Jurassic Stratigraphy Research Papers - Academia.edu (original) (raw)

The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The... more

The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The discovery of several well-preserved, relatively intact, fossil logs at several locations in Rainbow Draw and one location in Miners Draw, both near Dinosaur National Monument (Utah), has provided an opportunity to study the local paleobotany, stratigraphy, and sedimentology of the Morrison Formation in northeastern Utah. The Morrison Formation in northeastern Utah consists of four members. In ascending chronostratigraphic order, they are the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The lithology (including the presenceof glauconite grains) and fossil assemblage of the lower two members (Windy Hill and Tidwell) indicate a marine to marginal marine (coastal plain) depositional environment, whereas the lithology, fossil flora and faunaassem...

Belemnites (order Belemnitida), a very successful group of Mesozoic cephalopods, provide an important clue for understanding Mesozoic marine ecosystems and the origin of modern cephalopods. Following current hypotheses, belemnites... more

Belemnites (order Belemnitida), a very successful group of
Mesozoic cephalopods, provide an important clue for understanding Mesozoic marine ecosystems and the origin of modern cephalopods. Following current hypotheses, belemnites originated in the earliest Jurassic (Hettangian, 201.6–197 Ma) with very small forms. Accord- ing to this view their paleobiogeographic distribution was restricted to northern Europe until the Pliensbachian (190–183 Ma). The fossil record is, however, biased by the fact that all the previous studies on belemnites focused on Europe. Here we report two belemnite taxa from the Hettangian of Japan: a new species of the Sinobelemnitidae and a large taxon of the suborder Belemnitina. The Sinobelemnitidae, which may be included in the future in a new suborder, have also been recorded from the Triassic of China, specimens so far poorly under- stood. The presence of a very large rostrum attributed to the Belemni- tina suggests in addition that a diverse belemnite fauna evolved earlier than previously thought. Our new findings therefore (1) extend the origin of the belemnites back by ~33 m.y. into the Triassic, (2) suggest that this group did not necessarily originate in northern Europe, and (3) imply that belemnites survived the Triassic–Jurassic extinction, one of the five big mass extinctions in the Phanerozoic. Since belem- nites provided a considerable amount of food as prey, the origination of belemnites is probably an important event also for the evolution of their predators, such as marine reptiles and sharks.

The Callovian to Ryazanian (late Middle Jurassic to earliest Cretaceous; here referred to as 'Late Jurassic' sediments of the Dutch Central North Sea Graben, comprising the Central Grabeli and Scruff Groups, form several potential... more

The Callovian to Ryazanian (late Middle Jurassic to earliest Cretaceous; here referred to as 'Late Jurassic' sediments of the Dutch Central North Sea Graben, comprising the Central Grabeli and Scruff Groups, form several potential reservoirs. Source rocks are present within both these groups and the Carboniferous and Late Triassic-Early Juras-sic. The structural development of the area is illustrated by a number of cross-sections. A structural subdivision has been made into platform, intermediate platform, outer graben, and inner graben. The complex history of rifting, wrench-faulting, halokinesis, and structural inversion strongly influenced the palaeogeography and ensuing sandstone developments. A few selected burial-history plots are presented as examples of the relationship between the structural subdivision and the hydrocarbon potential of the area.

Strata of the Bardas Blancas Formation (lower Toarcian–lower Bajocian) are exposed in northern Neuquén Basin. Five sections have been studied in this work. Shoreface/delta front to offshore deposits predominate in four of the sections... more

Strata of the Bardas Blancas Formation (lower Toarcian–lower Bajocian) are exposed in northern Neuquén Basin. Five sections have been studied in this work. Shoreface/delta front to offshore deposits predominate in four of the sections studied exhibiting a high abundance of hummocky cross-stratified, horizontally bedded and massive sandstones, as well as massive and laminated mudstones. Shell beds and trace fossils of the mixed Skolithos-Cruziana ichnofacies appear in sandstone beds, being related with storm event deposition. Gravel deposits are frequent in only one of these sections, with planar cross-stratified, normal graded and massive orthoconglomerates characterizing fan deltas interstratified with shoreface facies. A fifth outcrop exhibiting planar cross-stratified orthoconglomerates, pebbly sandstones with low-angle stratification and laminated mudstones have been interpreted as fluvial channel deposits and overbank facies. The analysis of the vertical distribution of facies and the recognition of stratigraphic surfaces in two sections in Río Potimalal area let recognized four transgressive–regressive sequences. Forced regressive events are recognized in the regressive intervals. Comparison of vertical distribution of facies also shows differences in thickness in the lower interval among the sections studied. This would be related to variations in accommodation space by previous half-graben structures. The succession shows a retrogradational arrangement of facies related with a widespread transgressive period. Lateral variation of facies let recognize the deepening of the basin through the southwest.

