GEOCHEMICAL AND HYDROGEOLOGICAL STUDY TO IDENTIFY
GEOCHEMICAL AND HYDROGEOLOGICAL STUDY TO IDENTIFY THE SOURCE OF NITRATE IN THE CARBONATE GROUNDWATER (SOUTHERN ITALY) R. COSSU*, L.E. ZUFFIANO’**, P.P. LIMONI**, G. DE GIORGIO**, P. PIZZARDINI*, T. MIANO***, D. MONDELLI***, R. GARAVAGLIA****, C. CARELLA**** AND M. POLEMIO** *Istituto di Ricerca per la Protezione Idrogeologica – CNR, Bari, Italy **Università di Padova ***DiSSPA-Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti –Università degli Studi di Bari Aldo Moro ****Società Progetto Gestione Bari Cinque Srl
SUMMARY: Where the unique natural water resource is groundwater, is the case of wide karstic area, the attention and the susceptibility of local communities and authorities to groundwater risks can be so high to determine relevant misunderstanding due the existence of a number of landfills. For solve this kind of situation, a multi-methodological approach is proposed with the purpose to clarify the role of landfill leakage in terms of groundwater quality degradation risks. The selected study area (SSA) is narrow portion of a wide and deep coastal karstic aquifer, for these characteristics to be considered a case of high complexity and susceptibility. Mainly nitrate and secondly iron groundwater concentration were considered anomalously high in some well of the SSA, not far from Bari (main town of Apulia, a region of Southern Italy), worried about the potential effects of some landfills located in SSA. Five landfills have operated from 1975, one after the other, using increasing safety and technological devices to reduce risks due to leachate leakages with consequent groundwater quality degradation. The multi-methodological approach, which could be potentially applied worldwide, includes: the hydrogeological site characterization; the chemical study and the multi-isotope characterization of groundwater and leachate; the land use analysis and the estimation of nitrogen contributions deriving from agricultural activities, focusing on the use of fertilizers; the mineralogical study of groundwater suspended particles to define the origin of some substances, focusing on iron and manganese, relevant for the SSA. The hydrogeological site characterisation highlighted the local peculiarties of the aquifer. The chemical study was focused on the most important chemical features (Ca2+, Mg2+, Na+, K+, Cl-, SO42-, NO3-), especially to define geochemical peculiarties, along with some minor chemical elements were taken into account, to define globally the groundwater quality and the leachate characteristics. The environmental isotopes of hydrogen (H), carbon (C), nitrogen (N) and oxygen (O) were used to identify the groundwater provenance and the most relevant geochemical reactions. The oxygen-18 (18O) and deuterium (2H) stable isotopes were used to investigate the origin of water Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
in the aquifer system of the study area. The combination of NO3- concentration with δ15N-NO3and 18O-NO3- in groundwater also provides valuable information for identifying the true sources of anthropoghenic NO3-. Groundwater and leachate samples were analysed for 13C and Tritium (3H), completing the framework of knowledge on the role of leachate on groundwater as previous studies have demonstrated that the biogeochemical processes occurring within the landfill environment can produce a unique composition of these isotopes and therefore they can be utilized successfully to delineate the potential leachate influence. The land use analysis highlighted quantity and type of used fertilizers permitting to compare these with groundwater in terms isotopic signature. The mineralogical study demonstred the role of suspend natural parcticle due the presence of terre rosse (red clays) in some groundwater samples. The approach confirmed globally, meaning with all the defined results, which are not quality degradation effects on the sampled groundwater. Keywords: landfill, leachate, pollution, nitrate, nitrogen and oxygen isotopes, karstic coastal aquifer, Italy, Apulia
1. INTRODUCTION In nature, nitrogen is the most abundant component of atmospheric air (about 80%). Nitrogen-containing compounds are found in the organic substance, where nitrogen is present, for example, in the amino acids that make up the proteins. In contrast, minerals containing nitrogen are rare in nature but generally very (Appelo & Postma, 1996). Nitrogen is an important component of natural waters, where it is present dissolved in the form of different species. The concentration of dissolved molecular nitrogen in water, in equilibrium at 25 °C with the atmosphere, is 5x10-4 M (14 mg/L). Nitrogen is found in natural water in different valences such as +5 in NO3-, +3 in NO2-, 0 in N2 and -3 in NH4+ (Appelo & Postma, 1996). The natural groundwater nitrate concentration is generally low, concentrations greater than 1 mg/L are generally due to anthropogenic activities (Dubrovsky et al. 2010). High-nitrate concentrations in groundwater are a worldwide problem (Strebel et al., 1989; Thorburn et al. 2003; Burow et al. 2010; Li et al. 2010; Shalev et al., 