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1.
Mauro Aldinucci Anna Gandin Fabio Sandrelli 《International Journal of Earth Sciences》2008,97(6):1247-1269
In the Alpine-Mediterranean region, the continental redbeds and shallow-marine siliciclastics related to the early depositional
phases of the Late Permian-Mesozoic continental rifting are referred to as the most common representative of the “Verrucano
tectofacies”. The Verrucano-type successions exposed in southern Tuscany are diachronous, spanning from Triassic to earliest
Jurassic in age, and accumulated within the Tuscan domain, a paleogeographic region of continental crust that due to the opening
of the Piedmont–Ligurian ocean formed part of the Adria passive-margin. They belong to the metamorphic Verrucano Group and
the non-metamorphic Pseudoverrucano fm. Viewed overall, these Verrucano-type successions appear to manifest five episodes
or pulses of an ongoing continental rifting. With the exception of the first episode that developed entirely within a terrestrial
setting, each one is represented by basal Verrucano-type continental siliciclastics overlain by compositionally mixed marine
deposits, which resulted from four diachronous, post-Middle Triassic transgressions. This suite of tectonic pulses produced
the progressive westward widening (backstepping) of the Tuscan domain in the rifting south-Tuscany area. 相似文献
2.
Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin 总被引:1,自引:1,他引:0
Hans-Jürgen Gawlick Wolfgang Frisch Lirim Hoxha Paulian Dumitrica Leopold Krystyn Richard Lein Sigrid Missoni Felix Schlagintweit 《International Journal of Earth Sciences》2008,97(4):865-881
The Mirdita Ophiolite Zone in Albania is associated with widespread mélanges containing components of up to nappe-size. We
dated matrix and components of the mélange by radiolarians, conodonts, and other taxa. The components consist of radiolarites,
pelagic limestones and shallow-water limestones, all of Triassic age, as well as ophiolites. Triassic radiolarite as a primary
cover of ophiolite material proves Middle Triassic onset of Mirdita ocean-floor formation. The mélange contains a turbiditic
radiolarite-rich matrix (“radiolaritic flysch”), dated as Late Bajocian to Early Oxfordian. It formed as a synorogenic sediment
during west-directed thrusting of ophiolite and sediment-cover nappes representing ocean floor and underplated fragments of
the western continental margin. The tectonic structures formed during these orogenic events (“Younger Kimmeridian or Eohellenic
Orogeny”) are sealed by Late Jurassic platform carbonates. The geological history conforms with that of the Inner Dinarides
and adjoining areas; we therefore correlate the Mirdita-Pindos Ophiolite Zone with the Vardar Zone and explain its present
position by far-distance west-directed thrusting. 相似文献
3.
ABSTRACT New radiolarian biostratigraphical data have shed light on the Mesozoic tectonic evolution of South-Tethys in the Baer–Bassit region of NW Syria. Radiolarian assemblages of Late Triassic, Middle Jurassic and Early Cretaceous age were extracted from radiolarites in five measured sections. The results are compared with published radiolarian ages from the Mamonia Complex, western Cyprus. These two areas are interpreted as preserved fragments of the conjugate margins of a small South Tethyan oceanic basin formed by Triassic rifting. In the southerly (i.e. Arabian) margin, proximal successions were dominated by shallow-water-derived carbonate, whereas distal successions reveal seamount-type alkaline/peralkaline volcanism, dated as both Late Triassic and Middle Jurassic–Early Cretaceous. Along the inferred northern margin (i.e. western Cyprus) proximal successions are dominantly terrigenous, whereas distal settings include Late Triassic oceanic crust and seamount-type lavas. 相似文献
4.
