Transgressive Events Research Articles

Possible freshwater dinoflagellate cysts and colonial algae from the Upper Jurassic strata of the Surat Basin, Australia

ABSTRACTJurassic sedimentary successions in eastern Australia are widely thought to have been deposited in nonmarine environments. Thus, the discovery of low-diversity dinoflagellate cyst assemblages with associated colonial algae in the Walloon Coal Measures of the western Surat Basin provides new evidence of either a short-lived marine transgression or the very rare occurrence of nonmarine dinoflagellate cysts in pre-Cretaceous strata. Their small size, thin walls and simple proximate shapes are typical of freshwater to brackish dinoflagellate cysts, as are the low species richness and high dominance nature of the assemblages. Two new species of dinoflagellate cysts (Moorodinium crispa sp. nov. and Skuadinium fusum sp. nov.) and a new species of colonial algae (Palambages pariunta sp. nov.) are described from these assemblages. Tidal channel and tidal mudflat facies associated with these assemblages provide evidence of a possible upper estuarine setting. Support for a marine incursion is provided by U–Pb dating. This yielded an age of 150.11 ± 0.04 Ma (∼100 m above the dinoflagellate cyst assemblage in the Indy 3 well) that ties to an episode of high eustatic sea level during the Tithonian. Thus, a marine transgressive event during the Tithonian may have allowed dinoflagellates to migrate into the interior of the Australian continent. If these dinoflagellate cysts are found more widely, rather than being just an isolated occurrence in this well, they may provide a useful correlative tool for tracing distinctive brackish to marginal marine flooding surfaces in continental successions in eastern Australia.

Postrift deltaic sedimentation in western Kachchh Basin: Insights from ichnology and sedimentology

The postrift stage in the pericratonic Kachchh Rift Basin of western India is represented by a thick sequence of a diachronous megadelta system. The deposition of this deltaic sequence was initiated during the mid-Kimmeridgian and ended in the Albian. The sedimentation was interrupted by two transgressive events demarcating three subcycles within the megadelta system. The present study addresses the older mid-Kimmeridgian to Tithonian “Jhuran Delta”. An attempt is made here to delineate the nature of the Jhuran Delta using the ichnological and sedimentological parameters. The Jhuran Delta, which consists of 14 lithofacies, is grouped into seven lithofacies associations corresponding to the prodelta, subaqueous gravity flow, delta front, distributary channel, distributary mouth bar, and shoreface depositional environments along with a transgressive unit overlapping the lower delta of the megadelta system. Three distinct stages of deltaic evolution are delineated along with the fourth stage of transgression and delta destruction. The prodelta environment of Stage I is characterized by moderate ichnodiversity represented by nine recurring ichnotaxa, suggesting alternating brackish and fully saline water conditions, which indicate river-dominated deltaic sedimentation. Stage II shows a marked increase in the influence of river (fresh water) water, as indicated by a submarine mass failure that includes debris flow, chaotic and contorted structures, sediment gravity-failure and water-escape structures and suggesting a higher rate of sedimentation. Ichnologically, this phase indicates low ichnodiversity with sporadic occurrences of Ophiomorpha and Palaeophycus. Stage III indicates the mixed dominance of river and wave processes. Sediments deposited in the delta front environment show moderate ichnodiversity with nine ichnotaxa. The distributary mouth bar environment comprises 6 recurring ichnotaxa including the ichnoassemblages of both river and marine wave environments. Integrated ichnological data suggest deposition in a mixed environment. The Jhuran Delta stage ended with a marine transgressive event and reworking of the deltaic sands, which were overlain by a thick shoreface deposit. Thus, the Upper Jurassic Jhuran Delta represents a river-dominated, wave-influenced delta.

Marine flooding surfaces recorded in Permian black shales and coal deposits of the Main Karoo Basin (South Africa): Implications for basin dynamics and cross-basin correlation: Discussion

The paper “Marine flooding surfaces recorded in Permian black shales and coal deposits of the Main Karoo Basin (South Africa): implications for basin dynamics and cross-basin correlation” by Götz et al. (2017) correlates the Whitehill Formation with the No. 5 coal seam on a reported prasinophyte/acritarch spike, which the authors claim indicates a basin-wide marine transgression in the Roadian. The study disregards lithostratigraphic, palynological and radio-isotopic age evidence to the contrary, which all support a Kungurian age for the Whitehill Formation, and cast doubt on the marine affinity of the acritarchs used for cross-basin correlation. Further evidence is required before a “major transgressive event” in the Karoo Basin can be supported by palynology.

