Late Matuyama Research Articles

Global Geomagnetic Field Evolution From 900 to 700 ka Including the Matuyama‐Brunhes Reversal

AbstractPolarity reversals and excursions are the most significant geomagnetic field changes generated in the liquid outer core of the Earth, therefore studying them helps understand geodynamo processes. This study examines the Matuyama‐Brunhes (MB) reversal using a new reconstruction of the global geomagnetic field based on paleomagnetic data, termed Global Geomagnetic Field Model for the MB reversal (GGFMB). GGFMB covers 900–700 ka, including late Matuyama and early Brunhes. This allows us to also investigate the Kamikatsura excursion (ca. 888 ka). The model is based on 38 high‐quality paleomagnetic sediment records with age control mostly independent of the magnetic signal. GGFMB suggests that the MB reversal began about ∼799 ka, when non‐dipole field components increased and the axial dipole component decreased. The transitional fields first appeared on Earth's surface in the high‐latitude southern hemisphere and equatorial regions. The minimum dipole strength was reached around 780 ka and the axial dipole changed sign. After ∼10 Kyr, the field stabilized in the normal polarity of the early Brunhes. The MB reversal lasted ∼29 Kyr (from 799 to 770 ka) and had slower rate of dipole decay than recovery as well as lower dipole moment for several millennia before than after the reversal. According to GGFMB, the dipole moment during the Kamikatsura excursion was approximately half that of the current field and it was a regional excursion observed only over eastern Asia and North America. Our sediment data collection is heavily biased toward the northern hemisphere, thus more southern hemisphere records are needed to demonstrate GGFMB's robustness in this region.

Record and provenance of Pleistocene volcaniclastic turbidites from the central Lesser Antilles (IODP Expedition 340, Site U1398B)

Pleistocene volcaniclastic turbidites drilled during IODP 340 (U1398B, ≤ 170 mbsf) in the Grenada basin west of Martinique (central Lesser Antilles) have been investigated for sediment provenance. U/Pb ages by ion microprobe from 323 detrital zircon grains at three U1398B levels reveal youngest population maximum ages which are interpreted to represent major eruption periods. Systematic age progression with depth defines a ~ 20 cm/ka depositional rate and provides a robust chronostratigraphic frame for the ≤167.5 mbsf (≤ 856 ± 10 ka) interval of U1398B, and confirms on-board paleomagnetic constraints for a possible late Matuyama age for the lowermost sampled parts of U1398B. The achieved chronostratigraphic frame yields sedimentation rates for carbonate ooze and of volcaniclastic sands and gravels of 8.2 and 7.6 cm/ky, respectively. Depth plots of cumulative thickness of these lithologies allow for a differentiation into periods of enhanced and reduced volcanic activity.Porphyritic lava and mineral fragments include plagioclase, diopside, augite and enstatite, as well as magnesio-hornblende and ferri-tschermakite. Geothermobarometry based on clinopyroxene and amphibole reveal the dominant role of upper crustal magma reservoirs. Ferri-tschermakite from 93 and 167.5 mbsf (~410 and 856 ka, respectively) records contributions from lower crustal, hot magma reservoirs. These temperature estimates are supported by Ti-in-zircon data. O-isotope ratios and trace elements in zircon reflect magmatic activity typical for an evolved island arc system.The bathymetry of the Grenada basin, the composition of lava clasts and minerals, scarcity of altered lava fragments, the narrow maximum age population of detrital zircon, and the O-isotope and trace element data on zircon suggest that the majority of U1398B volcaniclastic turbidites originated from the island of Dominica. The thick volcaniclastic units are most likely related to major eruption periods of andesitic magma that ascended from crustal reservoirs. Debris avalanche-related processes seem to be less important in U1398B at ≤170 mbsf.Mineral chemistry and O-isotope data obtained from plagioclase, pyroxene, amphibole, zircon and glass, separated from deep marine volcaniclastic turbidites, provide a chronostratigraphic frame for the sedimentary succession, and helps to genetically fingerprint the volcanic and magmatic evolution of the neighboring volcanic islands. While this is documented here for the well-constrained Pleistocene history of the central Lesser Antilles, the applied methods may also be used to characterize ancient marine volcaniclastic mass flow deposits and to reconstruct their volcanic source areas.

