A study on the geology of the Ţaga region (Cluj district)

Abstract

2 ABSTRACT. The geological formations from Ţaga area (Cluj District) are Sarmatian in age (in outcrops) and Badenian (under surface). Lithologically, they are represented mainly by sands and sometimes fine sediments (clays, marls), interbedded with volcanic tuffs a low fossil content. The Badenian is the host of gas accumulations, concentrated in dome structures. Localization: the rural community of Ţaga is located East of Cluj District, at the border with Bistriţa - Nasaud District. Relief and hydrography: this region with large hilly areas belongs to the transition zone from the Transylvania (S) towards the Somesan Plateau (N). The highest hills are between 400 to 500 m (the Bocor Hill is over 500 m high). The cuesta relief that corresponds to the unconformable valley slopes is well represented. The main hydrographic collector is the Fizes Valley (from SE to NW) together with its numerous tributaries; within the frame of this valley and its affluents there are extensive marsh lands and lakes formed from a mixed origin (due to natural - earth slipping- and anthropogenous factors). This natural phenomenon originates in tectonic consequences, the rise of the confluence zone of the Fizes Valley, due to diapirism. The most well known lakes are those from Ţaga, Geaca, Catina, and Sântejude. Maxim (1935) examined the evolution of this region's valleys, while Sandulache (1970) covered a study of the lakes. A review of geological research studies: - Koch (1900) - in the Ţaga area the Plain Strata (Stratele de Câmpie) are developed (Middle Miocene). - Wein (1941 - 1942) - focus on the stratigraphy of the Buza-Nasal perimeter, as related to a nondenominated tuff level, and notes the lack of fossils (mentions a few Ervilia examples). - Mârza (1960, 1962) - identifies the Ghiris Tuff in the region and follows it through to Ocna Mures (Uioara), proves its continuity, identifies the geological formations as belonging to the Sarmatian, and discovers more fossil occurrences (Ervilia and Abra), including the fossil level located under the Ghiris Tuff. - Sabau (1984) 3 - his thesis on the Ţaga gas structure focus on the lithology of the formations and their paleonthologic content (micro and macro fauna). 1 Abstract of Geologia perimetrului comunei Ţaga- by I. Mârza (from Monografia comunei Ţaga; in press) 2