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Terrestrial analogue sites have been crucial for studying Martian geology and mineralogy, integrating the direct evidence available from Mars through remote sensing and in situ measurements carried out by the instruments on board robotic missions. Studying readily available and accessible terrestrial analogues of Martian fossil or extant environments is considered the most efficient way to answer crucial scientific questions. These analogues offer opportunities to collect a range of geological and microbiological data. The Makgadikgadi Basin (MKB) in Botswana is one of such environments hosting a system of salt pans presenting striking similarities with Mars playa deposits. The MKB presents layered mounds, relict fan deltas with inverted channels, polygonal structures and evaporitic crusts harboring communities of extremophiles. The present-day MKB is predominantly fed by groundwater and local precipitations in an overall arid to semi-arid climate, characterized by high UV radiation and salinity, deposition of evaporitic minerals and authigenic clays. The shallow subsurface of the MKB pans is covered by diagenetic features (duricrusts) including silcretes and calcretes. These pans can serve as test beds for the physical and chemical characteristics of playa deposits on Mars and help improve our understanding of the conditions that might support life outside our planet. • The Makgadikgadi pans physical and chemical conditions resemble early Mars. • Morphologies in the pans formed by the interplay of water upwelling and evaporation. • Polygonal fractures, inverted channels and paleo-shorelines were identified. • Evaporitic crust and duricrusts harbor communities of extremophiles. • The pans are natural laboratory for the study of Mars habitability. [ABSTRACT FROM AUTHOR]

Groundwater salinization and interaction between Playa Lake and regional groundwater were investigated using multi-chemo-isotopic evidences. Forty groundwater and 26 Kashan Playa Lake (KPL) water samples were collected and analyzed for their geochemical compositions. The evolution of hydrochemical facies in Kashan Plain Aquifer (KPA) to KPL is Ca-HCO3 (19%), Mix Ca–Cl (9%), Ca–Cl (17%), and Mix Na-Cl and Na-Cl (55%). Also, the Hydrochemical Facies Evolution Diagram (HFE-D) proposed cation exchange as the main process of salinization in KPA. Based on the binary hydrogeochemical diagrams of (Na+/Cl−)/Cl−, (Ca2+ + Mg2+)/HCO3− + SO42−, and Cl/Br, dissolution of halite and gypsum in the Miocene marlstone in the KPA is the main source of salinity. The δ18O of water in aquifer and playa water samples varies from –10.03 to 7.03‰ (VSMOW) with an average of –6.95‰ and –60.73 to 25.08‰ with average of –45.82‰ for δ2H. Based on the results, the relation between δ18O and δ2H, and δ18O and Br, approves discharge of saline water from KPA to KPL. Likewise, the isotopic composition of δ34SO4, varies from 5.95 to 22.55‰ CDT in KPA, and 5.95 to 9.99 ‰ CDT in KPL. Also, the relations between δ18O-δ34SSO4 and Cl-δ34S were non-linear, indicating that sulfur concentration in KPA and KPL changed due to sulfide oxidation and sulfate reduction in the freshwater and deep brines in the aquifer and mixed during the over-pumping in the KPA. Oxidation of sulfide minerals in the mineralized region in the western part of the aquifer (recharge zone) may have been the source of sulfur leached by seasonal runoff. Water–rock interaction, ion exchange, and hydraulic gradient have been the dominating factors in changing the water chemistry between aquifer and playa leading to saline groundwater discharged to the playa. [ABSTRACT FROM AUTHOR]

The Makgadikgadi Basin in Botswana hosts a system of salt lakes, which developed from the Upper Pleistocene onward due to the gradual shrinking of the giant Lake Palaeo-Makgadikgadi. Stratigraphic and palaeoclimatic studies of this area are difficult due to the influence of several factors, such as a complex history of regional tectonic activities, as well as climatic changes coupled with dryland diagenetic processes. This lake, in the central Kalahari, is the key to understanding the climatic variability in the southern part of Africa in the Quaternary and has played an important role in the evolution of numerous taxa, including our own. In this study, detailed sedimentological analyses (grain size and major elements distribution) of shallow sediments from the Makgadikgadi Pans were combined with the first comprehensive study of the encountered ostracod fauna to establish trends in the environmental changes in the area from the late Quaternary. Ostracod fossil assemblages from the cores of the Makgadikgadi Pans are dominated by the Limnocythere ssp., an opportunistic taxa commonly colonizing the littoral areas of shallow evaporative, ephemeral lakes, together with the subordinate occurrences of Sarcypridopsis ochracea, Sclerocypris cf. bicornis, Candonopsis spp., and Ilyocypris spp. The sediments from the pans show fluctuations in the Cl/K and Ca/Cl ratios, often in phase with the relative abundance of Limnocythere suggesting a cyclicity induced by changes of salinity and alkalinity in the water. This multi-proxy study of the cores collected from the pans suggests a Late Pleistocene shallow, playa lake environment with strongly alkaline water, interrupted by a prolonged drought with sustained aeolian conditions between ∼16 and 2 ka BP. Increasing diversity of ostracod fauna in the top 20–30 cm of the cores indicates that a temporary shift toward higher humidity occurred around 2–1.5 ka BP and lasted through the Medieval Warm Period. This humid period was followed by an overall desiccation trend that started with the Little Ice Age and continues until the present day.

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This study aimed to find the depositional environment and formation conditions of the gypsumdominated Miocene succession alternated and intercalated with clastics and carbonates in the southwestern part of the Erzincan Basin. As a result of sedimentological, mineralogicalpetrographic investigations, it was determined that the gypsum in this sequence was formed as primary and secondary. Primary lithofacies; nodular anhydrite, selenitic, discoidal, gypsum arenitic secondary lithofacies; It is divided into massive, laminated, banded, nodular, brecciated, satin-spar. The facies repetitions and folds, fractures, cracks and faulting in the sequence showed the effect of tectonism with the water level fluctuations in the basin. In addition, these investigations revealed sedimentary structures such as cross-bedding, ripple undulations, chicken-wire, enterolithic and bacterial-algal structures, parallel laminations in gypsum lithofacies. In addition to these, it was understood that gypsum lithofacies were exposed to diagenetic processes under the influence of a hot-humid and semi-arid climate, organic matter activity, meteoric/underground-water and hydrothermal solution factors, and were subjected to high temperature, pressure, salinity and pH conditions. [ABSTRACT FROM AUTHOR]