Today in the course of active updating and development (on the basis of the GSSP and GSSA concept) International Chronostratigraphic Chart in general and, the Mesozoic in a particular, among the most relevant and sharp stratigraphy... more

Today in the course of active updating and
development (on the basis of the GSSP and
GSSA concept) International Chronostratigraphic Chart in general and, the Mesozoic in
a particular, among the most relevant and
sharp stratigraphy problems still there is
a level division of a Cretaceous system
(GTS–2012) and J/K boundary in particular.
For almost 200 years, an attempt to solve this
problem has been raised by researchers at
the regional and global levels, discussed at
numerous symposiums, colloquiums, meetings, conferences and covered in a number
of publications by several generations of
stratigraphs around the world. In the last
three decades Subcommission on Cretaceous
Stratigraphy (SCS) with the Working Groups
that make important decisions on global
questions of level division, carrying out
boundaries between systems, series, stages
and making GSSP. It was not succeeded to
solve this problem at the regional and global
level yet (Hoedemaeker 1987; Grabowski
2011; Schnabl et al. 2015; Wimbledon et al.
2017). But it is nearing completion (Wimbledon 2017). At the present stage more than
300 section are studied worldwide, more than
3500 taxons and the marking layers are established, but making decision on the choice of
GSSP for unratified stages of the Jurassic and
Cretaceous systems remains the Working
Groups relevant (Granier et al. 2019). Considering emergence of new actual material
and new researches techniques the problem
remains unresolved. It is as follows. Despite
almost 200-year history of studying of a Сretaceous system, stages of lower department
and partially top (except for Cenomanian,
Turonian, Santonian and Maastrichtian) have
the status of unratified. It concerns also
stages of the Upper Jurassic (Oxfordian,
Tithonian). Boundaries Lower Cretaceous
and partially the Upper Cretaceous of stages
have no approved stratotype. Stages and substages of Cretaceous systems as the main
subdivisions of International Chronostratigraphic Chart have the status of unratified.
There is debatable a boundary problem between Jurassic and Cretaceous systems and
also the provision of a Berriassian stage in
International Chronostratigraphic Chart
(System boundary has to correspond to
boundary of the lower stage).

A single rostrum of Cylindroteuthis (Cylindroteuthis) cf. theofilaktovi Nikitin recovered from the Late Bathonian－Early Callovian Kaizara Formation of the Tetori Group in Shimoyama, Kuzuryu area, Central Japan, is described for the first... more

A single rostrum of Cylindroteuthis (Cylindroteuthis) cf. theofilaktovi Nikitin recovered from the Late Bathonian－Early Callovian Kaizara Formation of the Tetori Group in Shimoyama, Kuzuryu area, Central Japan, is described for the first time in East Asia. This belemnite species has been previously known only from the Early Callovian of Central Ukraine in Eastern Europe. Since the family Cylindroteuthididae has been considered as the typical Boreal or northern element in the Jurassic belemnite paleobiogeographic studies, its occurrence in the Inner Zone (Japan Seaside) of Southwest Japan clearly indicates that Cylindroteuthis expanded its distribution to the mid-latitudes of the Northwest Pacific at that time. This expansion possibly corresponds to the Early Callovian spread of boreal cylindroteuthids toward south into Europe in the Boreal-Atlantic seas. The occurrence of Cylindroteuthis from the Kaizara Formation strongly suggests that a cooler current possibly from the Arctic reached the Tetori Basin in the Late Bathonian－Early Callovian time.

A new locality in the Upper Jurassic Morrison Formation near Douglas, Wyoming, has yielded remains of a disarticulated sauropod skeleton (Supersaurus vivianae) and the remains of a semi-articulated small theropod. The sauropod is assigned... more

