Caltanissetta Basin Research Articles

Structural styles and regional tectonic setting of the “Gela Nappe” and frontal part of the Maghrebian thrust belt in Sicily

The Gela Nappe of south central Sicily provides an example of a curved segment of an orogenic front that can be examined both onshore and offshore for deformational style and amount of shortening. Synorogenic sediments allow the deformation to be dated. Two distinct structural styles are observed in the Gela Nappe: The central salient part of the nappe (Caltanissetta basin) consists of a single thrust sheet containing a train of continuously tightening folds and the reentrant margins of the nappe (Sciacca and Monte Judica) consist of a stack of several thrust sheets. These different structural styles correspond to the pretectonic Mesozoic stratigraphy of the foreland plate. Carbonate platforms exist on the Adventure bank and Hyblean Plateau ahead of Sciacca and Monte Judica, respectively, while the Caltanissetta basin region appears to have accumulated basinal clay facies. Where the resistant carbonate stratigraphy provides a buttress to the propagation of the thrust front, deformation is taken up by imbrication on‐steep ramps through the carbonates generating a relatively thick orogenic wedge. In the basinal setting, where no strong rheology exists, the low angle of friction on the clay detachment levels requires the growing thrust wedge to be much thinner with a very low foreland dip. Hence the thrust front propagates much farther forward into the basin than it does in the adjacent platformal areas, producing a nonlinear thrust front. In the basinal region, accretion of foreland material to the nappe by imbrication was only prominent during the Messinian when subaerial exposure prevented low‐friction transport of the nappe across the highest levels of the stratigraphy. A steady thickening of the nappe by internal folding suggests an increase in friction along the basal detachment, possibly due to progressive compaction of the clays.

Calibrating the duration and timing of the Messinian salinity crisis in the Mediterranean: linked tectonoclimatic signals in thrust-top basins of Sicily

The Messinian 'salinity crisis' which affected the Mediterranean represents one of the most dramatic examples of base-level fluctuation known in the geological record: an amplitude of perhaps 2 km within a stage with a duration of less than 2 Ma. Deposits within the Caltanissetta Basin of central Sicily are used to calibrate the duration and timing of these fluctuations. Two successions of evaporites termed 'First Cycle' and 'Second Cycle', are separated by an inter-regional unconformity. The first cycle is regionally regressive while the second is transgressive. Chronostratigraphic calibration of these deposits has been provided by a linked magnetostratigraphic, structural and sedimentological study. The regression was protracted. The earliest evaporites in our study accumulated early in Chron C3Ar (pre 6.88 Ma) and the youngest accumulated late in chron C3An (post 6.0 Ma). During this interval the basinward shift in coastline was 70 km and in vertical section implies a relative fall in sea level at 0.3–0.4 m ka– 1 Lowstand probably finally occurred at 5.8–5.5 Ma. Transgression, marked by accumulation of the 'second cycle' deposits, which all record reversed magnetizations (C3r), apparently occurred far more rapidly (200 ka), prior to the return to 'normal' marine conditions in the central Mediterranean late in Chron C3r. Local rates of tectonic deformation are relatively slow within the thrust belt which underlies the Caltanissetta Basin. Therefore, it is likely that the timing and rates of the Messinian 'salinity crisis' on Sicily are generally applicable to other basins in the region and help to underpin rates of climate change within this part of the Neogene.

The Mediterranean water body in the late Messinian: interpreting the record from marginal basins on Sicily

The stratigraphic record of climatic and palaeoceanographic changes in the Mediterranean during the late Messinian is controversial. On Sicily, sedimentary facies show a steady transgression, suggesting that sub-basins were hydrodynamically linked to a larger water body. Here we test this hypothesis using strontium isotope studies from Messinian materials collected from a range of sites in the Caltanissetta Basin of central Sicily. The strata include a regionally regressive ‘First Cycle’ of early-mid-Messinian age and a younger, transgressive ‘Second Cycle’. These cycles are separated by an inter-regional unconformity which may be correlated with base-level low stand in the Mediterranean. 87 Sr/ 86 Sr ratios for all First Cycle gypsum fall within the expected global marine composition (0.70891–0.70897). All Second Cycle analyses fall within a grouping of significantly lower values (0.70868–0.70878), a surprisingly tight but discrepant grouping for data collected from shells of a brackish water fauna and from gypsum. Analyses from these different Second Cycle materials are statistically indistinguishable. These results indicate that the strontium isotopic composition of waters from different sub-basins on Sicily are indistinguishable regardless of salinity during the late Messinian. Therefore these basins must have mixed with a larger, homogenized reservoir which we infer was the ancestral Mediterranean. Thus circum-Mediterranean basins may indeed chart regional palaeoceanographic and climatic events. By the end of Messinian times the base-level of the Mediterranean was within the range of the world's oceans but the water-body probably had a distinctly different but internally homogeneous strontium isotopic composition.

