The Paleobotanical Changes Across the Jurassic/Cretaceous Boundary in India

Integrated palaeobotanical and palynological analysis of subsurface Gondwana sedimentary succession (Jurassic–Cretaceous) in Jangareddygudem area, Chintalapudi Sub-basin, South India: Stratigraphical and phytogeographical implications

Authors:

Jha et al

Abstract:

Here we present an integrated palaeobotanical and palynological analysis of sub-surface terrestrial deposits of Jangareddygudem area, Chintalapudi Sub-basin, Godavari Graben, India. Plant megafossil impressions and palynomorphs were recovered in the bore core MJR-11 from Jangareddygudem area. Plant megafossils impressions: Equisetites sp., Ptilophyllum acutifolium, Pachypteris indica, Elatocladus jabalpurensis, Pagiophyllum gollapallensis, and Ptilophyllum cutchense are recorded at different depths in the bore core MJR-11. Palynological investigations carried out in these megafossil bearing beds reveal the presence of Coptospora sp., Ceratosporites equalis, Appendicisporites erdtmanii, Biretisporites spectabilis, Cicatricosisporites hughesii, Cicatricosisporites sp., Concavissimisporites sp., Contignisporites cooksoniae, C. fornicatus, C. glebulentus, C. multimuratus, C. psilatus, Converrucosisporites sp., Gleicheniidites sp., Klukisporites scaberis, Plicifera delicata, Balmeiopsis limbatus, Araucariacites australis, A. cooksonii, Callialasporites dampieri, C. monoalasporus, C. segmentatus, C. turbatus, Dacrycarpites australiensis, Podocarpidites ellipticus, Podosporites variabilis, Crybelosporites stylosus, and Foraminisporis wonthaggiensis. Very rare occurrence of monocolpate, tetracolpate and tricolpate pollen is also recorded. Both plant mega- and microfloral evidences indicate Late Jurrassic–Early Cretaceous (Tithonian–Valanginian) age for these sediments. A comparative study of present mega and microfossil assemblages with known megafloral and microfloral assemblage from the Upper Gondwana sediments of Godavari and other Indian basins has also been attempted. The floral assemblage clearly indicates the presence of Gangapur sediments in Jangareddygudem area.

Similarity of the Antarctic palynofloras with those known from Godavari and other basins on the east coast of India confirms continental reconstructions that show Lambert Graben of East Antarctica to have been contiguous with eastern India prior to Gondwana break-up. The non-marine character of the palynomorphs suggests that marine conditions in this region of the Godavari Graben did not develop until at least early Early Cretaceous time.

Climate Change During the Valanginian Cretaceous Vocontian Basin, France

Eccentricity paced monsoon-like system along the northwestern Tethyan margin during the Valanginian (Early Cretaceous): New insights from detrital and nutrient fluxes into the Vocontian Basin (SE France)

Authors:

Charbonnier et al

Abstract:

High-resolution changes in terrigenous and nutrient fluxes into the Vocontian Basin (northwestern Tethyan margin) were investigated for the Late Berriasian–Late Valanginian time interval, in order to assess the precipitation patterns in the source areas and to evaluate the effect of orbital forcing on the strength of the hydrological cycle. In this study, new high-resolution mineralogical (bulk-rock and clay fraction) and geochemical (phosphorus and oxygen isotope) data are used from the astronomically calibrated Orpierre section. For the first time, kaolinite, detrital, and phosphorus accumulation rates (KAR, DAR and PAR) are calculated and compared to a set of 547 geochemical, and 260 mineralogical published data from other Vocontian sections. It appears that three regional increases in the KAR document three successive humid episodes during the Valanginian. This is confirmed by contemporaneous increases in DAR and partly also in PAR, which highlight higher terrigenous and nutrient fluxes to the Vocontian Basin during these episodes. Concomitant decreases in the δ18Owhole-rock signals may reflect higher sea-surface temperatures during the early Valanginian and the early–late Valanginian transition. The occurrence of the three humid episodes is interpreted to relate to an orbital-paced monsoonal circulation pattern through seasonally reversing movements of air mass heat and precipitation over the northwestern Tethyan margin. In particular, based on the correlation between the 405 kyr eccentricity cycles and the KAR signal obtained at Orpierre, an eccentricity influenced monsoonal circulation is proposed as the possible forcing factor behind these climatic patterns. The average duration between the climaxes of the three regional wetter episodes is approximately 2.43 Myr. The wetter and likely also warmer episode at the early–late Valanginian transition is in step with the onset of the Weissert episode. In this regard, the intensification of monsoonal-driven precipitations appears as a possible external forcing factor leading or at least accelerating the important perturbation in the global Carbon cycle associated with the Weissert episode.