Mid- to late Holocene geomorphological and hydrological changes in the south Taihu area of the Yangtze delta plain, China

The Taihu Plain of the Lower Yangtze valley, China was a centre of rice agriculture during the Neolithic period. Reasons for the rapid development of rice cultivation during this period, however, have not been fully understood for this coastal lowland, which is highly sensitive to sea-level change. To improve understanding of the geomorphological and hydrological context for evolution of prehistoric rice agriculture, two sediment cores (DTX4 and DTX10) in the East Tiaoxi River Plain, south Taihu Plain, were collected, and analysed for radiocarbon dating, diatoms, organic carbon and nitrogen stable isotopes (δ13C and δ15N), grain size and lithology. These multiproxy analyses revealed that prior to ca. 7500 cal. yr BP, the East Tiaoxi River Plain was a rapidly aggrading high-salinity estuary (the Palaeo-Taihu Estuary). After ca. 7500 cal. yr BP, low salinity conditions prevailed as a result of strong Yangtze freshwater discharge. Subsequently, seawater penetration occurred and saltmarsh developed between ca. 7000 and 6500 cal. yr BP due to accelerated relative sea-level rise. This transgression event influenced a large area of the Taihu Plain during the Holocene, as shown by multiple sediment records from previous studies. Persistent freshwater marsh (or subaerial land) formed due to dramatic shrinkage/closure of the Palaeo-Taihu Estuary after ca. 5600 cal. yr BP when sea level was relatively stable. We speculate that geomorphological and hydrological changes of the East Tiaoxi River Plain played an important role in agricultural development across the Taihu Plain during the Neolithic period. The closure of the Palaeo-Taihu Estuary and the formation of stable freshwater marsh (or subaerial land) after ca. 5600 cal. yr BP were critical preconditions encouraging the rapid rise of rice productivity in the Liangzhu period (5500–4500 cal. yr BP). This development changed the landscape and river systems, and thus provided adequate freshwater supply to the Taihu Plain.

Effects of brand transgressions on third-party consumers

PurposeBrand transgressions, characterized by service failure, are a frequent theme for marketing scholars. Their impact on satisfaction, trust and brand loyalty is of high interest. However, in assessing the influence of those events on third-party consumers, the literature is still lacking. The purpose of this paper is to explore how social distance explains the reactions of close and distant third-party consumers toward other consumers during a brand transgression event. Anger is analyzed as a driver of this process.Design/methodology/approachTwo experiments were conducted. Both studies presented a 3 (social distance: victim vs close third party vs distant third party) by 2 (severity: low vs high) between-subjects design. Respondents were asked to read a transgression scenario in a mobile phone service (study 1) and in a restaurant (study 2) and then completed scales that measured their affective reactions and evaluations of the relationship – satisfaction, trust, and loyalty intention – with the transgressing brand.FindingsThe results showed that transgression severity intensifies the effect of the brand transgression on consumer’s anger. Victims and close third parties demonstrated higher levels of anger compared to distant third-party consumers. In the case of severe transgressions, an experience of anger contagion between victims and close third-party consumers was responsible for the negative effect on the relationship evaluation of the transgressing brand compared to distant third-party consumers.Originality/valueThis study extends previous research about how social distance influences consumer-brand relationships and demonstrates the mediating role played by affective anger contagion.

