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  • 1
    Description / Table of Contents: This book is an exploration of varying approaches to the study of the deposition, diagenesis and stratigraphy of evaporites. The volume includes papers from chemical modellers, who work on the basis of geochemical representations of the formative water bodies, and from basin-wide depositional-stratigraphical modellers, who propose depositional scenarios that are fitted to individual basinal pictures. Until now there have been only a few studies of evaporite formation that explain the characteristic features we observe in the real rock record. This volume is a collection of relevant papers in which these features are integrated in a realistic manner, based on our new understanding of saline water bodies, to the diverse tectonic, chemical and depositional constraints of their individual basins. In additional there are several review articles that offer oversight and extensive referencing of basins worthy of further study. This book is a valuable resource for sedimentologists and stratigraphers looking for an up-to-date reference on evaporite deposits.
    Pages: Online-Ressource (VI, 373 Seiten)
    ISBN: 9781862392328
    Language: English
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  • 2
    Publication Date: 2007-12-19
    Description: The Vena del Gesso' (Gessoso-Solfifera Fm, Messinian) is a 227 m-thick ridge along the western Romagna Apennines (Italy) consisting of up to 16 selenite cycles separated by shales and minor carbonate. The total organic carbon values of these deposits range between 0.0870.016% (gypsum) and 3% (shales). Organic matter is dominated by black debris associated with continental debris. Algae and dynocysts are rare (〈1%). The amount of amorphous organic matter is low but it may reach up to c. 40%. The 87Sr/86Sr of gypsum and carbonate vary from 0.708890 to 0.709024, yielding non-oceanic values with several exceptions that plot within error of coeval oceanic values only in the upper part of the section (from the 6{degrees} bed). The sulphur isotope composition of gypsum range between {delta}34S =+21.8 and +23.7{per thousand} and may represent precipitation of {delta}34S-enriched gypsum due to the fractionation effect or recycling of coeval gypsum with contributions of brine-sediment redox variations. The isotope values of carbonates show a large variability (6.4〈{delta}18O〈+6.05{per thousand}; 14.68〈{delta}13C〈+2.5{per thousand}), suggesting a complex origin by mixing of marine and non-marine waters with a significant contribution of reduced organic matter. These data point to an evaporite basin dominated by continental waters which received significant phases of marine recharge in the upper part together with a marked facies change. Because seawater recharges and a similar facies change are present in other Messinian sections, it follows that we have new possible geochemical and facies markers to correlate the Lower Evaporites across the Mediterranean.
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  • 3
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    In:  Geological Society Special Publication 285: 169-178.
    Publication Date: 2007-12-19
    Description: The Neogene Crotone basin in eastern Calabria contains extensive Messinian evaporite deposits, including thick gypsarenite and halite. The halite deposit reaches a maximum thickness of c. 300 m and in some areas forms relatively small diapirs piercing late Messinian and Pliocene sediments. Halite is strongly modified by folding and recrystallization, but a few primary features are preserved. Four primary halite facies have been recognized: (a) banded halite consisting of folded white and dark bands deposited in a salt pan and/or saline mudflat; (b) white facies, massive halite containing anhydrite nodules, probably formed in a variably desiccating saline lake; (c) clear facies made up of a mosaic of large blocky halite crystals separated by mud, possibly the product of displacive halite growth in a saline mudflat; and (d) breccia facies, a product of dissolution of halite/mudstone/siltstone layers. Residual facies formed from halite dissolution are present as both weld and cap rocks. Weld rocks are thick, undeformed, and composed only of insoluble phases originally included in the salt, whereas cap rocks are thin, strongly sheared and include clasts from the cover rocks.
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  • 4
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    In:  Geological Society Special Publication 285: 1-13.
