Late Miocene fluvial distributary system in the northern Danube Basin (Pannonian Basin System): depositional processes, stratigraphic architecture and controlling factors of the Piešťany Member (Volkovce Formation)

Abstract

M., Kováè, M., Hók, J., Šujan, M., Braucher, R., Rybár, S., de Leeuw, A., 2017. Late Mio cene flu vial distributary system in the north ern Dan ube Ba sin (Pannonian Ba sin Sys tem): depositional pro cesses, strati graphic ar chi tec ture and con trolling fac tors of the Piešïany Mem ber (Volkovce For ma tion). Geo log i cal Quar terly, 61 (3): 521-548, doi: 10.7306/gq.1360Aim of the study was to in ves ti gate the de tailed strati graphic ar chi tec ture of the al lu vial Volkovce For ma tion, which was de pos ited in the north ern Dan ube Ba sin dur ing the in ter val be tween 10 and 6 Ma. Two type lo cal ity ex po sures were sub ject to fa cies anal y sis and in ter pre ta tion of depositional pro cesses and >500 bore holes served for cor re la tion of spa tial vari abil ity in the char ac ter of the for ma tion. The study was fo cused on the north ern Blatné and west ern Rišòovce de pres sions, which are partly sep a rated by the Považský Inovec Moun tains horst. It was re vealed, that a mostly grav elly flu vial distributary system of the Piešïany Mem ber was de pos ited in the north ern Blatné de pres sion, partly con fined by the ex posed horst and by in cised palaeotopography. The se quence is com posed of amal gam ated braided river chan nel bod ies with no overbank strata, in re sponse to high sed i ment sup ply and low ac com mo da tion. The palaeo-stream then crossed the horst in its southern part to wards the Rišòovce de pres sion, where there was four times more ac com mo da tion. The sub merged horst acted as a bound ary, where the depositional pro cesses changed to a me an der ing river and sig nif i cant overbank de pos its started to be pre served. Only small streams were pres ent in the north ern Rišòovce de pres sion, which led to very low sed i ment sup ply com pared to the high ac com mo da tion there. The depositional sys tem was af fected mainly by the in cised palaeotopography, by the lo ca tion of sed i ment in put to gether with spa tial dif fer ences in ac com mo da tion rate caused by the ac tiv ity of the Ripòany Fault on the south east ern side of the Považský Inovec Mts.

Acta Geologica Polonica

“…3A-C). Facies characterised by trough and planar cross-stratification (St, SGt, STCt, and Sp) are typical of channel bedforms such as 3-D and 2-D dunes, respectively (Allen 1965;Bridge 1993Bridge , 2003Šujan et al 2017). Some of them may also represent the mid-channel bars (longitudinal, transverse, composite), especially when lamination is slightly convex upwards (Allen 1983;Bristow and Best 1993).…”