Holocene sedimentation in the Strait of Otranto, Mediterranean Sea

An extensive radiograph study of 24 undisturbed, up to 206-cm long box and gravity cores from the western part of the Strait of Otranto revealed a great variety of primary bedding structures and secondary burrowing features.
The regional distribution of the sediments according to their structural, textural, and compositional properties reflects the major morphologic subdivisions of the strait into shelf, slope, and trough bottom (e.g., the bottom of the northern end of the Corfu-Kephallinia Trough, which extends from the northeastern Ionian Sea into the Strait of Otranto):
(1) The Apulian shelf (0 to -170m) is only partly covered by very poorly sorted, muddy sands without layering. These relict(?) sands are rich in organic carbonate debris and contain glauconite and reworked (?Pleistocene) ooids.
(2) The slope sediments (-170 to -1,000 m) are poorly sorted, sandy muds with a high degree of burrowing. One core (OT 5) is laminated and shows slump structures. An origin of these slumped sediment masses from older deposits higher on the slope was inferred from their abnormal compaction, color, texture, organic content, and mineral composition.
(3) Cores from the northern end of the Corfu-Kephallinia Trough (-980 to -1,060 m) display a few graded sand layers, 2-5 cm (maximum 30 cm) thick with parallel and ripple-cross-laminations, deposited by oceanic bottom or small-scale turbidity currents. They are intercalated with homogeneous lutite.
(4) Hemipelagic sediments prevail in the more southerly part of the Corfu-Kephallinia Trough and on the "Apulian-Ionian Ridge", the southern submarine extension of the Apulian Peninsula. Below a core depth of 160 cm, these cores have a laminated ("varved") zone, representing an Early Holocene (Boreal-Atlanticum) "stagnation layer" (14C age approximately 9,000 years).
The terrigenous components of the surface sediments as well as those of the deeper sand layers can be derived from the Apulian shelf and the Italian mainland (Cretaceous Apulian Plateau and Gargano Mountains, southern Apennines, volcanic province of the Monte Vulture). Indicated by the heavy mineral glaucophane, a minor proportion of the sedimentary material is probably of Alpine origin. If this portion is considered to be first-cycle clastic material it reaches the Strait of Otranto after a longitudinal transport of 700 km via the Adriatic Sea. The lack of phyllosilicates in the coarse- to medium-grained shelf samples might be explained by the activity of the "Apulian Current" (surface velocities up to 4 knots) which in the past possibly has affected the bottom almost down to depths of the shelf edge.
The percentage of planktonic organisms, and also the plankton: benthos ratio in the sediments is a useful indicator for bathymetry (depth zonation).

对奥特朗托海峡（Strait of Otranto）西部海域24根未受扰动、最长达206 cm的箱式岩芯与重力岩芯（box and gravity cores）开展的大规模放射成像研究（radiograph study），揭示了丰富多样的原生层理构造（primary bedding structures）与次生潜穴特征（secondary burrowing features）。
根据沉积物的结构、组构与成分属性划分的区域分布格局，反映了该海峡划分为陆架（shelf）、陆坡（slope）与海槽底（trough bottom）的主要地貌分区（morphologic subdivisions），例如从爱奥尼亚海（Ionian Sea）东北部延伸至奥特朗托海峡的科孚-凯法利尼亚海槽（Corfu-Kephallinia Trough）北端海床：
(1) 普利亚陆架（Apulian shelf）（0至-170 m）仅局部被分选极差的无层理泥质砂覆盖。这些残留（？）砂体富含有机碳酸盐碎屑（organic carbonate debris），含有海绿石（glauconite）与再改造（？更新世（Pleistocene））鲕粒（ooids）。
(2) 陆坡沉积物（-170至-1000 m）为分选较差的砂质泥，潜穴发育程度高。其中一根岩芯（OT 5）具有纹层构造，并显示滑塌构造（slump structures）。根据其异常的压实程度、颜色、组构、有机质含量与矿物组成，推断这些滑塌沉积物团块来源于陆坡上部的古老沉积层。
(3) 科孚-凯法利尼亚海槽北端（-980至-1060 m）的岩芯可见数层粒序砂层（graded sand layers），厚度2至5 cm（最大30 cm），发育平行层理与波纹交错层理（ripple-cross-laminations），由大洋底流或小规模浊流（turbidity currents）沉积形成，与均质泥岩（lutite）互层产出。
(4) 半远洋沉积物（Hemipelagic sediments）广泛分布于科孚-凯法利尼亚海槽的更南部区域，以及普利亚半岛南部水下延伸体——普利亚-爱奥尼亚海岭（Apulian-Ionian Ridge）。在岩芯深度超过160 cm处，这些岩芯发育纹层（“纹泥”）带，对应全新世早期（Early Holocene）的北方期-大西洋期（Boreal-Atlanticum）“停滞层（stagnation layer）”，碳十四测年（14C age）年龄约为9000年。
表层沉积物与深层砂层中的陆源组分（terrigenous components）均可来源于普利亚陆架与意大利本土，包括白垩纪普利亚高原、加尔加诺山脉、亚平宁山脉（Apennines）南部以及蒙特武尔图尔火山省（volcanic province of the Monte Vulture）。从重矿物蓝闪石（glaucophane）的产出来看，有少量沉积物可能来自阿尔卑斯物源（Alpine origin）。若将这部分物质视为第一周期碎屑物质（first-cycle clastic material），则其需经亚得里亚海（Adriatic Sea）700 km的纵向搬运才能抵达奥特朗托海峡。粗-中粒陆架样品中缺乏层状硅酸盐（phyllosilicates）的现象，可由“普利亚海流（Apulian Current）”的活动解释：该海流表层流速可达4节（knots，海里/小时），历史上其影响范围几乎可达陆架边缘水深区域。
沉积物中浮游生物（planktonic organisms）的占比以及浮游生物/底栖生物（benthos）比值，是反映水深分区（bathymetry，深度分带）的有效指标。