Short-Term Climate Oscillations During the Messinian Salinity Crisis: New Insights from Gypsum Lithofacies of the Crati Basin (Lattarico, Calabria, Southern Italy)

Abstract

This study presents the first detailed investigation of the petrography, mineralogy, and depositional environment of Messinian gypsum lithofacies outcropping on the western side of the Crati Basin (Calabria, Southern Italy), focusing on three sections: Castelluccio, Striscioli, and Piretto. The different localities preserve in situ gypsum accumulation (laminar gypsum and gypsiferous mudstone) and clastic gypsum deposits (nodular, gypsarenite and gypsrudite) formed during the second stage (5.60–5.55 Ma) of the Messinian Salinity Crisis (MSC). Observation and analyses of macro-, meso- and nanoscale reveal a complex climatic variability and depositional history that reflect different environmental conditions, from shallow-water evaporitic environments to deep basin settings affected by slope failures. The data highlights the influence of tectonic activity on facies distribution within the basin. Overall, this study emphasizes the importance of climatic and geological controls on gypsum deposition, offering a detailed interpretation of the Crati Basin’s evaporitic history and contributing to the broader understanding of Mediterranean Messinian evaporites.

1. Introduction

Gypsum (CaSO₄·2H₂O) is one of the most significant minerals within the evaporitic successions formed during the Messinian Salinity Crisis (MSC). This event, dated between 5.97 Ma and 5.33 Ma, was characterized by the progressive isolation of the Mediterranean Basin from the Atlantic Ocean [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. The resulting extreme evaporation of marine waters led to the deposition of substantial amounts of evaporitic minerals, including gypsum [2]. Primary gypsum, classified as Lower Gypsum and Upper Gypsum, was deposited during Stages 1 and 3 of the MSC, respectively. These deposits encompass a variety of gypsum lithofacies, whose characteristics were influenced by depositional environments, ranging from shallow to deep-water conditions, as well as orbitally driven climatic oscillations [16,17,18,19,20,21]. During Stage 2, detrital gypsum, known as the Resedimented Lower Gypsum unit, was formed in several Mediterranean areas (i.e., Cyprus [22] and references therein; Italy [23,24,25,26,27,28] and references therein; and Spain [9]). This unit originated from the erosion and redeposition of primary gypsum, resulting in extensive reworking and transport processes [9,24,25].

The origin of gypsum (primary or secondary) and its deposition (as an in situ or clastic deposit) have been extensively studied, as they provide critical insights into the climatic and environmental changes occurring during the Messinian age. Beyond its paleoenvironmental significance, gypsum serves as a valuable resource for investigations into the stratigraphy, sedimentology and diagenesis of evaporitic deposits, which can affect the quality of the local water resource [29,30].

In general, primary gypsum precipitates as bedded deposits with different textures that provide important information about the timing and conditions of its formation, reflecting parameters such as brine depth and stability during precipitation. The main morphology includes prismatic, lenticular, and growth-aligned gypsum [17]. The first change in the texture of primary gypsum can already occur within the early eogenetic realm of the burial cycle, but it is primarily during burial (into the mesogenetic realm) that gypsum can be replaced by anhydrite, which exhibits several morphologies. During telogenetic rehydration, secondary gypsum commonly forms when previously impervious mesogenetic nodular anhydrite layers are exposed to regions with increasing phreatic activity, undersaturation, and meteoric crossflow, eventually transitioning into the vadose zone. In this latter contest, three secondary gypsum fabrics, characteristic of rehydration and replacement, can be formed as follows: (i) coarse porphyroblastic gypsum; (ii) fine-grained alabastrine gypsum; and (iii) satin-spar gypsum [31,32,33,34,35,36,37,38,39,40]. The gypsum-anhydrite-gypsum transition across the three realms is known as the paragenetic sequence of sulfate [41].

This study aims to investigate, for the first time, the gypsum lithofacies recognized in the Crati Basin (Calabria region) in order to describe the origin of gypsum (primary or secondary), its deposition (as in situ or clastic deposit), and to reconstruct the paleoenvironmental conditions that led to gypsum formation.

By accomplishing these purposes, the findings aim to provide new insights into the depositional and diagenetic processes of gypsum, as well as its broader geological significance, contributing to the larger puzzle of reconstructing the Messinian Salinity Crisis.

2. Geological Setting

The study area (Figure 1) is located within a region affected by an extensional tectonic regime [42] characterized by a system of normal faults that has generated a series of extensional basins crossing northern Calabria from the Pollino Massif [43] to the southern part of the Crati River [44]. Among these, the Crati Basin is one of the largest in terms of areal extent; it is oriented north–south and displays a maximum extension in the east–west direction. This basin is bounded and controlled by an array of east- and west-dipping normal faults that accommodate the regional extension in this sector of northern Calabria [45]. The extensional tectonic phase, dated to the Pliocene–Holocene [46], cuts through pre-existing Paleozoic–Mesozoic tectonostratigraphic units. These include a non-metamorphosed carbonate Apenninic Unit (Pollino Unit) and a metamorphosed equivalent (Verbicaro Unit), both overlain by Ligurian Units and by the Sila Units, which are the uppermost tectonostratigraphic unit superimposed on the previous one [47,48,49].

The stratigraphic succession of the CB was divided, from the bottom to the top, into the following four sedimentary units [50,51,52,53]:

(a)

The upper Miocene Basal Succession (BaS) outcrops discontinuously along the western side of the CB, unconformably overlying the crystalline Paleozoic rocks. From the base upwards, the BaS comprises conglomerates, sands, and arenites grading into clays and silty clays. The top of this interval consists of an evaporitic succession of Messinian age (i.e., limestone and gypsum) [54];

(b)

The Pliocene succession (PS) crops out extensively along the western side of the basin. This interval shows continental conglomerates that grade into marine silty clays [54];

(c)

The Pliocene–Pleistocene succession (PPS) occurs along the eastern border of the basin. It is characterized by shallow-water marine calcarenites and conglomerates, evolving to marine sands. In the center of the basin, these deposits change into upper Pliocene-early Pleistocene marine clays [54];

(d)

The Pleistocene Gilbert-type (PIS) fan delta conglomerates crop out extensively along the western and central parts of the basin [52,55,56].

Each unit is bound by angular unconformities, characterized by erosional surfaces and/or depositional hiatuses related to tectonic activity.