Extensive palaeodeserts are known from the intracontinental basins of South American Platform, simultaneously to volcanic activity and thick salt beds developed during the rifting phase of Brazilian coastal basins. Based on palaeoenvironmental conditions and modern analogues, it would be expected that Cretaceous evaporites were frequently described in the intracontinental basins of West Gondwana, however, such deposits are rarely mentioned. This work evaluated the recognition and role of evaporitic-related features as palaeoclimatic/palaeoenvironmental proxies, through outcrop-based facies, X-ray diffraction and petrographic analyses of the Areado Group (Lower Cretaceous), Sanfranciscana Basin, southeastern Brazil. The Areado Group stands out as a remarkable record of evaporitic-siliciclastic interactions, consisting of alluvial, lacustrine and aeolian deposits. The stacking pattern reflects the progressive drying-up of the Sanfranciscana Basin during Cretaceous times. Regardless salt dissolution, the Areado Group comprises pseudomorphs after evaporites, evaporitic moulds, sand patch-fabric, and replication of the microtopography of efflorescent crusts. Preservation of evaporitic features in the Areado Group was controlled by the unique geological context of the Sanfranciscana Basin, which was submitted to syndepositional/eodiagenetic cementation and pseudomorphism, along with rapid burial caused by the progradation of aeolian dunes. Equivalent sedimentary structures and morphological aspects also occur in other Cretaceous palaeodeserts of intracontinental basins throughout Brazil. Timing of salt dissolution and isovolumetric/non-isolumetric replacement are important controlling factors on the geological record of evaporitic-siliciclastic systems that undergo post-depositional modifications. The database provided here indicates that playa lake deposits are commonest than traditionally represented in the non-marine Cretaceous record of the West Gondwana and other similar settings worldwide. • Cretaceous non-marine palaeodeserts in the West Gondwana rarely comprise evaporites. • Sedimentological reconstruction and petrographic data allow tracking dissolved salts. • Evidences of dissolved evaporites are common in the Sanfranciscana Basin (Brazil). • Timing, type and extent of dissolution/replacement controls the stratigraphic record. • Evaporites were commonest than thought in the Cretaceous inland of West Gondwana. [ABSTRACT FROM AUTHOR]

This study investigates the depositional setting and diagenetic processes of gypsiferous sediments known as the Koluz gypsum member located in the northeast of Van (Eastern Anatolia-Turkey). The commencement of still-active contractional regime due to the collision of Eurasian and Arabian plates gave way to uplift events on the active Eurasian margin. This uplift initially resulted in termination of marine sedimentation and commencement of continental deposition in the region. The Middle-Late Miocene Kurtdeliği formation is one of the oldest products of the continental setting in the Eastern Anatolia. Sedimentologic and petrographic analyses conducted on the Koluz gypsum member of the formation, the main concern of this study, indicate that the member is represented by secondary gypsum (massive, laminated, nodular, satin spar) and primary gypsum lithofacies (selenite, gypsum arenite, discoidal and radial). The secondary gypsum facies are formed after hydration of anhydrite and anhydritizated primary gypsums. Additionally, mineralogical and geochemical studies suggest that carbonate (dolomite and calcite) and detrital materials found within the member formed during the deposition or late diagenetic processes. The high major and trace element values determined by XRF analyses also indicate intense detrital influx and accordingly terrestrial origin for the basin. Sedimentary textures and lithofacies of the member show a typical ephemeral playa complex, which was likely fed by both evaporation and groundwater discharge. Tectonism, climate, salinity variation, biologic activity and diagenetic and hydrothermal fluids play major roles in the formation and transformation of these sediments to each other. [ABSTRACT FROM AUTHOR]

Abstract It is often difficult to distinguish nearshore marine from non-marine non-fossiliferous quartz-rich sandstones, and in many cases the depositional environment is disputed. Detailed facies analysis is necessary to determine the environment and, although there are no 'smoking gun' features to delineate them, a group of specific attributes in combination can be used to differentiate fluvial from marine deposits. Primary characteristics of fluvial deposits are: fining-upward channel-based sequences lacking marine indicators, well-developed palaeosols, and unimodal palaeocurrent distributions. The Vieux Emosson Formation, a Triassic autochthonous unit of the western Swiss Alps, is one such controversial example. It lies unconformably above crystalline basement and consists of a basal sandstone and conglomerate-dominated unit, and an upper heterolithic sequence of thin sandstones and mudstones with thin dolostone beds near the top. The formation is overlain by allochthonous younger carbonates of the Tethys Ocean. The light color of the basal unit gives the appearance of quartz-rich sandstone. In part because of this and also the overlying marine carbonates, previous workers interpreted the Vieux Emosson Formation as having been deposited in a marginal marine environment, along the southern edge of the continent and bordering Tethys. However, petrographic analysis determined that the Vieux Emosson sandstones are poorly sorted subarkoses and arkoses, and facies analysis indicated deposition in a continental fluvial-lacustrine system with a north-trending palaeoslope off the Vindelician High, towards the Germanic Basin. Deposition of the lower unit was in braided streams, supported by: high-relief basal erosional surface, immature sediment, large angular clasts, amalgamated fining-upward sequences, mottled palaeosol horizons with carbonate nodules, absence of bioturbation, and a unimodal palaeocurrent pattern. The interbedded sandstone and mudstone (proximal) and the upper mudstone and dolostone (distal) units represent deposition in a terminal splay-playa environment. Desiccation cracks, dolostone, absence of body fossils and very rare trace fossils indicate deposition in a playa lake. Non-marine deposition in the region during the latest Early Triassic and early Middle Triassic helps constrain the location and timing of the initial marine transgression in the southern Germanic Basin. Highlights • The Vieux Emosson Formation is examined in detail. • How to differentiate marine from non-marine quartzose sandstones is clarified. • The formation was deposited in fluvial, terminal splay, and playa environments. • Regional northwest paleoslope indicates drainage into the Germanic Basin. • Findings help constrain the marine transgression in the southern Germanic Basin. [ABSTRACT FROM AUTHOR]

