Stratigraphy, petrophysical characterization and 3D geological modelling of the historical quarry of Nueva Tabarca island (western Mediterranean): Implications on heritage conservation

Abstract

The historical quarry of the Nueva Tabarca fortress (Mediterranean Sea, SE of Spain) was developed in a complex sedimentary Miocene deposit. Five lithostratigraphic units have been defined, including different lithologies such as breccias and microconglomerates (Unit 1), massive and laminated lithoarenites (Units 1, 3 and 5), calcarenites and biocalcirudites (Units 2 and 4). A complete stratigraphic description of this sequence has been carried out, as well as the petrophysical characterization of the most significant lithologies including the analysis of rock durability as well as hydraulic and mechanical properties. Regarding durability, the softest rocks correspond to those from the Unit 4, whilst samples from Units 2 and 5 are the most durable. Three weathering patterns were observed during the artificial ageing test according to both the velocity and intensity of the sample decay. Each pattern is explained according to water-circulation possibility through the rock, its porous system, and the mechanical strength. Rock weathering in monuments of Nueva Tabarca is quantified and discussed according to the results found in the laboratory. Several decay forms are observed in the building stones (mainly differential erosion, alveolization, and rounding forms). Both 3D photogrammetric and 3D geological model of the historical quarry were elaborated in order to quantify the extracted volume of building stones, differentiating the specific quarried percentage of each lithology. Correlation between the results obtained in the volumetric analysis of the historical quarry and the building stones used in the monuments has been carried out. 3D models were also used for determining the remaining rock volume in the current outcrops. Finally, a set of recommendations for future conservation works of the architectural heritage are proposed after the current availability of the different rock varieties and their petrophysical behaviour.

The Role of Calcite Dissolution and Halite Thermal Expansion as Secondary Salt Weathering Mechanisms of Calcite-Bearing Rocks in Marine Environments

“…Given than the thermal stress of halite is roughly equal to the product E•ΔαT•ΔT, where E is the Young modulus (35 GPa for halite) and the thermal expansion mismatch between stone and salt (ΔαT) is 30 × 10 −6 °C −1 approximately, this is about 1 MPa per degree change in temperature. According to this result, the change in temperature from day to night could generate stress exceeding the tensile strength of stone (frequently lower than 10 MPa in this rock types, [22]) This theoretical damage is effective when pores are full of salt, and its effectiveness decreases progressively as the salt filling degree decreases. Previous studies [11] point out that if the pores of a stone become filled with halite, the mismatch in the coefficient of thermal expansion can be destructive.…”

The Origin of Sand and Its Colour on the South-Eastern Coast of Spain: Implications for Erosion Management

“…The studied coast has very diverse habitats: dunes in the south [30], high cliffs of the Betic Cordillera in the north coast of Alicante [31], as well as beaches located on the Nueva Tabarca Island [23]. From a geological standpoint, this coastline is divided into three different domains: the southern sector mainly belongs to the Bajo Segura basin [32,33], the northern one pertains to the Prebetic zone of the External Zones of the Betic Range [34], while the Island of Tabarca is related to the Internal Zones of the Betic Range [35]. The different geological contexts in which the beaches are included establish broadly three different source areas of sediments, which constitute an intrinsic factor that determines natural sand composition and hence the native beach colour.…”

“…The sand used to nourish the beaches came from different sources: (i) submerged sandbanks (e.g., San Juan beach, No. [34][35], sometimes near to the mouth of harbours; (ii) from other beaches (e.g., El Puerto beach, No. 4); and even (iii) from a quarry inland (Fustera Beach,No.…”

Brucite-Aragonite Precipitates as Weathering Products of Historic Non-MgO-Based Geomaterials

“…Petrographically, calcarenites are characterized by a variable content of both bioclasts (mainly algal rhodolith and briozoa fragments) and lithoclasts (rock fragments of both volcanic rocks and limestones), as well as by a variable average grain size, defining both calcarenite (average grain size lower than 2 cm) and calcirudite levels (>2 cm) throughout the stratigraphic deposit. A complete description of these rocks (and the different lithostratigraphic levels) can be found in [17]. Grey limestones correspond to a homogeneous equigranular cryptocrystalline rock with frequent veins filled with white calcite cement ( Figure 1).…”