The extensive Miocene rocks outcropping in the Lattarico area almost entirely belong to the Messinian age [57]. These consist, from the bottom to the top, of para-conglomerate with a sandy-clay matrix that contains predominantly gneissic and granitic elements ranging in shape from elongated to subspherical and from angular to subrounded. The para-conglomerate evolves through an evaporitic phase (represented by evaporitic limestone) from continental to paralic conditions [57]. The evaporitic limestone exhibits a vacuolar brecciated texture, with micritic elements containing traces of structures similar to those found in the Calcare di Base of the gypsum sulfur series of Sicily [58]. Subsequently, a sequence of marls, marly calcareous siltstone and gypsum follows, representing the most distinctly marine part of the succession trending toward evaporitic conditions. In particular, this unit consists of densely bedded marls that, towards the gypsum and the top, exhibit a heteropic transition to marly calcareous siltstones characterized by rather dense bedding and thin arenaceous intercalations. The gypsum, often marked by intercalations of marly layers similar to the partings of the gypsum sulfur series of Sicily, displays a lenticular pattern that is more evident where the Messinian succession is well developed. Marls, marly calcareous siltstone, and gypsum are unconformably overlain by an arkose of deltaic environment, which forms the infill of the Lattarico sub-basin.

These rocks are largely not fossiliferous, except for a few thin levels in the marls and marly calcareous siltstones; a sample collected from one of these levels yielded a microfauna rather rich in individuals but poor in species. Comparing this association with the one described by Colalongo [59] for the neo-stratotype of the Messinian [60,61], it can be assigned to the Orbulina suturalis-Globigerinoides obliquus extremus subzone of the neo-stratotype, which is Lower Messinian in age [57].

Around the town of Lattarico, gypsum deposits were recognized in three sections: Castelluccio (Section 1), Striscioli (Section 2) and Piretto (Section 3).

Figure 1. Geological map of the study areas (modified from “Sheet F229 III NE” Lattarico in scale 1:25,000, of the Carta Geologica della Calabria IGM [62]. Numbers 1, 2 and 3 represent the Castelluccio, Striscioli and Piretto sections, respectively.

Figure 1. Geological map of the study areas (modified from “Sheet F229 III NE” Lattarico in scale 1:25,000, of the Carta Geologica della Calabria IGM [62]. Numbers 1, 2 and 3 represent the Castelluccio, Striscioli and Piretto sections, respectively.

3. Sampling and Analytical Methods

Field observations and sampling were conducted in the Castelluccio, Striscioli and Piretto sections (Crati Basin, Calabria Region, Southern Italy), where the gypsum deposits are well preserved.

The sampling was preceded by a stratigraphic description of the different outcrops and a macroscopic facies analysis to characterize the lithofacies comprising the three deposits. A total of twenty-four samples from different gypsum lithofacies were collected for petrographic studies. Thin sections (~30 μm thick) were prepared and observed using an optical microscope (Zeiss Axioplan 2 Imaging) to distinguish the lithofacies. The presence and distribution of organic matter were evaluated using UV epifluorescence, employing a mercury high-pressure vapor bulb and high-performance wide bandpass filters (436/10 nm) and long pass (470 nm), No. 488006, for the green light, as well as bandpass filters (450–490 nm) and long pass (515 nm), No. 488009, for the yellow light [63,64,65]. Representative thin sections were carbon-coated for Scanning Electron Microscopy (SEM) observations and energy-dispersive X-ray spectroscopy (EDS) microanalysis. The SEM apparatus used was an ultra-high resolution (UHRSEM)–ZEISS Crossbeam 350, operating under the following conditions: resolution (123 eV), high voltage (10 keV), probe current (100 pA) and working distance (11 mm). Mineralogical and chemical compositions were analyzed using an EDAX Octane Elite Plus with a silicon drift detector (Si₃N₄ window). The apparatus was operated under high voltage (15 keV), probe current (10 nA), working distance (12 mm), take-off angle (40°), and live time (30 s). Standardless quantitative analysis was verified using the SPI No. The 02757-AB serial 4AK standard and data were collected through the AMETEK APEX software suite V2.

All samples were analyzed at the Laboratories of Thin Section, Center SILA infrastructure, Geobiology and the Electron Microscopy of the Department of Biology, Ecology and Earth Science, University of Calabria (Rende, Italy).

4. Results

4.1. Field Observations

The Castelluccio section (39.456188° N; 16.144028° E) exhibits a deposit (~42 m) consisting of laminar gypsum (Lithofacies A), nodular-laminated gypsum with chicken-wire fabric (Lithofacies B₁), massive gypsum with terrigenous components (Lithofacies C), nodular-laminated gypsum with enterolithic crenulation fabric (Lithofacies B₂), massive gypsum (Lithofacies C) and gypsrudite (Lithofacies D), (

Table 1. Samples list for Sections 1, 2 and 3 and relative lithofacies (n.p. = not present).

Sampling Sections	Lithofacies
	Laminar Gypsum (Lith. A)	Nodular-Laminated Gypsum (Lith. B1 and B2)	Massive Gypsum (Lith. C)	Gypsrudite (Lith. D)	Gypsiferous (Lith. E)
Castelluccio (1)	C-01, C-02, C-03	C-04 to C-08	C-09, C-10	C-11, C-12	n.p.
Striscioli (2)	S-01 to S-04	n.p.	S-05	n.p.	n.p.
Piretto (3)	P-01, P-02	P-03, P-04	P-05	n.p.	P-06

).

Lithofacies A (Figure 2A) consists of sub-parallel alternations of white (~2 mm thick) and brown (<1 mm thick) laminae. Three samples (C-01, C-02 and C-03) were collected from this lithofacies.

Lithofacies B shows an alternation of dark gypsum laminae and layers of isolated or coalescent whitish nodules (up to 2 cm). Individual scattered white nodules, as well as aggregated or packed nodules and nodular layers, have been recognized. Based on the size and orientation of nodules and laminae, this lithofacies displays two fabrics (Figure 2B,C): chicken-wire (Lithofacies B₁) and enterolithic crenulation (Lithofacies B₂). Three samples from Lithofacies B₁ (C-04, C-05 and C-06) and two from Lithofacies B₂ (C-07 and C-08) were collected.

Lithofacies C consists of massive gypsum (Figure 2D), lacking lamination and containing embedded terrigenous minerals (<1 mm in size). At the outcrop scale, Lithofacies A and C laterally extend for tens of meters. No sedimentary structures (e.g., cross-lamination) indicative of tractive bottom currents or oscillatory flows were observed in either lithofacies. Two samples (C-09 and C-10) were collected from two strata belonging to Lithofacies C.

