Micropaleontology

Nuevas investigaciones sobre los yacimientos paleolíticos de la Sierra Norte de la Comunidad de Madrid

by Fernando Colino

Realizado junto a P. de la Peña, P. Sevilla, G. Vega, S. Barez y F. Gutiérrez.

Durante los últimos años se han retomado las investigaciones en la Sierra Norte de la Comunidad de Madrid. Dichas... more Durante los últimos años se han retomado las investigaciones en la Sierra Norte de la Comunidad de Madrid. Dichas actuaciones partieron de una iniciativa de la Dirección General de Patrimonio Histórico de la CAM que tuvo como primer objetivo evaluar el potencial arqueológico pleistoceno de la orla caliza de la Sierra Norte a través de una campaña de prospecciones. Aquel primer trabajo dejó clara la importancia de la zona E de la orla, destacando el Cerro de la Dehesa de la Oliva (Patones) y el barranco del Arroyo del Monte (El Vellón). La línea de trabajo emprendida, con posterioridad, se ha centrado en el estudio específico de dos enclaves, dado el amplio potencial que presentaban: la Cueva del Reguerillo y el Abrigo del Monte. Por un lado, en la Cueva de El Reguerillo se ha realizado una estrategia de protección, documentación y evaluación de sus bienes a través de diversos trabajos como la prospección de arte rupestre y los sondeos arqueológicos en las diferentes entradas. Por otro, en el Abrigo del Monte se efectuó un sondeo arqueológico que ha dejado clara la importancia de este yacimiento para el Paleolítico Superior final del centro de la Península Ibérica.

Multiple early Eocene benthic foraminiferal assemblage and δ13C fluctuations at DSDP Site 401 (Bay of Biscay – NE Atlantic)

by Simon D'haenens

Within the last decade, several early Eocene hyperthermals have been detected globally. These transient warming events... more Within the last decade, several early Eocene hyperthermals have been detected globally. These transient warming events have mainly been characterized geochemically - using stable isotopes, carbonate content measurements or XRF core scanning - yet detailed micropaleontological records are sparse, limiting our understanding of the driving forces behind hyperthermals and of the contemporaneous paleoceanography. Here, detailed geochemical and quantitative benthic foraminiferal records are presented from lower Eocene pelagic sediments of Deep Sea Drilling Project Site 401 (Bay of Biscay, northeast Atlantic). In calcareous nannofossil zone NP11, several clay-enriched levels correspond to negative δ13C and δ18O bulk-rock excursions with amplitudes of up to ~ 0.75‰, suggesting that significant injections of 12 C-enriched greenhouse gases and small temperature rises took place. Coeval with several of these hyperthermal events, the benthic foraminiferal record reveals increased relative abundances of oligotrophic taxa (e.g. Nuttallides umbonifera) and a reduction in the abundance of buliminid species followed by an increase of opportunistic taxa (e.g. Globocassidulina subglobosa and Gyroidinoides spp.). These short-lived faunal perturbations are thought to be caused by reduced seasonality of productivity resulting in a decreased Corg flux to the seafloor. Moreover, the sedimentological record suggests that an enhanced influx of terrigenous material occurred during these events. Additionally, the most intense δ13C decline (here called level δ) gives rise to a small, yet pronounced long-term shift in the benthic foraminiferal composition at this site, possibly due to the reappraisal of upwelling and the intensification of bottom water currents. These observations imply that environmental changes during (smaller) hyperthermal events are also reflected in the composition of deep-sea benthic communities on both short (< 100 kyr) and longer time scales. We conclude that the faunal patterns of the hyperthermals observed at Site 401 strongly resemble those observed in other deep-sea early Paleogene hyperthermal deposits, suggesting that similar processeshave driven them.

El yacimiento paleolítico de Cerro Negro. Actuaciones geoarqueológicas y paleontológicas en las obras del Colector By-Passs de Abroñigales (Madrid)

by Mario Lopez Recio

Manzano, I.; Morín, J.; del Moral, B.; Alarcón, A.; Dapena, L.; García Martos, M.; López Recio, M.; Rolindes, A.; Berninches, P.; Tapias, F.; Simón, G., published in "Actas de las Terceras Jornadas de Patrimonio Arqueológico en la Comunidad de Madrid (Madrid, nov.-dic. 2006), 2009.

