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1.
Two distinct series of slumps deform the upper part of the sedimentary sequence along the continental margin of the Levant.
One series is found along the base of the continental slope, where it overlies the disrupted eastern edge of the Messinian
evaporites. The second series of slumps transects the continental margin from the shelf break to the Levant Basin. It seemed
that the two series were triggered by two unrelated, though contemporaneous, processes. The shore-parallel slumps were initiated
by basinwards flow of the Messinian salt, that carried along the overlying Plio-Quaternary sediments. Seawater that percolated
along the detachment faults dissolved the underlying salt to form distinctly disrupted structures. The slope-normal slumps
are located on top of large canyons that cut into the pre-Messinian sedimentary rocks. A layer of salt is found in the canyons,
and the Plio-Quaternary sediments were deposited on that layer. The slumps are bounded by large, NW-trending faults where
post-Messinian faulted offset was measured. We presume that the flow of the salt in the canyons also drives the slope-normal
slumps. Thus thin-skinned halokynetic processes generated the composite post-Tortonian structural patterns of the Levant margin.
The Phoenician Structures are a prime example of the collapse of a distal continental margin due to the dissolution of a massive
salt layer. 相似文献
2.
中国大陆是由多个小陆块经多期次离散碰撞拼合而成,而"小陆块是否能成大钾"一直是国内钾盐研究领域关注的科学问题。文章剖析了意大利西西里微陆块的典型海相钾盐矿床形成条件与机理,为中国小陆块成钾研究提供借鉴。在晚中新世墨西拿盐度危机(Messinian Salinity Crisis)最盛期(5.60~5.55 Ma),西西里岛的卡尔塔尼塞塔盆地聚集了高达2亿t的钾盐镁矾矿。通过对卡尔塔尼塞塔盆地钾盐矿的赋存地层格架、矿体特征、成矿模式和机理进行梳理和总结,指出该矿床呈层状赋存于地中海"再沉积下石膏组"的原生石盐岩中,形成于深水、分层的常年性盐湖环境;晚中新世中地中海碰撞挤压的构造活动导致卡尔塔尼塞塔盆地强烈挠曲下凹,形成多个次级成矿凹陷;次级凹陷接受海水的周期性补给;在墨西拿盐度危机最盛期,由于气候变冷变干、直布罗陀海峡关闭、海平面急剧下降,远离补给源的次级凹陷变得更加封闭,从而在5万年的极短时间内经强烈蒸发,聚集为大规模钾盐矿。西西里微陆块尽管陆块小、盆地小,但在满足封闭构造_干旱气候_充足物源三要素耦合的特定时期内,同样形成了大型钾盐矿床。因此,西西里微陆块的钾盐成矿实例证明海相小陆块同样具有形成大型钾矿床的潜力,这对中国海相小陆块汇聚区的找钾工作具有重要的借鉴意义。 相似文献
3.
The Bajo Segura basin (eastern Betic Cordillera) has one of the most complete late Miocene–early Pliocene marine records of the western Mediterranean. An updated planktonic foraminifer zonal scheme based on recent astronomically tuned biozones is presented for this interval, documenting a complete succession of biostratigraphic markers, from biozone MMi9 (earliest Tortonian) to MPl3 (latest early Pliocene), of likely significance for regional-scale correlation throughout the Mediterranean. The findings reveal a series of intrazonal events (some unreported until now in the Mediterranean Neogene basin), including the particularly interesting two influxes of the Globorotalia miotumida group during the Tortonian. These biostratigraphic findings are the basis for a framework of the major allostratigraphic units in the basin based on planktonic foraminifer event-stratigraphy: synthems Tortonian I, Tortonian II, Tortonian-Messinian I, Messinian II, and Pliocene. In addition, the timing of the main tectono-sedimentary and palaeogeographic events throughout the basin's evolution has been further constrained. Our results suggest that, at least in the Bajo Segura basin, the late-Messinian barren interval (non-distinctive zone) can be considered an ecobiostratigraphic zone (cenozone) characterized by dwarf fauna of planktonic foraminifera. Consequently, the Bajo Segura composite section can be regarded as a biostratigraphic reference section for Neogene basins in the Betic Cordillera and hence also in the Western Mediterranean. 相似文献
4.
