Italy

Click Here

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, B10101, doi:10.1029/2008JB005699, 2008

for

Full Article

Differences and similarities between the central and the southern Apennines (Italy): Examining the Gran Sasso versus the Matese-Frosolone salients using paleomagnetic, geological, and structural data Sara Satolli1 and Fernando Calamita1 Received 17 March 2008; revised 29 June 2008; accepted 16 July 2008; published 1 October 2008.

[1] The Apennines consists of the following two major first-order arcuate features: the

northern Apennines Arc and the southern Apennines-Calabrian Arc, separated by the Sangro-Volturno line. In this paper we compare and discuss these major arcs, which are characterized by several differences. These are mainly related to differences in paleogeographic domains, stratigraphic successions, structural setting, and geodynamic evolution. We describe with particular emphasis the following two main salients: the Gran Sasso Range and the Matese-Frosolone Mountains, geographically belonging to the central and the southern Apennines, respectively. We analyze existing geological, structural, and paleomagnetic information from both salients and provide new paleomagnetic and magnetic anisotropy data for eight Messianian-Tortonian sites from the Matese-Frosolone Mountains. The aim of the work is to reconstruct the TortonianQuaternary kinematic evolution of the central Apennines, which represents the junction zone between the northern Apennines Arc and the southern Apennines-Calabrian Arc. Furthermore, we propose to use the different style of paleomagnetic rotations in arcuate shapes as a tool to discriminate if structures located in the central Apennines geologically belong to the northern Apennines Arc or to the southern Apennines-Calabrian Arc. Finally, the results of this study allowed us to interpret the Sangro-Volturno line as an oblique ramp of the Pliocene-Quaternary frontal thrusts. Citation: Satolli, S., and F. Calamita (2008), Differences and similarities between the central and the southern Apennines (Italy): Examining the Gran Sasso versus the Matese-Frosolone salients using paleomagnetic, geological, and structural data, J. Geophys. Res., 113, B10101, doi:10.1029/2008JB005699.

1. Introduction: An Overview of the Apennines 1.1. Geological Framework [2] The Apennines are a fold-and-thrust belt formed during Neogene-Quaternary times and verging toward the Adriatic foreland. The orogenesis affected Triassic to Miocene sedimentary successions belonging to different basin and platform paleogeographic domains of the Adria Mesozoic paleomargin [e.g., Ben Avraham et al., 1990; Ciarapica and Passeri, 2002; Lentini et al., 2002; Patacca and Scandone, 2007]. Two major arcs can be distinguished (Figure 1): the northern Apennines Arc and the southern Apennines-Calabrian Arc, with NE and SE convexity, respectively [Patacca and Scandone, 1989]. In addition, these two first-order arcs contain several second-order arcs. The two major arcs join in the Latium-Abruzzi region (central Apennines), bounded by two main approximately N-S structural features: the Olevano-Antrodoco line [Parotto and Praturlon, 1975] and the Ortona-Roccamonfina [Locardi, 1 Dipartimento di Scienze della Terra, Universita` G. d’Annunzio di Chieti-Pescara, Chieti Scalo, Italy.

Copyright 2008 by the American Geophysical Union. 0148-0227/08/2008JB005699$09.00

1982] or Sangro-Volturno line [Ghisetti and Vezzani, 1983]. The latter has long been interpreted as a crustal scale tectonic feature [Locardi, 1982; Patacca et al., 1990] and is considered the tectonic separation between the northern Apennines Arc and southern Apennines-Calabrian Arc [e.g., Patacca and Scandone, 1989]. [3] The Apennines are composed of structural units of inner origin superimposed on units belonging to the Adria paleomargin. Two extensional tectonic phases, during the Triassic and Early Jurassic, affected the Triassic peritidal carbonate platform [D’Argenio and Alvarez, 1980]. The later phase is documented by successions cropping out in the central Apennines; it divided the Triassic-Lower Jurassic carbonate platform into persistent carbonate platform (Latium-Abruzzi area) and pelagic (Umbria-Marche area) domains. The Lower Jurassic to Lower Cretaceous pelagic succession contains highly variable facies and thicknesses. The depositional environment was influenced by differential subsidence, and characterized by seamounts, bounded by Jurassic normal faults, and deeper basinal areas. The differential subsidence ended before the Aptian, when facies and thickness became uniform in the basinal area [Alvarez, 1990]. In the southern Apennines, the allochthonous units

B10101

1 of 16

B10101

SATOLLI AND CALAMITA: CENTRAL VERSUS SOUTHERN APENNINES

B10101

Figure 1. Tectonic sketch of central Italy (modified after Calamita et al. [2004]). SVL, Sangro-Volturno line; OAL, Olevano-Antrodoco line. Squares indicate the Gran Sasso (Figure 3) and the MateseFrosolone (Figure 5) salients. Black lines indicate the locations of the geological section (Figure 4a) and the line drawing (Figure 4b). (Liguridi-Sicilidi, inner Carbonate Platform, and LagonegroSannio-Molise units (according to Patacca and Scandone [2007, and references therein])) are exposed. In the footwall of the sole thrust of the allochthonous units, the Apulian carbonate units have been recognized and interpreted on the basis of well data and seismic lines as the Apulian duplex [Mostardini and Merlini, 1986], the buried Apulian chain [Cello et al., 1989; Corrado et al., 2002] or the Pliocene Apennine neochain [Boccaletti et al., 2005].

[4] Convergence between the African and European plates started in the Late Cretaceous. The convergence caused the Tethys Ocean to close, and the Apennines to form in the Late Oligocene-Pleistocene, as documented by the ages of siliciclastic deposits [Boccaletti et al., 1990]. During the Middle/Late Miocene to Late Pliocene, the Apennines had coeval occurrence of normal and thrust faults along the western and eastern belt margin, respectively [Elter et al., 1975]. Extension continued during the

2 of 16

B10101


B10101

Figure 2. Tectonic sketch of the Apennines with paleomagnetic data from the literature indicated by numbers in parentheses: 1, Muttoni et al. [1998]; 2, Speranza et al. [1997]; 3, Channell et al. [1978]; 4, Hirt and Lowrie [1988]; 5, Mattei et al. [1995]; 6, Jackson [1990]; 7, Marton and D’Andrea [1992]; 8, Gattacceca and Speranza [2002]; 9, Channell et al. [1990]. Look at Figures 3 and 5 for paleomagnetic details from the Gran Sasso and the Matese-Frosolone salients, respectively. Pleistocene-Holocene (remaining active today) and controlled seismicity in the Apennine mountain range. 1.2. Paleomagnetic Background [5] Many mountain belts display curved structural trends in plan view. Several schemes have been proposed so far to classify them on the basis of the relationship between geometry of displacement and strain trajectory. On the basis of their kinematics, orogens have been subdivided in: oroclines (or rotational arcs), originally linear and subsequently bent during a deformation event; primary (or nonrotational) arcs, where belt curvature is acquired during the initial deformation and is not increased during subsequent deformation [Carey, 1955; Marshak, 1988]; progressive arcs, which developed their arcuate nature contemporaneously with their growing [Weil and Sussman, 2004]. Paleomagnetism, combined with structural geology, is a powerful tool in discriminating primary or secondary mechanism in arcs formation and understanding the kinematics of curved orogens of controversial origin.

