Post-eocene biofacies,palaeoenvironments and palaeogeography of the Bengal Basin,India

The Bengal Basin is known for the extensive development of a thick Cretaceous— Tertiary sedimentary sequence in the eastern part of India. The basin has undergone several phases of transgressions, regressions, periodic uplifts and localised negative movements throughout the period of its evolution. The sedimentation up to the end of the Eocene was largely under the influence of a major transgressive phase which was later replaced by a regressive phase on account of the uplift and resulting marine retreat. in this paper, an analysis of the microfaunal distribution, biofacies and sedimentary and tectonic history is made for reconstruction of the palaeoenvironmental conditions and palaeogeography of the Bengal Basin relating to the post-Eocene regressive phase of evolution.During the Oligocene—Early Miocene, the open marine conditions existing since the Eocene were progressively modified on account of the regression into more brackish, lagoonal and estuarine types. A typical prograding delta started to spread over a large part of the marginal area of the basin. The rocks of the Barail Group, formed under the transitional environments of the delta, are found to occur in almost all the major geo-provinces of the basin. The sedimentary environments and characteristics of the rocks were ultimately controlled by the configurations of the respective geo-provinces. The negative movements in the Miocene along certain marginal areas were associated with the marine transgressive phase giving rise to the Surma Group. This transgressive phase was, however, short lived and its impact was not equally felt in all areas. The northeastern region was still uplifted which favoured an almost continuous existence of the deltaic phase.By the end of Miocene a greater part of the basin underwent a strong tectonic upheaval which was possibly the precursor of the main Himalayan orogeny. The intermontane depressions formed in the uplifted areas were the depositional sites for the Tipam Group and younger beds in Plio-Pleistocene times. The rapidly eroded debris from the highlands spread over a wide area towards the south under the influence of the river system of the Ganga and Brahmaputra which has transformed the original basinal areas into a large modern delta complex.     

Le Lias et le Dogger du sud du Bassin parisien (France) : rôle de la tectonique syn-sédimentaire et reconstitutions paléogéographiques à l'échelle de la biozone d'ammonite

The Lias and Dogger series in the southern Paris Basin outcrops are precisely dated following the ammonite biozonation scale. In these series, the depositional environment context is accurately identified and thus various isopic zones can bee recognized. From the outcrop study, the depositional sequence and the tectonics events are also distinguished. The poorly dated subsurface data should be not anymore interpreted as diagraphic signatures, with the traditional peak to peak correlation. They now need to be analysed according to the geodynamic evolution of each isopic zone. The Liassic transgressive series (in the Armorican continent) and the Dogger platforms numerous carbonate bodies are correlated at biostratigraphic scale, throughout the whole southern Paris Basin. Subsequently, paleogeographic maps are established and based on depositional sequences. The basin evolution image changes radically. This shows clearly that the complexes carbonate bodies layout prohibits any depositional environment interpretation and any isopach mapping at geological stage level. If not, the carbonate platforms of different age would be amalgamated, without any connection with the reality. Over the time, paleogeographic maps show syn-sedimentary short wavelength deformations, more or less well expressed according to the local sedimentary context. During the Lias and the Dogger, three steps can be distinguished in the southern Paris Basin. Hettangian to Lower Aalenian, the progressive increase in accommodation drives to total immersion of the continental areas; the maximum of accommodation during the Middle Toarcian entails uniform sedimentary conditions. However, short wavelength deformations persist. The major accidents defining the isopic zones are mainly North-South oriented. Middle Aalenian to Middle Bathonian, isopic zones are contrasted, controlled by the North-South accidents but also the North West-South East ones ; the variable accommodation allowed the development of regional sedimentary gaps and shallow limestone progradations on a marly area (so called “Sillon marneux”) ; tectonics events correspond to the Tethyan and the North Sea riftings influences. Upper Bathonian to Upper Oxfordian, the North West-South East tectonics accidents are particularly active; this tectonic phase could be associated to the thermal event, described in the Paris Basin and announcing the Malm depositional environment.     

