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68 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

type, composed of bioclastic as well as volcanic tions between sedimentation and depth may be ap-
materia!, shows the vertical sequence of sedimen- plicable in the interpretation of ancient deposits.
tary structures characteristic of typical terrigenous 12. Sedimentation rates in the Strait (with
turbidites. some exceptions) generally decrease with increas-
9. Stratigraphic correlation of the cores is based ing depth and have been relatively uniform during
on 41 carbon-14 analyses. The study shows that the late Quaternary. However, there is a significant
lipecific sediment units or sequences generally are difference in the age of sediment sequences at the
not corre1atab1e across the Strait or even within a top of cores in the different environments: on shai-
single environment such as a small deep basin. It low banks, the top of some cores are truncated in
is possible, however, to recognize a generai succes- the late P1eistocene to eariy Hoiocene; in the
sion of sedimentation patterns in each major neritic-bathyal environments in the early Rolo-
environment. cene; and in the deep basins, sediments have ac-
10. Depositional patterns in the Strait have been cumulated on a fairly continuous basis from the
controlled mainly by three major factors: regional late Pleistocene unti! the recent.
Quaternary events reiated to changes of climate and 13. Faulting in many sectors of the Strait is of
eustatic sea Ievei oscillations, depth, and organisms. recent or subrecent origin, and correlation of re-
The Quaternary climatic and associated sea Ievei flectors on high-resolution subbottom profiles indi-
oscillations are reflected primarily by the trunca- cates that this vertical displacement is commonly
tion of the upper sediment sequences on the shal- in excess of the sedimentation rate, i.e., in excess of
low platform and in neritic-bathyal environments, 20 cm per l 000 years.
and development of fining- and coarsening-upward 14. No saprope1 layers are noted in basin cores,
sequences on the shallow platform. The distribu- although the three deep Strait of Sicily basin
tion of hemipelagic and turbiditic mud lithofacies plains lie at a depth (1300 to 1700 m) well below
in the neritic-bathyal environments is related to that at which sapropel deposits are found else-
the present sea levei stand. In contrast, the well- where in the centrai and western Mediterranean.
stratified sections-in the deep enclosed basins show It appears that these deep basins remained venti-
a uniform rate of sedimentation from the late Qua- lated during the periods when anaerobic condi-
ternary t o the presen t, an d core t o core differences tions prevailed in the Ionian-Levantine basins east
have resuited from variations in the number of of the Strait. Apparently the Strait did not com-
turbiditic and volcanic ash incursions into the pletely block the circulation of water masses be-
deep basins. tween the eastern and western Mediterranean ba-
Il. The dose relation between sediment type sins in the late Quaternary.
and depth is well demonstrated by the inverse re- 15. An early Holocene paleooceanographic
lation of turbiditic mud, which increases, and model in which a possible reversal of currents is
hemipelagic mud, which decreases with increasing postulated would help explain the particular dis-
depth. About three-quarters of the variance in the tribution of sedimentary sequences and different
degree of bioturbation in the Strait cores also can rates of sedimentation observed in the various
be explained as a function of depth. These rela- Strait of Sicily environments.