Inventory and Quantitative Assessment of Coastal Geoheritage: Contribution to the Proposal of an Active Geomorphosite

Abstract

The geoheritage present on the “Tindari Cape and Marinello Lakes” site (TCML, Messina Province, NE Sicily, Italy) drew our attention due to the acquired contrasting information. Indeed, the TCML geoheritage was classified in the geosite national catalogue as a geosite (albeit under a non-evaluated status and with regional scientific interest), whereas it was classified in the geosite regional catalogue as a site of attention. The coastal geoheritage included in this site was analyzed by means of a literature review, field work, and a sedimentological and petrographic investigation. Moreover, the reconstruction of the historical to modern evolution of the lagoon and spit’s shapes was carried out across a time span of 85 years. The investigation results were used for the inventorying and quantitative assessment of the TCML geoheritage with the Brilha method. The primary and preeminent scientific interest was geomorphological, the lagoon and spit being an active geomorphosite. This system showed elements of rarity, representativeness, and exemplariness. Secondary-type geomorphological, structural, and palaeontological aspects were also evidenced in geological elements found on the cliffs of the Tindari Cape. For the quantitative assessment of the geodiversity, the scientific value (SV), potential educational use (PEU), potential touristic use (PTU), and degradation risk (DR) were evaluated. The obtained weighted scores were 320 (SV), 250 (PEU), 290 (PTU), and 285 (DR). The high SV suggested that the TCML, due to its geodiversity, could be classified as a geosite. Notwithstanding, the moderate PEU, PTU, and DR (fragility and vulnerability depending on natural climate and anthropogenic factors) values indicated that it was not fully compatible with educational and touristic purposes. The results of the inventorying and quantitative assessment of the TCML site provide scientific data that are useful in establishing the TCML as a global geosite, placing it in the national catalog of geosites.

1. Introduction

Geoheritage refers to objects and sites of geological interest and their relationships with cultural, esthetic, educational, and scientific values [1].

According to Wimbledon [2,3], a geosite is a locality, area, or territory in which it is possible to identify a geological or geomorphological interest for conservation, but also an area or a locality that represents, in an exemplary way, the history and development of geological and geomorphological events, acting as a model for a large swath of territory or a portion of the geosphere that is recognizable and accessible on the Earth’s surface, spatially limited and clearly distinguishable from the surrounding areas, in relation to defined geological characteristics and processes. The main mission in establishing geosites is to protect such sites and promote geoconservation to support geological research, education, and training [3]. Recently, Migoń [4] described geosites as windows into the geological past, which may be recorded in rocks and their properties, the fossil content, and landforms produced by processes that are no longer operating.

Geosites and geodiversity sites are considered in-situ geodiversity [5] (Figure 1). When in-situ geodiversity exhibits high scientific value (SV), independently of its potential educational and touristic uses (PEU and PTU) and degradation risk (DR), it may be classified as a geosite [5] (Figure 1). On the other hand, the in-situ counterpart of a geosite is a geodiversity site (Figure 1). Indeed, when the in-situ geodiversity does not exhibit high SV, the site may be classified as a geodiversity site (Figure 1).

There are several qualitative vs. quantitative approaches to geodiversity for the measurement of the main values or potentials. Indeed, in the last decade, growing interest in geoheritage evaluation has led to the proposal of several quantitative methodologies and tests to achieve better practices. Among them, the method reported by Brilha [5] represents one of the most appreciated approaches due to the completeness of the information provided on the SV, PEU, PTU, and DR. In this method, mainly based on a critical review of the literature, the quantitative assessment of geodiversity is carried out, evaluating the weights of scores attributed to thirty-seven criteria/indicators.

Zafeiropoulos and Drinia [6] carried out a quantitative assessment of the geoeducational value of five geosites by applying both the Brilha method [5] and the M-GAM method. The first method evidenced geological values showing relatively high scores. The second method, considering also the opinions of site visitors, provided lower scores for the geological values, being moderate.

Herrera-Franco et al. [7] analyzed ten geosites by comparing the results of the application of three different approaches (the Brilha method, the method used by the Geological and Mining Institute of Spain, and the methodology of geosite assessment) in order to obtain procedural considerations in the evaluation of geodiversity. The data obtained in the comparative analysis were organized in a matrix and described in guidelines, providing an integrated method. The results of the comparative approach showed similar rankings for the examined geosites. Moreover, the prioritization of determined aspects was highlighted.

Recently, the Brilha methodology was integrated with a multi-criteria group decision-making method to test the quantitative approaches [8]. This method consisted of applying the same criteria reported by Brilha [5] but applying the Improved Fuzzy Stepwise Weight Assessment Ratio Analysis technique. The determination of the geoheritage importance degree was achieved by using the rough measurement of alternatives and ranking method, according to the compromise solution technique applied to the weighted criteria.

A qualitative–quantitative approach for the quick recognition of geosites was recently applied by Zakharovskyi et al. [9]. This methodology was aimed at obtaining a form of prioritization in the search for potential geosites, by using a general geodatabase and digital elevation models (DEMs).

In Italy, besides a National Inventory of Geosites [10], there are also regional inventories of geosites.

Since 2002, the Higher Institute for Environmental Protection and Research (ISPRA) [11] has been required to edit the national inventory [10]. Geosites may be of local, regional, or national interest. In the latter case, national geosites must be established by the ISPRA. For including a potential geosite in the national inventory [10], it is necessary to fill out a form reporting twenty main types of data. These are the geosite name, dissemination, compiler, type of data acquisition, location, scientific interest, degree of primary scientific interest, description, images, lithology, geochronological unit, genetic process age, type of interest, exposure, position, accessibility, land use or type of seabed, protected area, state of conservation, and protection proposal [10]. Furthermore, the potential geosite needs to possess three main scientific characteristics: representativeness, rarity, and exemplarity [10]. Representativeness is related to the notion that the geodiversity under study represents the “best” available in a certain area. The concept of rarity is evaluated by considering the geographical area. Indeed, the type of geodiversity under study may be rare in a certain region and abundant in others. Exemplarity concerns the notion that the geodiversity under study may be used to describe a certain form or process [10].