Autochthonous outer ramp sedimentation: The Alamogordo Member of the Lake Valley Formation,New Mexico

Summary Paleozoic carbonate ramp sedimentation has generally been described in terms of downlapping clinoforms composed of allochthonous sediment derived from shallower environments. However, during transgressive episodes when carbonate sediment production is low and down slope sediment transport by gravity becomes inactive, autochthonous carbonate sediment accumulates in vertical stacks of essentially in situ sediment. Autochthonous outer ramp deposition is probably a part of many Paleozoic ramp strata, but has heretofore not been recognized because of the general absence of adequate exposures. Evidence of autochthonous, in situ deposition and preservation of sediments in a starved setting is well displayed in the Alamogordo Member of the Lake Valley Formation in south central New Mexico. This evidence includes: 1) beds and bed sets that are individually continuous and traceable along ramp slope for 32 km, 2) down-ramp sequential distributions of depth-sensitive organisms and assemblages but patchy distribution of rock types, 3) lack of sedimentary structures indicative of transport, 4) well preserved, unabraded fossils, 5) the common occurrence of fossils in life position, 6) beds traceable into and through mounds 7) bed thickness trends ascribed to biotic productivity, and 8) geopetal structures in original position. Integrated paleontologic, sedimentologic, and stratigraphic data provide information about depositional processes and setting. The depositional slope was approximately 0.5^o based on the distribution of fossil algae; this is comparable to dips reported for other Mississippian homoclinal ramps. An oxygen minimum zone may have impinged on the ramp during a major flooding event. Shifts in biotic gradients from bed to bed reveal transgressive-regressive patterns that would not be resolvable without detailed paleontological evidence. The Alamogordo Member formed as a result of transgressive and early highstand starved carbonate sedimentation along a narrow, homoclinal outer ramp. The surface of maximum flooding and the boundary between the TST and HST are within the Alamogordo Member.     

Filling the North European Early/Middle Eocene (Ypresian/Lutetian) boundary gap: Insights from the Pyrenean continental to deep-marine record

The Early/Middle Eocene (Ypresian/Lutetian) transition is represented by a hiatus in many North European sections, including those in which the classic stratotypes were originally defined. However, the Global Stratotype Section and Point of the Lutetian Stage, which is still pending definition, should be placed at a globally correlatable event included within that unrepresented interval. The Pyrenean Eocene outcrops display sedimentary successions that offer the rare opportunity to analyse the Ypresian/Lutetian boundary interval in almost continuous sections and in very different settings. Seven reference stratigraphic sections were selected on the basis of their quality and correlated by means of biomagnetostratigraphic data. This correlation framework casts light on the sequence of chronostratigraphic events that characterize the Ypresian/Lutetian boundary interval, which may prove useful in defining the main correlation criterion of the base of the Lutetian.All of the Pyrenean sections show a similar sedimentary evolution, despite being up to 350 km apart from each other, containing deposits of different origins (intrabasinal carbonate sediments, siliciclastic sediments sourced from the Iberian plate, and terrigenous sediments sourced from the uplifting Pyrenees) and despite having been accumulated in different sedimentary environments (from continental to deep marine) and in different geodynamic settings (piggy-back basin, foreland basin and cratonic margin). This common evolution can be readily interpreted in terms of a sea-level driven depositional sequence whose lowstand and transgressive systems tracts are included within the Ypresian/Lutetian boundary interval. The Pyrenean Ypresian/Lutetian depositional sequence can reasonably be correlated with depositional sequences from classic North European areas, shedding light on the palaeoenvironmental history which in those areas has not been recorded. Furthermore, these depositional sequences may possibly correlate with others from the Antarctic Ocean and from New Jersey, as well as with oceanic temperature variations, suggesting that they might be the result of climatically-driven glacioeustatic sea-level changes. Should this hypothesis prove correct, it would confirm previous suggestions that the onset of Antarctic glaciations needs to be backshifted to the late Ypresian at least.     