2015; Lasagna et al. 2016; Re et al., 2017). Ingestion of high nitrate rate can cause many problems to humans. It is especially dangerous for infants, whose exposure to high nitrate concentration may cause the methemoglobinemia, also commonly known as the “blue baby syndrome” or cyanosis, a potentially fatal outcome (Comly, 1945). Reports of health problems associated with nitrate contaminated groundwater appeared near the end of World War II when the Michigan Department of Health received several requests for nitrate determinations on well-water samples submitted by doctors who were trying to find the cause of methemoglobinemia. The World Health Organization (WHO) states that the NO3- concentration for drinking water should be less than 50 mg/L (WHO 2011). Potential sources of nitrate for groundwater include mineral fertilizers, septic waste, animal manure and landfill leachate. The use of fertilizers and the irrigation allow increasing production and diversification crops. As all crops aren’t able to use all the added mineral fertilizer, the use of nitrogenous fertilizer creates risk of increasing percolation and leaching of nitrates to groundwater, which are very relevant in the case, almost frequent, of over fertilisation (Singh et al., 1995). Many studies have indicated a high correlation between agriculture and nitrate concentrations in groundwater (Heaton et al., 2012; Re et al., 2017; Sheikhy Narany at al., 2017).
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
The landfill leachate could be another potential source of groundwater nitrogenous solutes, including nitrate. Municipal or urban landfill leachate consist generally of many different organic and inorganic compounds that are either dissolved or suspended in the wastewater (Mendoza et al., 2017). According to Mor et al. (2006), areas close to landfills have a greater possibility of groundwater contamination because of the potential pollution source of leachate which also contain heavy metals such as cadmium, chromium, iron, lead, zinc, nickel (Mendoza et al., 2017). The aim of this paper is to define and apply a multi-methodological approach to characterize the groundwater close to urban solid waste landfills located in a selected study area (SSA), choiced considering the precence of intensive agriculture and the location on a karstic coastal aquifer with the purpose to testify the existence or excluding leachate effects on groundwater. The SSA is narrow portion of a wide and deep coastal karstic aquifer, for these characteristics to be considered a case of high complexity and susceptibility. Five landfills have operated from 1975, one after the other, using increasing safety and technological devices to reduce risks due to leachate leakages with consequent groundwater quality degradation. Mainly nitrate and secondly iron groundwater concentration were considered anomalously high in some well of the SSA, not far from Bari (main town of Apulia, a region of Southern Italy), worried about the potential effects of some landfills located in SSA. For this reason, some landfills were seized by public authorities, hypothising a role of these in the groundwater quality degradation. The approach considers each potential source of nitrate, considering the type of local land use: mineral fertilizers, septic waste, animal manure and landfill leachate. The approach includes the use of nitrogen, oxygen and tritium isotopes as tracers for evaluating contamination of the landfill. The isotope approach regarding δ15N is based on the distinct isotopic composition that characterizes nitrate of different origin (Aravena et al., 1993). For the commercial fertilizers, typical δ15N values range from -2‰ to +4‰, for soil organic nitrogen nitrate the values range from +3‰ to +8‰ and + 10‰ to +20‰ for human and animal waste nitrate (Freyer and Aly, 1974; Kreitler, 1975; Gormly and Spalding, 1979; Heaton, 1986). In the case of 18O, synthetic fertilizers are characterized by enriched 18O values (+ 18‰ to +22‰), since the source of oxygen for these chemicals is atmospheric oxygen whose value is 18O=+ 23.5‰ (Amberger and Schmidt, 1987). Tritium (3H) is a radioactive isotope of hydrogen, occurring in very low quantity in the natural waters (Tazioli, 2011). Tritium (3H) levels in municipal solid waste landfill leachate can be several orders of magnitude greater than background groundwater levels due to the presence in the waste of some items containing high levels of tritium such as luminescence paints, watches (Robinson and Goronow, 1995, Hackley et al., 1996; Tazioli, 2011). High concentration of tritium in the leachate occur in municipal landfills throughout the world (Fritz et al., 1994; Robinson and Gronow, 1996; Fuganti et al., 2003; Tazioli et al., 2004; Hughes et al., 2011; Raco et al., 2013). Because of this, tritium may be a sensitive indicator of leachate impacts on groundwater samples (Kerfoot et al. 2003). Other isotope used for prevention and control of groundwater pollution is the δ13C of total dissolved carbon (Tazioli & Tazioli, 2005). The isotopic composition of dissolved inorganic carbon compounds in groundwater has a wide range of δ13C values. Dissolved carbonates, bicarbonates and CO2 usually have a value of about -15‰ and -10‰ referred to the standard PDB (belamnite carbonate from the Pee Dee formation of South Caroline), while for surface waters δ13C values are less high. For the atmospheric CO2, δ13C is about -8‰; in soil-gas CO2, δ13C has values ranging from -25‰ to -15‰. Most marine carbonates rocks have δ13C ranging from -2 to 0‰ (Letolle and Olive, 1983). Under reduction conditions (similar to those present in landfill environments), δ13C is highly enriched (δ13C > +15‰) (Tazioli & Tazioli, 2005). The positive value of δ13C is due to the production of methane under anaerobic conditions (Wimmer