《Cretaceous Research》2012,33(6):685-699
Albian pelagic successions of the Nebeur area in northwestern Tunisia consist of radiolarian-bearing and organic-rich black shale beds, which represent the lower part of the Fahdene Formation. The carbonate content of the organic-rich beds ranges between 40 and 48%. Total organic carbon (TOC) analyses via Rock Eval pyrolysis yielded values ranging between 0.7 and 2.8% and a mixed marine/terrestrial origin. Tmax values vary between 424 and 450 °C, indicative of submature to mature organic matter. High resolution planktic foraminiferal and radiolarian biostratigraphy suggest that the black shales beds span the mid- to late Albian, confined to the middle part of the Ticinella primula zone, upper Biticinella breggiensis zone and lower appeninica + buxtorfi zone. Episodes of organic-rich deposition in the “Tunisian Trough” are interpreted as being the sedimentary record of the global oceanic anoxic events OAE1b, c, and d respectively. Age-diagnostic radiolarian assemblages recovered from late Albian organic-rich black shales lie within the UA13–UA14 boundary biochronozones. The abundance of radiolarian and calcispheres (i.e. pithonella) within the black shales suggests high productivity periods and eutrophic conditions probably triggered by upwelling currents. 相似文献
5.
The Lagonegro Units are a part of the southern Apennines orogenic wedge. The age of the Lagonegro successions ranges from lower–middle Triassic to Oligo-Miocene. During late Cretaceous and Oligocene the deposition of calcareous-clastic sediments occurred interbedded with shales (Flysch Rosso Fm). During Oligocene and early Miocene, in the Mediterranean area, an important variation of the tectonic regime occurred, and siliciclastic sediments of the Numidian Basin unconformably lay on the Meso-Cenozoic units of the Lagonegro Basin. In the Lucanian Apennine, the Aquitanian–Langhian Numidian Flysch Fm overlies the Flysch rosso Fm. The shales of the Flysch rosso Fm have a peculiar geochemical fingerprint relative to typical shales of post-Archean age. The abundance of Ni and Cr is significantly higher and the HREE chondrite-normalized patterns are steep with a (Gd/Yb)ch>2. A supply of material from the African Archean terranes could be the cause. The palaeo-weathering indices record changes at the source, reflecting variations in the tectonic regime. The oldest samples are derived from an environment in which steady-state weathering conditions prevailed, whereas the youngest samples are related to non-steady-state weathering conditions. This difference could record deformational events that affected the Mediterranean area during the Oligocene and early Miocene. The sample at the top of the studied log has very high silica content and an abundant coarse grain-sized fraction. This suggests that this sample belongs to the Numidian Flysch Fm. The geochemical proxies of this sample are different from those associated with samples from the Flysch rosso Fm, indicating that the source-area of the Numidian Flysch Fm did not include the Archean terranes. 相似文献
6.
Antonio Funedda 《International Journal of Earth Sciences》2009,98(7):1625-1642
In the Variscan foreland of SW-Sardinia (Western Mediterranean sea), close to the leading edge of the nappe zone, nappe emplacement
caused folding and repetition of stratigraphic successions, km-scale offset of stratigraphic boundaries and an extensive brittle-ductile
shear zone. Thrusts assumed a significant role, accommodating a progressive change of shortening direction and forming complicated
thrust triangle zones. During thrust emplacement of the nappes, strong penetrative deformation affected rocks beneath the
basal thrust of the nappe stack and produced coeval structures with both foreland-directed and hinterland-directed (backthrusting)
shear sense. Cross-cutting and overprinting relationships clearly show that the shortening direction changed progressively
from N–S to E–W, producing in sequence: (1) E–W trending open folds contemporaneous with early nappe emplacement in the nearby
nappe zone; (2) recumbent, quasi-isoclinal folds with axial plane foliation and widespread, “top-towards-the-SW”, penetrative
shearing; (3) N–S trending folds with axial plane foliation, contemporaneous with late nappe emplacement; (4) backthrusts
and related asymmetrical folds developed during the final stages of shortening, postdating foreland-verging structures. Structures
at (3) and (4) occurred during the same tectonic transport “top-towards-the-E” of the nappe zone over the foreland. The several
generations of folds, thrusts, and foliations with different orientations developed, result in a complex finite structural
architecture, not completely explicable by the theoretical model proposed up to date. 相似文献
7.