Indication of global deforestation at the Cretaceous-Tertiary boundary by New Zealand fern spike

by Vivi Vajda

Vajda, Raine & Hollis 2001
Science, 294, 5547: 1700-1702

The devastating effect on terrestrial plant communities of a bolide impact at the Cretaceous-Tertiary boundary is... more The devastating effect on terrestrial plant communities of a bolide impact at the Cretaceous-Tertiary boundary is shown in fossil pollen and spore assem-blages by a diverse flora being abruptly replaced by one dominated by a few species of fern. Well documented in North America, this fern spike signals
widespread deforestation due to an impact winter or massive wildfires. A Southern Hemisphere record of a fern spike, together with a large iridium anomaly, indicates that the devastation was truly global. Recovery of New Zealand plant communities followed a pattern consistent with major climatic perturbations occurring after an impact winter that was possibly preceded by
global wildfires.

Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid-Waipara River, North Canterbury, New Zealand

by Vivi Vajda

Vajda & Raine 2003

New Zealand Journal of Geology & Geophysics, 2003, 46: 255–273

Abstract Terrestrial pollen and spores in late Maastrichtian to early Paleocene marine strata at mid-Waipara, New... more Abstract Terrestrial pollen and spores in late Maastrichtian to early Paleocene marine strata at mid-Waipara, New Zealand, permit reconstruction of contemporary vegetation and paleoclimates. During the latest Cretaceous, spore-pollen assemblages reflect a temperate rainforest with a prominent
podocarp and tree ferns component, angiosperm pollen being mainly represented by Nothofagus and Proteaceae. Disruption of the vegetation at the Cretaceous/Tertiary (K/T) boundary is recorded by an increase in fern spores, reduction in gymnosperm pollen, and temporary loss of angiosperm pollen both in mid Waipara and in the terrestrial sections of Moody Creek Mine and Compressor Creek. Following an interval of fern dominance, gymnosperms and later angiosperms return to the palynological record. The floral turnover at the K/T boundary is comparable to palynological records from North America and Japan, indicating that disruption of vegetation was global. Fern dominance is estimated to have lasted several thousands of years, based on foraminiferal biostratigraphy of immediate post-K/T boundary strata. This is orders of magnitude greater than seen in normal seral successions following deforestation. We suggest that the observed vegetation succession is due to a prolonged period of low ambient light levels, sufficient for photosynthesis but favouring plants already adapted to these levels (such as forest ground stratum), accompanied by a moderate temperature and moisture regime.

Exceptionally preserved Late Albian (Cretaceous) Arcellaceans (Thecamoebians) from the Dakota Formation near Lincoln, Nebraska, USA

by Darren Gröcke

Thousands of exceptionally well-preserved Arcellaceans (Thecamoebians) have been recovered from a Late Albian... more Thousands of exceptionally well-preserved Arcellaceans (Thecamoebians) have been recovered from a Late Albian (Cretaceous) deposit. Sedimentary samples were obtained from a clayey-silt leaf bed in the Dakota Formation, outcropping in a clay pit excavated by the Yankee Hill Brick Company, located near Lincoln, Nebraska. Based on recovered freshwater macrophyte spore and fossil remains, the leaf bed is a lagerstätten of paleobotanical remains in which the paleoenvironment has been interpreted as a quiescent freshwater setting. The large number of recovered thecamoebians revealed a high intraspecific variability in test morphology that is comparable to Holocene thecamoebian populations. Consequently, we employ the thecamoebian strain taxonomic framework, a first for ancient thecamoebians. Extant species contained in this collection include Difflugia oblonga, Difflugia protaeiformis, Difflugia urens, Pontigulasia compressa, Lagenodifflugia vas, Cucurbitella tricuspis, Lesquereusia spiralis and the cysts of environmentally stressed protozoans—with only one new species reported, Difflugia baukalabastron. The well-preserved nature of the taxa, suggesting little taphonomic bias, and the lack of significant new species supports the current hypothesis of minimal evolution in thecamoebian lineages through geologic time.

