The geodynamic and limnological evolution of Balkan Lake Ohrid,possibly the oldest extant lake in Europe

Studies of the upper 447 m of the DEEP site sediment succession from central Lake Ohrid, Balkan Peninsula, North Macedonia and Albania provided important insights into the regional climate history and evolutionary dynamics since permanent lacustrine conditions established at 1.36 million years ago (Ma). This paper focuses on the entire 584-m-long DEEP sediment succession and a comparison to a 197-m-long sediment succession from the Pestani site ~5 km to the east in the lake, where drilling ended close to the bedrock, to unravel the earliest history of Lake Ohrid and its basin development. ²⁶Al/¹⁰Be dating of clasts from the base of the DEEP sediment succession implies that the sedimentation in the modern basin started at c. 2 Ma. Geophysical, sedimentological and micropalaeontological data allow for chronological information to be transposed from the DEEP to the Pestani succession. Fluvial conditions, slack water conditions, peat formation and/or complete desiccation prevailed at the DEEP and Pestani sites until 1.36 and 1.21 Ma, respectively, before a larger lake extended over both sites. Activation of karst aquifers to the east probably by tectonic activity and a potential existence of neighbouring Lake Prespa supported filling of Lake Ohrid. The lake deepened gradually, with a relatively constant vertical displacement rate of ~0.2 mm a⁻¹ between the central and the eastern lateral basin and with greater water depth presumably during interglacial periods. Although the dynamic environment characterized by local processes and the fragmentary chronology of the basal sediment successions from both sites hamper palaeoclimatic significance prior to the existence of a larger lake, the new data provide an unprecedented and detailed picture of the geodynamic evolution of the basin and lake that is Europe’s presumed oldest extant freshwater lake.     

The Homo habitat niche: using the avian fossil record to depict ecological characteristics of Palaeolithic Eurasian hominins

Although hardly applied to human palaeoecology, bird fossils offer a unique opportunity for quantitative studies of the hominin habitat. Here we reconstruct the Homo habitat niche across a large area of the Palaearctic, based on a database of avian fauna for Pleistocene sites. Our results reveal a striking association between Homo and habitat mosaics. A mix of open savannah-type woodland, wetlands and rocky habitats emerges as the predominant combination occupied by Homo across a wide geographical area, from the earliest populations of the Lower Palaeolithic to the latest hunter-gatherer communities of the Upper Palaeolithic. This observation is in keeping with the view that such landscapes have had long standing selective value for hominins.     

The distribution of late-Quaternary woody taxa in northern Eurasia: evidence from a new macrofossil database

We present a database of late-Quaternary plant macrofossil records for northern Eurasia (from 23° to 180°E and 46° to 76°N) comprising 281 localities, over 2300 samples and over 13,000 individual records. Samples are individually radiocarbon dated or are assigned ages via age models fitted to sequences of calibrated radiocarbon dates within a section. Tree species characteristic of modern northern forests (e.g. Picea, Larix, tree-Betula) are recorded at least intermittently from prior to the last glacial maximum (LGM), through the LGM and Lateglacial, to the Holocene, and some records locate trees close to the limits of the Scandinavian ice sheet, supporting the hypothesis that some taxa persisted in northern refugia during the last glacial cycle. Northern trees show differing spatio-temporal patterns across Siberia: deciduous trees were widespread in the Lateglacial, with individuals occurring across much of their contemporary ranges, while evergreen conifers expanded northwards to their range limits in the Holocene.     

Lateglacial environmental and climatic changes at the Maloja Pass,Central Swiss Alps,as recorded by chironomids and pollen

