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Festa et al., 2013 - Draft

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Festa et al., 2013 - Draft

  1. 1. T E R 1 2 0 8 2 Journal Code Manuscript No. Dispatch: 13.11.13 - CE: Malarvizhi No. of pages: 10 PE: Revathi doi: 10.1111/ter.12082 New insights on diapirism in the Adriatic Sea: the Tremiti salt structure (Apulia offshore, southeastern Italy) Vincenzo Festa, Gianvito Teofilo, Marcello Tropeano, Luisa Sabato and Luigi Spalluto Dipartimento di Scienze della Terra e Geoambientali - via E. Orabona 4, Universit degli Studi “Aldo Moro” di Bari, Bari 70125, Italy a ABSTRACT Miocene and is still active today. An ancient extensional SE-dipping fault, cutting an older Mesozoic low-amplitude anhydritic ridge, played an important role during salt mobilization, which was promoted by NW-SE shortening. The diapir grew in the footwall of this fault, causing its upward propagation. In some places, the ancient fault served as a preferential channel for the upward migration of the anhydrites. Colour online, BW in print D I R IA N 200 km C TI A N44° R Ad ria tic I D P E N N I Pla halo tfor m strukinetic ctur Tremiti es Islands Adria Fig. 2 Gargano Promontory Basi tic S n E Apuli A A an P N E S TYRRHENIAN N40° SEA U L I A S N42° Plat IONIAN form ALBANIDES E © 2013 John Wiley Sons Ltd D Correspondence: Dr. Vincenzo Festa, Dipartimento di Scienze della Terra e Geoambientali - via E. Orabona 4, Universit degli Studi “Aldo Moro” di Bari, a Bari 70125, Italy. Tel.: 0039 080 5443468; e-mail: vincenzo.festa@uniba.it A Triassic to Lower Jurassic evaporites developed in the peri-Tethyan and proto-Atlantic areas over epicratonic platforms (e.g. Courel et al., 2003; Alves et al., 2006; Hudec and Jackson, 2007). Near and along the fronts of the Apennines, DinaridesAlbanides and Hellenides orogens (Mediterranean Sea region), these evaporites migrated upwards to form diapirs, mostly during the Neogene, often inducing sea-floor deformation in the form of ridges (e.g. Underhill, 1988; Zelilidis et al., 1998; Kamberis et al., 2000; Kokinou et al., 2005; Scrocca, 2006; Alves et al., 2007; Geletti et al., 2008; Kokkalas et al., 2013). Tectonic shortening associated with the accretion of the orogens enhanced salt mobilization within both the external thrusts area (e.g. Kokkalas et al., 2013) and the foredeep sensu stricto (i.e. the sector not involved in thrusting; Scrocca, 2006). Geletti et al. (2008, and references therein) highlighted the occurrence of several diapirs in the central Adriatic Sea, between the opposite fronts of the Apennines and Dinarides (Fig. 1). Here, diapirs are characterized by elongated shapes, mostly E17° Introduction E19° Terra Nova, 0, 1–10, 2013 E15° The reinterpretation of public seismic profiles in the Adriatic offshore of Gargano (Apulia, southern Italy) allowed the detection of a kilometre-scale salt-anticline, the Tremiti diapir, within the larger Tremiti Structure. This anticline was generated by diapirism of Upper Triassic anhydrites within a thick Mesozoic to Quaternary basinal sedimentary succession. Both internal stratal patterns and shapes of Plio-Quaternary units, and the occurrence of an angular unconformity between early Tortonian and Pliocene rocks on the Tremiti Islands, suggest that halokinesis began during the late A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 SEA Fig. 1 Schematic structural map of the region around the Adriatic Sea (after Zappaterra, 1990, 1994; modified). In the area not involved in the Apennines and Dinarides opposite orogens, the Meso-Cenozoic paleogeographic position of the Adriatic Basin between the Apulian and Adriatic carbonate platforms is shown. The fronts of the Apennines and Dinarides are according to Scrocca (2006), and Fantoni and Franciosi (2010), respectively. The halokinetic structures inferred or hypothesized (e.g. the SW–NE-striking structure along the Tremiti Islands) by previous studies are also indicated (after Geletti et al., 2008; modified). The inset indicates the study area. 1