Strontium geochemistry of Miocene primary gypsum; Messinian of southeastern Spain and Sicily and Badenian of Poland

ABSTRACT The strontium contents of primary marine gypsum facies were studied in Messinian (Upper Miocene) basins of SE Spain and Sicily, and in the Badenian (Middle Miocene) Carpathian foreland basin of Poland. The results obtained were interpreted on the basis of the findings reported for the gypsum facies of recent salinas in the western Mediterranean coast. The strontium profile obtained from the lower part of the gypsum deposit of the Sorbas basin (SE Spain) has homogeneous strontium contents, reflecting deposition under conditions of hydrological stability and relatively deep waters, but the upper part has a more variable strontium content related, in accordance with other sedimentological criteria, to a shallowing of the basin. This is consistent with data reported from other Messinian basins of SE Spain (San Miguel de Salinas and Palma de Mallorca). In the Caltanissetta basin (Sicily), the section studied in Eraclea Minoa (Upper Evaporite) is made up of 6-8 gypsum cycles that have a facies evolution from fine-grained laminar gypsum at the base of each cycle to selenites at the top, accompanied by increasing strontium values. This evolution is attributed to increasing salinity conditions and is consistent with geochemical data reported in the literature. In the Badenian basin the six gypsum sections studied are from different subbasins. The gypsum deposits comprise two members. In the lower member, which is mainly selenitic, two parts can be differentiated and a significant strontium increase (attributed to a rise in salinity) was recorded in the transition from the lower to the upper part. In the upper member, which is mainly clastic gypsum, a general strontium decrease indicates a fall in salinity linked to a deepening or freshening of the platform. In the Badenian selenitic layers a lateral variation in the strontium contents exists: higher and less homogeneous strontium contents were recorded in the marginal zones, suggesting variable salinity conditions, whereas in the deeper areas the gypsum layers show more homogeneous strontium values, expected from more stable and less concentrated brines. This distribution is in agreement with data reported from the Messinian basin of San Miguel de Salinas (SE Spain). The strontium contents in both the Messinian and Badenian selenitic samples are lower than those in the selenitic crusts of the recent salinas. These lower contents may be a result of a lower salinity of the mother brines at the steady state achieved during the precipitation of the thick selenitic sequences, with respect to the highly concentrated (with no reflux) brines of the recent salinas. Our findings highlight the relevance of studying strontium contents in primary gypsum facies of marine formations as a tool for interpreting the paleogeography and the paleosalinity of the evaporitic enviroents and for correlating cyclic selenite formations. This method could be especially helpful when combined with other geochemical indicators (i.e., isotopic and/or fluid inclusions composition).

A magnetostratigraphic study of the onset of the Mediterranean Messinian salility crisis; Caltanissetta Basin, Sicily

Abstract The Messinian ‘salinity crisis’ marked a dramatic climatic change in the Mediterranean region. The timing and extent of this event remain controversial, with conflicting models ranging from predictions of rapid and catastrophic dessication of all of the Mediterranean basin at once, to progressive draw-down of sea-level causing gradual onset of evaporite formation starting at the margins of the Mediterranean Sea. In this paper the preliminary magnetostratigraphy is described of two sections in the Neogene Caltanissetta basin, Sicily, containing the early Messinian Tripoli Formation, which pre-dates evaporite formation, and the overlying Calcare di Base shallow water carbonates that mark the first evaporite phase. The magnetisation of the sediments has been extensively overprinted by recent weathering, but primary or early diagenetic remanences which pass reversal and fold tests have been isolated. This has been possible because the sections have been tilted by Pliocene tectonic movements, thus rotating the pre-tilt remanence direction away from the later overprint direction, allowing resolution of the components by great circle analysis. The sections have been correlated with Krijsman et al .’s revision of the geomagnetic polarity time scale (GPTS) of Cande & Kent. This was achieved by comparing variations in the sediment rate derived from the alternative matches with the GPTS with the observed proportions of diatomite (relatively fast deposition) and clay (slow deposition). The proposed correlation puts the base of both sections at or close to the start of the Messinian, but predicts diachroneity in the onset of Calcare di Base deposition between the two sections, as the base of the Calcare di Base falls in opposite polarity chrons in the two sections. The sections lie in two separate sub-basins controlled by thrust anticlines of the Maghrebian thrust belt. Structural and sedimentological evidence suggests that the onset of evaporite formation in these perched basins was strongly controlled by the extent and development of the emerging anticlines. The magnetostratigraphy provides a first positive test of this prediction of tectonically controlled diachroneity of facies. Further palaeomagnetic work is in progress to assess the relative timing of evaporite formation on Sicily in more detail.

