The Isthmus of Panama as a Crossroad for Prehistoric Migration of Domesticated Plants

For thousands of years, Indian tribes have gathered, selected, domesticated and spread useful plants over the whole American continent while mostly practicing shifting forms of horti-agriculture. It has been argued that origin and domestication of New World crops could be traced back to essentially two independent, narrowly circumscribed core regions, (i.e. Vavilov's genecentres) one in the highlands of Mexico and the other in the Andes of Peru. Those alleged centers of origin and genetic diversity have been synchronized with the main cradles of American agriculture. Based on long periods of research work in South America, we disagree with this opinion which is maintained primarily by anthropologists, sociologists and ethnologists. Except for marginal desert and mountain environments, there are no real biogeographical restrictions for plant domestication. Apparent geographical barriers, like the Darien gap, did not represent insurmountable hindrances for the diffusion and migration of useful species in the hands of indigenous peoples.     

Wintertime European circulation patterns during the Late Maunder Minimum cooling period (1675–1704)

Summary The North Atlantic and Western Europe regions comprise a key area to study climate variations in the form of cold relapses which may be a possible manifestation of reduced ocean circulation. By using multi-proxy data of the late Maunder Minimum period, temperature and precipitation distribution during winter was studied in connection with atmospheric circulation, with the goal of obtaining an insight into the feedbacks between ocean, sea ice and temperature. The study shows that the Late Maunder Minimum was a relatively cool and dry period with low ocean temperatures and a large sea ice extent, although Alpine glaciers did not grow during this time. A comparison of the winter weather types of the three decades from 1675 to 1704 with the recent 30 year period (1961–1990) shows that the late Maunder Minimum was characterized by strong sea level pressure reversals with high pressure centres over Northern or Northwestern Europe and large outbreaks of northeasterly cold continental air.With 3 Figures     

TRANSALP—Cross-line recording during the seismic reflection transect in the Eastern Alps

Cross-line recording formed a companion experiment of the TRANSALP seismic reflection transect through the Eastern Alps, conducted by partner institutions from Austria, Germany and Italy in three field campaigns in the period fall 1998 to fall 1999. Besides of the originally expected three-dimensional control for the north–south running main transect, additional information on seismic anisotropy and alternative images of crucial parts of the main transect could be gained.Conventionally processed sections along N–S running common-midpoint (CMP) binning lines confirm and strengthen the predominance of midcrustal reflective structures of the ‘Sub-Tauern-Ramp’ beneath and south of the Tauern Window. Velocity analysis of the first arrivals exhibit about 10% higher velocities in east–west propagating P-waves, compatible with texture-dominated rock anisotropy, recorded on cross-lines at the Tauern Window. Pre-stack depth migration of cross-line recordings shows dominant south dip of the Sub-Tauern-Ramp with easterly dip components and a sub-horizontal root zone of the Sub-Dolomites-Ramp.     

Predicting the deforestation-trend under different carbon-prices

Background  

Global carbon stocks in forest biomass are decreasing by 1.1 Gt of carbon annually, owing to continued deforestation and forest degradation. Deforestation emissions are partly offset by forest expansion and increases in growing stock primarily in the extra-tropical north. Innovative financial mechanisms would be required to help reducing deforestation. Using a spatially explicit integrated biophysical and socio-economic land use model we estimated the impact of carbon price incentive schemes and payment modalities on deforestation. One payment modality is adding costs for carbon emission, the other is to pay incentives for keeping the forest carbon stock intact.     

New maturation parameters based on naphthalene and phenanthrene isomerization and dealkylation processes aimed at improved classification of crude oils (Southeastern Pannonian Basin,Serbia)

Aiming at improved classification of crude oils, naphthalene and phenanthrene isomerization and dealkylation processes were considered in detail as a possible basis to select new maturation parameters. Crude oils originating from the Banat depression (Southeastern Pannonian Basin, Serbia) were used as objects of our study. Four new maturation parameters are proposed in this paper. Two of them are based on dimethylnaphthalene (DMN) and trimethylnaphthalene (TMN) isomerization reactions: DN_x = (1,3-DMN + 1,6-DMN)/(1,4-DMN + 1,5-DMN) and TNy = (1,3,6-TMN + 1,3,7-TMN)/(1,3,5-TMN + 1,4,6-TMN). The other two are based on demethylation of dimethyl-and trimethylphenanthrenes (DMP and TMP) into corresponding methylphenanthrenes (MP): MDR = ΣMP/ΣDMP and MTR = ΣMP/ΣTMP. The new parameters’ advantageous applicability was demonstrated by factor analysis, comparing them with maturation parameters known from literature. The text was submitted by the authors in English.     