Lithofacies D (Figure 2D,E), recognized only in the Castelluccio section, consists of gypsrudite (clastic gypsum) showing abundant deformation (i.e., slump; Figure 2E) and incorporates, within a fine-grained matrix, large fragments of laminar gypsum (Figure 2E,F) and rounded or irregular clasts (>10 cm in size), chaotically arranged. At the macroscale, these clasts are composed of nodular and massive gypsum. From this lithofacies were collected two samples (C-11 and C-12).

The Striscioli section (39.442483° N; 16.146780° E) exposes a stratified gypsum deposit (~5.20 m), mainly composed of laminar gypsum (Lithofacies A). In the middle of the sequence, a thin layer (20 cm) of massive gypsum (Lithofacies C) was also identified (Table 1).

Lithofacies A is characterized by millimeter-scale laminated layers displaying white and gray colors. The lamination is predominantly parallel, though occasional undulating features are present, indicating notable lateral continuity and a combination of planar and wavy parallel lamination. The individual white layers can exceed 20 cm in thickness, and they are composed of fine- to very fine-grained crystals. The gray layers are generally thinner than the white ones, and in the basal portion, they appear darker compared to the upper portion. Four samples (S-01, S-02, S-03, and S-04) were collected from this lithofacies (Figure 3A,B).

Lithofacies C consists of massive gypsum, lacking any laminated structure. The matrix is homogeneous, with dispersed terrigenous minerals, typically less than 1 mm in size, scattered throughout the gypsum. One sample (S-05) was collected from this lithofacies (Figure 3B).

The Piretto section (39.448919° N; 16.131530° E) exposes a gypsum deposit (~6.5 m thick) composed of four main lithofacies (Figure 4): laminar gypsum (Lithofacies A), nodular-laminated gypsum (Lithofacies B₁), massive gypsum (Lithofacies C), and gypsiferous mudstone (Lithofacies E) (Table 1). This last facies was found exclusively in this section and is not present in the Striscioli and Castelluccio outcrops.

Two strata belonging to the Lithofacies A were identified at the bottom and in the middle part of the Piretto outcrop. Both strata (Figure 4B,C) display sub-parallel laminations (often exceeding 2 cm in thickness) with alternating white and dark/light brown color. The stratum observed in the middle part shows a light enterolithic fold. Two samples were collected from the laminar gypsum (P-01 and P-02).

Lithofacies B (Figure 4B) is characterized by an alternation of dark gypsum laminae and layers containing isolated or coalescent whitish nodules. The laminated nodules show chicken-wire structure (B₁). The basal strata exhibit more rounded and well-defined nodules, while the upper portion is characterized by elongated nodules and more linear layers. Two samples (P-03 and P-04) were collected from the laminated-nodules gypsum.

Lithofacies C (Figure 4A) consists of fine gypsum crystals with embedded terrigenous sediments (<1 mm), and it is very similar to those observed in Section 1 (Castelluccio). One sample (P-05) was collected from this facies.

A single stratum of massive gypsiferous (Figure 4A) with clearly thin dark laminae (<1 mm), belonging to the Litofacies E, is recognized in the upper part of the Piretto deposit. This facies was idendified only in this section, and one sample (P-06) was collected.

4.2. Microscopic Observations

4.2.1. Lithofacies A–Laminar gypsum

Microscopically, laminar gypsum consists of alternating white and light/dark brown laminae, which exhibit distinct texture and composition (Figure 5A and Figure 6A). The white laminae, conventionally known as gypsum-rich laminae [66,67], are homogeneous and compact, primarily composed of gypsum and, in minor amounts aluminosilicate (<1 wt%). In contrast, the brown laminae, generally interpreted as clay-rich laminae [66], display porous and granular textures and, in addition to gypsum, have high amounts of aluminosilicate compared to the white laminae.

Petrographically (

Table 2. Summary of the gypsum textures recognized in the five gypsum lithofacies (n.p. = not present). NB: the order of lithofacies listed in the table reflects their alphabetical labels (A–E) and does not represent a depositional or stratigraphic sequence.

Lithofacies	Gypsum Textures
	Primary	Secondary
Lithofacies A (laminar gypsum)	Microcrystalline	Acicular-like Coarsely crystalline anhedral Fibrous Alabastrine
Lithofacies B (Nodular-laminated gypsum)	n.p.	Fibrous Porphyroblastic Rosette gypsum
Lithofacies C (gypsarenite)	Microcrystalline (relicts)	Fibrous Alabastrine
Lithofacies D (gypsarudite)	Microcrystalline (relicts)	Coarsely crystalline anhedral Porphyroblastic Alabastrine Prismatic-radial gypsum
Lithofacies E (gypsiferous)	Microcrystalline	Alabastrine Porphyroblastic Fibrous

), the gypsum-rich laminae are mainly composed of gypsum of primary origin (chemical precipitation), though secondary gypsum, formed through diagenetic transformation of anhydrite, is also present. Primary gypsum exhibits microcrystalline textures, characterized by crystal sizes ranging from 5 to 100 μm. These crystals are equant and untwinned, with boundaries varying from tangential to planar, blocky, or interlocking (Figure 5B). Microcrystalline gypsum represents the matrix in all samples from different sections, and they are the most abundant components, particularly in samples from Section 1. Spheroidal dolomite microcrystals (ranging from 1 to 10 μm in size), often characterized by a hollow core, are found above the microcrystalline gypsum and around fractures (Figure 5E,F and Figure 6C).

Secondary gypsum is generally embedded within the microcrystalline gypsum matrix and displays various textures, including (i) acicular-like crystals, (ii) coarse crystals, (iii) fibrous gypsum, and (iv) fine-grained alabastrine gypsum. Acicular-like gypsum crystals (Figure 5C), observed only in samples from Section 2, appear randomly oriented, with crystal sizes ranging from 100 to 400 μm. The coarse-crystalline texture included anhedral and euhedral crystals, ranging in size from a few micrometers to several hundred micrometers. Coarsely crystalline anhedral gypsum exhibits irregular boundaries, chaotic distribution, and individual or grouped arrangements (Figure 5D,E). Moreover, they often display an amoeboid shape. Fibrous gypsum (Figure 5F and Figure 6B) consists of fibers ranging in width and length from 100 to 400 μm. They fill fractures and are bordered by thin, fluorescent layers.

Fine-grained alabastrine gypsum (Figure 5E) consists of a dense interlocking mosaic of prismatic to elongated crystals, generally more than 100 μm in size, with no apparent porosity.