A new locality in the Upper Jurassic Morrison Formation near Douglas, Wyoming, has yielded remains of a disarticulated sauropod skeleton (Supersaurus vivianae) and the remains of a semi-articulated small theropod. The sauropod is assigned to the genus Supersaurus based on autapomorphic characters seen in the type specimen (BYU 9462) including: ventrally keeled caudal vertebrae with lateral pleurocoels; and elongated medially narrow cervicals with simple pleurocoels. Taphonomy of the site provides information on an unusual depositional environment, and the circumstances that lead to the preservation of the largest and smallest dinosaurs found in the state. The site is broken into two units separated by a weak soil horizon. The lower unit consists of fine grained to clay-sized matrix containing skeletal remains of the sauropod, and incorporates rip-up clasts from an underlying scoured layer. This unit exhibits no structure or sorting other than a slight mottling, interpreted to be root traces of a weakly developed paleosol. Abundant charcoalified plant remains are present, showing no preferred orientation. The unit is interpreted to be a high-energy deposition, comparable to a muddy debris flow. Immediately above the contact with the lower unit a small theropod skeleton was found. Sedimentology and micropaleontology of the upper unit indicate a shallow lake or pond environment that transgressed, covering the debris flow sediments. Micritic limestone layers form an alternating (up to 6 times) sequence of wetland/lacustrine mudstone and limestone. Stable oxygen and carbon isotope data were collected for each of the limestone layers and compared with pedogenic carbonate nodules located approximately 60 m lateral to the wetland/lacustrine limestone. Isotope values from the limestone layers show little variation, but are significantly enriched in 13C relative to pedogenic carbonates. It is suggested that a drought-induced wildfire destabilized elevated soils, perhaps on a remnant levee, initiating sediment flow considered to be consistent with modern wildfire-related debris flows. This quarry demonstrates a novel mode of deposition and is consistent with a seasonal semiarid environment for the Morrison Formation in east-central Wyoming.

ABSTRACT Paleosols in the Morrison Formation (Upper Jurassic) from the Western Interior and Colorado Plateau regions occur in fluvial/overbank and marginal-lacustrine depositional facies associated with aggradational settings, and at... more

ABSTRACT Paleosols in the Morrison Formation (Upper Jurassic) from the Western Interior and Colorado Plateau regions occur in fluvial/overbank and marginal-lacustrine depositional facies associated with aggradational settings, and at sequence-bounding unconformities that mark divisions between major aggradational and degradational successions. Pedogenic features within these horizons preserve important contextual information about the local and regional paleoclimate and paleoenvironment in which the soils formed. Floodplain and lake-margin paleosols show evidence that most of the Morrison basin was characterized by a semi-arid to tropical wet – dry paleoclimate with fluctuating groundwater conditions, a low precipitation to evaporation ratio, and weak to moderately seasonal precipitation. Paleosol ichnofauna show evidence of a diverse and opportunistic flora and fauna that exploited changing conditions and existing nutrient and moisture regimes. Changes in paleosol type and degree of development over the basin indicate the overall regional paleoclimate was drier in the western and southern portions of the basin. Vertical trends indicate paleoclimatic conditions over the basin became steadily more humid through time. Laterally continuous, well-developed, deeply weathered paleosols formed during times of little or no deposition and mark regional unconformities. The paleosols at these sequence-bounding unconformities serve as useful regional stratigraphic markers to trace genetic packages across the Morrison depositional basin and to determine regional accommodation trends.

The age of the basal sediments at Jara (Kachchh, Western India) has been a matter of debate due to the absence of time diagnostic fossils (notably of ammonites and nannofossils). Previous nannofossil records from these basal beds indicate... more

The age of the basal sediments at Jara (Kachchh, Western India) has been a matter of debate due to the absence of time diagnostic fossils (notably of ammonites and nannofossils). Previous nannofossil records from these basal beds indicate an Early Callovian age, whereas ammonite records (largely noted in passing), point to either a Latest Bathonian or an Earliest Callovian interval. Now, for the first time, from the core (basal marl and marlstone intercalations) of the Jara Dome, discovery of a typical Latest Bathonian Indonesian ammonite Macrocephalites cf. mantataranus Boehm [M] is recorded.
A similar find is now also documented from coeval Latest Bathonian strata (the Sponge beds) of the Jumara Dome, ~12 km east of Jara. Previous nannofossil
assemblage data from Jara is also critically reviewed with updated biochronology and it suggests that the nannofossils assemblage is not exclusively Early
Callovian age, as has been suggested but is of late Middle Callovian age (late part of the Middle Callovian Tethyan Gracilis Zone). Additionally, based
on morphological similarity, coeval stratigraphic distribution and statistical analyses, the present study reaffirms the close affinity of the Indonesian M. mantataranus Boehm [M] with the Kachchh Bathonian zonal index Macrocephalites triangularis Spath [M].

