Quaternary Boundary Research Articles

Tropical forcing and ENSO dominate Holocene climates in South Africa's southern Cape

This paper explores the Holocene climatic dynamics of South Africa's southern Cape, a region that supports a large proportion of the Greater Cape Floristic Region and contains an array of important archaeological sites. While South African climates are generally characterised by marked rainfall seasonality, the southern Cape is currently situated at the interface between tropical and temperate climate systems, resulting in a largely aseasonal rainfall regime. This regime, however, is thought to have been particularly sensitive to past changes in late Quaternary boundary conditions, meaning that variability in either tropical or temperate systems could have significant environmental impacts. Evidence of past climate change, however, remains limited.We present a 9000-year record of hydroclimatic variability obtained from rock hyrax midden stable nitrogen records, from Papkuilsfontein, on the southern slope of the Anysberg Mountains. Resolved to an average 6-year resolution and spanning the period c. 9050 cal yr BP to 1990 CE, this is the highest resolution Holocene record from southern Africa and presents a unique opportunity for the detailed study of the primary drivers and spatial gradients of Holocene climate change in the southern Cape. The data indicate a long-term decrease in aridity across the Holocene and a pattern of variability that reveals remarkable similarities with records from the South African tropics and El Niño–Southern Oscillation proxies, highlighting the significance of tropical systems as drivers of Holocene climate change in the region. This substantially expands what has been previously considered to be the zone of tropical influence, extending from a coastal phenomenon associated with heat transport via the Agulhas Current to encompass much, if not all, of the Agulhas Plain south of the Cape Fold Mountains. These findings provide a valuable new climatic framework for contextualizing changes in ecological and archaeological records in the southern Cape, and contribute to a more comprehensive understanding of the spatio-temporal dynamics of climate systems in southern Africa.

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.

Quaternary Boundary Optimal Control Problem Dominating by Quaternary Nonlinear Parabolic System

In this paper, our purpose is to study the quaternary continuous classical boundary optimal control vector problem (QCCBOCVP) dominated by the quaternary nonlinear parabolic boundary value problem (QNLPBVP). Under suitable assumptions and with given quaternary continuous classical boundary control vector (QCCBCV), the existence theorem for a unique quaternary state vector solution (QSVS) of the weak form (WF) for the QNLPBVP is stated and demonstrated via the Method of Galerkin and the first compactness theorem. Furthermore, the continuity of the Lipchitz operator between the QSVS of the WF for the QLPBVP and the corresponding QCCBCV is proved. The existence of a quaternary continuous classical boundary optimal control vector (QCCBOVC) is stated and demonstrated under suitable assumptions.

THE KUYALNYKIAN REGIONAL STAGE OF THE EUXINIAN AREA OF THE EASTERN PARATETHYS AND THE POSSIBILITY OF DETERMINING THE NEOGENE-QUATERNARY BOUNDARY (PIACENZIAN-GELASIAN) IN THE SOUTHERN UKRAINIAN DEPOSITS