Traces of historical tropical cyclones and tsunamis in the Ashburton Delta (north‐west Australia)

Although the north‐western coast of Western Australia is highly vulnerable to tropical cyclones and tsunamis, little is known about the geological imprint of historic and prehistoric extreme wave events in this particular area. Despite a number of site‐specific difficulties such as post‐depositional changes and the preservation potential of event deposits, both tropical cyclones and tsunamis may be inferred from the geomorphology and the stratigraphy of beach ridge sequences, washover fans and coastal lagoons or marshes. A further challenge is the differentiation between tsunami and storm deposits in the geological record, particularly where modern deposits and/or historical reports on the event are not available. This study presents a high‐resolution sedimentary record of washover events from the Ashburton River delta (Western Australia) spanning approximately the last 150 years. A detailed characterization of event deposits is provided, and a robust chronostratigraphy for the investigated washover sequence is established based on multi‐proxy sediment analyses and optically stimulated luminescence dating. Combining sedimentological, geochemical and high‐resolution optically stimulated luminescence data, event layers are assigned to known historical events and tropical cyclone deposits are separated from tsunami deposits. For the first time, the 1883 Krakatoa and 1977 Sumba tsunamis are inferred from sedimentary records of the north‐western part of Western Australia. It is demonstrated that optically stimulated luminescence applied in coastal sedimentary archives with favourable luminescence characteristics can provide accurate chronostratigraphies even on a decadal timescale. The results contribute to the data pool of tropical cyclone and tsunami deposits in Holocene stratigraphies; however, they also demonstrate how short‐lived sediment archives may be in dynamic sedimentary environments.     

Contrasted Late Glacial and Holocene hydrology of Sarliève paleolake (France) from sediment geometry and detrital versus biochemical composition

Since the end of the Last Glacial Maximum, hydrology in Europe has been influenced by both climate changes, and since Neolithic times, an increase in human activity. Paleohydrological reconstructions, especially from lake studies, can help identify the respective impact of these two factors. The present work focuses on a lacustrine geosystem, the Sarliève paleolake in the Massif Central (France), in an unusually dry, temperate area. The lake sediment geometry (core drillings, geotechnical methods), and the geochemical and mineralogical characterization of the catchment rocks and soils, and of the lacustrine deposits, indicate major variations in paleohydrology during the last 12,000 years as dated by ¹⁴C, palynology and tephrochronology. In addition, a model quantifying detrital versus biochemical lacustrine components was developed to identify hydrological trends. The data show that the Sarliève area was characterized mainly by remarkably dry conditions, hence sharpening the climatic trends at middle latitudes in Western Europe. Three main hydrological phases are distinguished since the Late Glacial: (1) 13.7–7.5 ka cal BP, a dominant dry climate, with a peak at ca. 8 ka cal BP, leading to a lowstand in water level and unusual mineral authigenesis, zeolite then dolomite, constituting up to 60% of the lacustrine sediments; (2) 7.5 to ca. 5.3 ka cal BP, repeated short-duration hydrological alternations that could have been climate-driven: lowstands in water level with up to 60% biochemical minerals versus higher water levels with <10% biochemical minerals; (3) 5.3 ka cal BP to the Middle Ages (i.e. beginning in the 5th century AD), a hydrological trend towards perennial high water level, with mainly detrital sediments, probably linked to climate evolution, except periods of obvious human-driven drying during the last two millennia.     

Impact of climate variability,drainage and land-cover changes on hemiboreal streamflow

The aim of the study was to determine the effects of climate variability, agricultural land drainage and afforestation of agricultural land on river discharge. The study was conducted in the Vienziemīte stream basin (6 km²), where discharge was monitored on a daily basis during the time period of 1946–2010. In the stream basin, natural afforestation of agricultural land began in the 1950s, and in the mid-1970s artificial drainage systems were installed in all agricultural land (70% of the total basin area). Climate variability and artificial drainage were the main factors observed to be affecting stream discharge. The changes were most evident in annual and seasonal mean, minimum and maximum streamflow. There was no effect of afforestation of agriculture land on stream discharge.