Neotectonics of the Pleistocene deposits in the northeast of Taman peninsula, the southern Asov sea region

Studies in paleomagnetism, structural geology, and paleontology (mammals, molluscs, palynology) in the coastal sections of the Taman Peninsula north-eastern part (2017–18) resulted in definition of three sedimentary members. The sandy and clayey lower member (I) formed at 2.1–1.7 Ma. It contains a normally magnetised zone within deposits of reversed polarity correlated to the Olduvai Subchron and the Matuyama Chron.
 The middle member (II) is composed of the basal pebbles overlain by sands. The reversely magnetised deposits hosting the Sinyaya Balka site, the type locality of the Tamanian faunal complex, is correlated to the basal bed of the middle member II. The overlying sands are normally magnetised (Jaramillo Subchron) in the lower part and show reverse polarity (late Matuyama Chron) in the upper part. The member II is dated in the range of 1.3–0.78 Ma.
 The silty upper member (III) represents Middle-Late Pleistocene. The dissimilar displacement degree of the members reflect developmental stages of the Quaternary deformation.
 The member I is characterised by dip angles up to 70° is fragmented by faults into blocks. The member II filled the relief of the eroded surface of the Member I and also displaced by faults. The faulting separated the bone-bearing body of the Taman faunal complex as a rock land-slide. The attitude of the member III outline an anticline with a gentle south-western and a steeper north-eastern limbs eroded by land-slides and marine abrasion. During its entire life the anticline was affected by mud volcanism. The anticline continues its development at the present stage.

Tectonics of Pleistocene Deposits in the Northeast of Taman Peninsula, South Azov Sea Region

Studies in paleomagnetism, structural geology, and paleontology (mammals, mollusks, palynology) in the coastal sections of the Taman Peninsula north-western part (2017–18) resulted in definition of three sedimentary sequences. The sandy and clayey lower sequence (I) formed at 2.1–1.7 Ma. It contains a normally magnetised zone within deposits of reversed polarity correlated to the Olduvai Subchron and the Matuyama Chron. The middle sequence (II) is composed of the basal pebbles overlain by sands. The reversely magnetised deposits hosting the Sinyaya Balka site, the type locality of the Tamanian faunal complex, is correlated to the basal bed of the middle sequence II. The overlying sands are normally magnetised (Jaramillo Subchron) in the lower part and show reverse polarity (late Matuyama Chron) in the upper part. The sequence II is dated in the range of 1.3–0.78 Ma. The silty upper sequence (III) represents Middle-Late Pleistocene. The dissimilar displacement degree of the sequences reflect developmental stages of the Quaternary deformation. The sequence I is characterised by dip angles up to 70° is fragmented by faults into blocks. The sequence II filled the relief of the eroded surface of the sequence Member I and also displaced by faults. The faulting separated the bone-bearing body of the Taman faunal complex as a rock land-slide. The attitude of the member III outline an anticline with a gentle south-western and a steeper north-eastern limbs eroded by land-slides and marine abrasion. During its entire life the anticline was affected by mud volcanism. The anticline continues its development at the present stage.

Magnetostratigraphic and archaeological records at the Early Pleistocene site complex of Madigou (Nihewan Basin): Implications for human adaptations in North China

The Nihewan Basin in North China contains the densest concentration of early Pleistocene Paleolithic sites outside Africa. This paper introduces a new archaeological site complex at Madigou (MDG) that was systematically excavated from 2011 to 2014 in the northeastern part of the Nihewan Basin. The site contains fossils and well-preserved stone artefacts in fluvio-lacustrine sediments. Our magnetostratigraphic results situate the MDG sedimentary sequence in the early Brunhes normal chron and the late Matuyama reverse chron, including the Jaramillo normal subchron. The MDG artifact layers are positioned within the pre-Jaramillo Matuyama chron, with an estimated age of ca. 1.2 Ma, close to the onset of Mid-Pleistocene climate transition. The MDG core and flake technology includes bipolar flaking of siliceous dolomite cobbles, and freehand flaking of chert and brecciated chert block fragments. Mammalian fauna and pollen compositions indicate that the MDG hominins lived in an open habitat varying from lightly-wooded grassland to an ecosystem dominated by sparse steppe near the shore of the Nihewan paleolake. Our combined results in the fields of archaeology, paleontology, palynology and magnetochronology suggest that innovations in technological behavior may correlate with adaptations to high environmental variability during the start of Mid-Pleistocene climate transition.

