History of Paleozoic Salt Accumulation
Abstract
This translation of the Russian (1978) edition constitutes an elaboration and continuation of the 1974 monograph Palaeozoic salt formations of the world (Moscow/Nedra Press). The present work deals with the distribution and number of Palaeozoic evaporite sequences and basins, the stratigraphic position of evaporites and stages of evaporite accumulation, the areal extent and volume of evaporites, epochs of intense evaporite accumulation, palaeogeography of continents, and palaeoclimatic zonation of evaporite sedimentation.R.A.H.
Chapters (5)
... These are mainly associated with the specificities of the multidimensional free-energy landscapes, including local minima corresponding to sub-conformations of each anomer that are in fast equilibrium with the main isoforms corresponding to the four detected NMR lines. (2) to the four anomer temperature series (see Table 1). Dashed lines: pure water, solid lines: Hadean model water. ...
... As a consequence, our analysis predicts that a series of population inversions between the high-energy species β−furanose and the two low-energy ones, α−pyranose, should occur Table 1: Thermodynamic parameters describing the equilibrium of D-ribose isomerisation in solution at fixed temperature and pressure as estimated by fitting the equilibrium theory (2) to 13 C NMR data. ...
... In our model, the thermal equilibrium scenario corresponds to two isolated boxes, each reaching thermal equilibrium at a separate temperature. Mathematically, this corresponds to the limit k D → 0, Da ∝ k −1 D → ∞, the steady-state populations reducing to their respective equilibrium expressions (see Eqs. (2) in the main text), ...
The exclusive presence of -D-ribofuranose in nucleic acids is still a conundrum in prebiotic chemistry, given that pyranose species are substantially more stable at equilibrium. However, a precise characterisation of the relative furanose/pyranose fraction at temperatures higher than about 50C is still lacking. Here, we employ a combination of NMR measurements and statistical mechanics modelling to predict a population inversion between furanose and pyranose at equilibrium at high temperatures. More importantly, we show that a steady temperature gradient may steer an open isomerisation network into a non-equilibrium steady state where furanose is boosted beyond the limits set by equilibrium thermodynamics. Moreover, we demonstrate that nonequilibrium selection of furanose is maximum at optimal dissipation, as gauged by the temperature gradient and energy barriers for isomerisation. The predicted optimum is compatible with temperature drops found in hydrothermal vents associated with extremely fresh lava flows on the seafloor.
... As the osmolarity of the present-day ocean is 1.09Osm, whereas the osmolarity of blood serum of land vertebrates remained nearly constant (~0.3Osm). A corollary of the dynamic ocean hypothesis is that the salinity of oceans is gradually increasing [51][52][53][54][55][56][57][58][59]. Salinity changes of the sea over geological ages provide evidence for a dynamic osmolytesystem against a persisting general geochemical balance. ...
... Evaporite deposits: Rising Seabed's cause obstruction, limited flow, loss of contact of inner shallow seas to the ocean. Evaporite deposits could have temporarily decreased ocean salinity [56][57][58]. In agreement with the opinion of Holland [11] the salt extraction probably did not decrease significantly the global salinity of sea. ...
... These basins are separated from neighbouring structures by faults, while anticlinal folds separate them from each other. The flow of sea-water occurred mainly from the North [9]. The formed halogen series of the Solikamsk trough refers to the Irene Horizon of the Kungurian age of the lower Permian. ...
... It is thought that during the crystallization of potassium salt in the Middle Famennian stage of the Late Devonian epoch the salt basin was shallow. The inflow of sea water was thought to come mainly from the Dnieper-Donets Basin [9], [10]. The brines coexisting with the salts are characterized by their acidic consistency (рН 4,5-7), high mineralization (310-496 g/dm3) and the evolution of the whole mixture from calcium chloride to potassium chloride due to the degassing of inner magmatic outflows during the process of the rift structure's formation [11]. ...
... Major evaporite basins with potash salts deposits, their volume and chemical character, compilation of various sources, repeated after Hardie (1990), and Vysotskii et al. (1986), and supplemented (after Hardie, 1996;Harville and Fritz, 1986;Hryniv et al., 2007;Land et al., 1995;Lowenstein and Spencer, 1990;Petrychenko et al., 2005Petrychenko et al., , 2012Rahimpour-Bonab et al., 2007;Talbot et al., 2009b;Timofeeff et al., 2006;Valyashko, 1962;Warren, 2006) and carnallite as the major components (Table 10; Zharkov et al., 1978). In the upper half of Permian, that is, from Kungurian to Tatarian, the chloride sedimentation was accompanied by sulfate deposition (Zharkov, 1981). The Mesozoic potash evaporites are again dominantly of the chloride type, whereas in Neogene, the K-Mg sulfate salts appeared again in the geologic record together with the chloride type (Sonnenfeld, 1984). ...
... Two periods that lasted $ 40 My were recognized in the Phanerozoic, lacking any record of marine saline giants: in Ordovician (Zharkov, 1981) and between the Upper Coniacian and the end of Paleocene (Sonnenfeld, 2000). Ordovician is the only Phanerozoic system without recognized potash evaporites (Goncharenko, 2006). ...
... Plutonism in the New England Appalachians peaked 380 Ma ago (Osberg 1983(Osberg , 1988 (Fig. 14). It seems that the Acadian colüsion of Europe and North America (north of New York) was distinctly earlier than Zharkov (1981Zharkov ( ,1984, Witzke (1990). ...
... The Pridolian salt stage is known from North America but not from Eurasia, whereas the Early Carboniferous saltbearing stage is established in Eurasia but not in North America. Eifelian sulfates were deposited in North America and Europe, Givetian sulfates mostly in Europe, Visean ones in North America (Zharkov 1981(Zharkov , 1984). ...
... Plutonism in the New England Appalachians peaked 380 Ma ago (Osberg 1983(Osberg , 1988 (Fig. 14). It seems that the Acadian colüsion of Europe and North America (north of New York) was distinctly earlier than Zharkov (1981Zharkov ( ,1984, Witzke (1990). ...
... The Pridolian salt stage is known from North America but not from Eurasia, whereas the Early Carboniferous saltbearing stage is established in Eurasia but not in North America. Eifelian sulfates were deposited in North America and Europe, Givetian sulfates mostly in Europe, Visean ones in North America (Zharkov 1981(Zharkov , 1984). ...
... While evaporite deposition is going on, a large fraction of the sulphate in the affected seawater is precipitated (90% by the beginning of the halite facies: Holser, 1979, p. 245). Consequently, removal of sulphate from the ocean has been highly episodic (Zharkov, 1981;Holser et al., 1980). ...
... (1983), to give estimates of the present surviving masses of the two reservoirs for each geological period. Table 2.2 shows our own estimates of the mass of sulphate surviving (mainly as anhydrite) in giant evaporites (Holser et a l ., 1980;Zharkov, 1981); alternatively one could take the compilation of Migdisov e t a l. (1983, Table 2.17; note that they converted volumes as gypsum rather than anhydrite). ...