Cyclostratigraphy across a Mississippian carbonate ramp in the Esfahan–Sirjan Basin, Iran: implications for the amplitudes and frequencies of sea-level fluctuations along the southern margin of the Paleotethys

The Tournaisian–Visean carbonate successions of the Esfahan–Sirjan Basin (ESB) from Sanandaj–Sirjan Zone, Iran, have been used to generate a sequence stratigraphic model that enhances facies characterization and improves paleoenvironmental interpretation of shallow marine successions deposited along the southern margin of the Paleotethys. Detailed facies analysis allowed to differentiate seven facies, which, in order of decreasing abundance, are: (1) shaly and marly, F1; (2) peloidal mudstones/wackestones, F2; (3) peloidal/bioclastic packstones, F3; (4) intraclastic/bioclastic packstones/grainstones, F4; (5) oolitic/bioclastic packstone/grainstone, F5; (6) sandy intraclastic/bioclastic grainstones, F6; (7) sandy oolitic/bioclastic grainstones, F7. The different facies can be grouped into three facies associations that correspond to different environments of a carbonate platform with ramp geometry (homoclinal), from outer ramp (F1 and F2), mid-ramp (F3, F4 and F6) to inner ramp areas (F5 and F7). Meter-scale cycles are the basic building blocks of shallow marine carbonate successions of the Tournaisian–Visean ramp of the ESB. Small-scale cycles are stacked into medium-scale cycles that in turn are building blocks of large-scale cycles. According to the recognized facies and the stacking pattern of high-frequency cycles across the ramp, five large-scale cycles in the southeastern outcrops (Tournaisian–Visean) and three large-scale cycles in the northwest outcrops (Visean) related to eustatic sea-level changes can be recognized. The overall retrogradational nature of the carbonate ramp, illustrated by both vertical facies relationships and the stacking patterns of high-frequency cycles within the third-order cycles, implies that the deposition of the Tournaisian–Visean successions mainly took place under a long-term transgressive sea-level trend. The stratigraphic architectural style of the sequences, characterized by the lack of lowstand deposits and exposure surfaces, associated with the evidence of progressive increase in the proportion of backstepping of facies belts across bounding surfaces and predominant subtidal characteristics, is in accordance with the long-term transgressive sea-level trend and greenhouse conditions during the Tournaisian–Visean. The continued transgression on this broad shelfal platform could lead to the shutdown of the shallow water carbonate factory, reduction in sediment supply or sediment transport towards the offshore setting and the development of give-up sequences. The association of transgressive events with the deposition of thick open-marine marls/shales is a common feature in Tournaisian to Visean times of the southern margin of the Paleotethys.

Lower Badenian coarse-grained Gilbert deltas in the southern margin of the Western Carpathian Foredeep basin

AbstractTwo coarse-grained Gilbert-type deltas in the Lower Badenian deposits along the southern margin of the Western Carpathian Foredeep (peripheral foreland basin) were newly interpreted. Facies characterizing a range of depositional processes are assigned to four facies associations — topset, foreset, bottomset and offshore marine pelagic deposits. The evidence of Gilbert deltas within open marine deposits reflects the formation of a basin with relatively steep margins connected with a relative sea level fall, erosion and incision. Formation, progradation and aggradation of the thick coarse-grained Gilbert delta piles generally indicate a dramatic increase of sediment supply from the hinterland, followed by both relatively continuous sediment delivery and an increase in accommodation space. Deltaic deposition is terminated by relatively rapid and extended drowning and is explained as a transgressive event. The lower Gilbert delta was significantly larger, more areally extended and reveals a more complicated stratigraphic architecture than the upper one. Its basal surface represents a sequence boundary and occurs around the Karpatian/Badenian stratigraphic limit. Two coeval deltaic branches were recognized in the lower delta with partly different stratigraphic arrangements. This different stratigraphic architecture is mostly explained by variations in the sediment delivery and /or predisposed paleotopography and paleobathymetry of the basin floor. The upper delta was recognized only in a restricted area. Its basal surface represents a sequence boundary probably reflecting a higher order cycle of a relative sea level rise and fall within the Lower Badenian. Evidence of two laterally and stratigraphically separated coarse-grained Gilbert deltas indicates two regional/basin wide transgressive/regressive cycles, but not necessarily of the same order. Provenance analysis reveals similar sources of both deltas. Several partial source areas were identified (Mesozoic carbonates of the Northern Calcareous Alps and the Western Carpathians, crystalline rocks of the eastern margin of the Bohemian Massif, older sedimentary infill of the Carpathian Foredeep and/or the North Alpine Foreland Basin, sedimentary rocks of the Western Carpathian/Alpine Flysch Zone).