We present for the first time a synthesis of the evidence of focused fluid flow in the Eastern Mediterranean, providing an updated record that includes recent and past occurrences through the last ca. 6 My of evolution of the basin. We do this by adding the interpretation of a previously unpublished regional 2D seismic dataset to the existing occurrences of focused fluid flow reported in the literature. Our interpretation shows a high number (141) of focused fluid flow features, which span the stratigraphic interval from late Miocene to Recent. Of these features, (82) are at the seabed, and (59) are buried. The previous published record is more difficult to quantify, but in comparison shows an overwhelming majority of seabed features, with only rare examples of buried features.The spectrum of the buried and seabed features covers pockmarks, pipes, mud volcanoes, clastic intrusions and collapse structures. Clustering of the fluid flow features is observed at different times in specific areas, including the Nile Cone, and the Levant, Herodotus, Cyprus and Latakia basins. With the buried record, we are able to highlight the evolution of the leakage points through time. Focused fluid flow venting has been occurring since the onset of the Messinian Salinity Crisis and the start of basinwide deposition of evaporites. We focus in particular on seismic indicators of leakage through evaporites, and of sub-evaporitic source for fluids and remobilised sediments. We also discuss the role of the evaporites as a seal to ascending fluids, and in which circumstances they can be breached.Fluids (and associated remobilised sediments) are sourced from different intervals, from the sub- and supra-evaporitic section, and possibly within the evaporites. Only a minor proportion of the fluid flow features are certainly sourced from below the Messinian evaporites, and most of them are located in the Nile-Levant-Eratosthenes areas. The few examples of pathways that are able to cross thick, undeformed and well preserved evaporites are typically correlated to overpressure release and hydrofracturing. This confirms that the evaporites do act regionally as a very good seal as expected, while fluids are able to cross the evaporites only in their most extreme expression, i.e. in near-lithostathic overpressure conditions. This is confirmed by our observations made in the Eastern Mediterranean, where in the presence of relatively undisturbed evaporites, cross-evaporite vertical fluid pathways are only observed at the high end of the flux-pressure range, and involve sediment remobilisation. Maps combining these different elements can be used to detect areas potentially more prone to breaching. 相似文献
5.
Rivers respond to a drop in their base level by incising the topography. The upstream propagation of an incision, as usually depicted by a knickpoint migration, is thought to depend on several parameters such as the drainage area, lithology, and the amplitude of the base level drop. We first investigate the case of the Messinian Salinity Crisis that was characterized by the extreme base level fall (1500 m) of the Mediterranean Sea at the end of the Miocene. The response of drainage areas of three orders of magnitude (103 to 106 km2) highlights the dominant role of the drainage area (with a square root relationship) in controlling the knickpoint migration after a base level fall. A compilation of mean rates of knickpoint propagation for time durations ranging from 102 to 107 years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river: first, wave trains linked to the release of the alluvial cover and then, wave trains related to the bedrock incision, which correspond to the real time response of rivers. Wave trains with very low retreat rates (long lived knickpoints > 1 My) rather correspond to the response time of regional landscape. 相似文献
6.
