Contrasting deformation styles along an active thrust belt front - the external Dinarides and Hellenides
Final Report Abstract
Summarizing the main results of the project, our main scientific findings and conclusions are: • We identified numerous landforms indicative of recent tectonic activity in the transition area between the Dinarides and Hellenides fold-thrust belt, an area that repeatedly hosted destructive earthquakes in historical times, as well as the hitherto strongest instrumentally recorded earthquake (Mw 7.1 Montenegro 1979). For example, NW-SE-trending anticlines in the most external segment of the thrust belt exhibit several windgaps, that suggest reorganization of the drainage network during Pliocene to Quaternary times, likely in response to the activity along underlying thrust faults. • We were able to document highly dynamic Holocene landscape changes in the coastal regions between the cities of Ulcinj in southern Montenegro and Shkodra and Lezha in northern Albania induced by an intricate interaction of sea level changes, alluvial sediment supply from major rivers draining towards the Adriatic Sea as well as tectonics. After the maximum Holocene transgression (ca. 6 - 5 kyr BP) had flooded large parts of the study area, extreme sediment accumulation by the powerful Drin and Buna river systems reversed the coastline’s migration direction, pushing it back seaward for at least 11 km until present. • We were furthermore able to link the seismotectonic information of the strongest instrumentally recorded earthquake on the Balkan peninsula (Mw 7.1 Montenegro earthquake of 1979) with geomorphological data as well as bathymetric offshore data, suggesting ongoing shortening in the frontal portion of the southernmost Dinarides fold-thrust belt. We achieved this by combining onshore geological information with well logs, seismic lines, bathymetric data, seismotectonic and seismological data as well as cross-section balancing techniques into a new structural model for the area. • Our results of linking onshore and offshore as well as seismological data suggest that main shock and strongest aftershock (MW 6.2) occurred on the NE-dipping basal thrust of a largely Palaeogene-age nappe system involving Cretaceous neritic carbonates. Ongoing propagation of this thrust system is documented by the existence of elongated ridges located 15 km offshore. Reflection seismic and bathymetry data reveal that the ridges form crests of actively growing fault-related anticlines. Slip distribution models of the strongest events imply that the basal thrust below the ridges accommodated up to 2.7 m of coseismic displacement. Ongoing shortening along the basal thrust also induced surface uplift of structurally higher thrust imbricates, evidenced by dry valleys incising onshore anticline crests. Combining all evidence, we speculate that the observed structural and geomorphic features resulted from repeated seismogenic faulting events as in 1979. • We also documented three hitherto unknown normal fault scarps exposing bedrock in the western flank of the so-called Rumija mountain chain in southernmost Montenegro. 6 to 9 m high free faces in limestone suggest minimum post-LGM slip rates of c. 0.3 – 0.5 mm/yr. Distinct and sharply delimited earthquake ribbons suggest stepwise exhumation, indicative of repeated earthquake events. In terms of geometry, aerial extent and fabrics, these bedrock fault scarps share many similarities with well-documented normal fault scarps in the central Apennines in Italy, which are known to have ruptured during destructive earthquakes. In view of this overall still dominantly contractional frontal thrust belt segment, these results – i.e. existence of normal fault scarps atop large fault-related anticlines - came as one of the bigger surprises of the project. We interpret the fault scarps as second-order structures associated with structurally underlying first-order thrust faults. Alternatively, these structures might represent a transient behavior of the thrust belt from hitherto dominant shortening to increasingly dominating extension, as a far-field effect of slab-rollback of the Aegean slab further south.
Publications
- 2017. Jena’s connection to the Balkan Peninsula – ongoing work in various segments of the Dinarides-Hellenides fold and thrust belt. 3rd MedMeet, Budapest, Hungary, 14.-15.10.2017
Balling, P., Löwe, G., Schmitz, B., Tomljenović, B., Schmid, S. M., Reicherter, K., Ustaszewski, K.
- 2018. A new balanced cross section across the southern Dinarides fold and thrust belt in the vicinity of the Montenegro 1979 Mw 7.1 earthquake epicenter. TSK - 17th Symposium of Tectonics, Structural Geology and Crystalline Geology, Jena, Germany, 19.-26.03.2018
Pingel, J., Schmitz, B., Balling, P., Ustaszewski, K.
- 2018. Active normal faults within the convergent thrust belt front of the Southern Dinarides (Montenegro & Albania). TSK - 17th Symposium of Tectonics, Structural Geology and Crystalline Geology, Jena, Germany, 19.-26.03.2018
Schmitz, B., Biermanns, P., Ustaszewski, K., Mechernich, S., Djakovic, M., Sokol, K., Reicherter, K.
- 2018. Paleoseismology using bedrock fault planes. EGU General Assembly 2018, Vienna, Austria, 08.-13.04.2018
Mechernich, S., Schneiderwind, S., Mason, J., Biermanns, P., Schmitz, B., Papanikolaou, I., Ustaszewski, K., Reicherter, K.
- 2018. Paleoseismology using bedrock fault planes. TSK - 17th Symposium of Tectonics, Structural Geology and Crystalline Geology, Jena, Germany, 19.- 26.03.2018
Mechernich, S., Schneiderwind, S., Mason, J., Biermanns, P., Schmitz, B., Papanikolaou, I., Ustaszewski, K., Reicherter, K.
- 2018. Structural framework of the 1979 Mw 7.1 Montenegro earthquake. GeoBonn 2018, Annual DGGV Meeting, Bonn, Germany, 02.-06.09.2018
Schmitz, B., Biermanns, P., Djakovic, M., Reicherter, K., Ustaszewski, K.
- 2018. Tectonics shaping the landscape of Southern Montenegro and Northern Albania: A multidisciplinary study of Holocene surface processes at the Dinarides-Hellenides transition. GeoBonn 2018, Annual DGGV Meeting, Bonn, Germany, 02.-06.09.2018
Kremser, R., Freudenberg, L., Korsten, P., Biermanns, P., Schmitz, B., Reicherter, K.
- 2018. The Bar and Katërkolle Faults, Southern Montenegro: Structure and deformation rate estimates. 9th International INQUA Meeting on Paleoseismology, Active Tectonics and Arche-seismology, Possidi, Greece, 24.-29.06.2018
Biermanns, P., Schmitz, B., Ustaszewski, K., Mechernich, S., Onuzi, K., Reicherter, K.
- 2019. Tectonic geomorphology and Quaternary landscape development in the Albania – Montenegro border region: An inventory. Geomorphology, 326, 116-131
Biermanns, P., Schmitz, B., Ustaszewski, K., Reicherter, K.
(See online at https://doi.org/10.1016/j.geomorph.2018.09.014)