ГОЛОЦЕНОВЫЙ МОРФОЛИТОГЕНЕЗ В ОЗЕРНЫХ КОТЛОВИНАХ ЮГО-ВОСТОЧНОГО ЗАБАЙКАЛЬЯ, "Геоморфология"

В статье рассматривается функционирование озерных бессточных бассейнов Даурии в голоцене. Выделены типы рельефообразования, связанные с трансгрессивными и регрессивными фазами развития озер, контролируемыми климатическими колебаниями. Трансгрессия сопровождается интеграцией отложений в котловинах за счет береговых процессов, криогенного выветривания, флювиальной, склоновой и биогенной аккумуляции. Регрессия - эоловой деформацией сухих днищ и склонов озерных депрессий, формированием котловин выдувания, выносом рыхлых отложений господствующими ветрами на юго-восток. Установлены события быстрого флювиального сноса большого объема материала в озерные понижения по падям временных водотоков 7-8.5 тыс. кал.л.н. и в переходное время между атлантической и суббореальной климатическими фазами. Наиболее детально прослежена смена условий рельефообразования и осадконакопления в позднем голоцене, отмечавшаяся каждые 500 лет. Выявлен период стабилизации уровней озер и формирования почвы в атлантическое время и два этапа активизации криогенных процессов около 9.2 и 3.5 тыс. кал.л.н., зафиксированные в отложениях первой террасы оз. Хара-Нур. Установлена тенденция сокращения площадей озер и повышения в морфолитогенезе роли эоловых процессов на фоне общей аридизации климата за последние 10 тыс.л.

Marine flooding surfaces recorded in Permian black shales and coal deposits of the Main Karoo Basin (South Africa): Implications for basin dynamics and cross-basin correlation

The marine origin of black shales in the context of the Permian postglacial development of the Karoo Basin, South Africa, is subject of an ongoing controversial discussion. Here, we present and discuss palynological and sedimentological data providing evidence of a transgressive event during the early Guadalupian. Palynofacies assemblages of the black shales of the southern basin include marine phytoplankton that exhibit peak abundance within the Whitehill shales and which also occur within siltstones and glauconitic sandstones on top of the No. 5 coal seam of the north-eastern basin. Palynostratigraphic control makes this marine signal a powerful tool for cross-basin correlation. Moreover, palynofacies analysis demonstrates a facies transition from terrestrial lacustrine and fluvio-deltaic in the northeast to deep marine in the south-western parts of the basin.

Seasonal variation of training, competition load and markers of wellness in an elite Gaelic football team

Constraining the timing of the postglacial transgression is of great significance to the origin of coastal wetlands distributed extensively in eastern China. The high-resolution chronological sequence from Xixi Wetland enabled us to explore interactions among the postglacial transgression, sedimentary response, and human activities in the surrounding Hangzhou Bay. Diversities of 12 ostracods, 24 foraminifera and remains of oyster shells, gastropods, testate amoebae, diatoms, and vascular plants are indicative of the sedimentary facies. Grain size variables together with microfaunal records revealed seven stages of sedimentary evolution since the middle Late Pleistocene: initial riverbed, first transgression event, floodplain, early lagoon, shallow marine bay, late lagoon, and final freshwater marsh. The Xixi Basin experienced two distinct transgression events and sea-level changes inferred from assemblages of ostracods and foraminifera. The first transgression event is a minor transgression related to the moderate intensity of Asian Monsoon and moderately high sea level during the early MIS 3. The second large-scale transgression event established the sedimentary pattern of the modern Xixi Basin. The finding of the transgression maximum in the early Holocene (about 11.0–7.0 cal ka BP) highlighted the problem of reliable time of high sea level, which is tightly related to the strong Asian Monsoon intensity and global rising sea level. Subsequent changes in the sedimentary environment played a key role on the Neolithic human activities around the Hangzhou Bay. The origin of the Xixi Wetland reflected the combined effects of a sand barrier and rising human activities since the middle Holocene.

