Mesozoic Stratigraphy

Until now dinosaur tracks from Switzerland were only known
from Triassic and Late Jurassic strata. We report here for the first
time the occurrence of ornithopod tracks from the Schrattenkalk
Formation (Late Aptian) from the Swiss Central Alps. The locality
is situated in an abandoned quarry on the shore of Lake
Lucerne close to the village of Beckenried.
The steeply inclined surface has more than 50 tracks ( in three
trackways) of ornithopod dinosaurs that are attributed to iguanodontids.
Three trackways can be followed for distances of 25 to
35 m. The lengths of the footprints (mean: 30 cm) point to animals
ranging in size of from 4 to 6 m, with estimated hip heights between
1.8 and 2 m (hip height 6 FL) and 1.4 to 1.7 m (hip height 5
FL). One of the trackways shows two succesive manus impressions,
indicating facultative quadrupedal gait.
The track bearing layer consists of shallow water micrites with
traces of emersion, and it is overlain by bioclastic grainstones.
Previously the Upper Schrattenkalk Member in the Helvetic
realm was thought to have formed on a large shelf far away from
any continents. The present discovery will shed new light on the
paleogeographic position of the Helvetic nappes.

The southern Alps were characterized by strong variations,
both in space and time, of heat flow during Mesozoic rifting.
The regional thermal history was reconstructed using organic
matter (OM) maturity data from outcropping sediments.
One-dimensional (1-D) thermal modeling performed on selected
successions suggests thatOMmaturity wasmainly controlled
by high geothermal gradients (heat flow peaks of 85 to
105 mW/m2 in the Middle Jurassic) and differential burial
during Norian–Early Jurassic extensional phases. The results
of 1-D modeling show an eastward increase of heat flow peak
values.
These results were compared with those obtained with
two-dimensional (2-D) thermokinematic models. Themodels
show a time shift (ca. 10 Ma) in the heat-flow peak (Aalenian-
Bajocian for 2-D and Bajocian for 1-D modeling). However,
the Bajocian age was a priori imposed on 1-Dmodels.Available
geochemical data could be fitted assuming Aalenian-Bajocian
peak ages. Consequently, this misfit is not alarming. The eastward
increase in heat-flow peak values is tentatively explained
with an eastward increase of radiogenic heat production in the
crust instead of with differential stretching.
The comparison of paleothermal data and numericalmodeling
was done to gain knowledge on the potentials and limitations
of numerical modeling in frontier areas. Although some differences do exist in the results of geochemical and thermokinematicmodels,
we can conclude that if a reasonable knowledge
of the thermal parameters of both covers and basement is
available, thermokinematic modeling can provide useful firstorder
estimates in frontier areas of heat flow and temperature
evolution through time.