A transition from widespread humid to more drought tolerant floras characterized tropical terrestrial ecosystems during the Permian (Cisuralian). Tregiovo (Southern Alps, N-Italy) is one of the very few well dated Kungurian (late Cisuralian) plant localities in Euramerica. It was located in eastern palaeoequatorial Pangea. Two units bearing fossil plant assemblages occur in finely laminated sediments deposited in a playa-lake environment. In this paper, the sedimentology of the Tregiovo Basin is reviewed, and new palaeobotanical, palynological and stable isotopic data are presented, in order to reconstruct the palaeoclimatic and palaeoenvironmental conditions of the Kungurian in the Southern Alps. Both fossil plant assemblages are dominated by conifers ( Hermitia , Feysia , Quadrocladus , Dolomitia ), together with sphenophytes ( Annularia ), ginkgophytes ( Sphenobaiera ), pteridosperms ( Peltaspermum ), taeniopterids and sphenopterids. These taxa, which occur with different abundances in the two plant assemblages, both indicate semi-arid conditions. Associated palynoflora, dominated by bisaccate pollen, and extremely rare spore occurrences, is consistent with the xerophytic character of the macroflora, and suggests that the fossil plant record was not affected by collection or preservation bias. Stable isotopic analyses of two stratigraphic sections reveal an upward trend of increasingly negative δ 13 C org (VPDB), which may correlate with roughly coeval records from marine and continental successions such as in North China and South Africa. This isotopic shift may be attributed to a global perturbation of atmospheric δ 13 C, although the influence of local environmental factors cannot be excluded. [ABSTRACT FROM AUTHOR]

Lop Nur, a playa lake located on the eastern margin of Tarim Basin in northwestern China, is famous for the “Ear” feature of its salt crust, which appears in remote-sensing images. In this study, partial least squares (PLS) regression was used to estimated Lop Nur playa salt-crust properties, including total salt, Ca2+, Mg2+, Na+, Si2+, and Fe2+ using laboratory hyperspectral data. PLS results for laboratory-measured spectra were compared with those for resampled laboratory spectra with the same spectral resolution as Hyperion using the coefficient of determination (R2) and the ratio of standard deviation of sample chemical concentration to root mean squared error (RPD). Based on R2 and RPD, the results suggest that PLS can predict Ca2+ using Hyperion reflectance spectra. The Ca2+ distribution was compared to the “Ear area” shown in a Landsat Thematic Mapper (TM) 5 image. The mean value of reflectance from visible bands for a 14 km transversal profile to the “Ear area” rings was extracted with the TM 5 image. The reflectance was used to build a correlation with Ca2+ content estimated with PLS using Hyperion. Results show that the correlation between Ca2+ content and reflectance is in accordance with the evolution of the salt lake. Ca2+ content variation was consistent with salt deposition. Some areas show a negative correlation between Ca2+ content and reflectance, indicating that there could have been a small-scale temporary runoff event under an arid environmental background. Further work is needed to determine whether these areas of small-scale runoff are due to natural (climate events) or human factors (upstream channel changes).

Bloedite (NaMg(SO)·4HO), which is a sodium-magnesium sulfate mineral, has been determined for the first time in Turkey, in the İshaklı Lake within the Çankırı-Çorum Basin. The İshaklı Lake is a seasonal playa lake which is an east-west extending lake with an area of 0.22 km. Geochemical analyses (XRD, XRF, SEM) of the mineral crust samples indicate that they are composed chiefly of bloedite and thenardite (NaSO) minerals and lesser amounts of halite (NaCl) and gypsum (CaSO·2HO). In the blodite-thenardite association, thenardite mineral grows on bloedite crystals and it is crystallized after bloedite. The well and the spring (and fountain) waters in the vicinity of the lake are saturated with respect to calcite, dolomite, aragonite and talc minerals. In the waters of the İshaklı Lake, however, the degree of saturation of these minerals gradually increases and they become saturated with respect to anhydrite and gypsum as well. Lake waters represent a hydrochemical facies of Na-Mg-SO-Cl (type I). Tritium data (H) indicate that lake waters have higher tritium content (7.55 TU) than the springs and fountains (5.45-6.15 TU), and although there is a thick rock-salt drilled at the bottom of lake (to a depth of 220 m), no recent halite precipitation is observed in the lake bottom. This is attributed to recent recharge and the absence of deep groundwater circulation. The δO-δH data show that spring and fountain waters are in shallow circulation and have undergone a slight evaporation while waters of İshaklı Lake experienced an intense evaporation. According to Mineral Formation Model proposed herein, a portion of the rainfall reaches directly the lake. Additionally, there is recharge from springs, which travel through the Bozkır Formation and reach the lake. During hot periods, evaporation process begins with carbonate and gypsum precipitation as a white-colored crust on the mud flat along the shore of the lake. Therefore, calcium deficit occurs in the lake water. Further evaporation and possible cation exchange process in clay and muds at the lake bottom might be responsible for the formation of Na-sulfate (bloedite + thenardite) mineralization. [ABSTRACT FROM AUTHOR]

This paper describes and interprets the mineral and facies assemblages that occur in carbonate-evaporite shallow lacustrine deposits, considering the importance of the processes pathway (i.e. dolomitization, gypsum calcitization and silicification). The Palaeogene deposits of the Deza Formation (Almazán Basin, central-northern Spain) are selected as a case study to determine the variety of physicochemical processes taking place in carbonate-evaporite shallow lakes and their resulting diagenetic features. Dolostones are the predominant lithology and are composed mainly of dolomite with variable amounts of secondary calcite (5 to 50%), which mainly mimic lenticular gypsum (pseudomorphs). Five morphological types of dolomite crystal were identified as follows: dolomite tubes, dolomite cylinders, rhombohedral dolomite, spheroidal and quasi-rhombohedral dolomite, and cocoon-shaped dolomite. The dolomite cylinders and tubes are interpreted as the dolomitized cells of a widespread microbial community. The sequence of diagenetic processes started with growth of microlenticular interstitial gypsum in a calcareous mud deposited on the playa margin mudflats, and that sometimes included microbial sediments. Immediately following growth of gypsum, dolomite replaced the original calcite (or possibly aragonite) muds, the microbial community and the gypsum. Partial or total replacement of gypsum by dolomite was related mainly to the biomineralization of endolithic microbial communities on gypsum crystals. Later calcitization took place under vadose, subaerial exposure conditions. The development of calcrete in distal alluvial settings favoured the release of silica and subsequent silicification on the playa margin mudflats. Stable isotope compositions of calcite range from −9·02 to −5·83‰ δ13 CPDB and −7·10 to 1·22‰ δ18 OPDB; for the dolomite, these values vary from −8·93 to −3·96‰ δ13 CPDB and −5·53 to 2·4‰ δ18 OPDB. Quartz from the cherts has δ18 OSMOW values ranging from 27·1 to 31·1‰. Wide variation and relatively high δ18 OSMOW values for dolomite indicate evaporitic and closed hydrological conditions; increased influx of meteoric waters reigned during the formation of secondary calcite spar. [ABSTRACT FROM AUTHOR]