Carbonate mud that accumulated in the deep parts of a late Kimmeridgian carbonate ramp (Iberian Basin, NE Spain) was partly derived by resedimentation from shallow water production areas. High-frequency sea- level changes, probably driven... more

Carbonate mud that accumulated in the deep parts of a late Kimmeridgian carbonate ramp (Iberian Basin, NE Spain) was partly derived by resedimentation from shallow water production areas. High-frequency sea- level changes, probably driven by climatic changes in tune with precession and short-eccentricity cycles, affected carbonate production and the amount of exported sediment. Facies analysis and correlation of three outcrops located in middle and outer ramp settings allows a comparison of high-order sequences (bundles of beds and sets of bundles) across a ramp transect and an assessment of the carbonate factory. Analysis of the storm deposits found in middle ramp settings identifies deepening to shallowing high-frequency cycles based on the level of exported carbonate. In outer ramp areas, many of the bundles exhibit a thinning trend, indicating a progressive decrease of carbonate production and hence, carbonate export during periods of high- frequency sea-level rise. δ13Ccarb values show a gradual increase through the studied long-term transgressive interval ranging from 1.5‰ to 2.8‰. Within this long-term evolutionary trend, short-term δ13Ccarb fluctuations occur that correspond with some of the high-order cycles defined from sedimentary facies analysis. These short-term δ13Ccarb shifts are interpreted as shifts in carbonate export from shallow reef regions to the outer ramp. A consequence of this study is that variation in δ13Ccarb can be used for correlation in outer ramp successions, at least on a basin-wide scale.

A coastal exposure at Wine Haven, Robin Hood’s Bay (North Yorkshire, UK) fulfils the criteria for definition as the Global Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (Lower Jurassic). This marine sequence... more

A coastal exposure at Wine Haven, Robin Hood’s Bay (North Yorkshire, UK) fulfils the criteria for definition as the Global Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (Lower Jurassic). This marine sequence was deposited during a long-term transgression and is relatively expanded stratigraphically. A rich fauna of ammonites above and below the boundary interval allows recognition of the Leptechioceras gr. meigeini, Paltechioceras aureolum and Paltechioceras tardecrescens horizons of latest Sinemurian age, and the Bifericeras donovani, and Apoderoceras gr. aculeatum horizons of earliest Pliensbachian age. A suitable level for the boundary is characterized by the faunal association of Bifericeras donovani Dommergues & Meister and Apoderoceras sp. Strontium-isotope stratigraphy, based on analysis of belemnites, yields a calcite 87Sr/86Sr ratio for the suggested boundary level of 0.707425 ± 0.000021 (combined uncertainties based on line fit to stratigraphic dataset (±0.000004) and measurement of the standard (±0.000017)). Alternative uncertainties of ~±0.000008 are associated with the most extreme interpretation of sedimentation-rate history allowed by the strontium-isotope data (that is, abrupt changes in sedimen- tation rate at precisely the boundary level); however, sedimentological considerations, and measured strontium-isotope values at the boundary, support condensation rather than hiatus. Belemnite oxygen-isotope data suggest a significant temperature drop (~ 5°C) across the boundary at this locality.

Ichthyosaurs rapidly diversified and colonised a wide range of ecological niches during the Early and Middle Triassic period, but experienced a major decline in diversity near the end of the Triassic. Timing and causes of this demise and... more

Ichthyosaurs rapidly diversified and colonised a wide range of ecological niches during the Early and Middle Triassic period, but experienced a major decline in diversity near the end of the Triassic. Timing and causes of this demise and the subsequent rapid radiation of the diverse, but less disparate, parvipelvian ichthyosaurs are still unknown, notably be-cause of inadequate sampling in strata of latest Triassic age. Here, we describe an exceptionally large radius from Lower Jurassic deposits at Penarth near Cardiff, south Wales (UK) the morphology of which places it within the giant Triassic shastasaurids. A tentative total body size estimate, based on a regression analysis of various complete ichthyosaur skele-tons, yields a value of 12–15 m. The specimen is substantially younger than any previously reported last known occur-rences of shastasaurids and implies a Lazarus range in the lowermost Jurassic for this ichthyosaur morphotype.