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 Mesozoic Era of the Western Interior of the United States was dominated by sedimentation in shallow marine
and continental settings behind a magmatic arc developed along the western margin of the continent. Part of the history
of this magmatism is preserved as altered volcanic ash enclosed in sedimentary rocks. For the Mesozoic of the Western
futerior, we have compiled from the literature the ages and locations of discrete volcanic ash beds (mostly bentonites)
and ash-rich rocks (e.g., analcime-rich or bentonitic mudstones). These data are plotted on a series of eight
paleogeologic maps and compared with the locations of contemporaneous Mesozoic sedimentary and plutonic rocks.
From these maps we infer:
(1) Most ash was erupted from volcanoes in the arc during plinian eruptions of silicic magma associated with
caldera-collapse and emplacement of ignimbrite. The ash was deposited as pyroclastic fall, and then reworked
physically and chemically by sedimentary processes.
(2) Ash-producing volcanism was intermittent with pulses separated by as few as several million years to as many
as forty million years.
(3) Major periods of volcanism occurred during the Late Triassic (about 225 Ma), during the Middle Jurassic (about
160 to 140 Ma), and during two periods in the Late Cretaceous, peaking in the Cenomanian (about 95 Ma) and again
near the Campanian-Maastrichtian boundary (about 75 Ma). Volcanic quiescence prevailed during the Early and
Middle Triassic, from the latest Triassic to the Middle Jurassic, and perhaps during the early Cretaceous.
(4) Volcanic episodes correlate closely with the temporal pattern of pluton emplacement in the western United
States.
(5) The location and extent of the arc plutonic belt and the distribution of ash in each time interval constrain the
locations of the volcanoes from which the ash erupted For example, the bentonitic mudstones of the Late Triassic Chinle
Formation contain ash probably erupted from volcanoes in what is now southeastern California, southern Arizona, and
northern Mexico. Middle and Late Jurassic ashes probably erupted from near the continental margin from vents in what
is now the Sierra Nevada Batholith, whereas Cretaceous ashes erupted from the Idaho and Boulder batholiths as well
as the Sierra. As a result of the distribution of these magmatic systems, no volcanic ash is preserved in sedimentary rocks
in Montana that are older than Aptian (mid- Cretaceous).
( 6) Two general types of vent regions may have erupted compositionally distinct ashes. Continental margin regions
are typified by the northern or western Sierra igneous suites and the Idaho and Boulder batholiths comprise a continental
interior suite.
(7) in the Western Interior, Mesozoic sedimentary rocks are not widespread during times of magmatic quiescence.
This relationship can be explained if periods of slow sea-floor spreading increased the volume of the ocean basins,
caused elevation of the continental margins, and decreased rates of intrusion and volcanism above the slab being
subducted beneath the western margin of North America.

2016. The Late Triassic and Early Jurassic fissure faunas from Bristol and South Wales: Stratigraphy and setting. Palaeontologia Polonica 67, 257–287. 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 deposit in the region is Pliensbachian. The age range of the fissures thus shrinks to c. 20 Myr, and the first episode of tetrapod fissure infilling shifts from the time of the Carnian " pluvial " episode, to the early Rhaetian, when western Europe was undergoing major rifting associated with the beginning of the opening of the North Atlantic, and when the Rhaetian sea flooded over landscapes that had long been purely terrestrial and arid. We recognise clear changes in the faunal composition of the terrestrial vertebrate biota from the early Rhaetian, dominated by reptile taxa, with some mammaliamorphs, that then declined rapidly in diversity before the Hettangian. This herpe-tofauna was followed by three faunal assemblages in the Early Jurassic of St. Brides which became increasingly diverse following the end-Triassic mass extinction; each had prominent mammaliamorphs as well as high numbers, but few species, of rhynchocephalians.

The Faciès Rognacien is a sequence of highly bioturbated and pedogenically modified palustrine carbonates that were deposited under oxic conditions around the
Cretaceous-Tertiary (K-T) boundary in the northeastern Pyrenean foreland basin (SW France). The sedimentary structures and early diagenetic features identified
(mottling, nodule formation, brecciation, pseudomicrokarst, cracking, charophytes, Microcodium) suggest deposition in a palustrine environment between the subarid
and intermediate climate type. Sedimentological and paleoecological analysis enables us to distinguish two facies associations, the lacustrine pond facies and the freshwater
marsh facies associations. The majority of the carbonates are attributed to the freshwater marsh facies. The lacustrine pond facies occurs only in isolated paleolows, and is identified on the basis of its paleobiological content (charophytes, ostracodes).
This suggests that the palustrine carbonates of the Faciès Rognacien were deposited in a seasonal wetland (carbonate-producing freshwater marsh), rather than in the marginal zone of a large, shallow lake. In this wetland paleoenvironment, all carbonates underwent widespread pedogenesis, and small, ephemeral ponds are of limited distribution, most likely recording deposition in paleolows.

