Gelasian Stage Research Articles

Calcareous Nannofossil variability controlled by Milankovitch and sub-Milankovitch periodicity in the Monte San Nicola section (Gelasian GSSP / MIS 100–104)

The Quaternary marks the beginning of the ice ages, with the establishment of a stable Northern Hemisphere ice sheet. The Monte San Nicola section, southern Sicily (Italy) is the Global Boundary Stratotype Section and Point of the Gelasian Stage of the Lower Quaternary Subseries and is attracting new attention for providing valuable information on paleoclimate evolution.Here we present a paleoenvironmental reconstruction based on new data from calcareous nannoplankton, the phytoplankton organisms that are sensitive to sea surface changes and water column dynamics. We adopt statistical and signal analysis to support our paleoenvironmental model. The most evident paleoenvironmental signal throughout the investigated interval is the contrast between the abundance patterns of placoliths and Florisphaera profunda, the former pointing to surface productivity (water column mixing, shallow nutricline), the latter to the establishment of a deep nutricline. The observed nutricline depth shift occurred with a regular precessional pace, following Northern Hemisphere summer insolation and, likely, North African monsoon activity. A significant periodicity of 8 kyr, in tune with late Quaternary Heinrich events, is also observed in nannoplankton taxa, supporting previous findings on the existence of suborbital climatic variability even at the Pliocene-Pleistocene transition.

Morphological Characterization of Fossil Vitis L. Seeds from the Gelasian of Italy by Seed Image Analysis.

The discovery of well-preserved fossil Vitis L. seeds from the Gelasian stage in Italy has provided a unique opportunity to investigate the systematics of fossilized Vitis species. Through seed image analyses and elliptical Fourier transforms of fossil Vitis seeds from the sites Buronzo-Gifflenga and Castelletto Cervo II, we pointed out a strong relationship to the group of extant Eurasian Vitis species. However, classification analyses highlighted challenges in accurately assigning the fossil grape seeds to specific modern species. Morphological comparisons with modern Vitis species revealed striking similarities between the fossil seeds and V. vinifera subsp. sylvestris, as well as several other wild species from Asia. This close morphological resemblance suggests the existence of a population of V. vinifera sensu lato in Northen Italy during the Gelasian. These findings contributed to our understanding of the evolution and the complex interplay between ancient and modern Vitis species.

High-resolution climate variability across the Piacenzian/Gelasian boundary at land-based marine sequences of Monte San Nicola (Sicily, Mediterranean)

The Piacenzian – Gelasian transition is a time of profound changes in the Earth's climatic regime, epitomized by the definitive establishment of large ice caps in the Northern Hemisphere and the beginning of the “ice ages” at ca. 2.6 Ma. This event is sharply documented in δ18O records globally by a prominent triplet of severe glacial events (MIS 100, 98 and 96) that approximate the base of the Gelasian Stage. We have reconstructed a multi-species planktic and benthic foraminiferal δ18O and δ13C record from the Monte San Nicola section (Sicily) across the Piacenzian/Gelasian boundary, with the purpose of better constraining in time the main marker criteria for recognition of the Gelasian GSSP (Global Boundary Stratotype Section and Point) and investigating in detail the paleoclimatic and paleoceanographic response of the central Mediterranean to the definitive onset of the Northern Hemisphere Glaciation. Our results confirm the reliability and usability of the criteria originally proposed for defining the Gelasian GSSP, and significantly improve their chronology and chronostratigraphic positioning. Beyond an obvious alternation of obliquity-driven glacial-interglacial cycles, our isotopic record unraveled a pervasive climate variability in the suborbital time domain, the origin of which is still ambiguous. Altogether data presented in this paper provide the first high resolution isotopic records shedding new light both on the stratigraphic and paleoclimatic evolution of the Central Mediterranean area at the beginning of the Northern Hemisphere Glaciation.

