Research program
Integrated methodologies (organic matter dispersed in sediments, fluid inclusions, clay mineralogy and geochemistry, fission tracks and U-Th/He ages) to unravel the tectonic/sedimentary burial and exhumation in the southern Apennines (Calabria-Lucania border) and eastern Sicily (sedimentary fold-and-thrust belt)
University Co-ordinator
Università degli Studi ROMA TRE -
SCIENZE GEOLOGICHE - ROMA(RM)
Research Unit Leader
Sveva CORRADO
Description
In Eastern Sicily, both contractional and extensional deformations migrate toward the foreland with comparable speed. That and the progressive regional uplift make of Eastern Sicily an ideal case history for this kind of analysis: studying the thermal evolution of the sedimentary basins constituting the backbone of an orogenic wedge in order to understand its geometry's evolution and geodynamic meaning. Reconstructing the chain's geometries prior to regional uplift is the key to this goal. Furthermore, given the kind of deposits (mainly siliciclastics) and depositional environments (pelagic, foredeep, and thrust-top basin) of outcropping units, the lithostratigraphic units are suitable to such an investigation. The analysis is carried out by an integrated study of maturity degree of the organic matter(o.m.)dispersed in sediments and clay mineralogy (c.m.); to a lesser extent, fluid inclusion analysis in quartz and calcite crystals and fission track analysis in apatite crystals are also useful. From this point of view, the research's final goals are summarized in the following two points:1) RECONSTRUCTION OF THERMAL EVOLUTION OF STRATIGRAPHIC/STRUCTURAL UNITS OUTCROPPING IN EASTERN SICILY, along the regional N-S transect betwen S. Agata di Militello and Ramacca (from Nebrodi Mts to the North, to Iblei Mts. to the South). The goal will be achieved by acquiring new o.m., c.m., and structural data in order to generate thermo-structural models. The data will be integrated with those (fission tracks and fluid inclusions) acquired by the Camerino Research Unit (R.U.). In particular, we want to investigate the thermal evolution of the chain's outcropping units discriminating between pure sedimentary and tectonic burial. This will allow the reconstruction of the presence of units now removed by erosion and/or tectonics and the speed of their removal.2) SYSTEMATIC COMPARISON BETWEEN DIFFERENT INVESTIGATING METHODOLOGIES in collaboration with the Camerino R.U., seldom applied in an integrated way in Italy until now. This will allow to check the used methods for validity and to refine the techniques employed in the reconstruction of the thermal history of the orogen's sedimentary portions.METHODOLOGIES1. OPTICAL ANALYSIS OF MATURITY OF O.M. DISPERSED IN SEDIMENTS: Classification (a), Vitrinite reflectance (b) e Thermal Alteration Index of palinomorphs (T.A.I.) (c).a) The o.m. dispersed in sediments transforms into kerogen within the first centimeters of depth (eogenesis). Several groups of macerals can be observed at the microscope in kerogen (vitrinites-huminites, inertinites and liptinites, in reflected light; phytoclasts, amorphous om, palynomorphs, zooclasts, in transmitted light); they will be classified during the research.b) Vitrinites-huminites are jellified degradation products of the lignin-cellulose portions of higher plants. Their thermal degradation leads to the irreversible variation of some chemical and physical properties; this variation causes the gradual increase of their reflective power (or reflectance: Ro%), providing a thermal maturity scale of o.m. well correlated to other indicators of thermal evolution in sediments and with hydrocarbon generation stages. Ro% measurements will be carried out by reflected-light optical microscope. For each sample, about one hundred measurements will be performed on non-altered fragments. The mean Ro% value is derived from the interpretation of measurement histograms. c) Thermal evolution of om also determines a variation of colour of some of its constituents, which will be assessed in transmitted light. For palinomorphs these changes are coded in a chromatic scale where five categories of increasing T.A.I. are observable; the scale correlates to Ro%. Usually, for each sample, nearly 50 specimens are analyzed from the most abundant group of palinomorphs. Each one is given a value by comparison with the reference standards. The sample's T.A.I. is obtained from the arithmetic mean.2. X-RAY DIFFRACTION ANALYSIS (XRD) OF CLAY PORTIONS OF SEDIMENTARY SUCCESSIONS.In siliciclastic sediments, clay minerals are the only phases to provide information on their thermo-baric history (diagenesis-anchizone-epizone). The following parameters can be used: the variation of crystallinity index of some phases, the b0 value, illite and chlorite crystal size distributions, the illite polytypes evaluation, and the changes in ratios between the pure phases constituting mixed layers.In particular, the R.U. will deal with: a) determination of compositional variation and