... The salt extraction from evaporite deposits could have an effect on the decrease of ocean salinity [14]. Large reservoirs of salt stored in brines in the deeply burried sediments fueled the speculation that salinity of the ocean could have changed through time [15][16][17]. Others thought that evaporite salt deposits could not have decreased the salinity more than a few parts per thousand [18,19]. ...
... In addition, evaporite deposits have remarkable paleogeographic implications because they were generally formed in mid-to low-latitude (Álvaro et al., 2000;Hay et al., 2006). The stratigraphic records of evaporite deposits span from the Proterozoic to the Cenozoic (Zharkov, 1981;Blättler et al., 2018). Especially in the Early Cambrian period, large-scale evaporite deposits were distributed worldwide (Mattes and Morris, 1990;Warren, 2010;Evenick, 2021) and most prominent in Asia (Wang et al., 2013). ...
Evaporites are climate-sensitive sedimentary deposits with event stratigraphic, paleogeo-graphic, and paleoenvironmental significance. The Early Cambrian is characterized by early evolution of animal and extensive evaporite deposits at the end. Widespread evapor-ite deposits were developed in the lower Cambrian succession in the North China Craton (NCC), which could provide critical constraints on the age of evaporite-bearing strata, the reconstruction of paleogeographic evolution, and the paleoenvironmental change of the NCC during the Early Cambrian. In this study, we systematically synthesized the geographical and stratigraphic distributions of the Early Cambrian evaporite deposits in the NCC based on field collections and published data. The results show that the Early Cam-brian evaporite deposits in the NCC mainly include gypsum, halite pseudomorph, and gyp-sum breccia. They have been found in two sets of reddish layers and geographically distributed in the Jiao-Liao-Xu-Huai region and western Henan region. Integrated evidence of biostratigraphy, chemostratigraphy, and detrital zircon chronology constrains the age of these evaporite deposits within the Cambrian Series 2, Stage 4 (ca. 514-509 Ma). Consequently , these late Early Cambrian evaporite deposits represent drought events that can act as regional event stratigraphic markers to constrain the age of the evaporite-bearing strata near the Great Unconformity and also suggest that the paleogeographic position of the NCC in the Cambrian Stage 4 may be located between 20°N-30°N near the western Gondwana with northwest-southeast orientation. Additionally, the hot-arid paleoclimate evidenced by evaporite deposits may be the environmental factors for the decline of ben-thic organisms in the NCC in the late Early Cambrian.
... Gypsum (CaSO 4 Á2H 2 O) accounts for approximately 20% of the minerals in giant salt deposits formed via the evaporation of seawater throughout Earth's history (Zharkov, 1981;Warren, 2006 dissolved ions of seawater (Stumm and Morgan, 1996). By generating fluxes of sulfate and calcium to and from the ocean, continental gypsum weathering and marine gypsum deposition contribute in regulating ocean chemistry (Spencer and Hardie, 1990;Hardie, 1996;Hansen and Wallmann, 2003;Wortmann and Paytan, 2012;Prince et al., 2019;Turchyn and De Paolo, 2019), as well as atmosphere oxygenation, atmospheric pCO 2 and climate Wortmann and Paytan, 2012;Halevy et al., 2012;Shields and Mills, 2020) on geological time scales. ...
Gypsum makes up about one fifth of giant salt deposits formed by evaporation of seawater throughout Earth’s history. Although thermodynamic calculations and precipitation experiments predict that gypsum precipitates when the salinity of evaporating seawater attains about 110 g kg⁻¹, gypsum deposits of the Mediterranean Salt Giant often bear the geochemical signature of precipitation from less saline water masses. Addressing this geochemical riddle is important because marine gypsum deposition and continental gypsum erosion affect the global carbon cycle. We investigated gypsum deposits formed in the marginal basins of the Mediterranean Sea during the Messinian Salinity Crisis (about 6 million years ago). These often bear low-salinity fluid inclusions and isotopically light crystallization water, confirming previous published reports that the Mediterranean Salt Giant harbors low-salinity gypsum deposits. A geochemical model constrained by fluid inclusion salinity and isotope (⁸⁷Sr/⁸⁶Sr, δ³⁴SSO4, δ¹⁸OH2O, δDH2O) measurements excludes that Ca²⁺- and SO4²⁻-enriched continental runoff alone provides the trigger for gypsum precipitation at low salinity. We propose that, concurrent with the prevalent evaporative conditions and with Ca²⁺- and SO4²⁻-bearing runoff, the biogeochemical sulfur cycle is capable of producing a spatially-restricted and temporally-transient increase of Ca²⁺ and SO4²⁻ within benthic microbial mats, creating local chemical conditions conductive to gypsum precipitation. This hypothesis is supported by the presence of dense packages of fossils of colorless sulfur bacteria within gypsum in several Mediterranean marginal basins, together with independent geochemical and petrographic evidence for an active biogeochemical sulfur cycle in the same basins. Should this scenario be confirmed, it would expand the range of environments that promote marine gypsum deposition; it would also imply that an additional, biological coupling between the calcium, sulfur and carbon cycles exists.
... Fluid inclusion study demonstrates that the concentration of NaCl exceeds current levels in both Archaean seawater and hydrothermal fluid. Zharkov (Zharkov 1981) supported an Archaean sea of 1.2 times current salinity, inferring lacking complexity of biological evolution; this was refuted by Knauth (Knauth 1998), who advocated an ocean at least 1.6 times as saline as the modern. de Ronde et al. (de Ronde et al. 1997) conducted detailed fluid inclusion studies in Barberton greenstone belt ironstones to assign ionic concentrations to the water in which those formed. ...
The implicit objective of this thesis was to bridge the wide gap that exists between the various domains involved in origins of life studies, and bring them together under one larger domain of stochastic systems chemistry. The introductory chapter of the thesis appreciated and accentuated this inherent interdisciplinarity, with relevant examples, essential to origins of life studies. Furthermore, the chapter contextualised the experimental facets that have contributed to the framework of the thesis. The sources of the starting materials required for the origins of life were expanded upon, including the endogenous and the exogenous materials. The contemporary models of origins of life in the literature were discussed from the context of experiments, theory and computer models, and the limitations of the models involving the lack of early Earth-representative environments have been evaluated. Furthermore, compelling arguments were put forth to encourage experimentation that is inclusive of realistic geological settings. The subsequent chapters discussed the settings for prebiotic chemistry within this geological framework. Adhering to the proposed new paradigm, three distinct yet innately linked experiments were proposed and undertaken – the Photochemistry on the International Space Station experiment (PSS), the inorganic hydrogel environment experiment and studies involving mineral-influenced formose reaction.