Climate-induced surface water variability at Monte San Nicola type-section (Sicily, southern Italy): New data across the Gelasian GSSP

We present the first high-resolution results on planktonic foraminiferal stable oxygen isotopes and calcareous plankton assemblages at the Monte San Nicola GSSP section (near Gela, Sicily), the type-section for the Lower Pleistocene Gelasian Stage. The oxygen isotope profile is remarkably similar to the Eastern Mediterranean oxygen isotope record and indicates that the studied section, extending from marine isotope stage (MIS) G4 to MIS 103, clearly records glacial-interglacial variability. Cyclic changes of calcareous plankton assemblages (calcareous nannofossils and foraminifera) indicate that warmer and stratified surface waters occurred during interglacials, while cooler and unstable conditions developed during glacial phases. Signatures of further increase in surface water stratification are also captured by our surface water proxies and are coeval with enhanced monsoon run-off, developed during precession minima/insolation maxima. The surface water changes recorded at the Monte San Nicola section are in phase with North Atlantic climate variability, even at suborbital scale, and reveal evidence of the first significant southward migration of the Subarctic Front in the mid-latitudes during MIS 104, slightly below the GSSP. The overall dataset provides precise alignment of the Gelasian GSSP within MIS 103 as well as new climatostratigraphic constraints, close to the GSSP, thus improving its correlation potential outside the type-area.

The Neogene–Quaternary boundary at its type locality, Monte San Nicola, Sicily, southern Italy: X-ray computed tomography and ichnofabric signals of the sapropelic Nicola bed

A new low-cost method is described for obtaining narrow blocks of the friable Nicola bed, the local marker for the Neogene–Quaternary system (Pliocene–Pleistocene series) boundary at the type section at Monte San Nicola, southern Sicily. The Global boundary Stratotype Section and Point (GSSP), which also defines the Gelasian Stage and is dated at 2.58 Ma, is placed at the base of a marly layer immediately overlying the sapropelic microlaminated Nicola bed. Sedimentary structures and ichnofabrics revealed by X-ray computed tomography (CT) and polished surface observations show the rapid onset of anoxia marking the base of the Nicola bed, followed by progressive dysoxia indicated by the trace fossil Chondrites isp. alone. The top of the Nicola bed is bioturbated over an interval of several centimeters, which obscures precise recognition of the GSSP horizon. The overlying marl is characterised by the presence of Chondrites isp. accompanied by Planolites isp. and Thalassinoides isp. indicating a return to higher oxygen levels in the bottom waters, although a brief return to poor oxygenation is interpreted from the temporary absence/rarity of Chondrites isp. Trichichnus isp. is prevalent throughout the interval immediately above the Nicola bed, and its lowest extent revealed by CT may serve at least locally as an independent marker for the GSSP level. In general, we recommend the careful study of any sapropel before placing a GSSP at its upper or lower boundary or midpoint.

Chronological context, species occurrence, and environmental remarks on the Gelasian site Pedrera del Corral d’en Bruach (Barcelona, Spain) based on the small-mammal associations

ABSTRACT Here we present the results of a study of the small mammal assemblage recovered from a now disappeared karstic fissure located in a quarry called ‘Pedrera del Corral d’en Bruach’. The site was located at 330 m a.s.l. in the Garraf Massif, ca. 20 km south of Barcelona. An archaeological rescue excavation was conducted in 2006 by the Grup de Recerca del Quaternari, focusing on sieving the sediments that had accumulated at the foot of the quarry face. Fortunately, some faunal remains and sediment were recovered, which were later processed and sorted. Two hundred and seventy small mammal remains were identified at genus or species level, bringing to light 15 taxa. The assemblage is typical of the Mammal Neogene 17 (MN17) biozone, placing this site in the Gelasian stage of the Early Pleistocene. It is noteworthy that the first record of the glirid Glirulus pusillus in Iberia is documented. Based on the small mammals identified, the surrounding environment of the Garraf Massif is judged to have been characterised by open forest landscape and more humid environmental conditions than nowadays. Finally, the site provides a remarkable contribution to what is known of the Iberian small mammals of this time period.