The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The... more

The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The discovery of several well-preserved, relatively intact,
fossil logs at several locations in Rainbow Draw and one location in Miners Draw, both near Dinosaur National Monument (Utah), has provided an opportunity to study the local paleobotany, stratigraphy, and sedimentology of the Morrison Formation in northeastern Utah. The Morrison Formation in northeastern Utah consists of four members. In ascending chronostratigraphic order, they are the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The lithology (including the presence of glauconite grains) and fossil assemblage of the lower two members (Windy Hill and Tidwell) indicate a marine to marginal marine (coastal plain) depositional environment, whereas the lithology, fossil flora and fauna assemblage of the upper two members (Salt Wash and Brushy
Basin) indicate a fluvial–lacustrine depositional environment.
At least 10 fossil log sites in Rainbow Draw have been documented so far, and geologic mapping indicates that the logs and wood all occur in the same stratigraphic interval within the Salt Wash Member, approximately 17 to 27 m above the base of the member. The unit containing the logs and wood is about 11 m thick and consists of very fine to fine-grained sandstone and siltstone with indistinct bedding and no discernible sedimentary features. The logs are siliceous, some have a
coaly exterior, and they range in exposed length from 0.5 to 11 m and reach diameters up to 1.1 m. In the Miners Draw area, a single siliceous log is documented in the upper part of the Salt Wash Member within a silty sandstone unit that is 4 m thick; its exposed length is about 6 m. Although the correlation of the Miners Draw log-bearing interval to the interval in Rainbow Draw is uncertain, both units are lithologically similar and both occur in the upper part of the Salt Wash Member. The logs have been identified as araucariaceous conifers that pertain to the same taxon originally described as "Araucarioxylon hoodii" Tidwell et Medlyn 1993 from Mt. Ellen in the Henry Mountains of southern Utah. Concurrent systematic work will prompt a nomenclatural transfer of this
species to the genus "Agathoxylon."
Based on the abundance of large fossil logs and wood in the same stratigraphic interval in Rainbow Draw, we hypothesize that the area was covered by stands of moderately large trees of araucariaceous conifers. The sedimentological evidence suggests that the trees were not transported far from their original site of growth before they were deposited in a low-energy floodplain environment.

The shallow marine sedimentary sequence of the Jaisalmer Basin exhibits one of the important and well-developed Tithonian Sedimentary outcrops for western India. The ichnology and ichnofabric of the lower part of Bhadasar Formation (i.e.,... more

The shallow marine sedimentary sequence of the Jaisalmer Basin exhibits one of the important and well-developed Tithonian Sedimentary outcrops for western India. The ichnology and ichnofabric of the lower part of Bhadasar Formation (i.e., Kolar Dongar Member) belonging to Tithonian age are presented and discussed. The Kolar Dongar Member represents a shallow marine succession that contains 16 ichnotaxa: Ancorichnus ancorichnus, Conichnus conicus, Gyrochorte comosa, cf. Jamesonichnites heinbergi,
Imponoglyphus kevadiensis, Laevicyclus mongraensis, Monocraterion tentaculatum, Ophiomorpha nodosa, Palaeophycus tubularis, P. bolbiterminus, Phycodes palmatus, Planolites beverleyensis, Rhizocorallium isp., Rosselia rotatus, R. socialis, and Teichichnus rectus. The ichnofabric analysis divulges five distinct ichnofabrics, each typifying distinct depositional environment within shallow marine conditions. The ichnofabric Ophiomorpha 1 with syn-sedimentary faulting exemplifies high energy conditions typical of lower shoreface environment, whereas the Ophiomorpha 2 ichnofabric typifies upper shoreface environment. The Ancorichnus ichnofabric reflects lower offshore condition of deposition. The high ichnodiversity Ancorichnus–Rosselia ichnofabric is indicative of inner shelf conditions, while low ichno-diversity Teichichnus ichnofabric indicates prevalence of low energy brackish bay environment. Thus, Tithonian Kolar Dongar Member indicates depositional environment ranging from shoreface to offshore to inner shelf and finally to brackish bay environment.

The Lower Jurassic Whitmore Point Member is a widespread lacustrine unit at the top of the Moenave Formation that can be traced across southwestern Utah and northeastern Arizona. The shoreline to the northeast of the outcrop belt trends... more

The Lower Jurassic Whitmore Point Member is a widespread lacustrine unit at the top of the Moenave Formation
that can be traced across southwestern Utah and northeastern Arizona. The shoreline to the northeast of the
outcrop belt trends northwest to southeast, and the central part of the lake is interpreted to be southwest of the outcrop
belt. The detailed description of two of the most southwestern (offshore) sections at the St. George Dinosaur
Discovery Site at Johnson Farm in southwestern Utah and a reference section at Potter Canyon near the type section
in north-central Arizona reveals that two major lake cycles are recorded by these strata. Available paleomagnetic
and biostratigraphic data support an earliest Jurassic (Hettangian) age for the upper portion of the strata and possibly
the entire Moenave Formation or not.

