The Making of a Gravel Beach (Cavo, Elba Island, Italy)

This paper presents the history and evolution of the different projects carried out from 1999 to 2008 at Cavo beach in the Elba Island, Italy. The village of Cavo almost completely lost its beach in the 1970s due to the reduction of sedimentary input, and the backing coastal road was defended by a revetment and two detached breakwaters. Such severe erosion processes continued in the following years and impeded any possibility of beach tourist development. In 1999, a project based on the removal of existing breakwaters and beach nourishment works based on the use of gravel as borrow sediment and the construction of two short groins to maintain nourished sediment, raised environmental concern and did not find the approval of the stakeholders. They were worried about the characteristics of the sediments, i.e., waste materials from iron mining rich in red silt and clay. Such sediment fractions made the sea red during the nourishment and deposited on the Posidonia oceanica meadow in front of the beach, with a potential environmental impact. Furthermore, they cemented the gravel fraction forming a beach rock. Between 2006 and 2008, these materials were covered with better quality gravel, extending and raising the beach profile, which required the elevation and lengthening of the two existing groins. Beach evolution monitoring following the second project, based on morphological and sedimentological data acquired before, during and after the works, demonstrated the great stability of the newly created beach. The wider beach has allowed the construction of a promenade and the positioning, in summer, of small structures useful for seaside tourism, increasing the appeal of this village. Data presented in this paper shows an interesting study case, since few examples exist in international literature regarding gravel nourishment projects monitoring and evolution.

Evidence of tsunami deposits in East Tunisia coastline contemporaneous of the AD 365 Crete earthquake: Field data and modelling

<p>New field investigations along the East Tunisian near Sfax coastline reveal sedimentary deposits that may account for a catastrophic event. The sedimentary unit is made of sand coarse gravels, limestone beach-rock, mixed with broken shells of marine gastropods and lamellibranch mollusks, bones and organic matter. Near Thyna, at El Amra site located north of Sfax city, 3.2 m to 3.6 m high late Quaternary coastal terraces are spread over the coastline; they contain a catastrophic deposit that often cover archeological sites of the Roman period. The stratigraphic units show a succession of sandy-silty paleosol truncated by 40 to 70-cm-thick catastrophic unit which is covered in some sites by fire remains overlain by a relatively thin (~10 cm) sandy-silty aeolian unit. The sedimentary succession ends with about 1-m-thick of alluvial deposits and paleosol units. Charcoal samples collected at 10 cm below and 4 cm above the catastrophic units provide radiocarbon dating 236 - 385 cal AD and 249 – 541 cal AD (2s), respectively. Radiocarbon ages bracket the catastrophic unit that may refer to the major tsunamigenic earthquake of 21 July 365 (Mw ~ 8) in west Crete (Greece) reported to have inundated coastlines of Sabratha in Libya and Alexandria in Egypt. The nonlinear shallow water Tsunami-HySEA code is used to perform numerical modelling using 2 different seismic sources comparable to that of the AD 365 Crete earthquake. They feature 2 principal mechanisms that accommodate the Nubia-Aegean convergence along the Hellenic Arc, namely a shallowly dipping thrust-faulting on the subduction interface, as well as a steeper splay faulting in the overriding material. The maximum tsunami wave heights distribution calculated along the Tunisia coast peak in both cases at about 3 meters. The run-up caused by these sources, also considering that we have used uniform slip on the causative fault, can be significantly higher. This proves that the tsunami waves may have reached Tunisia where several coastal cities where severely damaged and reported to have stopped their economic activity. With the identification of the 365 tsunami deposits in eastern coast of Tunisia, the tsunami hazard and risk associated with a major earthquake from the western Hellenic subduction zone cannot be ruled out.</p>

Succession and Colonization Dynamics of Endolithic Phototrophs within Intertidal Carbonates

Photosynthetic endolithic communities are common in shallow marine carbonates, contributing significantly to their bioerosion. Cyanobacteria are well known from these settings, where a few are euendoliths, actively boring into the virgin substrate. Recently, anoxygenic phototrophs were reported as significant inhabitants of endolithic communities, but it is unknown if they are euendoliths or simply colonize available pore spaces secondarily. To answer this and to establish the dynamics of colonization, nonporous travertine tiles were anchored onto intertidal beach rock in Isla de Mona, Puerto Rico, and developing endolithic communities were examined with time, both molecularly and with photopigment biomarkers. By 9 months, while cyanobacterial biomass and diversity reached levels indistinguishable from those of nearby climax communities, anoxygenic phototrophs remained marginal, suggesting that they are secondary colonizers. Early in the colonization, a novel group of cyanobacteria (unknown boring cluster, UBC) without cultivated representatives, emerged as the most common euendolith, but by 6 months, canonical euendoliths such as Plectonema (Leptolyngbya) sp., Mastigocoleus sp., and Pleurocapsalean clades displaced UBC in dominance. Later, the proportion of euendolithic cyanobacterial biomass decreased, as nonboring endoliths outcompeted pioneers within the already excavated substrate. Our findings demonstrate that endolithic cyanobacterial succession within hard carbonates is complex but can attain maturity within a year’s time.

