Pollen record and dating of a sediment profile from Ahlequellmoor in Germany

A pollen diagram from the Ahlequellmoor in the Solling area shows the history of vegetation and settlement over the last 7,800 years. In the early Atlantic period mixed deciduous forest with mainly Tilia together with Ulmus and Quercus grew in the area. In the late Atlantic period Quercus became most abundant. Fagus spread in the Sub-boreal period at about 2700 B.C. Since ca. 900 B.C. the Solling was covered by beech forests with some oak. In prehistoric times woodland grazing is indicated. Only in Medieval times are two settlements in the vicinity of the Ahlequellmoor reflected in the pollen diagram. The earlier one is dated to about A.D. 750-1020, and may be connected with the former Monastery of Hethis, which is thought to have existed close to the fen from A.D. 815 to 822. The second Medieval settlement dates to the 11th-12th century. The large-scale woodland destruction of late Medieval and modern times is not clearly visible. The silvicultural measures of the last 200 years are reflected by increasing values of spruce and grassland taxa.

Pollen analysis of a sediment profile from Gabelsee in Germany

The article shows that pollen analysis plays an important role in the prediction of potential settlement areas and, furthermore, can offer a crude determination of settlement duration. Especially when the archaeological data fails to offer a possibility of dating, pollen analysis in connection with 14C can importantly broaden the knowledge base. As in the present case, the results of the Archaeo-Prognosis mapping and the pollen analysis of the Gabelsee are compared and, within this vicinity, confirmend. = Der Beitrag zeigt, dass die Pollenanalyse eine wichtige Rolle für die Vorhersage von potenziellen Siedlungsflächen spielen und darüber hinaus eine grobe Berechnung der Siedlungsdauer bieten kann. Insbesondere wenn die archäologische Datenbasis keine genaue Datierung zulässt, ermöglicht die Pollenanalyse in Verbindung mit der 14C-Datierung eine wichtige Erweiterung der Kenntnisse. Im vorliegenden Fall konnten die Ergebnisse der Archäoprognosekarte mit denjenigen der Pollenanalyse des Gabelsees verglichen und für diesen lokalen Raum bestätigt werden.

Rarefied allelic richness of the ground beetle Abax parallelepipedus in Germany

Although genetic diversity is one of the key components of biodiversity, its drivers are still not fully understood. While it is known that genetic diversity is affected both by environmental parameters as well as habitat history, these factors are not often tested together. Therefore, we analyzed 14 microsatellite loci in Abax parallelepipedus, a flightless, forest dwelling ground beetle, from 88 plots in two study regions in Germany. We modeled the effects of historical and environmental variables on allelic richness, and found for one of the regions, the Schorfheide-Chorin, a significant effect of the depth of the litter layer, which is a main component of habitat quality, and of the sampling effort, which serves as an inverse proxy for local population size. For the other region, the Schwäbische Alb, none of the potential drivers showed a significant effect on allelic richness. We conclude that the genetic diversity in our study species is being driven by current local population sizes via environmental variables and not by historical processes in the studied regions. This is also supported by lack of genetic differentiation between local populations sampled from ancient and from recent woodlands. We suggest that the potential effects of former fragmentation and recolonization processes have been mitigated by the large and stable local populations of Abax parallelepipedus in combination with the proximity of the ancient and recent woodlands in the studied landscapes.

Physical properties of four profiles from the Triassic in Germany

The Norian Steinmergel-Keuper (SMK) represents a low-latitude cyclically-bedded playa system of the Mid-German Basin. We investigated a drilling site (core Morsleben) and sections from marginal positions. Dolomite/red mudstone beds form rhythmic alternations that were associated with varying monsoon activity. Hence, low K/Al ratios of dolomite beds suggest increased chemical weathering of the crystalline hinterland and therefore increased monsoonal rainfall. High K/Al ratios in red mudstone beds reflect increased physical weathering of the hinterlands during dryer periods. Dolomite layers reflect the lake stage (maximum monsoon) while red mudstones indicate the dry phase (minimum monsoon) of the playa cycle. We distinguished five major types of cyclic facies alternations, representing specific facies zones in the playa system. We have implemented spectrophotometry as a tool for high-resolution cyclostratigraphy. The dense sampling increment (up to 1 cm) allows for the recognition of all orbital frequencies. Sediment colour profiles reveal striking hierarchical cycles from semi-precession (SP, 99 kyr) over precession (P, 19.8 kyr) and obliquity (O, 36 kyr) to eccentricity (E1-2 109 kyr; E3, 413 kyr). A significant about 2 Myr-signal is attributed to the longer-term eccentricity E4. One monsoonal (precession) cycle includes two carbonate precipitation events. We propose that stratified mudstone and red mudstone are associated with maximum and minimum monsoon during the transition of the solstices in perihelion and aphelion, respectively. The two carbonate precipitation events were most likely created when equinoxes were in perihelion and aphelion, respectively. A sedimentary semi-precession response cycle is a novel finding for the Norian strata. The obliquity signal is attributed to incoming atmospheric moisture from the northeast of the SMK basin. The E4 cycle controls lake-level changes over long times. Apparently, E4 is responsible whether or not a threshold value is crossed. Bundles of 109 kyr and 413 kyr in red mudstones suggest a dry system with reduced monsoonal activity. In contrast, humid periods reveal thick layers of dolomite beds, indicating that during those intervals the monsoonal activity was strong enough to prevent the playa system from drying out completely.