... As chemical deposits, these evaporites are direct recorders of the chemistry of ancient marine-derived brines (e.g., Babel and Schreiber, 2014), whereby variations in ocean chemistry are reflected in changes in the depositional records and sequences of Mg-K salt deposits. These vary between the chloride type, composed mainly of sylvite and carnallite (Table 1), and the sulfate type, characterized by MgSO 4 -rich minerals (e.g., Zharkov, 1981;Hardie, 1991;Lowenstein et al., 2001;Babel and Schreiber, 2014). The sequence of marine Mg-evaporite minerals that precipitate along the course of evaporation depends not only on the chemical composition of the parent seawater, but also on the degree of enclosure of the basin, the precipitating brine's temperature, whether or not continuous reaction with the already precipitated salts is maintained, and if additional reactions within the evaporitic basin take place (e.g., Eugster et al., 1980;Harvie et al., 1980;McCaffrey et al., 1987;Shalev et al., 2018b). ...
Marine Mg-evaporites are a small oceanic sink of magnesium, precipitating only from extremely evaporated brines. The isotopic composition of Mg in seawater, δ²⁶Mgseawater, has recently been shown to be an effective tool for reconstructing the Mg budget of the modern and past oceans. However, estimations of the Mg isotope fractionation between the Mg-evaporites and their precipitating solution are required for full quantification of the isotope effect of the evaporitic sink on δ²⁶Mgseawater, as well as for utilizing ancient evaporitic sequences as an archive for past δ²⁶Mgseawater. Here, we estimate the Mg isotope fractionation between Mg-evaporites and modern marine-derived brine along the course of seawater evaporation, up to degree evaporation of >200. The sequence of Mg-salts included epsomite (MgSO4∙7H2O), kainite (KMgClSO4∙3H2O), carnallite (KMgCl3∙6H2O), kieserite (MgSO4∙H2O) and bischofite (MgCl2∙6H2O).
The following isotope fractionation values, either negative or positive, were calculated from the isotope difference between the salt and its precipitating brine, and from the evolution of δ²⁶Mg in the brine throughout the evaporation: Δcarnallite-brine= +1.1‰, Δepsomite-brine= +0.59‰, Δbischofite-brine= +0.33‰, Δkieserite-brine= -0.2‰ and Δkainite-brine= -1.3‰. Magnesium isotopic compositions determined on minerals from different ages in the geological record corroborate well these results. Due to precipitation of multi-mineral assemblages having isotope fractionation values of opposing signs, the δ²⁶Mg value of the brine changes only slightly (<0.5‰) throughout the evaporation path, despite the considerable Mg removal (>50%). The isotope fractionations are shown to correlate with the number of water molecules coordinated to the Mg²⁺ and with Mg-O bond length in the mineral lattice.
Given these isotope fractionations, it is calculated that a volume of 0.4∙10⁶ – 0.8∙10⁶ Km³ of a mono-mineral assemblage of kainite or carnallite needs to precipitate in order to change seawater δ²⁶Mg by only 0.1‰. This huge volume is by far larger than the volume of these minerals known to date in the global geological record. Therefore, it is concluded that the impact of Mg-evaporites formation on δ²⁶Mgseawater has been insignificant since the Proterozoic. The results of this study suggest that the Mg isotopic composition of Mg-evaporites preserved in the geological record of evaporitic basins may be used to: 1) Quantify geochemical processes that fractionate Mg-isotopes within these basins, such as dolomitization; and 2) Complete the secular variations curve of the marine δ²⁶Mg record using basins with well-established evaporitic sequences.
... As chemical deposits, these evaporites are direct recorders of the chemistry of ancient marine-derived brines (e.g., Babel and Schreiber, 2014), whereby variations in ocean chemistry are reflected in changes in the depositional records and sequences of Mg-K salt deposits. These vary between the chloride type, composed mainly of sylvite and carnallite (for compositions see Table 1), and the sulfate type, characterized by MgSO 4rich minerals (e.g., Zharkov, 1981;Hardie, 1991;Babel and Schreiber, 2014). ...
https://doi.org/10.1016/j.gca.2018.09.003
Extreme evaporation experiments of modern seawater, up to a degree of evaporation (DE) of 870 on Li scale and brine density of 1.40 g∙ml-1 were conducted under controlled semi-natural conditions. This DE is well within the bischofite facies and, to the best of our knowledge, is the highest experimental DE ever reported. During the experiments, brine temperature varied between ~20°C and ~40°C with few excursions to higher temperatures, thereby demonstrating the effect of temperature on the precipitating mineral assemblages. Results were compared to a thermodynamic simulation of the evaporation experiment at 25°C, based on the Harvie-Møller-Weare activity coefficients correction.
The relative amounts of the precipitated minerals were evaluated from the bulk chemical composition of the collected precipitates, applying a Li-based methodology for subtracting the contribution of the brine adsorbed on the precipitated salts. The following minerals were identified during the evaporation experiments: halite (NaCl), epsomite (MgSO4∙7H2O), kainite (KMgClSO4∙3H2O), carnallite (MgKCl3∙6H2O), kieserite (MgSO4∙H2O) and bischofite (MgCl2∙6H2O). The precipitation of the Mg-salts was accompanied by continuous halite precipitation up to DE of ~170. The experimental results are in good agreement with literature experimental data, available up to DE = 98, and generally follow the thermodynamic calculations, thereby supporting both the established methodology of the experiments and the simulation parameters and assumptions. Minor differences between the experiments and the thermodynamic calculation are mainly due to temperature variations. The experiments suggest that, at warmer temperatures (~50°C), kainite and bischofite precipitate instead of kieserite, which precipitates to a greater extent at lower temperatures (25-30°C). The presence of organic matter (OM) in the brine was found to reduce the evaporation rate and the final DE at which evaporation ceased, but not to significantly affect the chemical evolution of the brine.
The detailed systematic data-set presented here is useful for both geochemical and applied purposes. For example, it can be used as a reference for reconstructing the evolution of ancient marine-derived brines, using evaporitic sequences far beyond the halite facies. Hence, this study provides new insights on the formation of such evaporitic minerals and opens the way for further studies on these highly soluble evaporitic sequences as clues to the chemical composition of the ancient oceans.
... The Ma-2, Ma-4, and Ma-6 members are mainly carbonate (dilution section with more seawater input), consisting of limestones interbedded with minor dolomites (Feng et al. 1998;Cai et al. 2005;Xia et al. 2008;Li et al. 2011;Huang et al. 2015). Ordovician evaporites are very rare in the geological record, having been reported only from China and Canada (Zharkov 1981;Zhang et al. 1991;Feng et al. 1998;Meng et al. 2014). Super thick Ordovician evaporites were found in the Ordos Basin during oil and gas exploration (Hou et al. 2003). ...