Cosmogenic signature of geomagnetic reversals and excursions from the Réunion event to the Matuyama–Brunhes transition (0.7–2.14 Ma interval)

Long-term variations of the geomagnetic dipole moment (GDM) during periods of stable polarity and in transitional states (reversals and excursions) provide key information for understanding the geodynamo regime. Following several studies dealing with the Brunhes chron and the Matuyama–Brunhes transition, this study presents a new authigenic 10Be/9Be ratio (Be-ratio) record obtained from the MD97-2143 core (western Pacific Ocean). This new Be-ratio series yields a record of GDM variations covering the early Brunhes and mid to late Matuyama time period (i.e. 700–2140 ka), independently from the relative paleointensity (RPI) record obtained from the same core, that can be compared with available RPI records and stacks. Stratigraphic offsets measured between the Be-ratio peaks and the corresponding RPI minima reach 2 to 14 cm. They can be assigned to (post-) detrital remanent magnetization (pDRM) effects leading to magnetization locking-in delays varying from 2 to 12 ka in the studied core. 10Be overproduction episodes triggered by geomagnetic dipole moment lows (GDL) linked to polarity reversals and excursions confirm the global control exerted by the GDM on cosmogenic radionuclides production. A dipole moment reconstruction derived from the Beryllium-10 (BeDiMo) was compiled and calibrated using absolute paleointensity data. This independent record complements the available paleomagnetic RPI records, permitting 1) to overcome the pDRM lock-in offsets induced below the mixing layer, 2) to confront and increase the robustness and precision of GDM reconstructions and, 3) to better constrain the chronology of geomagnetic field instabilities during the mid to late Matuyama chron. Our new 10Be derived inventory is fully compatible with the GDL series linked to geomagnetic polarity reversals and events (Matuyama–Brunhes transition, Jaramillo and Olduvai subchron boundaries, Cobb Mountain, Réunion) and it strengthens the occurrence of several excursions (Kamikatsura, Santa Rosa, Punaruu, Bjorn, Gilsa, Gardar) that were until now reported from only sparse locations.

Magnetic excursions in the late Matuyama Chron (Olduvai to Matuyama‐Brunhes boundary) from North Atlantic IODP sites

AbstractThe sedimentary record of late Matuyama magnetic excursions, between the end of the Olduvai Subchron and the Matuyama‐Brunhes boundary, has relied on North Atlantic Ocean Drilling Program (ODP) Sites 983/984, and individual recordings at ODP Site 1021 from the California Margin, and Core MD972143 from the west Philippine Sea. North Atlantic IODP Sites U1305, U1306, U1307 (Eirik Drift, off SE Greenland), and Site U1308 (central Atlantic) provide new records from u‐channel samples and discrete (8 cm3) cubic samples, collected from multiple holes drilled at each site. The results confirm the existence of the Intra‐Jaramillo, Punaruu, Bjorn, Gardar, and Gilsa excursions and possibly the Kamikatsura excursion. These excursions are not recorded at all sampled sites, although they do correspond to excursions recorded at ODP Sites 983/984 and to relative paleointensity minima recorded at all studied sites. For some records, including that of the Bjorn excursion (1251 ka), antipodal magnetization directions yield virtual geomagnetic poles that reach high northern latitudes, implying that the excursion involved reversal of the main axial dipole field. On the other hand, excursions are often partially and inadequately recorded, attributable to a combination of the brevity of geomagnetic excursions, bioturbation, and filtering of the magnetization signal by the detrital remanent magnetization acquisition process, nonuniform sedimentation rates at millennial/centennial scales, and possibly unrecognized drilling/sampling disturbance.

Age of Mammuthus trogontherii from Kostolac, Serbia, and the entry of megaherbivores into Europe during the Late Matuyama climate revolution

At the Drmno open-pit coal mine near Kostolac in Serbia, a nearly complete skeleton of Mammuthus trogontherii (nicknamed Vika) was discovered in a fluvial deposit overlain by a loess–paleosol sequence where a second paleontological level named Nosak with remains of M. trogontherii was found. We studied the magnetostratigraphy of the Kostolac sedimentary sequence and found that the Vika layer dates to ~0.8Ma, shortly before the Brunhes–Matuyama boundary. In addition, according to our age model and previously reported optically stimulated luminescence and electron spin resonance dates, the Nosak fossils have an estimated age of 0.19Ma and lived during the earliest part of Marine Isotope Stage 6. It appears therefore that at Kostolac, M. trogontherii is preserved both at its earliest occurrence at ~0.8Ma and close to its latest occurrence at 0.19Ma, and may well have been present in between, albeit not yet found. We speculate that megaherbivores such as M. trogontherii entered Europe along a conjunct Danube–Po River migration conduit connecting western Asia-Levant with central-southern Europe where vast and exploitable ecosystems, particularly suited for steppe- or savanna-adapted megaherbivores from Asia and Africa, developed during the late early Pleistocene climate revolution at around 0.8Ma.