Vertebrate microremains from the Lower Silurian of Siberia and Central Asia: palaeobiodiversity and palaeobiogeography

by Živilė ŽIGAITĖ

ŽIVILĖ ŽIGAITĖ,
VALENTINA KARATAJŪTĖ-TALIMAA,
and ALAIN BLIECK

Vertebrate microremains from the Lower Silurian of Siberia and Central Asia: palaeobiodiversity and palaeobiogeography
Journal of Micropalaeontology September 2011, v. 30:97-106; doi:10.1144/0262-821X11-016

Mesorbitolina (Cretaceous larger foraminifera) from the Yezo Group in Hokkaido, Japan and its stratigraphic and paleobiogeographic significance.

by Yasuhiro Iba

Iba, Y., Sano, S., 2006,
Mesorbitolina (Cretaceous larger foraminifera) from the Yezo Group in Hokkaido, Japan and its stratigraphic and paleobiogeographic significance.Proceedings of the Japan Academy, Series B 82, 216-223.

Hettangian to Sinemurian ostracod faunas from East Quantoxhead, West Somerset.

by Mark Hylton

Hart, M. B. and Hylton, M.D. 1999. Hettangian to Sinemurian ostracod faunas from East Quantoxhead,
West Somerset. Geoscience in South-West England, 9, 289-296.

The Hettangian to Sinemurian (Lower Jurassic) succession has been investigated for its ostracod fauna. The marine... more The Hettangian to Sinemurian (Lower Jurassic) succession has been investigated for its ostracod fauna. The marine assemblages from this
part of the Lower Jurassic succession are of low diversity, dominated by the genus Ogmoconcha Triebel, 1941. The stratigraphical
distribution of the known taxa, although distinctive, do not appear to provide a diagnostic tool for recognition of the base of the Sinemurian
Stage. The data generated by this work do, however, provide additional evidence that the East Quantoxhead succession is a suitable GSSP for
the base of the Sinemurian Stage.

Hettangian to Sinemurian (Lower Jurassic) sea-level change and palaeoenvironments: evidence from benthic foraminifera at East Quantoxhead, West Somerset, U.K.

by Mark Hylton

Hylton, M. D. 1999. Hettangian to Sinemurian (Lower Jurassic) sea-level change and palaeoenvironments:
evidence from benthic foraminifera at East Quantoxhead, West Somerset, U.K. Geoscience in south-west England, 9, 285-288.

The Hettangian to Sinemurian (Lower Jurassic) of the West Somerset coast, near East Quantoxhead, comprises an expanded... more The Hettangian to Sinemurian (Lower Jurassic) of the West Somerset coast, near East Quantoxhead, comprises an expanded fossiliferous
sequence of alternations of thickly laminated mudstones, more homogenous mudstones and limestones.
During Hettangian times a broad shallow marine shelf sea was established over most of Britain and north-west Europe, colonised by a low
(but gradually increasing) diversity foraminiferal fauna, related to the major transgressive pulse at the base of the Jurassic. Imposed upon this
general trend of sea-level rise, with major pulses in the early Hettangian and early Sinemurian, were episodic falls of sea-level. While there is
little facies evidence for a major sea-level drop around the end of the Hettangian at East Quantoxhead, it is notable that several index
foraminifera become extinct at or near the top of the Hettangian Angulata Zone which is interpreted as evidence for a minor regression.
Changes in foraminiferal assemblages from this Lower Jurassic section have been examined and are considered to be related to sea-level
changes where transgressions mark the arrival of new species and subspecies (evolutionary appearances and/or migration) whereas
regressions and times of lowered sea-level appear to equate to extinctions. Within these nodosariid-dominated foraminiferal populations,
major variations in species and generic abundances are seen in taxa which are long ranging, suggesting controlling palaeoenvironmental
factors. The predominance of the Lingulina tenera (Bornemann) plexus with associated Lenticulina and Marginulina species suggests inner
to near shelf environments with periods of normal oxygen levels.