The National Inventory of Geosites includes approximately 3000 geosites of local, regional, national, and international interest and GSSP (Figure 2), and this number is continuously growing [10]. The inventory represents a useful database, supporting the Italian Ministry of Environment and Energy Security (MASE) [12], universal global organizations (such as the Global Geopark Network of UNESCO or the Food and Agriculture Organization of the United Nations (ONU)), or public institutions to better manage practices, search for strategies and resources, and advance policies for the protection of geodiversity.

According to the geodatabase, it appears that the distribution of geosites in the different regions is strongly inhomogeneous, ranging from 0.2% per km² (in Lombardy and Puglia) to 1.9% (in Liguria), and it is independent of the regional areal extension. Indeed, Val d’Aosta and Sicily, which are the regions with the lowest and highest areal extensions and contain 41 and 142 geosites, respectively, show ratios above (1.3%) and below (0.6%) the national mean value (0.8%) (Figure 3).

In this paper, particular attention is paid to the Sicilian Regional Catalogue of Geosites [13], established in 2012 by the regional Department of Territory and the Environment. According to the Sicilian Regional Law on “Rules for the recognition, cataloguing and protection of geosites in Sicily” (Sicilian R.L. 25 of 11 April 2012), and the subsequent implementation decree of the Regional Councilor for Territory and the Environment (Sicilian I.D. 87 of 11 June 2012), the cataloguing of the Sicilian geodiversity was foreseen, followed by its protection with specific rules. Based on an increasing degree of detail, the Sicilian geosites were classified as reported, proposed, or inventoried. Then, in 2016, the Sicilian geodiversity was inventoried into three classes, attributed on the basis of a decreasing degree of progress in the establishment procedure (Sicilian I.D. 289/GAB of 20 July 2016). The classes were:

• Geosites (i.e., only sites established pursuant to I.D. 87/2012);
• Sites of geological interest (i.e., sites of recognized scientific interest that would be progressively established);
• Sites of attention (sites whose information, rarity, and representativeness needed to be confirmed by scientific investigation so that they could be subsequently included among the sites of geological interest).

Nowadays, the Sicilian geosites mostly include the sites established pursuant to Sicilian I.D. 87/2012 in the geological reserves (Sicilian I.D. 283 of 29 August 2017).

Among the nine Sicilian provinces, the largest number of geosites and sites of geological interest is found in Messina (3247 km²) [13], the province with the second-largest areal extension after Palermo (Figure 4). The mean distribution of the Sicilian geosites per km² ranges from 0.1% (Enna and Ragusa) to 1.4% (Messina) (Figure 4), with an average mean of 0.4%, apparently related to the province’s areal extension. Indeed, Messina and Enna-Ragusa, which are among the provinces with the highest and lowest areal extensions (Figure 4), show ratios above and below the mean value (0.4%), respectively. However, this correlation might only be apparent due to specific circumstances. Indeed, among the 45 geosites in Messina (D.A. 283 of 29 August 2017), forty belong to the UNESCO heritage, and they are all concentrated within a small area in the volcanic framework of the Aeolian arc (114.7 km²). Consequently, on these islands, the percentage of geosites per km² reaches 34.8%, the highest across the entire nation. By contrast, only five geosites are present in the remaining areas (3132.3 km²) of Messina, covering only 0.16%. This value, when compared with the national mean, leads to asking some questions regarding the factors responsible for this evident gap.

Among the Sicilian geosites, the site “Tindari Cape and Marinello lakes” (TCML) (Patti, Messina, Lat. 38.1412; Long 15.0527) drew our attention due to the acquired information on the national and regional catalogs. Indeed, according to the national inventory’s geodatabase [10], the TCML geoheritage is an areal geosite of regional scientific interest, but its status has not been evaluated since 31 December 2010 (ID geosite: 2716). Moreover, it is reported in the explanatory attribute table that this geosite does not show elements of rarity, representativeness, or exemplarity and is characterized by a medium anthropogenic risk and low natural risk [10]. In contrast, according to the classification of the regional Department of Territory and the Environment [13], the TCML geoheritage is not considered a geosite but a site of attention (as officially communicated after requests for information on the status of this site).

In contrast, according to a literature review, field surveys, and analyses, it appears that the TCML site has great geodiversity potential due to the peculiarities of the brackish lagoon (with four main lakes and a spit) and the Tindari Cape cliffs. Indeed, the site boasts outcrops, landscapes, and landforms with a wide range of geomorphological, geological, and palaeontological peculiarities.

With this in mind, the present research was devoted to the investigation of the geoheritage value and potential preserved in the Oliveri–Tindari coastal system. Other secondary geological elements of great scientific interest present on the Tindari Cape, such as an uplifted cave with vertebrate remains, lithophaga holes, and marine notches, were also described to provide useful and complementary elements for the geosite’s establishment. In this respect, the necessary scientific background for the upgrading of the status of the TCML in both the national and regional catalogues of geosites is provided after applying the Brilha method [5] for the quantitative assessment of its geodiversity. Moreover, the present work intended to fill a major knowledge gap regarding the coastal geoheritage, as there are very few published studies on this topic, and studies of such rapidly evolving landforms and systems are rare.

2. Materials and Methods

Geological, geomorphological, sedimentological, and petrographic observations were carried out on the TCML interim geosite. The results of these investigations, coupled with a review of the ancient to recent literature, were used for a quantitative assessment of the geodiversity present in the TCML site and its inventorying.

2.1. Study Area and Geological Background

The TCML site includes the Oliveri–Tindari Lagoon and the Tindari Cape cliffs facing the Sicilian Tyrrhenian coastline on the central–northern edge of the Peloritani Mountains (Figure 5).

The Oliveri–Tindari Lagoon (falling within the Marinello locality, close to Oliveri Village) is also known as the Marinello Lagoon or Marinello coastal wetland system. The Oliveri–Tindari Lagoon is formed by a sand spit, including a brackish system located east of the Tindari Cape promontory (see square with black line in Figure 5). The spit developed in a transitional environment, representing a very complex and challenging system. It shows continuous landscape modifications that were undergone in the last few centuries, because of the strict interaction existing between emerged lands and marine submerged sandbanks.