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
et al., 2013). 2. SELECTED STUDY AREA The SSA is located in the municipality of Conversano, close to Bari, the main town in the Apulia region. The SSA elevation from 100 to 175 m above mean sea level, with a mean land surface slope of 1.3% from west to east (seaward). The SSA is a rural area. Agriculture is the main activity, namely due to olive groves, cherry trees, almond trees and large extensions of vineyards. The study area includes 5 solid urban waste landfills, distinguished from I to V in chronological order of realisation, which are located roughly at 5 km northwest from the town of Conversano (Figures 1b and 1c). The more recent landfills II-V were built with a low permeability bottom, a clayey layer, to contain leachate that is collected, tapped and treated (II, IV and V). Contrarily, the oldest landfill (I) do not have any waterproofing liners at the bottom; after closure, the landfill I was not sealed by impervious capping to prevent rainwater infiltration, nor precautions were taken to collect leachate, limiting the leakage toward groundwater. Landfill I collected wastes from 1975 to 1982, for about a year in 1989 and for about 100 days in 1996, less than 10 years as total. This landfill was not sealed by capping. The leachate tapping system was not realized. The Landfill II operated from 1993 and was closed in 1996; the landfill post-mortem was terminated. It was equipped with a definitive capping realized with HDPE geomembrane and other typical urban waste tools, to nullify leachate leakage risks. The landfill II top now hosts a photovoltaic system. The leachate tapping system is now completely unseful and unusable. Roughly 1,465,000 m3 of wastes were disposed from 1996 to 2011 in the landfill III. At the present, the top of the III has been realised by a capping of HDPE geomembrane. The Progetto Ambiente Bacino BA/5 landfill system is made up of two sectors or tanks, our landfills IV and V (Figure 1c). Roughly 200,000 m3 of waste were disposed from March 2011 to April 2013, temporally covered by soil layer, in landfill IV while the V was realised but is still unused. Landfills III, IV and V were sized by authorities. Merging all boundary conditions, it was possible to sample only the leachate of landfill IV. 3. GEOLOGICAL AND HYDROGEOLOGICAL SETTINGS The Murge Plateau, which represents the central part of the Apulian carbonate platform, is made up of a Cretaceous carbonate succession in which the Bari limestone Formation (Valanginian-Early Turonian) and the Altamura limestone Formation (Coniacian-Early Campanian) can be distinguished (Laviano and Marino, 1996; Spalluto, 2012). An unconformity marked by a bauxite horizon and red soil or terra rossa deposits separates the two Cretaceous formations (Ciaranfi et al., 1979; Borgomano, 2000); the latter, roughly 1 km-thick, outcrops in the SSA (Figure 1b). The terra rossa is produced by the limestone weathering: when limestone weathers, mainly for dissolution, the clay contained in the rocks is left behind, along with any other non-soluble rock material. The terra rossa is a residual soil which outcrops as a mantle over limestone bedrock, typically in the karstic Mediterranean areas (Bates and Jackson 1987). The main minerals of terra rossa are illite, kaolinite, and oxides and hydroxides of iron; minor components are quartz, feldspars, micas, oxides and hydroxides of aluminum, and oxides of titanium (Moresi and Mongelli, 1988). The Murgia Plateau emerged since Late Cretaceous until Pliocene (Pieri et al., 1997), creating a major unconformity covered by thin (
SUMMARY: Where the unique natural water resource is groundwater, is the case of wide karstic area, the attention and the susceptibility of local communities and authorities to groundwater risks can be so high to determine relevant misunderstanding due the existence of a number of landfills. For solve this kind of situation, a multi-methodological approach is proposed with the purpose to clarify the role of landfill leakage in terms of groundwater quality degradation risks. The selected study area (SSA) is narrow portion of a wide and deep coastal karstic aquifer, for these characteristics to be considered a case of high complexity and susceptibility. Mainly nitrate and secondly iron groundwater concentration were considered anomalously high in some well of the SSA, not far from Bari (main town of Apulia, a region of Southern Italy), worried about the