    Publication Date: 2007-12-19
    Description: This volume grew out of the various oral and poster presentations given during the "Evaporite" session at the International Geological Union conference (2004) in Florence, Italy. It was clear that only a few of the participants or attendees, coming from many countries and various distant parts of the world, were well informed about evaporites outside their immediate area of study, apart from data from the most commonly available literature. Diversity in the languages of publication and the logistical difficulty of making first-hand comparisons acts as a major barrier to study. As a result, the basic concept of evaporites that most geologists have is that deposits are the product of simple, chemically controlled environments and, if evaporitic compounds are chemically the same, then it follows that their lithology and origin are also the same. Based on many studies over the past 30 years, it is now clear that this long-held impression is manifestly untrue. The disparities were very evident in the photographic presentations and descriptions at the 2004 International Geological Congress: the same evaporitic compounds can have distinct and diverse lithology, depositional sources and geological history. They cannot be considered to arise solely from simple, direct chemical origins as explained by a single universal model! This is the same paradigm of sedimentation that functions with other deposits, such as siliciclastics and carbonates, and should also apply to evaporites. In putting this volume together, we realized there were many questions about evaporites from parts of the world not discussed in Florence, despite the large number of participants. Thus, in order to broaden and balance the topics already in our Congress program, we added two additional review papers. One paper that we have added is a chapter covering the many evaporites in the former Soviet Union territory: Russia, Ukraine, Belarus and Moldova. This...
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  • 5
    Publication Date: 2015-05-02
    Description: The large palaeosinkholes located in the NW of Gozo (central Mediterranean Sea, Malta) offer excellent exposures that provide information on the geometry and kinematics of large karst-related collapse structures. Detailed geological analysis of these peculiar palaeosinkholes indicates that deep-seated evaporite dissolution is the most feasible hypothesis to explain their formation, according to the following evidence. (1) Several structures have been formed by progressive foundering of cylindrical blocks with limited internal deformation as revealed by the synsedimentary subsidence recorded by their Miocene sedimentary fill. This subsidence mechanism is more compatible with interstratal dissolution of evaporites than karstification and cave development in limestone formations. (2) The dimensions and deformation style of the palaeosinkholes are similar to those of other collapse structures related to deep-seated dissolution of salt-bearing evaporites. (3) The arcuate monocline associated with some of these collapse structures is also a characteristic feature of subsidence related to dissolution of evaporites. However, no major evaporite formations have been documented so far in the subsurface of the Malta Platform. Supplementary material: Detailed descriptions of the collapse structures of the island of Gozo (Malta, central Mediterranean Sea) are available at www.geolsoc.org.uk/SUP18808 .
    Print ISSN: 0016-7649
    Topics: Geosciences
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  • 6
    Publication Date: 2013-12-14
    Description: A bstract :  The recognition of large clastic sulfate deposits in the Miocene Messinian onshore of the Mediterranean Basin appears to be in contrast with the hypothesis of a complete desiccation as a consequence of the salinity crisis. Below the sea floor the evaporite facies are virtually unknown, but the detailed review of the cores from onshore Israel cutting through the evaporite filling of the marginal canyons in the Levant Basin (Mavqi'im Formation) reveal exclusively clastic sulfate facies. The rocks are graded gypsrudite and gypsarenite associated with laminar and cross-bedded gypsarenite–gypsiltite and shale, whereas no primary, in situ evaporites are present. The clastic facies association is interpreted to have been deposited by subaqueous gravity flows sourced from dismantled selenite rocks originally located eastward and updip of the canyons. The absence of supratidal evaporites suggests that no pronounced sea-level drop can be inferred during the salinity crisis because the presence of the evaporite layers at different elevations along the canyons cannot mark oscillations in sea level, but instead is the result of subaqueous mass-wasting phenomena. These findings indicate that the other ancient canyons described around the Mediterranean Basin may not be necessarily related to a base-level drop due to basinwide desiccation. On the contrary, the widespread presence of clastic evaporites suggests that a water body persisted even during the acme of the salinity crisis. The clastic deposits onshore Israel are the first direct evidence that the widespread Lower Evaporite Unit lying below the floor of the Mediterranean may actually consist of deep-water resedimented evaporites and that one of the primary sources was originally located on the upper margin of the Levant Basin. If this hypothesis is correct, then the Mediterranean Basin may host the largest clastic sulfate deposit in the world.