The shoreline carbonate lagoon deposits of the Yacoraite Formation in the Maimará locality, Quebrada de Humahuaca (Jujuy, northwestern Argentina) reveal invertebrate and vertebrate trace fossils that are distributed in two distinct subenvironments: (A) the subtidal-lower intertidal zone (S-LI), a moderate/high energy shoreline under wave and tide action, and (B) the playa-lake zone (PL), a protected supratidal/eulittoral zone that characterizes low energy ephemeral bodies of water. In the S-LI zone there are three suites: I, composed of Skolithos linearis and dinosaur tracks ( Hadrosauropodus isp., titanosaurian, ornithischian and theropod tracks); II, composed of monoichnospecific tiers with cf. Taenidium isp.; and III, constituted by abundant didactyl tracks maybe belonging to swimming tracemakers. The trace fossils of the PL zone are included in two suites: I, composed of Lockeia siliquaria and ? Ptychoplasma isp., and II, composed of Palaeophycus tubularis and Planolites cf. montanus with avian tracks (cf. Alaripeda isp.; Avipeda isp., cf. Gruipeda isp., cf. Yacoraitichnus avis ) and indeterminate biped dinosaur tracks. The invertebrate trace fossils in both zones (S-LI and PL) display low ichnodiversity and are restricted to the shallow tier with substrate penetration of a few centimeters, which is characteristic of an unfavorable environment for the establishment of a permanent benthic community. Dinosaur tracks were preserved in an “optimal preservation area”, located in between both zones. The trace fossils of the S-LI zone are ascribed in general sense to the Scoyenia and Skolithos Ichnofacies. Following the current knowledge, the trace fossils of the PL zone are assigned to the shorebird ichnosubfacies, within the Scoyenia Ichnofacies. [ABSTRACT FROM AUTHOR]

Ekonomik yönden önemli bir sodyum sülfat minerali olan blödit (Na2Mg(SO4)2.4H2O) Çankırı-Çorum Havzasında Çorum Bayat ilçesi Ishaklı Köyü kuzeyindeki mevsimlik bir göl olan Ishaklı Gölünde evaporasyon sonucu güncel olarak çökelmektedir. Türkiye'de ilk defa bu çalışma ile belirlenen güncel blödit çökeliminin olduğu küçük bir mevsimlik göl (playa göl) olan Ishaklı Gölü doğu-batı uzanımlı olup yaklaşık 220 000 m2 'lik bir yayılıma sahiptir. Göl kış ve ilkbahar aylarında derinliği 2 m' yi aşan sulu bir göl olmaktadır. Buharlaşmanın olduğu sıcak dönemlerde ise göl suyu kurumakta ve beyaz bir mineral kabuk ile kaplanmaktadır. Ishaklı playa gölünde belirgin zonlanmalardan alınan temsili örneklerde; mineralojik tayinler, kimyasal analizler ve SEM incelemeleri yapılmıştır. Analiz sonuçlarına göre göl alanında egemen mineralin blödit olduğu, buna karşın tenardit (Na2SO4), çok az halit (NaCI) ve jips (CaSO4.2H2O) çökelime eşlik ettiği saptanmıştır. Ishaklı Gölünde yaklaşık 187 500 m2 'lik evaporasyon alanı içerisinde ortalama 3 cm kalınlığa ulaşan sodyum sülfat kabuklaşması (blödit+tenardit) yaklaşık 12 500 ton görünür rezervi ile ekonomik bir potansiyel taşımaktadır

Se presentan los resultados del estudio fitosociológico de la vegetación de los barreales de la provincia del Neuquén dominada por el terófito suculento Halophytum ameghinoi. Se describe una nueva asociación vegetal que se desarrolla y localiza en cuencas endorreicas de escasa pendiente, compuestas por sedimentos finos con presencia de agua en forma temporaria. Como resultado del análisis de los datos de campo junto con los bibliográficos, se discute la pertenencia sintaxonómica de la nueva asociación vegetal propuesta, como así también su caracterización ecológica, composición florística y corológica.The results of a phytosociological study of the Barriales vegetation from northern central Neuquén province, where the Halophytum ameghinoi succulent therophyto dominates, are presented in this paper. A new plant association, which grows in gentle-slope endoreic basins characterized by fine sediments and the presence of temporary waters, is described. After analyzing the field and bibliographical data, we argue the syntaxonomic pertinence of the new plant association, its ecological characterization, floristic composition and chorology.

Playa margins are often characterised by a wide spectrum of landforms, which provide links between major lake stands, as recorded by beach ridges, and the detailed stratigraphic and paleoenvironmental information stored in lacustrine sediments. We mapped playa marginal geomorphology at Lake Frome, South Australia, documented the sedimentary characteristics, and analysed microfossil assemblages in selected sediments. Using a luminescence based approach, the sediments were summarised in four main stratigraphic units. During the later stages of Marine Isotope Stage (MIS)5 fluvio-deltaic sediments were deposited (Unit 1), indicating significant runoff from the adjacent Flinders Ranges into partly freshwater-dominated lakes. No sediments were dated between ∼70 and 25 ka, but renewed sediment delivery from the Flinders Ranges and re-deposition characterised the playa margin LGM and the early Holocene (Unit 2). The most recent phase of depositional activity is reflected by source-bordering dunes and lake marginal spit formation (Unit 3). Short-lived flooding events in the late Holocene are recorded by lake floor sediments and terminal splays (Unit 4). Our findings outline a dynamic late Quaternary playa margin, and highlight the complementary role which playa marginal landforms and sediments may play for the interpretation of runoff, sedimentary dynamics and paleoenvironments related to high regional lake levels. [ABSTRACT FROM AUTHOR]