  2. 2. Diapirism in the Adriatic Sea: the Tremiti salt structure • V. Festa et al. Terra Nova, Vol 0, No. 0, 1–10 ............................................................................................................................................................. ra, 1990, 1994; Bernoulli, 2001; Fig. 1). This pelagic domain developed as a consequence of early Jurassic rifting of an epeiric area dominated by carbonates (Rhaetian dolostones and overlying early Jurassic limestones of the Calcare Massiccio Fm, Fig. 3). The epeiric platform was rooted on Norian anhydrites and shallow-water limestones and dolostones (Burano Fm; Foresta Umbra1 well, Fig. 3), which overlie Permian continental deposits (Verrucano Fm) draping the Hercynian basement (Ricchetti et al., 1988). The Adriatic Basin succession rests on the Calcare Massiccio Fm and consists mainly of Jurassic to late Miocene pelagic limestones; thin Messinian evaporites separate this succession from the overlying Geological setting During the Mesozoic, in the Adria Plate (sensu Channell et al., 1979), a narrow pelagic basin (the Adriatic Basin), flanked by carbonate platforms (Apulian, to the SW, and Adriatic, to the NE), occupied roughly the same position as the present-day Adriatic Sea (Zappater- Famoso 1 Colour online, BW in print 42°31’57” B4 26 Eterno 1 50 0 6 B4 27 BR 2 26 3 BR 26 4 BR 16 8- 21 Fig. 4 M13 B4 1000 Tremiti Islands 500 500 B4 15°06’13” 42 BR B4 Lesina Marina MESOZOIC BASINAL DOMAIN 16 9- 30 B4 41 32 ME SO MESOZOIC PLATFORM Fig. 7 16°03’26” 5a 28 g. 10 km 5b B BR R26 26 0 1 Fi N 16 g. 26 BR Fi BR g. 00 Fi 15 8- BR 10 12 7 1000 5 2 lead to different interpretations (e.g. Finetti and Del Ben, 2005; Scisciani and Calamita, 2009), particular attention has been paid to those typical pre- to post-halokinesis geometries and terminations of the reflectors within the host-rock of a salt-diapir (e.g. Pascucci et al., 1999; Alves et al., 2002, 2009; Rowan et al., 2003; Stewart, 2007). 26 NW–SE and secondly, NE–SW trending. Geletti et al. (2008) also hypothesized that the NE–SW-striking ridge, whose culmination forms the Tremiti Islands, could represent a halokinesis structure. The ridge, about 15 km north of Gargano (Apulia, southeastern Italy; Figs 1 and 2), corresponds to the Tremiti Structure of Andr and Doulcet e (1991). Several different interpretations based on local seismicity and/or seismic profiles and/or regional geodynamic modelling have been suggested for the origin of the Tremiti Structure. It has been suggested to be a pushed-up ridge, accommodating deformation occurring along faults of regional extent characterized by either E–W right-lateral kinematics (Mele et al., 1990; Argnani et al., 1993; Favali et al., 1993; Doglioni et al., 1994; Gambini and Tozzi, 1996) or NE–SW left strike-slip movement (Finetti and Del Ben, 2005) or undefined kinematics leading to a compressional or transpressional setting (Scisciani and Calamita, 2009). The diapiric origin hypothesized by Geletti et al. (2008) can be supported by comparing sea-floor deformation along the Tremiti Structure with that induced by Plio-Quaternary diapirism of the Triassic anhydrites in the subsurface of the Adriatic Sea (Scrocca, 2006; Nicolai and Gambini, 2007; Geletti et al., 2008; Grandic and Kolbah, 2009). In addition, a few kilometres south of the Tremiti Islands, around Lesina Marina village (Fig. 2), the cropping out of exotic gypsum rocks that rose up from the Triassic anhydrite source (Bigazzi et al., 1996) could represent further evidence supporting the hypothesized diapiric origin for the Tremiti Structure. To verify this hypothesis, the seismic reflection profile M13 of the CROP Project (Scrocca et al., 2003), and both free exploration wells and seismic reflection profiles of the ViDEPI Project (2012; Fig. 2) dating back to the 1980–1990s, was interpreted. The profiles of the ViDEPI Project have been scaled to make times and distances consistent with the M13 CROP Project line. Owing to the low quality of these old, nonmigrated seismic profiles, which can BR 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 Peschici 1 ZO IC SHE LF 41°47’07” MARGIN Foresta Umbra 1 Fig. 2 Map of the study area around the Tremiti Islands (after Google Earth, 2013; modified). White contour lines represent the isobaths of the base of the Pliocene deposits (after Andr and Doulcet, 1991; modified); the Tremiti Structure is e the narrow area where the base-Pliocene depth abruptly decreases. Analysed wells (shown in Fig. 3) and the grid of the studied seismic profiles are indicated. Thicker orange lines show the portions of the interpreted seismic profiles M13, BR169-32, BR168-21 and B426, shown in Figs 4, 5a,b and 6, respectively. © 2013 John Wiley Sons Ltd