The Kuyalnykian regional stage is a stage of evolution of the Euxine Basin of the Eastern Paratethys with its own conditions for the existence of biota. During that time, the estuarine-marine conditions in southern Ukraine prevailed, leading to the development of various geological formations. However, to date, the Kuyalnykian does not have the official status of a regional stratigraphic unit, either in the Neogene stratigraphic scheme of the Eastern Paratethys or in the Neogene stratigraphic scheme of southern Ukraine, also there is no generalised (formal) description of it as a separate regional stratigraphic unit. The lowering of the Neogene–Quaternary boundary from 1.8 to 2.595 Ma led to a discussion about tracing it in the middle of the Kuyalnykian deposits. This study provides a comprehensive analysis of lithofacies, biostratigraphy (molluscs, ostracods, nannofossils, small mammals), palaeomagnetic and paleogeographic data to obtain a holistic view of the stratigraphy of the Kuyalnykian deposits in southern Ukraine. As a result, we acquired a generalized description and regional stratigraphic scheme of the Kuyalnykian, introduced new local stratigraphic units, obtained criteria for tracing the Neogene-Quaternary boundary, and clarified which part of the Kuyalnykian deposits are of Pliocene age and remain on the pre-Quaternary geological maps, and which of them are already of Pleistocene age and should be transferred to the Quaternary geological maps. The Euxine Basin of the Eastern Paratethys during Kuyalnykian was characterised by euryhaline brackish water, freshwater mollusc assemblages, brackish water and freshwater ostracods assemblages that existed in estuarine-marine environments. The Kuyalnykian deposits are divided into two regional substages and be determinated in the Northern Peri-Black Sea Region, Northern Azov Region, the northern part of the Crimean Peninsula and the Kerch Peninsula. We established the following lithostratigraphic units of the Kuyalnykian for southern Ukraine: the Zamorske Formation in the central and eastern part of the Kerch Peninsula; The Mysove Formation in the northwestern part of the Kerch Peninsula and the eastern part of the Crimean Peninsula is partly Kuyalnykian; the upper part of the Bekhtery Formation on the Left Bank of the Lower Dnieper in the Skadovsk and Holoprystan districts belongs to the lower regional substage of the Kuyalnykian; the Kuyalnyk Formation in the Northern Peri-Black Sea region and Northern Azov region, in the north of the Crimean Peninsula belongs to the upper regional substage of the Kuyalnykian. The age of the Kuyalnykian deposits has been determined based on palaeomagnetic and faunal data. The lower boundary of the Kuyalnykian regional stage is 3.6 Ma which coincides with the boundary of the Hilbert-Gauss palaeomagnetic epochs. The boundary between the Lower and Upper substages is 2.59 Ma (the Gauss-Matuyama boundary). The upper boundary of the Kuyalnykian is set at different stratigraphic levels; it dates 1.780 Ma (the upper boundary of the Olduvai Subchron) in the Indol structural facies zone and also ~1.500 Ma (perhaps above the Gils Subchron, based on small mammal data) or ~0.990 Ma (above the Jaramillo Subchron, based on palaeomagnetic data) in the Western and Eastern structural facies zones of the Northern Black Sea Region, the Northern Azov Region, and the Sivash structural facies zone. This diachrony of the upper Kuyalnykian boundary is explained by environmental difference: while in more marine and “deep water” conditions (Indol structural facies zone) the Kuyalnykian molluscs have already changed to “Gurian (sensu lato)”, in relatively remote estuaries (the Northern Black Sea Region, Northern Azov Region) the Kuyalnykian fauna still “survived”. In addition, it should be noted that the palaeomagnetic dates obtained from studied sections of the Northern Black Sea region are not “absolute” and therefore may be reinterpreted in the future.

Marker Tephra Layers Indicating the Lowest Part of the Quaternary System Found in the Moroyama Hills and Kawajima Core, Western Kanto Plain, Central Japan

Vitric tephra layers named Ushinosawa tephra from the Moroyama Hills in the western Kanto Plain, and KJT-380.5 tephra and KJT-384.15 tephra from the 600 m-long Kawajima core in the central part of Kanto Plain are described. Magnetic polarities suggest these tephra layers are intercalated at the lowest part of the Matuyama choronozone. Ushinosawa and KJT-380.5 tephra layers are characterized by low K2O concentration in volcanic glass, and can be correlated with Reiho tephra of the Tokai Group in Suzuka City, Mie Prefecture. KJT-384.15 tephra is characterized by a high K2O concentration in volcanic glass and can be correlated with newly described Onbebashi 1 and 2 tephras of the Tokai Group. These tephra layers can be considered to be wide spread marker tephras. This is the first report on widespread marker tephras just above the Gauss–Matuyama boundary in Japan. These marker tephra layers are expected to be a valuable key bed for exploring the Neogene–Quaternary boundary in various parts of Japan in the future.

The Upper Pliocene – Quaternary geological history of the Shirak Basin (NE Turkey and NW Armenia) and estimation of the Quaternary uplift of Lesser Caucasus