The geological and structural framework of the headland characterizing the study area is related to the Alpine thrust belt of the Peloritani Mountains (Calabria–Peloritani Arc) [14,16,17]. The thrust belt is composed of a different number of tectono-stratigraphic units [14,16,17], according to the different schools of geologists. In the present research, we identified five units (from top to base, Figure 5): the Aspromonte Unit (including, at its stratigraphic base, metamorphic rocks previously attributed to the Mela Unit), the Mandanici–Piraino Unit, the Alì–Montagnareale Unit, the Fondachelli Unit, and the Longi–Taormina Unit. Most of them are composed of Variscan very low- to high-grade basements overlain in unconformity by Mesozoic and Mesozoic to Cenozoic sedimentary successions. A few exceptions exist. The Aspromonte and Alì–Montagnareale Units are not provided with sedimentary cover or a Variscan basement, respectively, whereas the Aspromonte, Mandanici–Piraino, and Alì–Montagnareale Units are affected by an Alpine metamorphism [18,19,20,21].

Research published in national and international journals describes the geomorphology, geology, paleontology, structural geology, and ecology of the study area [15,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49].

2.2. Particle Size Analysis and Textural Parameters

Previous particle size and textural analyses of the lagoon sediments date back to the 1980s [27,28] and 2020 [48].

New particle size analyses of the lagoon sediments were carried out in the present research by means of dry mechanical sieving, performed according to Wentworth [50]. The twelve ASTM sieves used had sieve openings between −4.2 and 4 phi (−4.2, −3.6, −3.2, −2.7, −2.2, −2.0, −1, 0, 1, 2, 3, 4 phi). The instrument used was an automatic mechanical sifter (Retsch, model AS2, Haan, Germany). After the mechanical sieving, each size fraction was weighted and separated in different sample holders for mineralogical and textural observations. Statistical textural parameters (mode, mean and median, sorting, skewness, and kurtosis) were calculated according to Folk and Ward [51] and elaborated in GRADISTAT version 8 (software).

2.3. Petrographic Analysis

A major knowledge gap regarding the sedimentary petrography of the lagoon sediments was evidenced. As knowledge of the petrographic features is useful in inventorying geoheritage sites and enabling advances in provenance studies, petrographic analyses were also carried out.

The main mesoscale compositional features of the sediments were defined using a magnifying glass. Microscopic analyses were performed in incoherent sediments, as well as in thin sections of sediments aggregated in epoxy resin. The petrographic instruments used were a stereomicroscope (Zeiss, Stereo Discovery model, Oberkochen, Germany) and a petrographic microscope (Zeiss, Axio Vision model, Oberkochen, Germany), both coupled to a telecamera and workstation using image analysis software (Zeiss Axiovision, version 4.6, Oberkochen, Germany). Most of the minor minerals, present in the finest fractions, were detected under a stereomicroscope, observing the grain luster, color, habitus, and cleavage when preserved. Additional Raman analyses were used to confirm the mineralogical determinations of heavy minerals in trace amounts.

2.4. Brilha Method for the Inventorying and Quantitative Assessment of Geodiversity

The literature on geoconservation and methods for qualitative vs. quantitative assessment is rich [1,2,3,4,5,6,7,8,9,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88].

The Brilha method [5] was chosen to assess the geoheritage values and potentials of the TCLM site because, based on a critical review of the best scientific research, it has been one of the most used methods in the last decade. According to this method, high SV is the main requirement for the consideration of a geosite as in-situ geoheritage. Moreover, a geosite must provide unequivocal representations of geological history and evolution, accompanied by elements of rarity, and it must represent a significant site for future research, memory, and geoconservation [5]. Low or high values of PEU and PTU are not discriminant, but high PEU and/or PTU in a geosite may be allowed only if the DR is low [5]. In the case of an elevated DR, the geosite must be preserved with priority with respect to geodiversity sites and protected from possible damage caused by stakeholders and natural or anthropogenic phenomena. For this reason, geodiversity sites represent the counterparts of geosites [5].

The quantitative assessment performed by the Brilha method is based on the evaluation of four criteria: SV, PEU, PTU, and DR (Figure 6). These criteria are described by a total of 37 indicators associated with the parameters/scores synthesized in Figure 6 and based on from the third to ninth table reported by Brilha [5]. The scores (0, 1, 2, 3, 4) attributed to each indicator are based on the three to four specific descriptions (see the third, fifth, and seventh table reported in Brilha [5]) that best fit with the characteristics of the studied geoheritage. The scores are finally weighted (see the fourth, sixth, and octave table in Brilha [5]) and multiplied by a factor of 100 (total weighted scores).

The evaluations of the TCML geoheritage were carried out by using information provided via the scheme reported in Figure 6. To establish whether the studied TCML site may be inventoried as a geosite or geodiversity site, three main categories of geodiversity, based on the total weighted scores attributed to the SV criterion [5], were distinguished: high, medium, and low (

Table 1. Categories of in-situ geodiversity on the basis of the total weighted scores for the criterion of scientific value (SV). The total weighted scores were multiplied by a factor of 100. Geodiversity with high SV (score: 301–400) may be classified as a geosite, whereas geodiversity with moderate to lower SV values may be classified as a geodiversity site.

Scientific Value Total Weighted Score Interval	Category
0–200 (Low)	Geodiversity site
201–300 (Moderate)	Geodiversity site
301–400 (High)	Geosite

).

The evaluations of the studied site’s geodiversity were independently performed by three researchers who possessed expert knowledge of the site, and only the mean scores were considered and reported in the present paper.

3. Results

The TCML site (Figure 7) falls within the Oriented Natural Reserve (ONR) “Laghetti di Marinello”, established in 1998 because of the important biodiversity and ecosystems (I.D. 745/44, 10 December 1998). Indeed, the area was protected for a long time as a result of its high scientific value in the biological field due to the significant biotope, as well as its unique coastal aquatic ecosystem and faunistic and floristic peculiarities [23,24,25,26,27,28,31,32,36,40,48].