Barranc de la Boella (Catalonia, Spain): an Acheulean elephant butchering site from the European late Early Pleistocene

ABSTRACTEvidence of late Early Pleistocene elephant butchery activity has been excavated in the Pit 1 locality at Barranc de la Boella (Catalonia, Spain). The fossil assemblage mainly comprises the remains of one prime adult individual ofMammuthus meridionalis, together with 125 lithic artefacts, among which several refitting groups of chert have been identified. The lithic assemblage from the Pit 1 locality is composed of cobbles, cores, simple and retouched flakes, together with a large, well‐fashioned pick of hard‐wearing schist. Spatial, zooarchaeological, taphonomic, technical and use‐wear analyses confirm that the occupation was devoted to butchery of the mammoth carcass. The activity zone is in a fluvio‐deltaic area that incises the terrace T+60 of the lower Francolí river basin, 50 m a.s.l. Palaeomagnetic and cosmogenic analyses, as well as microfaunal (Mimomys savini,Victoriamys chalinei) and macrofaunal biostratigraphy (Mammuthus meridionalis), support the timing of the occupation to the late Matuyama chron. These various lines of evidence point to Barranc de la Boella being the oldest Early Acheulean butchering site in Europe. Ongoing excavations at several localities at Barranc de la Boella are yielding new data on the palaeoenvironmental, geochronological and technological framework of these occupations. Finally, the evidence is integrated into current understanding of the subsistence strategies practised by Early Pleistocene hominins.

Paleo-megalake termination in the Quaternary: Paleomagnetic and water-level evidence from south Bohai Sea, China

Asian marginal seas play an important role in moderating material and energy flux linkages between Asia and the Northwest Pacific, and thus have profound climatic and environmental effects. In this study, by combining paleomagnetic study with sediment grain-size analysis on the Lz908 borehole sedimentary sequence from the southern Bohai Sea, new insights into regional geomorphological process since the late early Pleistocene are obtained. The main results are as follows. (1) Paleomagnetic findings suggest that the sequence recorded the Brunhes normal chron and the late Matuyama reverse chron, including the Jaramillo normal subchron. (2) The sedimentary processes in the study area since 1327ka show a three-stage pattern, with depositional rates of 4.3, 17 and 107cm/ka during 1327–260ka (later part of the early and middle Pleistocene), 260–10ka (late middle and late Pleistocene), and the Holocene, respectively. (3) The sedimentary basin was a part of the Bohai Paleolakes (BHPL) prior to 260ka, whose water levels were consistently higher than 3m above the present-day level. After 260ka, seawater entered the Bohai basin, and relative sea level cyclically fluctuated with global sea-level changes. We therefore infer that the Miaodao Islands, which were the natural barrier of the BHPL blocking seawater entry, had partially subsided before 260ka, only allowing seawater to enter the basin during a global sea-level maximum. The BHPL terminated around 260ka, and the “barrier” subsided completely around ~130ka, causing the Bohai basin to become an inner shelf sea.

Magnetostratigraphic dating of the Shanshenmiaozui mammalian fauna in the Nihewan Basin, North China

Timing of the mammalian faunas in the Nihewan Basin, North China has provided insights into our understanding of Quaternary biochronology and biostratigraphy in East Asia. Here we contribute to this topic with detailed magnetostratigraphic investigation, coupled with mineral magnetic measurements on a fluvio-lacustrine sequence in this basin, which contains the Shanshenmiaozui mammalian fauna. Magnetite and hematite were identified as the main carriers for the characteristic remanent magnetizations. Magnetostratigraphic results show that the Shanshenmiaozui sedimentary sequence recorded the Brunhes chron, the Jaramillo subchron, and the late Matuyama chron. Stratigraphic correlation in terms of lithology, magnetic susceptibility and magnetic polarity sequences between the Shanshenmiaozui, Xiaochangliang and Dachangliang sections indicates that the Shanshenmiaozui mammalian fossil layer is younger than the Xiaochangliang and Dachangliang artefact layers, which have been previously estimated to be about 1.36 Ma. The age of the Shanshenmiaozui mammalian fossil layer at the bottom of the section is estimated to be about 1.2 Ma. The new magnetostratigraphy of the Shanshenmiaozui section provides useful constraints on lithostratigraphic and biostratigraphic correlations in the Nihewan Basin.