A PRELIMINARY ANALYSIS OF THE FORAMINIFERA FROM THE HETTANGIAN - SINEMURIAN BOUNDARY OF EAST QUANTOXHEAD, WEST SOMERSET

by Mark Hylton

Read at the Annual Conference of the Ussher Society, January 1998

The coastline of West Somerset has long been recognised as containing a classic example of Lower Lias (Lower Jurassic)... more The coastline of West Somerset has long been recognised as containing a classic example of Lower Lias (Lower Jurassic) geology consisting
of alternating cycles of shale and limestone ('Blue Lias' facies). Recent investigations of the palynology, chemostratigraphy,
magnetostratigraphy and ammonite successions have been undertaken to characterise the candidate basal Sinemurian Stage stratotype in the
area around East Quantoxhead.
The present study has involved the preliminary investigation of the foraminifera across the Hettangian - Sinemurian boundary as part of the
assessment of the potential of the section as a Global Stratotype Section and Point (GSSP).
35 samples of mudstone and shale were studied for microfossils in the >74 bm size-fraction from a 30 m section across the boundary. Ten
samples proved fossiliferous with an abundant and diverse fauna of foraminifera.
The faunas are dominated by the Lingulina tenera Bornemann plexus group with associated nodosariids and a minor component of the
Frondicularia terquemi Bornemann plexus group. The absence of foraminifera in the remaining samples could be a result of diagenesis
associated with the formation of the limestones.

Microfaunal investigation of the Early Toarcian (Lower Jurassic) extinction event in N.W. Europe

by Mark Hylton

PhD Thesis - Full text is available to download at ethos.bl.uk

The Early Jurassic was a time of rapidly rising sea-level associated with the extensive
spread of anoxic bottom... more The Early Jurassic was a time of rapidly rising sea-level associated with the extensive
spread of anoxic bottom waters. Sea-level rise across the Pliensbachian - Toarcian
boundary culminated in the falciferum Zone of the Toarcian and is one of the best
authenticated eustatic events in the Jurassic. This major transgressive pulse was marked by
deepw ater marine sequencesa nd was associatedw ith the deposition of organic-rich shales.
The development of anoxia coincides with a notable period of mass extinction of the
marine fauna. High resolution sampling and study of the microfaunast hrough sequencesin
N. W. Europe confirm that benthic foraminiferal. faunas were similarly affected by an early
Toarcianfalciferum Zone event. Samples were analysed from Pliensbachian - Toarcian
mudstone,c lay and shale sequenceso f the south Dorset Coast,t he Midlands, the Yorkshire
Coast, southern France and southwest Germany. The sections studied show distinct
changes in assemblagesa cross the Pliensbachian - Toarcian boundary and in the basal
zones of the Toarcian.
Evidence for a foraminiferal extinction event in the Pliensbachian - Toarcian includes the
elimination of the important Lower Jurassic Lingulina tenera, Frondicularia terquem! and
Marginulina prima plexus groups, initiating a significant period of turnover of the
microfauna. The foraminiferal extinction event recorded in the Lower Toarcian sections of
north west Europe is only significant at species level. No extinctions at the family-level
occurred.
A marked changea lso occurred in the charactero f associatedn odosariid assemblagest:h e
uniserial forms of Nodosaria, Frondicularia and Lingulina, dominating the Pliensbachian
assemblagesw, ere largely replacedb y coiled Lenticulina in the early Toarcian. A reduction
in test size and a decline in species diversity, compared with Hettangian to Sinemurian
foraminiferal assemblagesr,e flect the developmento f low oxygen conditions followed by a
subsequenrte newal of the microfauna in the Middle Toarcian. The foraminiferal data show
no evidence of progressive displacement of older by younger faunas. Instead certain species
only expanded their populations and diversity significantly after the extinction of similar
niche-occupying species.
The Pliensbachian - Toarcian (Lower Jurassic) sediments of the north Yorkshire coast
contain highly organic-rich shales where the sequence stratigraphic significance is
somewhat obscure. Benthic foraminiferal species distribution (as a function of organic flux
and oxygenation) allowed palaeobathymetry to be determined on quantitative assemblage
characteristics.
In parallel with this methodology, a suite of trace elements (including Mn, Ca, Fe, and Al)
have been analysed following nitric and hydrofluoric acid digestion. Maxima of Ca and Mn
occur at the base of the falcifierum Subzone (falcifierum Zone). It is suggested that these
maxima are an artefact of condensation of carbonate fossiliferous material due to sediment
starvation and correspond to published estimates of a maximum flooding surface.
Interpretations of the benthic foraminiferal assemblages surrounding this event provide
further support for a transgressive event -associated with the development of low oxygen
conditions and the deposition of organic-rich shales.
Additional Lower Jurassic,H ettangiant o lower Pliensbachian,s equencesw ere investigated
for the purposes of establishing their foraminiferal correlation potential as candidate Global
Stratotype Sections and Points for the basal Sinemurian and basal Pliensbachian.