Oil shale resources in Egypt: the present status and future vision

In Egypt, organic-rich sediments in the Duwi and Dakhla Formations of the Campanian-Danian age are customarily assigned as “oil shale” that occupies the middle latitudes of the country but may extend southward to Kurkur Oases. This oil shale belt has a vast worldwide extension, and it is considered as major oil- and gas-prone source rock in many places, especially in the Middle East. The sedimentation of the oil shale was triggered by the major transgression event that occurred during the Late Cretaceous. The lithology, type of kerogen, organic richness, and thickness of these organic-rich sediments vary markedly both on lateral and vertical scales. In Quseir area, the in-place geological reserves, of oil shale of the 800-kcal/kg quality, is estimated to be more than 9 billion tons that can produce 5.48 bbls equivalent upon retorting. Very optimistic resources are expected in the unexplored Nile Valley region. The factor analysis of data rank representing 1176 core samples and analysis of 58 major and trace elements besides Rock-Eval analyses point to five main controlling factors that control deposition of oil shale. The terrestrial indicators Al2O3, TiO2, Fe2O3, and K2O and the marine indicators Ca and Sr are oppositely loaded in the first factor. The second factor expresses the reducing conditions that prevailed during the deposition of the organic-rich marine environments. The euxinity of the basin is recognized by the third factor where sulfide and vanadium seem to be mutual. The fourth factor expresses the role of dolomitization while the fifth factor points to the humble role of oxidation. Considering the metric core samples, the highest TOC content recorded in the borehole drilled in Abu Tartur plateau is 3.6%, but it is about 14% for Quseir area. Regarding the spot samples in Quseir area, the highest TOC measured about 24%. It is not only the low TOC in Abu Tartur but also the kerogen type that is of type II + III, mostly of terrestrial origin (gas-prone) and lithology dominated by argillites. Organic richness is remarkable in Quseir-Safaga area, where the average TOC of 160-m-thick sequence is about 5%, with kerogen of type I or mixed I + II, mostly of marine origin (oil prone). The Dakhla Formation (Maastrichtian-Danian) is the richest in organic matter while Quseir Formation (Campanian) has the least organic richness and lowest kerogen quality. Detailed investigation on biomarkers confirms the relations among transgression, organic richness, kerogen type, and anoxic conditions. The organic matter is immature as witnessed by the low S1 values (<5%, in average), the low T max (<430 °C), the low vitrinite reflectance (<0.4%), and biomarker signature. The variation in the S1 values between 1 and 9% is attributed to the influence of tectonics associating the Red Sea rift. In Quseir-Safaga area, there are particular prolific horizons of oil shale that seem to be visible for utilization by different technologies of combustion and retorting. The content of the heavy metals and uranium, as well as the spent, is a significant benefit. The faulting, dragging, and steep tilting of beds in the Quseir-Safaga area shall remain a serious challenge for extensive utilization of the estimated in-place geological reserves.

Relative sea level rise, site distributions, and Neolithic settlement in the early to middle Holocene, Jiangsu Province, China

This study details the chronology and the human consequences of early- to mid-Holocene sea level rise and the related marine transgression and regression along the east coast of China. We use archaeological and environmental data to show that there was a significant marine transgressive event that began before 9000 cal. BP. This event reached its maximum extent inland and had the greatest impact on the Jiangsu region between 9000 and 8000 cal. BP. Because of this transgression, most of the low-lying parts of modern Jiangsu Province were either covered by seawater or were converted to a wetland environment that was unsuitable for long-term human settlements until ca. 7000 cal. BP. Between 7000 and 6000 cal. BP, the sea retreated and new lands became available for colonization. Humans rapidly moved into the newly emerged lands, which were ecologically rich with diverse and abundant plants, animals, fish, and shellfish. Evidence that human settlement were earliest in the northwest and generally expanded sout...

Constraints on sedimentary ages of the Chuanlinggou Formation in the Ming Tombs, Beijing, North China Craton: LA-ICP-MS and SHRIMP U–Pb dating of detrital zircons

