The Westernmost Tethys Blog Geology mapping, basin analysis and 3D modeling

05/20/2020

Evolutionary geological models of the central-western peri-Mediterranean chains

Filed under: paleogeography,Tectonosedimentary model,Tethys — Tags: , , , — messinianalicante @ 8:06 AM

Two main groups of geological models presented over the last four decades on the paleogeographic, paleotectonic and geodynamic eo-Alpine and neo-Alpine evolution of the central-western Mediterranean area were compared. The comparison was carried out mainly considering the main stratigraphic, sedimentological, petrographic, structural and plate tectonic constraints. Moreover, recent geophysical interpretations and reconstructions were also considered with an aim of presenting all the different results. The models can roughly be grouped into two main classes. First family considers the presence of the Mesozoic Tethyan Ocean, where a single oceanic basin is located between Africa and Europe and from which both eo-Alpine and neo-Alpine chains were generated during the Cretaceous to Miocene time span. Conversely, the other class considers the occurrence of at least two Tethyan oceanic branches (or with thinned continental crust) since the Jurassic, separated by one or more microcontinents. The pros and cons of both classes of models are presented. Progressive innovations and improvements to the two groups of models were proposed over the years. However, because the modelsare based on different data sets resulting from basic geological studies or obtained by means of other approaches, they often do not integrate easily.This caused interpretative difficulties and terminological uncertainties for their comparison, and completely different models were considered equivalent and, sometimes, the same terminology was used indifferently to identify different geological subjects. The main differences between the examined models concern the kinematic reconstructions and by hence in the paleogeographic and paleotectonic interpretations. The discussion presented in this paper aims at contributing to clarify and update the state of knowledge on this controversial topic.

General framework and correlations of the main evolutionary stages and geodynamic events (Triassic to Pliocene) of the eoalpine and neo-alpine systems reconstructed in different sectors of the central-western peri-Mediterranean chains (A to C boxes). (a). Palaeogeographic sketch map of the Central-Western Tethys (at Jurassic times) with the location of the sectors mentioned in the work; (b). Sketch map of present times showing the central-western peri-Mediterranean chains with the location of the sectors mentioned in the work; (c). Main evolutionary stages and geodynamic events (Triassic to Pliocene) of the different sectors of the central-western peri-Mediterranean chains.

Cite as: Guerrera, F., Martín-Martín, M., and Tramontana, M. (2019): Evolutionary geological models of the central-western peri-Mediterranean chains: a review. International Geology Reviews. 1-22. doi: 10.1080/00206814.2019.1706056

12/30/2019

Oligo-Miocene evolution of the Paratethyan branches

A comparison of the stratigraphic record between two different branches of the Tethys is attempted for the first time. This study concerns the main Oligocene-Miocene tectono-sedimentary events in the Cenozoic units of the Moldavidian Basin (Romanian Eastern Carpathians) and the Maghrebian Flysch Basin (Maghrebian Chain and its lateral extension in the Betic and Southern Apennine Chains). Both basins are characterized by three main general Oligo-Miocene successions (internal, mixed, and external) corresponding to three subdomains controlled by the geological evolution of opposite plate (or microplate) margins and affected by a similar tectonic evolution. The successions of the three subdomains of the two basins show very similar features regarding stratigraphic records (lithofacies and petrofacies associations, unconformities, marker-levels, age), and the space-time sediment supply diversification (i.e., immature and super-mature arenites coming from opposite margins). Furthermore, pre-, syn- and post-orogenic successions have been identified in the geological reconstructions of both basins. The tectonic control on depositional processes (i.e., a large amount of siliciclastic supply confined in restricted time ranges, widespread volcaniclastites linked to acid-intermediate penecontemporaneous volcanic activity), and the appearance of indicators of syn-sedimentary tectonic activity (turbidites, slumps, and olistostromes) result in correlable events related to deformation phases that in turn are indicative of a similar evolution. Also, the basinal evolutionary stages (i.e., beginning of terrigenous supply, thrust-top basin formation and gravitational sliding, molassic and/or intramontane sedimentary cycles), the timing of deformation phases (drifting, foredeep), and geotectonic events (from extension to compression and post-orogenic deformation) seem to be similar. All results are encompassed in an evolutionary geodynamic model considered in the context of the Africa-Europe convergence where intermediate microplates are involved. This complex framework implies a progressive reorientation of convergence direction of these microplates that occurs during similar geodynamic events leading to the closure of the western Tethys Ocean and its related late-Alpine branches. This comparative approach, if applied to similar evolutionary phases of other mountain chains, can be useful for different geological contexts of other orogenic belts, especially to check the major general geological constraints for their evolution.

