggest a predominantly marine source for the carbonate, whereas bacterial sulphate reduction played a minor part in their cementation. The oxygen isotopic values (−1.5‰ to −7.2‰ (PDB)) of the characteristic limestone beds, and nodules suggest their formation (cementation/recrystallization) commenced at shallow depth but continued during progressive burial. The microspar crystals of the matrix of the limestones show rare aragonitic relics or pitted surface. Aragonitic fossil remains are rare in these offshore facies and this is in contrast to their abundance in the laterally equivalent shallow marine facies (Sutton Stone). It is suggested that early submarine dissolution of aragonitic components (lime mud and bioclasts) was important in providing carbonate for cementation of the limestones. Early submarine dissolution may have been a common process in epicontinental epeiric settings with low deposition rates, and as the result long residence time in the early diagenetic zones.

The Karun River is one of the most important waterways in Iran and the quality level of its waters is very important for all the communities living around it. The salinity of river waters increases and the water quality decreases while it passes through the four km long valley consist of Gachsaran geological formation (mainly gypsum and halit), in the Ambal ridge area. This ridge is located some 5 km upstream of the Gotvand dam (under construction), which in the future will be inundated. In this section of the river, water chemistry suddenly evolves from Ca-HCO₃ type with TDS of ~0.4 g/l to Na(Ca)-Cl(SO₄) type with TDS of ~1.5 g/l, possibly due to mixing, carbonates precipitation and dolomitization. These variations suggest that saline water mixed with the river water extensively in the Ambal ridge area. Two hypotheses are suggested for the origin of the saline waters: first, in situ dissolution of halite and gypsum units of exposed Gachsaran Formation of the nearby area could produce saline ground-water flow into the river, and second, the intrusion of Karun River water itself through fractures of evaporite layers at location, where it first comes in contact with the Ambal area and in consequence, dissolution of halite and gypsum by the water, which discharge into the river via a number of exposed and underwater springs in the ridge. Calculations indicate that the average annual saline water seepage required for the change of the chemical composition is ~0.24% of the total river flow rate. Water balance calculations suggest that the required catchment area for the saline ground-water flow should be >300 km², much larger than the Ambal area itself. However, this excess area almost is exist in a closed by plain, the impermeable marl layers in the Gachsaran Formation restraint the flow of groundwater and suggest that the first hypothesis is less likely.