  3. 3. V. Festa et al. • Diapirism in the Adriatic Sea: the Tremiti salt structure ............................................................................................................................................................ Foresta Umbra 1 0m (–160 m) 0m (55 m) Aptian-Albian Marne a Fucoidi Messinian Gessoso- Tortonian Early Cretaceous Middle Late Jurassic Jurassic Base of Pliocene Schlier Scaglia Cinerea Messin. C Cenomanianmiddle Eocene Thickness: variable, up to 2600 m Aptian-Albian ThitonianBarremian Scaglia Calcarea Marne a Fucoidi Maiolica Dogger Malm Top of Calcare Massiccio Fm Schlier Aquit.Langh. Oligoc. Calcari ad Aptici Late Lias Gessoso- ? Serrav.Torton. Bisciaro Scaglia Cinerea Late CretaceousEocene Vp = 4100 m/s Rosso Ammonitico Corniola 1275 m Scaglia Calcarea Marne a Fucoidi Maiolica Dogger Malm Calcari ad Aptici Late Lias Middle Lias Calcari ad Aptici Early-Middle Jurassic Late Eocenemiddle Oligocene Maiolica Early Jurassic Thickness: variable, up to 1400 m Plio-Quaternary D Plio-Quaternary Vp = 1800 m/s 0m (809 m) Ripe Rosse Fm Calcari ad Aptici equiv. in slope facies Peschici 1 Eterno 1 0m (–143 m) Persistent shallow-water conditions through the Early-Middle Jurassic Famoso 1 Late Jurassic Seismostratigraphic units Rosso Ammonitico Corniola Middle Lias Early Lias Calcare Massiccio Fm m 900 2270 m B 600 Thickness: variable, up to 2500 m Rhaetian Vp = 5900 m/s Early Lias Calcare Massiccio Fm 300 3126 m 0 Late Triassic 3290 m Top of Triassic anhydrites Cherty limestones Marly limestones and marls A Dolostones Limestones Burano Fm Lithology 4303 m Norian 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 Colour online, BW in print Terra Nova, Vol 0, No. 0, 1–10 Anhydrites Vp = 6400 m/s 5912 m Fig. 3 Lithostratigraphic correlation between exploration wells drilled in the Adriatic offshore, i.e. Famoso 1 and Eterno 1, and in the Gargano onshore, i.e. Peschici 1 and Foresta Umbra 1 (see Fig. 2 for location). Lithostratigraphy of the Gargano wells is derived from the original data of the ViDEPI Project (2012) modified after Bosellini et al. (1993, 2000). Seismostratigraphic units and their maximum thicknesses computed using interval velocities (Vp) are indicated in the left part. Vp of Unit A, after Geletti et al. (2008); average Vp of Units B, C and D, according to Bally et al. (1986). The correlation between seismostratigraphic and lithostratigraphic units is also shown. © 2013 John Wiley Sons Ltd 3
  4. 4. Diapirism in the Adriatic Sea: the Tremiti salt structure • V. Festa et al. Terra Nova, Vol 0, No. 0, 1–10 ............................................................................................................................................................. Plio-Pleistocene foreland basin clays (Santantonio et al., 2013; Famoso1 and Eterno1 wells, Fig. 3). Seismic stratigraphy Four main seismostratigraphic units (A–D, from the bottom; Fig. 3) were identified in the studied area by reviewing seismic- and well-data in accordance with the most recent literature (e.g. Santantonio et al., 2013). Unit A, exhibiting a semi-transparent seismic facies topped by a high amplitude reflector (e.g. Fig. 4), is represented by the anhydritic portion of the Burano Fm. Unit B, topped by a strong reflector, exhibits discontinuous and poorly defined reflectors (Figs 4, 5a,b and 6), and consists of Burano Fm limestones and dolostones, Rhaetian dolostones and Calcare Massiccio Fm limestones (Fig. 3). Unit C groups middle Lias to Messinian lithostratigraphic units (Famoso 1 and Eterno 1 wells, Fig. 3) corresponding to the Adriatic Basin succession. It shows welldefined, continuous, subparallel reflectors and is topped by strong reflectors of the Gessoso-Solfifera Fm (Figs 4, 5a,b and 6). In the Tremiti Islands, the top of the unit crops out, in the form of an angular unconformity between tilted Palaeocene, Eocene and Miocene (Langhian to early Tortonian) rocks below and thin Plio-Pleistocene deposits above (Cremonini et al.,1971; Andriani et al., 2005; Brozzetti et al., 2006; Miccadei et al., 2011). Finally, Unit D consists of PlioQuaternary emipelagites (Famoso 1, Eterno 1 wells, Fig. 3), and is characterized by some continuous reflectors, and, locally, semi-transparent seismic facies (Figs 4, 5a,b and 6). and 5a,b). Due to the relatively high Vp value of the anhydrites, the reflections related to the interbedded dolostones are affected by velocity pull-up phenomena within the diapir. The top of the diapir stands at c. 1.8 s in seismic profile M13 (Fig. 4), and between c. 0.4 and 0.8 s in the profiles BR168-21 and BR169-32 (Fig. 5a,b). Considering the Vp value of the overlying sediments, the roof is at a minimum depth of c. 750 m from the sea bottom. Therefore, the diapir has risen up to c. 3750 m from the Triassic anhydrite source. On the flanks of the diapir, reflectors of Unit B, which has a nearly constant thickness, and Unit A are geometrically concordant. In contrast, the overlying units C and D exhibit variable thickness. Unit C is definitely thinner above the diapir, while an abrupt increase in thickness is observed laterally, especially