Detrital zircons in five sedimentary samples, MC1 to MC5, from the bottom of the Chuanlinggou Formation in the Ming Tombs District, Beijing, were dated with the LA-ICP-MS and SHRIMP U–Pb methods. Age spectra of the five samples show a major peak at 2500 Ma and a secondary peak at 2000 Ma, suggesting their provenances were mainly from the crystalline basement of the North China Craton and the Trans-North China Orogen. The youngest zircon has an age of 1673 ± 44 Ma, indicating that the Chuanlinggou Formation was deposited after this age. From sample MC4 to MC5, lithology changed from a clastic rock (fine-grained sandstone) to a carbonate rock (fine-grained dolomite), suggesting that the depositional basin became progressively deeper. The age spectrum of sample MC5 shows a major peak at 2500 Ma and a secondary peak at 2000 Ma. Sample MC4, which is stratigraphically lower than sample MC5, only had one peak at 2500 Ma. We conclude that there was a transgressive event when sediments represented by MC5 was deposited, and seawater carried ca. 2000 Ma clastic materials to the basin where the Chuanlinggou Formation was deposited, leading to the addition of ca. 2000 Ma detritus. Our research indicates that the source area for the sediments became more extensive with time. We conclude that the Chuanlinggou Formation in the Ming Tombs District was deposited in a low-energy mud flat sedimentary environment in the inter-supra tidal zone because it is mainly composed of silty mudstone and fine-grained sandstone with relatively simple sedimentary structures.

The effects of Quaternary sea-level fluctuations on the evolutionary history of an endemic ground lizard (Tropidurus hygomi)

The Quaternary period is marked by many extensive glaciations and sea level oscillations, mainly during the Pleistocene. Sea level oscillations possibly shaped landscapes in coastal regions, which may have played an important role in the diversification of organisms that live in these areas. In this study, we investigated the population history of the lizard Tropidurus hygomi, which is endemic to a narrow region of the northeastern coast of Brazil, inhabiting areas of white sandy coastal dunes in the Restinga formation. We specifically asked: how did sea level changes in the Quaternary shape population structure and historical demography of T. hygomi? We collected 72 tissue samples throughout the distribution of the species and obtained sequences from the mitochondrial gene cytochrome b. Different tests for population structure identified five distinct mitochondrial DNA clusters (mtDNA clusters) in T. hygomi. Divergence time estimate showed that splits among these mtDNA clusters took place in the Pleistocene, and exhibited temporal agreement with marine transgressive events during these periods. As T. hygomi is a threatened species and our data suggest the presence of five mtDNA clusters, further conservation actions for this species should consider these independent mtDNA clusters in order to preserve the evolutionary history and the diversity within the species.

THE EVOLUTION OF CHANNEL SYSTEM IN THE NORTHEAST MALAY BASIN, TERENGGANU OFFSHORE

This study aims to evaluate the evolution of the channel system in the Pleistocene-Recent succession in the northeast Malay Basin based on channel morphologies. The variable types of channel morphologies were determined from seven seismic time slices of study area. The fluvial channel became wider and low-sinuous when the sea-level rise. Meanwhile, the fluvial channel became narrower and high-sinuous when sea levels decreased. The point bars are seen in the meandering curve of the high-sinuosity channel. This occurred because of the sea-level decrease and more sediment being deposited in the study area. The point bars morphology do not appear in the transgressive event. An oxbow lake appeared in the 525 ms seismic time slice and is labelled as the oldest channel system. The channel morphologies then changed, and the oxbow lake does not appear in the younger system channel (Recent). The channel morphology changes have been proven to be affected by global sea-level changes.

Sedimentary control on the formation of a multi-superimposed gas system in the development of key layers in the sequence framework

Based on core observations, well logs and test results of siderite-bearing mudstone from the Benxi Formation to the Member 2 of the Shanxi Formations in the Linxing block, northeastern Ordos Basin, a logging identification model for siderite-bearing mudstone (key layer) was established. The porosity characteristics and sealing property were quantitatively evaluated by logging data. Sedimentary control on the formation of multi-superimposed gas-bearing system in the development of key layers in the sequence framework was also discussed. The results showed that the siderite-bearing mudstone has obvious logging response characteristics, e.g., high photoelectric absorption cross-section index (PE), high density (DEN), high amplitude natural gamma ray (GR), low acoustic (AC), low resistivity (M2RX) and low neutron porosity (CNCF). The quantitatively evaluated results of the porosity characteristics and sealing property for the key layer showed that the key layer has the characteristics of low porosity (with an average of 1.20 percent), low permeability (with an average of 2.29 × 10−8μm2), and high breakthrough pressure (with an average of 12.32 MPa) in the study area. This layer acts as an impermeable gas barrier in a multi-superimposed gas system. The results also indicated that the material composition of the multi-superimposed gas-bearing system can be established by the sequence stratigraphic framework. The sedimentary evolution results in a cyclic rhythm of material composition vertically. The spatial distribution of the corresponding transgressive event layer near the maximum flooding surface (MFS) in the sequence framework restricts the spatial distribution of the key layer with high breakthrough pressure and low porosity, which constitutes the gas-bearing system boundary. The siderite-bearing mudstone formed near the MFS in the second-order sequence and constitutes a stable comparison of the first-order gas-bearing system boundary, which has a wide range of regional distribution and stable thickness. The siderite-bearing mudstone formed near the MFS in the third-order sequence is often incompletely preserved due to the late (underwater) diversion channel erosion and cutting. This layer forms the coal-bearing reservoirs, which we termed as a second-order gas-bearing system in adjacent third-order sequences to form a uniform gas-bearing system.