Evolution of the Messinian Mediterranean environments: the Tripoli Formation at Capodarso (Sicily, Italy)

New field data have been collected from the Capodarso section (Caltanissetta basin, Sicily); 48 samples from the Tripoli Formation were analysed for foraminifera, dinocysts, palynofacies, CaCO 3, pollen grains and clay minerals. The uppermost clays of the Terravecchia Formation are clearly the result of deeper deposition than those corresponding to the lowermost analysed samples within the overlying Tripoli Formation. So, the general evolution of the basin was from normal marine conditions to confinement, during which the sedimentation of diatomite vs. clay was mainly controlled by relative sea-level changes. Three successive types of processes are considered to have generated the diatomites: 1. (1) in the lower part of the section, the sea level was relatively high and deposition of diatomites was aided by sea-level rises of unequal importance and variations of continental precipitations and run-off; 2. (2) then, relatively minor sea-level oscillations prevailed; however, the second part of the sequence is characterized by a generally strong shallowing trend leading to basin confinement; 3. (3) the explanation for diatomites during the last member does not rely as much on the occurrence of substantial sea-level rises in an increasingly desiccated basin; on the other hand, an increased number of rivers reached the central area of the basin, which helped to produce the youngest diatomites. The warm (subtropical to tropical) and xeric climate predisposed to such an evolution, inducing continuous high salt-concentration of marine waters; so, the smallest influx of less saline (oceanic) waters and/or continental freshwater (run-off) could produce water-mass stratification and diatomite deposition. However, not all lithologic breaks are likely to correspond to recorded environmental transitions. Bio- and magnetostratigraphy of the section allow consistent relationships between the sea-level curve at Capodarso and the δ 18O curve at Site 588 (southwest Pacific), attesting global eustatic control on the sedimentation of the Caltanissetta basin up to the beginning of the Messinian salinity crisis.

Tectonics and sequence stratigraphy in Messinian basins, Sicily: Constraints on the initiation and termination of the Mediterranean salinity crisis

Research Article| April 01, 1995 Tectonics and sequence stratigraphy in Messinian basins, Sicily: Constraints on the initiation and termination of the Mediterranean salinity crisis Robert W. H. Butler; Robert W. H. Butler 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom Search for other works by this author on: GSW Google Scholar W. Henry Lickorish; W. Henry Lickorish 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom Search for other works by this author on: GSW Google Scholar Mario Grasso; Mario Grasso 2Istituto di Geologia e Geofisica, Università di Catania, Corso Italia, Catania, Italy Search for other works by this author on: GSW Google Scholar H. Martyn Pedley; H. Martyn Pedley 3School of Geography and Earth Resources, University of Hull, Hull HU6 7RX, and Department of Geology, University of Leicester, Leicester, United Kingdom Search for other works by this author on: GSW Google Scholar Lamberto Ramberti Lamberto Ramberti 4Italkali, Palermo, Italy Search for other works by this author on: GSW Google Scholar GSA Bulletin (1995) 107 (4): 425–439. https://doi.org/10.1130/0016-7606(1995)107<0425:TASSIM>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert W. H. Butler, W. Henry Lickorish, Mario Grasso, H. Martyn Pedley, Lamberto Ramberti; Tectonics and sequence stratigraphy in Messinian basins, Sicily: Constraints on the initiation and termination of the Mediterranean salinity crisis. GSA Bulletin 1995;; 107 (4): 425–439. doi: https://doi.org/10.1130/0016-7606(1995)107<0425:TASSIM>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Deposits within the Caltanissetta basin of central Sicily have been important for developing the desiccating deep basin model for the Messinian salinity crisis in the Mediterranean. Linked structural and stratigraphic studies show that the Sicilian depocenters are synclines related to underlying thrust structures of the frontal part of the Maghrebian chain. Prior to the salinity crisis these basins were hydrodynamically linked through the foredeep to the Mediterranean. The precursor sediments (Terravecchia Formation) formed a delta, sourced from the north. Early Messinian regression acted on a range of paleobathymetries, shallow in the north and progressively deeper in the south, locally complicated by active thrust structures. Initial draw-down of Mediterranean base level is marked across the thrust belt by first cycle carbonates and evaporites on the structural highs and lows, respectively. Vast accumulations of halite and potassium salts (up to 1200 m) are restricted to growing thrust synclines. The different evaporite signatures may be related to different water conditions reflecting various meteoric and marine circulations across various subbasins, with cyclicity reflecting high-frequency variations in sea level. A sequence stratigraphic model is developed to explain fractionation of evaporite facies between different paleobathymetric settings and to predict the temporal evolution of the successions in different subbasins. Thrusting provides accommodation space for evaporites and also controls the water pathways into the desiccating basins. The intra-Messinian unconformity separating first and second cycle evaporites is a “type 1 sequence boundary” related to the forced regression associated with the acme of Mediterranean desiccation, an interpretation supported by local ravinement and incised valley fills. The overlying second cycle evaporites are a combination of detrital, reworked first cycle material and primary gypsum formed under brackish water. Regional onlap relationships and bed continuity suggest that this water body was of regional extent with a systematically rising base level. These interpretations have several implications for Messinian correlations in the Mediterranean: The deep basin evaporites correlate with an intra-Messinian unconformity that separates the two cycles on Sicily and postdate the first cycle deposits; regional base level was largely restored before the end of the salinity crisis. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Analysis of NRM directions from the Rossello composite: implications for tectonic rotations of the Caltanissetta basin, Sicily