The functioning of this peculiar Mediterranean coastal ecosystem is strongly influenced by both biotic and abiotic factors [23,27]. The ONR develops for about 3.67 km² in the middle of the Gulf of Patti (43 km long), between the Cape Milazzo to the east and the Cape d’Orlando to the west (Figure 5). The reserve was also included in a Site of Community Interest (SIC; ITA030012 Oliveri–Tindari Lagoon) based on the European laws governing the Rete NATURA 2000, devoted to the protection of wild fauna and migratory birds. The areal extension of the ONR and SIC coincides. The TCML site, belonging to an ONR established for biodiversity but not for geodiversity, unfortunately was not included among the 93 Sicilian geosites established in the natural reserves and created for geological reasons, as occurred instead for the two global geosites established in the brackish coastal lagoon of Cape Peloro in Messina (Figure 5) [87,88].

3.1. The Geoheritage of the Oliveri–Tindari Lagoon and Spit

Coastal lagoons with brackish lakes are usually associated with sandy spits. Classified as recurrent, temporary, or occasional, these may form due to longshore coastal drift in headlands and show shapes with angles greater than 30° [89,90].

The Oliveri–Tindari Lagoon is affected by continuous and active shape modifications. It currently shows a triangular shape with brackish ponds that are stretched and sub-parallel to the steep cliffs of the Tindari Cape headland, with a main NW-SE trend. The semi-permanent brackish ponds in the lagoon, from north to south (Figure 7 and Figure 8), are

• Verde Lake (VL, areal extension: 7039 m²);
• Porto Vecchio Lake (PVL, areal extension: 23,490 m²);
• Mergolo della Tonnara Lake (MTL, areal extension: 26,645 m²);
• Marinello Lake (ML, areal extension: 26,780 m²).

Remnants of an extinct pond (Fondo Porto Lake, FPL) that was formerly connected with the Verde and Mergolo della Tonnara Lakes through an artificial canal are yet recognizable as marshy depressions during the rainy season.

Bathymetric surveys carried out in the ponds between 1978 and 2006 reported depths of around 3–4 m [27,28].

The hydrogeology of the ponds is almost differentiated, since the ponds close to the cliff are mainly influenced by rainfall and groundwater, whereas the ponds near the shoreline are mainly influenced by seawater infiltration and direct inflows during storms [27].

At the east, the lagoon ends with a kilometer-long wave-dominated coarse sandy–gravelly spit [40,43,44], positioned at a high angle (about 70°) with respect to the rock cliffs of the Tindari headland (Figure 8).

The shape of the submerged Oliveri–Tindari Lagoon, achieved over centuries, is roughly semi-circular and easily observable on satellite imagery up to almost a 10 m depth, although it actually extends seaward up to the 30 m isobath [27].

A belt composed of Holocene beachrocks occurs in the lakes and along the NW coast of the Tindari Cape. Such a formation was identified for the first time in the lakes by Crisafi et al. [27] as a 3 m-wide belt developed in the intertidal zone of the Mergolo della Tonnara Lake. The beachrock, consisting of siliciclastic rocks ranging from fine sands to conglomerates, was also observed along the coastline among the 1.50 m and 2.50 m isobaths [44].

The beachrock’s areal extension, detected during our field surveys in the intertidal zone around the shores of the Mergolo della Tonnara and Porto Vecchio Lakes and the Marinello–Oliveri marine coast, is indicated in Figure 8 and shown in Figure 9a,b.

Coastal dunes are present along the northernmost side of the lagoon and spit (Figure 8 and Figure 10).

3.1.1. Origin and Evolution of the Oliveri–Tindari Lagoon and Spit

Land accretion and erosion are typical phenomena affecting transitional environments such as the coastal strip [89,90].

In the TCML interim geosite, the landscape shape of the brackish ponds and sand spit has changed over the centuries due to intense variations depending on the coastal dynamics, sediment supply, and storms.

Some relevant data, deduced from the analysis of historical maps and the literature [43], enabled us to delineate the main events responsible for their origins. It is hypothesized that the historical catastrophic seismic events that hit Tindari, destroying most of the homonymous city, also caused block detachments on the eastern side of the promontory and the consequent collapse of these materials at the base of the cliff and into the sea, which is still observable nowadays. The degradation phenomena contributed to notching the promontory, facilitating the block’s collapse along weakened mechanical planes (joints and faults) diffused along the cliffs (Figure 8). Archaeological remains (bricks and mortars) discovered underwater and reported by Ignazio Paternò Castello (1719–1786) seem to confirm this hypothesis [43]. The consequent modification of the configuration of the seabed due to fall-type landslides could have been responsible for the initial onset and growing of the spit [34,37,38,41,43]. The progressive formation of the coastal ponds, due to the action exerted by the Tindari promontory, favored sedimentation in areas with the lowest wave energy eastwards [43]. Concerning landscape modifications due to human activities, it was hypothesized that a littoral drift increase could have occurred due to anthropogenic causes, beginning in the mid-1800s (1877 according to the Hydrographic Institute of the Navy) [43]. Indeed, historical and recent sources and maps testify that consistent deforestation phenomena occurred during the 1700–1800 period in the hinterland between the Tindari Cape and Capo d’Orlando westward. This relief consequently underwent significant erosion, responsible for flooding and the transport of alluvial sediments, nourishing this sector of the Tyrrhenian coast [43]. Following this epoch, the lagoon underwent continuous modifications due to coastal dynamics with different intensities, extending to the present. In particular, the spit, with its actual E-W trend, was also cut over the centuries and modified by storms; it has continuously evolved, moving southeastwards, progressively reducing the connections between the sea and lagoon [43].

The development of inlets along the spit was responsible for the progressive advancement of ephemeral lagoons or semi-permanent brackish lakes [23,28]. The first evidence of the onset of a brackish lagoon with three lakes was provided only by oral witnesses in 1805, as reported by Abbruzzese and Aricò [23]. The shoreline appeared stretched along the steep cliff of the Tindari Cape promontory, and, in 1880, the Verde, Mergolo della Tonnara, and Marinello Lakes were yet recognizable [27]. Before this epoch, the Tindari Cape was directly exposed to the marine wave and current actions, and a spit protected an ancient harbor [27]. Variation in the number of lakes was observed in the 19th, 20th, and 21st centuries. Since the 1980s, anthropogenic activities upstream of the lagoon have been responsible for a decrease in the sedimentary supply, resulting in the modification of the spit’s shape and the number of brackish lakes [48].