BRIZ1 and BRIZ2 Proteins Form a Heteromeric E3 Ligase Complex Required for Seed Germination and Post-germination Growth in Arabidopsis thaliana

Ubiquitin pathway E3 ligases are an important component conferring specificity and regulation in ubiquitin attachment to substrate proteins. The Arabidopsis thaliana RING (Really Interesting New Gene) domain-containing proteins BRIZ1 and BRIZ2 are essential for normal seed germination and post-germination growth. Loss of either BRIZ1 (At2g42160) or BRIZ2 (At2g26000) results in a severe phenotype. Heterozygous parents produce progeny that segregate 3:1 for wild-type:growth-arrested seedlings. Homozygous T-DNA insertion lines are recovered for BRIZ1 and BRIZ2 after introduction of a transgene containing the respective coding sequence, demonstrating that disruption of BRIZ1 or BRIZ2 in the T-DNA insertion lines is responsible for the observed phenotype. Both proteins have multiple predicted domains in addition to the RING domain as follows: a BRAP2 (BRCA1-Associated Protein 2), a ZnF UBP (Zinc Finger Ubiquitin Binding protein), and a coiled-coil domain. In vitro, both BRIZ1 and BRIZ2 are active as E3 ligases but only BRIZ2 binds ubiquitin. In vitro synthesized and purified recombinant BRIZ1 and BRIZ2 preferentially form hetero-oligomers rather than homo-oligomers, and the coiled-coil domain is necessary and sufficient for this interaction. BRIZ1 and BRIZ2 co-purify after expression in tobacco leaves, which also requires the coiled-coil domain. BRIZ1 and BRIZ2 coding regions with substitutions in the RING domain are inactive in vitro and, after introduction, fail to complement their respective mutant lines. In our current model, BRIZ1 and BRIZ2 together are required for formation of a functional ubiquitin E3 ligase in vivo, and this complex is required for germination and early seedling growth.     

Integrated analyses of litho- and biofacies in a Pliocene cyclothemic, alluvial to shallow marine succession (Tuscany, Italy)

Lithofacies analysis of the upper part of the Pliocene succession of the Valdelsa basin (central Italy) unravelled a number of depositional environments, ranging from alluvial plain to coastal, to marine. Strata are arranged in a hierarchy of elementary and composite unconformity-bounded units. A palaeoecological study of macro- (molluscs) and microfossils (pollen, dinocysts, foraminifera) allowed to finely reconstruct sub-environments within fine-grained terrestrial, coastal and marine deposits and thence to track the spatial and temporal change of physical conditions. The stacking pattern of sedimentary units highlights the lateral switching of onshore-offshore gradients and documents relative sea-level changes. These units are interpreted in a sequence stratigraphic framework. Elementary depositional sequences are arranged to form six composite depositional sequences, in turn encased within two major synthems. This hierarchy of unconformity-bounded sedimentary units suggests that sea-level variation has occurred at different time-frequencies. Glacio-eustasy and active tectonism are discussed as the main forcing factors regulating the different scales of sedimentary cyclicity.     

Depositional facies and cyclic patterns in a subtidal-dominated ramp during the Early-Middle Ordovician in the western Tarim Basin (NW China)

Due to a long-term transgression since the Early Cambrian, an extensive shallow-water carbonate platform was developed in the entire Tarim Basin (NW China). During the deposition of the Yingshan Formation (Early-Middle Ordovician), a carbonate ramp system was formed in the intrashelf basin in the Bachu-Keping area of the western basin. Four well-exposed outcrop sections were selected to investigate their depositional facies, cycles, and sequences, as well as the depositional evolution. Detailed facies analyses permit the recognition of three depositional facies associations, including peritidal, semi-restricted subtidal, and open-marine subtidal facies, and eleven types of lithofacies. These are vertically arranged into meter-scale, shallowing-upward peritidal, semi-restricted subtidal, and open-marine subtidal cycles, in the span of Milankovitch frequency bands, suggesting a dominant control of Earth’s orbital forcing on the cyclic sedimentation on the platform. On the basis of vertical facies (or lithofacies) and cycle stacking patterns, as well as accommodation changes illustrated graphically by Fischer plots at all studied sections, six third-order depositional sequences are recognized and consist of lower transgressive and upper regressive parts. In shallow depositional settings, the transgressive packages are dominated by thicker-than-average, shallow subtidal cycles, whereas the regressive parts are mainly represented by thinner-than-average, relatively shallow subtidal to peritidal cycles. In relatively deep environments, however, the transgressive and regressive successions display the opposite trends of cycle stacking patterns, i.e., thinner-than-average subtidal cycles of transgressive packages. Sequence boundaries are mainly characterized by laterally traceable, transitional zones without apparent subaerial exposure features. Good correlation of the long-term changes in accommodation space inferred from vertical facies and cycle stacking patterns with sea-level fluctuations elsewhere around the world suggests an overriding eustatic control on cycle origination, platform building-up and evolution during the Early-Middle Ordovician, although with localized influences of syndepositional faulting and depositional settings.     