The Global Boundary Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (Lower Jurassic), Wine Haven, Yorkshire, UK

by Mark Hylton

The search for the origin of the planktic Foraminifera

by Mark Hylton

Planktic Foraminifera are an extremely abundant, important and successful group of marine protists. They are... more Planktic Foraminifera are an extremely abundant, important and successful group of marine protists. They are particularly useful in reconstructing past environments and for biostratigraphic dating. Despite their importance, the origin of the group is uncertain. Previous work has suggested that they evolved from a benthic ancestor during the Triassic or, perhaps, the Mid-Jurassic (?Bajocian), but a reason for their origination has remained unclear. Here, we present evidence from the Toarcian (early Jurassic) of NW Europe that the origin of the planktic Foraminifera may have been one of the results of the early Toarcian oceanic anoxic event. This event appears to have been associated with a massive dissociation of gas hydrates and other, perhaps related, water chemistry changes.

Orbitolinid foraminifers in the Northwest Pacific: Their taxonomy and stratigraphy

by Yasuhiro Iba

Iba, Y., Sano, S., Miura, T., 2011 (uncorrected proof)
Orbitolinid foraminifers in the Northwest Pacific: Their taxonomy and stratigraphy. Micropaleontology, vol. 57, p. 167-171

Orbitolinid foraminifers supply important information for the understanding of Cretaceous marine biogeographic and... more Orbitolinid foraminifers supply important information for the understanding of Cretaceous marine biogeographic and paleoclimatic conditions. A pre-requisite for these palaeoenviromental interpretations is a sound taxonomy. The taxonomy of the orbitolinoids from the Northwest Pacific has been controversial, and this paper aims at a taxonomic and stratigraphic revision of this group. Four orbitolinid species (Eopalorbitolina transiens, Praeorbitolina cf. wienandsi, Orbitolina (Mesorbitolina.) parva, and O. (M.) texana) have been recognized. Orbitolinids occurred almost continuously from the Late Hauterivian to the late Early Albian. Species belonging to the Praeorbitolina cormyi–Orbitolina (Mesorbitolina) aperta evolutionary lineage are most common, while dictyoconids are missing in the Northwest Pacific. Following the last occurrence of O. (M.) parva in the Douvilleiceras mammilatum zone of the Early Albian, no orbitolinids have been recognized in the Northwest Pacific. It is possible that provincialism in orbitolinid foraminifers occurred during the Early Cretaceous of the North Pacific.

Biodiversity and Endemism of the Silurian Vertebrates In the Siberian Palaeocraton

by Živilė ŽIGAITĖ

New Genus of Chondrichthyans From the Silurian-–Devonian Boundary Deposits of Tuva (Russia)

by Živilė ŽIGAITĖ

Palaeobiogeographical Significance of Early Silurian Thelodonts From Central Asia and Southern Siberia

by Živilė ŽIGAITĖ

Seasonal to Interannual Variability and Geographic Distribution of the Silicoflagellate Fluxes In the Western Mediterranean

by Iván Hernández-Almeida

Andrés S. Rigual-Hernández, María A. Bárcena, Francisco J. Sierro, José A. Flores, Iván Hernández-Almeida, Anna Sanchez-Vidal, Albert Palanques, Serge Heussner. Volume 77, Issues 1-2, October 2010, Pages 46-57 , Marine Micropaleontology

