Page 2 - Maldonado_Stanley_1976

ABSTRACT

Maldonado, Andrés, and Daniel Jean Stanley. Late Quaternary Sedimentation
and Stratigraphy in the Strait of Sicily. Smithsonian Contributions to the Earth
Sciences} number 16, 73 pages, 39 fìgures, 5 tables, 1976.-The Strait of Sicily,
a broad, elongate, topographically complex platform in the centrai Mediter-
ranean, separates the deep Ionian Basin from the Algéro-Balearic and Tyrrhenian
basins to the west. A detailed core analysis shows that the late Quaternary sec-
tions in the different sectors of the Strait are distinct from those in the deep
Mediterranean basins. Strait lithofacies are characteristically uniform, highly
bioturbated, and contain signifìcant amounts of coarse calcareous sediment. Five
major sediment types (coarse calcareous sand, sand- to silt-size sediment, ash,
mud, and sapropel) are grouped into natural vertical successions termed
sequences. The three major sequences defìned in the Strait are upward-coarsening
and upward-fìning, uniform, and turbiditic (including both mud and sand-silt
turbidites); sapropel sequences are recovered in cores on the Ionian slope east
of the Strait.
The direct relation between sediment type, latera! lithofacies distribution,
water depth, and structural displacement is demonstrated. For example, the
proportion of turbiditic mud increases while that of hemipelagic mud and bio-
turbated strata decreases with depth. The effects of regional Quaternary events,
particularly climatic changes and eustatic sea level oscillations, are well recorded
in cores collected in shallow platform and neritic-bathyal environments; here
the upper sediment sequences are truncated and fìning- and coarsening-upward
sequences, which include coarse calcareous sand layers interbedded with mud and
sandy lutite, prevail. In contrast, well stratifìed units comprising sand (including
gravity flow units and volcanic ash) alternating with hemipelagic and turbiditic
mud form the surfìcial deposits in the deep (>1000 m) elongate Linosa, Pantel-
leria, and Malta basins. Homogeneous bioturbated light olive gray to dusty
yellow muddy sequences predominate in the intermediate depth neritic-bathyal
environments.
Stratigraphic correlation of cores based on carbon-14 analyses shows that indi-
viduai units or sequences are not correlatable across the Strait or even within
small basins, although it is possible to recognize a generai vertical succession of
depositional patterns. Sedimentation rates generally decrease with increasing
depth. Rates in the deep basins have been relatively uniform from the late
Quaternary to the present, while upper (Holocene) sequences in the shallow
platform and neritic-bathyal environments bave been truncated. Correlation of
reflectors on high-resolution subbottom profìles indicates that faulting in many
sectors of the Strait is of recent or subrecent origin and that the vertical displace-
ment rate is locally in excess of the average sedimentation rate (i.e., greater than
20 cm per l 000 years).
The absence of sapropel layers in the Strait basins indicates that these depres-
sions remained ventilated during periods when anaerobic conditions prevailed
in the deep basins in the eastern and centrai Mediterranean. An early Holocene
paleooceanographic model depicting a possible reversal of currents in the Strait
of Sicily region is postulated.

0FFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded
in the Institution's annua} report, Smithsonian Year. SI PRESS NUMBER 6166. SERIES COVER DESIGN:
Aerial view of Ulawun Volcano, New Britain.

Library of Congress Cataloging in Publication Data
Maldonado, Andrés.
Late Quaternary sedimentation and stratigraphy in the Strait of Sicily.
(Smithsonian contributions to the earth sciences ; no. 16)
Bibliography: p.
Supt. of Docs. no.: SI 1.26:16
l. Geology, Stratigraphic-Quaternary. 2. Sediments (Geology)-Sicily, Strait of. 3. Geology-
Sicily, Strait of. I. Stanley, Daniel J., joint author. II. Title. III. Series: Smithsonian
Institution. Smithsonian contributions to the earth sciences ; no. 16.
QEI.S227 no. 16 [QE696] 550'.8s [551.4'62'1] 75-619369