[6] The Apennine chain shows curved structures at different scales that have been widely paleomagnetically investigated over the last 35 years. The belt experienced widespread differential vertical axes rotations in the Middle Miocene-Pliocene time interval, which have been explained with different models. Paleomagnetic data from back-arc extensional basins along the Tyrrhenian margin show no rotation [e.g., Mattei et al., 1996], indicating that the opening of the Tyrrhenian Sea was nonrotational. Conversely, data collected in Mesozoic and Miocene-Lower Pliocene sediments show varying amounts of rotation, due to both thrusts and strike-slip fault activity. Available data from the northern Apennines (Figure 2) document a change in paleomagnetic rotations from counterclockwise (CCW) to clockwise (CW) moving southward: strong CCW rotations have been documented in the Emilia-Romagna region [Muttoni et al., 1998; Speranza et al., 1997], while the Sibillini thrust front is characterized by CW rotation in the central sector [Speranza et al., 1997]. Large CCW and CW rotations are documented in the southern Apennines [Scheepers and Langereis, 1994; Speranza et al., 1998;

3 of 16

B10101


B10101

Figure 3. Schematic geological map of the Gran Sasso salient (modified after Satolli et al. [2005]), with rotational domains and corresponding average rotation values (look at text for details). Gattacceca and Speranza, 2002] and Sicily [Channell et al., 1990; Speranza et al., 2003], respectively. The central Apennines form the junction zone between the northern Apennines Arc and the southern Apennines-Calabrian Arc. Here, rotations are related and influenced by the southernmost and northernmost arms of the two major Arcs, respectively. Rotations of different magnitudes and signs have been documented in minor curved shapes. There are minor salients characterized by CCW and CW rotations along the limbs (Gran Sasso Range [Satolli et al., 2005]), block rotations due to strike-slip faults (e.g., central Apennines [Mattei et al., 1995]) and small homogenous CW-rotated structures (e.g., Mount Maiella [Jackson, 1990]; Mount Greco-Mount Genzana [Marton and D’Andrea, 1992]). [7] In this paper, we compare two minor salients (arcuate structures convex toward the foreland [Miser, 1932]), namely the Gran Sasso Range and the Matese-Frosolone Mountains. We use existing geological, structural and paleomagnetic data from the literature and present new paleomagnetic investigations from the Matese-Frosolone Mountains. The aim of the work is to achieve a better understanding on the formation of these two salients and to reconstruct the TortonianQuaternary kinematic evolution of the central Apennines. Moreover, we propose the use of paleomagnetic rotations for discriminating structures belonging to the northern Apennines Arc or to the southern Apennines-Calabrian Arc.

2. Gran Sasso Salient 2.1. Geological Setting [8] The Gran Sasso thrust system (Abruzzo region) forms one of the most external salients of the central Apennines and is characterized by two roughly orthogonal E-W and NS main thrusts, separated by a narrow arc apex (Figures 1, 3,

and 4a). The Gran Sasso unit consists of a Triassic-Miocene sedimentary succession, belonging both to a peritidal carbonate platform domain (Latium-Abruzzi platform) and to its transition zone into a northward and eastward basin (Umbria-Marche basin). Messinian-Lower Pliocene foredeep siliciclastic deposits crop out north and east of the carbonate salient and in piggyback basins [Adamoli et al., 1978]. [ 9 ] The carbonate units overthrust the siliciclastic Miocene deposits (Laga unit). The architecture of the Mesozoic paleomargin exerted a strong control over the geometry of the Gran Sasso salient, as the thrust fronts roughly mimic the trend of the Latium-Abruzzi platform [Calamita et al., 2002, 2003]. Along the E-W front, geological and structural analysis allowed to recognize two main thrust surfaces along which contractional displacement decrease westward, to their tip points located at Mount Corvo (Figures 1 and 3), where en echelon relationships with the western WNW-ESE-trending thrusts and related folds (Mount San Franco) are observed [Calamita et al., 2002, and references therein]. The amount of displacement increases eastward [Ghisetti and Vezzani, 1986], and a maximum shortening of approximately 15 km has been evaluated in the apex area of the salient [Calamita et al., 2003], where the thrusts show spectacular evidence. Thrusting occurred during Upper Messinian-Middle Pliocene times, as documented by the age of thrust top deposits (Figure 4a). Starting from the Early Pleistocene, several normal faults fragmented the chain, partially reactivating prethrusting normal faults. Furthermore, the Gran Sasso salient is characterized by low angle prethrust normal faults rotated during thrusting (Mount Camicia and Mount Jenca [Calamita et al., 2002]), also interpreted as youngeron-older thrusts [Ghisetti and Vezzani, 1991].

4 of 16

B10101


B10101

Figure 4. (a) Schematic geological sections across the central Apennines and (b) line drawing in the southern Apennines, modified after Calamita et al. [2004, 2006]. See Figure 1 for location.

[10] The displacement direction of the Gran Sasso salient has been evaluated by kinematic analysis along the thrust fronts [Ghisetti and Vezzani, 1986; Bigi et al., 1995; Calamita et al., 1995]. Along both the N-S and the E-W limb, the main transport direction is N50 – 60°. There are also secondary transport directions: N80 – 90°, N10° and N140° along the E-W limb; N10 – 20°, N120 – 140° and locally N80 – 90° along the N-S limb. The main transport direction is consistent with the N20°W trend of thrust fronts located north and east of the studied area [Bolis et al., 2003] and suggests a N60 – 70°E trend. The local N10° and N120 –140° kinematics were interpreted as being due to strain partitioning, controlled by the relative magnitudes of principal stresses along oblique thrust ramps [Wilkerson and Marshak, 1991]. However, scattered directions of kinematic trajectories make the transport direction unclear; this could be better constrained using paleomagnetic data.

2.2. Previous Paleomagnetic Data [11] The Gran Sasso Range is an indenter-controlled salient characterized by rotations of variable sign and magnitude (Figure 3). The indenter itself did not experience rotation and both the end points of the arc virtually show lack of rotation, whereas CCW and CW rotations are documented along the E-W and N-S fronts, respectively [Satolli et al., 2005]. Rotations continuously increase along the two orthogonal fronts moving toward the apex and the largest rotations (approximately 80°CCW and 50°CW) are observed in correspondence of the tight block of persistent carbonate platform exposed in the internal part of the arc, suggesting that the rigid carbonate domain acted as a nonrotating indenter during the Neogene. As indicated by the inequality between the maximum CCW and CW rotation values, the indenter translated asymmetrically with respect to the orientation of the indenter margin, approximately

5 of 16

B10101


B10101

Figure 5. Schematic structural map of the Matese-Frosolone Mountains (modified from Calamita et al. [2006]) and locations of paleomagnetic sites. Black dots are the sites retained from this study, light gray dots are the sites discarded from this study, white dots are the sites from Speranza et al. [1998], and dark gray dots are the sites from Iorio and Nardi [1992] and Iorio et al. [1996]. Small black arrows are the paleomagnetic rotations of sites both from this and previous studies (cones represents errors) and the big black arrow is the mean paleomagnetic rotation from the Matese-Frosolone salient. following the N70°E regional direction of tectonic transport. The indenter pushed into the weaker basinal sediments located ahead, causing maximum vertical axis rotations and maximum shortening (approximately 15 km) in correspondence of the arc apex, as suggested also by geological and structural information. The complex rotational pattern documented from the Gran Sasso salient does not correspond to either a primary arc or an orocline. It could be defined as a partially progressive arc, as the present-day arcuate thrust front developed only in part during thrust emplacement, and is strongly inherited from the first-order shape of the Mesozoic platform-to-basin boundary [Calamita et al., 2003]. Rotations occurred synchronously with the emplacement of the outer thrust fault of the system, supporting normal ‘‘insequence’’ propagation of thrust faults.

3. Matese-Frosolone Salient 3.1. Geological Setting [12] The Matese-Frosolone Mountains (Figure 5) form a minor salient structure located in the external southern

Apennines fold-and-thrust belt. It comprises sedimentary successions mainly derived from the Mesozoic passive margin of Adria and involved in the Apennine orogenesis during the Neogene. The preorogenic succession is mainly composed of the Mesozoic Apennine carbonate platform [e.g., D’Argenio et al., 1973; Mostardini and Merlini, 1986; Patacca et al., 1992; Corrado et al., 1998, Pescatore et al., 1999], passing northward into related Meso-Cenozoic slope successions (Molise-Lagonegro basin; we refer the reader to Patacca and Scandone [2007] for a complete discussion on palinspastic relocation of the southern Apennines units). A band of Upper Tortonian siliciclastic foredeep deposits crops out in the footwall of the Sannio units. [13] The Meso-Cenozoic paleodomains have been affected by several tectonic regimes during the Neogene-Quaternary. During the Late Tortonian-Late Pliocene orogenesis, the area was involved in NE-directed thrusting. Between the late Pliocene pro parte. and Early Pleistocene, strike-slip faulting (widespread WSW-ENE to W-E trending left-lateral and N-S trending right lateral) resulted in the dissection of compres-

