Mesozoic Stratigraphy

En la region de San Jose de Gracia, Ures, estado de Sonora, aflora una secuencia sedimentaria del Paleozoico inferior, que consiste en caliza oolitica, arenisca, lutita y limolita. Esta secuencia esta caracterizada por una abundante y diversa biota fosil que consiste en estructuras algales oncoidales, icnofosiles e invertebrados, entre estos, esponjas, braquiopodos, hiolitidos, trilobites y blastoideos. En este trabajo, se dan a conocer por primera vez dos especies de hiolitidos para la region de San Jose de Gracia, Hyolithes cf. H. sonora Lochman, 1952, que fue descrita para el Cambrico de Caborca en la region noroeste del estado de Sonora, y Haplophrentis reesei Babcock y Robison, 1988, por primera vez para Mexico, la cual fue referida antes para el Cambrico medio de la region norte de Utah, Estados Unidos de Norteamerica. La distribucion de los organismos cambricos de San Jose de Gracia, entre ellos los hiolitidos, muestra que existio una amplia provincia marina que comprendio Gr...

Exposures of the Te Kuiti Group sediments at Whangārei Harbour exhibit several distinct lithofacies within individual formations. These lithofacies exhibited unique sedimentary and biogenic characteristics, which were used to infer processes and environment of deposition. These paleoenvironmental inferences were leveraged with a compilation of published and unpublished data to determine if these sequences were, in fact, autochthonous as previously considered. Significant discrepancies in the depositional environments within facies showed that these sediments are incompatible with their geographic location and the general depositional trend of
these sequences across the harbour. The lithofacies of the Ruatangata Sandstone (lower Te Kuiti Group) showed concordant progressive shelf marine transgression during the Eocene across the Harbour and is still assumed
autochthonous.
The primary discrepancies in sequences and lithofacies are within the Whangārei Limestone Formation and the Onemama Formation, which exhibit varied depositional environments, mechanisms, substrate types, water energy levels, and sedimentary and biogenic structures.
The southern exposures of the Whangārei Limestone at Whangārei Harbour appear laterally continuous and seem to follow the general deepening trends during the Oligocene. Lower facies exhibit evidence of re-shallowing during the mid-late Oligocene and is thought to relate to tectonic influences as Isaac et al. (1994) proposed a propagation of a “wave-form bulge” in the rock mass as a sign of the advancing Northland Allochthon nappes in the northeast of Northland. The upper
facies depositing at bathyal depths by slumping or downslope creep records the rapid subsidence following the emplacement of the Northland Allochthon. These Mesozoic to Cenozoic sequences can still be considered autochthonous.
The Whangārei Limestone in the northern exposures show widely different lithotypes even in close geographical proximity and does not follow the general trends of deposition of the Te Kuiti Group sequences in the region and are deduced displaced limestone blocks related to the mass emplacement of the Northland Allochthon during the earliest Miocene.
The Onemama Formation (uppermost Te Kuiti Group) displays evidence of mass transport depositional processes with conflicting sedimentary/biogenic structures and bathymetric estimates. Its exact deposition and origin remain enigmatic and require further investigation. It is underlain and lensed by the Northland Allochthon lithologies, inferred as penecontemporaneous deposition. Paleoflow indicators across the exposures indicate a southeastern general direction.
Changes in the emplacement direction of allochthon are thought to relate to a detached olistolith before the main displaced nappes arrived at the Whangārei Area.
The sediments overlying the Te Kuiti sequences also showed important differences in thickness and followed the eastward younging trend. This suggests that possibly the whole CenozoicMesozoic sequences at Whangārei Harbour are displaced.

Basin analysis can assimilate structural, burial and thermal histories to predict hydrocarbon-prone zones in speculative areas. The validity of the modeling approach was field tested in the North Sea Viking Graben, an area for which good data are available. A recent BIRPS, deep seismic reflection profile across tectonic strike of the graben was interpreted and depth-converted with good well control. The burial and structural histories were determined by backstripping the chronostratigraphic layers using a one-dimensional fluid flow/compaction model on pseudo-wells. After removal of each sequence, the section was manually reconstructed. The thermal history was examined using thermal indicator tomography, extensional models and calculations of depth to detachment. Lack of resolution required that three different paleo-heat flow trends be tested to encompass the range in variability: a gradual warming trend, a constant heat flow through time, and a low heat flow until the Cretaceous-Tertiary boundary where a heat pulse occurred. Basement subsidence, extension, depth to detachment calculations, and thermal indicator inversions all suggest that the UK side of the graben has developed differently to the Norwegian section. The generation modelling predicts the position of the oil window in the cross-section. The areas where this window enveloped the Draupne Formation (Kimmeridge Clay) source rock broadly correlate with the positions of the Gullfaks, Statfjord and Thistle oilfields of the UK sector. However, in the Norwegian sector the Draupne Formation was generally overmature, except in the area around the Troll oilfield. Predicted Middle to Late Cretaceous generation in the rift axis may have caused updip oil migration towards the Horda platform. The correct prediction of off-prone zones validates the use of quantitative basin analysis as a tool for evaluating frontier areas where data are limited.

