Comparison of palynofacies distribution in north-eastern and north-western margins of Tethyan Ocean during Middle Jurassic

We studied palynofacies, i.e., organic particles larger than 15 μm left after chemical dissolution of mineral sedimentary rock components, from Jurassic successions of Algeria and Poland representing then marginal zones of opening Tethyan Ocean (Fig. 1). Material from north-western Algeria represents two structural units located once along the north-eastern margin of the Tethyan Ocean: the proximal Tlemcenian Domain compared to the more offshore Tellian Domain. Material from southern Poland and northern Slovakia represents a series of tectonic units originally deposited at the north-eastern margin that nowadays form the Pieniny Klippen Belt: the Czorsztyn Unit being closest to the emerged area, the most offshore Branisko-Pieniny units, and the Czertezik-Niedzica units placed in between.
Analysis of palynofacies of the above mentioned material showed significant differences in the palynofacies composition among particular units, but showing a similar trend in both regions. The Middle Jurassic strata of the marginal Tlemcenian Domain yielded diversified palynofacies composed of dinoflagellate cysts and terrestrial elements like sporomorphs and cuticles (Fig. 2). Towards the more offshore Tellian Domain these palynomorphs and phytoclasts are replaced by black and dark brown phytoclasts.
The same trend has been recorded from the Pieniny Klippen Belt units: the most proximal one, the Czorsztyn Unit, is characterized by palynofacies with high proportion of dinoflagellate cysts. Toward the basin that extended south of the Czorsztyn Ridge, black opaque phytoclasts proportion increases and reaches 100% in basinal facies of the Pieniny and Branisko units (Fig. 2).
The above described trend of palynofacies transitions reflects changes in palaeoenvironment related to increasing distance from the shore, decreasing land influences basinwards, and, as a consequence, with increasing aerobic conditions in the bottom water zone.