The Messinian succession of Tuscany (central Italy) contains three evaporitic units. Among the several exposed evaporitic lithofacies, only selenitic gypsum precipitated directly from evaporating brines. All the other facies, nodular microcrystalline gypsum, gypsarenites and gypsum laminites, despite their macroscopic differences, display the same petrographic textures, indicating that they are the product of dehydration of gypsum to give anhydrite which has been successively rehydrated to secondary gypsum. These secondary facies show an entire array of textures ranging from cloudy ameboid (xenotopic) with anhydrite relics, to idiotopic without anhydrite relics, that are here interpreted as a sequence of progressive stages of rehydration. The presence of completely hydrated petrofacies at the core of nodules which display a less hydrated rim suggests that these rocks have undergone at least two cycles of a dehydration–rehydration process. This interpretation is supported by the presence of satin spar veins that are replaced by microcrystalline gypsum. Satin spar itself is considered to be a by-product of anhydrite hydration. The first dehydration–rehydration event affected the entire gypsum deposit, producing a completely hydrated (idiotopic) facies together with satin spar veins; the second affected only veins, fractures and the rims of nodules, turning the first generation of satin spar and idiotopic gypsum into cloudy ameboid gypsum. Sedimentary structures typical of sabkha environments indicate for the youngest formation that the first dehydration and rehydration process occurred syndepositionally. The preservation of primary gypsum facies only at sites with condensed sections, indicate for the oldest two formations that the first dehydration event occurred upon burial. This event has been estimated to have occurred in the earliest Pliocene. After the Early Pliocene, dehydration was favored even at shallow depths, due to an increased heat flow related with the emplacement of local crustal magmatic bodies. Rehydration possibly occurred when these formations were uplifted and exposed to ground and/or meteoric water. The Volterra Basin has undergone alternating subsidence and uplift events, that can account for two dehydration–rehydration processes at least, also driven by alternating circulation, in the tectonic fractures, of fresh and salty water, the latter derived from dissolution of Messinian halite. 相似文献
7.
The Feos Formation of the Nijar Basin comprises sediments deposited during the final stage of the Messinian salinity crisis when the Mediterranean was almost totally isolated. Levels of soft‐sediment deformation structures occur in both conglomeratic alluvial sediments deposited close to faults and the hyposaline Lago Mare facies, a laminated and thin‐bedded succession of whitish chalky marls and intercalated sands alternating with non‐marine coastal plain deposits. Deformation structures in the coarse clastics include funnel‐shaped depressions filled with conglomerate, liquefaction dykes terminating downwards in gravel pockets, soft‐sediment mixing bodies, chaotic intervals and flame structures. Evidence for soft‐sediment deformation in the fine‐grained Lago Mare facies comprises syndepositional faulting and fault‐grading, sandstone dykes, mixed layers, slumping and sliding of sandstone beds, convolute bedding, and pillar and flame structures. The soft‐sediment deformed intervals resemble those ascribed elsewhere to seismic shaking. Moreover, the study area provides the appropriate conditions for the preservation of deformation structures induced by seismicity; such as location in a tectonically active area, variable sediment input to produce heterolithic deposits and an absence of bioturbation. The vertical distribution of soft‐sediment deformation implies frequent seismic shocks, underlining the importance of seismicity in the Betic region during the Late Messinian when the Nijar Basin became separated from the Sorbas Basin to the north. The presence of liquefied gravel injections in the marginal facies indicates strong earthquakes (M ≥ 7). The identification of at least four separate fissured levels within a single Lago Mare interval suggests a recurrence interval for large magnitude earthquakes of the order of millennia, assuming that the cyclicity of the alternating Lago Mare and continental intervals was precession‐controlled. This suggestion is consistent with the present‐day seismic activity in SE Spain. 相似文献
8.
Based on a new quantitative analysis of sidescan sonar data combined with coring, we propose a revised model for the origin
for Mediterranean Ridge mud volcanism. Image analysis techniques are used to produce a synthetic and objective map of recent
mud flows covering a 640 × 700 km2 area, which represents more than half of the entire Mediterranean Ridge mud belt. We identify 215 mud flows, extruded during
the last 37,000–60,000 years. This time period corresponds to the limit of penetration of the sonar, that we evaluate through
geoacoustic modeling of the backscattered signal returned by the mud breccia-hemipelagites contact, and calibrate by coring.