The Monte San Nicola section (Sicily) revisited: A potential unit-stratotype of the Gelasian Stage

The Monte San Nicola area (Southern Sicily) offers a spectacular exposure of open-marine sediments that were employed in 1998 for defining the Global Stratotype Section and Point (GSSP) of the Gelasian Stage (Upper Pliocene). After the lowering of the Pliocene/Pleistocene boundary to ca. 2.6 Ma in 2010, the Gelasian GSSP has been redefined as the base of both the Pleistocene Series and the Quaternary Period, which increased its importance and visibility within the scientific community. However, documentation on the Monte San Nicola reference section is still sparse. In the light of its renewed status, we decided to undertake a complete revision of the Gelasian Stage in its type area, in order to evaluate whether the succession of bio- and magnetostratigraphic events that are expected to occur in the interval of relevance are represented adequately in the local record. The results of our investigation demonstrate that the Monte San Nicola succession spans continuously from the upper Piacenzian to the lower Calabrian, and is therefore suitable to host the Unit Stratotype, or even the Astronomical Unit Stratotype, of the Gelasian Stage.

Lower–Middle Pleistocene Stratigraphy of the Southern West Siberian Plain: New Data

Abstract—The Quaternary stratigraphy of the southern West Siberian Plain is considered in the context of the updated International Chronostratigraphic Scale, with the Neogene/Quarternary boundary at 2.588 Ma. New geological, lithological, paleontological, and paleomagnetic data from a reference Quaternary section in the Irtysh River valley near Isakovka Village provide more rigorous constraints on the Lower–Middle Pleistocene stratigraphy and the respective deposition conditions. The Isakovka outcrop exposes two stratigraphically expressed and paleontologically characterized units that were deposited during regional Pleistocene interglacial events of different ages: the Strunino and Serebryanoe alluvium beds lying over eroded surfaces. The species of the Corbicula genus coexisting with numerous species of Palearctic molluscs, small mammals Allophaiomys deucalion, Mimomys reidi, and last rooted lagurids Borsodia found in the Strunino alluvium are known also from continental equivalents of the warm upper Gelasian Stage in different parts of northern Eurasia. Judging by the presence of extant corbicules, the Strunino alluvium was deposited in a warm climate, with a mean annual air temperature above +16 °C and a mean winter temperature no colder than –8 °C, in rivers that remained free from ice all year round. On the basis of fauna constraints for the Serebryanoe alluvium, along with the first appearance of the European Pisidium clessini molluscs in West Siberia, the unit can be correlated with one of the earliest Middle Pleistocene interglacial events. The faunal assemblages and spore-pollen patterns of the two units indicate that the climate during the Serebryanoe deposition was slightly cooler and wetter than during the Strunino deposition, though steppe landscapes predominated on watersheds in both events. The two alluvial beds, which are traceable in river bluffs, at 30 m above the modern water level in a tectonically stable part of West Siberia, mark the hypsometrically higher position of the river network during the Early Pleistocene and early Middle Pleistocene interglacials.

Quaternary Tectonics as the Neotectonics in Turkey

The base of the Quaternary was formally redefined in 2009 by the International Commision on Stratigraphy at 2.6 Ma by shifting a 800 ka, formerly part of the Pliocene epoch, into the Pleistocene. It has made tremendous impression in literature. The Quaternary period is unique because of its climatic characteristics; however, it is a geochronological unit, and a redefinition of its position would affect many areas, such as the definition of neotectonic period in Turkey. The major tectonic elements of the Eastern Mediterranean region are located in there. Recent studies related to neotectonics in Turkey present a consensus on the driving mechanism and age of this tectonic period: the late Pliocene (before the formal adding of Gelasian stage into the Quaternary period) westward escape of the Anatolian plate. Following the collision of the Arabian and Eurasian plates at ~11 Ma BP, the North Anatolian Fault Zone created in the east and the escape tectonics could not occur until the propagation of the North Anatolian Fault Zone to the Aegean Arc at ~2.5 Ma BP and gaining a transform fault character with a similar slip rate as in today. The spatial distribution of active faults in Turkey also supports such an approach. The great majority of them have no relations with the pre-Quaternary formations, on the other hand are bounding the Quaternary basins. In this study, the neotectonics of Turkey discussed within the view of the redefined Quaternary. The comparison suggests the using of the term Quaternary tectonics substantially coincides with neotectonics in literature for Turkey, because the base level of this period in this region overlaps with the redefined base level of the Quaternary period.