The clay-rich laminae exhibit bright green fluorescence under UV light, denoting high organic matter content. Notably, laminae that macroscopically appear darker, such as those found in the Striscioli section, emit stronger fluorescence under UV light, despite showing no significant textural differences compared to other brown laminae.

Spheroidal dolomite microcrystals, terrigenous grains and tiny pyrite (<10 μm) are commonly found within these laminae (Figure 5E,F).

Pyrite (Fe = 46.5 wt%, S = 53.5 wt%) and celestite (Sr = 73.2 wt%, S = 26.8 wt%) crystals were identified through EDS analysis and observed in both layers, mainly in proximity to annealed fractures or in association with dolomite.

4.2.2. Lithofacies B–Nodular-Laminated Gypsum

Microscopically, Lithofacies B shows chicken-wire (B1) and enterolithic crenulation fabrics (B2) with the very same characteristics (Table 2). Indeed, the gypsum nodules of Lithofacies B1 and the gypsum layers of Lithofacies B2 are made up of microcrystalline gypsum (Figure 7A) with a predominantly alabastrine mosaic texture and abundant porphyroblastic gypsum (Figure 7A–D). Fibrous gypsum is also present in significant amounts, often in contact with fine-grained layers (Figure 7E). These layers, showing deformation when engulfed by gypsum nodules (B1) or parallel arrangements when they alternate with the gypsum layers (B2), exhibit a strong green fluorescence under UV light (Figure 7E) and contain a consistent aluminosilicate, as shown by SEM/EDS analysis (Figure 7F,G). Numerous dolomite microcrystals were detected within the fluorescent layers in both fabrics. An important feature is the presence of quartz crystals with a spherulitic shape (Figure 7H). Accessory minerals, such as pyrite and celestite, are abundantly distributed near annealed fractures or in association with dolomite.

4.2.3. Lithofacies C–Massive Gypsum

Microscopically, Lithofacies C is composed of primary and secondary gypsum (Figure 8A,B; Table 2), dolomite crystals, and terrigenous components. Primary microcrystalline gypsum is poorly preserved, while secondary gypsum, abundantly distributed, exhibits fibrous and alabastrine textures. Fibrous gypsum consists of fibers with variable widths and lengths (200 to 500 μm), which are widely distributed and border the terrigenous components (Figure 8C). Fibrous gypsum is often separated by dolomite layers or alabastrine gypsum (Figure 8C). Alabastrine gypsum exhibits a mosaic texture with crystal sizes of approximately 50 μm (Figure 8A). Both types of secondary gypsum show random arrangements. Spheroidal dolomite crystals (<10 μm in size) with hollow cores are distributed in layers or clusters (Figure 8C) and emit a bright green fluorescence under UV light (Figure 8E). In terms of morphologies and composition, Lithofacies C is very similar to Lithofacies A.

Terrigenous components (Figure 8C,D) exhibit sharp edges, and their deposition predates the precipitation of fibrous gypsum and the formation of dolomite layers. SEM analysis identifies these components primarily as calcite and quartz minerals.

4.2.4. Lithofacies D–Gypsrudite

Microscopic observation and analyses were conducted on the gypsum matrix and on the main type of clast embedded within it.

The matrix exhibits three main textures attributable to primary and secondary (Table 2) microcrystalline gypsum (<10 μm), coarse crystalline anhedral gypsum (ranging from a few micrometers to several hundred micrometers), and porphyroblastic gypsum (>200 μm). Relict microcrystalline gypsum (Figure 9A) is frequently covered with dolomite crystals that do not emit fluorescence under UV light. Coarse crystalline gypsum exhibits irregular boundaries (ameboid shape) and occurs in groups (Figure 9A). Porphyroblastic gypsum (daisy gypsum) forms from fibrous crystals arranged in a radial pattern (Figure 9B). Annealed or empty fractures are also observed. SEM analysis revealed that the contact zones between primary and secondary gypsum are often bordered by calcite crystals (with low Mg/Ca ratio) and by rounded pyrite crystals, either isolated or grouped (Fe = 53 wt%, S = 47 wt%) (Figure 9C,D). Prismatic radial gypsum growth is abundantly distributed in the fractures (Figure 9B).

The main clasts embedded within the gypsum matrix consist of (i) alabastrine gypsum, composed of a mosaic of crystals ranging from prismatic to granular, and (ii) the same gypsum crystals and terrigenous components recognized in Lithofacies B. SEM-EDX microanalyses conducted on the main clasts agree with the optical observation (Figure 9D).

4.2.5. Lithofacies E–Gypsiferous Mudstone

Lithofacies E is composed of a rhythmic alternation of dark white and dark brown laminae and shows very similar characteristics to those observed in Lithofacies A. Like laminar gypsum, this facies is laterally continuous and displays no evidence of current influence. However, it differs by its higher terrigenous input and lack of sharply defined boundaries at the microscale. Dark white laminae (Figure 10A,B) exhibit crystal sizes generally exceeding 200 μm; in contrast, the dark brown laminae (Figure 10C,D) are dominated by aluminosilicate and crystal sizes below 200 μm. Both types exhibit microcrystalline gypsum, alabastrine mosaic and porphyroblastic-coarse textures (Table 2). Unlike similar gypsiferous mudstone described in other Messinian deposits [66], Lithofacies E does not contain small conical structures or core aggregates within the layers.

As in the other facies, the presence of dolomite is also significant, occurring throughout the samples regardless of lamina type (Figure 10B).

Fibrous gypsum, consisting of fibers with a width less than 200 μm, is also present in both laminae.

5. Discussion

5.1. In Situ Gypsum Accumulation vs. Clastic Deposition

Across the three investigated sectors, a total of five gypsum lithofacies were identified. Lithofacies A and C are the only facies present in all three sections, while Lithofacies B was recognized in Sections 1 and 3, and Lithofacies D and E were observed exclusively in Sections 1 and 3, respectively. Field evidence, integrated with petrographic observation and chemical (EDS) analyses, supports the interpretation of Lithofacies A and B as products of in situ gypsum accumulation, whereas Lithofacies B, D and E exhibit characteristics consistent with clastic gypsum deposition, likely derived from the reworking of pre-existing gypsum.