A total of 337 samples collected from five sediment traps located in the Gulf of Lions, Catalan margin and the Alboran... more A total of 337 samples collected from five sediment traps located in the Gulf of Lions, Catalan margin and the Alboran Sea have been analyzed in order to study the seasonal, interannual and geographical distributions of silicoflagellate fluxes in the Western Mediterranean. As a general trend, maximum fluxes of silicoflagellate skeletons always occurred during the spring bloom; i.e. during the winter–spring transition, while minimum fluxes were recorded during summer, characterised by a strong stratification and oligotrophic conditions. However, the sediment trap record of the Catalan margin did not exhibit any clear seasonal signal, probably owing to the fertilizing effect of the rivers Llobregat and Besos. Regarding interannual variability, no clear relationship between the NAO (North Atlantic Oscillation) and the silicoflagellate fluxes was found. In contrast, the silicoflagellate assemblages from the Alboran Sea and the Gulf of Lions responded with low fluxes and a delay in their annual maximum to the anomalous conditions elicited by the 1997–98 El Niño Event. Furthermore, the 2003 summer heat wave over the Western Mediterranean had similar repercussions on the silicoflagellate spring maximum 2004 in the Gulf of Lions. Three silicoflagellate species were identified in the samples, following the taxonomic concepts of Throndsen (1997): Dictyocha fibula (Ehrenberg), Dictyocha speculum (Ehrenberg) and Octactis octonaria (Ehrenberg) Hovasse 1946. D. fibula was cosmopolitan and the dominant species at all sites, always accounting for more than 80%. Moreover, its maximum fluxes were recorded in those sampling sites which were under the influence of high nutrient concentrations caused by the river input. D. speculum was only recorded in the northern locations, which suggests an affinity for colder water masses. In contrast, O. octonaria was restricted to the Alboran Sea stations, where temperatures reached the highest values and nutrients were scarcer.

Microplankton response to environmental conditions in the Alboran Sea (Western Mediterranean): One year sediment trap record

by Iván Hernández-Almeida

I. Hernández-Almeida, M.A. Bárcena, J.A. Flores, F.J. Sierro, A. Sanchez-Vidal & A. Calafat.Volume 78, Issues 1-2, January 2011, Pages 14-24. Marine Micropaleontology

The present work analyses the seasonal evolution of planktonic assemblages and particle fluxes through the water... more The present work analyses the seasonal evolution of planktonic assemblages and particle fluxes through the water column in the Eastern Alboran Sea (Western Mediterranean) at 35º55.47’N/01º30.77’W. A Sediment trap was deployed below the influence of the Almeria-Oran Front (AOF), a semi-permanent geostrophic front, during July 1997 to June 1998. Overall, the temporal variability of coccolithophore, planktonic foraminifer, diatom, benthic and wind-carried biogenic particle fluxes are linked to the seasonal evolution of sea surface hydrological structures. Maximum planktonic fluxes were found during high-productivity periods and wind-induced upwelling, following a trimodal pattern, with maximum fluxes in July 1997, November-December 1997, and April-May 1998. These periods were characterized by vertical mixing and the full development of anticyclonic gyres in the Alboran Sea. The annual flux of coccolithophores was dominated by the “small Gephyrocapsa Group” and Emiliania huxleyi <4m, whereas Turborotalita quinqueloba and Globigerina bulloides dominated the foraminiferal fluxes, and Chaetoceros Resting Spores (RS) were predominant in the diatom assemblage. Benthic specimens were also collected with the sediment trap, suggesting a variable influence of bottom water activity. Wind-driven particles (phytoliths and fresh-water diatoms) were collected along the year, but their fluxes followed the local wind regime.
The high Sea Surface Temperature (SST) during fall due to weaker than usual westerly winds, and the pressure anomaly prevaling in the Alboran Sea during early winter, were reflected in the planktonic assemblages by the proliferation of warm, lower photic layer inhabitants and/or oligotrophic taxa of coccolithophores (Florisphaera profunda), planktonic foraminifers (Globigerinoides ruber and Globorotalia inflata) and diatoms (Leptocylindrus danicus). These unusual climatic conditions in the eastern Alboran Sea must have been caused by the 1997-1998 ENSO event.