6 of 16

B10101


B10101

Figure 6. (a – h) Vector diagrams and (i) equal area projection obtained by AF demagnetization, in situ coordinates. Open and solid symbols represent projections onto the vertical and horizontal planes, respectively. Demagnetization step values are expressed in mT. sive structures [Corrado et al., 1997; Scrocca and Tozzi, 1999, and references therein]. Finally, during the Middle Pleistocene, NW-SE trending normal faults resulting from extensional tectonics developed [Patacca et al., 1992; Ferranti, 1997] and caused the orogenic wedge to collapse. As a result, the Matese and Frosolone Mountains grew as a carbonate horst bounded by extensional intramontane basins [Di Bucci et al., 1999]. [14] In the Molise region, the allochthonous units are represented by the Sannio, Apennine platform (or Matese-

Frosolone units) and Molise units, from top to bottom of the orogenic wedge (Figures 1, 4b, and 5). Below the allochthonous units, borehole data and seismic line interpretation indicate the presence of the Apulian units (Figure 4b), characterized by high angle thrusts that breach the shallower basal thrust of the allochthonous units [Calamita et al., 2006, and references therein]. These structural data allowed us to infer that the Matese-Frosolone salient belongs to the thin-skinned tectonic wedge of the southern Apennines allochthonous units.

7 of 16

B10101


B10101

Figure 7. Equal area projections showing the (a) present field viscous components, in situ coordinates, where the white star represents the position of the present dipolar field (D = 0°; I = 60.1°); (b) ChRMs from all sites; (c) Miocene mean directions from the Matese-Frosolone structure. Solid and open symbols represent projections onto the lower and upper hemisphere, respectively. In Figure 7c circles represent sites retained from this work, squares represent data from Speranza et al. [1998], triangle represents data from Iorio et al. [1996], inverted triangle (only in tilt-corrected coordinates) represents data from Iorio and Nardi [1992], and lozenge (only in tilt-corrected coordinates) represents data from Channell [1975].

3.2. New Paleomagnetic Data [15] We performed new paleomagnetic and magnetic anisotropy analyses on eight Messinian-Tortonian sites in the Matese-Frosolone Mountains. Paleomagnetic analysis in this area is hampered by low magnetic quality of outcropping sediments. For this reason, we performed a preliminary campaign to select sites with stable paleomagnetic direc-

tions and measurable intensity. We discarded a priori highly deformed rocks, dolomites, and grainstone/packstones. We collected samples from Messinian clays and Eocene limestones in 27 localities. The NRM of the specimens was measured with a 2G Enterprises DC-SQUID cryogenic magnetometer and the paleomagnetic behavior was tested by alternating field (AF) demagnetization in the paleomag-

8 of 16


B10101

B10101

Table 1. Paleomagnetic Results From the Matese-Frosolone Salienta Site

Age

Latitude N Longitude E

MF01 (1) MF02b (1) MF03b (1) MF04b (1) MF05b (1) MF06 (1) MF07c (1) MF08b (1)

Lower Lower Lower Lower Lower Lower Lower Lower

Miocene Miocene Miocene Miocene Miocene Miocene Miocene Miocene

41°3804900 41°3101100 41°3101100 41°2001600 41°4201200 41°4101000 41°3604700 41°3704000

14°2700000 14°3003000 14°3102500 14°3005800 14°1303600 14°1605000 14°0203600 14°1103700

MT01 (2) MT04 (2) MT07 (2) MT08 (2) Pescorosito (3) Regia Piana (4) Pietraroia (4) South Sbregavitelli (5)

Lower Miocene Lower Miocene Lower Miocene Lower Miocene Lower Miocene Cenomanian/Turonian Albian Aptian

-

-

n/N

Dis

Iis

a95 Strike/Dip

Dtc

Itc

k

New Sampled Sites 13(0)/14 148.2 26.7 10(0)/10 40.6 51.4 9(0)/10 352.6 41.5 12(1)/13 1.2 38.5 13(0)/13 66.2 30.5 12(8)/14 23.4 70.6 13(6)/13 132.9 8.8 14(10)/14 19.4 41.8

150.2 72.2 25.3 8.2 89.7 344.2 131.7 21.0

56.6 48.4 58.9 13.1 71.8 57.7 52.2 22.7

44.6 10.2 2.5 10.3 9.8 72.6 14.5 7.4

6.3 15.9 41.4 14.2 14.0 5.3 11.4 15.8

55/30 50/26 41/31 304/29 144/44 217/22 225/61 298/65

Previous Studies 9 342.5 25.0 7 115.1 41.1 10 147.5 28.4 7 337.8 59.9 24 304.5 36.1 28 42 -

344.9 106.3 153.2 311.2 313.1 322.4 262.8 274.4

37.5 67.5 57.9 54.5 56.6 28.2 41.4 39.9

36.6 53.9 40.6 61.8 172.0 16.1 37.5 72.5

8.6 8.3 7.7 7.7 4.2 7.0 15.2 7.9

-

R

F

31.2 ± 9.3 0.7 ± 5.3 17.2 ± 8.2 0.4 ± 4.6 16.5 ± 8.9 75.1 ± 17.5 28.2 ± 11.7 50.2 ± 10.7 48.3 ± 6.5 17.4 ± 8.4 64.8 ± 17.5 53.2 ± 10.7

19.8 ± 7.0 10.2 ± 6.7 0.6 ± 6.3 2.8 ± 6.3 0.7 ± 3.8 14.8 ± 8.6 0.5 ± 14.7 2.0 ± 10.6

a Here n/N is the number of reliable samples (great circles)/total number of studied samples at a site for new sites or number of reliable samples for previous studies. Dis and Iis and Dtc and Itc are site mean declination and inclination before and after tectonic correction, respectively; k and a95 are statistical parameters after Fisher [1953]. R and F are the site mean rotation and flattening [see Demarest, 1983] relative to coeval D and I African values expected at Matese-Frosolone Mountains (latitude N41°310, longitude E14°270). The reference African poles used are from Besse and Courtillot [2002]. Data are from the following numbers in parentheses: 1, this study; 2, Speranza et al. [1998]; 3, Iorio et al. [1996]; 4, Channell [1975]; 5, Iorio and Nardi [1992]. b Sites discarded for the high value of a95. c Site not considered for the regional mean (see text).

netic laboratory at the Istituto Nazionale di Geofisica e Vulcanologia (INGV) of Rome, Italy. [16] On the basis of the preliminary analysis, we selected eight sites from Messinian-Tortonian clays, characterized by stable paleomagnetic directions and higher intensities. The samples were collected during the summer of 2004 in the outer part of the curved structure of the Matese (sites MF02 to MF04) and Frosolone (sites MF01 and MF05 to MF08) Mountains, from foredeep siliceous deposits in front of the carbonate salient. We collected 10 to 14 samples from each site, spread laterally and vertically in the outcrop in order to average secular variation. Samples were mostly collected using a gas-powered drill; two soft clay sites (MF02 and MF03) were sampled with paleomagnetic sample boxes of standard dimensions (2 2 2 cm). In total, 101 cores were collected and oriented in situ with a magnetic compass. [17] All samples were measured in the shielded room of the paleomagnetic laboratory of the INGV with a 2G DCSQUID cryogenic magnetometer. NRM values range from 4.95 105 to 2.00 103 A/m. Each specimen (standard cylindrical specimens 2.5 cm in diameter and 2 cm in height or standard dimension boxes 2 2 2 cm) was AF demagnetized over 18 steps between 0 mT and 80 mT (up to 95 mT when necessary to completely demagnetize samples) using three coils in line with the magnetometer. [18] Demagnetization data (Figure 6) were plotted on orthogonal demagnetization diagrams [Zijderveld, 1967] and on equal area projections, and the characteristic remanent magnetizations (ChRMs) were evaluated using the principal component analysis [Kirschvink, 1980]. All samples show a viscous component (Figure 7a), usually isolated between 0 mT and 10 mT that shows generally normal polarity (Dis = 347.9°, Iis = 50.1°, a95 = 7.4°) and lies close