Pollen record from Muggesfelder See and Plussee in Germany

A basaltic tephra layer consisting of brownish-olive glass shards. and about 0.2 mm thick. was found in cores from four lakes in northwest Germany. According to pollen analysis it was deposited during the early Boreal period (corresponding to about 8700 BP). The petrographic properties. the geochemical composition and the age agree with those of the Saksunarvatn tephra. which was first found on the Faroe Islands. The position of the tephra layer in the pollen stratigraphy and in the absolute time-scale is discussed. Procedures for locating the tephra in other cores are suggested.

Miocene palaeoclimate reconstructions from the North Alpine Foreland Basin in Germany

Early- and Middle-Miocene sediments of the North Alpine Foreland Basin (NAFB) in Southern Germany contain one of the world richest regional records of silicified wood. Here we analyze over 1,000 identifiable samples, belonging to 80 wood anatomical taxa from 61 stratigraphically well-dated localities using principally the Coexistence Approach. The samples investigated originate from fluvial sediments representing periods of intensified surface runoff in the NAFB and therefore represent and provide information pertaining to the wet end-member of the fluctuating climate system. The dry end of the climate system is represented in the profiles either by hiatuses or palaeosoils. The dataset is split into four xylofloras: (I) the Ortenburg xyloflora (Late Ottnangian; ~17.5 to 17.3 Ma) originating from a paratropical evergreen Carapoxylon (Xylocarpus) forest; (II) the Southern Franconian Alb xyloflora (Late Karpatian; 17.0 to ~16.3 Ma) originating from a subtropical semideciduous limestone forest; (III) the upper Older Series xyloflora (Early Badenian; ~16.3 to ~15.3 Ma) originating from a subtropical oak-laurel forest; and (IV) the upper Middle Series xyloflora (Middle Badenian; 14.3 to ~13.8 Ma) originating from a subtropical dry deciduous forest.