Williams Point is an iconic late Quaternary sedimentary sequence exposed at the southern margin of Madigan Gulf at Kati Thanda – Lake Eyre (KT-LE), Australia's largest lake. The ∼15 m high cliff outcrop includes 6 m of aeolian sediments, capping a ∼0.5 m beach/shoreline facies containing abundant Coxiella (aquatic gastropod) unconformably overlying 5–6 m of fluvio-lacustrine facies. The base of the outcrop and the playa floor comprises shallow and deeper water laminated lacustrine sediments. We re-examine the stratigraphic sequence using detailed excavations, micromorphological analysis and geochemical characterisation (X-ray fluorescence, X-ray diffraction, palaeoecology, stable isotope analysis of gypsum hydration water and biogenic carbonates, rare earth element analysis) and present a revised chronology using single-grain optically stimulated luminescence (OSL) within a Bayesian framework. Our new chronostratigraphic data generally supports previous interpretations for Williams Point, but crucially refines the timing of several of the key sedimentological units. The deeper-water lacustrine facies on the lake floor, unconformably overlying the Miocene Etadunna Formation, were deposited 206 ± 13 ka (232–169 ka, 95% credible interval; C.I.). A palaeoplaya, or oxidised shallow lake deposits, formed at 153 ± 11 ka (175–131 ka, 95% C.I.) and the uppermost shallow water lacustrine facies at the base of the cliff was deposited at 131 ± 9 ka (150–113 ka, 95% C.I.). An unconformity separates these sediments from the overlying fluvio-lacustrine phase, securely constrained (with eight OSL samples) to 86 ± 4 ka (95–78 ka, 95% C.I.). The isotopic composition of the palaeo-lake water (δ18O and δD), reconstructed from the hydration water of syndepositional gypsum formed in-situ in these fluvio-lacustrine sediments, indicates wetter conditions at 95–78 ka than at ca. 232–131 ka. Based on the provenance analysis these fluvio-lacustrine and lacustrine sediments were sourced from the northern catchments within the Lake Eyre basin but with an additional contribution from the northern Flinders Ranges. An erosional unconformity separates this sedimentary unit from the overlying Coxiella beach facies, which itself dates to 71 ± 4 ka (79–63 ka; 95% C.I.). This beach facies is interpreted to represent a regressional shoreline or near-shore deposit formed during Marine Isotope Stage [MIS] 4. This is the most reliable palaeolake level indicator in the sequence and indicates a maximum water depth of 12 m. The overlying Williams Point aeolian unit (WPAU) dates to 49 ± 4 ka (56–41 ka, 95% C.I.), slightly younger than previous estimates. The modelled age for WPAU overlaps with (and is within uncertainty of) the last KT-LE megalake phase, which reached +5 m AHD at 48 ± 2 ka. However, considering its elevation (−3 to +3 m AHD), the age of this gypsiferous aeolian unit demands that it accreted as KT-LE was entering a playa phase with lengthy periods of exposed lake floor. In turn, this means that the putative Genyornis newtoni (a megafaunal flightless bird) which laid its eggs in the gypsiferous dunes, went extinct during a time of hydrological transformation. These results bring fresh perspectives to a site that has held a heavy sway over previous views of the Quaternary history of Australia's arid zone. • Williams Point, at Kati Thanda- Lake Eyre shows episodic sedimentation in a lacustrine setting from 230 to 131 ka and fluvio-lacustrine deposition at 86 ka. • Coxiella beach facies were deposited at 71 ka, showing water depths of 12 m. • Rare earth elements show northern catchments supplied water and discharge in MIS 7–4. • Gypsiferous aeolian sedimentation occurred at 49 ka contemporaneously with the last mega lake highstand. • Genyornis newtoni (a megafaunal flightless bird) went extinct during a time of hydrological transformation. [ABSTRACT FROM AUTHOR]

The early Paleogene environment and climate of East Asia are poorly understood. To improve knowledge, we investigated the palynological record of well ZK0303 in the southwest Jianghan Basin, Hubei Province (central China). The well lithology comprises three intervals whose lithofacies represent the deposits of a saline lake: anhydrite/silty mudstone, halite/mudstone, and dolomite/siltstone. Based on a study of 37 palynological samples, three assemblages were recognized. Assemblage A, which correlates with Paleocene, is dominated by Ephedripites and contains a high proportion of thermophilic and xerophytic taxa. Assemblage B, which correlates with the early Eocene, is dominated by Taxodiaceaepollenites and hygrophilous taxa while the proportion of xerophytes is generally low. Assemblage C, probably early Eocene too, is dominated by Ephedripites and contains higher numbers of xerophytic species while hygrophilous species decrease to nearly half of their earlier abundances. These palynological data show that the early Paleogene climate of the Jianghan Basin experienced a transition from hot and arid to warm and humid conditions, with the latter period interrupted by short arid intervals. Afterwards, hot-arid conditions prevailed again. The reconstructed desert shrub and mountain forest vegetation suggests that the regional Paleocene landscape resulted from basin and range tectonics. Under the influence of a hot and arid climate controlled by global circulation patterns and rain-shadow effects, desert landscape and evaporites were formed in central China during the early Paleogene, whilst humid climate and forest vegetation prevailed in central China under the influence of the Paleocene-Eocene Thermal Maximum (PETM). • The lake in the early Paleogene Jianghan Basin experienced the evolution from brackish playa lake, shallow and semi-deep saline lake, deep saline lake and brackish playa lake again. • Hot and arid climate in the Jianghan Basin during the Paleocene-Eocene was caused by the subtropical anticyclone in East Asia and rain-shadow effects. • The basin centre represented a desert landscape whilst surrounding mountains were covered by forests under the influence of hot and arid climate. • Abundant precipitation occurred during the PETM in the Jianghan Basin, and forests expanded from the surrounding mountains into the basin. [ABSTRACT FROM AUTHOR]