A suite of trace elements (TEs) characterized by an affinity to reducing environments, including molybdenum (Mo), uranium (U), vanadium (V), copper (Cu), and nickel (Ni), were used to investigate secular variations in environmental redox conditions during deposition of the Bächental bituminous marls (Bächentaler Bitumenmergel). These marls, which belong to the Sachrang Member of the Lower Jurassic Middle Allgäu Formation in the Northern Calcareous Alps, are subdivided on the basis of Al-normalized TE concentrations and concentration ratios into three units that correspond to major shifts in depositional redox conditions. The lower and upper units (Units 1 and 3, respectively) were deposited under suboxic to transiently anoxic conditions. The removal of TEs to the sediment was connected to siliciclastic input, diagenetic processes, and organic-matter accumulation in the sediment. In contrast, the middle unit (Unit 2) was characterized by intense anoxia as reflected in strong TE enrichments and peak total organic carbon (TOC) contents up to 13 %. Enrichment of TEs was linked mainly to adsorption onto organic matter in Unit 2, reflecting control of TE enrichment by the availability of an organic substrate. Comparison of inorganic and organic (e.g., pristane/phytane ratio, gammacerane index) geochemical proxies for environmental conditions permits detection of periods with elevated surface-water bioproductivity. A flourishing of algal and planktonic organisms contributed to the significant increase of TOC content at the base of Unit 2. This increase corresponds to the time-equivalent early Toarcian oceanic anoxic event characterized by the global occurrence of organic-rich sediments. Eine Auswahl an Spurenelementen (Mo, U, V, Cu, Ni), charakterisiert durch ihre Affinität zu reduzierenden Milieus, wurde verwendet um Variationen der vorherrschenden Redoxbedingungen während der Ablagerung der unterjurassischen Bächentaler Bitumenmergel (Sachrang-Member der Mittleren Allgäu-Formation in den Nördlichen Kalkalpen) zu untersuchen. Die Bitumenmergelabfolge wurde auf Basis dieser Spurenelementdaten in drei Einheiten unterteilt. Anorganisch-geochemische Parameter reflektieren wechselnde Umweltbedingungen während der Ablagerung der Bitumenmergel. Der untere und der obere Bereich (Units 1 und 3) der Bächentaler Bitumenmergel wurden unter suboxischen bis teils anoxischen Bedingungen abgelagert. Die Anreicherung der Spurenelemente im Sediment erfolgte durch siliziklastischen Eintrag, diagenetische Prozesse und Akkumulation von organischem Material. Maximalgehalte an Spurenelementen und von organischem Detritus (bis zu 13 %) bestätigen durchgehend anoxische Bedingungen während der Ablagerung des Mittelteils des Profils (Unit 2). Die Fixierung der Spurenelemente im Sediment erfolgte in diesem Bereich ausschließlich durch Adsorption an organischem Material. Folglich war die Verfügbarkeit von organischem Material der limitierende Faktor für die Spurenelementanreicherung. Der Vergleich der anorganisch-geochemischen und organisch-geochemischen (Pristan/Phytan-Verhältnis, Gammaceran Index) Parameter ermöglicht die Identifizierung von Perioden mit erhöhter Bioproduktivität. Demnach hat ein Aufblühen von algalen und planktonischen Organismen zu den signifikant hohen Gehalten an organischem Material an der Basis von Unit 2 beigetragen. Dieses Intervall entspricht dem Zeitraum des ozeanischen anoxischen Ereignisses des Unteren Toarciums, welches durch weltweites Auftreten von organisch-reichen Sedimenten charakterisiert wird.

Here we report for the first time on the presence of ichthyosaurs in Sicily, southern Italy. The deposit of origin (Mufara Formation) can be dated to the upper Carnian (Tuvalian substage) based on a typical association of ammonites, one of which ( Shastites  sp.) is embedded in the sediment still encrusting one of the bone specimens recently found. The latter consist of two isolated vertebral centra that are referred to the Ichthyosauria thanks to their disk-like shape (i.e. they are much taller than long) combined with the amphicelous condition, lack of transverse processes, and presence of rib articulations on the central sides. The largest specimen is more precisely an anterior dorsal vertebra from an adult individual, ascribed to Shastasauridae indet. By the presence of elongated reniform diapophyseal facets, cranially not truncated, and absence of parapophyses. The smaller specimen represents an anterior cervical element from an immature individual of a likely smaller-sized, in...

The Upper Miocene (Vallesian-Turolian) Unit II of the Teruel Graben comprises at its top a 25 m-thick sequence of palustrine deposits. Deposition of the entire unit commenced some 9 to 7 Ma ago in a halfgraben basin. Here, via a recent quarry, we examine in detail the lateral and vertical distribution of Unit II's palustrine facies and their features to determine the palaeogeography and main controls on deposit formation. Our findings suggest the deposits formed at a low-gradient lake margin with different energy levels. These energy levels controlled the type of primary deposit within the lake; wackestone to packstone sediments formed in low-energy conditions, whereas cross-bedded rudstones to floatstones formed under higher energy conditions, by erosion and redeposition of prior lacustrine deposits. Pedogenic and diagenetic modifications of the primary sediments took place during sedimentary discontinuities (SO) when the lacustrine sediments were subaerially exposed. These processes serve to explain the formation of eight different pal ustrine limestones: limestones with root traces, mottled limestones, brecciated limestones, flat pebble breccias, granular limestones, micro-karstified limestones with laminar ca1cretes, carbonate mounds and clayey limestones with laminar ca1cretes. Based on the features and thicknesses of the modified sediments five different morphological stages (I to V) of palustrine carbonates are defined. Stage I is characterized by incipient mottling and brecciation. Stage II shows mottling and strong brecciation that lead to the formation of intraclast breccias, in which the fragments are mostly "in situ". In Stage Ill, the primary fabric is totally changed; intraclasts have moved and may have lost their initial morphology. This Stage III may also be characterized by the formation of micro-karst. Stage IV is typified by the presence of coated grains and thin root mats. The chronological data available suggest that the formation of Stage III (lacustrine deposition + palustrine modification) would require about 40,000 yr. Facies and the SO record changes across short horizontal distances, and thus reflect the topography of prior sedimentation/modification events. Small (50 cm) highs with micro-karst have their SO counterparts in lower areas of the lake, in which the SO is indicated by desiccation and mottling. The topographic differences of the micro-karst were filled by intraclastic rudstones sourced by the adjacent carbonate flats. The example examined not only clearly sketches the morphology of ancient palustrine systems or wetlands, it also provides evidence that recycling of previous carbonate deposits played an important role as a sediment source, apart from biogenic or physical-chemical production processes. Our geochemical data indicate LMC (Low Magnesian Calcite) as the main component and Fe contents lower than 1%, except for the mottled areas that are richer in FeO. Stable isotope compositions provide 6 18 0 values close to-6.5%0 VPOB, and more varied 613C (-3.39 to-6.97%0 POB). Oxygen and carbon values reveal no covariation and clear trends are lacking. The homogeneity of 6 18 0 values reflects the intense effects of meteoric waters. The deposition of these palustrine limestones took place under suitable semi-arid to sub-humid climates. Climate could also have a role in determining subaerial exposure periods. However, its imprint is not easy to detect neither in the geochemical signals nor in the vertical arrangement of the facies. This could be attributed to climate changes probably occurring over shorter periods than those that can be recorded in this type of sediment, such as the astronomical precession cycles, and suggests the unsuitability of palustrine carbonates for detailed palaeoclimate analyses.