Indeed, while seven ponds were reported in 1985, namely the Marinello, Mergolo della Tonnara, Verde, Porto Vecchio, Fondo Porto, Nuovo, and Piccolo Lakes [48], which were recognizable until the end of the 1980s (according to a satellite image from 1989), only six remained after ten years (according to a satellite image from 1999) due to the concomitant erosion and interring of the Lake Piccolo pond.

For a detailed reconstruction of the lagoon and spit system’s evolution, see Crisafi et al., Crisà et al. [43], and Leonardi et al. [40,48].

3.1.2. Spatiotemporal Evolution of the Oliveri–Tindari Shoreline

The reconstruction of the spatiotemporal evolution of the Marinello (Oliveri) shoreline, occurred across a time span of 85 years (1938–2023), is provided in a simplified sketch map (Figure 11). This reconstruction was based on historical and modern topographic maps from the Istituto Geografico Militare Italiano (IGMI) and technical maps of the Sicilian region (1938, 1967, 1978, 1985, 1999, 2006, 2013), as well as satellite imagery from Google Earth Pro (from 1985 to 2023), taking into account also the literature review [23,27,33,40,43,48] and direct field trips to the study area. The maps and satellite imagery were georeferenced, considering as a reference point the steep cliff of the Tindari Cape (coordinate system: EPSG3857). The reconstruction was carried out using the QGIS (3.28 “Firenze”) software.

In Figure 11, two sand spits with several inlets, NW-SE-trending, are clearly distinguishable in 1938 (light blue line in Figure 11) and 1967 (pink line in Figure 11). The northernmost and southernmost spits were approximately located north and south of the actual Tindari–Marinello spit. In 1985, the number of spits (and inlets) was reduced to only one, maintaining a NW-SE orientation (light brown line in Figure 11). Observing the satellite imagery, the spit showed a hook shape, defining an evident inlet since 1985. The spit’s orientation underwent counterclockwise rotation, evolving from a NW-SE trend to a straight E-W orientation from 2005 to the present. This rotation was also accompanied by the progressive displacement of the spit southwards (Figure 11).

The shape of the submerged lagoon bed, at depths < 10 m, exhibits two bars south of the actual sand spit (one presumably formed in 1938) (Figure 11). The easternmost shape around the actual spit edge was presumably achieved in 1999 (dark brown line in Figure 11). Between the actual spit and Marinello Lake, suspensions of light brown fine sediments derived from the erosion of submerged ancient lagoon beds may still be occasionally observed (Figure 10b).

For a detailed reconstruction of the morphological evolution of the Marinello system, from 1967 to 2013 (including the brackish lakes), and the relative quantitative evaluation of the accretion and shrinking phases, see Leonardi et al. [48].

3.1.3. Textural and Mineralogical Observations

Previous textural analyses carried out in 1978–1979 on bottom samples from all ponds indicated sediments ranging from fine to very coarse, with low to high standard deviations [27,28,48].

Preliminary textural observations carried out by the authors on beach deposits along the shoreline indicated that they were characterized by pebbly–sandy sediments. The average texture of the five collected samples (TB14–18) was characterized by mean diameter average values equal to 2.7 mm. They consisted of sandy, very fine gravels, moderately sorted and with mesokurtic and symmetrical grain size distributions.

Preliminary optical mineralogical observations of the grains of these sandy, very fine gravels indicated that the main components were metamorphic lithoclasts (Figure 12a–n), with a minor contribution from sedimentary grains (Figure 12o–q). The metamorphic lithoclasts consisted of well-rounded grains, mainly derived from light greenish chlorite- and light grayish sericite-bearing phyllites (Figure 12e–h), with angular to rounded light minerals (hyaline quartz and feldspars, Figure 12a,d). Other minor metamorphic lithoclasts were represented by well-rounded grains of graphite-bearing phyllites (Figure 12g). Gneiss (Figure 12i) and marbles (Figure 12j) were also identified. Traces of heavy minerals of metamorphic (yellow garnet and dark yellow staurolite) and volcanic origin (dark green pyroxene) were also found. Garnets and staurolite showed angular to rounded shapes (Figure 12k,l), whereas pyroxene preserved its crystalline habitus but showed etching traces (Figure 12m,n). Minor quantities of lithoclasts composed of light brown chert and Verrucano-type dark red metasandstones and metapelite were also recognized (Figure 12o,p).

3.2. The Geoheritage of the Tindari Cape Promontory

The Tindari Cape promontory is dominated by the polymetamorphic basement of the Aspromonte Unit (Figure 5 and Figure 13). This basement was affected by a Variscan medium to high metamorphism, intruded by late Variscan plutonites, and locally overprinted by an Alpine metamorphism [14,16,17,18,19,20,21]. The eastern slope of the promontory exhibits a steep cliff at the base, slightly evolving upwards to a less inclined slope. The different morphology is strictly dependent on the rock composition of the substrate. Indeed, the steep cliffs and escarpments (almost subvertical and about 250 m thick) are mostly composed of light gray marbles interlayered by paragneiss and micaschists (Figure 13 and Figure 14a), whereas the overlying layers are mainly represented by paragneiss and micaschists intruded by thick to thin aplo–pegmatitic dikes. At the cliff foot, a discontinuous belt of debris derived from previous rockfall is present onshore (also within the Verde and Mergolo della Tonnata Lakes) and offshore. In particular, the marbles are two-mica bearing and mylonitic, testifying to an Alpine mylonitic phase, which is still observed in other areas of the chain (unpublished data of the authors). The marbles and paragneiss exposed along the Tindari cliff are affected by two main systems of faults, a NNW-SSE-trending right lateral transtensive system (the Tindari–Novara di Sicilia fault system) and a WSW-ENE-trending normal fault system (Figure 13 and Figure 14b).