percentage incidence of observed mixed layers (e.g, illite/smectite mixed layers), b) Illite and chlorite crystal size distribution, c) evaluation of illite polytypes a) illite/smectite mixed layers (I/S) among the others have been successfully used in petroleum exploration as indicators of thermal evolution of sediments.The detected transformations are irreversible under progressive burial and comply with the following scheme:di-smectite->disordered I/S mixed layers->ordered I/S mixed layers->illite->K-muscovite. In order to define those parameters, we propose a XRD investigation to be carried out on all samples focussing on: - whole rock - 2÷16 micron grain-size fraction- <2 micron grain-size fractionb) assessing the thickness of illite crystallites provides another independent parameter for the evaluation of thermal maturity of sediments. By decomposing the peak's profile, it is possible to distinguish the sediment's authigenic phase from the detritic one. This is essential for studying siliciclastic successions where the detritic phase can obliterate sedimentary and/or tectonic burial-induced transformations. In fact, the detritic phase could provide misleading information on paleotemperatures associated to conditions inherited from the past and not to the basin's burial history. Each sample will be analyzed by a XRD system in collaboration with the USGS at Boulder, Colorado. The analyses will concern:- whole rock- <2 micron grain-size fraction- <0.2 micron grain-size fractionc) the evaluation of illite polytype percentage (1Md-1M-2M1) is an additional parameter to distinguish a siliciclastic sediment's detritic and/or diagenetic portion; it also provides indications about the thermal evolution of sediments. 3. GEOLOGICAL SURVEY AND STRUCTURAL ANALYSIS along the boundaries between the main tectonic Units; mesoscale data from the Monte Judica area will be collected and elaborated. 4. MODELLING THE BURIAL AND THERMAL HISTORY OF OUTCROPPING SEDIMENTARY SUCCESSIONS.During the research, we will model the transect by means of BasinMod 1D (available at "Roma Tre" University), GET1 e SEbe3 (available in Agip). These software applications allow reconstructing the thermal and burial history on both undeformed basins and orogens, where thrust emplacement creates tectonic loads.The first step deals with the input of geologic data from sedimentary successions and their deformation history (age of formations and of deformation events; chemical and physical features of rocks, etc.). From burial curves we derive the thermal modelling, defining the system's boundary thermal conditions through time. The models are then calibrated using the sediments' thermal evolution indicators; this will allow to define: the time-space intervals where the sedimentary successions experienced definite temperatures, the thickness of the geological bodies that caused the tectonic loading, the rate at which they were removed by erosion or tectonics. 5. For FISSION TRACKS and FLUID INCLUSIONS methodologies see model B of Camerino R.U. RESEARCH PHASES AND TASKS OF RESEARCH UNIT PHASE 1. Critical review of literature and existing data. Expected duration: 1 month.PHASE 2. Sampling of sedimentary successions outcropping along the transect (about 130 samples for c.m. and 60 for o.m.). Collection of about 10 samples for the study of fluid inclusions in quartz and calcite and 4 samples for the study of fission tracks in apatite. The approximate number of samples and the type of analysis proposed for the different lithostratigraphic units is suggested by: the results of a preliminary analysis concerning the I/S mixed layer content and Ro% (the analysis was performed on nearly 30 samples during a previous research on CNR grants, in collaboration with the University of Catania); the quality of outcrops already partially visited; the total thickness of the successions. The northern sector of the transect is dominated by the Sicilide Complex Units. Within it, the uppermost structural unit is represented by the Cesarò Unit; it outcrops extensively on Nebrodi Mts. and is made of the Monte Soro Cretaceous Flysch (about 20 samples) overlain by a deep-sea pelitic succession (upper Argille Scagliose). Underneath this Unit lies the Troina-Tusa structural unit, whose bottom is made of Argille Scagliose from Upper Cretaceous-Eocene and of the Polizzi Fm. Furthermore, these formations have been mapped in a narrow band south of Mt. Judica's structure, which they overthrust in extreme allochthony (together with the Numidian Flysch they make up the Gela nappe). They will be sampled only for c.m. analyses (about 10 samples). In the northern sector, only the younger portions of the Troina-Trusa Unit outcrop: they are Oligo-Miocene formations like "Argille Varicolori" (Oligocene-Miocene p.p.) (about 10 samples for c.m.) and the Troina-Tusa Flysch (Lower Miocene; 10 samples), unconformably overlain by the thrust-top basin deposits of the Reitano Flysch (Burdigalian-Serravallian; about 5 samples).These deposits overthrust the Nicosia Unit, formed by "Argille Varicolori" (about 10 samples for c.m.) overlain by alternating dark shale and quatzarenites (Numidian Flysch, about 10 samples for c.m.). The Nicosia Unit tectonically overlies a Unit principally made of Numidian Flysch (Mt. Salici-Mt. Altesina Unit) formed by dark shale (Upper Oligocene.