The paleomagnetic results of the Pliocene marine marls from the Rossello composite section [30] in the Caltanissetta basin of Sicily have been analysed to determine the amount and timing of tectonic rotations. The analysis shows that there is a consistent inclination error for the NRM component, which is removed between 500 and 600°C, which may be caused by compaction of the sediment. Differences in inclination error throughout the composite section are related to differing carbonate content, a higher carbonate content implying less compaction and smaller inclination error. Furthermore, consistent differences are found between directions of normal and reversed polarities as well as between directions of the lower and upper part of the composite section. These differences are to a large extent related to differences in carbonate content, porosity and influence of weathering. The Caltanissetta basin shows a total clockwise rotation of 34° occurring since the early Pliocene. The magnetostratigraphy of the Rossello composite section shows that from the Miocene/Pliocene boundary (5.2 Ma) up to the Gilbert/Gauss boundary (3.6 Ma) there were no tectonic rotations of the Caltanissetta basin. Further, we speculate that 10° of this total clockwise rotation occurred during approximately Kaena times (ca. 3.05 Ma), and that at least 24° of this clockwise rotation is younger than the Gauss/Matuyama boundary (2.6 Ma).

Flexural tectonics of southeastern sicily

An inverse elastic flexural model for foreland basins has been developed and applied to southeastern Sicily. The model employs a non-linear least squares technique to determine the best values for the flexural parameters based on geological and geophysical data, thus avoiding the trial and error approach to parameter determination inherent in forward models. The lithosphere is assumed to act as an elastic plate of finite lenght ( L) and constant flexural rigidity ( D). The plate is anchored at one end in cantilever fashion. Four boundary conditions are necessary for solution of the governing flexural equation: at the fixed end the displacement is zero and the dip angle of the plate is π; on the free end the bending moment is M and the applied load is V. Thus, the plate profile is determined by five parameters, D, L, π, M and V. The model allows for differential lateral loading along the plate, a significant improvement over previous models which assume that the thrust/sediment load is applied at one point at the end of the plate. Sensitivity analysis of parameter determination and uncertainty are also discussed. Cross sections from southeastern Sicily are modeled and in every case the average difference between predicted and observed values is less than 6% of the maximum relief of the basin. The close fits indicate that the subsidence in the region is largely due to elastic flexure of the basement in response to thrust and sediment loading. The results support the contention that two separate basins have developed independently in the region: the Caltanissetta basin, a foredeep depression, and the Ragusa basin, a marginal sag basin. Parameter sensitivity analysis indicates that these two basins have evolved by different tectonic mechanisms. The foredeep is a dominantly flexural basin, while the Ragusa basin has a strong component of isostatic subsidence. In addition, the parameter values and sensitivity patterns are consistent with independent geological information from the region.

