Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 76. (Budapest 1984)

Kordos-Szakály, M.: New data to the Miocene flora of Nógrádszakál (Hungary)

interpretation corresponds to the Carpathian Garáb Schlier Formation (HÁMOR 1978, 1979; HALMAI 1981) Marine deposits are covered by sandy layers, sandstone or in parallel formation by Lajta limestone layers of varied development referring to a regression and are rich in fossils (BOGSCH 1936a, 1942; FERENCZI 1942). They were identified as belonging to the Lower Tortonian. Because of the lithological uniformity and rich fauna of these formations HÁMOR (1978) separated them under the name of Nógrádszakái Marl Formation and placed them into Lower Badenian. The type-locality of the formation is the valley-cutting of the Bertece stream which is located the area of Nógrádszakái and also the section of the boring Nógrádszakái N° 2 between 87.7 and 195.0 meters. This boring was slink at the entrance of the Paris stream (HÁMOR 1978, HALMAI 1981). At the upper part of the formation charred plant remains already appear. In the boring Nógrádszakái N° 2 the Nógrádszakái Marl Formation between 38.3 and 87.7 meters is covered by calcareous layer rich in fossils, in some places also with charred plant remains. This is the Sámsonháza Formation (HÁMOR 1976, 1978, 1979) identified as Badenian. Also according to the sequence of boring N° 2 the Mátra Volkanite Formation, which gives the main bulk of andésite volcanism connected with the Nógrádszakái and Sámsonháza formation then covers them in a great thickness. In the valley of the Paris stream the andesitic formations of the Badenian Mátra Volcanite Formation are covered by Upper Badenian cross-laminated sand, gravel and marl with rhyolitic tuff regarded by HÁMOR (1978, 1979) as the abrasion coastal facies of Fertőrákos Lajta Limestone Formation. In spite of the profound geological knowledge of the area (STUR 1867; BOGSCH 1942; FERENCZI 1942; BARTKÓ 1952, 1961-62; HÁMOR 1976, 1978, 1979; HALMAI 1981) and the thorough analysis of the fossils of its certain layers (MAJZON 1936; BOGSCH 1936ab, 1942; NAGYMAROSSY 1980, borings Nógrádszakái N° 2, 3 and 4) the exact position of levels with plant impressions had not been identified unambiguously. According to the work of KOVÁCS (1959) in the main valley of the Paris stream the andésite tuff layer contains poorly preserved plant remains. In the side-valley of the Paris stream coarse-grained, there is a unsplittable andésite tuff which is rich in plants builds up the locality. Below it there is a whitish and pinkish fine-grained tuff layer with only a few but excellently preserved impressions. On the geological conditions of the locality of the Bertece valley the only fact that has been published is that the plant remains here were embedded in a tuffite similar to sandstone. On the basis of field surveys, observations on the spot the literature data we can establish beyond doubt that it is impossible for the plant remains to have originated from the Nógrádszakái Marl Formation. The rocks of Sámsonháza Formation are unknown as surface outcrops in the Paris stream and in the valley of the Bertece stream or they have not been identified as such hitherto. Localities yielding plant remains in the Bertece valley occur everywhere directly among andesitic formations or in close contact with them. Therefore it is most probable that these localities were formed simultaneously with the appearance of the main bulk of the Mátra Volcanite Formation. As regards the valley of the Paris stream it is difficult to form an opinion on the stratigraphical position of localities even nowadays. The rocks identified earlier as andésite tuff have a rather rhyolitic character. Their position is doubtful because it is possible that they are either blocks embedded into the abrasion gravel material of the Fertőrákos Lajta Limestone and sediments deposited simultaneously with them, or they are original layers of earlier position and formation. From the stratigraphical position it can be established that the localities of the Bertece valley formed as the results of the same process while those excavated in the Paris stream differ from them; they are by all means younger.