This paper sheds light on the hydrodynamic conditions of transport and sedimentary effects of wind-induced water currents produced during strong windstorms in low gradient systems. Repeated field surveys were conducted in a playa lake in central Spain to determine the impacts of major winter storms on the bed form morphology in real time. The succession of storms that passed through the area from mid-December 2013 to early February 2014 left behind a variety of sedimentary structures: mainly ripple marks showing complex patterns and erosional structures. The latter include obstacle scours, grooves and other tool marks. In situ observations revealed that strong storm events in almost flat, extremely shallow lakes (less than 5 cm) have enough hydraulic energy to erode and remove high volumes of sediments and may also lead to large stones sliding across the bed, thus creating long grooves. Sole marks found in ancient continental successions have been typically attributed to fluvial conditions. We suggest that shallow lake basins should not be discounted when storm-generated structures are preserved in ancient rocks. The identification of such sedimentary structures provides valuable information for reconstructing hydrodynamic conditions and paleoclimatic conditions in semi-arid environments. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Expansive playa-lake systems situated in high-altitude piggyback basins are important and conspicuous components of both modern and ancient cordilleran orogenic systems. Extant playa lakes provide vital habitat for numerous endemic species, whereas sediments from these deposystems may record signals of climate change or develop natural resources over geological time. Laguna de los Pozuelos (North-west Argentina) provides the opportunity for an actualistic sedimentological and geochemical assessment of a piggyback basin playa lake in an area of critical interest for understanding Quaternary palaeoclimate dynamics. Silty clays and diatom ooze are the dominant playa-lake centre microfacies, with concentrations of total organic carbon and biogenic silica commonly exceeding 1·5 wt% in this sub-environment. Elemental and stable isotopic analyses point to a mixed organic matter composition in the playa-lake centre, with substantial contributions from algae and transported aquatic macrophytes. Bulk sediment and organic mass accumulation rates in the southern playa-lake centre approach 0·22 g cm−2 year−1 and 2·89 mg cm−2 year−1, respectively, indicating moderately rapid deposition with negligible deflation over historic time. Playa margin facies contain higher percentages of fragmented biogenic carbonate (ostracods and charophytes) and inorganically precipitated aragonite crusts due to seasonal pumping and evaporation of ground water. Organic matter accumulation is limited along these heavily bioturbated wet and dry mud flats. Fluvial-lacustrine transitional environments, which are key waterbird habitats, are either silty terminal splay (northern axis) or sandy deltas (southern axis) containing highly oxidized and partially allochthonous organic matter. Modern analogue data from Laguna de los Pozuelos provide key insights for: (i) environmental reconstructions of ancient lake sequences; and (ii) improving facies models for piggyback basins. [ABSTRACT FROM AUTHOR]

Medina playa lake, a Ramsar site in western Andalusia, is a brackish lowland lake of 120 ha with an average depth of 1 m. Water flows into Medina from its 1,748-ha watershed, but the hydrology of the lake has not previously been studied. This paper describes the application of a water budget model on a monthly scale over a 6-year period, based on a conceptual hydrological model, and considers different future scenarios after calibration to improve the understanding of the lake's hydrological functioning. Climatic variables from a nearby weather station and observational data (water-level evolution) were used to develop the model. Comparison of measured and predicted values demonstrated that each model component provided a reasonable output with a realistic interaction among the components. The model was then used to explore the potential consequences of land-use changes. Irrigation of olive groves would significantly reduce both the hydroperiod (becoming dry 15% of the time) and the average depth of the lake (water level <0.5 m 40% of the time). On the other hand, removal of an artificial overflow would double the average flooded surface area during high-water periods. The simulated water balance demonstrates that the catchment outputs are dominated by lake evaporation and surface outflow from the lake system to a creek. Discrepancies between predicted and observed water levels identify key areas of uncertainty for future empirical research. The study provides an improved basis for future hydrological management of the catchment and demonstrates the wider utility of this methodology in simulating this kind of system. This methodology provides a realistic appraisal of potential land-use management practices on a catchment-wide scale and allows predictions of the consequences of climate change. [ABSTRACT FROM AUTHOR]

Abstract: The Parecis Basin is a large intracratonic rift located in central Brazil and filled with Paleozoic carbonate, evaporite and siliciclastic sediments. The occurrence of gas seeps has recently attracted significant exploration interest by the Brazilian petroleum agency and by Petrobras. The continuously cored PB-01-RO well provided the first opportunity to study the depositional environments, diagenetic evolution and hydrocarbon potential of the largely unknown sedimentary successions of the Parecis Basin. The cored lithologies, belonging to the Siluro–Devonian (?) Pimenta Bueno Formation, are interpreted as deposited in playa-lake and ephemeral-stream environments. The deposits display a strong facies control on the diagenetic mineral assemblages and evolution. Diagenetic minerals in the ephemeral-stream deposits include eogenetic hematite and smectitic clay coats and quartz cement, and the mesogenetic process includes precipitation of sulfates (anhydrite and barite) and carbonates (calcite, dolomite and kutnahorite–ankerite–huntite), followed by partial dissolution of these carbonates and sulfates, and of feldspar grains. Telogenetic processes include the precipitation of hematite and kaolinite within secondary pores, and the replacement of anhydrite by gypsum. A second burial phase and mesodiagenesis is indicated by the precipitation of discrete K-feldspar crystals within moldic pores after dissolved feldspars, and by the illitization of etched, telogenetic kaolinite. The playa-lake deposits show early diagenetic dolomitization of lime mud, precipitation of anhydrite nodules and extensive silicification. The anhydrite nodules were replaced by gypsum and chalcedony during telodiagenesis. Potential source rocks are locally represented by organic shales. The fluvial sandstones show fair reservoir quality and limited compaction, as indicated by their intergranular volume, suggesting that the succession has undergone moderate burial. Potential seals for hydrocarbon accumulations are provided by the evaporites and playa-lake mudstones. The presence of an active petroleum system in the basin, as indicated by the gas seeps, suggests a good hydrocarbon exploration potential for the Parecis Basin, gas and stresses the importance of studying the depositional and diagenetic evolution of its sedimentary successions. [Copyright &y& Elsevier]

Lake Santa Ana is located in the Mexican central plateau, a semiarid region characterized by low rainfall and high evaporation rates. Because of the area's climatic conditions, most of its few existing lakes and reservoirs are ephemeral, with significantly reduced surface areas during the dry season. Mexican authorities currently pay little or no attention to these special aquatic ecosystems. As a consequence, several of these waterbodies are severely degraded in regard to both water quantity and quality. As a result, this report describes Lake Santa Ana as a case study. Several water quality parameters, including physicochemical, microbiological and heavy metal concentrations, were measured at eight sampling sites in the lake, and four sites in the lake basin, in 2005. Some dissolved ions were also analysed in 2007 in the lake, and in a well located close to the lake, in order to evaluate possible interactions between groundwater and surface waters. These study results indicate that the lake does not have significant interactions with groundwater in the local aquifer. Most of the measured water quality parameters do not meet the international suggested standards for inland surface waters to sustain aquatic life, and preserve the habitat for both endemic and migratory waterfowl. Loss of aquatic habitats puts at risk the value of the central portion of Mexico as a migratory route for North American waterfowl species. [ABSTRACT FROM AUTHOR]