The sedimentology and development of Terravecchia Formation carbonates (Upper Miocene) of North Central Sicily: Possible eustatic influence on facies development

On at least two occasions during the Late Tortonian, siliciclastic deposition ceased and carbonates accumulated at the northern margin of the “Caltanissetta Basin” in north-central Sicily. Bioclastics dominated in the shallower proximal areas, while coral reef facies developed where shallow-water sand and cobble substrates existed or where sea-floor highs has created local shallows. The genetic model proposed is that siliciclastic deposition was repeatedly terminated during the Late Tortonian by rises in sea level which transgressed fluviatile and deltaic environments. Carbonate deposition was widespread, but, later erosion and reworking removed much of the sediments except within abandoned delta distributary channels and minor sea-floor depressions. Reef developments, associated with channel mouths and the shelf slope break, have been preserved in situ, whereas channels in more proximal locations are filled with siliciclastic, bioclastic and intraclastic rubble from elsewhere on the delta top. The wide lateral extent of the truncated tops of the carbonate beds argues for eustatic, rather than tectonic controls of erosion and subsequent reworking. These events may be closely related in time to other recorded Late Tortonian eustatic events in the foreland zones, such as the Hyblean Plateau and the Maltese Islands further south. Collectively they give some support to a model involving multiple eustatic fluctuations associated with the onset of the Messinian desiccation of the Mediterranean.

Marine planktic diatom correlation of lower Messinian deposits in the western Mediterranean

Samples from late Neogene Mediterranean outcrops were analysed for diatom content. The presence of certain species in the Tripoli Formation (Caltanissetta Basin, Sicily) and in the Beida Formation (Cheliff Basin, NW Algeria) permits correlation between these sections and the paleomagnetic reversal record. The occurrence of Thalassiosira praeconvexa, Thalassiosira miocenica, Thalassiosira convexa var. aspinosa and Asterolampra acutiloba indicates that the Tripoli and Beida formations were deposited over an interval ranging from the upper half of Paleomagnetic Epoch 6 into the lower half of Epoch 5 (5.6 to 5.9 Ma). Previous diatom correlations were too young. The occurrence of Nitzschia reinholdii and Asterolampra acutiloba in pre-evaporitic diatomites from the upper Turre Formation (SE Spanish Sorbas Basin) is used to place deposits at this site tentatively in Paleomagnetic Epoch 5 or 6.

Globorotalia truncatulinoides (d'Orbigny) in the Mediterranean Upper Pliocene Geologic Record

Globorotalia truncatulinoides (d'Orbigny) in the Mediterranean Upper Pliocene Geologic Record

Different styles of deformation in the calabrian arc (Southern Italy): Implications for a seismotectonic zoning

The most recent seismic profiles in southern Italy show the existence of a sudden thinning of the crust at the boundary between the chain and the Tyrrhenian margin. The abrupt change in thickness can be followed along a zone which has the same geometry in plan as the Calabrian arc. By considering these data and the gravimetric anomalies, it is possible to associate this crustal anomaly with a deep-seated shear zone which determines a crustal shortening of about 40–60 km which can only be a consequence of post-Tortonian tectonics. The surface equivalents of the deep-seated shear zone can be recognized, from north to south, in the alignment of the intra-Apenninic basins (Vallo di Diano, San Arcangelo, Potenza), in the Crati-Mesima graben and in the Mount Kumeta-Alcantara fault zone. The distribution of the seismicity and its connection with the surface structures shows that the largest earthquakes occur along the deep shear-zone. In particular, shocks with the highest magnitude and the longest recurrence intervals are located in those areas where the deep shear zone is at an angle of about 90° with the direction of maximum shortening (Crati-Mesima graben). The fault zones nearly parallel to the regional compression axis (e.g., Mount Kumeta-Alcantara fault zone) are characterized by earthquakes of lower magnitude. Taking into account the neotectonic evolution of the regional structures, as well as the orientation of the stress field and its connection with the deep-seated shear zone, it is possible to distinguish the following seismotectonic zones: Upper Crati-Mesima graben, transverse throughs, Mount Pollino-Mount Raparo fault zone, external Ionian area, San Arcangelo basin-zone of the external flysch, Sicani Mountains, Mount Kumeta-Alcantara fault zone, Caltanissetta basin, and Iblean plateau-Bradanic trough-Murge ridge. The definition of the geometry of the shear zone at depth is one of the most important, but still unresolved problems.