Josep M. Parés

Use of red ochre by early Neandertals

The use of manganese and iron oxides by late Neandertals is well documented in Europe, especially for the period 60–40 kya. Such finds often have been interpreted as pigments even though their exact function is largely unknown. Here we report significantly older iron oxide finds that constitute the earliest documented use of red ochre by Neandertals. These finds were small concentrates of red material retrieved during excavations at Maastricht-Belvédère, The Netherlands. The excavations exposed a series of well-preserved flint artifact (and occasionally bone) scatters, formed in a river valley setting during a late Middle Pleistocene full interglacial period. Samples of the reddish material were submitted to various forms of analyses to study their physical properties. All analyses identified the red material as hematite. This is a nonlocal material that was imported to the site, possibly over dozens of kilometers. Identification of the Maastricht-Belvédère finds as hematite pushes the use of red ochre by (early) Neandertals back in time significantly, to minimally 200–250 kya (i.e., to the same time range as the early ochre use in the African record).

The Vallesian mammal succession in the Vallès-Penedès basin (northeast Spain): Paleomagnetic calibration and correlation with global events

Abstract The integrated lithostratigraphic, biostratigraphic and magnetostratigraphic study of new and classical alluvial fan sequences in the Valles-Penedes Basin (northeast Spain, Western Mediterranean) enabled a considerable refinement of the Vallesian mammalian succession in this basin and its correlation with the Magnetic Polarity Time Scale. Up to 12 new sections were logged and sampled in a search of mammal remains and a paleomagnetic analysis was carried out. The correlation among these sections was based on the small mammal content and the succession of magnetozones, enabling the establishment of four main composite sections (Les Fonts, Montagut, Terrassa and Viladecavalls). As a result, the Vallesian in the Valles-Penedes Basin appears punctuated by four main mammalian events, which coincide with the appearance of the genera Hipparion, Cricetulodon, Progonomys and Rotundomys. The Hipparion event did not coincide with any further change in the associations of small and large mammals. The dispersal of the cricetid Cricetulodon, in its turn, involved the first set of extinctions in the Vallesian, affecting the rodent and carnivore and artiodactyl associations. The main break during the Vallesian coincided with the dispersal of the murids of the genus Progonomys and implied a sudden drop in the diversity of the rodent and artiodactyl species of warm wet-forested affinities. This phase is characterized by the association of the murid Progonomys and the cricetid Cricetulodon and includes the last record of hominoids in the basin. The replacement of Cricetulodon by the sigmodont cricetid Rotundomys was associated with the entry of some typical early Turolian species. According to the correlation established, it is concluded that the FAD of Hipparion in the Valles-Penedes Basin is dated at 11.1 Ma, at the base of Chron C5r.1n. This data is congruent with other datings in Northern Africa and Eastern Europe, suggesting the isochrony of this event in the Mediterranean regions. The Cricetulodon FAD is dated to 10.4 Ma, in Chron C5n. The Progonomys dispersal, coincident with the late Vallesian Crisis, is dated at 9.7 Ma, in Chron C4Ar.3r. The Rotundomys FAD is dated at 9.2–9.3 Ma, in the upper part of Chron C4Ar.1n. The Vallesian mammal bioevents affected the peri-Mediterranean zones, including Northern Africa, and other regions in Northern and Western Eurasia. These paleofaunistic changes were caused by temperature descent from subtropical to warm-temperate conditions as well as by changes in the aridity balance and seasonality. This climatic evolution was the result of the interplay of diverse global events (cooling of the high latitude regions, growing of the Antarctica ice sheet, and enhancement of the thermohaline oceanic circulation) and of large-scale tectonic and paleogeographic processes (surface uplift of the Himalayas, the Tibetan Plateau and other tectonic reliefs, closing of gateways between the Mediterranean marine regions and the World Ocean). The magnetobiochronology resulting from the study of the Western Valles sequences suggests a close chronological correlation between some of these global and regional processes and the Vallesian bioevents recorded.