Depositional paleoenvironments of the Lower Permian (upper Cisuralian) carbonate succession of Paso Hondo Formation in Chiapas State, southeastern Mexico

The Paso Hondo Formation outcrops around of the Chicomuselo region, Chiapas State, Mexico. It is a Permian lithostratigraphic unit mainly composed of massive limestone which has been dated for the Artinskian-Kungurian (late Cisuralian). A microfacies analysis carried out on the carbonate rocks of a stratigraphic section, allowed for the first time the recognition of the depositional conditions that prevailed in the Chicomuselo region at the end of the Cisuralian. The facies associations studied allowed identifying different marine paleoenvironments related with a homoclinal carbonate ramp. The presence of anhydrite nodules, a mud-dominated carbonate production in euphotic zone (precursor of mudstones and packstones) and the presence of a diverse fauna mainly composed of photic-independent biota (mollusks, bryozoans, brachiopods and crinoids), indicate that the studied section was deposited in a relatively uniform low angle ramp. Thus, facies of different environments of inner ramp were detected, including those of a lagoon close to a peritidal area, with periodical restricted or open circulation, and open waters deposits influenced by the storm zone. In addition, mid-ramp facies were also observed.Facies associations of the basal levels on the studied section were mainly correlated with lagoonal shallow marine environments, being ostracods, calcispheres and peloids the dominant allochems. In contrast, there is a shift upwards to facies of open waters and mid-ramp environments, characterized by abundant skeletal grains of bryozoans, brachiopods and crinoids. The paleoenvironments recorded through the stratigraphic section were related with specific bathymetries, having a general tend towards the sea level rise. This record coincides with the global transgression event occurred during the Early Permian which have also been described for coeval localities of Texas and New Mexico in the United States and western Venezuela.

Tectonic and climatic controls on the late Pleistocene to Holocene evolution of Paleolake Ullum-Zonda in the Precordillera of the central Andes, Argentina

AbstractThe Ullum-Zonda tectonic depression located in the central Andes Precordillera records several lacustrine episodes from frequent natural damming of the San Juan River during the late Quaternary. We analyzed stratigraphic, geomorphic, and geologic data and obtained new radiocarbon ages for Paleolake Ullum-Zonda. Results show the existence of a late Pleistocene age (16.7–15.2 ka BP) unit and an early to middle Holocene (9475–7685 yr BP) unit. Subsurface data show lacustrine episodes were common during the late Pleistocene, with probably nine episodes occurring during that period. Two transgressive events are evident in the Holocene unit, dated to ~8420±30 and shortly after 7460±30 14C yr BP. The maximum extent of the paleolake occurred at 6930±30 14C yr BP, shortly before the lake desiccated. Fault propagation folds and growth strata in Quaternary alluvial deposits relate to the Villicum-Zonda Fault and may indicate early to middle Holocene activity for this fault. The deformation observed in an ancient shoreline of the paleolake could be related to middle to late Holocene activity of the Cerro Zonda Norte Fault at a mean vertical uplift rate of ~0.8 mm/yr in the hanging wall block.