Stratigraphy, structure, and tectonics of the Turkish part of the intermontane Shirak Basin and the adjacent Susuz Basin were studied based on methods of structural geology, geological and geomorphological correlation, paleontology, paleomagnetism, and archaeology. For the first time, the Pliocene-Quaternary stratigraphy and tectonics of the western Turkish and eastern Armenian parts of the Shirak Basin were correlated. Sedimentary cover of the western part of the basin consists of four units: the Lower Akchagylian (Piacenzian) marine deposits, Karakhach, Ani, and Arapi lacustrine-alluvial units. The Upper Pliocene age of the former formation in the Demirkent section is evidenced by normal palaeomagnetic signature and dinocysts of the Akchagylian aspect with some forms known to have a highest stratigraphic datum near the Pliocene–Quaternary boundary. The age of the Karakhach unit is estimated at 1.9–1.7 Ma based on similar geomorphological position and composition with corresponding deposits in Armenia, normal polarity, and a record of the Early Palaeolithic artefact. The dating of the Ani unit to the Calabrian, and the Arapi unit to the lower Middle Pleistocene is evidenced by assemblages of molluscs and small mammals, Acheulian artefacts, palaeomagnetic data, and geomorphological position similar to the correlated sedimentary sequences in the Armenian part of the basin.The level of the Akchagylian brackish water basin at the Neogene–Quaternary boundary (2.58 Ma) was close to the recent oceanic level. The recent altitude of the top of the Lower Akchagylian deposits in the Demirkent section is 1565 m. This defines the average rate of the Quaternary uplift in this part of Lesser Caucasus at 0.6 mm/year. The Shirak Basin is bounded and ruptured by fault and flexure-fault zones. Because of offsets on the Çamuşlu and Akhuryan zones, the central part of the northern Shirak Basin is subsided relative to the Demirkent section at 130–165 m. The movements in the Çarçioğlu zone caused a 100–120 m rise of the Ani unit surface in the Susuz Basin relative to the adjacent part of the Shirak Basin. The north-western border of the Susuz Basin is uplifted on the Sarikamiş fault zone. Thus, the Quaternary uplift ranges near 0.6 ± 0.1 mm/year. To the north of the Shirak Basin, in the Upper Akhuryan and Lori Basins and the Debed River valley, the rate of uplift during 0.65–0.6 Ma is estimated at about 1 mm/year and the adjacent Bazum and Javakheti Ridges rose more intensively. Therefore, the uplift could accelerate during the time interval of 0.65–0.6 Ma.

Changes in stratigraphic charts of neogene and quaternary deposits of Belarus due to the revision of the boundary between systems

Following the decision of the International Union of Geological Sciences on the transfer of the lower boundary of the Quaternary System/Period and the Pleistocene Series/Epoch from 1.8 Ma to 2.58 Ma (to the base of the Gelazian Stage/ Age of the Pliocene), the changes have been made in Stratigraphic charts of Neogene and Quaternary Deposits of Belarus (2010). The Neogene – Quaternary boundary in the territory of Belarus is aligned with the International Chronostratigraphic Chart and is made between the Kholmech horizon (analogue of Zanclean and Piacenzian, Pliocene) and the Dvorets horizon (analogue of Gelasian) displaced from the Pliocene to the lower base of the lowermost Pleistocene. Its new position in the sections is substantiated by paleobotanical data. New geological units were introduced into regional and local stratigraphic charts of the Neogene and Quaternary.

Boreotropical range expansion and long-distance dispersal explain two amphi-Pacific tropical disjunctions in Sabiaceae

Sabiaceae comprises three genera and ca. 80 species with an amphi-Pacific tropical disjunct distribution. It has been unclear whether the family is monophyletic, where the family belongs within the angiosperm phylogeny, and when and how is present-day disjunct distribution originated. To address these questions, we conducted a phylogenetic analysis of Sabiaceae with comprehensive sampling of the family and basal eudicots using six chloroplast DNA loci (atpB, rbcL, matK, ndhF, atpB-rbcL and trnL-trnF). Our results support the monophyly of Sabiaceae s. l. that includes three genera: Meliosma Blume, Ophiocaryon Endl. and Sabia Colebr. The placement of Sabiaceae as sister to Proteales receives moderate bootstrap support, and is corroborated by various alternative hypothesis tests. Within Sabiaceae, Ophiocaryon and Sabia were resolved as strongly supported clades, whereas Meliosma was paraphyletic with Ophiocaryon nested within it. The biogeographically disjunct accessions of Meliosma alba (which is alternatively known as Kingsboroughia alba (Schltdl.) Liebm.) sampled from southwestern China and Mexico form a monophyletic group. Molecular dating and ancestral area reconstruction suggest a Eurasian origin of Sabiaceae in the late Cretaceous and a boreotropical range expansion during Paleogene. Southward migrations were inferred from continental Eurasia to the Malesian region in Sabia and in the Asian Meliosma, and from Central America to South America in the Neotropical clade of Meliosma in response to climatic cooling after the late Miocene. A long distance dispersal from Central America to tropical Asia was suggested during the time at the Neogene and Quaternary boundary in Meliosma alba (now recognized as Kingsboroughia alba). Our results also support the recognition of Kingsboroughia Liebm. as a distinct genus to maintain the monophyly of each of the genera: Meliosma, Ophiocaryon and Sabia. Kingsboroughia along with Meliosma and Ophiocaryon constitutes the subfamily Meliosmoideae Mast., while Sabia is the sole genus of Sabioideae Y.W. Law & Y.F. Wu.