At the present day, stromatolites are very rare and limited to high-salinity settings. However, abundant and variable stromatolite fossils occur in thick evaporite sequences, the Middle Ordovician Majiagou Formation of the Ordos Basin, northwestern China. The setting and fossil assemblage imply that the high salinity prevented metazoan grazing and allowed stromatolites to flourish. The carbon isotope curve based on new data (average data range from −4.52 to +0.56‰) from drilling cores in Majiagou Formation is in good agreement with Middle Ordovician (Darriwilian), and supports the Middle Ordovician age inferred from biostratigraphy. Sulfur isotopes values (range from +27.1 to +28.0‰) are higher than those of the Upper Ordovician but much lower than those of the Lower Middle Cambrian; thus, the sulfur values imply that the Majiagou Formation is of Middle Ordovician age. New carbon and sulfur isotope data imply that these strata are of Middle Ordovician age, in good agreement with previous paleontological dating.
... Rising sea beds cause obstruction, limited flow, loss of contact of inner shallow seas to the ocean. Evaporate deposits could have temporarily decreased ocean salinity [48,64,65]. Others thought that salt extraction did not decrease significantly the salinity of sea [66]. ...
The long-term salination of two major osmolyte systems, the ocean and the inner environment of vertebrates has been compared. The average osmolality of today’s sea (1.09 Osm) is more than three times higher than that of the blood of land vertebrates (~0.3 Osm). Of the two major strategies for ionic adaptation, in the first pattern the osmolarity of organisms (unicells, invertebrates, primitive vertebrates) equals that of the surrounding water, but the qualitative composition of body or cells fluid differ from those of the environment. In the second pattern of ionic adaptation advanced invertebrates and vertebrates maintain their energy consuming osmotic content and ionic composition of their extracellular environment. In spite of geological changes, terrestrial vertebrates maintained their physiological ionic concentration that corresponded to the sea at the time of their emergence in the Devonian era, rather than the osmolality of the ocean maintained its constancy. Paradoxically, the recent global melting of ice and snow with its temporary dilution effect is opposed by the long-term salination of the ocean. To resolve the contradiction between the salination process and its short term oscillations supported by Raoult’s law of dilute solutions, glacial periods favoring salination and interglacial periods of dilutions are: a) characterized as salinity fluctuations over geological ages, b) representing a dynamic osmolyte system against a general geochemical balance, c) directed towards a general salination process of oceans interrupted by glacial and interglacial oscillations. The gradually increasing salinity of ocean poses a long-term threat to the biodiversity and global life. It is assumed that unless mitigative measures of global proportion will be implemented, biodiversity of life on Earth will be endangered by the salinity of oceans and the shrinkage of the fresh water resources.
... The most important studies include Gimm (1968), Korenevskiy (1973), Rayevskiy and Fiveg (1973), British Sulfur Corporation Ltd. (1975, 1984, Mayrhofer (1983), Zharkov (1984), Vysotsky et al. (1988), Beer (1996, and Garrett (1996). Zharkov (1981) calculated volumes for sulfates, halides, and potassium-bearing halides and sulfates in Paleozoic basins of the world, but grades and hence tonnages of K 2 O were not included. Many of these studies are in German or Russian, with very little of that information being included in analyses by more recent English-language publications. ...
During the past 15 yr, the global requirement for fertilizers has grown considerably, mainly due to demand by a larger and wealthier world population for more and higher-quality food. The demand and price for potash as a primary fertilizer ingredient have increased in tandem, because of the necessity to increase the quantity and quality of food production on the decreasing amount of available arable land. The primary sources of potash are evaporites, which occur mainly in marine salt basins and a few brine-bearing continental basins. World potash resources are large, but distribution is inequitable and not presently developed in countries where population and food requirements are large and increasing. There is no known substitute for potash in fertilizer, so knowledge of the world's potash resources is critical for a sustainable future. The U.S. Geological Survey recently completed a global assessment of evaporitehosted potash resources, which included a geographic information system-based inventory of known potash resources. This assessment included permissive areas or tracts for undiscovered resources at a scale of 1:1,000,000. Assessments of undiscovered potash resources were conducted for a number of the world's evaporite-hosted potash basins. The data collected provide a major advance in our knowledge of global potash resources that did not exist prior to this study. The two databases include: (1) potash deposits and occurrences, and (2) potash tracts (basins that contain these deposits and occurrences and potentially undiscovered potash deposits). Data available include geology, mineralogy, grade, tonnage, depth, thickness, areal extent, and structure, as well as numerous pertinent references.
... Salt deposits underlie one quarter of the Earth's landmass and are often hundreds of metres thick (Blatt et al., 1980; see paper by Hübscher, this volume) which makes them one of the most significant subterranean microbial habitats. Much of Europe was covered by the hypersaline Zechstein Sea in the Permo-Triassic period (Zharkov, 1981), and the Mediterranean Sea was desiccated more recently, with halite precipitation starting between 5.6 and 5.55 million years ago ; see the Executive Summary, this volume). Some salt deposits have been neither deeply buried beneath other geological deposits nor dissolved after their deposition, whereas others have undergone much alteration. ...
... Este trabalho é precursor no reconhecimento de um sistema lacustre de clima árido, com campo de dunas eólicas e sabkha continental para a porção superior da Formação Pedra de Fogo, sem qualquer indício determinante de contribuição marinha. A confirmação de um paleoambiente tipicamente de clima quente árido corrobora com as evidencias globais de clima e sedimentação durante a parte média a superior do período Permiano (Zharkov, 1981;Scotese et al., 1999;Golonka e Ford, 2000;Zharkov e Chumakov, 2001;Chumakov e Zharkov, 2002Scheffler et al., 2003;Ford e Golonka, 2003;Kiehl e Shields, 2005). ...
Stratigraphic and facies analysis in the Filadélfia region, TO, BR, at the western of the Parnaíba Basin, allowed redefine the paleoenvironment of the upper portion of the Pedra de Fogo Formation of Permian age. The studied deposits are a series of approximately 100 m thick, predominantly siliciclastic, with subordinate carbonates and evaporites, where were defined 21 sedimentary facies that could be grouped into six facies associations (AF): AF1) Lacustrine with ephemeral river deposits; AF2) Storm wave-influenced lake deposits; AF3) Continental sabkha deposits; AF4) Central lake deposits; AF5) Eolian dunes field deposits; and AF6) Lake/oasis deposits with inunditos. These associations indicate that during Permian, an extensive lacustrine arid system developed adjacent to eolian dunes fields and continental sabkha, as well as with contributions from ephemeral rivers. Fluvial incursions into lakes propitiated the formation of suspension lobes and sheet flows (AF1). Sabkha plains (AF3) were formed in the marginal portions of the lake that eventually were influenced by storms waves (AF2), while central zone were site of intense pelitic deposition (AF4). The low supply of eolian sand in this system resulted in the formation of restricted dune fields (AF5), with development of interdune lakes (oasis), where proliferating giant ferns, sporadically flooded by ephemeral rivers (AF6). The facies associations data, corroborated by the paleogeography of the region during the Late Permian, indicate that settling of the top part of the Pedra de Fogo Formation was laid during a hot and arid climate.