Relative sea-level change in western New Guinea recorded by regional biostratigraphic data

We present new biostratigraphic analyses of approximately 200 outcrop samples and review biostratigraphic data from 136 public domain exploration wells across western New Guinea. Biostratigraphic ages and palaeodepositional environments were interpreted from occurrences of planktonic and larger benthic foraminifera, together with other fossils and environmental indicators where possible. These data were compared with existing geological maps and exploration well data to reconstruct the palaeogeography of western New Guinea from the Carboniferous to present day. In addition, we used the known bathyal preferences of fossils to generate a regional sea-level curve and compared this with global records of sea-level change over the same period. Our analyses of the biostratigraphic data identified two major transgressive-regressive cycles in regional relative sea-level, with the highest sea levels recorded during the Late Cretaceous and Late Miocene and terrestrial deposition prevalent across much of western New Guinea during the Late Paleozoic and Early Mesozoic. An increase in the abundance of carinate planktonic foraminifera indicates a subsequent phase of relative sea-level rise during a regional transgressive event between the Late Jurassic and Late Cretaceous. However, sea-levels dropped once more during a regressive event between the Late Cretaceous and the Paleogene. This resulted in widespread shallow water carbonate platform development in the Middle to Late Eocene. A minor transgressive event occurred during the Oligocene, but this ceased in the Early Miocene, likely due to the collision of the Australian continent with intra-Pacific island arcs. This Miocene collision event resulted in widespread uplift that is marked by a regional unconformity. Carbonate deposition continued in platforms that developed in shallow marine settings until these were drowned during another transgressive event in the Middle Miocene. This transgression reached its peak in the Late Miocene and was followed by a further regression culminating in the present day topographic expression of western New Guinea.

A Gerecse pannóniai puhatestűi és lelőhelyeik: rétegtan, őskörnyezet és fejlődéstörténet

A Gerecse földtani térképezése során a Magyar Földtani és Geofizikai Intézet geológusai új, vagy régen feledésbe merült és részletesen soha nem dokumentált pannóniai feltárásokat azonosítottak a hegység északi előterében, az onnan dél felé felnyúló völgyekben, és a hegység belsejében is. Az ezekből begyűjtött puhatestű fauna (kiegészítve a már korábban ismert tatai puhatestű faunával és régebbi gyűjteményi anyagokkal) és a feltárásokban megfigyelhető szedimentológiai jellemzők alapján a pannóniai rétegsor itt is, mint az egész Dunántúli-középhegység északnyugati peremén, egyetlen transzgresszív-regresszív ciklusból áll. A ciklus transzgresszív szárnyát a tatai téglagyári feltárásokban a vékony transzgresszív bázisrétegre települő Száki Formáció kékesszürke agyagja és az abban megőrződött mély szublitorális fauna, míg a Gerecse központi részén, a tardosi Vályus-kút környékén, 375 méter tengerszint feletti magasságban a lignites agyaggal kezdődő rétegsor fedőjében települő, szintén mély szublitorális puhatestűeket tartalmazó agyag képviseli. A dunaszentmiklósi Iván halála-völgyben valószínűleg egy szökőár hozta létre a kréta fekü anyagából képződött konglomerátumot, homokos mátrixában tömegesen megjelenő zárt (két teknős) pannóniai kagylóhéjakkal. Az üledékciklus regresszív szárnyát az Újfalui Formáció képződményei adják; ezek legjobb feltárásai a Gerecse északi előterében, a Neszmély környéki völgyekben (Nyáraska-völgy, Disznós-kúti-völgy, Csekendi-völgy) és Süttő környékén találhatók. A formációt felépítő felfelé sekélyedő, néhány méter vastag ciklusok faunája a kagylók uralta sekély szublitorális együttesekből, a csigák magas diverzitásával jellemzett litorális faunákból és végül mocsári puhatestű együttesekből áll. Gyűjteményi anyagokban előfordulnak folyóvízi fajok is. A transzgresszív szárny a Congeria czjzeki zóna felső részébe tartozik, míg a regresszív szárny a Lymnocardium ponticum zóna része; a teljes ciklus képződésének kora 9,4–8,7 millió év lehetett. A fáciesek elterjedése alapján a transzgresszió már tagolt térszínen játszódott le, majd az üledékképződéssel egyidejűleg is folyt a terület vetődéses deformációja, de a tatai és vályus-kúti rétegsorok közötti nagy magasságbeli különbség csak további vetőmozgásokkal, a Gerecse utólagos kiemelkedése nyomán jöhetett létre.