The late Ladinian (Middle Triassic) Xingyi Fauna from the Zhuganpo Member of the Falang Formation yields abundant and well-preserved marine reptiles. Bed-by-bed excavation at Wusha in Xingyi of Guizhou Province reveals two marine vertebrate assemblages in a fossiliferous horizons that span 5.1 m in total thickness. The lower assemblage is marked by the near-shore sauropterygians, including the pachypleurosaur Keichousaurus, the nothosaurians Nothosaurus and Lariosaurus, 2 with a strong paleobiogeographic affinity to western Tethys. The upper assemblage consists of oceanic ichthyosaurs and pistosaurs, including the large shastasaurid ichthyosaur Guizhouichthyosaurus, the euichthyosaur Qianichthyosaurus, pistosaurs Yunguisaurus and Wangosaurus, and the thalattosaur Xinpusaurus, with a closer paleobiogeographic affinity to North America. The coastal pachypleurosaur and nothosaurid sauropterygians disappeared in the upper assemblage, suggesting that they were replaced by an oceanic marine reptile community that emerged. The reptilian composition of the upper assemblage is similar to that of the Guanling Biota, which is of the Early Carnian (Late Triassic) in age and thus somewhat younger than the Xingyi Fauna. The ecological turnover of marine reptiles from near-shore to the open ocean community corresponds to the paleoenvironmental changes indicated by lithofacies analysis, δ 13 C and the global sea level changes.

Il sistema di campionamento costituisce un’evoluzione di un campionatore a valvole pneumatiche per gas disciolti realizzato in precedenza (Cosenza et al., 2008). Esso è stato progettato sulla base di particolari meccanici realizzati con macchine utensili e l’impiego di prodotti industriali, quali valvole pneumatiche, valvole swagelok, anelli di tenuta O-ring, raccordi con attacco rapido per aria compressa. Il sistema è costituito da una camera centrale, alle cui estremità vengono avvitate due valvole pneumatiche normalmente chiuse, le estremità esterne delle valvole vengono a loro volta chiuse mediante dei tappi di plastica dotate di opportuno anello O-ring. Quest’ultimo accorgimento serve a colmare con acqua il volume esterno alla chiusura pneumatica e di sigillare quest’ultimo allo scopo di ottenere una chiusura anche idraulica del campionatore. Particolarmente utile nel caso il cui il processo di estrazione del campione venga effettuato in tempi successivi. L’apparato è tenuto in...

Iron is known to stimulate surface ocean productivity, as well as intervene with bacterially-mediated processes of organic matter remineralization, during early diagenesis. In this paper, we examine the influence of iron supply on the geochemistry (trace metals, δ 34 S, organic matter) of sedimentary rocks deposited in a clastic-dominated marine ramp environment. To this end, we studied two Late Jurassic formations of the Boulonnais area (North-France). Both formations were deposited under quite similar conditions, but they differ in the reactive-iron supply they received. Only one of the two formations was affected by the particulate iron shuttle process. Our results indicate that 1) the iron shuttle may be recorded through concomitant enrichments in P, Mo, As and Sb; 2) a limited reactive-iron supply will allow the sulfurization of organic matter, even in a context of moderate productivity. Thus sulfurization can be a factor favoring a noticeable accumulation of organic matter: iron may thus be an important agent in the C cycle. 1. Introduction The geological rocks of the Late Jurassic times (Kimmeridgian-Tithonian), cropping out along the Boulonnais shore (Strait of Dover, Northern France; Fig. 1), represent a proximal, lateral equivalent of the Kimmeridge Clay Formation (when used with a proper name, the word Formation will be abbreviated as Fm.), famous as a major petroleum source rock. These formations accumulated in a clastic dominated ramp environment where the sedimentary succession is made up of an alternation of marlstone-dominated formations (called "Argiles") and sandstone-dominated formations (termed "Grès") reflecting a range of water depths from lower offshore to shoreface settings, respectively (e.g., Wignall, 1991;

Bentonite, a claystone formed from the devitrification of volcanic ash, demonstrates varying amounts of alteration in elemental concentrations through the transition from glass to clay. Many studies have sought to characterize and correlate bentonites using various elemental signatures, but the information garnered from this can be misleading since 1) volcanoes produce highly variable compositions during single events, making tephra classifications reliant on the position within the bed and the distance from the source, and 2) the elemental concentrations may vary significantly due to devitrification. Strontium and neodymium isotopic signatures offer a powerful dataset to supplement these efforts, but the extent to which the isotopic ratio is preserved during devitrification and post-depositional diagenesis is not well documented. Here we perform a detailed isotopic, geochemical, and mineralogical examination of sixteen bentonites preserved in Cenomanian and Campanian strata (Late Cretaceous) from South Dakota in order to characterize the diagenetic factors that may influence the ash geochemistry, while checking for the fidelity of the isotopic signatures to the magmatic source. A mixing model between the isotopic composition of bentonite and seawater can be generated to determine the original endmember composition of each deposit, since Sr was likely derived from both sources