New constraints on the timing of flexural deformation along the northern Australian margin: Implications for arc-continent collision and the development of the Timor Trough

Numerous extensional faults offset the passive margin strata of the northern Bonaparte Basin. This extensional deformation has been attributed to lithospheric flexure of the descending Australian Plate, in an overall convergence setting. Here we use an extensive 2D and 3D seismic dataset calibrated with well biostratigraphy and strontium (Sr) isotope age data to constrain the timing of deformation along the northern Australian margin during the Neogene. Analysis of fault throw and differential thickness variations give new insights on the propagation and slip history of the faults. Along-dip throw profiles exhibit ‘D’ shape distributions, skewed towards the top. Positive throw gradients above the throw maxima, coinciding with intervals of growth strata, indicate multiphase fault activity. Results indicate that post-rift extensional deformation initiated during the latest Miocene (ca. 6Ma). The development of the modern Timor Trough (as a foreland basin) and Cartier Trough also commenced during this period. A second episode of increased tectonic activity occurred around the Pliocene–Quaternary boundary (ca. 3Ma), and the deformation continued intermittently to the present-day. These new results are in agreement with the timing of initiation of collision between the Australian Plate and the Banda Arc and uplift of the Timor Island, recently derived from stratigraphic analysis in Timor. These regional tectonic events have profoundly affected the paleogeography of the Timor Sea and may explain major changes in oceanic circulation and climate during the Neogene.

Changing provenance of late Cenozoic sediments in the Jianghan Basin

The Yangtze River is one of the most important components of the East Asia river system. In this study, sediments in the Jianghan Basin, middle Yangtze River, were selected for trace element and rare earth element (REE) measurements, in order to decipher information on the change of sediment provenance and evolution of the Yangtze River. According to the elemental variations, the late Cenozoic sediments of the Jianghan Basin could be divided into four parts. During 2.68–2.28 Ma and 1.25–0 Ma, provenance of the sediments was consistent, whereas sediments were derived from variable sources during 2.28–1.25 Ma. Comparison of the elemental compositions between the Pliocene and Quaternary sediments revealed a change in sediment source from a more felsic source area to a more basic source area around the Pliocene–Quaternary boundary. Input from the Emeishan LIP should account for this provenance change. Based on the provenance analysis of sediments in the Jianghan Basin, we infer that the Yangtze River developed into a large river with its drainage basin extended to the Emeishan LIP no later than the Pliocene–Quaternary boundary.

The stratigraphical position and the use of the term Eopleistocene in Serbian geological literature

When the Calabrian Stage was included in the Quaternary frame by the decision of the 18th IGC (1948), it implied changes in the stratigraphical scale subdivision. At the beginning of the 1970s after the addition of the Calabrian Stage to the Quaternary and the lowering of the Quaternary boundary, it became evident that in the new scheme a gap of nearly 1 My was created in the case of fluvial and fluvio-lacustrine formations. The time frame of the Pleistocene could not include the oldest Quaternary fluvial and fluvio-lacustrine formations because of the lowering the Quaternary boundary to nearly 1.8 Ma, as was done in marine (Calabrian Stage) and terrestrial formations (Villafranchian Stage). This was one of the main reasons why the term Eopleistocene was implemented into the Serbian Quaternary stratigraphical terminology in 1972 and it was used in a semi-official way until 2010. In 2009, with the official ratification of the ICS (IUGS) of the lowering of the Neogene/Quaternary, i.e. Pliocene/Pleistocene boundary to 2.58 Ma, the use of the Eopleistocene in the Serbian stratigraphical terminology lost its meaning.The use of the term Eopleistocene in the Serbian stratigraphical scheme cannot be accepted in the sense of modern stratigraphical principles, because the mixing of the discriminatory concepts of the Alpine morphostratigraphical model with regional (exUSSR) climatostratigraphic and/or biostratigraphical units was obvious. As a term, Eopleistocene also caused a number of unclear and undefined problems/misunderstandings with regard to relations: Eopleistocene–Pleistocene, Eopleistocene–Lower Pleistocene, Eopleistocene-Alpine morphostratigraphical stages. With the developments and changes in the Quaternary stratigraphy, the Serbian Eopleistocene should be interpreted and replaced with (upper part of) Lower Pleistocene, because the base of the Eopleistocene had been identified at nearly 1.8 Ma and the Lower/Middle Pleistocene (Brunhes-Matuyama) boundary does not correspond with the Eopleistocene–Neopleistocene boundary.