on the eastern and southeastern sides (Figs 4 and 5a,b). A local thickening of this sidering the interval velocities (Vp) of the overlying sedimentary rocks, a depth of ca. 4500 m has been calculated for this high amplitude reflector. Along the Tremiti Structure (Figs 4 and 5a,b), seismic wave diffractions, reflected refractions and velocity distortion phenomena strongly suggest halokinesis of the Triassic anhydrites. In addition, and as shown on seismic profile M13, the same seismic record may result from a fault located above the steeply inclined eastern flank of a halokinesis structure, i.e. the Tremiti diapir (Fig. 4). A chaotic and poorly defined seismic signal typically characterizes the diapir, while the reflectors of the wall-rock appear generally continuous and better developed. Often, the reflected refractions, in association with the steeply inclined flanks of the diapir, can be observed crosscutting the primary reflections of the host Unit B and the lowermost part of Unit C (Figs 4 BR169-32 B428 B430 0 1 Colour online, BW in print 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 2 3 4 0 1 5 km Unit D Unit C Seismic interpretation of the Tremiti Structure The interpretation of seismic lines along the Tremiti Structure required first the identification of the top of Unit A in poorly deformed areas. In agreement with the literature (Finetti and Del Ben, 2005; Geletti et al., 2008; Scisciani and Calamita, 2009), the top of Unit A around the Tremiti Structure has been located at c. 3.5 s in seismic profile M13 (Fig. 4). Con4 2 Salt 3 diapir Unit B Unit A - anhydrites 4 s TWT W-E Fig. 4 Uninterpreted (above) and interpreted (below) non-migrated and multi-channel stacked seismic profile M13 (see Fig. 2 for location). © 2013 John Wiley Sons Ltd
  5. 5. V. Festa et al. • Diapirism in the Adriatic Sea: the Tremiti salt structure ............................................................................................................................................................ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 Colour online, BW in print Terra Nova, Vol 0, No. 0, 1–10 M13 B428 BR168-10 0 (a) 1 2 5 km 0 Unit D Salt 1 diapir Unit C 2 Unit B s TWT NW - SE BR127 BR168-10 0 (b) Unit D 1 Unit C Salt diapir Unit B 2 5 km s TWT NW - SE Fig. 5 (a) Uninterpreted (above) and interpreted (below) non-migrated and multichannel stacked seismic profile BR169-32 (see Fig. 2 for location). (b) Uninterpreted (left) and interpreted (right) non-migrated and multi-channel stacked seismic profile BR168-21 (see Fig. 2 for location). unit can be appreciated in the western sector of seismic profile M13, i.e. on the hangingwalls of synsedimentary faults showing a dip-slip component (Fig. 4). These faults belong to a system of NE-dipping extensional faults © 2013 John Wiley Sons Ltd (Fig. 6), which determined thickness variations in the lower part of Unit C (Figs 4 and 6) and likely of Unit B (Fig. 6) during the Mesozoic extensional stage linked to the Jurassic rifting. The abrupt increase in thickness observed on the eastern side of the Tremiti Structure along seismic profile M13 (Fig. 4) is additional evidence of extensional tectonics. Furthermore, a low-amplitude ridge structure, involving the NE-dipping faults (Fig. 6), developed with a NW– SE trend (Fig. 7). On the flanks of the Tremiti Structure, reflectors show that gentle drag folds involve both Unit B (Fig. 5a,b) and the lower part of Unit C (Figs 4 and 5a,b), which were upturned by rising anhydrite. From the sides to the roof of the diapir, the geometries of reflectors within the wall-rock are compatible with an open, asymmetric anticline affecting both Unit B and Unit C (Figs 4 and 5a,b), which is thinner in its uppermost portion (e.g. Fig. 5a). As shown on seismic profile M13 (Fig. 4), compressive minor faults have been recognized in the eastern side of the diapir. In Unit D, internal unconformities, and reflectors recording upturned strata, are locally observed. Furthermore, the unit exhibits a decrease in thickness approaching the anticline, whose crest is truncated by an erosional surface (Figs 4 and 5a,b). The latter corresponds to an unconformity below the apparently undisturbed Plio-Quaternary sediments. According to well-known shape classifications of salt structures (Jackson and Talbot, 1991; Stewart, 2007; Guerra and Underhill, 2012), a saltanticline-type geometry may be inferred from the seismic profiles of the Tremiti diapir, which is c. 7– 8 km wide (Fig. 5a,b). In map view, the salt-anticline is developed for c. 30 km and its axial-plane trace is arched with a gentle concavity towards the NW; northwards, it strikes NNE–SSW, whereas southwards, it curves towards an ENE– WSW trend (Fig. 7). A strong asymmetry of this salt-anticline can be appreciated in seismic profile M13 (Fig. 4), i.e. along the intermediate part of the NE–SW-striking Tremiti diapir (Fig. 7). Discussion: age and mode of halokinesis Two stages of halokinesis of the Triassic anhydrites can be recognized in the Tremiti Islands area. 5