potential effects of some landfills located in SSA. Five landfills have operated from 1975, one after the other, using increasing safety and technological devices to reduce risks due to leachate leakages with consequent groundwater quality degradation. The multi-methodological approach, which could be potentially applied worldwide, includes: the hydrogeological site characterization; the chemical study and the multi-isotope characterization of groundwater and leachate; the land use analysis and the estimation of nitrogen contributions deriving from agricultural activities, focusing on the use of fertilizers; the mineralogical study of groundwater suspended particles to define the origin of some substances, focusing on iron and manganese, relevant for the SSA. The hydrogeological site characterisation highlighted the local peculiarties of the aquifer. The chemical study was focused on the most important chemical features (Ca2+, Mg2+, Na+, K+, Cl-, SO42-, NO3-), especially to define geochemical peculiarties, along with some minor chemical elements were taken into account, to define globally the groundwater quality and the leachate characteristics. The environmental isotopes of hydrogen (H), carbon (C), nitrogen (N) and oxygen (O) were used to identify the groundwater provenance and the most relevant geochemical reactions. The oxygen-18 (18O) and deuterium (2H) stable isotopes were used to investigate the origin of water Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
in the aquifer system of the study area. The combination of NO3- concentration with δ15N-NO3and 18O-NO3- in groundwater also provides valuable information for identifying the true sources of anthropoghenic NO3-. Groundwater and leachate samples were analysed for 13C and Tritium (3H), completing the framework of knowledge on the role of leachate on groundwater as previous studies have demonstrated that the biogeochemical processes occurring within the landfill environment can produce a unique composition of these isotopes and therefore they can be utilized successfully to delineate the potential leachate influence. The land use analysis highlighted quantity and type of used fertilizers permitting to compare these with groundwater in terms isotopic signature. The mineralogical study demonstred the role of suspend natural parcticle due the presence of terre rosse (red clays) in some groundwater samples. The approach confirmed globally, meaning with all the defined results, which are not quality degradation effects on the sampled groundwater. Keywords: landfill, leachate, pollution, nitrate, nitrogen and oxygen isotopes, karstic coastal aquifer, Italy, Apulia
1. INTRODUCTION In nature, nitrogen is the most abundant component of atmospheric air (about 80%). Nitrogen-containing compounds are found in the organic substance, where nitrogen is present, for example, in the amino acids that make up the proteins. In contrast, minerals containing nitrogen are rare in nature but generally very (Appelo & Postma, 1996). Nitrogen is an important component of natural waters, where it is present dissolved in the form of different species. The concentration of dissolved molecular nitrogen in water, in equilibrium at 25 °C with the atmosphere, is 5x10-4 M (14 mg/L). Nitrogen is found in natural water in different valences such as +5 in NO3-, +3 in NO2-, 0 in N2 and -3 in NH4+ (Appelo & Postma, 1996). The natural groundwater nitrate concentration is generally low, concentrations greater than 1 mg/L are generally due to anthropogenic activities (Dubrovsky et al. 2010). High-nitrate concentrations in groundwater are a worldwide problem (Strebel et al., 1989; Thorburn et al. 2003; Burow et al. 2010; Li et al. 2010; Shalev et al., 2015; Lasagna et al. 2016; Re et al., 2017). Ingestion of high nitrate rate can cause many problems to humans. It is especially dangerous for infants, whose exposure to high nitrate concentration may cause the methemoglobinemia, also commonly known as the “blue baby syndrome” or cyanosis, a potentially fatal outcome (Comly, 1945). Reports of health problems associated with nitrate contaminated groundwater appeared near the end of World War II when the Michigan Department of Health received several requests for nitrate determinations on well-water samples submitted by doctors who were trying to find the cause of methemoglobinemia. The World Health Organization (WHO) states that the NO3- concentration for drinking water should be less than 50 mg/L (WHO 2011). Potential sources of nitrate for groundwater include mineral fertilizers, septic waste, animal manure and landfill leachate. The use of fertilizers and the irrigation allow increasing production and diversification crops. As all crops aren’t able to use all the added mineral fertilizer, the use of nitrogenous fertilizer creates risk of increasing percolation and leaching of nitrates to groundwater, which are very relevant in the case, almost frequent, of over fertilisation (Singh et al., 1995). Many studies have indicated a high correlation between agriculture and nitrate concentrations in groundwater (Heaton et al., 2012; Re et al., 2017; Sheikhy Narany at al., 2017).