The Tacutu Basin formed from the rifts system that occurred in the Caribbean region during the Mesozoic and culminated with in the opening of the North Atlantic Ocean. It evolved as a half-graben inserted in the Guiana Shield north of the Amazonian Craton. The Pirara Formation corresponds to the rift phase of the evolution of this basin, however the studies characterizing this unit are very scarce and little accurate due to the absence of outcrops. Therefore, there is much debate about the origin and depositional environment of the Pirara Formation, as some authors argue that the basin was episodically connected to the sea during the rifting, whereas others claim that was a continental-lacustrine environment, under arid to semi-arid climatic conditions. This work was based on investigations carried out on recently drilled rock cores of the Pirara Formation, which provides substantial new information regarding lithological and sedimentological data. The main objective was to characterize the lithofacies petrography palynofacies and constrains the paleoenvironmental interpretation of this unit. Three main lithofacies were identified: marlstone, siltstone, and black shale, with the latter yielding TOC content between 5% and 13.7% and organic matter consisting of phytoclasts, palynomorphs, and amorphous particles. Highly hypersaline conditions are indicated by the presence of pseudomorphs of evaporitic minerals, occurring in the marlstone and siltstone facies. Conversely no marine components take place in the palynological assemblages. The results demonstrate that the Pirara Formation represents a playa lake environment that evolved in the Southern Caribbean region in the Late Jurassic-Early Cretaceous during the opening of the Central Atlantic Ocean. • The Tacutu Basin developed during the Mesozoic. • The samples of black shale facies present high TOC values, ranging from 5.5% to 13.7%. • The Pirara Formation represents a hypersaline lake system that developed in a rift basin related to the opening of the Central Atlantic Ocean. [ABSTRACT FROM AUTHOR]

This study describes the application of a water run-off model for Lake Santa Ana, Mexico, developed through the combined application of two simulation models: the Watershed Modelling System (WMS) and the Hydrologic Modelling System (HEC-HMS). The WMS was used to estimate the geometric parameters of the hydrographic basin from a digital elevation model and geographical information describing the location of the hydraulic infrastructure developed in the basin in recent years. The HEC-HMS was used to estimate the run-off hydrographs, by using historical rainfall data and calibrating the model with the observed hydrometric data. The lake bathymetry was taken into account in order to estimate the lake's water balance. Recent observations indicate that anthropogenic activities have modified the natural run-off features of the lake basin. The magnitude of these modifications was estimated by linking the WMS and HEC-HMS models. Application of these linked tools allowed the successful estimation of the modified basin limits and hydraulic behaviour of Lake Santa Ana. [ABSTRACT FROM AUTHOR]

The Lower Triassic Rogenstein Member of the Buntsandstein Formation produces gas at the De Wijk and Wanneperveen fields, NE Netherlands and consists mainly of claystones with intercalated oolitic limestone beds. The excellent reservoir properties of the oolites (φ= 20-30%; k = 5-4000 mD) are predominantly controlled by depositional facies. Oolitic limestones are interpreted as the storm and wave deposits of a shallow, desert lake located in the Central European Buntsandstein Basin. The vertical sequence of lithofacies in the Rogenstein Member indicates cyclic changes of relative lake level. The reservoir rock is vertically arranged in a three-fold hierarchy of cycles, recognised both in cores and wireline logs. These cycles are a key to understanding the distribution of reservoir facies, and are used as the basis for a high-resolution sequence stratigraphic correlation of the reservoir units. Slight regional-scale thickness variations of the Rogenstein Member (in the order of tens of metres) are interpreted as the effects of differential subsidence associated with the inherited Palaeozoic structural framework. The depositional basin can be subdivided into subtle palaeo-highs and -lows which controlled facies distribution during Rogenstein deposition. Oolitic limestones show their greatest lateral extent and thickest development in the Middle Rogenstein during large-scale maximum flooding. Potential reservoir rocks (decimetre to metres thick) are present in the NE Netherlands, in particular in the Lauwerszee Trough and the Lower Saxony Basin, where abundant gas shows of 200 - 4000 ppm CH4 have been recorded. Preserved primary porosity is interpreted to be a result of rapid burial in subtle depositional palaeo-lows in this area. The thickest, amalgamated oolite intervals (tens of metres thick) occur in the eastern part of the Central Netherlands Basin. Because of poor reservoir properties, other areas appear to be less promising in terms of Rogenstein exploration potential. [ABSTRACT FROM AUTHOR]

Abstract: Lake model of the Upper Cretaceous Jindong Formation in Korea was established on the basis of sedimentological and palaeobiological records of the playa lake and sheetflood deposits and their palaeoenvironmental implications. The playa lake and sheetflood deposits of the Jindong Formation are characterized by the common presence of traces of vanished evaporites, complicated polygonal desiccation cracks and rainprints, the pedogenic carbonate development, and the preservation of invertebrate traces and dinosaur and bird tracks. The traces of vanished evaporites including halite and sulphate evaporite occur as evaporite pseudopmorphs and moulds. The occurrence of all of the evaporite minerals as traces suggests that flooding stages persisted much longer than evaporation and desiccation stages. Invertebrates, birds, and dinosaurs inhabited the playa lake environment of the Upper Cretaceous Jindong Lake. The Jindong Lake formed by the combination of humid source area and arid depositional site due to an orographic effect in fault-bounded basin. Extensive development of the playa lake and sheetflood deposits with evaporite mineral casts and very limited association of shoreline deposits in the Jindong Formation are characteristic of closed lake, and the Jindong Lake is compared to a lake formed in partly drained closed basin. The aggradation of mudflat deposits indicates continued subsidence of the basin and continuation of an underfilled lake basin. The Jindong Lake expanded and stabilized as a playa lake surrounded by dry to saline mudflats, and palaeoclimate and subsidence rates changed little throughout the period of the Jindong Lake development. [Copyright &y& Elsevier]