5.1.1. Lithofacies A: Cumulate Deposit

Lithofacies A was recognized at the base of all three investigated deposits, and it is composed of microcrystalline gypsum. This facies can be interpreted either as the result of in situ gypsum precipitation or as a clastic (resedimented) deposit derived from the reworking and redeposition of earlier gypsum layers, as commonly reported in the literature [4,27,28,66,67,68,69,70,71,72,73,74,75,76,77,78,79]. The in situ precipitation of microcrystalline gypsum, initiated at the air–water interface and often leading to the accumulation of cumulate deposits [27,28,66,70,71,72,79], requires high supersaturation conditions, which may be favored by (i) strong periodic evaporation, which also increases the salinity of surface waters [73,74]; (ii) mixing of water masses of different chemical compositions and densities in stratified basins [75,76]; and (iii) the oxidation of sulfide accumulated in organic-rich bottom sediments through bacterial sulfate reduction and diffused upward in the water column until it reaches oxygenated waters above the oxycline [77,78]. Resedimented facies are often linked to deeper, distal depositional environments, where gypsum originally deposited in shallower settings is later reworked and redeposited by turbiditic or gravity flows, resulting in resedimented evaporitic deposits [23,79,80].

Based on field observations and petrographic evidence, Lithofacies A recognized in the Crati Basin represents an in situ cumulate. Field observations confirm that their accumulation can be traced laterally and forms numerous laminations. The white and light/dark brown laminae vary in thickness (ranging from fine to medium), providing a varved aspect (Figure 2A, Figure 3B and Figure 4A,B; [35,66]). This suggests that the seafloor was periodically draped by a “pelagic” rain of crystals and the influence of short-term climate oscillations from more arid (white gypsum laminae) to more humid (brown clay laminae) conditions. As previously mentioned, this lithofacies displays an alternation of light and dark laminae. The white laminae are common across all sampling sites and exhibit the same major chemical elements (Ca, S, K, Si and Al), as revealed by EDS analysis, and the same petrographic features (e.g., microcrystalline crystals). In contrast, the dark laminae vary in color from light brown to black. Microscopically, they do not show significant differences; however, chemical analyses reveal that as the color darkens, the aluminosilicate contribution increases. Petrographically, both laminae show mainly primary microcrystalline gypsum, but also secondary gypsum was recognized: acicular-like, coarse, fibrous and fine-grained alabastrine. Acicular-like crystals show random arrangements and were formed into dissolution-related voids within the gypsum matrix; the space to extend in length may be the key factor for their arrangements [36,39,81]. They are defined as acicular-like because, unlike strictly acicular crystals reported in the literature, they do not exhibit a pointed termination with a distinctly pyramidal shape [81].

The acicular-like crystals were formed by the replacement of primary gypsum, but their origin took place at the eogenetic stage, still under the influence of the depositional setting. These gypsum morphologies are closely related to the laminated evaporites, serving to demonstrate that their formation was related to replacements that did not affect the primary sedimentary structures [81].

Coarsely crystalline anhedral gypsum shows interlocking (ameboid) crystalline boundaries and is formed to replace mainly carbonate or primary gypsum [20] at the telogenic stage. This phenomenon is a result of fine crystal conversion to coarse crystal through the diagenetic process, which is affected by the deformation conditions (i.e., temperature) [82,83].

Fibrous and elongated gypsum crystals are observed growing within fractures [34,39,41], often accompanied by dolomite crystals lining the fracture walls. These fractures likely resulted from the partial dissolution of a CaSO₄ precursor phase (possibly anhydrite) under changing geochemical conditions, leading to the concentration of less soluble residual components [40]. The precipitation of dolomite in these settings is interpreted as a result of late-stage diagenetic processes, possibly triggered by the infiltration of Mg-rich fluids during deep burial or uplift. Such conditions are characteristic of the telogenetic realm. Therefore, the co-occurrence of gypsum and fracture-hosted dolomite suggests that crystal growth occurred during telogenetic alteration, rather than during early (eogenetic) diagenesis.

Alabastrine consists of a dense, interlocking mosaic of prismatic to elongated crystals. Contrary to Ortí et al. [34] and Rafei and Rahmani [37], no prismatic and granular shapes and relics of anhydrite have been observed. Alabastrine can be created where precursor anhydrite rehydrates to gypsum (in the zone of active phreatic flow) [37,41], or it can replace the host rock as well as any pre-existing gypsum texture. Thus, no remains of gypsum components, native sulfur, or celestite crystals are observed within these replacive textures [34].

Major non-detrital minerals found are dolomite, pyrite and celestine. Subspherical dolomite crystals that emit a bright green fluorescence are recognized in the white laminae but are significantly greater in the brown laminae. Their crystal’s habit and fluorescence agree with previous studies that consider the dolomite as a product of bacteria mediation ([66] and references therein). Pyrite framboids are often associated with dolomite crystals in the brown laminae, precisely because the formation of dolomite is due to an increase in alkalinity, which, by releasing hydrogen sulfide, reacts with iron and mediates pyrite precipitation. Small celestine crystals are recognized in both primary and secondary gypsum and are derived from diagenetic processes [20,31,84,85,86,87].

The difference in color of the dark laminae is related to a cyclic sedimentation process. The light laminae represent periods of more stable deposition, during which environmental conditions and sedimentary dynamics did not change significantly and where sedimentation is dominated by a pelagic rain of crystals. In Section 3 these laminae show a light enterolithic fold probably attributed to in situ soft sediment deformation [88]. Variable amounts of organic-rich terrigenous materials mixed with gypsum deposition originate the dark laminae, indicating a change in the environmental conditions and sedimentary dynamics [66]. EDS chemical analyses and epifluorescence agree with a major number of terrigenous components during the deposition of the dark in comparison to the white laminae.

5.1.2. Lithofacies B: Diagenetic Deposit

The nodular gypsum lithofacies are typically regarded as having formed through diagenetic processes, specifically by the rehydration of anhydrite back to gypsum. Evidence for sabkha origin in a supratidal environment for these gypsum nodules has been reported by previous research [71,88,89]. These facies are frequently found in association with laminated gypsum [90,91], and the association with subaqueous sediments, such as laminated and reworked gypsum, along with observed deformation in adjacent gypsum laminae caused by nodule growth, suggests a late diagenetic origin. This is further supported by the partial anhydritization of gypsum [92,93], which is linked to the interstitial growth of displacive sulfate within laminated gypsum facies. In the samples investigated, the transformation of anhydrite into gypsum appears to be complete, as evidenced by the micromorphology of the crystals, which exhibit characteristics more typical of gypsum than anhydrite, and the presence of H₂O detected during EDS analyses. These findings suggest that the process of anhydritization has been fully completed, with the gypsum structure now stabilized. This is confirmed by the presence of fibrous, porphyroblastic and rosette gypsum and quartz crystals with a spherulitic shape, typical of crystallographic changes in the telogenetic realm [40]. Indeed, porphyroblastic gypsum crystals form during the later stages of crystallization or recrystallization (telogenic realm), typically when there is a shift in the formation conditions, such as temperature or pressure. This texture is common in diagenetic gypsum [36,39], where gypsum undergoes hydration or recrystallization, producing large, often anhedral crystals surrounded by smaller ones. The textural development of porphyroblastic gypsum can also be influenced by environmental factors like water chemistry, tectonic activity, and the rate of evaporation [34,39]. A particular porphyroblastic texture with a daisy shape (fibrous crystals that arrange into a radial pattern) has also been recognized in Section 3; this gypsum is formed under rather homogenous conditions when massive nodular anhydrite units enter the lowermost parts of the telogenetic zone [41].

