CONTENTS & ABSTRACTS
InEnglish. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Geology
Volume 54 No. 3September 2005
Height of the turbulent gas flow and transport distanceof glassy spherules on the example of the Kaali impact, Estonia; 145–152
Anto Raukas and Kustav-Olimar Laigna
Abstract. Impact ballistics of the Kaali impact group has beenconsidered by a number of authors givingextremely different interpretations. The exact time of the impact is alsodebatable, but according to direct dates the age of the craters is at least4000 years. Spherule studies in the mires of the islands of Saaremaa and Hiiumaa show that the impact tookplace some 7600 years ago. As the more or less vertical gas stream couldhave reached a height of 6.8–7.9 km, the small glassy particles, oftenhollow inside, were easily transported over long distances.
Key words: emitted gas flow, Kaali impact, crater age, spheruletransportation.
Lithologyand evolution of Devonian carbonate and carbonate-cemented rocks in Estonia; 153–180
Anne Kleesment and Alla Shogenova
Abstract. The Devonian sedimentary sequence of Estonia is mainlycomposed of terrigenous rocks, but includesalso carbonate and mixed carbonate-siliciclastic rocks. Theaccumulation of siliciclastic sediments has recurrently alternated withcarbonate sedimentation. Carbonate rocks are bestrepresented in the Narva Regional Stage where they arefully dolomitized. In addition to pure dolostones,dolomitic marlstones, and siliciclastic sediments, mixedcarbonate-siliciclastic rocks were recorded in six studied drill cores (Ruhnu (500), Taagepera, Tartu (453),Valga (10), Võru, and Värska (6)).Mixed rocks were deposited in transitional tidal flat conditions of shallowepicontinental sea during simultaneousaccumulation of carbonate and siliciclastic material. They include alsoterrigenous rocks cemented by dolomite during diagenesis. According tomineralogical, petrographical, andgeochemical data, early diagenetic dolostones and dolomitic marlstones weredeposited in the shallownearshore tidal flat environment in the seawater saturated with Mg, but changed in the next stages of diagenesis.Siliciclastic rocks were cemented during middle and late diagenesis byMg- and Mn-enriched fluids. Sometimes cementof siliciclastic and mixed rocks is represented by gypsum and latediagenetic calcite. The porosity of Devonian rocks increases with increasingclay content, and decreases with mechanicalcompaction, dolomitization, and carbonate cementation.The sedimentation and diagenetic history are reflected in gamma-raylogs.
Key words: Devonian, carbonate rocks, siliciclasticrocks, mixed rocks, chemical composition, diagenesis, X-ray diffractometry,porosity, gamma-ray logs.
ThelodontOeselia mosaica gen. et sp. nov. from the Wenlock and Ludlow of the East Baltic; 181–190
Tiiu Märss
Abstract. A thelodont Oeselia mosaica gen.et sp. nov. is described from the Upper Wenlock and Lower Ludlow (Silurian) of Estonia and Latvia. The species has verysmall to small scales and shows low variation in scale morphology,simple branching dentine tubules, and a specific ultrasculpture with polygonsof irregular shape, separated by narrow grooves.
Key words: Thelodonti, Agnatha, Silurian, East Baltic.
Recentinvestigations of the peculiarities of Vilnius relief dynamics; 191–203
Regina Morkûnaitë and Algimantas Èesnulevièius
Abstract. The paper presents data about landslides which occurred in2000, 2001, and 2002 usually after autumn orspring rainfalls (for example in June 2001 after the rainfall of 19.8 mmand in August after the rainfalls of 29.8 and 37.9 mm). In terms ofthe surrounding relief genesis, sediments, and character of morphometry, landslides occurred in erosional relief(60%) and in sandy loam sediments (80%). Landslides were the mostfrequent in small high hills (height over 20 m, slope length morethan 100 m, slope angle over 7°).Changes along seven levelling profiles, located in the erosional, ice-marginalformations, and glaciofluvial relief types, are considered. Erosionaltransformations mostly took place in the upper and lower parts of the slopes,where up to 0.35 m of sediments were eroded or accumulated in two years.According to the relief stability coefficient (4.6), the Rasos–Ribiðkës areawas erosionally the most active.
Key words: landslide, slope stability, suffosion.
Instructionsto authors; 204–206