Environmental changes in the eastern Arctic 1.6975-1.965 Ma, palynological investigations from El’gygytgyn Lake, northeastern Russia

The 1.6975–1.965 Ma (MIS 60–MIS 74) portion of the El'gygytgyn Lake record includes two key chronostratigraphic markers in the Calabrian–Gelasian boundary (1.806 Ma) and the Olduvai paleomagnetic excursion (1.77–1.95 Ma). It also provides the first paleovegetation information for these times from the eastern Arctic. Palynological data indicate the dominance of Larix forest and forest-tundra during warm and cool intervals, which differs sharply from the herb tundra which characterized glacial intervals of the Middle and Late Pleistocene. These forests likely included tree species of Betula and Alnus and perhaps Populus and Chosenia. The persistence of Larix indicates summer temperatures were warmer than present. Pinus pumila, a typical interglacial taxon, is restricted to MIS 65 and MIS 71, suggesting other intervals experienced dry winters. Cool and warm periods are clearly marked by vegetation changes during the Late Gelasian Stage, but a dominance of Poaceae pollen and reduction in Alnus pollen during the Early Calabrian Stage mutes the climatic fluctuations. The loss of Alnus perhaps relates to decreases in seasonal temperatures.

Early Pleistocene divergence ofPelagia noctilucapopulations (Cnidaria, Medusozoa) between the Atlantic Ocean and the Mediterranean Sea

AbstractA previous study detected mixing of two deeply split mtDNA clades (Clade I and Clade II) for Atlantic and Mediterranean populations of the medusozoanPelagia noctiluca. The north hemisphere glaciations and the Messinian salinity crisis have been proposed as the two main biogeographic events related to the isolation between the Atlantic Ocean and the Mediterranean Sea. We tested if the splitting time between Clade I and Clade II ofP. noctilucawas associated with one of these geological events. Our study was based on DNA sequence data of mitochondrial (COI and 16S ribosomal RNA) and nuclear (18S ribosomal RNA, internal transcribed spacer 1 and 5.8S ribosomal RNA) genes from populations of the Atlantic and Pacific Ocean and the Mediterranean Sea. The rise of the Isthmus of Panama was used to calibrate substitution rates for COI. This calibration was based on the detection of a shallow but significant genetic structure betweenP. noctilucapopulations from the Pacific and the Atlantic Oceans. Considering our calibration for COI, we refute a possible origin of Clades I and II during the Messinian salinity crisis. Our estimates suggest the origin for a putative common ancestor of Clades I and II around 2.57 Ma (with 95% 2.91–2.22 HPD), roughly corresponding to the Gelasian stage of the early Pleistocene. These alterations include changes in the sea level and oceanic currents at the Strait of Gibraltar and other regions of the Mediterranean basin, and could explain the origin of the twoP. noctilucaclades.

On the lower boundary of the Quaternary System in the Azov-Black Sea Basin

The data on the lowering of the lower boundary of the Quaternary System below the Gelasian Stage at 2.588 million years are presented in the paper. In Azov-Black Sea basin this boundary takes place within the middle of the Kuyalnikian Regionalstage and related to the magnetostratigraphic boundary Gauss-Matuyama and should be drawn under the deposits of the upper Kuyalnikian regionalsubstage, Taman layers of the Akchagylian, alluvium X terrace of the Dnister, Danuba, Prut rivers, the Haprovian layers of the Priazovie and under sediments of the Siverian stage in the loess-soil series of the Ukraine.Below there lie the deposits of the Bogdanivkian stage and the lower Kuyalnikian rocks. The deposits of the Lowerkuyalnikian regionalsubstage, upper and lower Poratian beds and sediments of the Bogdanivkian, Kizlyarkian and Jarkian stage in the loess-soil series related to Piacencian stage and Upper Pliocene. Kuyalnikian deposits in the Odessa (Kryzhanivka) region are the upper part of the Upperkuyalnikian regionalsubstage, above the Tamanian beds and correlations with a Beregovian stage in the loess-soil series. Beginning of the maximum Akchagylian transgression in the Black Sea coincides with a sharp cooling Climate period (2,5-2,6 million years) and compares with the Middle Akchagylian transgression of the Caspian basin. Signs of the late Akchagylian mollusks at the basal beds of the Kuyalnikian of the Priazovie requires additional research, as at that time the formation of the lower Poratian depositstook place in a (with Rugunio lenticularis) Warm climate. The most probable version is the invasion of Akchagylian mollusks during the cocking in Ajdarian time. The author opinion on the reasoning of the lowering of the boundary and the problems of its use in geological mapping are also stated.