The Upper Cretaceous-lower Paleogene formations in the Aix-en-Provence basin are characterized by interfingering lacustrine carbonates and flood-plain alluvium. The deposits from both environments display numerous horizons of carbonate-rich paleosols. By using a combined magnetostratigraphy and carbon isotope stratigraphy for the pedogenic carbonate glaebules, we constructed a detailed integrated stratigraphy for the entire lower Paleogene. This method provides a way to correlate marine and terrestrial sequences when C3 plants dominated the environment. Both long-term and short-term δ 13 C variations were identified in the Provence series: (1) the uniform carbon isotope record established through the end of the Maastrichtian followed by the abruptly negative carbon isotope excursion in the lowermost Paleocene provides a marker for the precise location of the Cretaceous-Tertiary boundary in this basin, 5 m below the Calcaire de Vitrolles Formation; (2) a gradual δ 13 C increase through the middle upper Paleocene similar in amplitude to that of the marine realm; (3) a short-term negative δ 13 C excursion in the latest Paleocene, as seen within the Calcaire de St. Marc Formation; and (4) a slow decrease during the late Paleocene to early Eocene, with a probable hiatus in the sedimentary record. The Provence mammal site of Palette is shown to be stratigraphically younger than the late Paleocene negative δ 13 C excursion.

The famous vertebrate-bearing fissures of the Bristol area in southwest England and in south Wales were traditionally referred to “upland” environmental settings, and assigned an overall time range of some 60 Myr; we reject both of these viewpoints. In terms of the environmental setting, based upon the evidence of palaeogeography, sediments, and fossils, we show that all the Triassic-aged fissures were near-coastal and embedded in karst formed on palaeo-islands in a subtropical archipelago. Further, the dates of these fissure fills in both regions do not span the Carnian to Rhaetian, as commonly supposed, but instead they are probably all Rhaetian. We update information on the Charles Moore Holwell “Microlestes” fissure assemblage and demonstrate that the marine fauna confirms a Rhaetian age. As proposed by previous authors, younger fissure fills around the St. Brides area of South Wales were also formed on an island, but during the Hettangian–Sinemurian. The youngest fissure deposi...

Elongated lenses of palustrine limestone interbedded with Mio-Pleistocene fluvial sands were exposed within a sand quarry in the north of Kuwait. Detailed field investigations, thorough petrographic and nanoscopic examinations and geochemical analysis revealed that they were originally precipitated as carbonate microbialite in isolated freshwater ponds scattered within a fluvial floodplain. These lacustrine microbialites were subjected to intermittent drying and wetting conditions and eventually altered to pseudobrecciated nodular palustrine limestone through several pedogenic and early diagenetic processes. The pedogenesis is exhibited by cracking, nodulization, mottling, pseudomicrokarst and root traces. The desiccation macrocracks are filled with siliciclastic sands derived from short-lived flash floods. Diagenesis is represented by aggradational neomorphism of micrite, cementation of cracks and voids by sparry calcite and precipitation of biogenic needle-fibre calcite. Concurrently, the cracks filled with siliciclastic sands have been calcretized, forming an embedded interapalustrine calcrete. Mottling postdates the early diagenesis and is manifested by pseudoclotted texture and abundant black spots and dendrites, which may have been developed by the marmorization of iron and manganese ions due to the seasonal fluctuation of groundwater. The δ 13 C and δ 18 O values are mostly comparable with those of closed freshwater lakes; however, the high negative values of δ 18 O may be attributed to diagenetic calcite. The occurrence of this palustrine limestone within a fluvial siliciclastic sequence that lacks clearly developed calcrete profiles may present an exceptional setting for palustrine limestone.

The Po Plain (Italy) is one of the most densely populated and productive regions of Europe, characterized by a flourishing economy (also linked to strategic subsurface resources) and several world cultural and natural heritage sites. The coupling of social-economic interests with geological hazards (i.e., seismic, subsidence and flooding hazards) in this area requires accurate knowledge of the subsurface geology, active geological processes, and impact of human activities on natural environments to mitigate the potential natural and anthropic risks. Most data unveiling the subsurface geology of this region were produced by the hydrocarbon exploration industry. Po Plain hosts indeed many hydrocarbon fields that were discovered since the early 1950s giving rise to the subsurface exploration through extensive seismic reflection surveys and drilling of numerous deep wells. In this work, geological-geophysical data from 160 deep wells drilled for hydrocarbon exploration/exploitation purposes in the Po Plain and in the facing northern Adriatic Sea have been collected and digitized along with several published geological cross-sections and maps. These data have been used to reconstruct the overall subsurface 3D architecture and to extract the physical properties of the subsurface geological units. The digitized data are suitable to be imported into geo-software environments so to derive the geophysical-mechanical properties of the geological units for a wealth of applied and scientific studies such as geomechanical, geophysical and seismological studies. The integrated dataset may represent a useful tool in defining strategies to ensure the safety of the urbanized areas and human activities and to reduce natural and anthropic risks that may affect this crucial region of Europe. Nowadays, such issues are particularly relevant for the underground industry development related to the increasing interest on possible CO 2 and hydrogen underground storage, which can play a fundamental role in the energy transition process towards the decarbonisation goals.

Red, purple and gray-green mudrocks near Dillon, Montana, have been mapped traditionally as the Upper Jurassic Morrison Formation. There are very few studies of the Mesozoic strata in this area and questions exist as to whether this unit actually is the Morrison Formation, or whether it is similarly variegated mudrocks of other formations at nearly the same stratigraphic interval. This study compares the stratigraphy, sedimentology, and paleontology of rocks near Dillon to the Upper Jurassic Morrison Formation elsewhere in the northern portion of the Western Interior Basin. The average thickness of the unit in question is approximately 24 m. It is composed of four lithofacies: 1) interbedded gray-green sandy siltstone showing weak pedogenic modification; 2) red calcareous mudstone on which moderately-to well-developed paleosols formed; 3) intraformational mudclast conglomerates; and 4) black claystone. These lithofacies are interpreted as distal floodplain deposits of a mud-dominated alluvial system. The paleosols are characterized by mottled coloration, carbonate nodules, clay slickensides, and abundant carbonate rhizoliths and rhizocretions. Dinosaur-bone fragments and the Late Jurassic gastropod Viviparus reesidei were also present. The stratigraphy, sedimentology and paleontology compare best with the Morrison Formation of northern Wyoming and south-central Montana.