Paleogeographic evolutionary sketches of thewestern Tethyan domains for Cretaceous (A), Oligocene (B), Aquitanian (C) and Langhian (D). Relationships between microplates and basins, tectonic transport, and opening and closing of basins are shown (based also on data fromGuerrera et al., 1993, 2012a, 2012b, Belayouni et al., 2009; Amadori et al., 2012; Guerrera and Martín-Martín, 2014).

Cite as: Martín-Martín, M., Guerrera, F., Miclăuș, C., and Tramontana, M. (2020): Similar Oligo-Miocene tectono-sedimentary evolution of the Paratethyan branches represented by the Moldavidian Basin and Maghrebian Flysch Basin. Sedimentary Geology 396: 105548

12/13/2019

Jimenez de Cisneros exhibition at Crevillent

Filed under: Sin categoría,Tectonosedimentary model — Tags: , — messinianalicante @ 2:07 PM

In the Crevillent town takes place an exhibition on the geologist Daniel Jimenez de Cisneros celebrating the 100 years of the publication of the first geological study of the Crevillent Sierra.

The University of Alicante has been collaborating in the exhibit 15-years after the 2004-tribute-simposium to Don Daniel Jimenez de Cisneros. The link bellow show two videos made for the event.

 

Catoon trailer:

 

link to the facsimil-book published:

www.academia.edu/41114909/

10/25/2019

Tectonic breakup in the Eastern Betic zone

Six Paleogene-Aquitanian successions have been reconstructed in the Alicante area (eastern External Betic Zone). The lithofacies association evidences “catastrophic” syn-sedimentary tectonic processes consisting of slumps, mega-olisthostromes, “pillow-beds” and turbiditic deposits  (Figure 1).

Figure 1. Field photos of the main macro-tectofacies found in the study area (see text for details). (A) A typical Lower Eocene sequence of the Villafranqueza section. (B) Calcarenite turbidite with convolute bedding (Lower Eocene, Villafranqueza). (C) Two Oligocene carbonate turbiditic channelized bodies (Busot). (D) Oligocene conglomeratic bed with erosional base and reverse grading of clasts, typical of debris flow deposits (Busot). (E) Oligocene slumped level and pillow-beds (Busot). (F) Oligocene mega-flute casts indicating a northwestwards-directed paleocurrents (Relleu). (G) Oligocene pillow-beds (Relleu). (H) Oligocene mega-olisthostrome with huge blocks (Playa Nudista). (I) Slumped megabed (Playa Nudista).

This kind of sedimentation is related to unconformity surfaces delimiting sequence and para-sequence cycles in the stratigraphic record (Figure 2).

Figure 2. Unconformities, associated gaps of the Eocene and Oligocene-Miocene depositional sequences compared with the sedimentary cycles of (Vera, 2000). The figure shows a basement tectonic interpreted as folding during the Eocene and blind thrust during the Oligocene-Aquitanian. The different evolutionary trends are discussed in the text.

The data compiled have enabled the reconstruction of the Paleogene-Aquitanian paleogeographic and geodynamic evolution of this sector of the External Betics. During the Eocene the sedimentary basin is interpreted as a narrow trough affected by (growth) folding related to blind thrust faulting with a source area from the north-western margin, while the southeastern margin remained inactive. During the Oligocene-Aquitanian, the sourcing margin became the southeastern margin of the basin affected by a catastrophic tectonic (Figure 3).

Figure 3. Paleogeographic-geodynamic model of the Alicante Trough during Eocene and Oligocene-Miocene times.

The activity of the margins is identified from specific sediment sources area for the platform-slope-troughsystem and from tectofacies analysis. The southeastern South Iberian Margin is thought to be closer to the Internal Betic Zone, which was tectonically pushing towards the South Iberian Margin. This pushing could generate a lateral progressive elimination of subbetic paleogeographic domains in the eastern Betics (Figure 4).

Figure 4. Synthetic Oligocene-Aquitanian paleogeographic-geodynamic model proposed for the western.

This geodynamic frame could explain the development of such “catastrophic” tectono-sedimentary processes during the Late Oligocene-Early Miocene.

Cite as: Guerrera, F. and Martín-Martín, M. (2014): Paleogene-Aquitanian tectonic breakup in the Eastern External Betic Zone (Alicante, SE Spain). Revista de la Sociedad Geológica de España, 27(1): 271-285.

 

07/26/2019

Source areas in the Agost Basin (Betic Cordillera)

Filed under: Betics,Tectonosedimentary model — Tags: , , , — messinianalicante @ 7:52 AM

A new work to illustrate a changes in source areas related with pull-apart basin  in the Betics. Here the link to the work in researchgate.

Sedimentary and mineralogical analyses were performed in the Neogene Agost Basin (External Domain, Betic Cordillera) to reconstruct relationships between tectonics and sedimentation, and source areas evolution over time.