Geochemistry and geodynamic implications of the Triassic bimodal magmatism from Western Kunlun Orogen,northwest China 总被引:1,自引:0,他引:1
The Western Kunlun Orogen occupies a key tectonic position at the junction between the Tarim block and the Tethyan domain.
However, the late Paleozoic to early Mesozoic, especially the middle to late Triassic tectonic evolution history of the Western
Kunlun Orogen remains controversial. This study reports SHRIMP zircon U–Pb ages and geochemical as well as Sr–Nd–Hf isotopic
data for middle to late Triassic Taer pluton in Western Kunlun Orogen, Northwest China. The Taer pluton shows a strong bimodal
distribution of compositions, with the felsic rocks dominant and the mafic rocks subordinate. Zircon U–Pb dating reveals that
the coexisting mafic and felsic rocks are coeval, both emplacing in a period between 234 and 225 Ma. Most of the studied rocks
are potassium rich and can be classified into high-K calc-alkaline to shoshonitic series. They are also strongly enriched
in LREE, LILE and depleted in HFSE with strong negative Ti and Nb anomalies, and characterized by enriched Sr–Nd–Hf isotopic
signatures. Detailed geochemical and isotopic studies indicate that the Taer pluton was emplaced in a post-collisional extensional
setting, with the mafic rocks derived from partial melting of the enriched continental lithospheric mantle in the spinel facies
field, and the felsic rocks formed by anatexis of newly underplated basaltic rocks. The existence of middle to late Triassic
post-collisional magmas in Western Kunlun region suggests that the final closure of Paleo-Tethys and the initial collision
between the Western Kunlun and the Qiangtang terranes may have happened before ~234 Ma, most probably in late Permian, rather
than in late Triassic or early Jurassic. In assistance with other geological evidences, such as the presence of early Triassic
to late Triassic/early Jurassic S-type magmatism, terrestrial molasse depositions, regional unconformities, and strong deformation,
we propose that the Western Kunlun Orogen may have undergone a long post-collisional intracontinental process from early Triassic
to late Triassic/early Jurassic. 相似文献
8.
Mabrouk Boughdiri Houaïda Sallouhi Kamel Malaoui Mohamed Soussi Fabrice Cordey 《Comptes Rendus Geoscience》2006,338(16):1250-1259
The analysis of calpionellid associations from jebels Amar and Jédidi sections in North-Atlasic Tunisia provides, for the first time, a precise biozonation of the Jurassic–Cretaceous transition succession. In the light of the new data obtained and considering recently published results, the age of Upper Jurassic formations is clarified, allowing correlations with the Tunisian ‘Dorsale’ and the North–South Axis successions. Within the Maghrebides' range, sections from the external zones correlated to the Tunisian successions are quite distinctive from their equivalent in the internal zones. Both have evolved in different palaeogeographic domains related to the early structuration of the northwestern and southwestern Tethys margins. To cite this article: M. Boughdiri et al., C. R. Geoscience 338 (2006). 相似文献
9.
《Geodinamica Acta》2013,26(3):131-138
Radiolarians of Middle Jurassic age (tentatively middle Bathonian) provide the first direct age determination from oceanic sediments associated with the Chenaillet-Montgenèvre ophiolite (Piemonte zone, French-Italian Alps). This datum obtained from radiolarites of the Lago Nero- Replatte thrust sheet is older than those previously established on ophiolite sedimentary covers from this segment of the western Alps. It also shows that Lago Nero-Replatte basal radiolarites are anterior to the youngest intrusives from the overlying Chenaillet s.s. thrust sheet. This chronological relationship implies either a late seafloor spreading-related magmatic activity in places younger than adjacent initial pelagic sedimentation, or more likely that the Lago Nero-Replatte and the Chenaillet s.s. thrust sheets are distinct and distant pieces of lithosphere that were eventually stacked together: the Lago Nero-Replatte unit was trapped within the accretionary wedge while the Chenaillet s.s., of a younger age and in a more distal position with regards to the European margin, was obducted. Regionally, the Lago Nero-Replatte sediments appear to be coeval to other Bathonian supraophiolitic radiolarites exposed in the western Alps. These results strengthen the Bathonian correlation of widespread seafloor spreading in both western Tethys and the central Atlantic ocean. 相似文献
10.