This study combines lithofacies, palaeosols, and ichnocoenoses of the Upper Triassic Chinle Formation (Fm) into ichnopedofacies to interpret palaeoenvironmental conditions and palaeoclimatic changes in the northeast Chinle Basin. These interpretations, in turn, will enable more detailed reconstructions of the variability in sedimentation rate, tectonics, and climate across the basin, building a more accurate regional picture of the Chinle Fm through the Late Triassic. This is the first study to systematically integrate ichnological and pedogenic features in the Chinle Fm to determine local controls on base level, sediment deposition, pedogenesis, groundwater profile, and environments. Palaeosols record the relative influence of soil-forming factors-climate, organisms, topography, parent material, and time (Jenny, 1941)-that modified sediments deposited on ancient landscapes (e.g.

Extensive soft-sediment deformation (SSD) of multiple expressions and scales record active and dynamic events and processes in erg deposits of the Lower Jurassic Navajo Sandstone near Moab, Utah. The erg deposits preserve depositional environments of eolian dune, interdune, fluvial, playa, lake, and spring. A large range of SSD features, from intact beds showing little deformation to pervasively disturbed beds, exist in many of these deposits. A simplified classification index captures the different scales of SSD in ascending order of deformation intensity: 1) mostly intact bedding with small-scale wavy or undulatory deformation structures within single beds; 2) dish and flame structures; 3) meter-scale, kinked, slumped, rolled, overturned, vertical, and detached contorted crossbedding, and associated centimeter-to meter-scale pipes; and 4) disruptive diapirs and laterally extensive massive sandstone. The SSD features of deformed crossbed sets, diapirs, and massive sandstone beds, are consistently juxtaposed, and are thus genetically linked. Although the Navajo Sandstone has been considered a classic example of an extensive dry eolian system, both individual and combinations of strata bounded SSD features exemplify dynamic deformation, liquefaction, and fluidization that took place at various times after deposition. The lowest degree of deformation, SSD 1, is largely attributed to autogenic-inherent to the eolian system-or local allogenic processes. Larger degrees of deformation, SSD 2-4, were more likely produced by allogenic, external-forcing processes from regional changes in climate and/or near-surface groundwater conditions originating from the Uncompahgre uplift, with the deformation triggered by some event(s). Possible significant ground motion could have led to large-scale disruption in the Navajo sand sea across kilometer-scale intervals. The Navajo example establishes valuable hierarchical relationships of processes and products for recognizing and interpreting SSD in other ancient and modern eolian systems. This has particular relevance to sedimentary discoveries on Mars, where SSD features are visible from remote sensing imagery and rover exploration.

Twelve samples of Jurassic Twin Creek Limestone from seven localities in the Idaho-Wyoming thrust belt region were found to be extremely low in organic matter content, even though the darkest colored and least weathered samples were selected for analysis. We believe that very little organic matter was deposited and preserved in the Twin Creek Limestone in this region. Moreover, rocks of pre-Cretaceous age were subjected to high temperatures unfavorable for preservation of liquid hydrocarbons in localized areas, especially near the point where the borders of Utah, Idaho, and Wyoming join. These interpretations suggest that oil produced from the Twin Creek Limestone and underlying Nugget Sandstone in this region was generated in source rocks of Cretaceous age buried beneath thrust sheets. This oil would have been emplaced in structural traps also associated with thrust movement, after rocks of Jurassic and Triassic age were uplifted, and at temperatures more favorable for the presence of liquid hydrocarbons.

A model is proposed for the development of the Quaternary palustrine carbonate-calcrete association, which occurs as hard crust capping low hills at a distal flood plain of Al Dibdibba alluvial fan located at southwestern Kuwait. Field occurrence, detailed petrographic investigation and geochemical analysis revealed that a single cycle of groundwater calcrete with vertical gradational maturity pattern was developed. This represents a continuous sedimentological cycle during which flood sheet conditions prevailed with intermittent periods of humid and arid conditions. Subsequently, calcitic micrite was continuously precipitated from small, shallow, local, isolated and short lived ponds fringed by freshwater marshes with abundant charophyte meadows. The latter were developed as a result of flooding scattered depressions by groundwater supersaturated with respect to calcite due to rise of groundwater table. The deposition of two facies of carbonate muds, namely; biomicrite and pelintraclasts skeletal micrites was followed by a drought phase which witnessed desiccation of the fresh water ponds and significant drop in groundwater level. A sequence of pedogenic and diagenetic processes acted on the deposited carbonate muds are manifested by: (a) desiccation cracks, (b) micrite neomorphism, (c) infilling of root burrows and some cracks by aeolian siliciclastics, (d) karstification, (e) marmorization, (f) calcretization of root burrow infill and development of pseudo-rhizocrete, (g) calcite cementation and mineral authigenesis, and (h) silcretization. These processes are responsible for the development of hard palustrine carbonate crust. At the advent of aridity, the whole system of Al Dibdibba alluvial fan was subjected to deflation. This resulted in reversing the paleotopography of the hard crusted palustrine depressions into carbonate capped domal hills.

We present a 1:7500 scale geological map of part of the footwall of the south verging Belluno Thrust of the seismically active eastern Southern Alps of northern Italy. We report a previously unknown thrust zone, the "San Donato-Costa Thrust Zone", that cuts across the local Meso-Cenozoic stratigraphic succession. 1:2500 and 1:5000 geological mapping, in combination with the revision and improvement of the local lithostratigraphy and detailed structural analysis, provided new insights into the thrust geometry and the setting of the greater area it deforms. We show that the recorded deformation style (e.g. folding vs. faulting) exhibits notable variations within the affected Meso-Cenozoic stratigraphic succession, with shortening accommodated by fold trains and several subparallel thrust splays with variable amounts of stratigraphic offset cumulated during repeated faulting. Our results contribute to a better definition of folding and faulting within the Mesozoic carbonate multilayer system of the eastern Southern Alps.