Changes in the Landscape and Climate of Eastern Europe in the Early Pleistocene

In the context of shifting the boundary of the Quaternary down to the level of 2.6 Ma and including the Gelasian Stage in the Quaternary System, the systematization of the original and published data on the geology and paleogeography of the Late Pliocene and Early Pleistocene of Eastern Europe has been carried out. It was established that, at the boundary of the Gauss and Matuyama paleomagnetic epochs, along with the general trend toward cooling and aridization, profound landscape and climate changes occurred and rhythmic fluctuations of the climate intensified. During the period from 2.6 to 1.8 Ma, corresponding to the Gelasian (pre-Tiglian and Tiglian of Western Europe or Paleopleistocene of Eastern Europe), there appeared subarctic landscapes. In the Eopleistocene (1.8–0.78 Ma) and the Early Neopleistocene (0.78–0.42 Ma), the climate became colder, and climatic zonality repeatedly underwent a complex restructuring, gradually approaching the modern one. Glacial deposits (layers of till) occurring in Eastern Europe date back to the Paleopleistocene. Evidence indicates that there were at least three independent glaciations in the Eopleistocene (1.8–0.78 Ma) and possibly four in the Early Neopleistocene. On the basis of studies of stratotypic sections, paragenetic links were established between sediments of different age within glacial and periglacial areas, and the paleogeographic events of the Early Pleistocene of Eastern Europe were correlated with those within the Western European region.

Landscape and climat changes in Eastern Europe in the early Pleistocene

The systematization of the original and published data on the geology and paleogeography of the Late Pliocene and Early Pleistocene of Eastern Europe was carried out due to the lowering of the Quaternary lower boundary to the level of 2.6 million years ago and the inclusion of the Gelasian stage in Quaternary system. It was revealed that at the bound of the Gauss-Matuyama paleomagnetic epochs, the profound landscape and climate changes took place. The rhythmic fluctuations of the climate intensified against the background of the general trend towards cooling and aridization. Subarctic landscapes appeared during the period from 2.6 to 1.8 Ma, which corresponds to the Gelasian stage (the Praetiglian and Tiglian stages of Western Europe or the Paleopleistocene of Eastern Europe). In the Eopleistocene (1.8–0.78 Ma) and Early Neopleistocene (0.78–0.42 Ma), the climate became colder while the structure of natural zonality repeatedly underwent a complex restructuring and gradually approached to the modern one. The presence of glacial deposits was noted in Eastern Europe already in the Paleopleistocene. The traces of at least three independent glaciations were revealed in the Eopleistocene, and four glaciations were suggested for the Early Neopleistocene. Based on the data from stratotype sections, paragenetic relations between heterochronous sediments in glacial and periglacial areas were established and Early Pleistocene paleogeographic events in Eastern and Western Europe were correlated.

Biostratigraphy of the Early Pleistocene (Palaeopleistocene) deposits of the Southern Fore-Urals, Russia

A summary of published and unpublished data on the stratigraphy of the Early Pleistocene (Palaeopleistocene) of the Southern Urals region is presented in this paper. The summary follows previous reviews about the characteristics of the Pleistocene deposits of the easternmost part of Europe. The improvement and unification of the Regional Quaternary stratigraphical scheme was the main aim of these investigations. Deposits of different origin, which constitute the regional stratigraphical units (Zilim-Vasilyevo, Akkulaevo and Voevodskoe), are characterized. Malacological data form the base for the biostratigraphical subdivision. At the beginning of the Early Pleistocene, an ingression of the Akchagyl Sea (modern Caspian Sea area) began in the Zilim-Vasilyevo time, which developed as much as possible during Akkulaevo time, and then shortly re-emerged after regression into the territory of the Southern Fore-Urals during Voevodskoe time. During the Early Pleistocene (Palaeopleistocene), the Southern Fore-Urals region was characterized by continental climate conditions, which were influences by the wideapreaded brackish-water gulf of the Akchagyl Sea. Fossil molluscs, ostracods, mammals and pollen are used for the reconstruction of the palaeoenvironmental conditions and the biostratigraphical position of the main localities. The units have been correlated with the Gelasian stage of the Western European stratigraphical timescale.