The main fault system occurring in the Tindari promontory is NNW-SSE-oriented and belongs to the Tindari–Novara di Sicilia fault system, characterized by right-lateral transtensional movements [15,35,45]. This kinematics, confirmed by unpublished structural data of the authors, is associated with a system that is still active, as indicated by the local seismicity present in the area and recorded in historical times (earthquakes during the first century and 365 B.C.). The Tindari fault is considered a 14.5 km long capable normal fault, reported onshore and offshore in the maps of the ISPRA catalog of capable faults (Italy Hazards from Capable Faulting, ITHACA, code: 12700) [91]. This system presumably occurred after the onset of ENE-WSW-trending normal faults affecting the promontory (Figure 13 and Figure 14a,b).

Additional geological elements of scientific interest were identified at two sites along the northernmost edge of the steep cliffs of the Tindari Cape (Figure 13).

The Donnavilla Cave (Lat: 38°9′3.89″ N, Long: 15°2′44.39″ E; Figure 15a–c) provides important morphological and palaeontological evidence, including endemic mammal deposits (Dama carburangelensis, Cervus elaphus siciliae, Hippopotamus pentlandi, Ursus cf. arctos) [39] (Figure 15d). Evidence of the uplift of a Late Quaternary coastline is provided by the endolithic bivalve Lithophaga lithophaga holes affecting the external and internal marble walls of the cave located at 60 m a.s.l. (Figure 15c) [39]. The mammal deposits should be compatible with other Upper Pleistocene continental sedimentary deposits, unconformably lying on Tyrrhenian abrasion terraces, widespread in the Peloritani belt and distributed at elevations between 80 and 105 m a.s.l. [39]. It is presumable that the marbles hosting the Donnavilla Cave underwent down-throwing with displacement of about 30 m along recent normal faults [39]. A structural investigation carried out by the authors indicated that the cave presumably developed along a NNE-SSW-trending system of faults (Figure 15a,b).

Access to the cave in the past was represented by a very complex and dangerous dirt path, being very narrow and facing a steep cliff that was 60 m high, without safety structures (fence).

Along the rocky coast at Cape Tindari, different Holocene marine notches were identified [38,44]. The lowest one was a marine-submerged notch, lying at the 2 m isobath. The other two were found at 5 m and 6 m a.s.l., respectively, along the crags [38]. These emerged and uplifted notches were also associated with the remains of littoral gravels and marble pebbles with lithophaga holes. The uplifted and submerged roof notches were dated between 6.5 and 5 ka cal BP [44].

Access to the site showing emerged and submerged notches is only possible by boat or swimming.

3.3. Quantitative Assessment of Geodiversity

Based on the geoheritage present in the Oliveri–Tindari Lagoon/spit and the geological elements identified on the Tindari Cape cliffs, the extension of the TCML interim geosite would cover the entire Oliveri (Marinello)–Tindari Lagoon (corresponding to a sector of zone A of the ONR) and the northernmost steep cliffs facing the Tindari Cape (corresponding to a sector of zone B of the ONR).

3.3.1. Scientific Value

Seven indicators [5] were considered to assess the SV (

Table 2. Evaluation of indicators A–G for the assessment of scientific value (SV) (see Figure 6).

Scientific Value (4–2–1)	Weight (%)	Score	Weighted Score
A. Representativeness	30	4	1.2
B. Key locality	20	1	0.2
C. Scientific knowledge	5	4	0.2
D. Integrity	15	4	0.6
E. Geological diversity	5	4	0.2
F. Rarity	15	4	0.6
G. Use limitations	10	2	0.2

). The selection of the score was performed using the descriptions and corresponding scores reported in the third table of Brilha’s work [5].

The “representativeness” value was high, indicating that the site is one of the best examples of a geological framework related to the Quaternary record and coastal brackish lagoon dynamics. The “key locality” value was low, indicating that the site is a reference for the geological framework at national scale. The “scientific knowledge” value was high, because of existing international papers devoted to the geological framework. The “integrity” value was high, because the geological framework was very well preserved. The “geological diversity” value was high, with more than three different geological elements of scientific interest. Indeed, the findings of Upper Pleistocene continental mammal fauna inside the Donnavilla Cave, as well as Holocene Lithophaga lithophaga and marine-submerged and sub-aerial notches at different elevations, represent different significant geological elements. The “rarity” value was high, because the site is the only occurrence of this type of geological framework at regional scale. The “use limitations” value was intermediate, indicating that it is possible to carry out sampling and field work activities after obtaining the permission of the management authorities of the reserve.

3.3.2. Potential Educational Use

Twelve indicators [5] were considered to assess the PEU (

Table 3. Evaluation of indicators A–L for the assessment of potential educational use (PEU) (see Figure 6).

Potential Educational Use (4–3–2–1)	Weight	Score	Weighted Score
A. Vulnerability	10	4	0.4
B. Accessibility	10	1	0.1
C. Use limitations	5	2	0.1
D. Safety	10	2	0.2
E. Logistics	5	4	0.2
F. Density population	5	3	0.15
G. Association with other values	5	4	0.2
H. Scenery	5	3	0.15
I. Uniqueness	5	4	0.2
J. Observation conditions	10	2	0.2
K. Didactic potential	20	1	0.2
L. Geological diversity	10	4	0.4

). The selection of the score was performed using the descriptions and corresponding scores reported in the fifth table in the work of Brilha [5].

The first ten indicators (A–J, Table 3) used to assess the PEU and PTU, being the same, were applied once, but we used different weights for H-I-J (Table 3). As regards the “vulnerability” value, the geological elements did not show a possible deterioration risk due to anthropic activity, although elevated deterioration risks due to natural phenomena, such as possible landslides and block falls along the deep marble slope facing seawards, are present (see DR). To this value, we attributed an intermediate score. The “accessibility” value was low, with the site having no direct access by paved roads. The “use limitations” value was intermediate, with the site being accessible after overcoming limitations. The “safety” value was intermediate, as the site was not provided with safety facilities but had mobile phone coverage and emergency services at less than 50 km (Patti Hospital). The “logistics” value was high, with the site possessing lodgings and restaurants for groups of 50 persons less than 15 km away. The “density population” value was medium–high, with the site being in a municipality with 250–1000 inhabitants/km² (Patti inhabitants: 252.58 in./km²). The “association with other values” value was high, with the site possessing several ecological and cultural elements less than 5 km away. The “scenery” value was intermediate–high, with the site being occasionally used as a tourism destination in national campaigns. The “uniqueness” value was high, with the site possessing unique and uncommon features. The “observation conditions” value was medium–low, as the site exhibited some obstacles in observing the main geological elements. The “didactic potential” value was low, with the site possessing some geological elements that may be used in university teaching. The “geological diversity” value was high, with the site possessing more than three types of geodiversity elements.