Field relations, petrography, GIS, and geochemistry of a Late Miocene-Pliocene limestone, the Opache Formation, Calama Basin, Atacama Desert, Chile shows that depositional facies, diagenetic histories, and isotopes differ from eastern to western parts of the basin. We recognize two facies; lacustrine, characterized by ostracoddiatom mudstone and wackestone, and palustrine, characterized by both shallow water and pedogenic features. GIS analysis of the Basin topography reveals an intrabasinal low in the eastern area and steeper hydrological gradients to the west, with the "Calama constriction", restricting flow between east and west. Petrography and geochemical results confirm that the Calama constriction influenced depositional parameters, ponding groundwater to the east, forming a shallow lake and creating palustrine conditions to the west. Our analyses indicate that lake waters were less enriched in 13 C or 18 O than palustrine waters even though

This study defines the neostratotype of the Lower-Middle Albian Itapecuru Formation in the Parnaíba Basin, Northeast Brazil. In this sedimentary succession along the right bank of the Itapecuru river near the Itapecuru-Mirim City, Maranhão State, three lithofacies associations are recognized. the first is silty claystone with some very fine sand, micaceous, reddish color, thin laminated, showing a tabular aspect, interpreted as floodplain fines in a distal position. The second is clayey siltstone, reddish color, with ripple cross-lamination, very thin cross-laminated wacke lenses, grading to thin parallel lamination, in apparently tabular layers, interpreted as crevasse splay and distributive channels deposits in successive avulsion events. The third is fine quartz wacke, reddish to grayish color, showing grouped trough cross bedding, interpreted as channel filling deposits. These facies associations correspond to part of a fluvial depositional system, with predominantly fine-grained rocks, and small lakes in the floodplain, in an oxidizing environment and marked by seasonality. These field data, reinforced by grain size and petrographic analyses showed that, contrary to previous descriptions, the Itapecuru Formation consists mainly of mudrocks. this research also shows that the medium to coarse sandstones and conglomerates, previously included in the Itapecuru Formation, belong to the underlying Grajaú Formation.

The magnetic parameters of sedimentary rocks can record accurately tectonic and climatic influences upon sedimentary processes, when they are not altered during diagenesis. This paper is focused on the possible alteration of the primary magnetic-susceptibility signal during early diagenesis of marine organic matter (OM). In the late Kimmeridgian-Tithonian Argiles de Châtillon Formation (Fm.) of the Boulonnais area (northern France – lateral time equivalent of the distal organic-rich sediments of the Kimmeridge Clay Fm. of Dorset), the organic content is dominated by amorphous OM (AOM), either brown or orange, originating from selective preservation or sulphurisation, respectively. Total sulphur content correlates well with orange + brown AOM abundance, and organic S content correlates well with orange AOM abundance. The magnetic signal of these claystones and paper shales is dominantly carried by clay minerals. The magnetic susceptibility vs. brown-AOM abundance relationship shows ...

This study defines the neostratotype of the Lower-Middle Albian Itapecuru Formation in the Parnaíba Basin, Northeast Brazil. In this sedimentary succession along the right bank of the Itapecuru river near the Itapecuru-Mirim City, Maranhão State, three lithofacies associations are recognized. the first is silty claystone with some very fine sand, micaceous, reddish color, thin laminated, showing a tabular aspect, interpreted as floodplain fines in a distal position. The second is clayey siltstone, reddish color, with ripple cross-lamination, very thin cross-laminated wacke lenses, grading to thin parallel lamination, in apparently tabular layers, interpreted as crevasse splay and distributive channels deposits in successive avulsion events. The third is fine quartz wacke, reddish to grayish color, showing grouped trough cross bedding, interpreted as channel filling deposits. These facies associations correspond to part of a fluvial depositional system, with predominantly fine-grained rocks, and small lakes in the floodplain, in an oxidizing environment and marked by seasonality. These field data, reinforced by grain size and petrographic analyses showed that, contrary to previous descriptions, the Itapecuru Formation consists mainly of mudrocks. this research also shows that the medium to coarse sandstones and conglomerates, previously included in the Itapecuru Formation, belong to the underlying Grajaú Formation.

The famous vertebrate-bearing fissures of the Bristol area in southwest England and in south Wales were traditionally referred to “upland” environmental settings, and assigned an overall time range of some 60 Myr; we reject both of these viewpoints. In terms of the environmental setting, based upon the evidence of palaeogeography, sediments, and fossils, we show that all the Triassic-aged fissures were near-coastal and embedded in karst formed on palaeo-islands in a subtropical archipelago. Further, the dates of these fissure fills in both regions do not span the Carnian to Rhaetian, as commonly supposed, but instead they are probably all Rhaetian. We update information on the Charles Moore Holwell “Microlestes” fissure assemblage and demonstrate that the marine fauna confirms a Rhaetian age. As proposed by previous authors, younger fissure fills around the St. Brides area of South Wales were also formed on an island, but during the Hettangian–Sinemurian. The youngest fissure deposi...

A detailed study of the mineral composition and microstructure of the black shales associated with OAE1a (Eastern Russian Platform), OAE1b (Middle Caspian), and the host rocks has been carried out using X-ray diffraction, scanning electron microscopic, and microprobe analyses. The results provide important constraints for depositional environments in the sedimentary basins. Black shales with pyrite framboids imply euxinic (sulfidic) conditions with increased organic matter preservation. Disintegrating framboids suggest partial or complete dissolution of the organic matter inside the framboids due to increasing water oxygenation. OAE1a on the Eastern Russian Platform is heterogeneous as it includes thin interbeds of concretionary coccolith limestones within the interval of bituminous shales, and correlates with the Lower Aptian Rhagodiscus angustus nannofossil zone. The coccolith limestones indicate short intermittent episodes of interrupted stagnation, rapid oxygenation, and restoration of normal marine conditions. The presence of montmorillonite, albite, microcline, and diopside in the bituminous siltstones and in the host siltstones of OAE1a on the Eastern Russian Platform, as well as a high content of titanium in the black siltstones correlated with OAE1b in the Middle Caspian allow proposing significant input of pyroclastic material into the extant sea.