Vladimir Cermak Jan Safanda Louise Bodri 《International Journal of Earth Sciences》2010,99(6):1437-1451
Observational evidence proved that even when a borehole is in “fully” stabilized conditions, temperature data may exhibit
certain unrest resembling irregular oscillations in the order of hundredths or (in the extreme case) even tenths of degree.
Temperature was monitored in complicated hydrogeological conditions in the Yaxcopoil-1 hole (Chicxulub impact structure, Mexico).
Two experiments are reported: (a) 20-day monitoring when a logger was located in the center of the high temperature gradient
anomaly produced by the cold wave slowly propagating downwards and (b) simultaneous three-loggers 18-day monitoring with loggers
located above, in and below the anomaly. All observed temperature–time series displayed intermittent oscillations of temperature
with sharp gradients and large fluctuations over all observed time scales. While the “upper” and “lower” records revealed
quasi-periodic temperature variations, the “central” record shows fast temperature oscillations with strong up-and-down reversals,
all with amplitudes up to a few tenths of degree. The observed temperature–time series were processed by recurrence and recurrence
interval quantification as well as by spectral analyses. It is shown that fluid in a borehole, subject to thermal gradient,
is stable, as far as the gradient remains below a certain critical value. At higher Rayleigh numbers, the periodic character
of oscillations typical for “quiescent” regime is superseded by stochastic features. This “oscillatory” convection occurs
due to instability of the horizontal boundary layers. In the specific case of the Yaxcopoil hole, the time series above and
below the cold wave (characterized by relatively lower temperature gradients between 20 and 50 mK/m) contain a clear low frequency
component produced by tidal forcing. This component dominates over the high frequency domain (periods from 10–15 to 1 min),
which exhibit a scaling behavior. This pattern conspicuously changes in the center part of the cold wave, where the local
temperature gradient exceeds 200 mK/m and where tidal forcing composes only ~3% of the signal. 相似文献
11.
12.
Summary ?Results of experimental investigations in the dry system PtS-PdS-NiS at 1100°C, 1000°C, and 900°C are presented. The phases
observed at 1100°C are “cooperite” and a melt, at 1000°C “cooperite”, “braggite”, and a melt and at 900°C “cooperite”, “braggite”,
“vysotskite”, Ni1−xS, and a melt. At 1100°C the maximum solubility of Ni in ideal, Pd-free “cooperite” is 2.7 atomic per cent and the Pd-content
limit in Ni-free “cooperite” is 12.8 atomic per cent. At 1000°C the maximum solubility of Ni in ideal, Pd-free “cooperite”
is 3.3 atomic per cent and the Pd-content in Ni-free “cooperite” is 13.7 atomic per cent. The “braggite” composition ranges
from Pt0.56Pd0.38Ni0.06S and Pt0.59Pd0.41S in a Ni-saturated and Ni-free environment respectively to Pt0.18Pd0.80Ni0.02S and Pt0.14Pd0.86S respectively. At 900°C the maximum Ni-content in ideal Pd-free “cooperite” is 3.1 atomic per cent and the Pd-limit in Ni-free
“cooperite” is 12.5 atomic per cent. The “braggite” composition ranges from Pt0.59Pd0.29Ni0.12S and Pt0.60Pd0.40S for a Ni-saturated and Ni-free environment respectively, to Pd0.91Ni0.09S and PdS respectively. The Ni-content in “braggite” and “vysotskite” increases slightly with increasing Pt/Pd ratios and
is higher at 900°C than at 1000°C. Comparison of experimental trends with cooperite, braggite, and vysotskite analyses from
the literature implies high temperatures of formation for Pt-Pd-Ni sulphides in placers if Ni-saturation is assumed.
