The tide-dominated Messina Strait (southern Italy) is a 3 km wide marine passageway, whose block-faulted borders form steep subaqueous zones incised by canyons and gullies. These erosional features retreat towards the shorelines and are often in direct connection with subaerial valley-bounded river deltas. High-energy density-flows generated by river floods periodically enter the canyon heads, attaining supercritical-flow regime and accreting large, upslope-migrating bedforms. Although these bedforms have been documented in recent studies, little attention has been paid to the definition of the type of delta entering canyon heads, the internal features of river-influenced deposits accumulated in the nearshore zone, and their interplay with tidal currents flowing axially to the strait. This study focuses on a Lower Pleistocene coarse-grained succession exposed along the north-eastern margin of the modern Messina Strait, investigated using conventional facies analysis and sedimentological logging, integrated with photogrammetric techniques and interpretation of drone-acquired imagery. Facies confinement between basement blocks suggests a subaqueous delta complex shed from the tectonically controlled margin of the ancient strait and entering shallowly submerged canyon heads. Basal breccias, conglomerates and pebbly sandstones exhibiting channel-form discontinuities and upslope dipping backsets are interpreted as cyclic-step and antidune deposits. Units composed of these facies are comprised between master erosional surfaces and tidal ravinement surfaces. The tidal ravinements suggest that canyon infill occurred during a major phase of sea-level rise, punctuated by minor falls and stillstands. These surfaces are overlain by mixed bioclastic–siliciclastic, arenitic, trough and planar cross-strata, representing dunes migrating roughly parallel to the palaeo-coastline and originated by tidal currents amplified by the narrowing of the ancient Messina Strait. Tidal-influenced sedimentation dominated over the fluvial-influenced processes during the late transgression, overfilling the canyon relief. The exceptionally good exposure of depositional architectures and facies characteristics is key to outline the general features of a specific type of delta system, fed by valley-bounded rivers and entering canyon heads in the nearshore of tectonically-controlled, tide-influenced steep strait margins. The pre-existing subaqueous incised topography forced the delta front to be split into lobe branches during the canyon infilling, hampering clinoform architectures and preserving large supercritical-flow sedimentary structures. This study suggests these as possible criteria for the recognition of similar systems in outcrop or subsurface.

中文翻译：

---

接近浅水峡谷头的粗粒三角洲：来自意大利南部下更新世墨西拿海峡的案例研究

以潮汐为主的墨西拿海峡（意大利南部）是一条 3 公里宽的海洋通道，其断层边界形成了峡谷和沟壑切割的陡峭水下区域。这些侵蚀特征向海岸线退去，并且通常与以谷底为界的河流三角洲直接相关。河流洪水产生的高能量密度流周期性地进入峡谷头部，达到超临界流状态并形成大型上坡迁移床型。尽管最近的研究已经记录了这些床型，但很少有人关注进入峡谷头部的三角洲类型的定义、近岸区积聚的受河流影响的沉积物的内部特征，以及它们与轴向流动的潮汐流的相互作用。海峡。本研究的重点是沿现代墨西拿海峡东北边缘出露的下更新世粗粒层序，使用常规相分析和沉积学测井，结合摄影测量技术和无人机获取图像的解释进行调查。基底块体之间的相限制表明一个水下三角洲复合体从古海峡的构造控制边缘脱落并进入浅水淹没的峡谷头。基底角砾岩、砾岩和卵石砂岩表现出通道形式的不连续性和上坡倾倒后倾，被解释为循环台阶和反沙丘沉积物。由这些相组成的单元包含在主侵蚀面和潮汐沟谷面之间。潮汐沟壑表明峡谷充填发生在海平面上升的主要阶段，偶尔会出现小幅下降和静止。这些表面覆盖着混合的生物碎屑-硅质碎屑、砂质、槽和平面交叉地层，代表沙丘大致平行于古海岸线迁移，起源于因古墨西拿海峡变窄而放大的潮汐流。海侵晚期受潮汐影响的沉积作用主导了受河流影响的过程，溢满了峡谷地貌。沉积构造和相特征的异常暴露是勾勒出特定类型三角洲系统一般特征的关键，这些三角洲系统由以山谷为界的河流馈送，并在受构造控制、受潮汐影响的陡峭海峡边缘的近岸进入峡谷头。预先存在的水下切割地形迫使三角洲前缘在峡谷充填过程中分裂成叶状分支，阻碍了倾斜构造，并保留了大型超临界流沉积结构。这项研究建议将这些作为识别露头或地下类似系统的可能标准。