• The pre OAE 2 Mo-isotope composition of seawater constrained to 1.1%-1.9% • Limited change in seawater Mo isotopes during OAE 2 linked to enhanced global Mo burial with Fe minerals • The response of other redoxsensitive isotopic systems to major ocean redox changes may be affected by global changes in Fe cycling

Molybdenum (Mo)-isotope chemostratigraphy of organic-rich mudrocks has been a valuable tool for testing the hypothesis that the Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic,~183 Ma) was characterized by the spread of marine euxinia (and organic matter burial) at a global scale. However, the interpretation of existing Mo-isotope data for the T-OAE (from Yorkshire, Cleveland Basin, U.K.) is equivocal. In this study, three new Mo-isotope profiles are presented: from Dotternhausen Quarry (South German Basin, Germany), the Rijswijk core (West Netherlands Basin, Netherlands), and the Dogna core (Belluno Basin, northern Italy). Precise biostratigraphic and chemostratigraphic correlation between the three sites allows a direct comparison of the data, enabling some key conclusions to be reached: (i) The Mo-isotope composition of seawater during the peak of the T-OAE was probably close to~1.45‰, implicating a greater removal flux of sulphides from seawater, and a larger extent of global seafloor euxinia compared to the present day; (ii) Mo-isotope cycles previously identified in the Yorkshire sedimentary succession are attributed to changes in the degree of local Mo drawdown from overlying Cleveland Basin seawater; (iii) The consistency of the new multisite Mo-isotope data set indicates a secular reduction in the burial of Mo globally in the late stages of the T-OAE, implying a contraction in the extent of global marine euxinia; (iv) Subtle differences in the Mo-isotope composition of deposits formed in different euxinic subbasins of the European epicontinental shelf were probably governed by local variations in basin hydrography and rates of water renewal. 2007]. This negative carbon-isotope excursion likely records the injection of isotopically light carbon into the oceans and atmosphere, either from the dissociation of methane hydrates [e.g., Hesselbo et al., 2000], magmatic intrusions into organic-rich sediments [McElwain et al., 2005], and/or volcanic activity associated with the Karoo-Ferrar large igneous province [Pálfy and Smith, 2000; Svensen et al., 2007; Percival et al., 2015]. Overall, the significance of the T-OAE is manifested in a carbon-cycle perturbation that reflects changes in climate and biogeochemical cycling at a global scale [Jenkyns, 2010]. In terms of north European ammonite stratigraphy, the negative carbon-isotope event can be considered to have lasted from the late tenuicostatum Zone to the mid-falciferum (or serpentinum) Zone. The isotopic composition of the trace metal molybdenum (Mo), which was previously measured in mudrock samples from the Jet Rock in Yorkshire, England (Cleveland Basin

The Congo basin, located in the Democratic Republic of Congo, is the largest sedimentary basin of Africa. Mesozoic sediments of this intra-cratonic basin outcrop along its eastern edge, south of Kisangani (former Stanleyville). The Stanleyville formation (dated Upper Jurassic) was described in the last century as a lacustrine series resting on a basal thin marine limestone, the Limefine . Since this early model was proposed, the depositional environment of the Stanleyville formation and in particular the possible marine incursion has been strongly debated, but without revising the existing core and outcrop samples for the type location near Kisangani that are available at the Royal Museum for Central Africa (MRAC/KMMA, Tervuren, Belgium). In order to refine the former sedimentary descriptions, a series of 9 mining cores drilled in the Kisangani region have been selected for this purpose. The cores were made available during a project with the MRAC/KMMA. This study focuses on sedimen...

The Department of Conservation makes no warranties as to the suitability of this product for any particular purpose. In 1990 the U.S. Geological Survey, as part of the National Geologic Mapping Program, initiated the Southern California Areal Mapping Project (SCAMP) (http:// scamp.wr.usgs.gov) in cooperation with the California Geological Survey (then Division of Mines and Geology) Regional Geologic Mapping Project (http://www.conservation. ca.gov/cgs/rghm/rgm/index.htm). SCAMP's objectives were twofold: to provide a basic understanding of the geologic framework and geologic history of southern California; and to develop a uniform digital geologic map database that could be used in a Geographic Information System (GIS) and be the foundation for geologic hazard investigations, natural resource evaluations, and other related earth science studies. These types of digital data can provide an important component for performing GIS analyses throughout southern California.

Bentonites serve as an important stratigraphic tool for facies correlation due to their instantaneous deposition and preservation across multiple depositional environments. Correlating one bed to another can be a complex issue limited by the 3-dimensional availability of outcrops and core. This process is reliant on the assumption that the geochemical signatures of ash beds do not vary enough to statistically alter the correlation coefficients that tie one ash-fall to another. This assumption may be faulty, however, and the problem compounds as bentonite bed thickness increases because the chemical composition varies through an eruption due to stratification of the magma chamber and through physical transport. Linear discriminant analysis (LDA) can significantly aid with this issue, allowing for the utilization of a multivariate dataset to statistically separate chemically-similar groups. Here we present a statistical approach to assessing the primary discriminatory variables on a suite of 87 Cretaceous bentonites deposited in the Bighorn Basin, Wyoming, USA, that span five geologic stages and seven formations, from the Cloverly Formation (110 Ma) to the Meeteetse Formation (70 Ma), and includes nine named ash beds. Using LDA, bentonites were sorted into groups based on geologic stage, formation, and unique beds using key elemental concentrations and radiogenic isotopes (e.g., 87 Sr/ 86 Sr, TiO 2 , Sc, Na, and Th). Additionally, distinct similarities in the discrimination pattern between formations reveal two periods of magmatism, the development of the Idaho batholith and the migration and development of the Boulder batholith and surrounding related plutons. With well-preserved, temporally-constrained ash, LDA can correlate ancient tephra deposits while also shedding light on the cyclical nature of geochemical trends in a migrating subduction zone.

