UTRECHT MICROPALEONTOLOGICAL BUllETINS

tional. Most Pliocene taxa, frequently considered to be newly introduced
from the Atlantic (Cita, 1973), are already present below this boundary in
similar proportions. This led us to doubt the assumed complete sterilization
of the Mediterranean at the end of the salinity crisis, i.e. at the end of the
Messinian (Cita, 1973, 1976). No indications of a catastrophic influx of
Atlantic waters, as proposed in the "desiccated, deep basin model" (Hsii,
Cita and Ryan, 1973), were observed either. The great depth of deposition
assumed for the first Pliocene sediments of these sections (cf. Cita, 197Sa)
could not be recognized from our data. The sediments directly underlying
the boundary were deposited at depths not exceeding wave-base, and the
gradational character of the boundary interval, in lithological as well as
faunal sense, revealed the gradual change to deeper environments which
ultimately, i.e. several meters above the boundary, might have resulted in
deposition in excess of 200 m. A gradual rise of sea-level and/or a moderate
rate of subsidence of the bottom, or both together seem to have been the
mechanisms which best explained our newly gathered data (Brolsma, 1975b).
These results were questioned during the Erice seminar (1975) of the
I.G.C.P.. Project 96. Re-arrangement of the earlier arguments and some new
data will be presented in the chapter on the Transitional interval.
More information concerning the history of the Pliocene Mediterranean
during a longer time-span would inevitably shed more light on the process
of return to normal marine 'conditions after the salinity crisis. With this in
mind, Lower to Upper Pliocene sediments at Capo Rossello and in a nearby
section called Punta Piccola were closely studied and sampled in detail. From
all samples, the benthonic and planktonic foraminiferal faunas were again
studied in a quantitative way. The results of this extended study will be
given in the following chapters.
In the meantime an 8 meter part of one of the sections at Capo Rossello
was selected for a pilot study on quantitative faunal methods within the
scope of I.G.C.P. Project 1, "Accuracy in time" (Utrecht Micropal. Bull.,
17). The results of this study, pertinent to our own investigation, are incorporated
in the present volume.
The sediments deposited during the latest part of the Messinian and early
middle parts of the Pliocene in southern Sicily can be divided into three
informal formations (see also Marchetti, 1957, 1960). In stratigraphic order
from bottom to top these are:
Arenazzolo - Grey to black coloured sediments directly overlying the