... Strain H4 T and several strains related to it, as well as members of the species Halococcus salifodinae, were isolated from subterranean salt mines in Austria. The salt sediments are thought to have been deposited during the Permian period (Zharkov, 1981). Evidence gathered from the data presented in this and earlier studies Stan-Lotter et al., 1993, 1999McGenity et al., 2000 ;Radax et al., 2001) further strengthens the notion that halophilic salt mine strains are the remnants of archaeal populations that originally inhabited the Palaeozoic brines. ...
Several extremely halophilic coccoid archaeal strains were isolated from pieces of dry rock salt that were obtained three days after blasting operations in an Austrian salt mine. The deposition of the salt is thought to have occurred during the Permian period (225-280 million years ago). On the basis of their polar-lipid composition, 16S rRNA gene sequences, cell shape and growth characteristics, the isolates were assigned to the genus Halococcus. The DNA-DNA reassociation values of one isolate, strain H4T, were 35 and 38% with Halococcus salifodinae and Halococcus saccharolyticus, respectively, and 65.8-67.8% with Halococcus morrhuae. The polar lipids of strain H4T were C20-C25 derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate. Whole-cell protein patterns, menaquinone content, enzyme composition, arrangements of cells, usage of carbon and energy sources, and antibiotic susceptibility were sufficiently different between strain H4T and H. morrhuae to warrant designation of strain H4T as a new species within the genus Halococcus. It is proposed that the isolate be named Halococcus dombrowskii, and the type strain is H4T (= DSM 14522T = NCIMB 13803T = ATCC BAA-364T).
... Many researchers have attempted to reconstruct climate zones over geological time by analyzing the distribution of climatically sensitive deposits (Strakhov, 1967;Zharkov, 1981;Bardossy, 1982). Terrestrial red beds would appear to be indicative of climates that are warm and dry or seasonal with respect to rainfall (Parrish, 1998;Du et al., 2011), and the distribution of coal indicates a range of humid climates under different temperature conditions (Meyerhoff and Teichert, 1971;Boucot et al., 2009). ...
As a paradigm of greenhouse climate in Earth's history, the Cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate. The Songliao Basin, among the longest duration (85-90 m.y.) of continental sedimentary basins, provides an excellent opportunity to recover a nearly complete Cretaceous terrestrial sedimentary record. Extensive lake deposits, ten-kilometers deep and covering an area of 260,000 km(2) of the Songliao Basin, provide unique, detailed records that can be tied to the global stratigraphic time scale, thereby improving our understanding of the continental paleoclimate and ecological system. The two coreholes at SKIs and SKIn sites were drilled into this basin and completed with a total length of 2485.89 m of recovered core that spanned the complete middle-to-Upper Cretaceous strata in the basin. The unique geological setting of long-term continuous subsidence within the largest Cretaceous landmass in the world makes the Cretaceous Songliao Basin of northeastern China an ideal place to study Cretaceous climate change on the continent. This paper reviews the literature on the paleogeography and paleoclimate of the northern East Asia and the Songliao Basin during the Cretaceous. Based on the climatologically sensitive deposits, oxygen isotope studies, and paleontology, the climate during the Cretaceous in the Songliao Basin was temperate and humid with relatively abundant rainfall. During the period, significant changes - four cooling, three warming, and three semiarid events - are generally consistent with the oxygen isotope data from East Asia, and the four cooling events, in Berriasian-Valanginian, Aptian-Albian, early Santonian, and Campanian-Maastrichtian, may be related to potential glaciations in Cretaceous.
... 3-5) in cratonic settings; potash deposits and their host tracts in intracratonic basins tend to be more areally extensive than in other types of basins. This supports previous observations by and Zharkov (1981). In contrast, in rift basins and tectonic settings with active faulting and subsidence, salt and potash deposits are thicker, have more elongated shapes, and have a greater tendency to develop salt structures than deposits in other tectonic basin settings. ...
Potash is mined worldwide to provide potassium, an essential nutrient for food crops. Evaporite-hosted potash deposits are the largest source of salts that contain potassium in water-soluble form, including potassium chloride, potassium-magnesium chloride, potassium sulfate, and potassium nitrate. Thick sections of evaporitic salt that form laterally continuous strata in sedimentary evaporite basins are the most common host for stratabound and halokinetic potash-bearing salt deposits. Potash-bearing basins may host tens of millions to more than 100 billion metric tons of potassium oxide (K2O). Examples of these deposits include those in the Elk Point Basin in Canada, the Pripyat Basin in Belarus, the Solikamsk Basin in Russia, and the Zechstein Basin in Germany.
This report describes a global, evaporite-related potash deposits and occurrences database and a potash tracts database. Chapter 1 summarizes potash resource history and use. Chapter 2 describes a global potash deposits and occurrences database, which contains more than 900 site records. Chapter 3 describes a potash tracts database, which contains 84 tracts with geology permissive for the presence of evaporite-hosted potash resources, including areas with active evaporite-related potash production, areas with known mineralization that has not been quantified or exploited, and areas with potential for undiscovered potash resources. Chapter 4 describes geographic information system (GIS) data files that include (1) potash deposits and occurrences data, (2) potash tract data, (3) reference databases for potash deposit and tract data, and (4) representative graphics of geologic features related to potash tracts and deposits. Summary descriptive models for stratabound potash-bearing salt and halokinetic potash-bearing salt are included in appendixes A and B, respectively. A glossary of salt- and potash-related terms is contained in appendix C and a list of database abbreviations is given in appendix D. Appendix E describes GIS data files, and appendix F is a guide to using the geodatabase.
... Plot of the areas underlain by salt in various significant ancient evaporite deposits (saline giants) (afterZharkov 1981) ...
This paper looks first at the distribution of modern evaporite-depositing areas and then at the much more extensive evaporite basins of the past, many of which have no modern analogue in size or depositional diversity. The inability to compare all aspects of evaporites past and present, reflects a failing of modern arid geological settings. Problems inherent in many of the correlation assumptions used in sequence stratigraphic interpretations of evaporite basins will discuss. For interpretations the Zechstein was chosen because there is no modern day equiva-lent to a seawater-fed drawdown basin such as the Zechstein. Distribution of modern evaporites Modern bedded evaporite deposits typically accumulate in saline lake and mudflat environments within groundwater discharge regions in the arid and semi-arid de-serts of the world. Coastal deposits of evaporites occur in areas fed by marine seepage into isolated coastal depressions or mudflats. Continental playa deposits, typically contain much larger areas of salts than coastal deposits, but still do not approach the aerial extent or thicknesses of their ancient counterparts. Evaporite salts also form as lakes precipitates and efflorescences in the cold polar deserts of Antarctica, but the amount of salt in these regions pales to insignificance when compared with settings closer to the equator. Salt-accumulating desert playas form as discharge areas within endoheic (internal drainage) basins; where more water is leaving the basin via evaporation than is en-tering it as rainfall, surface, or subsurface inflow. They are found at different loca-tions such as tectonic basins, wind deflation hollows, and abandoned fluvial val-leys. The greatest present-day volumes of salts are to be found accumulating within continental tectonic basins located in the world's desert belts. Present day settings are not direct analogues for many environments where larger and thicker evaporites accumulated in the past.