Palynology of sediment profiles from 30 lakes in Germany

Dieser Datensatz beinhaltet 70 Pollenprofile und begleitende sedimentologische Daten aus 30 Seen in Deutschland, die im Verlauf der 70er und 80er Jahre vom NlfB gekernt und analysiert wurden. Der Datenatz wurde im Rahmen des im folgenden beschriebenen Teilprojektes des DFG-Schwerpunktprogrammes "Wandel der Geo-Biosphäre" von Prof. Dr. Josef Merkt der wissenschaftlichen Gemeinschaft zur Verfügung gestellt. Im Projekt "Laminierte Seesedimente als Archive für Untersuchungen der Änderungen von Umweltbedingungen während Spätglazial und Holozän" wurden die laminierten Abschnitte von Sedimentprofilen aus oberschwäbischen, nordschweizerischen und norddeutschen Seen, die die letzten 15 000 Jahre umfassten, mikroskopisch ausgewertet. Ziel war es für Deutschland eine jahrgenaue Chronologie nach Kalenderjahren aufzustellen. Poster: Kleinmann, A, Merkt, J, Müller, H, Küster, H (1998) Holocene lake-level changes in Germany. Institute of Geobotany, University Hannover & Geological Survey of Lower Saxony, Hannover. (pdf hdl:10013/epic.31687.d001 280kB) Einführung: Die meisten Seen in Deutschland bestehen seit mehr als 15 000 Jahren und sind seit Jahrtausenden attraktiv für menschliche Besiedlung. In den Seeablagerungen ist die Geschichte der Umwelt nahezu ungestört und hoch aufgelöst konserviert. Pflanzliche und tierische Reste, wie z. B. Blütenstaub, Birkenfrüchte, Bucheckern, Algen, Wasserflöhe, Käfer, Muschelkrebse und Rädertierchen können Auskunft über die Entwicklung der Flora und Fauna, über Wärme- und Kälteperioden seit der letzten Eiszeit bis heute geben. Weitere Zeugen sind z.B. klastischer Eintrag (wie Sand), vulkanische Aschen, chemische Ausfällungen und eine jahreszeitliche Schichtung, die nur unter Sauerstoffausschluß entsteht. Ist der Seegrund belüftet, leben dort Tiere, die die oberen Zentimeter des Seebodens zur Nahrungssuche durchwühlen und dabei diese Schichtung zerstören. Ist der Seegrund ganzjährig unbelüftet, bleiben die klastischen Partikel, die organischen Reste, die chemischen Fällungen wie Siderit und Kalzit in der Reihenfolge liegen wie sie abgesunken sind. Die Reihenfolge spiegelt den Ablauf der Jahreszeiten wider: Goldalgen fallen im Frühjahr und die Mehrheit der Kieselalgen im Frühsommer und Sommer auf den Seeboden. Eisenkarbonat und Kalk werden im Sommer ausgeschieden, die klastischen und organischen Partikel sedimentieren im Winter. Die Jahresschichten liefern das zeitliche Gerüst in dem sich Klimaumschwünge, Seespiegeltiefstände und andere Ereignisse der Paläoumwelt jahrgenau fassen lassen. Auch die Landnutzung durch den Menschen ist aus Seeablagerungen abzulesen, wie z. B. erster Ackerbau, Rodungshochphasen in der Römerzeit und im Mittelalter, Aufforstung Anfang des 19. Jahrhunderts, bronzezeitliche und jüngere Erzverhüttungen, Industrialisierung, sogar Atombombentests und das Reaktorunglück von Tschernobyl 1986. Diese deuten das umwelt-wissenschaftliche Potential der Seesedimente an. Wesentliche Antworten, die in Seesedimenten stecken und entschlüsselt werden, sind die auf Fragen nach Klimaänderungen und ihren Folgen. Neben den bekannten vulkanischen Aschenlagen Laacher Tuff aus der Eifel, Saksunarvatn Tuff aus Island und Kilian/Vasset Tuff aus dem Massif Central werden weitere gesucht, da sie trennscharfe Leithorizonte sind und zur absoluten zeitlichen Korrelation von See zu See dienen. Daneben können regional unterschiedliche Vegetationsentwicklungen über isochrone Tephralagen einander zugeordnet werden. Mit der Erfassung möglichst vieler Sedimentparameter können Kriterien gefunden werden, mit denen die natürlichen von den anthropogenen Umweltveränderungen zu unterscheiden sind. Klimatisch unruhige Zeitabschnitte wie der Übergang Alleröd/Jüngere Tundrenzeit vor 12700 Kalenderjahren, der Übergang Spätglazial/Holozän vor 11560 Kalenderjahren und die 120 Jahre später einsetzende vorübergehende Abkühlung, die Rammelbeekphase, wurden analysiert, um Dauer, Verlauf und Folgeerscheinungen kennenzulernen. Als Methoden wurden eingesetzt: Mikrofaziesanalyse mit Dünnschliffen, Pollenanalyse, Mikrofaunauntersuchungen, anorganisch und organisch geochemische Analysen, Isotopenanalyse (delta13C, delta18O, AMS an terrestrischen Makroresten).

Pollen and diatom analysis on varved sediments in Lake Jues (Harz Mountains, Germany)

Studies combining sedimentological and biological evidence to reconstruct Holocene climate beyond the major changes, and especially seasonality, are rare in Europe, and are nearly completely absent in Germany. The present study tries to reconstruct changes of seasonality from evidence of annual algal successions within the framework of well-established pollen zonation and 14C-AMS dates from terrestrial plants. Laminated Holocene sediments in Lake Jues (10°20.70' E, 51°39.30' N, 241 m a.s.l.), located at the SW margin of the Harz Mountains, central Germany, were studied for sediment characteristics, pollen, diatoms and coccal green algae. An age model is based on 21 calibrated AMS radiocarbon dates from terrestrial plants. The sedimentary record covers the entire Holocene period. Trophic status and circulation/stagnation patterns of the lake were inferred from algal assemblages, the subannual structure of varves and the physico-chemical properties of the sediment. During the Holocene, mixing conditions alternated between di-, oligo- and meromictic depending on length and variability of spring and fall periods, and the stability of winter and summer weather. The trophic state was controlled by nutrient input, circulation patterns and the temperature-dependent rates of organic production and mineralization. Climate shifts, mainly in phase with those recorded from other European regions, are inferred from changing limnological conditions and terrestrial vegetation. Significant changes occurred at 11,600 cal. yr. BP (Preboreal warming), between 10,600 and 10,100 cal. yr. BP (Boreal cooling), and between 8,400 and 4,550 cal. yr. BP (warm and dry interval of the Atlantic). Since 4,550 cal. yr. BP the climate became gradually cooler, wetter and more oceanic. This trend was interrupted by warmer and dryer phases between 3,440 and 2,850 cal. yr. BP and, likely, between 2,500 and 2,250 cal. yr. BP.