Michael R. Frogley

Ecological thresholds and patterns of millennial-scale climate variability: The response of vegetation in Greece during the last glacial period

The regional expression of millennial-scale climate variability during the last glacial is examined with particular reference to the vegetation response in Greece. Inspection of three pollen records from contrasting bioclimatic areas suggests that differences in the magnitude of cold events as recognized in the North Atlantic and western Mediterranean are expressed in terms of tree population changes only in areas with a range of favorable habitats. By contrast, records from sites where populations approach their tolerance threshold do not appear to resolve differences in the amplitude of the climate oscillations. Understanding the importance of local factors in modulating the biological response to climate change is critical when attempting to establish the spatial pattern of millennial variability.

Last interglacial conditions in southern Europe: evidence from Ioannina, northwest Greece

A new record combining isotopic and palynological results over the interval 133-111 ka BP at 100-200 year resolution from a long lacustrine sequence at Ioannina, northwest Greece is presented. The sequence provides an opportunity to examine the nature of climate variability during the Last Interglacial in southern Europe where information has hitherto been relatively limited. The record shows that the frequency and amplitude of changes during the transitional late glacial and late interglacial phases were markedly higher than that of the full interglacial interval. These differences are probably a reflection of the relative size of ice sheets in the circum-North Atlantic and associated ice-rafting events and climatic perturbations during these periods. During intervals of increased ice volume, it appears that North Atlantic variability has a significant downstream impact, dominating the climate signal in northwest Greece. During intervals of minimum ice volume there may be a decoupling between the North Atlantic system and continental climates with other factors, such as insolation changes, becoming more important. The length of the Last Interglacial at Ioannina defined by the presence of forest is here estimated to be c. 15 ka, in agreement with recent results from Portugal, but in conflict with estimates of c. 10 ka for the duration of the Eemian in northwest Europe. In the absence of independent confirmation for these estimates, however, these differences and associated implications remain unresolved.

A revised chronological and palaeoenvironmental framework for the Kastritsa rockshelter northwest Greece

Archaeological, palynological and palaeolimnological evidence is combined with new AMS radiocarbon dates to shed new light on a long-known, yet only partially understood, Upper Palaeolithic occupation in southeast Europe.

A Faunistic Review of the Modern and Fossil Molluscan Fauna from Lake Pamvotis, Ioannina, an Ancient Lake in Nw Greece: Implications for Endemism in the Balkans

The Balkans are justifiably famous for being natural hotspots of floral and faunal biodiversity and endemism. Much of this biological diversity is witnessed in the ancient lakes that exist (or previously existed) in the region, which have provided stable, long-lived arenas within which evolutionary processes have been able to operate. One group that ably demonstrate such diversity are the gastropod molluscs. Their wide dispersal, morphological variability and relative ease of identification make them ideal candidates for addressing questions concerning patterns and processes of biodiversity and evolution over time (e.g. Michel, 1996). Furthermore, the fact that they are often well preserved in fossil sequences means that they can provide a temporal dimension to evolutionary investigation, something that is often difficult to resolve when using groups more traditionally associated with this kind of work, such as the cichlid fishes. The molluscan faunas of the Balkans (and Greece in particular) have been the subject of study for at least the last two centuries (e.g. Butot & Welter-Schultes 1994). Isolated ancient lakes from the region, and in particular Ohrid, have often been a focus for detailed investigation, because of their remarkable endemic faunas (e.g. Hadzisce, 1956; Hubendick & Radoman, 1959; Stankovic, 1960; Meier-Brook, 1983; Stankovic, 1985; Schtt, 1987; Sattmann & Reischtz, 1988; Dhora & Welter-Schultes, 1996). Despite this, the malacology of many other key localities from the area still remains poorly documented. In this paper we first briefly review the main controls thought to influence the radiation of gastropods in ancient lakes and then present the modern and fossil aquatic molluscan fauna from a typical but previously poorly known site: Lake Pamvotis, located in the Ioannina Basin in NW Greece. Comparisons are then drawn with the gastropod fauna derived from other extant and fossil ancient lakes from across the Balkan region (bivalves are considered by Korniushin elsewhere in this volume), before highlighting some common patterns and providing some thoughts on the implications for speciation in ancient Balkan lake systems.

Modern and fossil ostracods from ancient lakes

Ancient lake systems contain incredibly rich archives of past biological and environmental change. Ostracods have long been associated with ancient lakes, largely because as a group they are common in such habitats, often occupy specific ecological niches and, generally, can be relatively easily studied. In addition, their excellent potential for preservation ensures that they frequently have a long fossil record, thereby providing a convenient means for investigating temporal changes in the lake system. Here we use a combination of biological and geological criteria to classify ancient lakes and, by means of a series of case studies using both extant and fossil exam-ples, go on to review some of the evolutionary and palaeoclimatic issues that can be addressed with respect to ancient lake ostracod faunas. We also high-light some of the current deficiencies in the field and make a call for more concerted research, not only from taxonomic and ecological standpoints, but also in the provision of rigorous chronological control for fossil sequences. The potential to couple both modern and fossil faunal data with new genetic analysis techniques will ensure that ostracod studies remain at the forefront of palaeoclimatic and evolutionary research in ancient lake environments.