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
The landfill leachate could be another potential source of groundwater nitrogenous solutes, including nitrate. Municipal or urban landfill leachate consist generally of many different organic and inorganic compounds that are either dissolved or suspended in the wastewater (Mendoza et al., 2017). According to Mor et al. (2006), areas close to landfills have a greater possibility of groundwater contamination because of the potential pollution source of leachate which also contain heavy metals such as cadmium, chromium, iron, lead, zinc, nickel (Mendoza et al., 2017). The aim of this paper is to define and apply a multi-methodological approach to characterize the groundwater close to urban solid waste landfills located in a selected study area (SSA), choiced considering the precence of intensive agriculture and the location on a karstic coastal aquifer with the purpose to testify the existence or excluding leachate effects on groundwater. The SSA is narrow portion of a wide and deep coastal karstic aquifer, for these characteristics to be considered a case of high complexity and susceptibility. Five landfills have operated from 1975, one after the other, using increasing safety and technological devices to reduce risks due to leachate leakages with consequent groundwater quality degradation. Mainly nitrate and secondly iron groundwater concentration were considered anomalously high in some well of the SSA, not far from Bari (main town of Apulia, a region of Southern Italy), worried about the potential effects of some landfills located in SSA. For this reason, some landfills were seized by public authorities, hypothising a role of these in the groundwater quality degradation. The approach considers each potential source of nitrate, considering the type of local land use: mineral fertilizers, septic waste, animal manure and landfill leachate. The approach includes the use of nitrogen, oxygen and tritium isotopes as tracers for evaluating contamination of the landfill. The isotope approach regarding δ15N is based on the distinct isotopic composition that characterizes nitrate of different origin (Aravena et al., 1993). For the commercial fertilizers, typical δ15N values range from -2‰ to +4‰, for soil organic nitrogen nitrate the values range from +3‰ to +8‰ and + 10‰ to +20‰ for human and animal waste nitrate (Freyer and Aly, 1974; Kreitler, 1975; Gormly and Spalding, 1979; Heaton, 1986). In the case of 18O, synthetic fertilizers are characterized by enriched 18O values (+ 18‰ to +22‰), since the source of oxygen for these chemicals is atmospheric oxygen whose value is 18O=+ 23.5‰ (Amberger and Schmidt, 1987). Tritium (3H) is a radioactive isotope of hydrogen, occurring in very low quantity in the natural waters (Tazioli, 2011). Tritium (3H) levels in municipal solid waste landfill leachate can be several orders of magnitude greater than background groundwater levels due to the presence in the waste of some items containing high levels of tritium such as luminescence paints, watches (Robinson and Goronow, 1995, Hackley et al., 1996; Tazioli, 2011). High concentration of tritium in the leachate occur in municipal landfills throughout the world (Fritz et al., 1994; Robinson and Gronow, 1996; Fuganti et al., 2003; Tazioli et al., 2004; Hughes et al., 2011; Raco et al., 2013). Because of this, tritium may be a sensitive indicator of leachate impacts on groundwater samples (Kerfoot et al. 2003). Other isotope used for prevention and control of groundwater pollution is the δ13C of total dissolved carbon (Tazioli & Tazioli, 2005). The isotopic composition of dissolved inorganic carbon compounds in groundwater has a wide range of δ13C values. Dissolved carbonates, bicarbonates and CO2 usually have a value of about -15‰ and -10‰ referred to the standard PDB (belamnite carbonate from the Pee Dee formation of South Caroline), while for surface waters δ13C values are less high. For the atmospheric CO2, δ13C is about -8‰; in soil-gas CO2, δ13C has values ranging from -25‰ to -15‰. Most marine carbonates rocks have δ13C ranging from -2 to 0‰ (Letolle and Olive, 1983). Under reduction conditions (similar to those present in landfill environments), δ13C is highly enriched (δ13C > +15‰) (Tazioli & Tazioli, 2005). The positive value of δ13C is due to the production of methane under anaerobic conditions (Wimmer