The Henry Mountains basin is outlined by Middle Jurassic formations to form a southward pointing, triangular basin. An interval of mostly eolian sandstone and some intercalated non-eolian beds lies between the Navajo Sandstone (below) and... more

The Henry Mountains basin is outlined by Middle Jurassic formations to form a southward pointing, triangular basin. An interval of mostly eolian sandstone and some intercalated non-eolian beds lies between the Navajo Sandstone (below) and Carmel Formation (above). These beds were known as the Harris Wash Tongue of the Page Sandstone but are redefined here as Temple Cap Formation because their stratigraphic position and isotopic age data indicate that they are time equivalent to the
Temple Cap Formation of southwestern Utah. The Temple Cap Formation is preserved throughout most of the basin but is missing in some areas, especially along the Waterpocket Fold. Its irregular
thickness is likely because of deposition on a paleotopographic surface developed by the J-1 unconformity on the Navajo Sandstone. West of the Henry Mountains basin was a significant paleohigh over which the Temple Cap Formation is missing.
The Carmel Formation in the Henry Mountains basin conformably overlies the Temple Cap Formation and includes (in ascending order) the Judd Hollow, Crystal Creek, Paria River, and Winsor
Members. The lower two members comprise the first marine transgressive-regressive cycle of the Sundance sea that flooded into Utah from the north. The upper two members comprise the second marine transgressive-regressive cycle. Each member is recognizable throughout the basin; however, they become sandier in the northwestern part of the basin because of an influx of sand that dominated deposition from north-central Arizona across the Kaiparowits basin and into the northwest corner of the Henry Mountains basin. This is particularly evident in the first marine transgressive-regressive cycle in which the typically fine-grained red beds (sandstone and siltstone) of the Crystal Creek Member
are sharply replaced with mostly eolian sandstone. In the areas where eolian sandstone dominates, the name Thousand Pockets Member is used. The Judd Hollow Member is an important and recognizable marker unit (even in the areas of sand-dominated deposition) that provides the means to separate the eolian beds of the redefined Temple Cap Formation from the Thousand Pockets Member. In those areas, we reassign the Thousand Pockets Tongue of the Page Sandstone to the Thousand Pockets Member of the Carmel Formation.
We recommend that Page Sandstone be restricted to Arizona where the Judd Hollow Member thins to a feather edge or is missing, making it difficult to separate the Temple Cap Formation from the Thousand Pockets Member. Finally, we recommend abandoning the use of Gypsum Spring Formation south of the Uinta arch, and instead placing these rocks in the Temple Cap Formation.

"A biostratigraphic and systematic study based on belemnites collected along with ammonites was performed on four sections in the Subalpine Basin (SE France): Lac du Castillon and La Baume (Castellane area), Galabrun and Grand Lara (Gap... more

"A biostratigraphic and systematic study based on belemnites collected along with ammonites was performed on four sections in the Subalpine Basin (SE France): Lac du Castillon and La Baume (Castellane area), Galabrun and Grand Lara (Gap area). The specimens, originating from hemi-pelagic marl-limestone alternations in the lower part of the ‘‘Calcaires a ` Zoophycos’’ Formation, are dated from Middle Aalenian (Murchisonae Zone) to Lower Bajocian (Humphriesianum Zone). Five belemnite taxa
(Megateuthis elliptica, Holcobelus munieri, H. trauthi, Pachybelemnopsis roettingensis, Hibolithes sp.) have been identified, and two more taxa are reported in an open nomenclature (Belemnitida incertae sedis sp. 1 and sp. 2). The biostratigraphic range of the belemnite fauna is established. The new findings contribute to a more detailed understanding of the paleobiogeography of holcobelid belemnites that flourished at the northern margin of the Tethys Ocean and formed a distinct sub-Mediterranean fauna. The association herein described is similar to the fauna of the Calabro-Peloritani Arc (Calabria, Italy), a further hint for the supposed paleogeographic position of the latter during the Middle Jurassic."

Current chemostratigraphical studies of the Jurassic System primarily involve the use of one sedimentary component (marine organic carbon), one divalent transition metal substituted in carbonate (manganese), and two isotopic tracers:... more