to the present field direction (D = 0°, I = 60.1°). Therefore, the viscous component is probably an overprint of the recent field. The ChRM is isolated after the viscous component and until the maximum applied field. A few samples show ChRMs characterized by a linear trend toward the origin (Figures 6a and 6b), however ChRMs usually show an irregular trend (Figures 6c and 6e) and often do not pass through the origin (Figures 6d, 6f, 6g, and 6h). Sometimes, it is not possible to isolate stable components, and demagnetization steps move along remagnetization circles (Figure 6i). For each site, mean directions were computed using Fisher’s [1953] statistic, when only ChRMs components were isolated, or McFadden and McElhinny’s [1988] method, whenever both ChRMs and great circles were recognizable at the site level. [19] Although the sites were selected after the preliminary sampling, results from all eight sites are of very poor quality because of remagnetization, difficulties in isolating stable components and scattering of stable directions at the site level (Figure 7b and Table 1) and we selected only two reliable sites. We discarded site MF08, as almost all its samples are characterized by remagnetization circles, clearly indicating the presence of an unsolved component of magnetization (Figures 6h and 6i). We also discarded sites characterized by highly scattered directions within site and a95 14° (sites MF02, MF03, MF04, and MF05). Furthermore, site MF07 was not used in the regional interpretation as it is characterized by an anomalous eastnortheastward direction. Such a direction could be due to strong deformation caused by the closeness of this site to both the Frosolone and the Meta-Mainarde frontal thrusts. 3.3. Comparison With Data From the Literature [20] The first paleomagnetic studies in the Molise region were carried out in the eastern [Channell, 1975; Channell

9 of 16

B10101


B10101

Figure 8. Diagrams illustrating the magnetic anisotropy of the analyzed samples. (a) Flinn diagram illustrating the relationship between magnetic lineation (k1/k2) and magnetic foliation (k2/k3) and (b) relation between shape factor T and corrected anisotropy degree P’ [Jelinek, 1981].

and Tarling, 1975] and western sectors of the Matese Mountains [Iorio and Nardi, 1992] in Albian bauxites and Lower Cretaceous carbonates, respectively. Most recently, Iorio et al. [1996] applied very stringent rejection criteria to a large number of samples and isolated a well-defined direction from Early/Middle Miocene rocks from Pescorosito, inferring a 40°CCW rotation since Mid-Miocene time. Finally, Speranza et al. [1998], on the basis of 4 new reliable sites (over 13 sampled sites) found that a 35°CCW CCW rotation occurred after Messinian times in the northern sector of the Matese Mountains and in the southern part of Frosolone Mountain. The two new reliable sites sampled in the northern part of Frosolone Mountain show paleomagnetic directions that are consistent with previous results from sites of the same age. [21] In order to evaluate tectonic rotations related to thrust sheet emplacement, tilt-corrected paleomagnetic directions from this study and from the literature were compared with coeval directions expected for the Adriatic foreland (Figure 7c and Table 1). An exhaustive apparent polar wander path from Adria is not yet available, but several studies have demonstrated that Adria has paleomagnetically mirrored the motion of Africa since at least the Permian [e.g., Channell, 1992; Van der Voo, 1993; Muttoni et al., 2001; Rosenbaum et al., 2004]. Therefore, we used the most recent African APWP [Besse and Courtillot, 2002] to evaluate the orogenic rotations of the Matese-Frosolone Mountains with respect to the foreland. Absolute ages from sampled sites were computed using the geomagnetic polarity timescale of Gradstein et al. [2004]; rotation and flattening values were computed according to Demarest [1983]. The new paleomagnetic directions, integrated with previous paleomagnetic studies from the same area, indicate a 40.2°CCW rotation of the salient occurred during the Neogene (according to Speranza et al. [1998]). Directions from two new sites from northern Frosolone Mountain are consistent with previous data from the Matese Mountains and southern Frosolone Mountain, suggesting a homogenous rotation of the entire structure. Furthermore, site

MF06, showing a rotation in agreement with the other sites, suggests that the rotation was induced by the outer buried Frosolone thrust [see Calamita et al., 2006]. 3.4. Magnetic Anisotropy [22] Anisotropy of magnetic susceptibility (AMS) was measured for 9 to 12 specimens from each site with a KLY3S bridge. Measuring magnetic anisotropy allows us to define the magnetic fabric acquired during diagenesis or during successive tectonic strain. [23] The bulk susceptibility is about the same for all specimens and ranges between 162 106 and 416 106 SI. AMS is computed using a least squares best fit method [Jelinek, 1977]. The ellipsoid shape and the degree of anisotropy were evaluated both using a Flinn diagram (Figure 8) and the relationship between corrected anisotropy degree P’ and ellipsoid shape T (Figure 8a and Table 2) [Jelinek, 1981]. [24] The magnetic fabric (Figure 8b) is characterized by an oblate ellipsoid (T > 0), with k3 perpendicular to bedding. All sites show a well-defined magnetic lineation (Figure 9 and Table 2), given by the alignment of the maximum axis k1 with the compressive structural axis. The magnetic lineation indicates that the studied rocks were subjected to mild deformation. [25] The lineation changes direction along the thrust front, and is oriented parallel to principal compressive structures in different sectors of the Matese-Frosolone Mountains. Sites MF02, MF03, MF01 and MF08 have lineation directions gradually changing from NNE-SSW to NW-SE and finally to WSW-ENE, that mimic the orientation of the Frosolone frontal thrust. Site MF04 is characterized by a NE-SW lineation, parallel to the Matese external frontal thrust, while site MF07 shows a NNESSW lineation, parallel to the nearby Meta Mainarde frontal thrust. Site MF06 has a NNE-SSW lineation direction, according to the inferred direction of the buried frontal Frosolone thrust. Finally, site MF05 shows a NW-SE lineation, which cannot be directly related to any structure,

10 of 16


B10101

B10101

Table 2. Anisotropy Parameters for the Analyzed Sitesa Site

n

Susceptibility

L

F

P’

T

D(k1)

I(k1)

a95x

a95y

MF01 MF02 MF03 MF04 MF05 MF06 MF07 MF08

9 9 9 12 11 12 11 10

162 374 369 179 416 296 246 234

1.010 1.002 1.012 1.008 1.032 1.023 1.023 1.015

1.084 1.022 1.043 1.056 1.084 1.058 1.034 1.050

1.104 1.028 1.059 1.070 1.123 1.085 1.058 1.069

0.780 0.800 0.555 0.743 0.437 0.420 0.181 0.529

119.5 27.8 16.1 324.1 122.7 26.4 339.2 66.2

0.2 0.3 4.3 0.2 0.4 0.1 1.4 0.0

7.7 41.2 22.4 32.4 4.8 5.4 5.0 16.0

5.1 9.0 12.1 5.9 1.6 4.3 2.7 7.6

a Here n is the number of samples; susceptibility is the mean susceptibility in 106 SI; L and F are magnetic lineation (k1/k2) and magnetic foliation, respectively (according to Balsley and Buddington [1960] and Stacey et al. [1960]); P’ and T are the corrected anisotropy degree and the ellipsoid shape, respectively (according to Jelinek [1981]); D(k1) and I(k1) are declination and inclination of k1, with the relative a95 along the x and y axis.

but is likely due to strike-slip fault activity or to a local and temporary stress field direction.