First Evidence of a Post Wildfire Debris Flow From the Valanginian (?) Cretaceous Algoa Basin

Lower Cretaceous deposit reveals first evidence of a post-wildfire debris flow in the Kirkwood Formation, Algoa Basin, Eastern Cape, South Africa

Authors:

Muir et al

Abstract:

The Algoa Basin is an onshore rift basin filled by an Upper Mesozoic non-marine and shallow marine sedimentary sequence. The middle unit of this clastic succession is assigned to the Lower Cretaceous Kirkwood Formation, known to host a wealth of plant and animal fossils together with poorly documented lignites, amber and charcoal clasts. This study is motivated by the growing interest in the impact of wildfires on the palaeoenvironment during the high-oxygen, Cretaceous world. It has been hypothesised that frequent and severe Cretaceous wildfires triggered large-scale non-marine denudation events, altering the sedimentation dynamics and influencing the evolution of ecosystems. In order to investigate this phenomenon, charcoal-bearing sedimentary rocks and plant fossil assemblages of the Kirkwood Formation have been studied at the Bezuidenhouts River locality, ∼50 km north of Port Elizabeth (Eastern Cape, South Africa).

Detailed field observations of the sedimentary facies suggest that deposition occurred in a meandering fluvial environment with mature, vegetated floodplains. Depositional trends within a charcoal-rich bed (i.e., stratification, flattening and decrease in charcoal clast size down-current) indicate that a charcoal-rich debris flow, linked to a post-wildfire flood event, became diluted by fluvial flow. Palaeocurrent indicators (e.g., orientation of fossil logs) suggest unidirectional currents from SW to NE, which are somewhat inconsistent with the previously reported regional palaeocurrent directions in the Kirkwood Formation.

To gain insights into the fire-influenced dynamics of the Early Cretaceous ecosystems, the macro-plant fossil assemblages of the Kirkwood Formation were considered, with reference to the responses of modern plant analogues to wildfire. Of the plant orders reported from macrofossils of the Kirkwood Formation, the Cycadales, Pinales and Filicales, are known to have produced large woody or fibrous trunks and stems, or in the case of the Bennettitales more densely branched, divaricate architectures, and are likely to have provided the bulk of fuel for wildfires, with fern elements dominating groundcover niches. The particular role of these plants in the Early Cretaceous wildfire palaeoecology of the Algoa Basin is a topic for an ongoing study, but the Bezuidenhouts River locality appears to record the aftermath of a severe crownfire that led to mass tree mortality.

There was a 4 C Temperature Drop at High Latitude During the Valanginian Cretaceous

Latitudinal temperature trends in the northern hemisphere during the Early Cretaceous (Valanginian - Hauterivian)

Authors:

Meissner et al

Abstract:

We present the first detailed stable isotope record (δ13C, δ18O) for the Valanginian (Lower Cretaceous) of the southern Boreal Realm. The observations are based on the geochemical analysis of 286 belemnite rostra from stratigraphically well-dated sections in northwest Germany. A major positive carbon isotope excursion (CIE) of ~ 2‰ in the early late Valanginian documents a perturbation of the carbon cycle. This positive CIE, which is well known as the 'Weissert Event' in the Tethys, is also displayed in composite carbon isotope records based on published and own data from three different palaeolatitudes (35°, 39°, 65° North). These findings suggest that the environmental changes indicated by the CIE in the early late Valanginian are synchronous, thereby pointing to a global control. The combined oxygen isotope data sets show long-term fluctuations of up to 7 °C with a cooling in the late Valanginian for both the southern and the arctic part of the Boreal Realm, while Tethyan data document only a ca. 1 °C cooling. Based on a reliable bio- and chemostratigraphic correlation between the different realms this study highlights the amplitude of the environmental perturbations in the Valanginian and supports the idea that a combination of regional and global factors caused such shifts.

Relic Sauropod Lineage From Berriasian/Valanginian Cretaceous North America

The oldest Cretaceous North American sauropod dinosaur

Authors:

D'emic et al

Abstract:

Sauropod dinosaurs have been found in sediments dating to most of the Cretaceous Period on all major Mesozoic landmasses, but this record is spatiotemporally uneven, even in relatively well-explored North American sediments. Within the 80 million-year-span of the Cretaceous, no definitive sauropod occurrences are known in North America from two ca. 20–25 million-year-long gaps, one from approximately the Berriasian–Barremian and the other from the mid-Cenomanian–late Campanian. Herein, we present an undescribed specimen that was collected in the middle part of the twentieth century that expands the known spatiotemporal distribution of Early Cretaceous North American sauropods, partially filling the earlier gap. The material is from the Berriasian–Valanginian-aged (ca. 139 Ma) Chilson Member of the Lakota Formation of South Dakota and appears to represent the only non-titanosauriform from the Cretaceous of North America or Asia. It closely resembles Camarasaurus and may represent a form closely related to that genus that persisted across the Jurassic–Cretaceous boundary.