Received October 1, 1998;/revised version accepted September 7, 1999 相似文献
Zusammenfassung ?Synthetischer ,,Cooperit”, ,,Braggit” und “Vysotskit” im System PtS-PdS-NiS bei 1100°C, 1000°C und 900°C Ergebnisse experimenteller Untersuchungen im trockenen System PtS-PdS-NiS bei 1100°C, 1000°C und 900°C werden dargestellt. Bei 1100°C sind die Phasen “Cooperit” und Schmelze, bei 1000°C “Cooperit”, “Braggit” und Schmelze und bei 900°C “Cooperit”, “Braggit”, “Vysotskit”, Ni1−xS und Schmelze stabil. Bei 1100°C ist die maximale L?slichkeit von Ni in idealem, Pd-freiem “Cooperit” 2.7 Atomprozent und der Pd-Gehalt in Ni-freien “Cooperit” liegt bei maximal 12.8 Atomprozent. Bei 1000°C ist die maximale L?slichkeit von Ni in idealem, Pd-freien “Cooperit” 3.3 Atomprozent und der Pd-Gehalt in Ni-freien “Cooperit” liegt bei maximal 13.7 Atomprozent. Die Zusammensetzung des “Braggits” variiert zwischen Pt0.56Pd0.38Ni0.06S und Pt0.18Pd0.80Ni0.02S in einem Ni-ges?ttigtem und zwischen Pt0.59Pd0.41S und Pt0.14Pd0.86S in einem Ni-freien Umfeld. Bei 900°C liegt die maximale L?slichkeit von Ni in idealem Pd-freien “Cooperit” bei 3.1 Atomprozent und der Pd-Gehalt in Ni-freien “Cooperit” liegt bei maximal 12.5 Atomprozent. Die Zusammensetzung des “Braggits” variiert zwischen Pt0.59Pd0.29Ni0.12S und Pd0.89Ni0.08S in einem Ni-ges?ttigten und zwischen Pt0.59Pd0.40S und PdS in einem Ni-freien Umfeld. Der Nickelgehalt in “Braggit” und “Vysotskit” nimmt mit zunehmendem Pt/Pd Verh?ltnis zu und ist bei 900°C h?her als bei 1000°C. Ein Vergleich der experimentellen Trends mit Cooperit, Braggit und Vysotskit Analysen aus der Literatur weist auf eine Hochtemperaturbildung der Pt-Pd-Ni Sulfide in Seifenlagerst?tten hin, wenn man von Nickels?ttigung ausgeht.
Received October 1, 1998;/revised version accepted September 7, 1999 相似文献
13.
Shumei XU Shikui ZHAI Aibin ZHANG Huaijing ZHANG Haijian LU 《Frontiers of Earth Science》2008,2(1):10-16
The grain size and element (including redox sensitive elements and terrigenous elements) concentration of surface sediments
from the Changjiang Estuary hypoxia zone and its adjacent sea area were measured in this research. Based on the obtained data,
the hypoxic environment’s influence on the distribution of elements in surface sediments was further studied. We believe that
the “redox environment effect” greatly influences the distribution of the RSE, which reveals the “patchy enrichment pattern”
offshore in the hypoxia zone, while the distribution of the terrigenous elements which shows the “stripped enrichment pattern”
near shore is mainly affected by “granularity effects”. Due to the existence of the hypoxia zone of the Changjiang Estuary,
the distribution of the RSE such as Mo, Cd and V in the study area exhibits the characteristics of “redox environment effects”.
__________
Translated from Marine Geology & Quaternary Geology, 2007, 27(3):1–8 [译自: 海洋地质与第四纪地质] 相似文献
14.