Gypsum rosettes are pseudomorphs of secondary gypsum after anhydrite. They represent the latest phase of evaporite formation in the study section, resulting from either intra-stratal waters or surface waters during weathering (e.g., [20,31,85,86,87]), and formed mainly in the telogenetic realm.

Enterolithic and chicken wire structures observed in nodular gypsum are two distinct textural features that arise from different diagenetic processes. Enterolithic structures, characterized by an interlocking network of elongated, irregular crystals, are typically considered to result from a rapid, localized rehydration of anhydrite to gypsum under conditions of restricted fluid flow. Chicken wire structures, which appear as a network of thin, interconnected laminae or filaments, are generally attributed to later stages of diagenesis, particularly when gypsum is subjected to more prolonged fluid interactions or partial recrystallization. This pattern is thought to form due to differential expansion and contraction of gypsum crystals during the evaporation process, creating a mesh-like arrangement.

Both enterolithic and chicken wire fabrics are commonly observed in modern and ancient sabkha deposits [73,94]. However, as reported by Lugli et al. [69] and Hardie and Lowenstein [72], such structures may also develop as a result of diagenetic transformations induced by lithostatic burial and therefore do not necessarily indicate a sabkha origin. In the studied sections, Lithofacies B shows a vertical transition to Lithofacies C, indicating the development of an evaporative shoaling platform influenced by highstand-lowstand-highstand cycles, as documented in other basin successions [91]. Considering the stratigraphic context and the sedimentological features observed, a sabkha-related origin remains the most plausible interpretation for these fabrics in the studied area.

5.1.3. Lithofacies C: Gypsarenite Deposit

During field observations, this lithofacies, characterized by lateral continuity, absence of deformational structures, and a massive texture, seems to result from in situ precipitation. However, both optical and electron microscopy observations revealed structures consistent with diagenetic processes, supporting its classification as a pebbly gypsarenite [23,90]. This facies shows massive appearance consisting of a gypsum matrix and abundant terrigenous grains (calcite and quartz). Primary cumulate crystals are not well preserved, whereas secondary gypsum textures (such as fibrous and alabastrine) are abundantly present. Layers of dolomite crystals, exhibiting bright green fluorescence and well-defined pyrite crystals, are also identified. While this facies does not show evidence of slides or slumps, the formation of massive, parallel strata suggests that it likely results from the erosion, reworking and diagenesis of coeval exposed crystalline gypsum deposits [90].

During field observations, these lithofacies, characterized by lateral continuity, absence of deformational structures, and a massive texture, appear primary in origin. However, both optical and electron microscopy analyses revealed structures consistent with diagenetic processes, supporting its classification as a pebbly gypsarenite [23,90]. These facies show a massive appearance consisting of a gypsum matrix and abundant terrigenous grains (calcite and quartz). Primary cumulate crystals are not well preserved, whereas secondary gypsum textures (such as fibrous and alabastrine) are abundantly present. Layers of dolomite crystals, exhibiting bright green fluorescence and well-defined pyrite crystals, are also identified. While these facies do not show evidence of slides or slumps, the formation of massive, parallel strata suggests that it likely results from the erosion, reworking and diagenesis of coeval exposed crystalline gypsum deposits [90].

The identification of Lithofacies C (gypsarenite) above Lithofacies D (gypsrudite) reflects environmental and depositional variations, testifying to a transition from low-density gravity flows (turbidites flow in the central basin) to high-density gravity flows, inducing slumps and olistostromes (debrites flow in the deeper basin) formation. Turbidites and debrites do not necessarily suggest a great water depth, but rather a particular relief within the basin [95].

5.1.4. Lithofacies D: Gypsrudite Deposit (Olistostrome)

The formation of gypsrudites occurs in sedimentary environments where fine-grained, evaporitic material is transported and deposited by debris currents, typically triggered by a sudden disturbance such as a slope failure. This disturbance causes the resuspension of sediments, leading to their subsequent downslope flow. In these conditions, previously deposited gypsum can be eroded and transported, along with other evaporitic minerals, eventually being deposited in deeper basin settings. These deposits are commonly associated with features like slump and slide structures [23], reflecting the dynamic and episodic nature of the depositional process. Lithofacies D, observed only in Section 1, shows slumps and slides and incorporated fragments from Lithofacies A and C. It is observed in outcrops as discrete blocks, suggesting a two-stage transport mechanism: the first stage corresponds to the disintegration of pre-existing gypsum deposits (Lithofacies A and C), followed by their reworking and transport during the second stage, resulting in the formation of gypsrudites. Overall, this facies could be attributed to an olistostrome.

5.1.5. Lithofacies E: Gypsiferous Deposit

Gypsiferous mudstones exhibit several similarities with laminated gypsum (i.e., distinct lamination, lateral continuity of the layers, and absence of bottom currents evidence). These features suggest that gypsiferous mudstones may be interpreted as cumulate deposits [66]. However, in contrast to pure gypsum deposits, the laminae in gypsiferous mudstones consist of a mixture of pelagic gypsum crystals, aluminosilicate, and organic material. The observed mixing is likely the result of a decrease in gypsum nucleation within the water column, coupled with an increased influx of terrigenous components into the basin. A greater influx of detrital sediments than observed in Lithofacies A suggests an increased incidence of precipitation and erosion in the surrounding areas. This could be indicative of a more variable climate or an increase in rainfall, which brings more sediments into the basin.

5.2. Crati Basin Lithofacies in the Context of Messinian Environmental Dynamics

Lithofacies A, characterized by laminated cumulate gypsum and identified at the base of the three sedimentary sections, closely resembles the primary evaporitic deposits observed along the margins of other Messinian basins, particularly in the Northern Apennine (i.e., Vena del Gesso Basin [96]), the Piedmont (i.e., Alba section [5,66]), and Southern Apennines (i.e., Caltanisetta Basin, Eraclea Minoa [8,9,97]), where similar cumulate gypsum lithofacies have been extensively documented and known as “balatino”. These lithofacies were also recognized in all the cores that cut through the topmost deposits of the Messinian Salinity Crisis lying below the floor of the Mediterranean Sea [69].