  6. 6. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 Colour online, BW in print Diapirism in the Adriatic Sea: the Tremiti salt structure • V. Festa et al. Terra Nova, Vol 0, No. 0, 1–10 ............................................................................................................................................................. 0 1 2 3 4 5 km Unit D 1 Unit C 2 Unit B 3 Unit A - anhydrites 4 s TWT SW - NE Fig. 6 (a) Uninterpreted (above) and interpreted (below) non-migrated and multichannel stacked seismic profile B426 (see Fig. 2 for location). The older one is characterized by a low-amplitude ridge structure (Fig. 6), striking parallel to the ancient, extensional NE-dipping faults (Figs 6 and 7), and related to the early Jurassic rifting (Santantonio et al., 2013). The ridge is bordered to the NE by the fault that records the maximum dip-slip displacement (Fig. 6). In accordance with several models of diapirism in extensional tectonic settings (e.g. Vandeville and Jackson, 1992; Schultz-Ela and Jackson, 1996; Rowan et al., 1999; Stewart, 2007; Guerra and Underhill, 2012), this kind of fault could have promoted migration of the salt towards the hangingwall. Here, the low-amplitude ridge likely developed in Unit B during the deposition of 6 Unit C, namely during the regional subsidence that followed the main fault displacement (Fig. 8). The younger halokinesis stage began during the late Miocene. The internal unconformities in Unit D and its thinning approaching the Tremiti diapir (e.g. Fig. 4) indicate that the salt-anticline grew during the Plio-Quaternary due to the upward movement of the Triassic anhydrites (Fig. 9). However, on the Tremiti Islands, the angular unconformity separating early Tortonian deformed rocks from less-deformed Pliocene deposits indicates that this halokinesis deformation began before the Pliocene. Moreover, the diapirism seems to be still active as, on high-resolution seismic profiles, deposits of the post- last glacial interval show weak deformations that also involve the sea floor (Ridente and Trincardi, 2006). Late Paleogene–Neogene halokinesis structures found in the Adriatic Sea, north of the Tremiti Islands, by Geletti et al. (2008, and references therein; Fig. 1) could have been enhanced by horizontal shortening linked to either the Apenninic or Dinaric orogenesis (Scrocca, 2006; Grandic and Kolbah, 2009). In such a setting, the axes of salt-anticlines strike perpendicular to the regional shortening direction, as demonstrated also by Jahani et al. (2009) in the Persian Gulf (i.e. the foreland basin of the Zagros orogen). In the Adriatic Sea, these NW–SE-striking salt-anticlines developed mainly on top of pre-existing NW–SE-striking diapirs, elongated like the old low-amplitude salt ridge in the Tremiti area. In contrast, despite the presence of the old salt ridge, the axis of the younger Tremiti salt-anticline strikes roughly NE–SW, and is perpendicular to the Apennines front. This geometry is coherent with NW–SE shortening (Fig. 7), whose occurrence in the area could be related to the presence of an active tectonic boundary deduced by seismicity and separating the Adriatic into north and south blocks with different velocity motions (Oldow et al., 2002). In addition, this shortening is in accordance with the local component of the E-W right-lateral simple shear inferred by several authors (Mele et al., 1990; Argnani et al., 1993; Favali et al., 1993; Doglioni et al., 1994; Gambini and Tozzi, 1996). The mode of emplacement of the Tremiti diapir, reconstructed in accordance with the NW–SE shortening direction (Fig. 9), is mainly constrained by the interpretation of seismic profile M13 (Fig. 4). The emplacement needed a NE–SW-oriented zone of weakness for the upward migration of the anhydrites (Figs 7 and 9). The abrupt increase in thickness of Unit C on the southeastern side of the Tremiti diapir (Figs 4 and 5a,b) strongly supports the presence of an ancient NE–SWstriking extensional fault (Figs 7 and 9). This inferred fault strikes subparallel to the normal faults accompanying the widespread NW–SE dip-slip faults activated during the Jurassic– © 2013 John Wiley Sons Ltd