3.3.3. Potential Touristic Use

Thirteen criteria [5] were applied to assess the PTU (

Table 4. Evaluation of indicators A–M for the assessment of potential touristic use (PTU) (see Figure 6).

Potential Touristic Use (4–3–2–1)	Weight	Score	Weighted Score
A. Vulnerability	10	4	0.4
B. Accessibility	10	1	0.1
C. Use limitations	5	2	0.1
D. Safety	10	2	0.2
E. Logistics	5	4	0.2
F. Density population	5	3	0.15
G. Association with other values	5	4	0.2
H. Scenery	15	3	0.45
I. Uniqueness	10	4	0.4
J. Observation conditions	5	2	0.1
K. Interpretative potential	10	3	0.3
L. Economic level	5	2	0.1
M. Proximity of recreational areas	5	4	0.2

). The selection of the score was performed using the descriptions and corresponding scores reported in the fifth table of Brilha’s work [5].

The first ten criteria (A–J, Table 4) used to assess the PEU and PTU, being the same, were applied once, but we attributed different weights for H-I-J (Table 4). The “interpretative potential” value was medium–high, needing the public to have some geological background knowledge to understand the geological elements present at the site. The “economic level” value was medium–low, being the site located in a municipality with a household income similar to the national average. The “proximity of recreational areas” value was high, being the site located less than 5 km from a recreational area (Marinello–Oliveri beaches) or tourist attractions (cathedral and Greco–Roman colony of Tindari; Figure 10a,c).

3.3.4. Degradation Risk

Five indicators [5] were analyzed to assess the DR (

Table 5. Evaluation of indicators A–E for the assessment of the degradation risk (DR) (see Figure 6).

Degradation Risk (4–3–2–1)	Weight	Score	Weighted Score
A. Deterioration of geological elements	35	4	1.4
B. Proximity to areas/activities with potential to cause degradation	20	4	0.8
C. Legal protection	20	1	0.2
D. Accessibility	15	1	0.15
E. Density of population	10	3	0.3

). The selection of the score was performed using the descriptions and corresponding scores reported in the seventh table of Brilha’s work [5].

The “deterioration of geological elements” value was high, due to the possibility of deterioration of all geological elements present at the site. The “proximity to areas/activities with potential to cause degradation” value was high, being the site located less than 50 m from a potentially degrading area. The rock cliffs facing the reserve are unsuitable for the attendance of stakeholders [47] due to the presence of protruding rock masses that are potentially unstable and liable to future rockfall [49]. Analogously, the absence of adequate and safe access to the Donnavilla Cave, due to the instability of the cliff, makes it unsuitable for visiting. For this reason, safety restrictions are present regarding the accessibility of these unsafe areas, which are unsuitable for the attendance of stakeholders. The “legal protection” value was low, being the site located in an area with legal protection and control of access. The “accessibility” value was low, the site having no direct access by road but located less than 1 km from a road accessible by bus. The “density population” value was high–medium, being the site located in a municipality with 250–1000 inhabitants/km².

4. Discussion

The actual Oliveri–Tindari Lagoon’s shape and position were determined after centuries of coastal dynamics and landscape changes (Figure 8, Figure 10 and Figure 11). The surrounding and submerged sectors of the lagoon, partially observable on satellite imagery, underwent analogous changes in shape (Figure 11). The shape seems compatible with a coastal longshore current and drift, parallel to the Tyrrhenian coast and from west- to eastwards. The petrographic composition of the beach sediments collected along the shoreline was coherent with an eastwards drift. Indeed, the beach sediments showed the occurrence of lithoclasts composed of Alpine anchimetamorphic Verrucano-type deposits (Figure 12o,p), attributed to the Alì–Montagnareale Unit exposed exclusively westwards of the Tindari Cape, at Montagnareale (Lat.: 38°9′25.59″ N; Long.: 14°55′54.57″ E, between 500 and 700 m a.s.l.; Figure 5). This very small-sized outcrop, being the only one on the Tyrrhenian coast of the Peloritani chain, represents a key outcrop for provenance studies. This evidence suggests that the spit was nourished by a sedimentary supply with a western provenance.

4.1. Inventory of the Tindari Cape and Marinello Lakes Interim Geosite (Higher Institute for Environmental Protection and Research Procedure)

On the basis of the ISPRA procedure for the inclusion of a potential geosite in the national inventory [10], the data to report in the inventory of the TCML interim geosite are synthesized in

Table 6. Synthesized information and description of the Tindari Cape and Marinello Lakes (TCML) interim geosite, based on the twenty parameters used in the ISPRA procedure for the inventorying of geosites.

