Balancing cross sections with kinematic constraints: The Dolomites (northern Italy)

Abstract

Abstract. Balancing of structural cross sections is often hindered by a limited database or tectonic complications. In such cases, kinematic constraints may help to better constrain the construction of a cross section and its extrapolation to depth. The kinematic implications of a known structure (generally at the surface) have to be considered for the unknown structure and for the internal consistency of a cross section. A key point is the quantification of shortening of the known structure. The extrapolation of this parameter allows balancing in an approximate way, emphasizing major structures while minor structures are either neglected or treated in a simplified way. With this approach a quick overview can be achieved on how much leeway for interpretation exists, • critical points for testing various working hypotheses become more evident, and the trial-and-error effort during the construction of a balanced section is considerably shortened. Still the implications the observed structures have on the deeper crustal levels can be assessed. This concept is applied to a section across the Italian Dolomites, a brittle fold-and-thrust belt lacking reflection seismic data so far and thus with a poorly known deep structure. Still active south vergent Alpine thrusting is oriented approximately perpendicular to previous Dinaric thrusting. The ramp flat style is dominant due to rheological constrasts within the stratigraphic sequence. Thanks to kinematic balancing based on surface data, three Alpine thrust systems could be identified, each defining a thrust sheet with its particular basement unit and its sedimentary part. Superposition of the two more external basement units led to the presently observed high elevation of the Triassic sequence in the Dolomites. Shortening since late Miocene times amounts to more than 50 km. Retrodeformation of Alpine thrusting is a key for better understanding the previous Dinaric structures and kinematics.

Lineament domain analysis to infer groundwater flow paths: Clues from the Pale di San Martino fractured aquifer, Eastern Italian Alps

“…9B). The thrusting is likely characterized by a rampandflat geometry according to the tectonic style proposed by other authors for this part of the Alpine orogen (e.g., Doglioni, 1985;Schönborn, 1999), and is responsible for the observed intense fractur ing of the Pale di San Martino aquifer. The main lineament domain showing a N340° direction of regional compression thus indicates that the fracture systems nearly parallel to this direction are the main water carrier.…”

“…The uplift of the belt is ascribed to a rampandflat thrusting mechanism that was favored by inherited sedimentary features (Doglioni, 1985). Through the construction of balanced cross sections, Schönborn (1999) proved that the Dolomites were likely uplifted by very long décollements and by a number of blind thrusts. These thrusts also involve the crystalline basement and have provided an overall shortening below the east ern Southern Alps of at least 50 km since the late Miocene.…”

“…The ma trix porosity is <5% (Blendinger et al, 2015), whereas the secondary permea bility is high due to the rock brittle deformation. This includes a complex net work of fractures and faults generated from the polyphased tectonic history that has affected this part of the Alpine orogen since Eocene times (Bosellini and Doglioni, 1986;Doglioni, 1987;Castellarin et al, 1992;Schönborn, 1999;Castellarin and Cantelli, 2000). Despite the fact that dolomite groundwater sys tems usually show less karstification than limestone systems (Hartmann et al, 2010), the aquifer of the study area has several karst features.…”

Cenozoic structural evolution of the Argentinean Andes at 34º40’S: A close relationship between thick and thin-skinned deformation

“…BaB.x-1 oil well registered the presence of several slices of the Choiyoi Group (Manceda et al, 1992). Comparable kinematic models, where superposition of basement-involved thrust sheets results in high elevations of basement rocks that produced deformation in the sedimentary cover, have been proposed in other fold and thrust belts in the Andes (e.g., Kley, 1996;McQuarrie et al, 2008) and elsewhere (e.g., Schönborn, 1999;Heermance et al, 2008).…”

Water-rock interactions and trace elements distribution in dolomite aquifers: The Sassolungo and Sella systems (Northern Italy)

“…Finally, during the Neogene, the Dolomites became the innermost part of a south-vergent thrust belt. Most of the present elevation of Dolomite mountains has been generated during this phase (Doglioni, 1987;Schönborn, 1999).…”