Facies distribution and sequence stratigraphy of the Coniacian–Santonian succession of the Bangestan Palaeo-high in the Bangestan Anticline,SW Iran

This study is focused on the sedimentary environments, facies distribution, and sequence stratigraphy of the Coniacian–Santonian sediments of the Bangestan Palaeo-high in the Bangestan Anticline (Zagros, Iran). These sediments are subdivided into nine microfacies types belonging to various sedimentary environments, ranging from continental lacustrine to very shallow and relatively deep-water (hemipelagic to pelagic) marine environments. The lower boundary of the studied sections is characterised by an unconformity. The lacustrine and very shallow marine sediments at the base of the studied sections are interpreted as a lowstand system tract. The establishment of an open shelf carbonate platform took place during the transgressive system tract. The maximum flooding zone of the Early Santonian is an important surface because it extends from the distal to the proximal part of the depositional environment.     

Environmental control on the biogeographical distribution of Desmanella (Soricomorpha,Mammalia) in the Miocene of the Iberian Peninsula

Abstract: This paper reports the first record of Desmanella (Mammalia, Soricomorpha) from the Granada Basin in southern Iberian Peninsula, which represents its south‐westernmost occurrence in all Eurasia. It is a controversial taxon whose systematic assignment has been discussed for a long time. This genus belongs to the family Talpidae, a group of insectivores that include extant moles, shrew moles and desmans. Desmanella was very abundant in the late Miocene and early Pliocene of Eurasia, including several basins of northern Iberian Peninsula, but it has not been found until now in southern Iberia. Previous studies have shown that the faunal record and the climatic conditions during the Neogene in the Granada Basin were different from other areas of the Iberian Peninsula. The particular distribution of Desmanella supports the hypothesis that specific climatic features (wetter than neighbouring areas) prevailed in the Granada Basin during the late Turolian (late Miocene).     

Facies analysis of the old Red Sandstone of Spitsbergen (Wood Bay Formation): Reconstruction of the depositional environments and implications of basin development

Summary The object of this paper is to provide a facies guide that helps subsequent workers recognizing different facies and palaeoenvironments of the terrestrial old Red Sandstone exposed in central N Spitsbergen. Sediments of the Early Devonian Wood Bay Formation represent continental molasse deposition under arid to semi-arid climatic conditions in three main depositional environments (rivers, alluvial plains, perennial lakes) represented by characteristic lithologies, sedimentary structures and microfacies. River channel deposits, consisting of conglomerates, very coarse-to very fine-grained sandstones and sandy siltstones are generally arranged in successive fining-upward sequences marked by specific sedimentary structures in a particular order. The sediments reflect the bed, mixed and suspended load of low sinuosity braided to high sinuosity meandering rivers. Adjacent overbank areas (levees, crevasse splays) and extensive alluvial plains are represented by reddish-brown, fine-grained sandstones to sandy siltstones and silty mudstones. The sediments are the accumulated, mixed and suspended load of floodwaters, which recurrently inundated the lowlands. Various lithofacies types, facies associations and sequences reflect the local formation of palaeosols, ephemeral flood lakes and boggy areas with persistent high water tables. Multicoloured, calcareous successions and single lime-stone beds intercalated in the red beds represent the depositional products of perennial, low relief, low-energy lakes, which developed in topographic depressions of the alluvial plains. The sediments reflect deposition in deep-water, littoral and palustrine sub-environments, forming regressive, shallowing-upward sequences in the central lake areas. The overall arrangement of the various facies reflects a terrestrial basin that developed from a steep-sloped, high-energy, river-dominated molasse trough into a level, lowenergy coastal plain, marked by broad mud flats and the formation of extensive perennial lakes.     