In 2003 vertebrate tracks attributed to pterosaur, crocodiles, turtles, hadrosaurs and sauropods have been reported from a locality close to Sabinas (Coahuila) in the Sierra Madre Oriental (Maastrichtian). Three trackways of medium-sized theropods could be observed. Evenly spaced parallel scratches forming a trackway might have been left by a swimming pterosaur. Furthermore a clear tetradactyl imprint, with claw marks only
can be temptatively assigned to a pterosaur. So far, we have observed tracks of theropods only and probable prints of pterosaurs. The purported turtle tracks are small paired and tripled very faint scratches that have been produced by a xiphosuran arthropod. These are the first limulid tracks from Mexico. Another locality, Santa Helena, close to the village of Melchior Musquiz (Campanian) yields several surfaces with dinosaur fooprints.
The best preserved trackway is attributed to a large theropod.

2016. The Late Triassic and Early Jurassic fissure faunas from Bristol and South Wales: Stratigraphy and setting. Palaeontologia Polonica 67, 257–287. 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 pre...

2016. The Late Triassic and Early Jurassic fissure faunas from Bristol and South Wales: Stratigraphy and setting. Palaeontologia Polonica 67, 257–287. 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 pre...

RESUMEN Se propone, por primera vez, un cuadro estratigráfico integrado para las unidades pospaleozoicas en la Precordillera Septen-trional sobre la base de las exposiciones comprendidas entre las quebradas de Santo Domingo y El Peñón. Esta área resulta una región crítica, no sólo para la estratigrafía de la Precordillera Septentrional, sino también como sección de referencia para la co-rrelación entre las unidades aflorantes en las Sierras Pampeanas y en el norte de Chile. Se han reconocido 6 unidades compren-didas entre el Triásico Tardío y el Mioceno-Plioceno? La más antigua corresponde a la Formación Santo Domingo, unidad de bancos rojos datada en el Triásico Tardío-Jurásico Temprano sobre la base del estudio de la xiloflora y dataciones radimétricas. Esta unidad es cubierta en discordancia por la Formación Ciénaga del Río Huaco (Cretácico Tardío), en la que han sido repor-tados restos óseos de titanosaurios. La Formación Puesto La Flecha (Eoceno tardío-Oligoceno) inicia el registro cenozoico de la comarca, y corresponde a una sucesión preorogénica a los primeros movimientos andinos compuesta por areniscas y pelitas formadas en ambientes fluviales de baja energía y cuerpos lacustres someros. La orogenia andina en la región está representa-da en las areniscas eólicas de la Formación Vallecito (Oligoceno tardío-Mioceno temprano), la que fue sedimentada bajo con-diciones áridas en un contexto de cuenca de antepaís hambrienta. Estas rocas son sucedidas por la unidad de " conglomerados y areniscas Refugio del Peñón " , formada por la progradación de cuñas clásticas desde el arco magmático y de los cabalgamien-tos más occidentales de la orogenia andina en la Argentina. Finalmente, el " conglomerado La Falda " indica el desplazamiento hacia el este del orógeno andino y el ascenso y destechado del granito que forma el núcleo de la Sierra del Peñón. ABSTRACT Stratigraphy of the Neogene, Paleogene and Mesozoic successions of the Santo Domingo and El Peñón creeks (Northern Precordillera of La Rioja) Geological surveys carried out in the Santo Domingo and El Peñón creeks allow, for the first time, proposing an integrated stratigraphic model for the post-Paleozoic units outcropping in the Precordillera Septentrional. The area encompassing the Santo Domingo and El Peñón creeks is a key section not only for the stratigraphy of the Precordillera but also for regional correlations with units of similar age from the Sierras Pampeanas and north of Chile. Six stratigraphic units between the Late Triassic and the Miocene were recognized. The oldest corresponds to the Santo Domingo Formation, a red bed sequence composed of conglomerates, sandstones and mudstones wich was dated in the Late Triassic-Early Jurassic based on the study of the xyloflora and a radiometric age. This unit is unconformably covered by sandstones and mudstones belonging to the Ciénaga del Río Huaco Formation (Late Cretaceous) which provided some skeletal remains of Titanosaurios. The Puesto La Flecha Formation (late Eocene–Oligocene) comprises sandstones and mudstones deposited in ephemeral fluvial systems together with shallow water bodies (Lower Member) and eolian dunes (Upper Member). The onset of the Andean Orogeny in the studied region is represented in the eolian sandstones of the Vallecito Formation (late Oligocene – early Miocene) which was formed in arid conditions within an underfilled foreland basin. These rocks are succeeded by the informally called unit of " conglomerates and sandstones Refugio del Peñón " that represent the progradation of clastic wedges from the volcanic arc located to the west. Finally, the informal unit of " conglomerates La Falda " points out the displacement towards the west of the Andean orogenic front and the uplift and unroofing of the granitic rocks forming the core of the Sierra del Peñón.