Chironomids and pollen were studied in a radiocarbon-dated sediment sequence obtained from a former lake near the Maloja Pass in the Central Swiss Alps (1865 m a.s.l.) to reconstruct the Lateglacial environment. Pollen assemblages imply a vegetation development around the Maloja Pass from shrub tundra at the beginning of the Allerød to coniferous forest during the early Holocene with a lowering of the timberline during the Younger Dryas. Chironomid assemblages are characterized by several abrupt shifts in dominant taxa through the Lateglacial. The occurrence of taxa able to survive hypoxia in the second part of the Allerød and during the Preboreal, and their disappearance at the onset of the Younger Dryas cold phase suggest summer thermal stratification and unfavourable hypolimnetic oxygen conditions in the palaeo-lake during the warmer periods of the Lateglacial interstadial and early Holocene. Mean July air temperatures were reconstructed using a chironomid-temperature transfer function from the Alpine region. The pattern of reconstructed temperature changes agrees well with the Greenland δ¹⁸O record and other Lateglacial temperature inferences from Central Europe. The inferred July temperatures of ca 10.0 °C during most of the Allerød were slightly lower than modern values (10.8 °C) and increased up to ca 11.7 °C (i.e., above present-day values) at the end of the Allerød. The first part of the Younger Dryas was colder (ca 8.8 °C) than the second part (ca 9.8 °C). During most of the Preboreal, the temperatures persisted within the limits of 13.5–14.5 °C (i.e., ca 3 °C above present-day values). The amplitudes of temperature changes at the Allerød–Younger Dryas–Preboreal transitions were ca 3.5–4.0 °C. The temperature reconstruction also shows three short-lived cooling events of ca 1.5–2.0 °C, which may be attributed to the centennial-scale Greenland Interstadial events GI-1d and GI-1b, and the Preboreal Oscillation.     

Pollen‐inferred palaeoclimate reconstruction in the Alps during the Lateglacial and the early Holocene: how to estimate the effect of elevation and local parameters

The modern analogue technique (MAT) was applied to six pollen sequences from the Belledonne Massif (northwestern French Alps) to estimate the effect of altitude and local parameters on pollen‐based climate reconstruction during the Lateglacial and the early Holocene. The six sites (Le Vivier (345 m a.s.l.), Les Etelles (700 m a.s.l.), La Coche (980 m a.s.l.), Montendry (1330 m a.s.l.), Le Grand Leyat (1660 m a.s.l.), La Gouille (1800 m a.s.l.)) are located in different vegetation belts (mixed deciduous woods, conifer woods, alpine pastures with maple). The main vegetation changes in the past are recorded at each site. The evolution of four climate parameters (coldest month temperature, warmest month temperature, mean annual temperature, annual precipitation) was quantitatively inferred from pollen data using MAT. The curves obtained were compared to the Les Etelles site, which was the least affected by non‐local pollen transport. The results show consistent trends for the climate parameters reconstructed at the different sites. However, the reconstruction does not indicate a decrease in temperature values related to the increasing elevation. Difficulties in reconstructing the altitudinal variations of climate parameters from pollen data during the periods studied are discussed and perspectives for improvement are considered. Copyright © 2009 John Wiley & Sons, Ltd.     

Reply to Molina-Garza et al. (2019) “Discussion of: Ortega-Flores et al. (2018) provenance analysis of Oligocene sandstone from the Cerro Pelón area,southern Gulf of Mexico”

ABSTRACT

The origin of the Oligocene turbidites from the Cerro Pelón area in south Gulf Mexico proposed by Ortega-Flores et al. (2018) is in disagree with the interpretations made by Molina-Garza et al. (2019), which main criticism is based on U-Pb ages of detrital zircons from the matrix of a conglomerate unit, which they refer to as ‘Nanchital Conglomerate’, as well as on the presence of limestone, gabbros, and mafic protolith-derived clasts. Molina-Garza et al. (2019) basically interpret the Nanchital Conglomerate as Miocene in age, which was sourced mainly from metamorphic complexes including their sedimentary covers located to the west and south of the Cerro Pelón area. For some reason, Molina-Garza et al. (2019) suppose that the Nanchital Conglomerate should have the same provenance sources that the Oligocene turbidites from Cerro Pelón area, reported by Ortega-Flores et al. (2018). Based on the foregoing, we strongly disagree with Molina-Garza et al. (2019) considering that, from the beginning, they intend to compare two units of different age. Additionally, the scarce data reported from both the matrix and the clasts of the Nanchital Conglomerate are not determinant for interpreting the provenance of this conglomeratic unit and subsequently, to consider the same rock sources from the Oligocene through Miocene time.     

Traffic-related platinum group elements (PGE) in soils from Mexico City

The first evaluation of the distribution of platinum group elements (PGE) derived from automobile catalytic converters in urban soil samples in Mexico City was carried out. There are more than four millions cars in Mexico City and, at the present time, one third of them have catalytic converters. PGE concentrations in soils exposed to high traffic densities exceed the natural background values by upto two orders of magnitude and are directly influenced by traffic conditions. The highest concentrations of Pt, Pd and Rh in the analyzed samples are about 300, 70 and 40 μg/l, respectively. Although the PGE concentrations found in soil samples are relatively low, they represent an accumulation of only 10 yr. It is likely that the use of catalytic converters will dramatically change the distribution of these metals in the urban environment in the next decades.