Les limites du Quaternaire : 1,8 ou 2,6 millions d’années? Apports de l’étude concernant les premiers représentants du genre homo

The Quaternary, which is sometimes also termed the Anthropogene Period, often is linked to the beginning of humankind. But what exactly is the basis in the fossil hominin record for this link, in particular what is the early Homo evidence? Since 1999, debate concerning the definition of the genus Homo and the identification of its first members has intensified. At the centre of recent debates, there are four hypotheses: (1) all early Homo specimens belong to the same species: Homo habilis sensu lato; (2) the early Homo hypodigm is heterogeneous, two species could be defined: Homo habilis sensu stricto and Homo rudolfensis; (3) these species do not belong to the genus Homo but to the genus Australopithecus; or (4) it would be more appropriate to put the specimens of Homo rudolfensis into the genus Kenyanthropus. The earliest appearance of the genus Homo will differ depending upon the favoured hypothesis: 2.45 Myr (hypotheses 1 and 2); 1.9 Myr (hypothesis 3); 1.9 or 2.4 Myr (hypothesis 4, depending on the genus attribution for habilis (2.4 Myr if Homo; 1.9 Myr if Australopithecus)). Our study, based on palaeoanthropological data, is focused on the 2.6-1.6 Myr period. In this paper, we propose to review and assess knowledge of early Homo taxonomy in the context of the definition of the Quaternary boundary.

Upper Siwalik mammalian faunas of India and associated events

Tatrot and Pinjor mammalian faunas are well known from the Chandigarh and Jammu regions of India. The Pinjor Formation of the type area in the Chandigarh region has been dated by magnetostratigraphy and ranges from 2.48 to 0.63Ma. The pre-Pinjor beds of the Upper Siwalik Subgroup are referred to as the Saketi Formation and are characterized by the presence of the Tatrot Fauna. These are well exposed in the type area of the Pinjor Formation. The Pinjor Mammalian Fauna marks the end of the record of the Siwalik vertebrate faunal succession since the overlying Boulder Conglomerate Formation, the youngest formation of the Siwalik Group, is devoid of fossils. About 49 mammalian taxa are restricted to the Pinjor Formation. The Saketi beds are differentiated from the Pinjor beds by 30 Tatrot taxa. In the Jammu region, the Nagrota Formation of the Upper Siwalik Subgroup contains both the Tatrot and Pinjor faunas; however both faunas are not as well developed as compared to those of the Chandigarh region. The extinction or migration of the Pinjor Mammalian Fauna began near the Olduvai subchron (i.e. near Neogene\\Quaternary boundary). However, in the Parmandal-Utterbeni (Jammu) and Patiali Rao (Chandigarh) sections, the fauna survived well after the Olduvai subchron, and extinction in various sections ranges in age from 1.72 to 0.6Ma. Near the Olduvai subchron, the last phase of the Himalayan orogeny was marked by initial deposition of the Boulder Conglomerate Formation and was probably one of the reasons for the gradual extinction of the Pinjor Mammalian Fauna. Two biostratigraphic interval-zones, Elephas planifrons Interval-Zone (3.6–2.6Ma) and Equus sivalensis Interval-Zone (2.6–0.6Ma) are also recognized on the basis of mammalian fossils and magnetostratigraphy. Twenty-five taxa made their first appearance in the older zone whereas forty-eight taxa are restricted to the younger zone.