Summary A continuous, but attenuated section through orogenic lower and middle crust overthrust by a second lower-crustal complex
was distinguished at the eastern margin of the Bohemian Massif. This indicates the existence of two lower-crustal “autochthonous”
extrusions into middle crust that is not compatible with the model of “allochthonous” lower crustal klippen remaining after
flat thrusting of the Gf?hl nappe over large distances. The base of the lower crust is represented by a granulite body exhumed
from c. 15 kbar and 800 °C. A hangingwall complex of layered amphibolites gradually passes into amphibolite bearing paragneisses
(the Monotonous unit) and micaschists intercalated with marbles at the top (the Varied unit). The metamorphic grade and anatexis
decreases upwards and the micaschists preserve a prograde path to c. 8 kbar and 700 °C. This sequence is overthrust by a second
lower crustal strongly migmatitized complex, referred to as the Raabs complex, which is marked by an eclogite-bearing belt
at the base. The garnet zoning of eclogite indicates burial from 10 kbar to min. 15 kbar. In all units, relics of a steep
metamorphic fabric were identified, reworked by folding and a moderately west-dipping foliation. The conditions of 7–10 kbar
and approximately 750 °C for the flat foliation were obtained in all units indicating that exhumation of the lower crust into
a middle crustal level occurred earlier, probably during the development of steep fabrics. The intense flat fabric is interpreted
as a result of thrusting of the whole assembly over the middle crustal Brunian indentor. 相似文献
15.
Hualing Wei Nianqiao Fang Xuan Ding Lanshi Nie Xiuming Liu 《Frontiers of Earth Science》2008,2(2):162-169
This paper presents pelagic records of planktic foraminifera, as well as data of stable isotope stratigraphy and carbonate
stratigraphy since 3.5 Ma B.P. from site ODP758 in the Ninetyeast Ridge of the Indian Ocean. Based on these data, manifestations
and related mechanisms of major tectonic and environmental events such as the rapid uplift of the Himalaya Mountains, “middle
Pleistocene climatic transition” and “mid-Brunhes dissolution event” in the region are discussed. According to the analysis
and comparison of various indices and changes in terms of foraminifera assemblage, paleotemperature, paleosalinity and themocline
from site ODP758, the authors deduce that the paleoclimatic changes might correlate with the mid-Pleistocene transition at
1.4–1.7 Ma B.P. The changes of CaCO3, mass accumulation rates (MAR) of CaCO3 and non- CaCO3 MAR indicate that the loaded terrigenous sediments increased at 1.7 Ma, which is in agreement with the uplift history of
the Qinghai-Tibet plateau as shown by the available data. The last two changes coincide with the uplift of the Qinghai-Tibet
plateau, hence they are called “Qinghai-Tibet movement” (1.7 Ma), and the “Kunlun-Yellow River movement” (1.2–0.6 Ma). The
changes of the CaCO3 content, coarse fraction (> 150 μm) content and planktonic foraminifera biostratigraphy show that strong dissolution of abyssal
CaCO3 occurred in the study region during 0.5–0.4 Ma. The event was consistent with the “mid-Brunhes dissolution event” in the
sedimentary records of the Atlantic Ocean, Pacific Ocean, Indian Ocean and Nansha sea area of the South China Sea.
__________
Translated from Geological Bulletin of China, 2007, 26(12): 1627–1632 [译自: 地质通报] 相似文献
16.
17.
Vladimir Cermak Louise Bodri Jan Safanda 《International Journal of Earth Sciences》2008,97(2):375-384
In the previous part of this work (Cermak, Safanda and Bodri, this volume p.MMM) we have described experimental data and quantified
the heterogeneity features of the microtemperature time series. The spectral analysis and the local growth of the second moment
technique revealed scaling structure of all observed time series generally similar and suggested the presence of two temperature
forming processes. The longer-scale part can be attributed to the heat conduction in compositional and structural heterogeneous
solid rocks, further affected by various local conditions. Short-scale temperature oscillations are produced by the intra-hole
fluid convection due to inherent instability of water column filling the hole. Here we present how the observational evidence
is supported by the results of the computer simulations. The exact modes of intra-hole convection may be different, ranging
from quasi-periodic (“quiescent”) state to close of turbulence. As demonstrated by numerical modeling and referred on laboratory
experiments, at higher Rayleigh numbers the periodic character of oscillation characteristic for “quiescent” regime is superseded
by stochastic features. This so called “oscillatory” convection occurs due to instability within the horizontal boundary layers
between the individual convectional cells. In spite of the fact that the basic convective cell motion is maintained and convection
is characterized by slow motion, the oscillatory intra-hole flow and corresponding temperature patterns exhibit typical features
of turbulence. The idea of boundary layer instability as a source of stochastic temperature fluctuations could explain many
distinct features of borehole temperatures that previously cannot be interpreted. 相似文献
18.