According to stratigraphic and sedimentological data from the literature [8,66,69,70,98,99], cumulate deposits formed during both the initial (stage 1) and the acme (stage 2) of the Messinian Salinity Crisis through direct precipitation from oversaturated saline waters. During the first stage, these deposits typically accumulated along basin margins that were not affected by significant erosion. They are characterized by microcrystalline textures and well-laminated structures [66,70,98]. These gypsum layers exhibit a marked small-scale cyclicity, generally interpreted as resulting from annual or pluriannual climatic fluctuations [90]. In contrast, the cumulate facies associated with the second stage of the MSC [8,69,99], found in more central and deeper parts of the basins, often display more complex varve-like alternations of evaporitic and clastic material. These deposits reflect highly stratified water columns and increased basin isolation, with a more pronounced imprint of climate-controlled cyclicity. Indeed, detailed statistical analyses (e.g., laser ablation studies) conducted on gypsum deposits from the Northern Apennines [99], as well as petrographic and sedimentological studies from Sicily [8], support the interpretation of these lithological cycles as being of annual origin. These investigations also indicate that the MSC (particularly during its peak) was not characterized by stable evaporitic conditions but rather by pronounced seasonal and multiannual climatic variability. Specifically, spectral analyses performed on Messinian gypsum sequences have revealed periodicity peaks corresponding to intervals of approximately 3–5, 9, 11–13, 20–27, and 50–100 years, potentially linked to quasi-periodic climatic oscillations such as the Quasi-Biennial Oscillation [8].

The studied lithofacies display a microcrystalline cumulate texture and regular millimetric lamination, commonly associated with gypsum formed through in situ precipitation from supersaturated brine. The stratigraphic position and depositional setting do not allow for a definitive attribution to a specific stage of the Messinian Salinity Crisis. The absence of desiccation features, the fine lamination, and the presence of dolomite and organic matter within the matrix are consistent with deposition under a stratified, subaqueous environment, similar to that described for both marginal early-stage deposits and deeper basin facies associated with the acme of the crisis. Although geochemical or isotopic constraints are currently lacking, the stratigraphic association with overlying clastic gypsum facies makes a formation during the second stage of the MSC the most plausible hypothesis.

Lithofacies B exhibits characteristic features such as chicken-wire fabric and enterolithic crenulation fabric, which are specifically described in Messinian evaporite deposits from the Southern Apennines [95] and in Northern Cyprus [91]. The nodular gypsum facies documented by Matano et al. [95] are associated with the Primary Lower Gypsum unit of the MSC (5.97–5.60 Ma), whereas those described by Varol and Atalar [91] in Northern Cyprus belong to the Upper Gypsum (5.60–5.55 Ma).

Based on petrographic and stratigraphic evidence, the studied Lithofacies B closely corresponds to the nodular gypsum facies (F1) described by Varol and Atalar [91] within the Upper Gypsum of the Mesaoria Basin (Northern Cyprus). In their study, the nodular gypsum facies are characterized by enterolithic and chicken-wire textures and interpreted as having formed under marginal evaporitic conditions, likely in a sabkha-type environment influenced by early diagenetic processes. These deposits occur at the base of the evaporitic succession and are associated with shallowing-upward cycles, typical of highstand-lowstand dynamics. Similarly, Lithofacies B in the investigated sections exhibits nodular morphologies and deformation structures consistent with the F1 facies [91] and is stratigraphically positioned between laminated cumulate gypsum and clastic gypsum deposits. This vertical arrangement, along with the observed textural similarities, supports the interpretation of Lithofacies B as a sabkha-related gypsum facies deposited under conditions comparable to those reported in Varol and Atalar [91]. Although these features are analogous to those observed in the Mesaoria Basin, its development appears to be primarily controlled by specific environmental conditions, such as marginal settings with episodic exposure and early diagenetic processes.

Interestingly, the nodular gypsum lithofacies were only identified in two sections (Castelluccio and Piretto) of the Crasi Basin. This uneven distribution likely reflects local variations in depositional environments during the Messinian Salinity Crisis. The development of nodular gypsum, with chicken-wire and enterolithic fabrics, typically requires conditions of pronounced evaporation, frequent alternations between subaerial exposure and shallow water flooding, and episodic freshwater influxes. These conditions may be consistent with the climatic fluctuations documented during the second stage of the MSC. Therefore, it can be inferred that the Castelluccio and Piretto sections were located in more marginal, intermittently exposed sections of the basin, experiencing stronger evaporative stresses and periodic hydrological fluctuations. In contrast, the Striscioli section, where nodular gypsum is absent, may have been situated in a slightly deeper or more stable subaqueous environment, where continuous submersion inhibited the formation of sabkha-like features and promoted more laminated gypsum deposition.

Lithofacies C, corresponding to gypsarenites, was identified in all three studied sections of the Lattarico area, albeit in different stratigraphic positions. In the Castelluccio and Piretto sections, gypsarenites are found overlying the nodular gypsum units, whereas in the Striscioli section, they occur interbedded between two laminated gypsum layers. Such distribution points to local variations in depositional dynamics within the basin. Gypsarenite deposits testify to episodes of gravity-driven redeposition of pre-existing evaporites during tectonic activity and basin reorganization. This interpretation is supported by well-documented examples from the Southern Apennines [95] and the northern Apennines Adriatic foredeep [23], where gypsarenites occur as part of deep-water clastic evaporite systems and often display characteristics such as chaotic structures, discontinuous lateral facies, and erosive bases.

The gypsarenite deposits observed in the Lattarico area do not fully match these classical features. Despite being present in all three sections, the Lattarico gypsarenites show remarkable lateral continuity at the macroscale and lack the disorganized textures, sharp basal contacts, and brecciated structures typically associated with gravity-flow processes. This suggests that the Lattarico gypsarenites may not have formed through large-scale slope instability or mass transport. A possible explanation for this discrepancy is that the gypsarenites in the Lattarico area represent a lower energy depositional setting, possibly related to local reworking of marginal gypsum deposits under stable hydrodynamic conditions or to fine-scale density-driven flows that redistributed clastic gypsum without inducing the structural disruption observed in other basins. Alternatively, these deposits may reflect shallow-water sediment gravity flows restricted to confined sub-basins, lacking the energy or slope necessary to produce the classical chaotic facies. Their consistent stratigraphic presence across all sections highlights a basin-wide event, yet one that likely occurred under more quiescent, less tectonically influenced conditions than those described in the classical Apennine examples, which could also occur during the second stage of the MSC.