Position of the base of the Quaternary in West Siberia (based on paleobotanical and paleomagnetic evidence)

This study reviews a possible new position of the base of the Quaternary in West Siberia based on paleobotanical and paleomagnetic data in view of ratification of ICS recommendations by the IUGS Executive Committee and the decision of the Interdepartmental Commission on the Quaternary Stratigraphy of Russia to lower the base of the Quaternary (and, therefore, the base of the Pleistocene) at 2.58 Ma. The paleobotanical and paleomagnetic data from two horizons on the West Siberian plain (Kulunda, attributed in part to the formerly Neogene Gelasian Stage, and Kochki, attributed to the Quaternary) were used to identify global cooling that occurred synchronously with a regional cooling phase determined at the base of the Gelasian at Monte San Nicola, Italy.

Geographical conditions and evolution of vegetation cover of Middle Volga Region in the pliocene

The development of flora on the territory of the Middle Volga region during the Pliocene is discussed. An attempt to reconstruct geographic conditions and vegetation cover is taken. A short description of the natural environment and landscape, of the vegetation cover of the Middle Volga and adjacent territories is done. The comparative scheme of the total and the regional scales of Pliocene is added. In the given paper one assumes the upper boundary of the Pliocene to be the upper boundary of the Gelasian Stage. The Pliocene is rather turbulent geological period during there was a relatively quick change of warm and cold phases, each of which is characterized by landscape and climate change. Landscape transformations took place against a background of progressive climate cooling with an increase in the contrast of summer and winter temperatures. Main geomorphological structures of the Middle Volga region, such as the Volga Upland, Samara Bend, Zhiguli Mountains, Obshhij Syrt, river network, appeared prior or during this period. Main plant formations in their broadest sense (taiga, broad-leaved and small-leaved forests, steppes) had already been formed by the beginning of the Pliocene. During the Pliocene period the depletion of those plant formations took place. It occurred due to the gradual extinction of thermophilic species and bringing in their composition to modern formations. Most of the species had taken modern form by the end of the Pliocene.

Gelasian stage and expected stratigraphical units having similar ages in Viet Nam

During recent years (2009-2013), International Commission on Stratigraphy (ICS) has published International Chronostratigraphic Charts with the increasing trend on the quantity of Quaternary. The lower part of Quaternary has supplemented the stage of Gelasian leading to the increasing time of Quaternary from 1,6 - 1,8 million years to 2,588 million years. In Viet Nam, geologists are currently using the time from 1,6 - 1,8 million years to present for Quaternary.In order to integrate into the international geological community, Quaternary in Viet Nam needed to be studied and added more stratigraphical units with the ages of Pliocene to fit the time of 2,588 million years. In this paper, we propose two related scientific idioms:- Exclude the upper Pleistocen of Ha Noi formation of Ha Noi depression, Ba Mieu formation (Nam Can) of Cuu Long river plain, Thach Han formation (Vo Dac) of Central of Viet Nam.In addition, detailed studies on paleontology, sedimentary, paleomagnetic, absolute age, stratigraphical events…needed to be continuously invested for implementation in the future.ReferencesIUGS ratified ICS Recommendation on redefinition of Pleistocene and formal definition of base of Quaternary, June 30th 2009. (Source: www.stratigraphy.org). Tống Dzuy Thanh và Vũ Khúc (chủ biên), 2005. Các phân vị địa tầng Việt Nam. Nhà xuất bản Đại học Quốc gia Hà Nội, 553tr. Nguyễn Địch Dỹ, 1987. Địa tầng và cổ địa lý trầm tích Kainozoi Việt Nam. Luận án Tiến sĩ Khoa học, tiếng Nga, 380tr.