Reconciling diverse lacustrine and terrestrial system response to penultimate deglacial warming in southern Europe

Unlike the most recent deglaciation, the regional expression of climate changes during the penultimate deglaciation remains understudied, even though it led into a period of excess warmth with estimates of global average temperature 1‒2 °C, and sea level ~6 m, above preindustrial values. We present the first complete high-resolution southern European diatom record capturing the penultimate glacial-interglacial transition, from Lake Ioannina (northwest Greece). It forms part of a suite of proxies selected to assess the character and phase relationships of terrestrial and aquatic ecosystem response to rapid climate warming, and to resolve apparent conflicts in proxy evidence for regional paleohydrology. The diatom data suggest a complex penultimate deglaciation driven primarily by multiple oscillations in lake level, and provide firm evidence for the regional influence of abrupt changes in North Atlantic conditions. There is diachroneity in lake and terrestrial ecosystem response to warming at the onset of the last interglacial, with an abrupt increase in lake level occurring ~2.7 k.y. prior to sustained forest expansion with peak precipitation. We identify the potentially important role of direct input of snow melt and glacial meltwater transfer to the subterranean karst system in response to warming, which would cause rising regional groundwater levels. This explanation, and the greater sensitivity of diatoms to subtle changes in temperature, reconciles the divergent lacustrine and terrestrial proxy evidence and highlights the sensitivity of lakes situated in mountainous karstic environments to past climate warming.

Hydrological and land-use changes in the Cuzco region (Cordillera Oriental, South East Peru) during the last 1200 years: a diatom-based reconstruction

A quantitative diatom analysis was carried out on a sediment core from the small infilled lake basin of Marcacocha (Cuzco-region, SE Peru), in order to reconstruct environmental changes between 800 and 1850 AD. Five stratigraphical zones were distinguished by means of constrained cluster analysis. Very few diatoms were present between 790 and 1070 AD, probably reflecting dry and cool conditions, at a time when anthropogenic impact was limited around the basin. The transition at ca. 1070 AD was the most pronounced, and corresponded with a marked shift towards higher temperatures, as deduced from plant macroremains and the pollen record. This coincided with a sudden climate shift from cold and dry conditions towards warmer and even drier conditions, as recorded elsewhere in tropical South America. Between 1070 and 1650 AD diatoms (mainly the genus Epithemia Ktzing) became more abundant, together with charophyte oospores, suggesting the existence of a stable, shallow lake. The transition in diatom composition and abundances at ca. 1650 AD, with peaks centered on 1700 AD, lag behind the start of the Little Ice Age (around 1490-1530 AD), though match increased cooling at the end of the 17th and early 18th century as recorded in Peruvian ice cores. This could be caused by a threshold that was passed after the lake level had lowered sufficiently due to a cooling and drying climate, as well as infilling processes. Further transitions in the diatom community may be interpreted less in terms of climatic change, but as increasing sensitivity to local environmental changes, such as a lake level decrease and lake infilling. A hiatus in diatom abundance observed between ca. 1750 and 1810 AD, could be associated with increasing colonization of Juncaceae around the lake margin and rapid infilling, possibly linked to the construction of drainage canals clearly visible today. The final stage of infilling occurred after ca. 1845 AD, with complete colonization of the remaining lake surface by Juncaceae, with further accumulation of peats.

On the origins of Cyprideis torosa (Jones, 1850) and a short biography of Professor T. R. Jones

The original description and taxonomic attribution of Cyprideis torosa (Jones, 1850) is reviewed with reference to the type locality at Grays, Essex, SE England and several of the original specimens are re-illustrated. A short biography of its author, the geologist T. R. Jones, is provided.

The Uplifted Terraces of the Arkitsa Region, NW Evoikos Gulf, Greece: A Result of Combined Tectonic and Volcanic Processes?

The Arkitsa-Kamena Vourla area of central Greece occupies a zone of accommodation between the two tectonic provinces of the North Aegean Trough (the extension of the North Anatolian fault system) and the Gulf of Corinth and is characterized by a series of very prominent tectonic landforms, notably the large (ca. 1000 m elevation) footwall ridge of the Arkitsa-Kamena Vourla fault system. Despite the highly prominent nature of this footwall ridge and the presence of very fresh tectonic landforms, this fault system is not known to have hosted any major historical earthquakes, and the tectonic and geomorphic evolution of the Arkitsa-Kamena Vourla area remains poorly constrained. This article utilizes a combined geomorphological, sedimentological, and macro-/microfossil approach to evaluate the Late Quaternary evolution of the Arkitsa area, in the eastern part of the fault system, focusing on prominent uplifted terraces present in the hanging wall of the Arkitsa fault. Three distinct raised glaciolacustrine terraces and previously reported uplifted marginal marine deposits suggest sustained uplift of the coastline at a rate of 1–1.5 mm/yr over the past at least 40,000 yr, possibly dating to 75,000 BP. While movement on an offshore normal fault strand may explain more recent coastal uplift, purely fault-driven, longer-term uplift at this rate requires anomalously high fault-slip and extension rates. Consequently, the development of the terraces and other geomorphic indicators of uplift may be at least partly due to nonfaulting processes, such as Quaternary (intrusive and/or extrusive) volcanic activity associated with evolution of the nearby Lichades volcanic center.