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
et al., 2013). 2. SELECTED STUDY AREA The SSA is located in the municipality of Conversano, close to Bari, the main town in the Apulia region. The SSA elevation from 100 to 175 m above mean sea level, with a mean land surface slope of 1.3% from west to east (seaward). The SSA is a rural area. Agriculture is the main activity, namely due to olive groves, cherry trees, almond trees and large extensions of vineyards. The study area includes 5 solid urban waste landfills, distinguished from I to V in chronological order of realisation, which are located roughly at 5 km northwest from the town of Conversano (Figures 1b and 1c). The more recent landfills II-V were built with a low permeability bottom, a clayey layer, to contain leachate that is collected, tapped and treated (II, IV and V). Contrarily, the oldest landfill (I) do not have any waterproofing liners at the bottom; after closure, the landfill I was not sealed by impervious capping to prevent rainwater infiltration, nor precautions were taken to collect leachate, limiting the leakage toward groundwater. Landfill I collected wastes from 1975 to 1982, for about a year in 1989 and for about 100 days in 1996, less than 10 years as total. This landfill was not sealed by capping. The leachate tapping system was not realized. The Landfill II operated from 1993 and was closed in 1996; the landfill post-mortem was terminated. It was equipped with a definitive capping realized with HDPE geomembrane and other typical urban waste tools, to nullify leachate leakage risks. The landfill II top now hosts a photovoltaic system. The leachate tapping system is now completely unseful and unusable. Roughly 1,465,000 m3 of wastes were disposed from 1996 to 2011 in the landfill III. At the present, the top of the III has been realised by a capping of HDPE geomembrane. The Progetto Ambiente Bacino BA/5 landfill system is made up of two sectors or tanks, our landfills IV and V (Figure 1c). Roughly 200,000 m3 of waste were disposed from March 2011 to April 2013, temporally covered by soil layer, in landfill IV while the V was realised but is still unused. Landfills III, IV and V were sized by authorities. Merging all boundary conditions, it was possible to sample only the leachate of landfill IV. 3. GEOLOGICAL AND HYDROGEOLOGICAL SETTINGS The Murge Plateau, which represents the central part of the Apulian carbonate platform, is made up of a Cretaceous carbonate succession in which the Bari limestone Formation (Valanginian-Early Turonian) and the Altamura limestone Formation (Coniacian-Early Campanian) can be distinguished (Laviano and Marino, 1996; Spalluto, 2012). An unconformity marked by a bauxite horizon and red soil or terra rossa deposits separates the two Cretaceous formations (Ciaranfi et al., 1979; Borgomano, 2000); the latter, roughly 1 km-thick, outcrops in the SSA (Figure 1b). The terra rossa is produced by the limestone weathering: when limestone weathers, mainly for dissolution, the clay contained in the rocks is left behind, along with any other non-soluble rock material. The terra rossa is a residual soil which outcrops as a mantle over limestone bedrock, typically in the karstic Mediterranean areas (Bates and Jackson 1987). The main minerals of terra rossa are illite, kaolinite, and oxides and hydroxides of iron; minor components are quartz, feldspars, micas, oxides and hydroxides of aluminum, and oxides of titanium (Moresi and Mongelli, 1988). The Murgia Plateau emerged since Late Cretaceous until Pliocene (Pieri et al., 1997), creating a major unconformity covered by thin (