Current chemostratigraphical studies of the Jurassic System primarily involve the use of one sedimentary component (marine organic carbon), one divalent transition metal substituted in carbonate (manganese), and two isotopic tracers: strontium-isotope ratios (87Sr/86Sr) and carbon-isotope ratios (δ13Ccarb and δ13Corg) in carbonate and in organic matter. Other parameters such as Mg/Ca and Sr/Ca ratios in calcite, oxygen-isotope ratios (ä18O) in carbonate, sulphur-isotope ratios (δ34S) in carbonate-hosted sulphate, nitrogen- isotope ratios (δ15Norg) in organic matter, osmium-isotope ratios (187Os/188Os) in black shales and neodymium-isotope ratios (143Nd/144Nd) in various mineral phases are also useful but at present give poor resolution because the database is incomplete or compromised by various factors. Stratigraphical patterns in total organic carbon (TOC) can be of either local or regional significance, depending on the lateral extent of the former nutrient-rich and productive water mass. Divalent manganese follows a similar pattern, being concentrated, most probably as a very early diagenetic phase, only in oxygen-depleted waters that typically underlie zones of elevated organic productivity. Shifts in Mg/Ca and Sr/Ca ratios on the time scale of ammonite subzones seem largely to reflect temperature changes. Strontium-isotope ratios from pristine skeletal calcite provide a global signal; δ13C values from carbonates with minimal diagenetic overprint potentially do the same, although small spatial differences in palaeo-water-mass composition may have been locally significant. Oxygen-isotope determinations on carbonate rocks and fossils generally yield values that are too scattered to be stratigraphically useful, because they reflect palaeotemperature, the evaporation–precipitation balance in sea water and the impact of any diagenesis involving an aqueous phase. Nitrogen-isotope ratios in organic matter reflect the chemistry of ancient water masses as affected by nitrate utilization and denitrification, and the stratigraphical pattern of this parameter is more likely to correlate only on a regional basis. Neodymium- isotope ratios in sea water are also water mass dependent and greatly affected by regional sources and oceanic current systems. Preliminary data on sulphur-isotope ratios in carbonates and osmium-isotope ratios in organic-rich shales, both potentially offering global correlation, indicate that these tracers may be valuable, although the records at present are not sufficiently well established to allow high-resolution regional correlation. In all cases, biostratigraphically well-dated reference sections, against which the relevant geochemical data have been calibrated, are required in the first instance. To date, studies on the stratigraphical distribution of organic carbon have been principally carried out in both northern (Boreal) and southern (Tethyan) Europe; carbon- isotope stratigraphy has been undertaken primarily, but not exclusively, on bulk pelagic sediments from the Alpine–Mediterranean or Tethyan domain; and strontium-isotope stratigraphy has been undertaken largely on calcitic skeletal material (belemnites and oysters) from northern and southern Europe. In many sections, including those containing ammonites, multi-parameter chemostratigraphy can give resolution that exceeds that attainable by classic biostratigraphical means. Strontium-isotope ratios in skeletal calcite are a particularly powerful tool for illustrating changes in sedimentary rate and revealing gaps in the stratigraphical record.

Detailed sedimentological, sequence stratigraphical and cyclostratigraphical analyses have been made from four lower Tithonian–lower Valanginian sections of the Vaca Muerta Formation, exposed in the southern Mendoza area of the Neuquén... more

Detailed sedimentological, sequence stratigraphical and cyclostratigraphical analyses have been made from four lower Tithonian–lower Valanginian sections of the Vaca Muerta Formation, exposed in the southern Mendoza area of the Neuquén Basin, Argentina. The Vaca Muerta Formation is characterized by decimetre-scale rhythmic alternations of marls, shales and limestones, and consists of five facies associations, which reflect different paleoenvironmental conditions: basin to restricted outer ramp, outer ramp, and middle ramp. Vertical organization within the Vaca Muerta Formation shows a well-ordered hierarchy of cycles, where elementary cycles, bundles and superbundles with frequencies within the Milankovitch band have been recognized. According to biostratigraphic data, elementary cycles have a periodicity of ~ 20 ky, which correlates with the precession cycle of Earth's axis. Spectral analysis based on series of cycle thickness allows us to identify frequencies of about 400 ky and 90–120 ky, which we interpret as the modulation of the precessional cycle by the Earth's orbital eccentricity. Cycles are probably driven by variations in carbonate exportation, as fluctuations in shallow-water carbonate production involve modifications in carbonate basinward exportation. Cyclostratigraphic data allowed us to build a floating orbital scale for the Tithonian–lower Valanginian interval in the Neuquén Basin. Correlation between studied sections allowed us to recognize a discontinuity between the Substeueroceras koeneni and Argentiniceras noduliferum ammonite zones in the Malargüe Anticline area. Orbital calibration of these sections is consistent with Riccardi's biostratigraphic scheme, wich place the Jurassic-Cretaceous boundary within the Substeueroceras koeneni ammonite Zone. On the other hand, the base of the Vaca Muerta Formation (Virgatosphinctes mendozanus ammonite Zone) would be probably placed in the base of the middle Tithonian rather than the lower Tithonian, which is also consistent with our preliminary palaeomagnetic data.

The Lower Jurassic Whitmore Point Member is a widespread lacustrine unit at the top of the Moenave Formation that can be traced across southwestern Utah and northeastern Arizona. The shoreline to the northeast of the outcrop belt trends... more

The Lower Jurassic Whitmore Point Member is a widespread lacustrine unit at the top of the Moenave Formation that can be traced across southwestern Utah and northeastern Arizona. The shoreline to the northeast of the outcrop belt trends northwest to southeast, and the central part of the lake is interpreted to be southwest of the outcrop belt. The detailed description of two of the most southwestern (offshore) sections at the St. George Dinosaur Discovery Site at Johnson Farm in southwestern Utah and a reference section at Potter Canyon near the type section in north-central Arizona reveals that two major lake cycles are recorded by these strata. Available paleomagnetic and biostratigraphic data support an earliest Jurassic (Hettangian) age for the upper portion of the strata and possibly the entire Moenave Formation.