Magnetostratigraphy of the Vallesian (late Miocene) in the Vallès-Penedès Basin (northeast Spain)

The magnetostratigraphic analysis of the late Miocene continental deposits from the Valles-Penedes Basin, combined with its well-documented fossil mammal record, has provided a well-resolved chronology for the upper basin infill. The study is based on the biostratigraphic and magnetostratigraphic cross-correlation of 12 sections throughout the alluvial sequences in the western Valles area. The biostratigraphic framework consists of 21 mammal localities corresponding to the Mammal Neogene MN9 and MN10 units. The composite magnetic polarity sequence is based on 400 paleomagnetic sites. Correlation with the Geomagnetic Polarity Time Scale (GPTS) has led to an absolute dating of the faunal events and a precise chronostratigraphy of the Vallesian mammal stage in its type area. The Hipparion First Appearance Datum (FAD), at the MN8MN9 boundary, is dated at 11.1 Ma in the Valles-Penedes Basin. This age, compared to other radiometrically dated localities in Europe, North Africa and Turkey, is consistent with an isochronous dispersal of this equid through the Mediterranean region. A possible isochrony at a larger geographical scale (Old World, Mesogea) must await more reliable ages of the Hipparion FAD in Asia and Africa. The Cricetulodon FAD (MN9aMN9b boundary) is dated to 10.4 Ma, in chron C5n. The Progonomys FAD (MN9MN10 boundary), corresponding to the intra-Vallesian faunal crisis, is dated at 9.7 Ma (C4Ar.3r). The Vallesian spans 2.4 Myr, from 11.1 Ma (C5r.1n) to 8.7 Ma (C4An) and correlates to the early Tortonian.

Calibration of the late Pliocene-early Pleistocene transition in the continental beds of the Guadix-Baza basin (southeastern Spain)

In this paper a survey of the correlation between magnetic polarity and the mammalian succession in the Plio-Pleistocene sequence of the Guadix-Baza basin is presented. In this basin a complete continental sequence from the early Pliocene to the Middle Pleistocene is present, allowing the correlation of mammalian biozones with the geomagnetic polarity scale. Two sections of the Baza sector of the basin have been analyzed in order to calibrate the Pliocene-Pleistocene transition: the Galera (middle Pliocene to early Pleistocene) and the Orce (late Pliocene to early Pleistocene). It is concluded that the boundary between the MN 15 (late Ruscinian) and the MN 16 (early Villanyian) is placed between the 2An. 3n chron and the 2An. In subchron. The late Villanyian (MN 17) extends up to the upper part of chron 2r. 1r. The entry of the Pleistocene marker Allophaiomys pliocaenicus can be placed within subchron 2n (Olduvai).

LATE PLIOCENE CONTINENTAL MAGNETOCHRONOLOGY IN THE GUADIX-BAZA BASIN (BETIC RANGES, SPAIN)

Abstract The late Pliocene shallow lacustrine sequences in the Guadix-Baza basin (Betic Ranges, southeast Spain) are a suitable setting for mammal chronology because of the abundance of rich, mammal-bearing sites. Stratigraphic superposition of late Ruscinian and Villanyian vertebrate fossils makes the Galera Section very appropriate for magnetostratigraphic dating. Sediments are characterized by a weak but measurable magnetization predominantly carried by magnetite. Other remanence carriers, such as iron sulphides and hematite, may be significant only in some particular lithologies, such as dark palustrine organic silts and red alluvial beds, respectively. Direct correlation of the Galera Section to the geomagnetic polarity time scale provides a reliable dating of the late Ruscinian and Villanyian mammal units. The Ruscinian/Villanyian boundary (MN15/MN16) is found to occur in the lower Gauss chron, and approximately correlates to the 3.3 Ma cooling event observed in stable-isotope and planktonic foraminifera deep sea records. The earliest occurrence of late Villanyian assemblages (MN17) in the lower part of the Matuyama chron allows dating of the early/late Villanyian boundary (MN6/MN17) to approximately 2.4–2.6 Ma. Based on the presence of late Villanyian assemblages underlying the base of the Olduvai chron, a maximum age of 1.95 Ma (top of C2r) is attributed to the Villanyian/Biharian (MN17/MmQ) boundary. A 300 kyr sedimentary gap in the Galera Section is suggested to correlate with a probable early Villanyian hiatus, an hypothesis that agrees with the absence of fossils of this age elsewherein the Baza Formation.

Further evidence for inclination shallowing in red beds

Red beds and related shallow marine siliciclastic sediments within the extensional Catalan Neogene basins offer a unique opportunity to study the relationship between sediment anisotropy, remanence acquisition and inclination shallowing. On the basis of the dominant fabric features, sedimentary facies are grouped into laminated, massive and bioturbated. The bulk susceptibility appears to be dominated by paramagnetic phyllosilicates and clay minerals. The magnetic susceptibility fabric is dominantly foliated while the degree of anisotropy is very variable and is dependent on the facies type. Strong foliation dominates in the laminated sediments whereas weak anisotropy characterizes the bioturbated and massive mass-flow facies. Moreover, we observe a correlation between facies type and remanence inclination. The undisrupted thinly laminated facies provides the most biased inclination values: 20° as opposed to 60° of the expected geomagnetic field. Steeper inclinations are reported from bioturbated muds, while the best record of the geomagnetic inclination is found in the weakly anisotropic mass flow deposits.