Evidence of Valginian Cretaceous Weissert Event

The mid-Valanginian Weissert Event as recorded by calcareous nannoplankton in the Vocontian Basin

Authors:

Mattioli et al

Abstract:

The mid-Valanginian Weissert Event represents one of the most significant paleoceanographic events of the Early Cretaceous and is characterized by a major perturbation of the carbon cycle testified by a positive carbon isotope shift, a crisis of both neritic and pelagic carbonate producers, and climatic fluctuations. Here we propose a paleoreconstruction of paleoenvironmental changes that occurred in the reference Vergol and La Charce sections (Vocontian Basin, SE France) during the Weissert Event based on the analysis of calcareous nannofossil absolute abundance and assemblages. These latter are compared to newly acquired and already published sedimentological and organic geochemical analyses. Our approach is novel for the time interval considered. Indeed, Principal Component Analysis was applied for the first time to the entire nannofossil assemblage to reconstruct environmental conditions, instead of using paleoecological preferences of single species. The comparison of calcareous nannofossils and biomarker analyses indicates that a phase of severe sea–water stratification occurred prior to the carbon positive excursion of the Weissert Event in the Vocontian Basin. This was followed by a raise in fertility of surface waters, as attested by increased nannofossil abundances, in particular, of meso–eutrophic taxa, and biomarkers likely produced by dinoflagellates. This increase in fertility was likely triggered by a humid climate and enhanced continental input of clays and nutrients to surface oceanic waters. Calcareous nannofossils also proved to react to sea-level changes that occurred in the Valanginian, as inferred by previous works. Species likely inhabiting proximal areas were recorded in higher proportions during a major sea-level drop in the Peregrinus Ammonite Zone, Late Valanginian. The results of this study also permit to revise previously proposed paleoecological affinities of some nannofossil species. We suggest that Watznaueria barnesiae, one of the most-widely used species in the literature, should be used cautiously because of its high plasticity with respect to environmental conditions. Also, nannoconids that are usually regrouped in papers with paleoceanographic purposes should be analyzed separately because they show distinct species-specific ecological preferences.

Paleoclimate Change Through Valaginian Through Barremian Cretaceous France

Strontium-isotope stratigraphy of the Early Cretaceous (Valanginian–Barremian): Implications for Boreal–Tethys correlation and paleoclimate

Authors:

Mutterlose et al

Abstract:

The interpretation of past oceanographic events on a supra-regional scale requires precisely dated and well correlated biostratigraphic schemes. Only synchronous events can be interpreted in a global context. Events of local or regional character have therefore to be accurately correlated with time-equivalent shifts in other areas in order to be interpreted in a wider context. One of the problems of inter-basin correlation based on biostratigraphy lies in floral and faunal provincialism of the relevant index fossils. In order to overcome such limitations, chemostratigraphy can be used as a stratigraphic tool independent of biostratigraphy.

This study presents 87Sr/86Sr-isotope data for the Lower Cretaceous (Valanginian to Barremian) based on previously published findings from Speeton (northeast England) and the Vocontian Basin (southeast France). These belemnite-based 87Sr/86Sr-isotope data allow a correlation of the Lower Cretaceous sequences of the Boreal Realm and the Tethys independent of biostratigraphy. This chemostratigraphic approach may help to overcome the biostratigraphic problems which have been discussed for more than 40 years.

The two different 87Sr/86Sr-isotope curves modeled for the Boreal Realm and the Tethys show two offsets, asking for the following adjustments of the current correlation scheme. In the Boreal Realm, the base of the lower Hauterivian, currently defined by the first occurrence of the ammonite Endemoceras amblygonium, should be shifted into the Endemoceras amblygonium zone. The base of the upper Barremian, in the Boreal Realm defined by the first occurrence of the ammonite Paracrioceras elegans, correlates with the uppermost part of the Tethyan Kotetishvilla compressissima zone in the lower Barremian. To adjust for this mismatch a shift of the lower/upper Barremian boundary is necessary either in the Boreal Realm or in the Tethys.

The combined 87Sr/86Sr and δ18OBel isotope datasets suggest a synchronous negative δ18OBel shift for the middle Barremian. This shift, seen both in the Boreal and in the Tethys, indicates a major European wide phase of high humidity and increased run-off.