... 3-5) in cratonic settings; potash deposits and their host tracts in intracratonic basins tend to be more areally extensive than in other types of basins. This supports previous observations by and Zharkov (1981). In contrast, in rift basins and tectonic settings with active faulting and subsidence, salt and potash deposits are thicker, have more elongated shapes, and have a greater tendency to develop salt structures than deposits in other tectonic basin settings. ...
... 4-Balkwill (1978); 5- Rodgers (1963); 6-- Rodgers (1970);7-De Cserna (1971); 8- Rogers et al. (1962);9-Ujeta (1969): lo- Campbell and Burg1 (1965); II-McLaughlin (1972): 12-Tortochaux (1978): 13-Brinkman and Logters (1968); 14- Liechti (1968); 15-Spicher (1980); 16-Laubscher (1972); 17-Paraschiv and Olteanu (1970); 18-Farhoudi (1978); 19- Yeats and Lawrence (1985) 20-Leith (1984); 21 -Keith et al. (1982); 22-Kazantsev and Kamaletdinov (1977); 23-Stewart (1979);24-McNaughton et al. (1968);25-Nalivkin (1973);26-Le Pichon et al. (1982). anhydrite and gypsum, are common (Zharkov, 1981). In this paper, we examine the ways in which the presence of a relatively weak evaporite-rich detachment influences 'the style of deformation in a thin-skinned mountain belt. ...
Davis, D.M. and Engelder, T., 1985. The role of salt in fold-and-thrust belts. In: N.L. Carter and S. Uycda (Editors), Collision Tectonics: Deformation of Continental Lithosphere. Tectonophysics, 119: 67-88. The style of deformation in thin-skinned fold-and-thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks. Evaporites can provide an extremely weak horizon within which a basal detachment can form and along which only a relatively small shear traction can be supported. Fold-and-thrust belts that form atop a salt layer, such as the Appalachian Plateau, the Franklin Mountains in northwestern Canada, and the Jura of the Alps, among others, share several readily observable characteristics. As predicted by a simple mechanical model for fold-and-thrust belts, a detachment in salt permits a thrust belt to have an extremely narrow cross-sectional taper. In addition, predicted orientations of the principal stress axes over a salt dtcollement are consistent with the commonly observed lack of a consistently dominant vergence direction of structures within the thrust belt. Other common attributes of salt-basal thin-skinned deformation include the presence of several widely but regularly spaced folds and abrupt changes in deformational style at the edge of the salt basin.
Large regions of Earth's surface are underlain by salt deposits that evaporated from ancient oceans and are populated by extreme halophilic microbes. While the microbiology of ancient evaporites has been well studied, the ecology of halite deposits and more recently formed NaCl "salticle" stalactite structures (speleothems) in a Triassic halite mine are less well characterized. The microbiome of Kilroot Salt Mine was profiled using conventional and enhanced culturing techniques. From this, 89 halophilic archaeal isolates from six known genera, and 55 halophilic or halotolerant bacterial isolates from 18 genera were obtained. Culture-independent metagenomic approaches also revealed that culturing techniques were inadvertently biased toward specific taxa, and the need for optimized isolation procedures are required to enhance cultivation diversity. Speleothems formed from saturated brines are unique structures that have the potential to entomb haloarchaea cells for thousands of years within fluid inclusions. The presence of such fluid inclusions, alongside the high abundance of genes related to glycerol metabolism, biofilm formation, and persister cell formation is highly suggestive of an environmental niche that could promote longevity and survivability. Finally, previous studies reporting the discovery of novel biocatalysts from the Kilroot mine microbiome, suggests that this environment may be an untapped source of chemical diversity with high biodiscovery potential.
New Concepts in Global Tectonics Newsletter, no. 65, December, 2012. www.ncgt.org
Abstract: During the reign of plate tectonics, the tectonic evolution of the Middle East has been turned into a never ending ad hoc situation-without trustworthy phenomenological coherence. In an attempt to get out of this deadlock, the geological evolution of the region-stretching from India in the east to Turkey in the west-is interpreted within a new global evolutionary scheme: Global Wrench Tectonics. In working out the new geological development pattern, we start with the pre-plate tectonics notion of the Tethys-an extended E-W running epicontinental seaway along the southern fringes of Eurasia, including the Middle East. During the Alpine tectonic revolution, the Tethyan axis was close to the time-equivalent palaeoequator; and as the palaeo-equatorial zone is a crucial geographical belt for inertia-based wrench deformation of the lithosphere, the Middle East Tethys sector underwent a tectonic cataclysm during which the epicontinental Tethys disappeared completely. Lithospheric Alpine age wrenching led to significant overall transpression of the Tethyan basement giving rise to marginal thrust belts, transcurrent faulting, ophiolite formation, and tectonic rotation of both externally and internally located continental blocks. For example, palaeomagnetic evidence, fault plane solutions, GPS velocity vectors, along with structural data suggest that the Central Iran micro-continental assembly-including the Lut Block-were subjected to a significant counter clockwise rotation in response of Upper Cretaceous-Lower Tertiary transpressive deformation. Furthermore, evidence suggests that the many kilometers thick salt accumulations of the Middle East-including the major Infra-Cambrian Hormoz sequence, the Neogene basins of Iran, the Red Sea and the Dead Sea depressions-are unlikely to be of evaporitic origin; instead, they are much more likely precipitates of episodic ejections of high concentration brines from the upper mantle. The upward surging of asthenospheric material-including magma, solid state upper mantle material (building up surface ophiolites), and transport of the whole diversity of metal compounds-is tightly associated with changes in Earth rotation.
Extremophilic organisms are found in all three domains of life - Bacteria, Archaea, and Eukarya. They tolerate or even require habitats which are characterized by extreme factors, such as low water activity, scarce nutrients and extremes of temperature, pH, pressure and toxic compounds. Most extremophiles are prokaryotes, with Archaea accounting for the largest proportion, but the group also includes Eukarya such as algae, fungi and protozoa, and even multicellular organisms. This chapter provides an overview of the extreme environmental factors which influence life on Earth, a short survey of the various types of extremophiles - including viruses - as well as an update of current records for the limits of growth by extreme environmental factors and survival of extreme conditions. The interest in extremophilic microorganisms is growing, particularly since they survive exposure to space conditions and may possibly be capable to live in extraterrestrial environments.