Tamás Mikes Björn Baresel Andreas Kronz Dirk Frei István Dunkl Raimon Tolosana‐Delgado Hilmar Von Eynatten 《地学学报》2009,21(6):495-506
Three independent single‐grain geochronometers applied to detrital minerals from Central Dinaride sediments constrain the timing of felsic magmatism that associated the Jurassic evolution of the Neotethys. The Lower Cretaceous clastic wedge of the Bosnian Flysch, sourced from the Dinaride ophiolitic thrust complex, yields magmatic monazite and zircon grains with dominant age components of 164 ± 3 and 152 ± 10 Ma respectively. A unique tephra horizon within the Adriatic Carbonate Platform was dated at 148 ± 11 Ma by apatite fission track analysis. These consistent results suggest that leucocractic melt generation in the Central Dinaride segment of the Neotethys culminated in Middle to Late Jurassic times, coeval with and slightly post‐dating subophiolitic sole metamorphism. Growth of magmatic monazite and explosive volcanism call for supra‐subduction‐zone processes at the convergent Neotethyan margin. New compilation of geochronological data demonstrates that such Jurassic felsic rocks are widespread in the entire Dinaride–Hellenide orogen. 相似文献
19.
Tunisian Chott’s region is one of the most productive artesian basins in Tunisia. It is located in the southwestern part of
the country, and its groundwater resources are developed for water supply and irrigation. The chemical composition of the
water is strongly influenced by the interaction with the basinal sediments and by hydrologic characteristics such as the flow
pattern and time of residence. The system is composed of an upper unconfined “Plio-Quaternary” aquifer with a varying thickness
of 20–200 m, an intermediate confined/unconfined “Complex Terminal” aquifer about 100 m in thickness and a deeper “Continental
Intercalaire” aquifer about 150 m in thickness separated by thick clay and marl layers. The dissolution of evaporites and
carbonates explains part of the contained Na+, Ca2+, Mg2+, K+, SO42− and Cl-, but other processes, such carbonate precipitation, also contributes to the water composition. The stable isotope composition
of waters establishes that the deep groundwater (depleted as compared to present corresponding local rainfall) is ancient
water recharged probably during the late Pleistocene and the early Holocene periods. The relatively recent water in the Plio-Quaternary
aquifer is composed of mixed waters resulting presumably from upward leakage from the deeper groundwater. 相似文献
20.
Habib Belayouni Francesco Guerrera Manuel Martín-Martín Francisco Serrano 《International Journal of Earth Sciences》2013,102(3):831-855
The Numidian and Post-Numidian stratigraphy of the Tunisian Tell has been updated based on 16 stratigraphic sections belonging to the Massylian sub-domain of the Maghrebian Flysch Basin and to the External Domain. The new data concern detailed litho- and biostratigraphy, gaps, synchronous marker levels, lateral correlations, tectonic contacts, etc. The successions studied show many diachronous and unconformity boundaries delimiting sedimentary depositional sequences related to some tectonic/sedimentary processes. Two main Miocene sedimentary successions (Numidian and Post-Numidian) are recognized overlying the Sub-Numidian Succession (pre-Early Aquitanian) by new integrated (planktonic foraminifera and calcareous nannoplankton) chronostratigraphic analyses, allowing an update of the formations studied. The Miocene tectonic/sedimentary relationships and the timing of the deformation are summarized as follows: (1) the activation of a foredeep stage and a tectogenesis phase gives rise to an accretionary orogenic wedge during mainly the Early Miocene; (2) a late-orogenic phase is checked in the Late Burdigalian-Early Langhian characterized by a marine glauconitic terrigenous sedimentation; (3) a post-orogenic generalized phase is confirmed from the Middle Miocene on in shallow marine or continental sedimentation. These results show good correlation along the Maghrebian Chain and Betic Cordillera. Finally, a paleogeographic and geodynamic evolutionary model concerning the Miocene African Tunisian Margin is postulated. 相似文献