Patterns of uranium-molybdenum covariation in marine sediments have the potential to provide insights regarding depositional conditions and processes in paleoceanographic systems. Specifically, such patterns can be used to assess bottom water redox conditions, the operation of metal-oxyhydroxide particulate shuttles in the water column, and the degree of water mass restriction. The utility of this paleoenvironmental proxy is due to the differential geochemical behavior of U and Mo: (1) uptake of authigenic U by marine sediments begins at the Fe(II)-Fe(III) redox boundary (i.e., suboxic conditions), whereas authigenic Mo enrichment requires the presence of H 2 S (i.e., euxinic conditions), and (2) transfer of aqueous Mo to the sediment may be enhanced through particulate shuttles, whereas aqueous U is unaffected by this process. In the present study, we examine U-Mo covariation in organic-rich sediments deposited mostly in the western Tethyan region during oceanic anoxic events (OAEs) of Early Jurassic to Late Cretaceous age. Our analysis generally confirms existing interpretations of redox conditions in these formations but provides significant new insights regarding water mass restriction and the operation of particulate shuttles in depositional systems. These insights will help to address contentious issues pertaining to the character and origin of Mesozoic OAEs, such as the degree to which regional paleoceanographic factors controlled the development of the OAEs.

The tectono-stratigraphic evolution of foreland basins is influenced by processes acting on local, regional and global scale. In this paper the effects of these processes on the basin evolution are investigated using a forward reconstruction model based on the principles of balanced cross-section. The modelling incorporates the consequences of thrust deformation, sedimentation, erosion, basement subsidence, and sealevel changes on the basin stratigraphy. Basement subsidence due to lithospheric loading is the main cause of foreland basin formation, but appears to have minor implications for the occurrence of angular unconformities in the stratigraphic record of piggyback basins. Thrusting is probably the dominant factor in the control of the stratigraphic evolution of piggyback basins, overprinting the effect of eustasy. Detailed analyses of stratigraphic data enable the reconstruction of the structural evolution of the underlying thrust system. ModelIing of the Northern Apenninic PO basin shows that Neogene stratigraphic sequences of the proximal part of the basin can be explained by tectonic activity of the Apenninic fold and thrust belt. Strong basement subsidence accompanied with deep-seated mid-Pliocene thrusting controls the stratigraphic record of the PO piggyback basins.

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In the Caborca–Altar area of northwest Sonora, variably deformed and metamorphosed sedimentary and volcanic rocks crop out in a northwest-southeast–trending belt (El Batamote belt) at least 70 km long. We obtained detrital zircon U-Pb ages from two distinctive components of the belt near Altar, here termed the Altar complex and Carnero complex. Zircon ages for metasandstone and metaconglomerate matrix from the Altar complex indicate a Late Cretaceous maximum age of sedimentation, with at least part of the complex no older than 77.5 ± 2.5 (2σ). Pre-Cretaceous detrital zircons in the complex were derived largely from local sources, including Proterozoic basement, the Neoproterozoic–Cambrian miogeocline and the Jurassic arc. The detrital zircon ages and lithologic character of the Altar complex suggest correlation with the Escalante Formation, the uppermost unit of the Upper Cretaceous El Chanate Group. In contrast, one sample from the Carnero complex yielded a Middle Jurassic maximum ...

This paper considers the development and evolution of pedogenic structures within palustrine facies and their relationship with those of calcretes as exemplified by the Bembridge Limestone (BL) Formation (Upper Eocene) of the Isle of Wight. Within this formation, primary lacustrine facies (mainly biomicrites) have been modified by pedogenesis to varying degrees. Whilst such changes developed as part of an evolving continuum, three structures are recognised to represent evolving stages in this process: brecciated-nodular, clotted-peloidal and peloidal-ooidal structures. A fourth structure, laminar, is sometimes intercalated with the other three and in places is seen to replace them. They are particularly developed in the western outcrops of the formation which represent the palustrine fringes of the main lacustrine bodies. The structures are thought to represent the progressive differentiation of the peloidal and ooidal elements from the original lacustrine sediment and appear to be a response to alternations of wetting and drying of the soil under fluctuating climatic conditions. The vermiform fabric of the laminar structure is attributed to calcified root mats. The general depletion in the heavy O and C isotopes of palustrine facies with respect to the original lacustrine ones is interpreted as being the result of repeated dissolution-reprecipitation processes occurring during soil development. The palustrine facies of the BL correlates well with an intermediate condition between semi-arid and subhumid climates with extensive biological soil modification of freshwater carbonates.

The carbonate lake system represented by the late Eocene Bembridge Limestone Formation (Isle of Wight, southern England) comprises two main facies: lacustrine and palustrine. These facies are arranged vertically in transgressive/regressive cycles, corresponding to a model of carbonate lakes of low gradient and fluctuating margins with extensive palustrine fringes. These lakes developed in a coastal plain of limited relief, where two paleogeographical domains predominate. A lacustrine domain is represented in northern and eastern sections in the Isle of Wight by cycles representing upward passage from central lacustrine sub-facies (marl/marly limestone) through marginal lacustrine sub-facies (biomicrite) to sub-facies indicative of exposure (brecciated-nodular limestone). A palustrine domain, predominant in west Wight, is represented by a predominantly pedogenic palustrine facies with clottedpeloidal to ooidal textures and some intercalated laminated (laminar calcrete) horizons. Within the pedogenic facies, textures have evolved from those of unaltered biomicrites through clotted-peloidal to dense ooidal to open ooidal textures. A third domain, developed in close geographical proximity to more saline waters, is represented by gypsiferous lake-margin facies found in north Wight in which microlenticular gypsum developed post-depositionally as a result of evaporation following subaerial sediment exposure. In the lacustrine domain, there appears to be an association between cyclicity and changes in base (sea) level reflecting a likelihood that the lakes were part of a paralic, coastal plain complex with distal marine connections. Alternatively, the cyclicity might have developed as a result of the alternation of wetter and drier climatic periods.