Sediments of Kimmeridgian and Tithonian age are well exposed on the Boulonnais coast of northern France between Equihen and Cap Gris Nez and on the south coast of England at and adjacent to Kimmeridge Bay. Both successions were deposited... more

Sediments of Kimmeridgian and Tithonian age are well exposed on the Boulonnais coast of northern France between Equihen and Cap Gris Nez and on the south coast of England at and adjacent to Kimmeridge Bay. Both successions were deposited on a marine shelf and lie within the Subboreal faunal province which enables detailed correlations to be made between them based on ammonite assemblages. They are, however, lithologically markedly different due to their environmental settings: close to a land area in the case of the Boulonnais and
within a depositional basin in the case of Kimmeridge. The succession adjacent to the Kimmeridgian-Tithonian boundary exposed in the Boulonnais is highly condensed and laterally variable with more attenuated successions occurring close to the former Anglo-
Brabant Massif land area. The boundary occurs at the end of a succession of up to six regressive-transgressive events that onlap the land area. This is in contrast to that at outcrop at Kimmeridge, where the Kimmeridgian-Tithonian boundary is marked by a correlative
conformity in an unbroken basinal succession. The cliff and foreshore exposures in the Kimmeridge area provide the only unbroken succession in the Subboreal faunal province of the beds adjacent to the Kimmeridgian-Tithonian boundary.

Belemnites are the extinct coleoid cephalopods, which flourished worldwide in the Jurasso−Cretaceous oceans (Doyle et al., 1994). The distribution of belemnite genera and families ... A LATE MIDDLE JURASSIC BOREAL BELEMNITE... more

Belemnites are the extinct coleoid cephalopods, which flourished worldwide in the Jurasso−Cretaceous oceans (Doyle et al., 1994). The distribution of belemnite genera and families ... A LATE MIDDLE JURASSIC BOREAL BELEMNITE CYLINDROTEUTHIS FROM CENTRAL JAPAN AND ...

The aim of this paper is to document the ammonite fauna of the upper part of the Late Tithonian collected at the key section of Le Chouet (Drome, SE France). Emphasis is laid on new and poorly known Ataxioceratidae, Himalayitidae and... more

Qualitative and quantitative studies on calcareous nannofossils have been carried out on the Middle–Upper Bathonian succession of Gnaszyn (Kraków-Silesia Homocline, Czêstochowa region). The nannofossil assemblages are moderately or... more

Qualitative and quantitative studies on calcareous nannofossils have been carried out on the Middle–Upper Bathonian succession of Gnaszyn (Kraków-Silesia Homocline, Czêstochowa region). The nannofossil assemblages are moderately or well-preserved and are dominated by Watznaueria britannica; also common are Staurolithites lumina and Zeugrhabdotus erectus. The presence of delicate nannofossil forms together with dissolution- resistant taxa shows that the changes in composition of some of the nannoplankton assemblages reflect original variations. The frequency and diversity changes of the calcareous nannofossil assemblages have been interpreted in relation to fluctuations of sedimentation rate versus changes in trophic conditions within the photic zone. The highest diversity assemblages contain a high percentage of palaeofertility indicators, and are impoverished in the genus Watznaueria. This is interpreted as a reflection of a lower sedimentation rate and more stable, possibly mesotrophic conditions within the photic zone. On the other hand, W. britannica-dominated assemblages with low species diversity may represent more unstable environments with a high influx of terrestrial material related to a high sedimentation rate and a high nutrient influx, i.e. eutrophic conditions in the photic zone.

Our tentative proposal is that several biological markers have potential to help define any putative boundary in the traditional basal Berriasian interval. That is, between the base of the Berriasella jacobi Subzone and the base of the... more

Our tentative proposal is that several biological markers have potential to help define any putative boundary in the traditional basal Berriasian interval. That is, between the base of the Berriasella jacobi Subzone and the base of the Pseudosubplanites grandis Subzone, and therefore straddling the base of magnetozone M18r. Promising micropalaeontological markers are the FADs of Nannoconus steinmannii minor and N. kamptneri minor, plus the base of the Calpionella alpina Zone, and the bloom(s) of Calpionella alpina and Crassicollaria parvula. The testing and calibration of this constraining event-matrix in the most complete and fossiliferous sections is our task for the near future.