4. Discussion 4.1. Differences Between the Central and the Southern Apennines [26] The central and the southern Apennines differ in their paleogeographic domains, stratigraphic successions, structural setting, and geodynamic evolution [Ciarapica and Passeri, 2002; Boccaletti et al., 2005; Finetti et al., 2005a, 2005b; Patacca and Scandone, 2007]. In the central Apennines, the carbonate structural units derived from the deformation of the outer Adria paleomargin crop out and their bounding thrust faults accommodate an amount of shortening of approximately 30 km (according to Boccaletti et al. [2005] and Finetti et al. [2005a]). Instead, in the southern Apennines these units (Apulian units) lie in the footwall of the basal thrust along which the main allochthonous units are far traveled (Liguridi-Sicilidi, inner Carbonate Platform and Lagonegro-Sannio-Molise Units (according to Patacca and Scandone [2007, and references therein])). The allochthonous units are related to the paleodomains (Liguro-Piedmont ocean basin, Inner Carbonate Platform and Lagonegro-Molise basin) that were originally located west of the Apulian Carbonate Platform domain [Patacca and Scandone, 2007, and references therein]. Furthermore, the inner Carbonate Platform units are related to the continental block interposed between the Ionian and Liguro-Piedmont ocean domains (according to Finetti and Del Ben [2005], Ciarapica and Passeri [2002], Gattacceca and Speranza [2002], and Finetti [2005]). Finally, the paleomagnetic data show that differences between the central and the southern Apennines regard also the kind and magnitude of tectonic rotations introduced during the Neogene orogenesis. 4.2. Differences Between the Gran Sasso and the Matese-Frosolone Salients [27] A comparative analysis of the Gran Sasso and the Matese-Frosolone salients pointed out that these salients share some similarities, and yet retain several differences. The structures have similar shapes, with two main E-W and N-S bounding structural trends that define an arcuate thrust front. The paleogeography is very similar, even though they formed and evolved at different times. A platform domain crops out in the inner part of the salients, passing to transitional and pelagic domains northward and eastward.

The evolution from platform to pelagic domain occurred during the Early Jurassic and Upper Triassic in the central and southern Apennines, respectively [Ciarapica and Passeri, 2002]. The two salients have had different styles of tectonic deformation (Figures 1 and 4). Orogenic shortening occurred during the Pliocene for the MateseFrosolone salient and during the Messinian for the Gran Sasso salient, as documented by the ages of foredeep deposits. In addition, approximately 15 km of shortening were accommodates by thrust related structures at the Gran Sasso [Calamita et al., 2002; Satolli et al., 2005], while the Matese-Simbruini thrust front experienced higher amount of shortening (approximately 80 km), that yet progressively decreases toward the Simbruini Mountains (approximately 15 km), as documented by data from the Trevi well [Pieri, 1966; Scrocca and Tozzi, 1999; Patacca and Scandone, 2007]. Paleomagnetic data and geological structural evidence indicate that the Gran Sasso salient is rooted westward and southward, whereas the Matese-Frosolone salient, which instead belongs to the southern Apennines allochthonous units, was strongly rotated during its passive translation by thrusting onto Apulian carbonates units. 4.3. Kinematic Evolution of the Central Apennines [28] Combined geological, structural and paleomagnetic investigations carried out in this work, and integrated with data from the literature (e.g., recent palinspastic reconstruction proposed by Ciarapica and Passeri [2002] and Patacca and Scandone [2007]), allowed us to reconstruct a kinematic model related to the Tortonian-Quaternary evolution of the central Apennines thrust system (Figure 10). The central Apennines is here regarded as the junction zone between the northern Apennines Arc and the southern Apennines-Calabrian Arc, that were developed during the Tortonian-Early Pliocene time interval. Here, the thrust sheets belonging to the northern Apennines Arc are characterized by CW rotations, with northward increase in the amount of shortening up to approximately 15 –20 km (i.e., Olevano-Antrodoco-Sibillini thrust, according to Mazzoli et al. [2005]), while minor salients show strong CW and CCW paleomagnetic rotations confined near the apex and corresponding to maximum shortening of approximately 15 km (e.g., Gran Sasso salient, according to Satolli et al. [2005]). Conversely, southwestward increase in the amount of shortening is documented in the southern Apennines, up to 80 km in the Matese-Frosolone salient (Figure 4b), in agreement with the homogeneous CCW paleomagnetic rotation. Thus, according to paleomagnetic data and kinematic

11 of 16

B10101


Figure 9. Equal area projections showing the magnetic fabric in the studied sediments. Solid and open symbols represent projections onto the lower and upper hemisphere, respectively. Ellipses indicate the semiangle of confidence around mean susceptibility axes.

12 of 16

B10101

B10101


Figure 10

13 of 16

B10101

B10101


reconstructions (Figure 10), the Gran Sasso salient is part of the northern Apennines Arc, while the Matese-Frosolone structure belongs to the southern Apennines-Calabrian Arc (Figure 10d). [29] Looking at paleomagnetic data, the thrust sheets belonging to southern Apennines-Calabria Arc can be extended northward to the Simbruini-Ernici Mountains. As a relevant consequence, the Sangro-Volturno line should not be interpreted as a major tectonic separation between the northern Apennines Arc and the southern Apennines-Calabrian Arc. This tectonic feature represents the oblique ramp of the Plio-Quaternary frontal thrust of the central Apennines (e.g., Maiella and Morrone units), that is buried by the tectonic wedge of the allochthonous units in the southern Apennines (Apulian chain) (Figure 10c). [ 30 ] The northwestward limit of the Molise units, corresponding to the Sangro-Volturno line, could thus represent the oblique ramp of the allochthonous sole thrust developed in the northern sector of the Lagonegro-Molise basin (Figure 10a), detached and thrust onto the Apulian carbonate platform (Figure 10c) (according to Calamita et al. [2007]). 4.4. Causes of the Observed Rotations [31] The formation of the Apennine orogen is driven by subduction rollback [e.g., Malinverno and Ryan, 1986; Patacca and Scandone, 1989; Doglioni, 1991; Rosenbaum and Lister, 2004]. Nevertheless, the Adria paleomargin architecture caused a slab detachment in the central-southern Apennines (documented in the tomographic images by the presence of a slab window above 250 km depth [Lucente et al., 1999; Lucente and Speranza, 2001]) that led to the formation of the major arcs of the northern Apennines and southern Apennines-Calabrian Arc. [32] We propose that homogeneous CCW rotation in the Matese-Frosolone salient represents the northern area influenced by the slab subducting under the southern ApenninesCalabrian Arc. Conversely, paleomagnetic rotations in the Gran Sasso Range were probably driven by an orogenparallel compression and related lateral extrusion mechanism [Mantovani et al., 2000; Schellart and Lister, 2004; Boccaletti et al., 2005]. Furthermore, in both salients the paleomagnetic rotation was also strongly influenced by a different structure of the paleogeographic domains. In the Matese-Frosolone salient, the presence of the LagonegroMolise basin, floored by attenuated crust (oceanic or atten-

B10101

uated continental crust) allowed the occurrence of homogeneous CCW rotations in the southern Apennines units, with thrusts that accommodated high shortening values. Conversely, the rotations in the Gran Sasso salient were strongly influenced by the Mesozoic paleomargin architecture, in a context of less significant shortening accommodated by thrusts (Figure 10).

5. Conclusions [33] The Apennines describe two major Arcs characterized by CCW rotations in the northern sector and CW rotations in the southern sector (Figure 2). In fact, the northern Apennines Arc is characterized by CCW rotations in the Emilia-Romagna and Marche regions, changing to CW rotations toward the central Apennines. Similarly, the southern Apennines-Calabrian Arc is characterized by CCW rotation in the southern Apennines, changing to strong CW rotations in Sicily. [34] Paleomagnetic and magnetic anisotropy analyses performed over eight new sites from the Matese-Frosolone salient confirm that this salient underwent a homogeneous approximately 40°CCW rotation. The integration of geological-structural and paleomagnetic information from the Gran Sasso and the Matese-Frosolone salients allowed us to reconstruct a kinematic model for the Tortonian-Quaternary evolution of the central Apennines, i.e., the junction zone between the northern Apennines Arc and southern Apennines-Calabrian Arc (Figure 10). [35] We propose the use of paleomagnetic rotations as a reliable tool to ascribe the Gran Sasso to the northern Apennines Arc and the Matese-Frosolone salients to the southern Apennines-Calabrian Arc. The different kind and amount of paleomagnetic rotations documented in the two analyzed salients may be ascribed to different driving mechanisms and to the different paleogeographic-structural heritage. In particular, the different structural settings and paleomagnetic rotations of the thrust sheets belonging to the northern Apennines Arc or to the southern ApenninesCalabrian Arc may be related to the architecture of the Adria paleomargin, characterized in the southern sector by the presence of the Lagonegro-Molise basin, which belongs to the Ionian Ocean paleodomain (according to Ciarapica and Passeri [2002] and Finetti [2005]) or to the Adria continental paleomargin (according to Mostardini and Merlini [1986]).

