MILIOLIDAE - Acta Palaeontologica Polonica

MILIOLIDAE FROM MIOCENE OF POLAND 23
In his study of the relation of the present Foraminifera to the deposit
facies in the turbulent zone of Cardigan Bay (Wales), Atkinson (1971)
gives interesting observations concerning the foraminiferal population as
a whole, and so including the Miliolidae. He states that living foraminifera
occur frequently in coarse grained deposits, whereas empty tests accumulate
in large numbers in fine-grained deposits. The empty foraminiferal
tests are washed away from the coarse-grained deposits to the
fine-grained ones and only few large specimens remain in the former
(e.g. Massilina secans is a good palaeoecological indicator of sublittoral
conditions and coarse-grained substratum). Porcellaneous tests, as he~vier
and larger, are not generally so readily displaced by water movements.
The same is true of the agglutinating foraminifers.
So far as the reconstruction of the palaeoecological conditions in the
Miocene sea of southern Poland is concerned, a comparison with the
occurrence of the Miliolidae in the present seas provides some information.
Although most species of the Miocene miliolids differ from the contemporary
ones (morphologically some of them come very near to the
contemporary forms, e.g. Quinqueloculina akneriana to Q. seminulum
(Linnaeus), Q. buchiana to Q. lamarckiana d'Orbigny, Q. regularis to
Q. pentagona Giunta, Triloculina neudorfensis to T. tricarinata d'Orbigny
and a number of other species), still they belong to the same genera and
form similar groups. The analogies suggested are presented below by the
example of the typical associations given in Table 1.
Karsy, Korytnica, Benczyn and Wieliczka have miliolid assemblages
typical of the Lower Tortonian. The Lower Tortonian sea covered the
area of the Precarpathian Foredeep (Text-fig. 1) and probably extended
to the west as far as the eastern part of the Sudety Foreland, being
connected with the Vienna Basin by a narrow strait of the Moravian Gate
in the south. In the east the foreland of the East Carpathians in the
USSR connects it with the Ukraine and Moldavia. In respect of area the
sea was a third of the Adriatic Sea; it had its northern and southern
coastlines irregular and indented and a well-developed shelf zone, in
which lithothamnian reefs were formed in places. Virtually, it was not
an open sea and it is risky to compare the conditions prevailing in it with
those of open bays of the present oceans. Nevertheless, it is possible to
draw parallels regarding the littoral zones.
Karsy and Korytnica are typical localities of the occurrence of the
Lower Tortonian microfauna in the northern coastal zone. Their miliolid
assemblages differ somewhat from each other, but they undoubtedly
characterize similar environments, since they contain the same groups of
genera and for the most part the same species. Quinqueloculina QS and
MS and Triloculina predominate evidently, Pyrgo, Pyrgoella and Miliolinella
occur in smaller numbers and even then are represented by small
specimens. Among the quinqueloculines Q. buchiana, morphologically