The small mammals of Sima del Elefante (Atapuerca, Spain) and the first entrance of Homo in Western Europe

The small-mammal assemblages associated with the fossil human remains of the Sima del Elefante site provide the best tool for estimating the age for the first appearance of Homo during the Early Pleistocene of Western Eurasia. Sima del Elefante (TE) is part of the archaeo-palaeontological complex known as the Atapuerca cave-sites, in Burgos, Spain. In 2007, the lower levels of Sima del Elefante yielded the earliest European fossil of a Homo species from the level Trinchera Elefante 9c (TE9c). The site is an opening to the Galería Bajainfill, with 25m of cave sediments ordered in 22 stratigraphic levels. The Lower Red Unit, TELRU, comprises the stratigraphic levels Trinchera Elefante 7 (TE7) to Trinchera Elefante 16 (TE16). The faunal association of the TELRU is composed of nearly one hundred species of vertebrates, including 17 species of amphibians and squamate reptiles, nearly 60 mammals (Homo sp. included), around 15 birds, and an indeterminate number of fishes. Only levels TE7 to TE14 yielded vertebrate fossil remains.The small-mammal assemblages of the TELRU display the same species composition from level TE7 to level TE14, though their ecological structure varies in the relative richness in number of specimens (Shannon). The species of small mammals from Sima del Elefante TELRU levels TE7 to TE14 are: the shrews Sorex sp.1, Sorex sp. 2, Asoriculus gibberodon, Beremendia fissidens, Crocidura kornfeldi; the talpids Galemys cf. G. kormosi and Talpa cf. T. europaea; the erinaceid Erinaceus cf. E. praeglacialis; the lagomorphs Oryctolagus cf. O. lacosti and Lepus cf. L. terraerubrae; the chiropters Miniopterus schreibersii, Myotis sp., Rhinolophus sp. and Chiroptera spp.; the rodents Sciurus sp., Castillomys rivas, Apodemus aff. A. sylvaticus, Allophaiomys lavocati, A. burgondiae, A. nutiensis, Arvicola jacobaeus, Ungaromys nanus, Pliomyscf. P. simplicior, Eliomys sp. and Castor sp. This faunal assemblage correlates levels TE7 to TE14 with other Western European localities that are biostratigraphically dated to a Late Villafranchian or Early Biharian age, localities such as Bagur 2, Fuente Nueva 3, Barranco León D, Le Vallonnet, Les Valerots, Courterolles and Monte Peglia, among others. These Late Villafranchian localities are situated in the late Matuyama, pre-Jaramillo palaeomagnetic zone, thus dating to around 1.5 to 1.2Ma.

Magnetostratigraphic dating of the Hougou Paleolithic site in the Nihewan Basin, North China

The fluvio-lacustrine sedimentary sequences in the Nihewan Basin, northern China, are important for studying Quaternary land mammal evolution and Paleolithic settlements in the high-latitude temperate East Asia. Here we report new magnetostratigraphic results that constrain age of the Hougou Paleolithic site in this basin. Magnetite and hematite were identified as carriers of the characteristic remanent magnetizations, with the former being dominant. Magnetic polarity stratigraphy shows that the Hougou sequence recorded the very late Matuyama reverse chron and the Brunhes normal chron. The age of the Hougou Paleolithic site was estimated to be 395 ka based on an averaged rate of sediment accumulation. The combination of our magnetostratigraphy and previously published chronological data for early Paleolithic or human sites in the high-latitude northern China may document a persistent colonization of the hostile high-latitude areas of the eastern Old World during the middle- early Pleistocene.