  7. 7. Terra Nova, Vol 0, No. 0, 1–10 V. Festa et al. • Diapirism in the Adriatic Sea: the Tremiti salt structure ............................................................................................................................................................ 42°26’09” de . 9 litu Fig amp ge - rid lowitic oic dr oz hy es an B4 26 16 8- Mesozoic dip-slip faults 10 km 21 Anticline Salt axis anticline, i.e. Tremiti diapir BR 9- 32 Fi Tremiti Islands g. g. 5a Tremiti ridge 5b Fault favouring the ascent of the Tremiti diapir Sh or te ni ng 9 Fi g. . Fig 15°13’24” Fi M13 Fig. 4 16 42°02’38” 15°58’49” .8 BR Fi g Fi g. 6 N M Tremiti diapir 10 Fig. 7 Structural sketch map of the Tremiti Islands area, where the old Mesozoic anhydritic low-amplitude ridge and the younger Neogene Tremiti diapir (roughly corresponding to the Tremiti ridge) are emphasized in grey. Note the geometric relationships between the dip-slip Mesozoic faults and the coeval salt low-amplitude ridge, and between the Tremiti diapir and the fault that favoured its rising up. Colour online, BW in print 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 Cretaceous s.l. Unit C Cretaceous (Festa, 2003; Santantonio et al., 2013). Much later, during the NW-SE shortening, the anhydrites migrated in the footwall of the fault, beneath Unit B (Fig. 9). Above the southeastern flank of the diapir, the growth of the anhydritic body determined an upward propagation, with a dip-slip displacement, of the ancient fault (Fig. 9). Drape upbending of Units B and C occurred, and an asymmetric salt-anticline developed (Figs 4 and 9). In addition, the NW–SE shortening may have led to the arching of this fault, which has a gentle concavity towards the NW (Fig. 7). Towards the north-east and southwest terminations of the salt-anticline (Fig. 7), the anhydrites simply used the weakened zone of the ancient fault as a preferential channel for their upward migration through Unit B (e.g. Fig. 10). Upward dragging of Unit B, piercing of the lower part of Unit C, and folding of the intermediate and upper parts of this unit also occurred (Fig. 5a,b). In addition, in the south-west termination of the salt-anticline, an inversion of the ancient dip-slip fault, which occurred during piercing of the anhydrites, would explain both the highest position of Unit C, and the thinness of Unit D in the hangingwall, compared with the footwall (Fig. 10). Concluding remarks Early Jurassic s.l. Unit C Unit B Unit A SW 5 km NE Fig. 8 2D frames summarizing the mode of emplacement of the low-amplitude ridge, from early Jurassic to Cretaceous. Reconstruction is based on the interpretation of the seismic reflection profile in Fig. 6, and is perpendicular to the elongation of the Mesozoic anhydritic low-amplitude ridge (see Fig. 7). © 2013 John Wiley Sons Ltd The occurrence of the Tremiti ridge and its outstanding size are the result of late Miocene to present-day salt tectonics overprinting a Mesozoic low-amplitude salt ridge. A halokinesis structure, the Tremiti diapir, made up of Triassic anhydrites, is located beneath this ridge. The Tremiti diapir forms an anticline whose axis is approximately perpendicular to both the elongations of most of the Neogene diapirs, and the Apenninic and Dinaric fronts, which strike NW–SE in the sector of the Adriatic Sea north of Gargano Promontory. The development of this diapir required NW–SE shortening, and occurred along a pre-existing SE-dipping extensional fault, whose origin dates back to the Jurassic–Cretaceous. In its central part, the diapir was emplaced in the footwall of this fault. Both shorten7
  8. 8. Diapirism in the Adriatic Sea: the Tremiti salt structure • V. Festa et al. Terra Nova, Vol 0, No. 0, 1–10 ............................................................................................................................................................. Present-day s.l. Pleistocene s.l. Pliocene s.l. Unit D Late Miocene s.l. Unit C Unit B Unit A 10 km NW SE Fig. 9 2D frames summarizing the mode of emplacement of the Tremiti diapir, from late Miocene to present-day. Reconstruction is based on the interpretation of the seismic profile M13 (Fig. 4), and is subparallel to the elongation of the old Mesozoic anhydritic low-amplitude ridge (see Fig. 7). Colour online, BW in print 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 s.l. Unit D Unit C Unit B Unit A NW 5 km SE Fig. 10 2D schematic interpretation of the seismic profile BR169-32 (Fig. 5a), crossing the southwestern termination of the Tremiti diapir (see Fig. 7 for location). The path taken during upward migration and squeezing of the anhydrites is indicated by the blue arrows, near the fault plane. Note