Figure 10. Kinematic sketch showing the Tortonian-Quaternary evolution of the central Apennines thrust system, the junction zone between the northern Apennines Arc and southern Apennines-Calabrian Arc. (a) Paleogeographic scheme (inspired by Ciarapica and Passeri [2002] and Patacca and Scandone [2007]) with location and age of the main thrusts belonging to the northern Apennines Arc (blue) or to the southern Apennines-Calabrian Arc (green). L-A-A, LepiniAusoni-Aurunci carbonate platform; S-E, Simbruini-Ernici carbonate platform; LAM-B, Lagonegro-Molise basin; SAB-B, Sabina slope-to-basin; UM-B, Umbria-Marche slope-to-basin; LA-P, Lazio-Abruzzi carbonate platform; PA-P, Apulian carbonate platform. (b) Structural setting related to Tortonian-Quaternary evolution, showing the control of the paleomargin architecture on geometry, kinematic, and tectonic style of the thrust sheets belonging to the northern Apennines Arc or to the southern Apennines-Calabrian Arc and of their minor structures (the Gran Sasso and Matese-Frosolone salients). (c) Palinspastic reconstruction of the central and southern Apennines units (redrawn from Patacca and Scandone [2007]). (d) Tectonic sketch of Italy showing the separation between the northern Apennines Arc (dark gray shadowed area) and the southern Apennines-Calabrian Arc (light gray shadowed area). O-A-L, Olevano-Antrodoco oblique thrust ramp; S-V-L, Sangro-Volturno oblique thrust ramp. 14 of 16

B10101


[36] Acknowledgments. We thank the Istituto Nazionale di Geofisica and Vulcanologia of Rome for allowing us to measure samples in their paleomagnetic laboratory. We would like to sincerely thank the Associate Editor W. P. Schellart and the reviewers E. Patacca and E. Tavarnelli who greatly contributed to improving the quality of this manuscript. The first version of this manuscript benefited from the careful reviews of G. Muttoni. This work was supported financially by ex 60% grants awarded to F. Calamita.

References Adamoli, L., T. Bertini, M. Chiocchini, G. Deiana, A. Mancinelli, U. Pieruccini, and A. Romano (1978), Ricerche geologiche sul Mesozoico del Gran Sasso d’Italia (Abruzzo). Parte II: Evoluzione tettonico-sedimentaria dal trias- superiore al Cretaceo inferiore dell’area compresa tra il Corno Grande e S. Stefano di Sessanio (F. 140 Teramo), Studi Geol. Camerti, 4, 7 – 18. Alvarez, W. (1990), Pattern of extensional faulting in pelagic carbonates of the Umbria-Marche Apennines of the central Italy, Geology, 18, 407 – 410, doi:10.1130/0091-7613(1990)0182.3.CO;2.. Balsley, J. R., and A. F. Buddington (1960), Magnetic susceptibility anisotropy and fabric of some Adirondack granites and orthogneisses, Am. J. Sci., 258(A), 6 – 20. Ben Avraham, Z., M. Boccaletti, G. Cello, M. Grasso, F. Lentini, L. Torelli, and L. Tortorici (1990), Principali domini strutturali originatesi dalla collisione neogenico-quaternaria nel Mediterraneo centrale, Mem. Soc. Geol. Ital., 45, 453 – 462. Besse, J., and V. Courtillot (2002), Apparent and true polar wander and the geometry of the geomagnetic field over the last 200 Myr, J. Geophys. Res., 107(B11), 2300, doi:10.1029/2000JB000050. Bigi, S., F. Calamita, and E. Centamore (1995), Caratteristiche geologicostrutturali dell’area abruzzese ad oriente del Gran Sasso, Studi Geol. Camerti, 1995/2, 67 – 76. Boccaletti, M., et al. (1990), Palinspastic restoration and paleogeographic reconstruction of the peri-Tyrrhenian area during the Neogene, Palaeogeogr. Palaeoclimatol. Palaeoecol., 77, 41 – 50, doi:10.1016/00310182(90)90097-Q. Boccaletti, M., F. Calamita, and M. G. Viandante (2005), La Neo-Catena litosferica appenninica nata a partire dal Pliocene inferiore come espressione della convergenza Africa-Europa, Boll. Soc. Geol. Ital., 124, 87 – 105. Bolis, G., S. Carruba, R. Casnedi, C. R. Perotti, A. Ravaglia, and M. Tornaghi (2003), Compressional tectonics overprinting extensional structures in the Abruzzo Periadriatic Foredeep (Central Italy) during Pliocene times, Boll. Soc. Geol. Ital., 122, 251 – 266. Calamita, F., E. Centamore, G. Deiana, and M. Ridolfi (1995), Caratterizzazione strutturale dell’unita` della Laga (area marchigiano-abruzzese esterna), Studi Geol. Camerti, 1995/1, 171 – 182. Calamita, F., W. Paltrinieri, M. Pelorosso, V. Scisciani, and E. Tavarnelli (2002), Inherited Mesozoic architecture of the Adria continental palaeomargin in the Neogene central Apennines orogenic system, Italy, Boll. Soc. Geol. Ital., 122, 307 – 318. Calamita, F., M. Pelorosso, and S. Satolli (2003), The role of the Adria Mesozoic paleomargin architecture on the Gran Sasso d’Italia orogenic system (central Apennines), Boll. Soc. Geol. Ital., 122, 337 – 349. Calamita, F., M. G. Viandante, and K. Hegarty (2004), Pliocene-Quaternary burial/exhumation paths of the central Apennines (Italy): Implications for the definition of the deep structure of the belt, Boll. Soc. Geol. Ital., 123, 503 – 512. Calamita, F., W. Paltrinieri, P. Esestime, and M. G. Viandante (2006), Assetto strutturale crostale dell’Appennino centro-meridionale, Rend. Soc. Geol. Ital. Nuova Ser., 2, 103 – 107. Calamita, F., M. G. Viandante, P. Esestime, W. Paltrinieri, and V. Scisciani (2007), The control of the Adria paleomargin architecture on the pre and post-Early Pliocene evolution of the central-southern Apennines, Rend. Soc. Geol. Ital. Nuova Ser., 4, 170 – 173. Carey, W. (1955), The orocline concept in geotectonics, Pap. Proc. R. Soc. Tasmania, 89, 255 – 289. Cello, G., N. Martini, W. Paltrinieri, and L. Tortorici (1989), Structural styles in the frontal zones of the southern Apennines, Italy: An example from the Molise district, Tectonics, 8(4), 753 – 768, doi:10.1029/ TC008i004p00753.. Channell, J. E. T. (1975), Paleomagnetic studies in Italy and Greece and the evolution of the mediterranean region, Ph.D. thesis, Newcastle Univ., Newcastle upon Tyne, U. K. Channell, J. E. T. (1992), Paleomagnetic data from Umbria (Italy): Implications for the rotation of Adria and Mesozoic apparent polar wander paths, Tectonophysics, 216, 365 – 378, doi:10.1016/0040-1951(92)90406-V. Channell, J. E. T., and D. H. Tarling (1975), Palaeomagnetism and the rotation of Italy, Earth Planet. Sci. Lett., 25, 177 – 188, doi:10.1016/ 0012-821X(75)90194-6.