Calibration of the Early-Middle Pleistocene transition in the continental beds of the Guadix–Baza Basin (SE Spain)

Abstract The magnetostratigraphic and palaeontologic studies carried out in two sections in the Guadix–Baza Basin (SE Spain) have enabled an accurate calibration of the Early-Middle Pleistocene boundary in the continental beds of this basin. The palaeontological record (rodents) in the Cortes de Baza section indicates an age ranging from the earliest Pleistocene (latest Villanyian or early Biharian) to the late Early Pleistocene (late Biharian). The whole Cortes de Baza Section is placed in a reversed magnetic interval identified as the upper part of the Matuyama Chron. In the Guadix–Baza Basin, the Middle Pleistocene (early Toringian) was already known at the locality of Cullar–Baza I, but new studies in the area have resulted in the recognition of Early Pleistocene deposits in the lower part of the section. Thus, the locality of Cullar–Baza B is placed in a reversed magnetozone correlated with the uppermost Matuyama, while the locality of Cullar–Baza C is placed in a normal magnetozone correlated to the lower Bruhnes Epoch. Therefore, the Biharian–Toringian boundary (based on the presence of Arvicola cantiana ) falls well within the Bruhnes epoch. This result is consistent with what is found in other Early–Middle Pleistocene sections of Spain (Atapuerca Gran Dolina).

Magnetostratigraphic characterization of a thick Lower Pleistocene lacustrine sequence from the Baza Basin (Betic Chain, Southern Spain)

Abstract The magnetic polarity stratigraphy from a lacustrine sequence of the Baza Basin (Betic Chain, Southern Spain) has been interpreted as having a Lower Pleistocene age. Fifty-nine paleomagnetic sites have been obtained and a set of 179 specimens has been demagnetized with both thermal and alternating field procedures. Several magnetic parameters, that depend on the lithology, have been obtained. The characteristic remanent magnetization polarity has been unambiguously recovered over the whole sequence. The materials studied span chron 1r.2, located in the upper Matuyama epoch. This allows the placement of the faunas studied, ranging from the Late Villanyian to the Late Biharian, in the magnetic polarity time scale (MPTS). This work also proves that magnetostratigraphy can be established in lacustrine sediments even with extremely low magnetic intensities.

Iberian Triassic paleomagnetism revisited: Intraplate block rotations versus polar wandering

A paleomagnetic study of over 220 samples, obtained from 21 sites from Triassic redbeds in the Algarve (S Portugal) and La Meseta (SE Spain), yields two paleomagnetic poles at lat = 62°N,lon = 202°E, A95 = 9 and lat=54°N, lon=178°E, A95=7 respectively. The Algarve paleopole reflects a rotation associated with the Alpine evolution of the Iberian Atlantic margin. A comparison of the La Meseta pole with other data indicates a progressive clockwise rotation of the Eurasian Plate from the Late Paleozoic to Middle Triassic, followed by rapid drift until the Upper Triassic. This late Triassic drift event may be related to the opening and spreading of the Tethys towards the west.

Fly ash content and distribution in lake sediments around a large power station: inferences from magnetic susceptibility analysis.

The bulk magnetic susceptibility of sediments from artificial and natural lakes around a large coal-fired power station in NE Spain has been measured. Higher magnetic susceptibility values are found in lake sediments located SE of the power station. This distribution of susceptibility values is compatible with environmental and meterological studies of emissions from the power station, which indicate a dominant SE plume direction. Mineralogical studies, by means of X-ray diffraction and scanning electron microscopy, show that the highest susceptibility values found in the sediments are caused by magnetic iron spinels in the fly ash that is transferred to the environment by the power station particulate emissions. After the quantitative mineralogical studies of fly ash, two different methods of fly ash content determination in the sediments have been devised, showing very similar results. The low background magnetic susceptibility of the sediments in the study area and the high susceptibility resulting from the input of magnetic fly ash particles allows both delimitation of the polluted area around the power station, and quantification of the fly ash input into the natural sediments.