A new species of Petrolisthes (Crustacea, Anomura, Porcellanidae) inhabiting vermetid formations (Mollusca, Gastropoda, Vermetidae) in the southern Caribbean Sea

Petrolisthes virgiliussp. nov. from the Caribbean Sea of Colombia is described. The new species resembles P. tonsorius morphologically but differs from it principally by its color and habitat. Petrolisthes tonsorius is brown or blueish brown and occurs under intertidal boulders strongly exposed to water movement. Petrolisthes virgiliussp. nov. is pale brown to beige and lives exclusively in intertidal areas dominated by vermetid snails, exposed to heavy wave action. The entangled tubular shells of vermetids are cemented to each other and to a hard substrate like beach rock, forming a microhabitat for the new crab species and other porcellanids of the genera Neopisosoma and Clastotoechus. Large genetic distances between DNA sequences of the mitochondrial 16S rDNA gene from P. virgiliussp. nov. and P. tonsorius confirmed that they comprise different species. Petrolisthes virgiliussp. nov. is the 53rd member of the West Atlantic porcellanid fauna.

Quarrying the coasts of Crete in antiquity; some geoarchaeological considerations

The paper discusses three aspects of coastal quarrying in the island of Crete, Aegean Sea, Greece; issues of chronology in regard to the Mean Sea Level in antiquity, issues of ancient technology, and issues of local marble extraction. A series of violent seismic events, the most known being the so-called Early Byzantine Tectonic Paroxysm, affected the morphology of the coastline of Crete, the coastal quarries of which are today either uplifted or sunken. Quarries of aeolianite/sandstone, limestone, marble, and beach rock are related to adjacent rock-cut fish tanks and ship sheds. Traces of the ancient exploitation such as the circular holes observed in the coastal quarries are differentiated according to their dimensions and their natural or manmade form. A preliminary report of a new site, a white marble quarry at Istron (Gulf of Merambello, eastern Crete), is added to the white marble quarries of the area and correlated with the graffiti inscribed on the islet of Prasonēsi or Vryonēsi.

NOTIFICATION SCIENCE: GEOLOGICAL HERITAGE OF BEACH ROCK IN THE LY SON ISLAND

Beach rock (đá bãi biển-BR) hình thành khi lớp trầm tích bãi biển trở nên rắn chắc nhờ tích tụ thứ sinh của cacbonat canxi (canxit, aragonit) kết tủa từ nước ngầm trong đới dao động của thủy triều[1]. Loại đá này từ dễ vỡ tới gắn kết tốt, bao gồm hỗn hợp các loại trầm tích cỡ hạt bột, cát và cuội sạn, có nguồn gốc từ các mảnh thân mềm, san hô, mảnh đá các loại, cả các vật liệu khác như mảnh gỗ, dừa, thậm chí cả vật dụng như chai lọ, mảnh gốm... BR thường là cát sạn kết, nhưng cũng có khi là dăm kết và cuội kết, có cấu tạo phân lớp nằm nghiêng, thường được hình thành dưới một lớp phủ mỏng trầm tích bở rời. Chúng lộ ra do xói lở bờ biển và cát phủ trên bị cuốn đi. BR thường hình thành trong đới gian triều vùng nhiệt đới hoặc cận nhiệt đới, được tìm thấy ở vùng biển Caribe, Địa Trung Hải, Biển Đỏ và vịnh Ả Rập, bờ biển Brazil, Nam Phi, Úc và ở Đông Nam Á. [1]Eric Bird, 2008. Coastal Geomorphology. 2ed. Edition. John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester.

Investigating the existence of a "palaeo-foreshore" zone at Molos beach (Kefalos bay, Paros, Greece).

The present study investigates the existence of a "palaeo-foreshore zone" at Molos beach in or after 1884 A.D., as defined in the Greek legislation (Law 2971/ 19.12.2001). To this end, existing geological and climatological information were gathered, detailed geomorphological mapping was carried out and surficial sediment samples were collected along a shore-normal transect extending from the backshore to the nearshore (subaqueous) zone. In addition, sedimentological /stratigraphical data were obtained from two trenches (1.5 m and 3 m deep) that were excavated on the landward side of the coastal dunes. Topographic maps, aerial photographs and satellite images are used to study the recent changes of the shoreline position. On the basis of the above, it is concluded that the current backshore zone has recently evolved from a shallow lagoonal, to a terrestrial environment. The submerged beach rock formations are at similar water depths (0.3-0.4 m) with those observed in other islands of the Cyclades complex (i.e. Rhenia, Naxos) whose formation has been radio-carbon dated at least 200 years BP, indicating that the 1884 A.D. shoreline was not landward, but approximately 15 m offshore relative to its present position