The Kota Formation of the Pranhita-Godavari Basin is well known for its fossil fauna and flora especially for its silicified woods. However, the palaeoflora and its palaeoclimatic significance within the formation are poorly known. In spite of the fact that the formation yields a rich fauna and flora chronostratigraphic problems still exist. The present study aims to analyze the palaeofloras from the Kota Formation to understand their diversity and palaeoecological significance. We also describe a new species Agathoxylon kotaense belonging to the conifer family Araucariaceae. Our study shows that the flora was dominated by conifers and that it is comparable to that of the ?Late Jurassic-Lower Cretaceous Gangapur Formation, Pranhita-Godavari Basin and that of the Rajmahal Formation of the Rajmahal hills. The growth ring pattern and leaf fossil assemblage suggest that the growth conditions were seasonal, but mostly stressed.

A crinoid Lagerstatte of Chariocrinus wuerttembergicus
(Opalinuston Formation, Aalenian, Middle Jurassic) was
formed under storm conditions. The Lagersta¨ tte is oriented
parallel to paleowave crests, and exhumed concretions indicate
sediment reworking. Paleoflowwas nearly perpendicular
to (storm-) wave ripple-crests and was directed towards
a depocenter to the south-southeast. Both waves and
currents affected crinoid parts, such as stems, and document
combined flow conditions. The crinoids lived on a lowrelief
swell somewhat above stormwave base in amuddy environment,
and caused their own in-situ burial. During a
storm, wave agitation led to suspension of sediments extending
into the habitat of the crinoids. The crinoids provided
additional friction within the near-bottom, suspension-
rich, agitated water body, thereby reducing the speed of
water currents. This led to sediment deposition, and the crinoids
were buried in fine-grained sand and silt. In thisway,
they induced their own burial; therefore, the Lagersta¨ tte is
the product of a feedback process. Rapid burial of the crinoids
led to their excellent preservation. Articulated preservation
is possible only if the flow was too slow to remove the
crinoids from their substrate. Some crinoids tried to escape
these hostile conditions by autotomizing their crowns, but
these were pushed down to the seafloor by oscillatory water
movement, and were immediately covered, mouth upward,
by sediments. The preserved crowns provide an estimate of
the population density in the range of 110 animals m22,
which is a minimumvalue because some crowns might have
been washed away before burial.

The Upper Triassic Chinle Formation and the Upper Jurassic Morrison Formation preserve a record of lacustrine deposition along the western margin of tropical Pangaea and post-Pangaean North America. The lake deposits in these formations contain archives of sedimentary and geochemical paleoclimatic indicators, paleoecological data, and characteristic stratal architecture that provide glimpses into the evolution of basins linked to global- and continental-scale tectonic events and processes, and the establishment of a mosaic of continental paleoecosystems. This field trip highlights the lacustrine and associated fl uvial deposits of the Monitor Butte Member of the Chinle Formation and the Tidwell and Brushy Basin Members of the Morrison Formation in the southern part of the Colorado Plateau region, with emphases on: (1) sedimentary facies analysis and paleogeography of the paleolakes; (2) stratal architecture and high-frequency sequence stratigraphy; (3) recognition of lake basin-fill ty...