Geological Setting

Figure 1) A: Index map; B: Geological sketch showing the main zones and units of the Betic Cordillera; C: Geological map based on the main sedimentary cycles proposed by Vera (2004).

 

The sedimentary analysis allowed defining two sedimentary sequences: (1) Lower Stratigraphic Unit, Serravallian p.p. and (2) Upper Stratigraphic Unit, post Lower Tortonian (Upper Miocene p.p.)separated by an angular unconformity. They consist of marine (lithofacies L-1to L-3) and continental (lithofacies L-5to L-8) deposits respectively (Figure 2).

Figure 2. Lithostratigraphic record and correlations of four representative successions (logs 1 to 4) of the Agost Basin. The two main sequences (Lower Stratigraphic Unit, LSU and Upper Stratigraphic Unit, USU) separated by an angular unconformity are evidenced. Depositional environments, supplies and the isochronous lines T1-T5 are also indicated.

 

The analysis of mineralogical assemblages and some XRD parameters of the sedimentary sequences (Figure 3) and older formations (Figure 4) allowed recognizing a sedimentary evolution controlled by the activation of different source areas over time.

Figure 3. Mineralogical results of the Neogene sedimentary record of the Agost Basin (LSU and USU, given as the average value from the set of samples (n) in each lithofacies L-1 to L-8 included in tab. 2 for the whole rock and the <2 µm grain-size fraction (in wt. %). Ranges and average values of the intensities ratio of the Qtz(001)/Qtz(101) peak areas of quartz, and Sme(003)/Sme(002) peak areas of smectite and Ill(002)/Ill(001) peak areas of illite under ethylene glycol solvation are included.

 

Figure 4. Mineralogical results concerning the source areas given as the average value from the set of samples (n) in each Sedimentary Cycle included in tab. 1 for the whole rock and the <2 µm grain-size fraction (in wt. %). Ranges and average values of the intensities ratio of the Qtz(001)/Qtz(101) peak areas of quartz, and Sme(003)/Sme(002) peak areas of smectite and Ill(002)/Ill(001) peak areas of illite under ethylene glycol solvation are included.

 

In particular, the Ill+Kln±Sme+Chl clay-mineral association characterizes the supply from Triassic formations; the Ill+Kln+Sme association from Albian formations; the Sme+Ill±Kln+(I-S) and Sme+Ill±Kln associations from Upper Cretaceous p.p.formations; and the Sme+Ill±Kln+(I-S) association from Paleogene formations, testifying a tectonic mobility of the basin margins differentiated over time (Figure 5).

 

Figure 5. (A) Comparative plots of XRD parameters, traceable mineral phases, and clay-mineral associations of the Neogene sedimentary record of the Agost Basin (LSU and USU, including the lithofacies L-1 to L-8) and source areas (Sedimentary Cycles I to VI as Triassic p.p., CI; Albian p.p., CIV; Cenomanian-Turonian p.p., CV-CT; Upper Cretaceous p.p., CV-S; and Paleogene p.p., CVI); purple, green, and orange dotted lines identify supplies from predominant Triassic, Cretaceous, and Upper Cretaceous-Paleogene source areas, respectively. The ternary plots for the whole-rock (B) and the <2 µm grain-size fraction (C) mineralogy, given as the average value (in wt. %) from the set of samples in each Sedimentary Cycle (tab. 1, fig. 4) and lithofacies (tab. 2, fig. 5), show three compositional fields corresponding to predominant Triassic like (TR), Albian like (AL), and Upper Cretaceous-Paleogene like (CP) mineralogical associations mixing in variable proportions to determine the mineralogical associations from L-1 to L-8. Samples with gypsum and chloride as typical Triassic mineral phases to identify the Triassic influence in F-1 to F-8 are indicated.

 

This reconstruction leads to propose detailed relationships between types of deposits and provenance and not a classic “unroofing”, as follows: (i) the lithofacies L-1 (lithofacies L-2 and L-3 were not analysed) is characterized by the Ill+Kln+Sme mineralogical association indicating an origin from the Albian formations; (ii) the lithofacies L-4 shows a mixture of Ill+Kln+Sme and Sme+Ill+Kln associations sourced from the Albian and Upper Cretaceous formations; (iii) the lithofacies L-5 is characterized by the Sme+Ill±Kln+(I-S) association indicating a provenance from the Upper Cretaceous and Paleogene formations; (iv) the lithofacies L-6 to L-8 are characterized by the Ill+Kln±Sme+Chl association indicating a supply mainly from Triassic deposits. The evolutionary sedimentary model reconstructed for the Agost Basin, which improves a previous contribution about the same area, has been correlated with those reported in other intramontane Neogene basins in the Betic-Rifian Arc studied with similar resolution, so obtaining useful information for regional reconstructions.