Magnetostratigraphic dating of the Huojiadi Paleolithic site in the Nihewan Basin, North China

The fluvio-lacustrine sequences in the Nihewan Basin, northern China provide important terrestrial archives of paleoclimate and paleoenvironment as well as an important source of Paleolithic settlements and therefore early human occupation in the eastern Old World. Magnetostratigraphic dating of the sequences has permitted the precise timing of the basin infilling and associated Paleolithic and mammalian fauna sites. Here we report new magnetostratigraphic results that place stringent age controls on the Huojiadi Paleolithic site in this basin. Partially-oxidized magnetite and hematite were identified as the major carriers for the characteristic remanent magnetizations. Magnetostratigraphic results show that the Huojiadi sequence recorded the very late Matuyama reverse chron and the Jaramillo normal subchron. The stone artifact layer resides in the Jaramillo normal subchron, yielding an estimated age of around 1.0 Ma for the Huojiadi Paleolithic site. Furthermore, by combining our magnetostratigraphy and previously published magnetochronology data, a magnetochronological sequence of the early Pleistocene Paleolithic sites in the Nihewan Basin has been established. The chronological sequence implies that early humans may have persistently colonized the high-latitude temperate areas in the eastern Old World, such as the Nihewan Basin, during the Early Pleistocene.

Mineral magnetism to probe into the nature of palaeomagnetic signals of subtropical red soil sequences in southern China

SUMMARY Magnetic polarity stratigraphy has proved to be useful in dating of both marine and terrestrial sedimentary sequences over the world. However, the reliability of magnetostratigraphic results of red soil sequences in subtropical southern China has been found to be variable in different regions. To probe into the capabilities of recording magnetic polarity stratigraphy in the red soils, three red soil sequences have been selected for detailed mineral magnetic, petrographic and/or palaeomagnetic analyses. These include the Xuancheng and Qiliting sequences, which are located in the lower reaches of the Yangtze River and the Damei sequence in the Bose Basin near the Tropic of Cancer. Palaeomagnetic results indicate that the Xuancheng sequence has recorded the Brunhes Chron and the late Matuyama Chron, including a short interval probably representing the Santa Rosa geomagnetic event. The Xuancheng and Qiliting sequences have faithfully recorded the palaeogeomagnetic field behaviour while the Damei sequence has failed. Detailed mineral magnetic and petrographic measurements suggest that four magnetic minerals (magnetite, maghemite, haematite and goethite) are contained in the three studied sequences, but the characteristic remanent magnetization (ChRM) carriers are different. For the Xuancheng and Qiliting samples, the ChRM carriers are magnetite and haematite, which are all of detrital origin. However, the ChRMs of Damei samples are carried by pedogenic haematite with an unblocking temperature (TB) of about 630–640 °C, which has overprinted the primary remanence of the Damei red soil deposits. This pedogenic haematite is mainly produced by chemical weathering, which is commonly intensified by the climate of high temperature and rainfall. It further suggests that climatic conditions have a great effect on the nature of palaeomagnetic signals of the red soil sequences. In addition, the red pigment components in the red soils may be used to indicate the degree of remagnetization.

A new Lower Pleistocene archeological site in Europe (Vallparadís, Barcelona, Spain)

Here we report the discovery of a new late Lower Pleistocene site named Vallparadís (Barcelona, Spain) that produced a rich archeological and paleontological sequence dated from the upper boundary of the Jaramillo subchron to the early Middle Pleistocene. This deposit contained a main archeological layer with numerous artifacts and a rich macromammalian assemblage, some of which bore cut marks, that could indicate that hominins had access to carcasses. Paleomagnetic analysis, electron spin resonance-uranium series (ESR-US), and the biostratigraphic chronological position of the macro- and micromammal and lithic assemblages of this layer reinforce the proposal that hominins inhabited Europe during the Lower Pleistocene. The archeological sequence provides key information on the successful adaptation of European hominins that preceded the well-known fossil population from Atapuerca and succeeded the finds from Orce basin. Hence, this discovery enables us to close a major chronological gap in the early prehistory of Iberia. According to the information in this paper and the available data from these other sites, we propose that Mediterranean Western Europe was repeatedly and perhaps continuously occupied during the late Matuyama chron.

