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stratifìed deposits on 1and are associateci with dized mud. In core LY II-3 the sequence is about
phreatomagmatic eruptions or vulcanian pu1se 20 m thick and is usually complete.
eruptions. The structures observed in the Strait Sapropels in the eastern and centrai Mediter-
may be ana1ogous. Each graded ash 1ayer probab1y ranean are believed to have accumulateci during
records a sing1e eruption. Base surge density flows stagnant phases associateci with stratifìcation of
(Moore, 1967) as well as ash flows may be of some water masses and formation of H 2 S-rich anaerobic
importance in the formation of the vo1canic de- bottom waters (Ohusson, 1961; Ryan, 1972; van
posits cored in the Strait. Straaten, 1972). The vertical sequence appears to
Another type of gravity flow deposit is illustrateci closely reflect large-scale oceanographic fluctua-
in Figure 32. Core KS 12 collected in a small basin tions. The organic ooze indicates that, initially,
in the Strait Narrows disp1ays thick 1ayers of sand conditions (including vertical mixing and oxygena-
and sandy mud interbedded with mud (Figure 35). tion of water masses) fostered a high degree of
These 1ayers consist of calcareous sand, in some in- benthic activity as attested by the importance of
stances clean and in some instances muddy, without bioturbation. Evidence that the water mass above
grading or sharp contact in some cases. Mech- the sea floor became progressively anaerobic and
anisms other than turbidity currents are postu- rich in H 2 S is provided by an increase of pyritized
1ated: in the case of clean sand, grain flow trans- burrows and eventual absence of any bottom or-
port is envisioned; debris flow or s1umping may ganic activity in the protosapropel and sapropel.
exp1ain the sandy mud and muddy sand mixtures The sapropel proper records a major anaerobic
(Hampton, 1972; Midd1eton and Hampton, 1973). phase (van Straaten, 1972). The varvelike sapro-
Further evidence of s1umping is recorded in basins, pel laminations, unlike those of the protosapropel,
such as a 70-cm thick contorted unit in core 139, are attributed to periodic high coccolith produc-
Verna 14~ at 1703 m in the Malta Trough (Figure tivity possibly resulting from seasonal upwelling
33). and subsequent sinking of the coccoliths (cf., Gulf
of California, v an An del, 1964; Black Se a, Degens
and Ross, 1974). A progression to more norma!
SAPROPEL SEQUENCE
open ocean conditions and vertical mixing is in-
The saprope1 sequence is found on1y in cores on dicated by the subsequent deposition of protosa-
the eastern margin of the Strait (i.e., on the s1ope prope1 and organic ooze. The upper orange oxi-
extending into the Ionian Basin) but not in the dized layer represents a return to oxygen-rich
Strait proper. The idea1ized complete saprope1 se- bottom water conditions. It is concluded that sapro-
quence (Figure 29) based on an analysis of core pel sequences observed east of the Strait are com-
LY II-3 (Figure 34) comprises a basai organic parab1e to those in the Herodotus Abyssal Plain
ooze layer (Figure 28) usually in continuity over and Nile Cone areas detailed by Maldonado and
gray hemipelagic mud. The organic ooze is inten- Stanley (1975).
sively bioturbated (presence of burrows, etc.) and
frequently includes a zone of pyritized worm tubes
Sedimentation and Stratigraphy in the Strait
(Figure 28, b) toward the top. Organic ooze grades
Environments
upward into a protosapropel sediment type distin-
guished by a low degree of bioturbation. The
REGIONAL DISTRIBUTION OF SEQUENCES
black, organic rich saprope1 Iayer proper is usually
well defìned, particularly in X-radiographs, where Our regional survey of sediment types and se-
it appears as a bundle of thin parallel laminae quences reveals the dose corre1ation between the
(Figure 28A) consisting of alternating calcareous Strait of Sicily depositional environments and the
coccolith-rich muds and somewhat thicker layers of resulting Quaternary sedimentary facies. This re-
calcareous-poor terrigenous mud. The sapropel is lation is illustrateci in Figures 33, 34, and 35. The
capped by a thin protosapropel 1ayer, which grades shallow platform environment is characterized by
upward into an organic ooze (Figure 28B). The coarsening- and fìning-upward sequences, which
sequence is covered by a 1ayer of 1ight brown to result from the associati o n of two ma jor sediment
dark yellowish orange (5 YR 5/6-10 YR 6/6) oxi- types: coarse calcareous sand and shallow water