B10101

Channell, J. E. T., W. Lowrie, F. Medizza, and W. Alvarez (1978), Paleomagnetism and tectonics in Umbria, Italy, Earth Planet. Sci. Lett., 39, 199 – 210, doi:10.1016/0012-821X(78)90196-6. Channell, J. E. T., J. S. Oldow, R. Catalano, and B. D’Argenio (1990), Paleomagnetically determined rotations in the western Sicilian fold and thrust belt, Tectonics, 9(4), 641 – 660, doi:10.1029/TC009i004p00641. Ciarapica, G., and L. Passeri (2002), The palaeogeographic duplicity of the Apennines, Boll. Soc. Geol. Ital., 1, 67 – 75. Corrado, S., D. Di Bucci, G. Naso, and R. W. H. Butler (1997), Thrusting and strike-slip tectonics in the Alto Molise region (Italy): Implications for the Neogene-Quaternary evolution of the central Apennine orogenic system, J. Geol. Soc., 154, 679 – 688, doi:10.1144/gsjgs.154.4.0679. Corrado, S., D. Di Bucci, G. Naso, and A. V. Damiani (1998), Rapporti tra le grandi unita` stratigrafico-strutturali delle aree esterne dell’Appennino centrale: Evoluzione geologica dell’Alto Molise, Boll. Soc. Geol. Ital., 117, 761 – 776. Corrado, S., C. Invernizzi, and S. Mazzoli (2002), Tectonic burial and exhumation in a foreland fold and thrust belt: The Monte Alpi case history (Southern Apennines, Italy), Geodin. Acta, 15, 159 – 177, doi:10.1016/S0985-3111(02)01086-0. D’Argenio, B., and W. Alvarez (1980), Stratigraphic evidence for crustal thickness changes on the southern Tethyan margin during the Alpine cycle, Geol. Soc. Am. Bull., 91, 681 – 689, doi:10.1130/00167606(1980)912.0.CO;2. D’Argenio, B., T. Pescatore, and P. Scandone (1973), Schema geologico dell’Appennino meridionale (Campania e Lucania), Quad. Accad. Naz. Lincei, 183, 49 – 72. Demarest, H. H., Jr. (1983), Error analysis for the determination of tectonic rotation from paleomagnetic data, J. Geophys. Res., 88(B5), 4321 – 4328, doi:10.1029/JB088iB05p04321. Di Bucci, D., S. Corrado, G. Naso, M. Parotto, and A. Praturlon (1999), Evoluzione tettonica neogenico-quaternaria dell’area molisana, Boll. Soc. Geol. Ital., 118, 13 – 30. Doglioni, C. (1991), A proposal for the kinematic modelling of W-dipping subductions – possible applications to the Tyrrhenian-Apennines system, Terra Nova, 3, 423 – 434, doi:10.1111/j.1365-3121.1991.tb00172.x. Elter, P., G. Giglia, M. Tongiorgi, and L. Trevisan (1975), Tensional and compressional areas in recent (Tortonian to Present) evolution of north Apennines, Bol. Geofis. Teor. Appl., 17, 3 – 18. Ferranti, L. (1997), Tettonica tardo pliocenica-quaternaria dei Monti del Matese (Appennino meridionale): Raccorciamenti tardivi e distensione ‘‘neotettonia’’, Quaternario, 10(2), 503 – 506. Finetti, I. R. (2005), Ionian and Alpine Neotethyan oceans opening, in CROP Project: Deep Seismic Exploration of the Central Mediterranean and Italy, edited by I. R. Finetti, pp. 103 – 107, Elsevier, New York. Finetti, I. R., and A. Del Ben (2005), Ionian Tethys lithosphere roll-back sinking and back-arc Tyrrhenian opening from new CROP seismic data, in CROP Project: Deep Seismic Exploration of the Central Mediterranean and Italy, edited by I. R. Finetti, pp. 483 – 503, Elsevier, New York. Finetti, I. R., F. Calamita, U. Crescenti, A. Del Ben, E. Forlin, M. Pipan, G. Rusciadelli, and V. Scisciani (2005a), Crustal geological section across central Italy from the Corsica Basin to the Adriatic Sea based on geological and CROP seismic data, in CROP Project: Deep Seismic Exploration of the Central Mediterranean and Italy, edited by I. R. Finetti, pp. 159 – 195, Elsevier, New York. Finetti, I. R., F. Lentini, S. Carbone, A. Del Ben, A. Di Stefano, P. Guarnieri, M. Pipan, and A. Prizzon (2005b), Crustal tectono-stratigraphy and geodynamic of the southern Apennines from CROP and other integrated geophysical-geological data, in CROP Project: Deep Seismic Exploration of the Central Mediterranean and Italy edited by I. R. Finetti, pp. 225 – 262, Elsevier, New York. Fisher, R. A. (1953), Dispersion on a sphere, Proc. R. Soc. London Ser. A, 217, 295 – 305. Gattacceca, J., and F. Speranza (2002), Paleomagnetism of Jurassic to Miocene sediments from the Apenninic carbonate platform (southern Apennines, Italy): Evidence for a 60° counterclockwise Miocene rotation, Earth Planet. Sci. Lett., 201, 19 – 34, doi:10.1016/S0012-821X(02)00686-6. Ghisetti, F., and L. Vezzani (1983), Deformazioni pellicolari mioceniche e plioceniche nei domini strutturali esterni dell’Appennino centro-meridionale (Maiella ed Arco Morrone-Gran Sasso), Mem. Soc. Geol. Ital., 26, 563 – 577. Ghisetti, F., and L. Vezzani (1986), Assetto geometrico ed evoluzione strutturale della catena del Gran Sasso tra Vado di Siella e Vado di Corno, Boll. Soc. Geol. Ital., 105, 131 – 171. Ghisetti, F., and L. Vezzani (1991), Thrust belt development in the central Apennines (Italy): Northward polarity of thrusting and out-of-sequence deformations in the Gran Sasso chain, Tectonics, 10(5), 904 – 919, doi:10.1029/91TC00902.. Gradstein, F. M., et al. (2004), A Geologic Time Scale 2004, Cambridge Univ. Press, New York.

15 of 16

B10101


Hirt, A. M., and W. Lowrie (1988), Paleomagnetism of the Umbrian-Marches orogenic belt, Tectonophysics, 146, 91 – 103, doi:10.1016/00401951(88)90084-4. Iorio, M., and G. Nardi (1992), Studi paleomagnetici sul Mesozoico del Matese Occidentale, Mem. Soc. Geol. Ital., 41, 1253 – 1261. Iorio, M., G. Nardi, D. Pierattini, and D. H. Tarling (1996), Palaeomagnetic evidence of block rotations in the Matese Mountains, Spec. Publ. Geol. Soc. London, 105, 133 – 139. Jackson, K. C. (1990), A paleomagnetic study of Apennine thrusts, Italy: Monte Maiella and Monte Raparo, Tectonophysics, 178, 231 – 240, doi:10.1016/0040-1951(90)90149-3. Jelinek, V. (1977), The Statistical Theory of Measuring Anisotropy Of Magnetic Susceptibility of Rocks and its Application, 88 pp., Geofyzika, Brno, Czech Republic. Jelinek, V. (1981), Characterization of the magnetic fabric of rocks, Tectonophysics, 79, T63 – T67, doi:10.1016/0040-1951(81)90110-4. Kirschvink, J. L. (1980), The least squares line and plane and the analysis of paleomagnetic data, Geophys. J.R. Astron. Soc., 62, 699 – 718. Lentini, F., S. Carbone, A. Di Stefano, and P. Guarnieri (2002), Stratigraphical and structural constraints in the Lucanian Apennines (southern Italy): Tools for reconstructing the geological evolution, J. Geodyn., 34, 141 – 158, doi:10.1016/S0264-3707(02)00031-5. Locardi, E. (1982), Individuazione di strutture sismogenetiche dall’esame dell’evoluzione vulcano-tettonica dell’Appennino e del Tirreno, Mem. Soc. Geol. Ital., 24, 569 – 596. Lucente, F. P., and F. Speranza (2001), Belt bending driven by lateral bending of subducting lithospheric slab: Geophysical evidences from the northern Apennines (Italy), Tectonophysics, 337, 53 – 64, doi:10.1016/S0040-1951(00)00286-9. Lucente, F. P., C. Chiarabba, G. B. Cimini, and D. Giardini (1999), Tomographic constraints on the geodynamic evolution of the Italian region, J. Geophys. Res., 104, 20,307 – 20,327, doi:10.1029/1999JB900147. Malinverno, A., and W. B. F. Ryan (1986), Extension on the Tyrrhenian Sea and shortening in the Apennines as result of arc migration driven by sinking of the lithosphere, Tectonics, 5, 227 – 245, doi:10.1029/ TC005i002p00227. Mantovani, E., M. Viti, D. Albarello, C. Tamburelli, D. Babbucci, and N. Cenni (2000), Role of kinematically induced horizontal forces in Mediterranean tectonics: Insights from numerical modeling, J. Geodyn., 30, 287 – 320, doi:10.1016/S0264-3707(99)00067-8. Marshak, S. (1988), Kinematics of orocline and arc formation in thin-skinned orogens, Tectonics, 7(1), 73 – 86, doi:10.1029/TC007i001p00073. Marton, P., and M. D’Andrea (1992), Paleomagnetically inferred rotations of the Abruzzi and Northwestern Umbria, Tectonophysics, 202, 43 – 53, doi:10.1016/0040-1951(92)90454-E. Mattei, M., R. Funiciello, and C. Kissel (1995), Paleomagnetic and structural evidence for Neogene block rotations in the central Apennines, Italy, J. Geophys. Res., 100, 17,863 – 17,883, doi:10.1029/95JB00864. Mattei, M., C. Kissel, L. Sagnotti, F. Funiciello, and C. Faccenna (1996), Lack of upper Miocene to present rotation in the Northern Tyrrhenian margin (Italy): A constraint on geodynamic evolution, Spec. Publ. Geol. Soc. London, 105, 141 – 146. Mazzoli, S., P. P. Pierantoni, F. Borraccini, W. Paltrinieri, and G. Deiana (2005), Geometry, segmentation pattern and displacement variations along a major Apennine thrust zone, central Italy, J. Struct. Geol., 27, 1940 – 1953, doi:10.1016/j.jsg.2005.06.002. McFadden, P. L., and M. W. McElhinny (1988), The combined analysis of remagnetization circles and direct observations in palaeomagnetism, Earth Planet. Sci. Lett. , 87, 161 – 172, doi:10.1016/0012821X(88)90072-6. Miser, H. D. (1932), Oklahoma structural salient of the Ouachita Mountains, Geol. Soc. Am. Bull., 43, 138. Mostardini, F., and S. Merlini (1986), Appennino Centro-Meridionale: Sezioni geologiche e proposta di modello strutturale, Mem. Soc. Geol. Ital., 35, 177 – 202. Muttoni, G., A. Argnani, D. V. Kent, N. Abrahamsen, and U. Cibin (1998), Paleomagnetic evidence for Neogene tectonic rotations in the northern Apennines, Italy, Earth Planet. Sci. Lett., 154, 25 – 40, doi:10.1016/ S0012-821X(97)00183-0. Muttoni, G., E. Garzanti, L. Alfonsi, S. Cirilli, D. Germani, and W. Lowrie (2001), Motion of Africa and Adria since the Permian: Paleomagnetic and paleoclimatic constraints from northern Libya, Earth Planet. Sci. Lett., 192, 159 – 174, doi:10.1016/S0012-821X(01)00439-3. Parotto, M., and A. Praturlon (1975), Geological summary of the central Apennines, Quad. Ric. Sci., 90, 257 – 306.