Figures sédimentaireset traces d'origine biologique du Trias moyen de la bordure orientale du Massif Central signification sédimentologique et paléoécologique

The sandstones with foot-prints of reptiles and saltcasts from the Middle Triassic of the eastern border of the Massif Central (France) show a striking reptilian ichnofauna. The numerous sedimentary figures and trace fossils which are described here allow to deduce the following characteristics of the depositional environment: shallow water, lower flow regime, periodical increase of salinity. The reptiles used to pass through that environment where numerous stretches of water alternated with emerged, plant overgrown areas.     

Short-term responses of the understory to the removal of plant functional groups in the cold-temperate deciduous forest

It is widely believed that functional diversity contributes to the stability of ecosystems. Indeed, greater redundancy among species within functional groups and greater complementarity among functional groups within communities should increase the resistance and resilience of ecosystems. In the present study, we tested for functional group complementarity by examining how the loss of specific functional groups may alter the role that other groups play in ecosystem functions. We removed different functional groups, one at a time, from the understory of three maple-dominated forests in southern Québec (Canada) and followed the understory response over a 2-year period. The experimental design included a control and five removal treatments. Five functional groups were defined: spring-flowering ephemeral species; spring-flowering persistent species; summer-flowering species; fern species; and seedlings and juveniles of woody species. Richness, cover, soil pH and organic matter content were determined after two years of removal. The results of our experiment revealed that richness was significantly lower than what we expected when spring-flowering persistent species or seedlings and juveniles of woody species were removed, suggesting not only direct but also indirect positive effects of both of these groups on understory richness (mostly through effects on summer-flowering species and fern species). Removal of the seedlings and juveniles of woody species and, to a lesser extent, of spring-flowering persistent species and of fern species lead to a decrease in the cover of summer-flowering species, implying a positive effect of the former groups on the latter. The cover–richness relationship in the control and in each one of the five removal treatments was positive and well fitted by a linear regression. Yet, the slope of the relationship differed among treatments, but not between the control and any one of the removal treatments (pair-wise comparisons). Our results suggest that the different functional groups are complementary and that positive interactions predominate over negative ones. Contrary to common belief, understory plants can respond quite rapidly to changes in community functional composition. Although we have not investigated the specific mechanisms responsible for the short-term responses reported here, we suggest that complex intergroup interactions may favour functional diversity and enhance ecosystem functions.     

Facies architecture,depositional environments,and sequence stratigraphy of the Middle Cambrian Fasham and Deh-Sufiyan Formations in the central Alborz,Iran

Based on their lithologic characteristics and stratal geometries, the Middle Cambrian Fasham and Deh-Sufiyan Formations of the lower Mila Group in the Central Alborz, northern Iran, exhibit 39 lithofacies representing several supratidal to deep subtidal facies belts. The siliciclastic successions of the Fasham Formation are divided into two facies associations, suggesting deposition in a tide-dominated, open-mouthed estuarine setting. The mixed, predominantly carbonate successions of the Deh-Sufiyan Formation are grouped into ten facies associations. Four depositional zones are recognized on the Deh-Sufiyan ramp: basinal, outer ramp (deep subtidal associations), mid ramp (shallow subtidal to lower intertidal associations), and inner ramp (shoal and upper intertidal to supratidal associations). These facies associations are arranged in small-scale sedimentary cycles, i.e., peritidal, shallow subtidal, and deep subtidal cycles. These cycles reflect spatial differences in the reaction of the depositional system to small-scale relative sea-level changes. Small-scale cycles are stacked into medium-scale cycles that in turn are building blocks of large-scale cycles. Systematic changes in stacking pattern (cycle thickness, cycle type, and facies proportion) allow to reconstruct long-term changes in sea-level. Six large-scale cycles (S1–S6) have been identified and are interpreted as depositional sequences showing retrogradational (transgressive systems tract) and progradational (highstand systems tract) packages of facies associations. The six depositional sequences provide the basis for inter-regional sequence stratigraphic correlations and have been controlled by eustatic sea-level changes.     