-Aquitanian; about 10 samples for c.m.) and Burdigalian-Langhian Numidian Flysch quartzarenites. To the south, the Monte Judica Unit develops; it is made of a Mesozoic-Tertiary basin succession (about 10 samples only in the Mufara Fm. and in the Triassic cherty Limestones) overlain by an Oligocene-Miocene succession of marly clays and glauconitic sandstones (about 10 samples for c.m.). In the Mt. Judica Unit we will also collect samples for the analysis of fluid inclusions in quartz and calcite vein systems that developed in the sedimentary Mesozoic succession (particularly in cherty Limestones and Radiolarites); the number of samples will not exceed 10; structural analysis will constrain the veins' formation and evolution. This investigation is necessary to support the o.m. and c.m. maturity data (which provide indications on maximum burial) with an independent temperature constraint; the constraint is related to the deformation history of this unit, which underwent remarkable translations and rotations during orogenesis.Tortonian-Pliocene siliciclastic sediments outcrop between Leonforte and Centuripe. They were deposited unconformably over units of the belt within satellite basins preserved in Regalbuto's synform. They are represented by the proximal facies of Terravecchia Fm. (Upper Tortonian; about 10 samples), by the Messinian evaporitic succession, and by the Trubi (Lower Pliocene; about 5 samples).We will collect a limited number of samples (max. 4) for fission track analysis in more internal sectors of the Sicilide domain (e.g., Mt. Soro Flysch, Troina Tusa Flysch), which, based on available thermal maturity data, shows thermal stages typical of the oil window (Ro%=0,6-0,8). Expected duration: 4 months. About 20% of the total budget will be spent for this phase. PHASE 3. Sample preparation, laboratory analyses, elaboration, interpretation, and correlation. a) Sample preparation (at the Laboratories of the Department of Geological Sciences, University of "Roma Tre": D.S.G.3)b) Optical analysis of o.m.: analysis of composition, evaluation of T.A.I., measurement of Ro (at the D.S.G.3 and School of Civil Engineering and Geosciences, University of Newcastle, which is collaborating since several years ago, allowing uncharged use of the microscopy laboratory) c) Diffractometric analysis of clays (at the D.S.G.3 and USGS of Boulder, Colorado, which is collaborating since several months ago, allowing uncharged use of the RDX system)d) Interpretations and correlations. Comparison and integration with data from the Camerino R.U.. Setting up of the BasinMod 1D, Get1, and Sebe3 models. First evaluation of the tectonic and sedimentary loads different portions of the transect underwent in the past. Expected duration: 12 months. About 55% of the total budget will be spent for this phase.PHASE 4. Elaboration of thermo-structural model evolution, geometric-kinematical re-interpretation of available geological sections and of data acquired during the preceding phases. Drawing of geometrically correct geological sections. Evaluation of tectonic and/or sedimentary loads experienced in the past. Comparison to available data and interpretations for the southern Apennine and Sicily. Informal workshop with researchers from various institutions, with experience in the regional and methodological topics dealt with in this research. Results' publication. Expected duration: 5 months. 23% of the total budget will be spent for this phase.PHASE 5. Collaboration with the Camerino R.U. In this phase we will performed o.m. analyses on max 20 samples, and will create the thermo-structural models of prominent sectors on the Calabria-Lucania border. This phase aims to verify the effectiveness of the proposed integrated methodology and to produce a joint regional synthesis concerning southern Apennine and Eastern Sicily. Expected duration: 2 months. 2% of the total budget will be spent for this phase.EXPECTED RESULTSExpected results for the Eastern Sicily transect are: - Analytic correlation outline of o.m. maturity, c.m., fission tracks, and fluid inclusions data from samples analyzed by the other R.U. - Burial diagrams and thermal history of the studied sedimentary successions.- Data distributions map, tectonic and sedimentary loads and exhumation rates maps. - Structural-geological sections (for considerable time spans) including the reconstruction of thickness evolution of tectonic and/or sedimentary loads, and analytical data on the studied successions' thermal evolution. - Methodological and, to a lesser extent, regional scientific publications on national and international journals.
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