B10101

Patacca, E., and P. Scandone (1989), Post-Tortonian mountain building in the Apennines: The role of the passive sinking of a relic lithospheric slab, in The Lithosphere in Italy, Adv. Earth Sci. Res. Ser., vol. 80, edited by A. Boriani et al., pp. 157 – 176, Atti Conv. Accad. Lincei, Rome. Patacca, E., and P. Scandone (2007), Geology of the southern Apennines, Boll. Soc. Geol. Ital., 7, 75 – 119. Patacca, E., R. Sartori, and P. Scandone (1990), Tyrrhenian basin and Apenninic arcs: Kinematic relations since late Tortonian times, Mem. Soc. Geol. Ital., 45, 425 – 451. Patacca, E., P. Scandone, M. Bellatalla, N. Perilli, and U. Santini (1992), La zona di giunzione tra l’arco appenninico settentrionale e l’arco appenninico meridionale nell’Abruzzo e nel Molise, Studi Geol. Camerti, 1991/2, 417 – 441. Pescatore, T., P. Renda, M. Schiattarella, and M. Tramutoli (1999), Stratigrafic and structural relashionship between Meso-Cenozoic Lagonegro basin and coeval carbonate platforms in southern Apennines, Italy, Tectonophysics, 315, 269 – 286, doi:10.1016/S0040-1951(99)00278-4. Pieri, M. (1966), Tentativo di ricostruzione peleogeografico-strutturale dell’Italia centro-meridionale, Geol. Rom., 5, 407 – 424. Rosenbaum, G., and G. S. Lister (2004), Formation of arcuate orogenic belts in the western Mediterraneran region, in Orogenic Curvature: Integrating Paleomagnetic and Structural Analyses, edited by A. J. Sussman, and A. B. Weil, pp. 41 – 56, Geol. Soc. of Am., Boulder, Colo. Rosenbaum, G., G. S. Lister, and C. Duboz (2004), The Mesozoic and Cenozoic motion of Adria (central Mediterranean): A review of constraints and limitations, Geodin. Acta, 17(2), 125 – 139, doi:10.3166/ ga.17.125-139. Satolli, S., F. Speranza, and F. Calamita (2005), Paleomagnetism of the Gran Sasso Range salient (central Apennines, Italy): Pattern of orogenic rotations due to translation of a massive carbonate indenter, Tectonics, 24, TC4019, doi:10.1029/2004TC001771. Scheepers, P. J. J., and C. G. Langereis (1994), Paleomagnetic evidence for counter-clockwise rotations in the southern Apennines fold-and-thrust belt during the Late Pliocene and middle Pleistocene, Tectonophysics, 239, 43 – 59, doi:10.1016/0040-1951(94)90106-6. Schellart, W. P., and G. S. Lister (2004), Tectonic models for the formation of arc-shaped convergent zones and backarc basins, in Orogenic Curvature: Integrating Paleomagnetic and Structural Analyses, edited by A. J. Sussman and A. B. Weil, pp. 237 – 258, Geol. Soc. of Am., Boulder, Colo. Scrocca, D., and M. Tozzi (1999), Tettonogenesi mio-pliocenica dell’Appennino Molisano, Boll. Soc. Geol. Ital., 118, 255 – 286. Speranza, F., L. Sagnotti, and M. Mattei (1997), Tectonics of the UmbriaMarche-Romagna Arc (central northern Apennines, Italy): New paleomagnetic constraints, J. Geophys. Res., 102(B2), 3153 – 3166, doi:10.1029/ 96JB03116. Speranza, F., M. Mattei, G. Naso, D. Di Bucci, and S. Corrado (1998), Neogene-Quaternary evolution of the central Apennine orogenic system (Italy): A structural and paleomagnetic approach in the Molise region, Tectonophysics, 299, 143 – 157, doi:10.1016/S0040-1951(98)00202-9. Speranza, F., R. Maniscalco, and M. Grasso (2003), Pattern of orogenic rotations in central-eastern Sicily: Implications for the chronology of the Tyrrhenian Sea spreading, J. Geol. Soc., 160, 183 – 195. Stacey, F. D., G. Joplin, and J. Lindsay (1960), Magnetic anisotropy and fabrics of some foliated rocks from S.E. Australia, Geofis. Pura Appl., 47, 30 – 40, doi:10.1007/BF01992481. Van der Voo, R. (1993), Paleomagnetism of the Atlantic, Tethys and Iapetus Oceans, 411 pp., Cambridge Univ. Press, Cambridge, U. K. Weil, A. B., and A. J. Sussman (2004), Classifying curved orogens based on timing relationships between structural development and vertical-axis rotations, in Orogenic Curvature: Integrating Paleomagnetic and Structural Analyses, edited by A. J. Sussman and A. B. Weil, pp. 1 – 15, Geol. Soc. of Am., Boulder, Colo. Wilkerson, M. S., and S. Marshak (1991), Factors controlling slip-lineation orientation on thrust-fault planes, Tectonophysics, 196, 203 – 208, doi:10.1016/0040-1951(91)90297-6. Zijderveld, J. D. A. (1967), AC demagnetization of rocks: Analysis of results, in Methods in Palaeomagnetism, edited by S. K. Runcorn, K. M. Creer, and D. W. Collinson, pp. 254 – 286, Elsevier, New York.

F. Calamita and S. Satolli, Dipartimento di Scienze della Terra, Universita` G. d’Annunzio di Chieti-Pescara, Via dei Vestini 30, I-66013 Chieti Scalo, Italy. ([email protected])

16 of 16