MILIOLIDAE - Acta Palaeontologica Polonica

14 EWA LUCZKOWSKA
In the present work the old term "Tortonian" is retained to simplify the
references to the author's previous papers and thus to avoid obscurity. It
seems expedient to explain that this term is here used as the Tortonian
sensu lato, i.e. a geochronological unit based on the occurrence of
planktonic and benthonic foraminifera, its lower boundary being marked
out by the appearance of Praeorbulina in the Tortonian and the upper
one by the appearance of Anomalinoides dividens in the Sarmatian. Compared
with the situation in the Vienna Basin, this period corresponds to
the geochronological unit "Badenian" proposed in 1968, the lower boundary
of which is the bottom of the "Lagenidae Zone" and the upper one the
top of the "Bulimina-Rotalia Zone".
The miliolid assemblages from the Miocene of Poland vary between
particular stratigraphic zones. It may be stated in general that the groups
of miliolid species living in the Tortonian differ in composition from those
in the Sarmatian. Although in the Tortonian the assemblages vary from
zone to zone, still they have some common features, e.g. the predominance
of species belonging to the genera Quinqueloculina, Cycloforina, Lachlanella,
Sigmoilopsis, Siphonaperta, Miliolinella, Pyrgo, Sinuloculina,
Triloculina and other species having large-sized tests, sometimes reaching
to 2-3 mm. The species living in the Sarmatian have small tests, the
dimensions of which do not exceed 0.5-1 mm (except for the forms with
the uniserial arrangement of chambers), and belong chiefly to the genera
Varidentella, Articulina, Articularia and the species of Cycloforina other
than those occurring in the Tortonian. Only a few Tortonian species
persisted into the Sarmatian.
A list of the Miliolidae occuring in typical localities representing
deposits varying in age is given by way of example in Table 1: for the
Lower Tortonian - Karsy and Korytnica in the northern coastal region,
Benczyn in the southern coastal region and Wieliczka in the region of the
Foredeep; for the Upper Tortonian - Gliwice Stare in the north-western
coastal region in Upper Silesia, W~glinek near Zaklik6w in the Roztocze
Mts and Niskowa near Nowy SqCZ in the southern coastal region.
The Miliolidae from Dwikozy near Sandomierz are given for the Sarmatian,
separately for the sandy deposits belonging to the lower microfaunal zone
and for the argillaceous deposits of the upper one.
The stratigraphic distribution of the species under study given in
Table I is based on the above-mentioned examples and on the species
identified from a number of other outcrops and bore holes, the list of'
which is given in the section entitled Material. The localities at which
individual species occur are mentioned in their descriptions in the
palaeontological part.
The characteristic assemblages of the Miliolidae of the Tortonian and
Sarmatian strata are discussed below.