in Unit C, piercing and folding due to the Tremiti diapir. The inversion of the originally dip-slip fault is indicated by the red arrow. The highest position of Unit C, and the thinness of Unit D in the hangingwall, compared with the footwall, can be appreciated. ing and upward growth of the diapir were able to uplift the entire footwall. As a consequence, upward propagation of the fault with dipslip kinematics occurred. Towards the terminations of the diapir, the 8 fault, which was locally reactivated with reverse kinematics, represented a path for the upward migration and squeezing of the anhydrites, which pierced and folded the above wall-rock. These results could represent an interpretive key for the scattered halokinetic structures occurring in the Adriatic Basin, north of the Tremiti Islands. NW-SE-elongated diapirs originally developed during the Mesozoic in the form of lowamplitude ridges, whose geometric features were driven by the activity of extensional faults. During the Neogene, two sets of diapirs with opposite elongations developed. The most representative set consists of halokinesis structures that grew on top of, and parallel to, the pre-existing low-amplitude diapirs. Their fold axes strike NW–SE, i.e. perpendicular to the shortening direction due to the opposite propagation of the Apenninic and Dinaric fronts. In contrast, NW–SE shortening could have locally promoted both salt mobilization and NE–SW-elongated salt-anticlines representing the other set. These halokinesis structures developed parallel to the Tremiti diapir, likely along Jurassic–Cretaceous faults. Acknowledegments This study was supported by “Convenzione tra Autorit di Bacino della Puglia e a Dipartimento Geomineralogico dell’Universit degli Studi di Bari per studi a © 2013 John Wiley Sons Ltd
  9. 9. Terra Nova, Vol 0, No. 0, 1–10 V. Festa et al. • Diapirism in the Adriatic Sea: the Tremiti salt structure ............................................................................................................................................................ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 petrografici e mineralogici, oltre che geologico-strutturali, nell’area di Lesina Marina (FG) – 2009” research funds, to V. Festa. We are grateful to T. Alves, L. Ferranti and an anonymous reviewer, whose suggestions helped us to improve the manuscript. Discussions with D. Scrocca, J. Underhill and S. Nardon were very useful. References Alves, T.M., Gawthorpe, R.L., Hunt, D.W. and Monteiro, J.H., 2002. Jurassic tectono-sedimentary evolution of the Northern Lusitanian Basin (offshore Portugal). Mar. Petrol. Geol., 19, 727–754. 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Hartley, N.T. Grant and R. Hodgkinson, eds), Geol. Soc. London Spec. Publ., 363, 175–206. Hudec, R. and Jackson, M.P.A., 2007. Terra infirma: understanding salt tectonics. Earth-Sci. Rev., 82, 1–28. Jackson, M.P.A. and Talbot, C.J., 1991. A Glossary of Salt Tectonics. Geological Circular, 91-4. The University of Texas at Austin, Bureau 5 of Economic Geology, ???. 44 pp. Jahani, S., Callot, J.-P., Letouzey, J. and Frizon de Lamotte, D., 2009. The eastern termination of the Zagros Foldand-Thrust Belt, Iran: structures, evolution, and relationships between salt plugs, folding, and faulting. Tectonics, 28, TC6004. Kamberis, E., Sotiropoulos, S., Aximniotou, O., Tsaila-Monopoli, S. and Ioakim, C., 2000. Late Cenozoic deformation of the Gavrovo and Ionian zones in NW Peloponnesos (Western Greece). Ann. Geofis., 43, 905–919. Kokinou, E., Kamberis, E., Vafidis, A., Monopolis., D., Ananiadis, G. and Zelilidis, A., 2005. Deep seismic reflection data from offshore western Greece: a new crustal model for the Ionian Sea. J. Petrol. Geol., 28, 185–202. Kokkalas, S., Kamberis, E., Xypolias, P., Sotiropoulos, S. and Koukouvelas, I., 2013. Coexistence of thin- and thickskinned tectonics in Zakynthos area (western Greece): insights from seismic sections and regional seismicity. Tectonophysics, 597–598, 73–84. Mele, G., Mattietti, G. and Favali, P., 1990. Sismotettonica dell’area adriatica: interpretazione di dati sismologici recenti. Mem. Soc. Geol. It., 45, 233– 241. Miccadei, E., Mascioli, F. and Piacentini, T., 2011. Quaternary geomorphological 9