An alternative hypothesis for the origin of Amazonian bird diversity

Summary AimTo determine the origin of the high diversity of birds and other animals and plants in Amazonia. Previous hypotheses are: palaeogeography hypothesis, river hypothesis, river‐refuge hypothesis, refuge hypothesis, disturbance‐vicariance hypothesis, gradient hypothesis, pest‐pressure hypothesis, intermediate disturbance hypothesis, riverine disturbance hypothesis, models of fine‐scale habitat heterogeneity, lake hypothesis, and museum hypothesis. MethodsAt present there is agreement between areas of high species diversity and sites located over 100 m. As these sites would have been islands during a sea‐level rise of this value, it was important to determine the probable distribution of these islands in Amazonia during a marine transgression. For that purpose, I traced the 100 m contour line from topographic maps. ResultsTwo broad marine transgressions would have been produced from the Atlantic Ocean via the Amazon and Orinoco rivers. Two very large islands would have been formed to the north of the Amazon River, and other islands and archipelagos would have been formed along the coastal lowlands of Guiana, and at the periphery of the Amazon basin. The area located between the Solimoýes and Negro rivers and in the lower Branco would have been completely covered by the sea. Main conclusionsA substantial part of the high diversity of forest and nonforest birds in lowland Amazonia can be hypothetysed to have originated during sea‐level rises of about 100 m in the Quaternary and late Tertiary. These transgressions would have fragmented the Amazonian lowland into a large number of true islands and archipelagos, thus favouring active allopatric speciation. Values appreciably higher than 100 m above the present sea‐level during previous periods of the Tertiary would have produced segregation of the biota earlier than the Tertiary–Quaternary boundary. Sea‐level rises and vegetational changes (by aridity or cooling) would thus have driven the speciation pump, and local disturbances and other processes, would maintain the diversity.

Twisting or stable quaternary boundary? A perspective on the glacial late Pliocene concept

There has been a long-running debate over the position of the Pliocene-Pleistocene boundary, i.e. 1.8 Ma versus 2.6 Ma. This study presents litho- and pedo-stratigraphic characteristics, grain size, magnetic susceptibility, and dust sedimentation rates for ‘red clay’-loess sequences over northern China, in order to assess the drastic climatic event(s) recorded in the quasi-continuous eolian deposits, and to readdress the position of the Pliocene-Pleistocene boundary. In complete Chinese loess sequences, 33 soil-loess couplets have been identified and labeled with Si-Li system. Traditionally, the base of Chinese loess has been designated at the bottom of loess unit L33. However, a typical loess layer within the uppermost ‘red clay’ is identified and formally designated here as L34 and the soil unit between L33 and L34 as S33, which lowers the basal age of Chinese loess from 2.6 Ma to ∼2.8 Ma. Although the Neogene ‘red clay’ and the overlying Quaternary loess are both of windblown origin, they have quite different pedogenic characteristics. The loess consists of alternating reddish soil and yellowish loess layers, while the ‘red clay’ is composed of soils with much redder colour and carbonate nodule layers. In general, the “red clay” has been subjected to stronger pedogenic processes than the overlying loess, and can be regarded as an extremely thick soil complex. The alternation of loess and soils reflects large-scale oscillations between glacial and interglacial conditions, whereas the well-developed ‘red clay’ deposition indicates a relatively stable climate condition. At ∼2.8 Ma, shortly before the Gauss/Matuyama boundary, the eolian sequences show a sedimentary transition from the well-weathered ‘red clay’ to the alternating loess and paleosol deposits, accompanied by coarser particle size, increased dust accumulation rates, and change of magnetic susceptibility signature. These indicate a large climatic shift from long-lasting warm-humid conditions to large-amplitude cold-dry and warm-humid fluctuations around 2.8 Ma, and a dramatic increase in aridity over the dust source region. In contrast, such a drastic event is not identified around the top of the Olduvai event or at any other time of the past 7.7 Ma. As the Gauss/Matuyama boundary offers a sound foundation for global time correlation and chronostratigraphic classification, these results still support the proposal of ICS and INQUA, that the conventional Pliocene-Pleistocene boundary should be lowered from 1.8 Ma to 2.6 Ma.

Evolution of life during the Pliocene and Pleistocene and the Neogene—Quaternary boundary

Evolution of life during the Pliocene and Pleistocene and the Neogene—Quaternary boundary