About 250 million years ago the continents were close together and formed Pangaea, a supercontinent, which persisted for about 100 million years and then fragmented. The landmasses at that time were located predominantly in the southern hemisphere. The climate was arid and dry; the average temperature is thought to have been several degrees higher than at present. This was one of the time periods in the history of the Earth, when huge salt sediments formed. A total of about 1.3 million cubic kilometers of salt were deposited during the late Permian and early Triassic period alone (Zharkov 1981). The thickness of the salt sediments can reach 1000 to 2000 meters. When Pangaea broke up, land masses were drifting in latitudinal and Northern direction. Mountain ranges such as the Alps, the Carpathians and the Himalayas were pushed up due to the forces of plate tectonics. The salt deposits in Austria originated in the Alpine basin, which extended from Innsbruck to Vienna. Some salt mines in the Alps are still in operation, and these were the sources of our samples. In the Alpine basin and in the Central European basin (Zechstein sea), no more salt sedimentation took place after the Triassic period; however, in other locations, e.g. in Poland, significant salt deposits were still formed until about 20 million years ago. Dating of the salt deposits by sulfur-isotope analysis (ratios of 32S/34S as measured by mass spectrometry), in connection with information from stratigraphy, indicated a Permo-Triassic age for the Alpine and Zechstein deposits, which was independently confirmed by the identification of pollen grains from extinct plants in the sediments (Klaus 1974).
Is the present the key to the past in evaporite studies? It’s part of a broader question that has plagued geologists working with salts since the seventeenth century, when Werner’s Neptunist postulates explained world geology (including igneous strata) as layered precipitates from cooling oceanic waters. And, like Werner’s Scottish antagonists, we are still discussing the merits of strict uniformitarianism. In this chapter I am not questioning the fundamental principle of using present-day process studies to interpret the past. Nor am I questioning the utility of detailed studies of process analogs and the use of physical constants to reliably interpret the past. Let me put it plainly for the creationist community and proponents of “intelligent design,” all the geological evidence clearly shows the earth is not 8,000, but more than 4 billion years old. Biological evolution is fact, it interacts with and responds to the physical environment and has been in operation on the earth’s surface for at least the past 3.45 billion years. There is no need to invoke the supernatural and sky faeries to explain biological evolution and other earth processes, and there is no geological evidence for a worldwide biblical flood of epic proportions drowning mankind and covering all the land.
Halophilic archaebacteria (haloarchaea) thrive in environments with salt concentrations approaching saturation, such as natural brines, the Dead Sea, alkaline salt lakes and marine solar salterns; they have also been isolated from rock salt of great geological age (195–250 million years). An overview of their taxonomy, including novel isolates from rock salt, is presented here; in addition, some of their unique characteristics and physiological adaptations to environments of low water activity are reviewed. The issue of extreme long-term microbial survival is considered and its implications for the search for extraterrestrial life. The development of detection methods for subterranean haloarchaea, which might also be applicable to samples from future missions to space, is presented.
The Earth currently contains a large number of underground salt formations of significant size. These formations range in age from Jurassic (60,000,000 Million year of age [Ma]) to Cambrian (570,000,000 Ma). Most are Permian in age (230 — 280 Ma) (Javor 1989). Salt formations are distributed across nearly every continent, with the largest number in the northern hemisphere (Zharkov 1981)
Live microbes have been isolated from rock salt up to Permian age. Only obligatory cellular functions can be performed in halite-buried cells. Consequently, their genomic sequences are likely to remain virtually unchanged. However, the available sequence information from these organisms is scarce, and consists of mainly ribosomal 16S sequences. Here, live archaea were isolated from Early Cretaceous (∼123 million years old) halite from the depth of 2000 m in Qianjiang Depression, Hubei Province, China. The sample was radiologically dated and subjected to rigorous surface sterilization before microbe isolation. The isolates represented a single novel species of Halobacterium, for which we suggest the name Halobacterium hubeiense, type strain Hbt. hubeiense JI20-1. The species was closely related to a Permian (225-280 million years old) isolate, Halobacterium noricense, originating from Alpine rock salt. This study is the first one to publish the complete genome of an organism originating from surface sterilized ancient halite. In the future, genomic data from halite-buried microbes can become a key factor in understanding the mechanisms by which these organisms are able to survive in harsh conditions deep underground or possibly on other celestial bodies.
For several hundred years the existence of enriched phosphatic sediment (phosphorite) has been recognized. In turn, for slightly more than 150 years, a contentious argument has existed about its origin. For a historical summary and background of studies on the origins and temporal and spatial distribution of phosphorite deposits see, especially, Bentor (1980), Cook (1984), Cook et al. (1990), and references therein. In part, much of the controversy surrounding the origin of phosphorite deposits exists because of various explanations for the existence of a single, giant phosphorite deposit in the Permian Phosphoria Formation of the western USA. Moreover, for about the past decade, the extremely uneven distribution of phosphorites in the sedimentary record, with one of the largest accumulations in the Permian, has been noted. The Permian commonly is stated to be among the few notable periods of phosphorite accumulation in the Phanerozoic; hence, it must represent a major change in the global phosphate cycle.
All life we know no matter how freaky in other respects, is still based on organic molecules dissolved in water, and we all use the same basic cellular machinery. Extremophiles haven’t fundamentally changed the way we think about strategies to look for life, but they have bolstered the optimism with which we search. Right now anywhere with liquid water is considered a possible habitat, and this guides our quest. (Grinspoon 2003)
The terms brines and evaporites are used in a generic way to describe concentrated solutions of ions and the chemical precipitates from those solutions. Based on the order of precipitation of evaporite minerals from brines of known composition, geochemists have deduced the chemistry of brines from which ancient evaporites have been deposited. Modern evaporite basins and their brines also serve as models to reconstruct the physical and temporal development of ancient evaporite deposits. The following discussion highlights some of the major geological aspects of hypersaline environments as well as chemical and physical aspects of brines. The discussion of brine chemistry emphasizes the factors that are important in biological productivity. The modern evaporite areas discussed in this book are shown in Figure 1.1.
: China was formed by amalgamation of several small continental blocks (cratons), micro, blocks and orogenic belts in different paleoclimatic settings. It may be correlated with other continental blocks but has its own specific characteristics; therefore the tectonic environments of China's marine and continental saline basins and salt, and potash, forming environment have some specific characteristics: multiple phases of salt formation, difference in salt, forming ages, migration and concentration of salt, forming processes and diversity of component materials, as well as small sizes of marine saline basins and great changes of saline basins in the late stage and occurrence of abundant liquid mineral resources. The nature of the tectonic basement exerted a key controlling effect on the formation of potash basins. The stable tectonic region was favorable for potash concentration in a quasi, stable region, and quasi, and the quasi-stable region was favorable for salt concentration and potash formation in a local stable tectonic region. Most China's major ancient saline basins occur in “quasi, cratons (continental block)”; especially all the marine saline basins occur in continental blocks with the Precambrian basement. These regions are the key ones for potash search. Most relatively large, scale soluble salt deposits are developed in relatively stable continental nuclei. According to the characteristics of the tectonic domains where China's salt, forming basins are located, the North China, Yangtze and Tarim, Qaidam salt minerogenetic domains and the northern Qiangtang, western Yunnan salt minerogenetic belt may be distinguished. Their salt and potash prospects will be discussed separately.