Lacustrine stromatolites of the Norian Arnstadt Formation (“Steinmergelkeuper”) occur on top of asymmetric flooding–evaporation cycles of a closed lake basin. They have been investigated with regard to associated lithofacies and biota, microfabric and stable carbon and oxygen isotopes. The stromatolites of the “Middle Grey Series” are brecciated and reworked by a flooding event of a subsequent lake cycle. They comprise agglutinated stromatolites rich in fish scales as well as skeletal stromatolites composed of a rhythmically grown dendroid micropeloidal framework. The latter are characterized by a shift towards positive δ13C values relative to the associated lake carbonates. This points to an effective photosynthesis in biofilm calcification at low concentrations in dissolved inorganic carbon (DIC) in a perennial fresh to brackish water lake. The stromatolites of the “Upper Red Series” occur on top of perennial lake cycles intercalated between playa lake deposits. The fine-grained stromatolites are poor in microfabric characteristics but show a significant covariation of δ18O and δ13C. This points to evaporation/degassing acting as driving mechanism in biofilm calcification. The lack of biotic effects on carbon isotope fractionation may reflect high concentrations in dissolved inorganic carbon. Skeletal oncoids, which occur as allochthonous components within an intraformational lag deposit of the “Upper Red Series”, are composed of cyanobacterial tubes and probably represent lowest saline lakes with only poor DIC buffering. Stable isotope signatures in conjunction with stromatolite microfabric analyses may be used as a proxy of DIC concentrations in ancient closed lakes. [ABSTRACT FROM AUTHOR]

Perennial lakes lasting several decades occupied Silver Lake playa, the terminus of the Mojave River, as recently as 390 ± 90 and 3620 ± 70 BP. Flood routings from the Mojave River headwaters to its terminal playa, and water balance calculations for the resulting lakes, indicate that floods comparable in magnitude to the largest floods in the modern record must occur almost annually to generate and maintain perennial lakes. In contrast, the modern floods of this magnitude have recurrence intervals greater than 18 years. Such an increase in flood frequency is required even if lake evaporation is reduced by as much as 50%. Modern extreme floods of the Mojave River are related to meridional atmospheric circulation and a southeastward shift in the winter low pressure center over the North Pacific Ocean, causing vigorous storms over the headwaters in the San Bernardino Mountains of southern California. This winter pattern probably occurred more frequently to induce the large number of storms and floods needed to form the middle and late Holocene lakes in Silver Lake playa. [ABSTRACT FROM PUBLISHER]

Lacustrine strata record long-term variations in climatic and tectonic perturbations during orogen evolution. Here we use the sedimentological record of the early to middle Miocene intramontane lacustrine Pranjani Basin (Serbia) to study tectonic and climatic variations during the evolution of the Dinaridic orogen. Our study focuses on a Mg-clay-bearing succession that belongs to the second depositional cycle. A detailed sedimentological, mineralogical and geochemical study shows that the investigated Mg-clays bearing succession consists of an alternation of smectite- (± analcime or sepiolite), dolomite-sepiolite and sepiolite layers. We interpret this high-order cyclicity to have been driven by variable water availability, i.e. by the interplay between runoff, groundwater influx and evaporation. Furthermore, we relate these pulses in water variability to wet and dry intervals under semi-arid to arid climatic conditions. Dry intervals produced a negative water balance promoting the deposition of sepiolite - and dolomite - dominated facies. Wet intervals and a positive water balance stimulated higher terrestrial input and thus favored the deposition of smectite-dominated facies. Our new data combined with a review of previous studies reveal longer-term basin-wide lake level and chemistry fluctuations, which we relate to closed and open lake phases. We suggest that these phases can be explained by alternating humid and arid phases superimposed on tectonically induced uplift and subsidence. The arid phases led to lake shrinking and deposition of an evaporite-bearing succession. During the intervening humid phase, the lake expanded. In contrast to the lakes formed in the external part of the Dinarides, the lakes that existed in its internal part contain evaporite-bearing successions, indicating that this arid phase was regionally extensive and possibly orographically controlled. • Mg-clay bearing succession reveals changing lake level and chemistry over time. • Lake cycles can be linked to wet and dry palaeoclimate cycles. • Deposition took place in saline-alkaline conditions under semi-arid to arid climate. • During Miocene evaporite-bearing successions were spread across the Internal Dinarides. • The distribution of the evaporite-bearing successions in the Dinarides is possibly controlled by orographic rainshadow effect. [ABSTRACT FROM AUTHOR]

The exhumed Lodève Basin (Hérault, France) provides a rich suite of outcrops showing diagenetic Ba–Pb–Fe–Cu fronts trapped in karst system in Cambrian dolomites during the Triassic post-rift exhumation of the basin. The sedimentological analysis on 10 sites in the basin reveals that barites-sulfides fronts formed during humid-arid climate fluctuations and the emplacement of a shallow lake environment. The fabric of ore deposits, the microthermometry of fluid inclusions entrapped within barites and the strontium/sulfur isotopic compositions of barite-sulfides associations indicate two distinct groups of mineralizations, Type I and Type II, which are contemporaneous but resulting from different processes. The synsedimentary mineralization of the Type I, the presence of only primary single-phase liquid fluid inclusions within barite crystals and the gradual increase of δ34S for both barites and chalcopyrites with depth (from −7 to +18.9‰ V-CDT) suggest ore precipitation close to the vadose zone under bacterial sulfate reduction (BSR) in a confined sulfate-rich playa lake aquifer. The similar 87Sr/86S ratios between barites and the overlying Triassic evaporites indicate that the barium and strontium derived directly from the overlying sulfate-rich lake. For the Type II, the high homogenization temperature of fluid inclusions entrapped within barite (modal Th between 60 and 80 °C) and the association with hydrocarbon markers, confirm the participation of deeper basinal brines in addition to downward percolating sulfates derived from the lake environment. The high positive values of δ34S for both barites and sulfides are typical of a precipitation linked to the combined action between anaerobic oxidation of methane and sulfate reduction (AOM-SR) at the sulfate-methane transition zone (SMTZ) during hydrocarbon migration. Similar 87Sr/86Sr ratios between Middle Triassic barites and previous Late Permian barites confirm that the source of metals precipitated at the SMTZ originated from the dissolution of anterior ore deposits located in the sulfate-depleted zone. This study links very shallow metallogenesis processes to reworking of MVT ore deposits by the action of sulfate-reducing bacteria around hydrocarbon seeps in a karstic environment. • Barite-sulfides fronts in meteoric karsts during the Triassic post-rift burial of the Lodève Basin (Hérault, France). • Karstology/sedimentology coupled with analyses of texture, fluid inclusions and sulfur/strontium isotopes in ore deposits. • Synsedimentary to early diagenetic continental mineralizations at the sulfate-methane transition during hydrocarbon ascent. • Metallogenic model: karst dynamics, climate changes, metals and hydrocarbon migration, bacterial mediation. [ABSTRACT FROM AUTHOR]