Evidence for the earliest Pleistocene hominid activity in the Nihewan Basin of northern China

The Nihewan Basin in North China contains the densest concentration of early Pleistocene Paleolithic sites outside Africa. This paper introduces a new archaeological site complex at Madigou (MDG) that was systematically excavated from 2011 to 2014 in the northeastern part of the Nihewan Basin. The site contains fossils and well-preserved stone artefacts in fluvio-lacustrine sediments. Our magnetostratigraphic results situate the MDG sedimentary sequence in the early Brunhes normal chron and the late Matuyama reverse chron, including the Jaramillo normal subchron. The MDG artifact layers are positioned within the pre-Jaramillo Matuyama chron, with an estimated age of ca. 1.2 Ma, close to the onset of Mid-Pleistocene climate transition. The MDG core and flake technology includes bipolar flaking of siliceous dolomite cobbles, and freehand flaking of chert and brecciated chert block fragments. Mammalian fauna and pollen compositions indicate that the MDG hominins lived in an open habitat varying from lightly-wooded grassland to an ecosystem dominated by sparse steppe near the shore of the Nihewan paleolake. Our combined results in the fields of archaeology, paleontology, palynology and magnetochronology suggest that innovations in technological behavior may correlate with adaptations to high environmental variability during the start of Mid-Pleistocene climate transition.

Late Matuyama climate forcing on sedimentation at the margin of the southern Alps (Italy)

Abstract The Pleistocene history of climate control on sedimentation in the Southern Alps–Po Plain system, northern Italy, was reconstructed using an integrated magnetostratigraphic, palynological, and petrographical approach on a 47-m-deep core. The core mainly consists of lacustrine sediments pertaining to the Bagaggera sequence, deposited at the foothills of the Southern Alps during the late Matuyama subchron (0.99–0.78 Ma). At that time, climate worsened globally and locally it caused the progradation of an alluvial fan unit onto the nearby Po Plain, triggering lake formation by damming of a tributary valley. These new data are used in conjunction with data from the literature to highlight and track the effects of climate forcing on sedimentation during the late Matuyama subchron in different orographic and geodynamic settings of the Southern Alps–Po Plain system as part of the greater Alpine area. We found that the episodes of alluvial fan and braidplain progradation observed in the southern foreland of the Alps during the late Matuyama global cooling seem broadly synchronous with the deposition of most of the so-called Gunz and Alterer Deckenschotter deposits in the northern forelands of the Alps as well as with the first major waxing of the Alpine valley glaciers, possibly around the Marine Isotope Stage 22 (∼0.87 Ma).

Geomagnetic anomalies recorded in L9 of the Songjiadian loess section in southeastern Chinese Loess Plateau

Detailed magnetostratigraphic and rock magnetic investigations on L8-S12 of the Songjiadian loess section in the Sanmenxia area, southernmost margin of the Chinese Loess Plateau were conducted in this study. Matuyama/Brunhes (M/B) boundary occurred at the bottom of the loess unit L8. The top and bottom boundaries of the Jaramillo polarity subchron are found in the middle of L10 and the bottom of L12, respectively. Magnetic fabric of the loess layers maintains the original depositional features and the recorded remanent magnetization analysis indicates little post-deposition disturbance experienced. In late Matuyama chron, two anomalies of geomagnetic field have been detected in L9. Our data demonstrated that these recorded anomalies were less likely a result of remagnetization, but more possibly the signature of geomagnetic excursions occurred, named SJD1 and SJD2. It is calculated that the midpoint ages of SJD1 and SJD2 are 0.917 Ma and 0.875 Ma, respectively, and the time-interval between the two events approximates 12 ka. Chronologically, SJD1 is close to the Santa Rosa (0.922 Ma) and SJD2 corresponds to the Kamikatsura (0.886 Ma) excursions. In consistence with previous studies, the geomagnetic field was weakened during these events.

Chronology of the transition from a spreading ridge to an accretional seamount in the Marsili backarc basin (Tyrrhenian Sea)

AbstractInversion of new high‐resolution magnetic data from the Marsili seamount and the surrounding basin in the Tyrrhenian Sea reveals NNE–SSW magnetization stripes ranging from the Matuyama chron to the Brunhes chron, including the short positive Jaramillo subchron. The detailed magnetic chronology shows that from the late Matuyama (1.77 Ma), the average half spreading rate was about 1.5 cm yr−1, with a slight decrease between the Jaramillo and the Brunhes events, when the growth of the volcanic edifice overcame lateral spreading. Analysis of spreading rate and volume of erupted lava indicates that at the beginning of the Jaramillo subchron (1.07 Ma), the Marsili basin evolved from pure horizontal spreading to a superinflated seamount as a consequence of tearing of the Ionian slab. Our data give us a snapshot of the geodynamic transition from an active backarc spreading phase to the vertical accretion of the seafloor because of a radical change in the subduction dynamics.