Information	Description
1 Geosite Name	Tindari Cape and Marinello Lakes
2 Dissemination	Yes
3 Compiler	University of Messina. Email address: rsomma@unime.it
4 Type of Data Acquisition	Field survey and literature review
5 Data Acquisition	30 September 2024
6 Location	Tindari Cape (Tindari) and Oliveri (Marinello) (Messina, Italy) Geographic coordinates: 1675650, 4599375 (WGS 84/Pseudo Mercator)
7 Scientific Interest	Lagoon: Primary and preeminent geomorphological scientific interest related to active geomorphosites (with secondary geological/sedimentological value). Lagoonal system with elements of rarity (at regional, national, and international scale), representativeness (the “best” examples of an active geomorphosite at a regional, national, and international scale), and exemplarity (active geomorphosite that can be used to describe its evolution and genetic process). Contextual interest, characterized by secondary-type naturalistic interest, due to significative fauna and vegetation. Tindari Cape: Secondary geomorphological, structural, and palaeontological interest.
8 Degree of Primary Scientific Interest	Global
9 Description	Lagoon: Coastal transitional system with five small-sized brackish ponds and a spit. Tindari Cape: Marble cliffs with a cave (Donnavilla Cave with Quaternary mammal bone continental deposits) and emerged notches and Lithophaga lithophaga holes that underwent uplift.
10 Figures, Tables	Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15, Table 2, Table 3, Table 4, Table 5 and Table 6 in present research
11 Lithology	Lagoon: Sandy, very fine gravels, moderately sorted and with mesokurtic and symmetrical grain size distributions, composed of metamorphic origin lithoclasts (prevailing sericite-bearing phyllites, quartz, feldspars, minor graphite-bearing phyllites, gneiss, marbles, traces of garnet, staurolite, pyroxene; see Figure 12a,n), with a minor contribution of sedimentary origin grains (chert and Verrucano-type metasandstones and metapelite; see Figure 12o,p). Tindari Cape: Two mica marbles (Figure 14) with intercalation of layers of gneiss and micaschist, intruded by aplo-pegmatitic rocks, affected by Variscan metamorphism.
12 Geochronological Unit	Lagoon: Holocene EpochTindari Cape: Paleozoic Era
13 Genetic Process Age	Lagoon: 1880 (or since 1805 according to oral witnesses) Tindari Cape: Mammal vertebrate deposit (Upper Pleistocene), uplift (6.5 and 5 ka cal BP)
14 Type of Interest	Global
15 Exposure	It is due to natural factors (coastal dynamics).
16 Position	Lagoon: It is located on a low-relief coastal plain. Tindari Cape: It is located on a promontory with steep cliffs facing the sea.
17 Accessibility	Lagoon: Access is possible along several dirt paths (no direct access by paved road). Access is interdicted under steep cliffs due to block collapse. Tindari Cape: Access to reach the additional geological elements (cave) is very difficult on foot, lacking any safety measures along the very narrow dirt paths. Direct access to the submerged notch is achieved by swimming, whereas the uplifted notches may be observed by boat.
18 Land Use/Type of Seabed	Protected area (ONR Oliveri–Tindari Lakes)
19 Protected Area	Yes (managing body and public owner: Metropolitan City of Messina)
20 State of Conservation	Site with fragility and vulnerability. Risk of degradation due to natural climate and anthropogenic factors.
21 Protection Proposal	Unnecessary (being ONR)

.

4.2. Quantitative Assessment of the Tindari Cape and Marinello Lakes Interim Geosite (Brilha Method)

The scores from the quantitative assessment of the geodiversity based on the Brilha methodology are reported in

Table 7. Total weights assigned to the four criteria adopted for the quantitative assessment of geodiversity. The total weighted scores of Table 2, Table 3, Table 4 and Table 5 were multiplied by a factor of 100. See Table 1 for the different classes of geodiversity.

Criterion	Total Weighted Score
Scientific Value	320
Potential Education Use	250
Potential Touristic Use	290
Degradation Risk	285

. Based on the high SV (total weight: 320, Table 7), the studied site can be classified as a geosite.

The scores related to the PEU (total weight: 250, Table 7), PTU (total weight: 290, Table 7), and DR (total weight: 285, Table 7), notwithstanding the uniqueness of the landscapes, appeared to indicate that the site is not fully compatible with educational and touristic activities.

4.3. Factors Regarding the Risk of Degradation in the Tindari Cape and Marinello Lakes Interim Geosite

A step that is of paramount importance is the evaluation of the factors influencing the risks of degradation (fragility and vulnerability) in any geoconservation strategy. Indeed, different natural and anthropogenic factors may cause the loss of integrity or scientific value of any geosite, irremediably damaging it [1,79,80]. For this reason, analyzing the risk of degradation should represent a fundamental step in any geoconservation strategy. Geomorphosites may undergo strong modifications, mainly due to intrinsic and extrinsic factors (natural climate and anthropogenic pressures) [79,80]. The main factors influencing a geosite’s vulnerability may be synthesized as follows: (i) anthropogenic stress, (ii) climate change, (iii) unsustainable exploitation, (iv) geohazards, and (v) inadequate management [1,4,60].

The potential vulnerability of the studied Oliveri–Tindari lagoon to natural processes could depend on different factors. The rock collapse, observable at the base of the cliff or in front of the cliff of the Tindari Cape (Figure 8 and Figure 13), could damage the geomorphosite in the near future. The collapsed materials or landslides could form detrital cover on the lagoon, definitively burying this geomorphological geoheritage. Further rock collapse, especially along the internal side of the lagoon, could be triggered by the seismo-tectonic activity related to the Tindari–Novara di Sicilia capable fault system (Figure 13). Global warming could potentially cause the disappearance of many coastal lagoons, as a consequence of the eustatic sea level rise. As the Oliveri–Tindari Lagoon developed on a low-relief coast, it could also be affected by climate changes. On the other hand, if the origin of the Oliveri–Tindari spit was due to an increasing sedimentary supply caused by deforestation activities [43], conversely, irreversible modifications to the scientific value and integrity of this active geomorphosite could occur due to a decreasing sedimentary supply caused by human-induced pressures occurring in the last few decades (such as the noteworthy cementification of the streams and the extraction of alluvial deposits).

5. Concluding Remarks

The spatiotemporal evolution of the coastline in the Oliveri–Tindari system, as it occurred across the time span of 1938–2023, demonstrates active dynamic processes. This evidence makes this system one of best examples of an active geomorphosite (e.g., [65,72]), both on national and international scale. Furthermore, the other highly significant geodiversity elements (such as the uplifted cave with continental fossil remains and the notches along the rock cliffs of the Tindari Cape) add complementary and important value to the interim geosite under study. These results indicate that the site fulfils all requirements to be classified as a global geosite. Consequently, the contents of the present research provide valuable information that could aid the relevant authorities in finally classifying and establishing the geoheritage of the TCML site, which has been pending since 2010, within the Italian National Inventory of Geosites.

Final remarks about future research concern the possibility to model the spit’s evolution, as suggested for other geosites (e.g., [72]). This modelling could be particularly significant for the possible future re-evaluation of the geosite, policy strategies, and initiatives focusing on the sustainable geoconservation of such vulnerable and rare coastal geoheritage.