MILIOLIDAE - Acta Palaeontologica Polonica

20 EWA LUCZKOWSKA
equally abundant Varidentella reussi, Cycloforina predcarpatica, Articulina
problema and Articularia articulinoides. As can be seen, the species are
few in number although the number of specimens is large.
The above-mentioned species abound in the northern coastal zone,
e.g. in the region of Tarnobrzeg (Luczkowska, 1964), whereas in the deeper
zone of the Foredeep, where the Sarmatian deposits exceed 1000 m in
thickness, they are met with more rarely. The microfauna found in the
Sarmatian layers of the Foredeep is mostly a redeposited fauna washed
out of the deposits of the Upper or Lower Tortonian and even those of
the Cretaceous.
Zone with Elphidium hauerinum. - This zone, overlying the zone with
Varidentella sarmatica has hardly any miliolids. From among the
Sarmatian species, only dwarfish Varidentella reussi is encountered in it;
however, it may well be that the rare specimens of this species come
from the lower layers that have been washed away. The range of this
zone is not known exactly, supposedly it occurs only locally in the region
of Tarnobrzeg.
PALAEOECOLOGY
The Miliolidae are a foraminiferal group having small requirements in
respect of water salinity, for they may be found in both salt and brackish
waters, but their occurrence is frequently restricted to only certain depths
and temperatures. In the contemporary seas they prevail over inner shelf
and in open gulfs, in warm and shallow tropical and subtropical waters,
at depths from zero to about 100 m (Norton, 1930; Lowman, 1949; Sigal,
1952; Matthes, 1956; Bandy & Arnal, 1960; Loeblich & Tappan, 1964;
Bandy, 1964 b; Boltovskoy, 1965), where they may form 50 per cent or
more of the whole population. They belong chiefly to different species
of Quinqueloculina and Triloculina 3), which are good indicators of conditions
in the vinicity of coasts. These genera are not dominant in the
region of central and outer shelves, but here Biloculinella appears beside
them. In the bathyal zone the miliolids are scarce except Pyrgo and
Pyrgoella, which here develop various groups of species and grow to
a large size (above 5 mm), whereas the shelf forms of Pyrgo do not
usually exceed 1 mm.
Such a pattern of distribution of the Miliolidae is generally noted in
tropical regions and those of warm water all over the world. In the Gulf
of Mexico the Miliolidae are abundant at depths of 30 m (Shifflett, 1961),
70-100 m (the genus Quinqueloculina chiefly in the inner turbulent zone
at 20-30 m; Phleger, 1960), or even down to 150 m (Parker, 1954), and
do not descend below 180-220 m (Phleger & Parker, 1951). In Florida the
3) The generic names are given after the authors cited.