Mediterranean Quaternary interglacial molluscan assemblages: Palaeobiogeographical and palaeoceanographical responses to climate change

The analysis of several central to eastern Mediterranean shallow-water deposits, mostly related to Posidonia oceanica palaeocommunities, sheds light on the presence of thermophilic molluscan assemblages throughout the Mediterranean Pleistocene. The taxonomic composition of these assemblages is totally different from that of the well-known Senegalese molluscan fauna and they play an important role in understanding some of the hydroclimatic conditions during Quaternary interglacial episodes in the central-eastern Mediterranean basin. Two of these assemblages from the Kyllini–Trypiti sequence (NW Peloponnesus) can be referred to the Upper Pleistocene interglacial marine isotope (sub)stage (MIS) 5e and 5a, on the basis of U/Th dating of corals (Cladocora coespitosa). Other assemblages belong to Lower Pleistocene (mainly Emilian substage, possible MIS 37), late Lower (Sicilian substages)–early Middle Pleistocene and late Middle–Upper Pleistocene (MIS 7 and MIS 5e). As a whole, these assemblages consist of 15 species of palaeoclimatic and stratigraphic value. Among these, Craspedochiton altavillensis (Polyplacophora), Jujubinus? bullula, Ersilia aliceae, Haedropleura bucciniformis, Strioterebrum basteroti (Gastropoda), and Plicatula mytilina (Bivalvia) are (Euro)Mediterranean strictly endemic extinct species, whereas Rissoina decussata, Niso terebellum, Kyllinia parentalis, Strioterebrum grayi, Terebra corrugata, Terebra reticularis (Gastropoda), Anadara sp., Chama placentina, and Corbula revoluta (Bivalvia) can be regarded as closely related to recent tropical West African taxa or as species living in tropical waters. The latter stock is useful for reconstructing palaeoclimatic conditions, suggesting winter sea surface temperatures 4–6°C and 2–4°C warmer than today in western Sicily and the easternmost part of the Mediterranean Sea, respectively. In contrast with Pleistocene glacial settings, detected warm episodes are characterized by a lower degree of seasonality, with a difference between summer and winter sea surface temperatures of 6–7°C vs. 10–11°C recorded at present in the Mediterranean. The molluscan assemblages also indicate that central to eastern Mediterranean salinity was lower than today, suggesting that a different hydrological regime, triggered by increase in rainfall/runoff, was manifested during warmer Pleistocene periods in that area. The distribution of some of the most meaningful taxa studied here indicates that the Mediterranean Sea was divided into two palaeobioprovinces, a cooler western and a warmer eastern one, with a boundary zone possibly located near the present Sicilian–Tunisian Strait.The Anadara sp.–Jujubinus? bullula association is a meaningful ecobiostratigraphical marker for recognizing warm Lower Pleistocene–Upper Pleistocene events. The youngest occurrence of this association has been detected in MIS 5a, in the uppermost part of the Kyllini–Trypiti sequence. Craspedochiton altavillensis, J.? bullula, Ersilia aliceae, Anadara sp., Chama placentina and Plicatula mytilina became extinct during the MIS 5a. Kyllinia parentalis and Terebra corrugata became extinct during MIS 5e. The disappearance of Niso terebellum took place during the Emilian substage (Lower Pleistocene). The gastropod Nassarius musivus musivus, previously considered as becoming extinct at the top of the Gelasian stage, has been recorded in the eastern Mediterranean deposits younger than MIS 5a and older than MIS 3.

Formal definition of the Quaternary System/Period and redefinition of the Pleistocene Series/Epoch

The base of the Quaternary System is formally defined for the first time at the base of the Gelasian Stage as defined by the Global Boundary-Stratotype Section and Point (GSSP) at San Nicola, Sicily, Italy; the Pleistocene Series is extended downwards to coincide with the base the Gelasian Stage; accordingly, the Gelasian Stage is transferred from the Pliocene Series and Neogene System to the Pleistocene Series and Quaternary System. Ratification by the Executive Committee of the International Union of Geological Sciences (IUGS) of these recommendations from the International Commission on Stratigraphy (ICS) followed established procedures of extended, open discussion and deliberation of submitted proposals, and formal voting by the relevant ICS Subcommissions, the ICS Voting Membership, and the IUGS EC. They are now established as global standards.