We show that during this period, at least 96% of the mud volume has been extruded at the Mediterranean Ridge-Hellenic backstop
contact, the remaining being scattered over the prism. We suggest that the source is a Messinian (5–6 Ma) mud reservoir that
remained close to the backstop contact, at variance with the classical transport-through-the-wedge model. A revised mud budget
indicates that steady-state input is not needed. We propose that the source layer was deposited in deep and narrow pre-Messinian
basins, sealed by Messinian evaporites, and finally inverted in post-Messinian times. Onset of motion of the Anatolia-Aegea
microplate in the Pliocene resulted in change from slow to fast convergence, triggering shear partitioning at the edges of
the backstop and basin inversion. Mud volcanism initiation is probably coeval with the latest events of this kinematic re-organization,
i.e. opening of the Corinth Gulf and activation of the Kephalonia fault around 1–2 Ma. 相似文献
9.
RAPHAËL BOURILLOT EMMANUELLE VENNIN JEAN‐MARIE ROUCHY CHRISTOPHE DURLET VINCENT ROMMEVAUX CHRISTOPHE KOLODKA FREDERIC KNAP 《Sedimentology》2010,57(2):477-512
The Sorbas Member is a late Messinian complex sedimentary system that formed immediately following deposition of the Messinian evaporites in the Sorbas Basin (South‐east Spain). This work describes the sequence architecture and facies organization of a continuous kilometre long, alluvial fan to open platform transect near the village of Cariatiz in the north‐east of the basin. The post‐evaporitic Cariatiz platform was a mixed carbonate‐siliciclastic system composed of four intermediate‐frequency, fifth‐order depositional sequences (Depositional Sequences 1 to 4) arranged in an overall prograding trend. The intense fracturing and brecciation of these deposits is attributed to the deformation and dissolution of an evaporite body measuring several tens of metres in thickness. The four sequences display significant spatial–temporal variability in both architecture and facies distribution, with two main phases: (i) Depositional Sequences 1 and 2 are ooid and oobioclastic dominated, and show normal marine faunas; and (ii) Depositional Sequences 3 and 4 show a higher siliciclastic contribution and are microbialite dominated. These important changes are interpreted as modifications of the primary controlling factors. Following an initial 70 m drowning, possibly linked to increased oceanic input, Depositional Sequences 1 to 3 were controlled mainly by eustatic variations and inherited topography; their progradation destabilized the evaporite body near the end of the Depositional Sequence 2 period. During the second phase, Depositional Sequences 3 and 4 recorded a progressive restriction of the Sorbas Basin related to a 30 to 40 m fall in water level that was driven mainly by regional factors. These regional factors were dissolution and gravity‐induced deformation of the evaporites and correlative evaporative fluid circulation associated with the contrasted arid/humid regional climate that, respectively, controlled sequence geometry and fluctuating water salinity which caused a microbialite bloom. 相似文献
10.
Correlations and sequence stratigraphic model for Messinian carbonate platforms of the western and central Mediterranean 总被引：1，自引：0，他引：1
Jean-Jacques?CornéeEmail author Jean-Paul?Saint Martin Gilles?Conesa Philippe?Münch Jean-Pierre?André Simona?Saint Martin Stefan?Roger 《International Journal of Earth Sciences》2004,93(4):621-633
Distance correlations of Late Tortonian–Messinian littoral carbonate complexes are proposed from the study of eight platforms in the western and central Mediterranean. Correlations are based on the identification of two major biological sedimentary cycles and of two index surfaces. Surface A is a maximum flooding surface during cycle 1 at around 6.7 Ma. Surface B is a regional marine planation surface at around 5.95 Ma, at the base of cycle 2 (Terminal Carbonate Complex). A general sedimentary model is proposed for the 7–5.6-Ma time-span. The boundary between cycles 1 and 2 is coincident with the onset of the Messinian Salinity Crisis, and appears to be related to major environmental–paleo-oceanographic changes in the Mediterranean, rather than to a major sea-level drop or to climatic change. 相似文献