  10. 10. Diapirism in the Adriatic Sea: the Tremiti salt structure • V. Festa et al. Terra Nova, Vol 0, No. 0, 1–10 ............................................................................................................................................................. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 evolution of the Tremiti Islands (Puglia, Italy). Quatern. Int., 233, 3–15. Nicolai, C. and Gambini, R., 2007. Structural architecture of the Adria platform-and-basin system. Boll. Soc. Geol. Ital., (Suppl. 7, 21–37. Oldow, J.S., Ferranti, L., Lewis, D.S., Campbell, J.K., D’Argenio, B., Catalano, R., Pappone, G., Carmignani, L., Conti, P. and Aiken, C.L.V, 2002. Active fragmentation of Adria, the north African promontory, central Mediterranean orogen. Geology, 30, 779–782. Pascucci, V., Gibling, M.R. and Williamson, M.A., 1999. Seismic stratigraphic analysis of Carboniferous strata on the Burin Platform, offshore Eastern Canada. Bull. Can. Petrol. Geol., 47, 298–316. Ricchetti, G., Ciaranfi, N., Luperto Sinni, E., Mongelli, F. and Pieri, P., 1988. Geodinamica ed evoluzione sedimentaria e tettonica dell’Avampaese Apulo. Mem. Soc. Geol. It., 41, 57–82. Ridente, D. and Trincardi, F., 2006. Active foreland deformation evidenced by shallow folds and faults affecting late Quaternary shelf-slope deposits (Adriatic Sea, Italy). Basin Res., 18, 171–188. Rowan, M.G., Jackson, M.P.A. and Trudgill, B.D., 1999. Salt-Related Fault Families and Fault Welds in the Northern Gulf of Mexico. AAPG Bull., 83, 1454–1484. 10 Rowan, M.G., Lawton, T.F., Giles, K.A. and Ratliff, R.A., 2003. Near-salt deformation in La Popa basin, Mexico, and the northern Gulf of Mexico: a general model for passive diapirism. AAPG Bull., 87, 733–756. Santantonio, M., Scrocca, D. and Lipparini, L., 2013. The OmbrinaRospo Plateau (Apulian Platform): evolution of a Carbonate Platform and its Margins during the Jurassic and Cretaceous. Mar. Petrol. Geol., 42, 4– 29. Schultz-Ela, D.D. and Jackson, M.P.A., 1996. Relation of Subsalt Structures to Suprasalt Structures During Extension. AAPG Bull., 80, 1896–1924. Scisciani, V. and Calamita, F., 2009. Active intraplate deformation within Adria: examples from the Adriatic region. Tectonophysics, 476, 57–72. Scrocca, D., 2006. Thrust front segmentation induced by differential slab retreat in the Apennines (Italy). Terra Nova, 18, 154–161. Scrocca, D., Doglioni, C., Innocenti, F., Manetti, P., Mazzotti, A., Bertelli, L., Burbi, L. and D’Offizi, S. (eds.), 2003. CROP Atlas: seismic reflection profiles of the Italian crust. Memorie Descrittive della Carta Geologica d’Italia, 62, 193, 71 plates. Stewart, S.A., 2007. Salt tectonics in the North Sea Basin: a structural style template for seismic interpreters. In: Deformation of the Continental Crust: The Legacy of Mike Coward (A.C. Ries, R.W.H. Butler and R.H. Graham, eds), Geol. Soc. London Spec. Publ., 272, 361–396. Underhill, J.R., 1988. Triassic evaporites and Plio-Quaternary diapirism in western Greece. J. Geol. Soc. London, 145, 269–282. Vandeville, B.C. and Jackson, M.P.A., 1992. The fall of diapirs during thinskinned extension. Mar. Petrol. Geol., 9, 354–371. ViDEPI Project, 2012 (last upgrade). Progetto ViDEPI - Visibilit Dati a Esplorazione Petrolifera in Italia. http://unmig.sviluppoeconomico.gov.it/ videpi/ Zappaterra, E., 1990. Carbonate paleogeographic sequences of the periadriatic region. Boll. Soc. Geol. It., 109, 5–20. Zappaterra, E., 1994. Source-rock distribution model of the Periadriatic region. AAPG Bull., 78, 333–354. Zelilidis, A., Kontopoulos, N., Avramidis, P. and Piper, D.J.W., 1998. Tectonic and sedimentological evolution of the Pliocene-Quaternary basins of Zakynthos island, Greece: case study of the transition from compressional to extensional tectonics. Basin Res., 10, 393–408. Received 4 June 2013; revised version accepted 21 October 2013 © 2013 John Wiley Sons Ltd
  11. 11. Author Query Form Journal: Article: TER 12082 Dear Author, During the copy-editing of your paper, the following queries arose. Please respond to these by marking up your proofs with the necessary changes/additions. Please write your answers on the query sheet if there is insufficient space on the page proofs. Please write clearly and follow the conventions shown on the attached corrections sheet. If returning the proof by fax do not write too close to the paper’s edge. Please remember that illegible mark-ups may delay publication. Many thanks for your assistance. Query reference Query 1 AUTHOR: Please provide the publisher name, publisher location for reference Andr and Doulcet (1991). e 2 AUTHOR: Please provide the publisher name, publisher location for reference Bernoulli (2001). 3 AUTHOR: Please provide the publisher name for reference Bosellini et al. (2000). 4 AUTHOR: Please provide more details (if applicable) for reference Google Earth (2013). 5 AUTHOR: Please provide the publisher location for reference Jackson and Talbot (1991). Remarks
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