Biogeographical Boundaries,Functional Group Structure and Diversity of Rocky Shore Communities along the Argentinean Coast

We investigate the extent to which functional structure and spatial variability of intertidal communities coincide with major biogeographical boundaries, areas where extensive compositional changes in the biota are observed over a limited geographic extension. We then investigate whether spatial variation in the biomass of functional groups, over geographic (10′s km) and local (10′s m) scales, could be associated to species diversity within and among these groups. Functional community structure expressed as abundance (density, cover and biomass) and composition of major functional groups was quantified through field surveys at 20 rocky intertidal shores spanning six degrees of latitude along the southwest Atlantic coast of Argentina and extending across the boundaries between the Argentinean and Magellanic Provinces. Patterns of abundance of individual functional groups were not uniformly matched with biogeographical regions. Only ephemeral algae showed an abrupt geographical discontinuity coincident with changes in biogeographic boundaries, and this was limited to the mid intertidal zone. We identified 3–4 main ‘groups’ of sites in terms of the total and relative abundance of the major functional groups, but these did not coincide with biogeographical boundaries, nor did they follow latitudinal arrangement. Thus, processes that determine the functional structure of these intertidal communities are insensitive to biogeographical boundaries. Over both geographical and local spatial scales, and for most functional groups and tidal levels, increases in species richness within the functional group was significantly associated to increased total biomass and reduced spatial variability of the group. These results suggest that species belonging to the same functional group are sufficiently uncorrelated over space (i.e. metres and site-to-site ) to stabilize patterns of biomass variability and, in this manner, provide a buffer, or “insurance”, against spatial variability in environmental conditions.     

Temporal dynamics of marginal steppic vegetation over a 26‐year period of substantial environmental change

Questions: (1) Is climate a strong driver of vegetation dynamics, including interannual variation, in a range margin steppic community? (2) Are there long‐term trends in cover and species richness in this community, and are these consistent across species groups and species within groups? (3) Can long‐term trends in plant community data be related to variation in local climate over the last three decades? Location: A range margin steppic grassland community in central Germany. Methods: Cover, number and size of all individuals of all plant species present in three permanent 1‐m² plots were recorded in spring for 26 years (1980–2005). Climatic data for the study area were used to determine the best climatic predictor for each plant community, functional group and species variable (annual data and interannual variation) using best subsets regression. Results: April and autumn temperature showed the highest correlation with total cover and species richness and with interannual variations of cover and richness. However, key climate drivers differed between the five most abundant species. Similarly, total cover and number and cover of perennials significantly decreased over time, while no trend was found for the cover and number of annuals. However, within functional groups there were also contrasting species‐specific responses. Long‐term temperature increases and high interannual variability in both temperature and precipitation were strongly related to long‐term trends and interannual variations in plant community data. Conclusions: Temporal trends in vegetation were strongly associated with temporal trends in climate at the study site, with key roles for autumn and spring temperature and precipitation. Dynamics of functional groups and species within groups and their relationships to changes in temperature and precipitation reveal complex long‐term and interannual patterns that cannot be inferred from short‐term studies with only one or a few individual species. Our results also highlight that responses detected at the functional group level may mask contrasting responses within functional groups. We discuss the implications of these findings for attempts to predict the future response of biodiversity to climate change.     

Predator occurrence and perceived predation risk determine grouping behavior in guanaco (Lama guanicoe)