A Valanginian/Hauterivian Cretaceous Ichthyosaur Graveyard From Chile

A Lower Cretaceous ichthyosaur graveyard in deep marine slope channel deposits at Torres del Paine National Park, southern Chile

Authors:

Stinnesbeck et al

Abstract:

Remnants of ophthalmosaurid ichthyosaurs recently discovered in the vicinity of the Tyndall Glacier in the Torres del Paine National Park of southern Chile are extremely abundant and well preserved. After three field campaigns to the area, a total of 46 articulated and virtually complete ichthyosaur specimens, both adults and juveniles, were tentatively assigned to four different species of Ophthalmosauridae. Preservation is excellent and occasionally includes soft tissue and embryos. The skeletons are associated with ammonites, belemnites, inoceramid bivalves, and fishes as well as numerous plant remains. The enormous concentration of ichthyosaurs is unique for Chile and South America and places the Tyndall locality among the prime fossil Lagerstätten for Early Cretaceous marine reptiles worldwide.

The deposit is Early Cretaceous (Valanginian–Hauterivian) in age and forms part of a monotonous bathyal to abyssal sequence of the Late Jurassic to late Early Cretaceous Rocas Verdes back-arc basin. In this region, the Tyndall ichthyosaur population may have profited from cold upwelling currents that caused abundant life at the shelf edge including masses of belemnites and small fish, the preferred diet of ichthyosaurs. The abundance of almost completely articulated ichthyosaur skeletons in the Tyndall area suggests that some animals fell victim to episodic mass-mortality events caused by turbidity currents traveling downslope through a submarine canyon. They lost orientation, drowned, and were dragged into the deep sea by these turbulent high-energy gravity flows. Their bodies ended up in an oxygen-deficient basin environment where they were immediately embedded by the fine turbidite suspension fallout. The Tyndall ichthyosaur locality thus combines characteristics of both concentration and conservation Lagerstätten.

Cheirolepidiacean Foliage From Valangian-Albian Cretaceous Australia

Cheirolepidiacean foliage and pollen from Cretaceous high-latitudes of southeastern Australia

Authors:

Tosolini et al

Abstract:

Cheirolepidiaceae leaves and pollen are recorded from Valanginian–Albian strata of southeastern Australia that were deposited at high-latitudes under cool, moist climates in contrast to the semi-arid or coastal habitats preferred by many northern Gondwanan and Laurasian representatives of this group. Leaves of this family are characterized by thick cuticles and cyclocytic stomata with randomly oriented apertures, arranged in scattered or longitudinal rows or bands. Stomata are deeply sunken and surrounded by four to six subsidiary cells that bear one or two ranks of prominent overarching papillae, which may constrict the mouth of the pit. Three new taxa (Otwayia denticulata Tosolini, Cheirolepidiaceae cuticle sp. A and sp. B) are distinguished based on cuticular features, adding to several previously documented cheirolepid conifers in the Early Cretaceous of eastern Australia. Cheirolepidiaceae foliage is preserved predominantly in fluvial floodbasin settings and is interpreted to be derived from small trees occupying disturbed or low-nutrient sites. The foliage is associated with Classopollis/Corollina pollen and roots characterized by prominent mycorrhizal nodules. A Cenomanian Classopollis type recognised from Bathurst Island, Northern Australia, is recorded for the first time from the Early Cretaceous Eumeralla Formation, Otway Basin. Classopollis locally is rare in Valanginian–Barremian strata of Boola Boola, Gippsland, but constitutes up to 14% of the palynomorph assemblage in Albian strata. This indicates that the family was locally abundant in cool southern high-latitude climates of the Mesozoic, contrary to previous reports of its rarity in this region.

Pterosaur Landing Trace Fossils Found

I've seen in some of the news bits our own Dave Hone quoted. Quite kewl.

Anyone have a link to the paper?

Earliest Spider Web in Amber

The tiny tangled threads of the world's oldest spider web have been found encased in a prehistoric piece of amber, a British scientist said Monday.

Oxford University paleobiologist Martin Brasier said the 140-million-year-old webbing provides evidence that arachnids had been ensnaring their prey in silky nets since the dinosaur age. He also said the strands were linked to each other in the roughly circular pattern familiar to gardeners the world over.

"You can match the details of the spider's web with the spider's web in my garden," Brasier said.

The web was found in a small piece of amber picked up by an amateur fossil-hunter scouring the beaches on England's south coast about two years ago, Brasier said. A microscope revealed the existence of tiny threads about 1 millimeter (1/20th of an inch) long amid bits of burnt sap and fossilized vegetable matter.

While not as dramatic as a fully preserved net of spider silk, the minuscule strands show that spiders had been spinning circle-shaped webs well into prehistory, according to Simon Braddy, a University of Bristol paleobiologist uninvolved with the find.

"It's not a striking, perfect web," Braddy said. "(But) this seems to confirm that spiders were building orb webs back in the early Cretaceous" — the geological term for the period of time between 145.5 and 65.5 million years ago when dinosaurs and small mammals shared the earth.

140 MYA puts it on the Valanginian-Berriasian boundary more or less.