Previous research has indicated that halophilic microorganisms are associated with salt crystals from ancient formations. However,this research has generally failed to convincingly demonstrate that these organisms were originally trapped inside the crystals during their deposition and were not recent surface contaminants. This paper presents techniques for crystal selection; verifiable, noninvasive, surface sterilization of salt crystals; and sterile extraction of biological material from the crystals. Immersing salt crystals in 10 M NaOH for 5 min; rinsing with sterile, saturated brine before immersing for 5 min in 10 M HCl; and rinsing with saturated brine is an effective method for surface sterilization. No growth has resulted from contamination tests of 216 faces from 36 natural salt crystals exposed to these treatments. Pure culture experiments using the halotolerant eubacteria, Halomonas elongata and Bacillus sp. (2-9-3), and the archeon, Halogeometricium borinquense, showed that exposure to either 10 M HCl or NaOH reduced the population of these organisms by a factor of 107 to 108 colony-forming units/ml. The fluid is extracted from inclusions by drilling into surface-sterilized salt crystals with a variable-speed drill using sterilized 0.5-mm-diameter carbide drill bits and extracting the fluid with a sterilized microliter syringe. Drilling and extraction are performed in a Class II biosafety cabinet. All procedures are carried out in a biosafety level 3 facility. All personnel involved wear cleanroom coveralls, shoe covers, hair caps, and gloves. The above protocol has resulted in the isolation of a Bacillus sp. from a Permian-age salt crystal.
Marine evaporites such as the Zechstein (Permian, NW Europe) consist of thinning-upward sulphate–
halite–potash cycles whose origin is poorly understood. An intra-basinal mechanism presented here explains well their mineral composition and cycle development. It involves the progressive obstruction of ocean connections by sulphate-platform progradation, causing a chain reaction of outflow reduction and subsequent accelerated sulphate precipitation. Numerical modelling shows this to be a self-accelerating process that ultimately triggers halite and potash precipitation. Isostatic compensation of the salt load explains the formation of accommodation space for subsequent cycles, each about half the thickness of the previous cycle.
http://dx.doi.org/10.1144/jgs2013-062
Wide distribution of Cambrian salt-bearing basins is a prominent feature of older strata in Asia. The Cambrian salt-bearing sequences are mainly distributed in East Siberia of Russia, Iran, Oman, India, Pakistan, and China. The Cambrian was one of the most important epochs of potash deposition in the world. Potash salts are found in East Siberia, Iran, India, and Pakistan, and, among them, one of the largest potash deposits in the world—the Siberian Nepa Potash Basin-formed in the Early Cambrian. The Cambrian was also one of the most important epochs of rock gypsum and salt deposition in China. Gypsum deposits occur in all the three major continental blocks of China (Yangtze Block, North China Block, and Tarim Block), forming four large marine salt-bearing basins. Extensive, thick rock salt deposits have been found in the Yangtze Block and Tarim Block, where better potash-bearing hydrochemical manifestations and leaching coefficient anomalies have been found for the first time. In the North China Block, a number of gypsum deposits and occurrences have been observed and Cambrian high-salinity brine and halite crystals found in oil wells. This study for the first time relatively completely analyzes the distribution and tempo-spatial evolution of Cambrian gypsum and salt-bearing basins in China, which provide an important basis for the study of the history of Cambrian paleogeographic evolution over the globe and salt and potash exploration in Cambrian salt-bearing basins of China.
In view of the difficulties of stratigraphic correlation, the absence of being able to position continents reliably, the scarcity of climate indicators, and the fact that Vendian sequence crops out over a wide area and can be far apart, it has only so far been possible to identify the most general climatic features for three Vendian units. Late Vendian (Nemakit-Daldyn), and possibly Early Tommotian (Early Cambrian), time was characterized by a glacial climate with pronounced climatic zonation. It appears that there were northern and southern cold zones and a low-latitude, possibly mid-latitude warmer zones. Throughout the time the Middle Vendian sequence was being deposited (Redkino-Kotlin), a warm, possibly and zone was characteristic of low and mid-palaeolatitudes. In southern high latitudes, there is evidence of a warm humid climate at some periods during this time. The Early Vendian (Laplandian or Varangian) time was characterized by a glacial climate. Some palaeocontinental reconstructions based on magnetism suggest that these glaciations affected high, middle and most of the low latitudes, extending to the palaeoequator. The timing of glacial events in the late Neoproterozoic and their extent across the globe and severity is a topic of great debate at the moment - some researchers suggesting glaciations that lasted for millions of years that locked the entire Earth in solid ice ('Snowball Earth'). Others suggest that some ice-free oceans were present even during the most severe of glacial events and certainly some geological evidence seem to fit this latter hypothesis well.
In the Late Proterozoic the world's oceans changed from being relatively oxic and well-mixed, into a less mixed and more stagnant system. This resulted in the accumulation of massive amounts of organic matter and pyrite in anoxic sediments on the sea floor, and the enrichment of P in the anoxic deep ocean waters. Significant rises in atmospheric O 2 levels must have accompanied the periods of greatly enhanced organic matter burial. A return to a stable more oxic ocean system occurred around the Proterozoic/Cambrian boundary, at which time rifting of the supercontinent(s) created a large number of epicontinental seas at low latitudes, enabling deep P-rich ocean waters to be moved into shallow-water environments. While increasing pO 2 levels during the latest Proterozoic may have been largely responsible for the Cambrian "radiation' event, the increase in pCO 2 levels at the beginning of the Cambrian, as the oceans became more oxic, may have been responsible for the acquisition of mineralized skeletal structures by soft-bodied organisms. -from Authors
Improved regional and interregional stratigraphic correlations of Pennsylvanian strata permit comparisons of vegetational changes in Euramerican coal swamps. The coal-swamp vegetation is known directly from in situ coal-ball peat deposits from more than 65 coals in the United States and Europe. Interpretations of coal-swamp floras on the basis of coal-ball peat studies are extended to broader regional and stratigraphic patterns by use of coal palynology. Objectives of the quantitative analyses of the vegetation in relation to coal are to determine the botanical constituents at the peat stage and their environmental implications for plant growth and peat accumulation. Morphological and paleoecological analyses provide a basis for deducing freshwater regimes of coal swamps.
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