Grouping behavior of social ungulates may depend on both predator occurrence and perceived predation risk associated with habitat structure, reproductive state, and density of conspecifics. Over 3 years, we studied grouping behavior of guanaco (Lama guanicoe) families in Chilean Patagonia during the birthing season and determined their response to variation in predator occurrence and perceived predation risk (habitat structure, calf/adult rate, and density of conspecifics). We considered the effect of two predators, puma (Puma concolor) and culpeo fox (Lycalopex culpaeus). We measured two common (family group size and vigilance) and one novel (family group cohesion) behavioral responses of guanaco. Our results show that guanaco family groups adapted their grouping behavior to both predator occurrence and perceived predation risk. Larger family groups were found in open habitats and areas with high puma occurrence, while guanacos stayed in small family groups in areas with high shrub cover or low visibility. Group cohesion increased in areas with higher occurrence of pumas and culpeo foxes, and also increased in smaller family groups and in areas with low guanaco density. Vigilance (number of vigilant adults) was mainly related to group size and visibility, increasing in areas with low visibility, while residual vigilance (vigilance after removing the group‐size effect) did not vary with the explanatory variables examined. Our results suggest that a mix of predator occurrence and perceived predation risk influences guanaco grouping behavior and highlights the importance of evaluating different antipredator responses together and considering all predator species in studies aimed at understanding ungulate behavior.     

Sedimentary response to basin inversion: Mid cretaceous-early tertiary pre- to syndeformational deposition at the Areif El Naqa anticline (Sinai, Egypt)

Summary The Areif El Naqa domal anticline in northeastern Sinai is part of the ‘Syrian Arc’ which represents an intraplate orogen that has been formed since the late Cretaceous by inversion of an older half-gaben system as a consequence of the collision of the African and Eurasian plates. The here studied pre- and syn-deformational Upper Albian to Lower Eocene sedimentary succession in the anticline was formed under shallow marine to hemipelagic conditions resulting in predominantly carbonate lithologies with only subordinate siliciclastic intercalations. The depositional history at Areif El Naqa has been reconstructed in terms of sequence stratigraphy on the basis of detailed sedimentological, biostratigraphical, and paleoecological investigations of ten sections including comparisons with age-equivalent successions further north and south as well as published data. Following a late Triassic-early Cretaceous extensional period, tectonically rather quiet conditions prevailed during deposition of the Albian-Turonian successions. Inversion started around the Coniacian. Three main phases of uplift have been determined for the Areif El Naqa anticline on the basis of evidence from lateral facies and thickness changes, local development of pronounced hiatuses, and in comparison to the sequence stratigraphic development in the tectonically quiet region of central east Sinai. The first major compressional phase is interpreted to have taken place in Coniacian-early Santonian times. It is characterized by pronounced facies and thickness changes which were documented in an earlier study byBartov et al. (1980). Nevertheless, inter-regional sea level changes still controlled deposition at Areif El Naqa during this period. The second pulse of tectonic uplift is indicated for the late Campanian-early Maastrichtian. This is based on siliciclastic deposits which are interpreted as having been reworked from older siliciclastic rocks uplifted in the anticlinal core. The third compressional pulse is inferred to be of middle Paleocene to early Eocene age as evidenced by a major hiatus in sections on the northern anticlinal flank. The uplift history at Areif El Naqa has been compared with the tectonic development in other parts of the Syrian Arc and in general seems to reflect major movements which occurred throughout the anticlines of the fold belt.     

Miocene carbonate factories in the syn-rift Sardinia Graben Subbasins (Italy)

Summary Miocene syn-rift carbonate production areas are exposed in south-eastern Sardinia (Italy) along the eastern side of the Plio-Pleistocene Campidano Graben. Here the downfaulted margins of the Oligo-Miocene Sardinia rift-basin crop out with a complex alignment of smaller subbasins. Carbonate factories developed during the Aquitanian times in these tectonically controlled small depositional subbasins, where terrigenous input might be high due to the erosion of the uplifted pre-Neogene substrata. Terrigenous deposits generally acted as passive substratum for pioneer communities of rhodalgal-type (red algae, ostreids, bryozoans) and locally evolved into coral-dominated assemblages. Carbonate production areas occur on tilted, uplifted blocks as well as along basement margins. These have varying organic communities and facies characteristics strongly dependent on different environmental conditions. In footwall areas, devoid of (or with a very reduced) terrigenous supply, open foramol carbonate factories occur with aggradational-progradational stratigraphic geometries. The resulting pure calcareous successions are organized in sequences, bounded by tectonically driven discontinuity surfaces. In sectors close to the hinterland area, with a higher freshwater input and a consequent significant clastic input, coral-dominated assemblages grew during long periods of quiescence between flash floods. Repeated coral-rich communities developed on thick wedges of terrigenous debris. Carbonate facies composition and distribution were mainly controlled by local syn-sedimentary tectonics and eustasy as well as by climate. However, although the inception of the carbonate factories was presumably not synchronous, their growth represented the response to a relative regional sea level rise subsequent to episodes of significant clastic supply: the expression of an early syn-rift stage. During the Burdigalian (N6 zone) a hemipelagic cover uniformly sealed the neritic successions. This basin wide drowning event appears to correspond to the transgressive system tract of the TB2.1 cycle ofHaq et al. (1987) but it can also be interpreted as the expression of an evolved syn-rift stage passing to late syn-rift and quiescence stages. Beneath the hemipelagic cover in some areas, ?late Aquitanian-early Burdigalian deep erosive surfaces, terrigenous clastics and paleosoils have been recognized. These suggest a relative sea level fall and may relate to the global sea level drop at the TB1-TB2 boundary (seeHaq et al., 1987) or to diacronous uplift of different fault blocks.     