    Print ISSN: 1527-1404
    Topics: Geosciences
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  • 7
    Publication Date: 2014-02-28
    Description: During the first stage of the Late Miocene Messinian salinity crisis (5.97–5.60 Ma), deposition of sulfates (the Primary Lower Gypsum) occurred in shallow silled peripheral subbasins of the Mediterranean undergoing restricted water exchange with the Atlantic Ocean. Fluid inclusions in Messinian selenite crystals from the Piedmont Basin (northwest Italy) have surprisingly low salinities (average of 1.6 wt% NaCl equivalent), suggesting that parent waters were depleted in Na + and Cl – compared to modern seawater. Modern gypsum from a Mediterranean salt work, in contrast, contains fluid inclusions with elevated salinities that match the normal evaporation trend expected for seawater. The salinity data indicate that the Messinian sulfate deposits from the Piedmont Basin formed from hybrid parent waters: seawater mixed with Ca 2+ and SO 4 2– enriched freshwaters that dissolved coeval marginal marine gypsum. Such mixed parent waters and complex recycling processes should be taken into account when explaining the genesis of other Messinian gypsum deposits across the Mediterranean Basin.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 8
    Publication Date: 2016-10-15
    Description: A general agreement on what actually happened during the Messinian salinity crisis (MSC) has been reached in the minds of most geologists but, in the deepest settings of the Mediterranean Basin, the picture is still far from being finalized and several different scenarios for the crisis have been proposed, with different significant implications for hydrocarbon exploration. The currently accepted MSC paradigm of the ‘shallow-water deep-basin’ model, which implies high-amplitude sea-level oscillations (〉 1500 m) of the Mediterranean up to its desiccation, is usually considered as fact. As a consequence, it is on this model that the implications of the MSC events on the Mediterranean petroleum systems are commonly based. In fact, an alternative, deep-water, non-desiccated scenario of the MSC is possible: it (i) implies the permanence of a large water body in the Mediterranean throughout the entire Messinian salinity crisis, but with strongly reduced Atlantic connections; and (ii) envisages a genetic link between Messinian erosion of the Mediterranean margins and deep brine development. In this work, we focus on the strong implications of an assessment of the petroleum systems of the Mediterranean and adjoining areas (e.g. the Black Sea Basin) that can be based on such a non-desiccated MSC scenario. In particular, the near-full basin model delivers a more realistic definition of Messinian source-rock generation and distribution, as well as of the magnitude of water-unloading processes and their effects on hydrocarbon accumulation.
    Print ISSN: 1354-0793
    Topics: Chemistry and Pharmacology , Geosciences
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  • 9
    Publication Date: 2012-12-21
    Description: : The deposition of varved sedimentary sequences is usually controlled by climate conditions. The study of two late Miocene evaporite successions (one halite and the other gypsum) consisting of annual varves has been carried out to reconstruct the paleoclimatic and paleoenvironmental conditions existing during the acme of the Messinian salinity crisis, ~ 6 Ma, when thick evaporite deposits accumulated on the floor of the Mediterranean basin. Spectral analyses of these varved evaporitic successions reveal significant periodicity peaks at around 3–5, 9, 11–13, 20–27 and 50–100 yr. A comparison with modern precipitation data in the western Mediterranean shows that during the acme of the Messinian salinity crisis the climate was not in a permanent evaporitic stage, but in a dynamic situation where evaporite deposition was controlled by quasi-periodic climate oscillations with similarity to modern analogs including Quasi-Biennial Oscillation, El Niño Southern Oscillation, and decadal to secular lunar- and solar-induced cycles. Particularly we found a significant quasi-decadal oscillation with a prominent 9-year peak that is commonly also found in modern temperature records and is present in the contemporary Atlantic Multidecadal Oscillation (AMO) index and Pacific Decadal Oscillation (PDO) index. These cyclicities are common to both ancient and modern climate records because they can be associated with solar and solar-lunar tidal cycles. During the Messinian the Mediterranean basin as well as the global ocean were characterized by different configurations than at present, in terms of continent distribution, ocean size, geography, hydrological connections, and ice-sheet volumes. The recognition of modern-style climate oscillations during the Messinian suggests that, although local geographic factors acted as pre-conditioning factors turning the Mediterranean Sea into a giant brine pool, external climate forcings, regulated by solar–lunar cycles and largely independent from local geographic factors, modulated the deposition of the evaporites.
    Print ISSN: 1527-1404
    Topics: Geosciences
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  • 10
    Publication Date: 2017-08-08
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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