Past environmental change and seawater intrusion into coastal Lake Lilaste,Latvia

Diatoms, organic matter and magnetic susceptibility in a 10-m-long sediment sequence from coastal Lake Lilaste, Latvia, were analysed to evaluate Holocene environmental changes related to past sea-water intrusions. Lake Lilaste is located ~1 km from the present sea coast in an area with a low uplift rate and a threshold altitude of 0.5 m a.s.l. It was thus considered to be an appropriate site to study the influence of past sea level fluctuations on the lake and its sediments. Variations in diatom community composition, along with sediment lithostratigraphy, show that a shallow, nutrient-rich freshwater lake existed there during the early Holocene. The first brackish-water diatoms appeared concurrent with a sea level rise ca. 8700 ± 50 cal a BP, but long-term, intermittent inputs of brackish water were observed between 6700 ± 40 and 4200 ± 80 cal a BP. During those time spans, diatoms indicate increased nutrient concentrations and high conductivity, a consequence of occasional mixing of brackish and freshwater that promoted biological productivity. Lilaste was isolated from the sea at 4200 ± 80 cal a BP, after which a stable freshwater environment, dominated by planktonic diatoms such as Aulacoseira ambigua, A. granulata, A. islandica and A. subarctica, was established. At 400 ± 50 cal a BP, planktonic diatoms were gradually replaced by Fragilaria spp., indicating the beginning of anthropogenic impact. The reconstructed relative water-level curve from the lake coincides with the eustatic sea level curve from 6800 ± 40 cal a BP onwards. There was a distinct increase in abundance of brackish-water diatoms when the sea level reached the threshold of Lilaste, which at that time was probably about 3 m lower than the present sea level. According to radiocarbon-dated shifts in the diatom community composition, the Litorina Sea transgression was a long-lasting event (ca. 2200 years) in the southern part of the Gulf of Riga, where the land uplift rate was near zero. It culminated more than 1000 years later than at other sites with higher uplift, in the northern part of the Baltic Sea.     

Spatio-temporal Organization of Mountain Taiga Geosystems of the Baikal Natural Territory

Results from investigating the geosystems of Cisbaikalia in its western and eastern parts (Primorskii Range and Barguzin Range, respectively) are presented. For studying three macroslopes of these mountain ranges (having an easterly aspect for the Primorskii Range and a westerly and south-easterly aspect for the Barguzin Range), the regional background and the main factors of the landscape differentiation of the study areas were analyzed. Structural features of topological geosystems are revealed, and large-scale maps of key areas are compiled (at a scale of 1:50 000). Maps of the landscape-typological structure were created on the basis of the structural-dynamic and facies analysis of landscapes. It is established that the main factors influencing the landscape diversity are the aspect and steepness of the slopes, the composition and structure of rocks, the absolute height, the amount of atmospheric precipitation, and anthropogenic impacts. It is determined that the influence of the lithomorphic factor is widespread throughout the study areas, the hydromorphic factor is also important, the cryomorphic factor occurs additionally in the goletz zone, and the xeromorphic factor is only observed on the Baikal Range and on the coastal plain in some areas of Priolkhonie. The dynamic aspect of the landscape structure and the relationships between geosystems are displayed in map legends.     

Practising geographical knowledge: fields, bodies and dissemination

In this article we make a case for a renewed emphasis upon some of the generic, albeit often tacit, spaces of practice that we share across our sub–disciplinary boundaries. In this we seek to emphasize the ways in which everyday actions make up the grander facades of institutional agendas, empirical projects and disciplinary schools of thought. To achieve this we trace the performance of disciplinary contours and identities across three important sites: the field, the body and the act of dissemination. There are, we will argue, significant commonalities that bind us as disciplinary practitioners in terms of how we perform within and across these sites, and indeed, how we join them up through our practices.