Figure 6. Tectono-sedimentary evolutionary model with location of source areas of the Agost Basin and surrounding areas. A: Middle Miocene stage (Lower Stratigraphic Unit); B: Late Miocene stage (Upper Stratigraphic Unit).

 

 

Cite as: Martín-Martín, M., Guerrera, F., Alcalá, F. J., Serrano, F., Tramontana, M. (2018): Source areas evolution in the Neogene Agost Basin (Betic Cordillera): implications for regional reconstructions. Italian Journal of Geoscience. 2018, 137(3): 433-451. doi:10.3301/IJG.2018.14

 

07/10/2019

The Agost Basin (Betic Cordillera, Alicante province, Spain): a pull-apart basin involving salt tectonics

Filed under: Betics,Tectonosedimentary model — Tags: , , , — messinianalicante @ 12:05 PM

A new work to illustrate a strike-slip basin in the Betics. Here the link to the publisher.

The Agost Basin is characterized by a Miocene-Quaternary shallow marine and continental infilling controlled by the evolution of several curvilinear faults involving salt tectonics derived from Triassic rocks. From the Serravallian on, the area experienced a horizontal maximum compression with a rotation of the maximum stress axis from E-W to N-S.

Figure 1) A: Index map; B: Geological sketch showing the main zones and units of the Betic Cordillera; C: Geological map based on the main sedimentary cycles proposed by Vera (2004).

 

Geological setting

Figure 2) A: Detailed geological map of a sector of the Novelda-Jijona Strike-Slip Fault zone including the Agost Basin and surrounding areas (location shown in Fig. 1C); B: Detailed geological map of the Agost Basin, including the five isochronous lines T1-T5.

Figure 3) Geological cross sections (located in Figure 2) showing the lateral structural evolution of the Novelda-Jijona Strike-Slip Fault. The insertion of isochronous lines T1-T5 is useful for lateral correlations in the Agost Basin.

The resulting deformation gave rise to a strike-slip fault whose evolution is characterized progressively by three stages (see Figure 4): (i) stepover/releasing bend with a dextral motion of blocks; (ii) very close to pure horizontal compression; and (iii) restraining bend with a sinistral movement of blocks.

Figure 4) Paleogeographic model of the Agost Basin and surrounding relief with indications of sedimentary environments and isochronous lines T1-T5.

In particular, after an incipient fracturing stage, faults generated a pull-apart basin with terraced sidewall fault and graben subzones developed in the context of a dextral stepover during the lower part of late Miocene p.p. The occurrence of Triassic shales and evaporites played a fundamental role in the tectonic evolution of the study area. The salty material flowed along faults during this stage generating salt walls in root zones and salt push-up structures at the surface. During the purely compressive stage (middle part of late Miocene p.p.) the salt walls were squeezed to form extrusive mushroom-like structures. The large amount of clayish and salty material that surfaced was rapidly eroded and deposited into the basin, generating prograding fan clinoforms. The occurrence of shales and evaporites (both in the margins of the basin and in the proper infilling) favored folding of basin deposits, faulting, and the formation of rising blocks. Later, in the last stage (upper part of late Miocene p.p.), the area was affected by sinistralrestraining conditions and faults must have bent to their current shape. The progressive folding of the basin and deformation of margins changed the supply points and finally caused the end of deposition and the beginning of the current erosive systems. On the basis of the interdisciplinary results, the Agost Basin can be considered a key case of the interference between salt tectonics and the evolution of strike-slip fault zones. The reconstructed model has been compared with several scaled sandbox analogical models and with some natural pull-apart basins.

Figure 5) Comparison with scaled analogical models and natural pull-apart basins. A: sandbox analogic model, non-overlapping releasing sidestep, to simulate the kinematic and geometric evolution of pull-apart basins, after Dooley and McClay (1997); B: Sketch map of the Dead Sea Basin (from Keydar et al. 2013, modified); C: Sketch map of the Salina del Fraile in Argentina (from Reijs and McClay, 2003, modified); D: Sunik pull-apart basin in Armenia (from Karakhanian et al., 2002, modified).

Research supported by: Research Project CGL2016-75679-P, Spanish Ministry of Education and Science; Research Groups and Projects of the Generalitat Valenciana, Alicante University (CTMA-IGA); Research Group RNM 146, Junta de Andalucía; Grants from University of Urbino “Carlo Bo”, responsible M. Tramontana.

Cite as: Martín-Martín, M., Estévez, A., Martín-Rojas, I., Guerrera, F., Alcalá, F. J., Serrano, F., Tramontana, M. (2018): The Agost Basin (Betic Cordillera, Alicante province, Spain): a pull-apart basin involving salt tectonics. International Journal of Earth Sciences. 107, 2: 655-671. Doi: 10.1007/s00531-017-1521-6

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