Nd isotopes of fish debris collected from the English Chalk at Eastbourne (Sussex, UK) are used to reconstruct the history of ocean circulation in the NW European shelf sea during Oceanic Anoxic Event 2 (OAE 2, Cenomanian-Turonian). The Eastbourne ε Nd record exhibits a 1-unit negative excursion (decreasing from ∼−9 to ∼−10), immediately followed by a 3-unit positive excursion reaching ∼−7. The onset of the negative ε Nd excursion lags the global δ 13 C rise characteristic of OAE 2, suggesting stable patterns of ocean circulation in the NW European shelf sea at this time. Both negative and positive Ndisotope excursions took place during a transient cooling episode within OAE 2. The negative ε Nd excursion is interpreted as due to a change in ocean circulation with northerly sourced water masses becoming the dominant bottom waters at Eastbourne. The positive excursion is best explained by the transport of radiogenic Nd derived from a volcanic source, possibly the High Arctic or Caribbean large igneous province (LIP). An input of volcanic Nd may reconcile the Eastbourne record with coeval ε Nd records on Demerara Rise in the western tropical Atlantic. The broad synchroneity of high ε Nd values (∼−7) registered at both sites suggests a possible period with efficient oceanic mixing between the tropical Atlantic and the NW European shelf sea during the cooling episode. The Eastbourne ε Nd record of OAE 2, together with coeval temperature reconstructions, provides evidence for the coincidence of changes in ocean circulation and transient climatic cooling, implying a tight coupling between the two phenomena during this interval.

In Late Jurassic times, the Swiss Jura carbonate
platform occupied the transition between the Paris Basin
and the Tethys and thus connects the Boreal and Tethyan
realm. Up to now, the lack of index fossils in the Reuchenette
Formation prevented a reliable correlation between
both areas (its sediments are characterised by a prominent
sparseness of index fossils). Now, seven recently in situ
collected species of ammonites helped to establish a new
sequence-stratigraphical frame for the platform sediments
of the Reuchenette Formation in NW Switzerland. Based
on biostratigraphical data, five third-order sedimentary
sequences were assigned to the Late Oxfordian to Late
Kimmeridgian. The upper three third-order sequences
correspond to the Boreal sequences Kim3–5 of Hardenbol
et al. (1998). The deduced large-scale sea-level fluctuations
match those from other European regions (Spain, Russia).
This biostratigraphically based sequence-stratigraphical
frame is a prerequisite to refine correlations within a wider
area covering the Swiss Jura and parts of adjacent France
and Germany.

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...

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 Upper Triassic Chinle Formation and the Upper Jurassic Morrison Formation preserve a record of lacustrine deposition along the western margin of tropical Pangaea and post-Pangaean North America. The lake deposits in these formations contain archives of sedimentary and geochemical paleoclimatic indicators, paleoecological data, and characteristic stratal architecture that provide glimpses into the evolution of basins linked to global-and continental-scale tectonic events and processes, and the establishment of a mosaic of continental paleoecosystems. This fi eld trip highlights the lacustrine and associated fl uvial deposits of the Monitor Butte Member of the Chinle Formation and the Tidwell and Brushy Basin Members of the Morrison Formation in the southern part of the Colorado Plateau region, with emphases on: (1) sedimentary facies analysis and paleogeography of the paleolakes; (2) stratal architecture and high-frequency sequence stratigraphy; (3) recognition of lake basinfi ll types; and (4) paleontology and ichnology of lake strata and their paleoecologic, paleohydrological, and paleoclimatic interpretation.

The southern Alps were characterized by strong variations, both in space and time, of heat flow during Mesozoic rifting. The regional thermal history was reconstructed using organic matter (OM) maturity data from outcropping sediments. One-dimensional (1-D) thermal modeling performed on selected successions suggests that OM maturity was mainly controlled by high geothermal gradients (heat flow peaks of 85 to 105 mW/m 2 in the Middle Jurassic) and differential burial during Norian-Early Jurassic extensional phases. The results of 1-D modeling show an eastward increase of heat flow peak values.