Depositional system and response to sea level oscillations of the senonian rudist-bearing carbonate shelves. Examples from central Mediterranean areas

Summary  In the Late Cretaceous the carbonate platforms modified the organization of their depositional systems owing to vast and complex geologic events. In this view, detailed analyses have been made on Senonian shelf-to-slope rudist-bearing limestones resting on pre-Coniacian erosive surfaces or slope facies in the Nurra region (northwestern Sardinia, Italy), in the central-southern Apennines and in the Gargano area (central-southern Italy). The main characteristic of the analyzed deposits is the spreading of rudists in a context of foramol-type calcite-dominated benthonic sediment-producer communities. The reconstructed Senonian depositional environments match a large complex of unprotected shelves that produced loose, diagenetically stable mollusc-dominated bioclastic debris which were not involved in significantin situ cementation processes. High energy episodes led to repeated and more or less total remobilization of the sedimentary sheet. On the shelves, both storm- and wind-induced currents and waves exercised a strong driving control on the sedimentary arrangement of the shifting biogenic sediments. The latter constituted large coalescing sheets of winnowed, loose, fine-to-coarse skeletal sands. Sandy sediments were easily involved in remobilization processes across the shelves toward the redepositional sites. Transport modality largely depended on the granular composition of the sediments. The early and almost continuous sweeping of the finer fraction (bioeroded-derived silt) resulted in an effective pre-sorting of the skeletal debris stored in the Senonian open shelf settings.In situ preservation potentiality of the produced skeletal material was low and huge amounts of sands may have concurred in forming slope aprons. In the studied successions a two-stage evolution is documented during the Senonian.

Environmental changes reflected by palynomorphs in the early Middle Ordovician Hanadir Member of the Qasim Formation, Saudi Arabia

Core samples from the QASIM-801 (QSIM-801) water well in the Qasim Region of central Saudi Arabia were investigated palynologically. The interval studied contains the transgressive succession from the Sajir Member of the Saq Formation to the Hanadir Member of the Qasim Formation, and yields well-preserved and abundant cryptospores, microphytoplankton (acritarchs and chlorophycean algae), and chitinozoans, indicative of a Darriwilian (Llanvirn) age. The lowermost portion of the cored interval from the upper Sajir Member consists of fine-grained sandstones deposited in tidal flat, and shallow-marine settings. It is characterized by abundant and diverse cryptospores (permanent tetrads, dyads, monads), cuticle-like phytoclasts, and a low diversity assemblage of marine palynomorphs. The upper part of the cored interval from the Hanadir Member is composed of hemipelagic to pelagic, organic-rich, graptolitic shales, and micaceous shales, of middle- to outer-shelf depositional settings, which yield abundant marine palynomorphs (acritarchs and chitinozoans). Cryptospore-bearing horizons are interspersed in the succession. Changes in the composition of palynomorph assemblages reflect higher frequency environmental changes within an overall transgressive succession. Four new acritarch species are described in open nomenclature, Tyrannus sp. A, Clypeolus sp. A,?Pulvinosphaeridium sp. A, and?Tinacula sp. A.