Regime of karst and glacial lakes at the carboniferous plateau of Tikhvin Ridge in the Northwest of the Russian platform

The studied territory is restricted to the central part of Tikhvin Ridge composed of karstified terrigenous and carbonate deposits of Carboniferous age. The central part of the area is a flat watershed dividing the rivers flowing northwest to Lake Ladoga and those flowing southeast to the Rybinsk water reservoir. The considered territory lies within the Msta River basin subjected to the recent tectonic uplift, forming landforms of Alpine type. Considerable longitudinal sloping of rivers provide intense surface and subsurface runoff (the active hydrodynamic regime). In the considered territory, the lakes are known with their areas changing significantly and quickly enough (months or years). The water in lake basins may disappear or fill them back completely. According to observations, these abrupt decreases and rises in water level do not correlate with seasonal floods, high water and low water periods. The phenomenon of drying and (what is particularly interesting) subsequent filling of lake basins with water is obviously related to the karstic groundwater regime, which is of scientific interest. The up-to-date research data include state geological maps (scale 1:200 000); topographic maps (scale 1:100 000); space images of the free-access Google Planet Earth Internet service, taken in summer and autumn 1984-2016; and weather service data. Cartographic materials were processed in GIS. The analysis of collected data allowed us to distinguish between two types of lakes, i.e., those with insignificant and substantial changes in area with time. Water reservoirs of the first type located on water-permeable moraine Quaternary deposits are classified as glacial. Other lakes overlying immediately Carboniferous deposits, have funnels in the basin bottom and are considered as karstic. The areas of two glacial and three karstic lakes have been measured (by interpreting satellite images) within the central part of the Carboniferous plateau at the Tikhvin Ridge. Variation in the glacial lake areas in the span of 33 years were found to be not crucial, being directly related to annual atmospheric precipitation not correlating with the changing areas of karstic lakes. Karstic lakes reveal 2-, 3- and 12-year-long cycles of significant changes in areas. These changes show decreases and rises in their levels and volumes. They are correlated among all karstic lakes irrespective of the average annual volume of atmospheric precipitation. It points to the significant participation of groundwater in alimentation of karstic lakes belonging to a single karstic water-bearing complex of underlying Carboniferous deposits. Authors relate the recurrent shallowing and filling of karstic lakes to the modern alternating tectonic movements leading to variation in permeability of karstic groundwater-bearing deposits.

Karst and geotops of karst origin in Albania

Albania is one of the most karst-developed countries in Europe. Karst phenomena are related to soluted carbonate formations which cover of about 7300 km2 of Albanian territory and with sulfate evaporates rocks, which outcrop of about 500 km2. Typically alpine relief of average altitude 708 m above the sea level and high horizontal splitting are favorable for karst development. Karst and geological sites of karst origin are widespread mainly in Albanian Alps and in Ionian zone. In Albanides there are determined surfaces and underground karst forms which belong to the Neo-Pliocene-Quaternary age and deep karst forms belonging to the paleokarst in old formations. The most widespread karst forms in carbonate rocks there are valleys, caves, cones etc., while into salt rocks there are formed many karstic lakes and depressions. Up to now there are determined about 80 karstic caves, nice karst fields, valleys, plains, which represent geological sites of karst origin.

Living with the Lake, Living Without the Lake An Introduction into the Research of the Way of Life by the Intermittent Karstic Lakes Petelinjsko Jezero and Palško Jezero

Petelinjci in Palčani so se skozi stoletja prilagajali spremenljivi naravi presihajočih jezer. Obe jezeri sta poplavljeni le del leta, tako da travnate površine v poletnem času praviloma omogočajo vsakoletni pridelek sena. Palško jezero in obrežje Petelinjskega jezera sta primerna za pašo. V gospodarskem pogledu sta jezeri bili in sta še vedno vezani na vzrejo živine. Kmetovanje na tem področju v današnjem času ne prinaša dobička, zato se bo v prihodnosti krajina ohranila taka kot je le, če bo država namenila kmetijski dejavnosti dovolj denarne pomoči. Na jezero je bila do srede dvajsetega stoletja vezana še ena gospodarska dejavnost, in sicer ledarstvo. Dodatni dopolnilni dejavnosti, ki sta pogojeni z jezerom, sta lov in nabiralništvo. Petelinjci in Palčani so bili v preteklosti prisiljeni svoji jezeri deliti z avstroogrsko, italijansko in jugoslovansko vojsko, ki so za seboj pustile še danes vidne sledi. Jezeri s svojo nenavadno in nadvse slikovito naravo domačinom predstavljata kraj miru in sprostitve. People of Petelinje and Palčje have adapted to the ever-changing nature of the intermittent karstic lakes through the centuries. Both lakes are filled with water only a part of the year, so that the grassy areas usually provide a yearly harvest of hay. Palško jezero and the shores of Petelinjsko jezero are suitable for pasturing. Economically the lakes were and still are connected with raising livestock. Agriculture is now no longer profitable, so the only way to preserve the land is by the state devoting enough money for agriculture. The lake was connected to another economic activity until the middle of the 20th century, ice making. Additional supplementary activities dependent on the lake are hunting and gathering. Petelinje and Palčje villagers had to share their lakes with the Austro-Hungarian, Italian and Yugoslav armies in the past; they left traces that can still be seen today. The lakes, with their unusual and highly picturesque nature, represent a place of peace and relaxation to the locals.

Investigation of freshwater sponges spicules deposits in a karstic lake in Brazil

The environmental conditions which contributed to the formation of the notorious quaternary deposits of freshwater sponge spicules in karstic lentic environments in Brazil have been subject of some speculation. No investigation has yet been conducted to test whether these deposits currently originate in karstic lakes. To provide for such an investigation, Serra Negra Lake, which is formed on an ultramafic-alkaline-carbonatite dome at central western Brazil, close to the area of occurrence of the paleo-deposits was selected for the study. Bottom sediments were sampled at 10 stations across the lake, and water was sampled at five of the stations, in June/2011 (rainy season) and October/2011 (dry season). Analysis of granulometry, organic matter and presence of spicules were carried out in the sediments. Lake water was analysed for the main physical and chemical characteristics. Deposit of spicules was restricted to the northern area of the lake, which is rich in macrophyte. The taxonomic analysis of the spicules indicated the contribution of five sponge species, Dosilia pydanieli, Metania spinata, Radiospongilla amazonensis, Trochospongilla variabilis and Heterorotula fistula, which formed large deposits in neighbouring areas. The high silica concentration, derived from the dome volcanic rocks, constant water level and available substrate are credited for the continuous production of sponges and spicules, confirmed by the rare presence of gemmoscleres. The lake is classed as a minerotrophic fen type of bog with a heavy contribution from the surrounding creeks. Lake sediments are fine with high levels of organic matter and peat, which contributed to the trapping of spicules in the sediments.