The Lithofacies D, characterized by clastic gypsum and interpreted as an olistostrome, was identified only in the Castelluccio section, where it occurs at the top of the evaporitic succession. According to Manzi et al. [23], gypsrudites in the Northern Apennines formed during the second stage of the MSC (5.60–5.55) as a result of gravitational resedimentation processes following tectonic uplift, subaerial exposure, and collapse of marginal evaporitic basins. The gypsrudites described there are associated with high-density debris flows and submarine slumps that transported large gypsum clasts into deep foredeep settings. The occurrence of gypsrudite only in the Castelluccio section suggests localized tectonic instability or basin margin collapse affecting that specific area during the late stages of the Messinian Salinity Crisis. This interpretation aligns with the genetic model proposed for other Messinian gypsrudites [23], where gypsum breccias and chaotic deposits similarly record gravity-driven redeposition triggered by tectonic activity and sea-level fluctuations during the MSC. In the Castelluccio section, the absence of a clearly defined Messinian Erosional Surface (MES) may be due to the dual formation mechanism of this deposit: a first phase involving the disintegration of pre-existing Lithofacies A and C, followed by a second phase of reworking, transport, and redeposition of the resulting debris as gypsrudites, which may have obscured or removed any original erosional features. Overall, the limited presence of gypsrudite in Lattarico supports the view that the basin experienced spatially variable tectonic and hydrological conditions during the latest Messinian, with localized destabilization events leading to resedimentation in specific settings, while others maintained more continuous, undisturbed evaporitic sedimentation.

Lithofacies E, similarly to Lithofacies A, displays laminated structures, pelagic gypsum crystals, and features indicative of in situ precipitation and shows many similarities with the gypsiferous facies described by Natalicchio et al. [66], which was attributed to the first stage of the Messinian Salinity Crisis (MSC). However, Lithofacies E, compared to Lithofacies A, is enriched in detrital material, suggesting a more substantial terrigenous input during deposition. Despite its resemblance to both the facies described by Natalicchio et al. [66] and to Lithofacies A, the stratigraphic position of Lithofacies E at the top of the deposit, overlying laminated Lithofacies A, B and C, supports a different interpretation. Indeed, this vertical arrangement suggests that Lithofacies E could have formed under transitional conditions following the main phase of evaporite deposition, during a period characterized by increased sediment influx and environmental instability. Therefore, it is more consistent with deposition during the second stage of the MSC, reflecting a shift toward more dynamic hydrological and climatic conditions.

The stratigraphic and sedimentological analysis of the three Lattarico sections reveals significant spatial variability in depositional environments during the MSC, reflecting different dynamic processes of basin evolution. In the Castelluccio section, the lithofacies sequence A-B-C-B-C-D documents a progressive transition from relatively stable evaporitic conditions (Lithofacies A: laminated cumulate gypsum) to increasingly dynamic marginal environments (Lithofacies B: nodular gypsum, associated with intermittent exposure and subaerial processes). The recurrence of gypsarenite deposits (Lithofacies C) suggests repeated episodes of gravitational reworking, culminating with the deposition of a gypsrudite layer (Lithofacies D), indicative of localized tectonic instability.

In the Striscioli section, the simpler alternation of Lithofacies A-C-A reflects more stable conditions overall, with dominant in situ gypsum precipitation (Lithofacies A) and limited low-energy reworking events (Lithofacies C). The absence of nodular gypsum and resedimented facies suggests that this sector of the basin remained submerged and tectonically undisturbed.

In the Piretto section, the lithofacies succession A-B-A-E indicates a more stable evolution, with initial cumulate gypsum (A), followed by development of nodular gypsum (B), another phase of cumulate gypsum (A), and ultimately the deposition of a gypsiferous mudstone (E). The absence of gypsrudite suggests that Section 2 was less affected by tectonic destabilization compared to Section 1.

Overall, the variability among the three sections highlights how local topography, hydrological dynamics, climate and tectonic activity controlled the sedimentary evolution of the Crati Basin during the second stage of the MSC.

Although the current interpretations are primarily based on petrographic and stratigraphic observations, a new phase of research is now underway to refine and strengthen these correlations. Ongoing geochemical and geobiological investigations aim to resolve subtle temporal and environmental differences among the three sections and to better integrate the Lattarico record within the broader framework of Mediterranean Messinian basins. These approaches will provide a more robust basis for regional correlations and paleoenvironmental reconstructions.

6. Conclusions

The integrated sedimentological and petrographic analysis of the three Lattarico sections provides a comprehensive view of the spatial and temporal variability of evaporitic deposition in the Crati Basin during the Messinian Salinity Crisis (MSC). Despite their proximity, the three sections exhibit distinct lithofacies successions that reflect localized variations in basin morphology, hydrodynamic regime, and climatic forcing.

Section 1 (Castelluccio) records the most complete and dynamic depositional evolution, encompassing both in situ gypsum accumulation and clastic deposits, culminating in the formation of gypsrudites indicative of tectonic destabilization and margin collapse. The succession suggests that this section was more exposed to slope failure processes and the reworking of previously deposited evaporites.

Section 2 (Striscioli) is characterized by a simpler alternation of laminated gypsum and gypsarenite, lacking evidence of nodular gypsum or brecciated facies. This stability points to a persistently submerged environment, with minimal subaerial exposure or gravitational redeposition. The presence of localized deformation structures and recurrent laminated deposits suggests that this section preserved a more continuous record of in situ gypsum accumulation, shaped by the interplay of climatic oscillations, hydrological isolation, and gradual basin infilling.

Section 3 (Piretto) presents a distinctive succession with evidence of early nodular gypsum formation, followed by renewed cumulate deposition and capped by gypsiferous mudstones. These facies associations imply a transition toward stratified, low-energy conditions potentially linked to enhanced terrigenous input and reduced water renewal.

Overall, the facies distribution across the Crati Basin underscores the heterogeneous response of sub-basins to the regional controls of the MSC, including climate-driven salinity variations, episodic tectonic activity, and differential accommodation space. Among the recognized units, Lithofacies A (laminated cumulate gypsum) provides a common stratigraphic marker across all sections. In contrast, the occurrence of nodular, clastic, and mudstone facies varies significantly, reflecting the influence of local environmental conditions on the development and preservation of the evaporitic record.