Burial-Deformation History of Folded Rocks Unraveled by Fracture Analysis, Stylolite Paleopiezometry and Vein Cement Geochemistry: A Case Study in the Cingoli Anticline (Umbria-Marche, Northern Apennines)

Abstract

Unravelling the burial-deformation history of sedimentary rocks is prerequisite information to understand the regional tectonic, sedimentary, thermal, and fluid-flow evolution of foreland basins. We use a combination of microstructural analysis, stylolites paleopiezometry, and paleofluid geochemistry to reconstruct the burial-deformation history of the Meso-Cenozoic carbonate sequence of the Cingoli Anticline (Northern Apennines, central Italy). Four major sets of mesostructures were linked to the regional deformation sequence: (i) pre-folding foreland flexure/forebulge; (ii) fold-scale layer-parallel shortening under a N045 σ1; (iii) syn-folding curvature of which the variable trend between the north and the south of the anticline is consistent with the arcuate shape of the anticline; (iv) the late stage of fold tightening. The maximum depth experienced by the strata prior to contraction, up to 1850 m, was quantified by sedimentary stylolite paleopiezometry and projected on the reconstructed burial curve to assess the timing of the contraction. As isotope geochemistry points towards fluid precipitation at thermal equilibrium, the carbonate clumped isotope thermometry (Δ47) considered for each fracture set yields the absolute timing of the development and exhumation of the Cingoli Anticline: layer-parallel shortening occurred from ~6.3 to 5.8 Ma, followed by fold growth that lasted from ~5.8 to 3.9 Ma.

Pre-folding fracturing in a foredeep environment: insights from the Carseolani Mountains (central Apennines, Italy)

“…The main peculiarity of our study area is hence the orientation of the pressure-solution cleavage, which is neither sub-vertical nor orthogonal to bedding, contrary to what is reported for other anticlines in the northern Apennines (e.g. Beaudoin et al 2020;Labeur et al 2021). Such observation suggests that pressure-solution cleavage is not related to layer-parallel shortening or to late-folding tightening.…”

“…The simplest criterion to distinguish pre-folding from syn-folding joints is based on the analyses of joint orientation with respect to the orientation of the fold axis. Syn-folding, bending-related structures are oriented parallel and orthogonal to the fold axis, whereas prefolding structures can develop oblique to the fold axis (Lash & Engelder, 2007;Tavani et al 2015;Labeur et al 2021), as they reflect the direction of pre-folding layer-parallel shortening or the foreland flexure direction, both of which may be oblique with respect to the direction of compressional strain during folding. Since folds are generally elongated parallel to the trend of the hosting foredeep-belt system, the distinction between pre-folding and syn-folding joints can be challenging.…”

Dating folding beyond folding, from layer-parallel shortening to fold tightening, using mesostructures: lessons from the Apennines, Pyrenees, and Rocky Mountains

“…In this paper, we focus on easily recognizable mesostructures that develop in the same contractional stage and under the same regional trend of horizontal shortening as folding. We report neither on microstructures such as calcite twins (Craddock et al, 1993;Lacombe et al, 2007Lacombe et al, , 2009Rocher et al, 1996;Hnat et al, 2011; see review by Lacombe, 2010) nor on rock physical properties such as anisotropy of magnetic susceptibility (e.g. Aubourg et al, 2010;Amrouch et al, 2010b;Branellec et al, 2015;Weil and Yonkee, 2012).…”

Calcite Twin Formation, Measurement and Use as Stress–Strain Indicators: A Review of Progress over the Last Decade

“…Such finding led [158] to propose an analytical relationship linking the applied differential stress, the mean stress, the elastic properties of the rock (Young modulus and Poisson coefficient) and the surface energy at the solid-fluid interface to the characteristic length (referred to as the cross-over length, Lc) at which roughness analysis switches from a Hurst coefficient related to elastic energy to a Hurst coefficient related to surface energy (Figure 13C). Since then, the Stylolite Roughness Inversion Technique (SRIT) has successfully been applied to sedimentary stylolites from various geological settings, from simple ones [159][160][161] to more complex ones [103,[162][163][164][165]. Assuming that sedimentary stylolites formed under a vertical maximum principal stress σ 1 with the horizontal stress being isotropic (σ 2 = σ 3 ), applying SRIT to sedimentary stylolites provides a reliable way to access the magnitude of the past vertical stress, hence the burial depth, at the moment the stylolite stop dissolving, free from any considerations upon fluid pressure or geothermal gradient [91,160] (Figure 13B,C).…”

“…Ongoing and future development combining both paleopiezometers mainly rely on the capability of SRIT to constrain the σ v prevailing at the time of deformation. A first promising development is to better constrain the timing at which σ 1 switches from a vertical to a horizontal attitude by combining the SRIT results from a population of sedimentary stylolites and burial models (Figure 13A, [164,165]). This approach constrains the range of depths at which twinning occurred under a horizontal σ 1 , along with providing indirectly the absolute timing of the contractional event (Figure 13A).…”