Ongoing shortening in the Dinarides fold-and-thrust belt: A new structural model of the 1979 (Mw 7.1) Montenegro earthquake epicentral region

Schmitz, Benjamin; Biermanns, Peter; Hinsch, Ralph; Đaković, Martin; Onuzi, Kujtim; Reicherter, Klaus; Ustaszewski, Kamil

doi:10.1016/j.jsg.2020.104192

Cited by 20 publications

(13 citation statements)

References 42 publications

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“…5 ). This might be related to a Neogene structural overprint due to pronounced Neogene shortening in the southern External Dinarides 17 , 52 , 53 , which is in agreement with the presence of the Neogene South Adriatic Basin 54 (Fig. 1 a).…”

Section: Discussionsupporting

confidence: 79%

Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

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et al. 2021

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The Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

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Section: Discussionsupporting

confidence: 79%

Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

Balling

Grützner

Tomljenović

et al. 2021

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“…5). This might be related to a Neogene structural overprint due to pronounced Neogene shortening in the southern External Dinarides 17,52,53 , which is in agreement with the presence of the Neogene South Adriatic Basin 54 (Fig. 1a).…”

Section: Discussionsupporting

confidence: 79%

Post‑collisional mantle delamination in the Dinarides implied from staircases of Oligo‑Miocene uplifted marine terraces

Balling

Grützner

Tomljenović

et al. 2021

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The Dinarides fold and thrust belt on the Balkan Peninsula is the result of the long-lasting convergence between the Adriatic and Eurasian plates since the Mid-Jurassic. Late Jurassic obduction of ophiolites, Early Cretaceous composite nappe stacking, and subsequent continent-continent collision in the latest Cretaceous resulted in folding and thrusting that in the most external part of the Dinarides took place during the Middle Eocene &#8211; Oligocene. This extensive last phase of substantial crustal shortening and thickening was associated with flexural foreland basin deposition, resulting in Eo- to early Oligocene syntectonic units. These rocks and older Mesozoic carbonate platform units now form the mountain chain of the external Dinarides. So far, the driving mechanism behind the rock uplift was unknown and it was not clear when the present-day topography formed. Here we show that horizontal marine terraces preserved at elevations of up to 600 m in the external Dinarides are crucial to answer these questions.We extracted horizontal surfaces, river incision profiles, and the Adriatic and Black Sea catchments from a digital elevation model (DEM). The extracted horizontal surfaces are interpreted as marine terraces because they are degradational, locally preserved in a staircase morphology, neither bedding- nor fault-related, and located close to the present-day Adriatic shoreline. The marine terraces stretch c. 600 km along-strike the entire Dinaric coastal region. Their spatial correlation agrees with the position of a reported positive P-wave tomography anomaly beneath the Dinarides. This up to 180 km deep anomaly correlates also with the thinnest part of the Adriatic lithosphere and the Adriatic-Black Sea drainage divide. The orogen-perpendicular river incisions profiles reveal a symmetric river incision pattern on both sides of the drainage divide. The mean amount of the river incision is equivalent to the mean elevation of the documented marine terraces. All results point to an orogen-wide surface uplift of the Dinarides.Based on the geological record this post-collisional uplift event can be relatively dated to Oligocene-Miocene (28-17 Ma) and seems to be broadly contemporaneous with the emplacement of igneous rocks with mantle affinity (33-22 Ma) in the internal Dinarides. Previously published geophysical and petrological, as well as the new geomorphological data presented here suggest that the post-collisional reorganization of the Dinarides is attributed to an Oligocene-Miocene mantle delamination event, which results in uplift event affecting the entire Dinarides. We also show that no significant, orogen-scale deformation affected the uplifted Dinarides after the Early Miocene.

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“…4). Its emplacement onto the underlying Kruja-Dalmatian Unit is dated to between late Eocene and middle Miocene (e.g., Schmitz et al, 2020).…”

Section: Geological Settingmentioning

confidence: 99%

Aegean-style extensional deformation in the contractional southern Dinarides: incipient normal fault scarps in Montenegro

et al. 2022

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Abstract. We describe two 5–7 km long normal fault scarps (NFSs) occurring atop fault-related anticlines in the coastal ranges of the Dinarides fold-and-thrust belt in southern Montenegro, a region under predominant contraction. Both NFSs show well-exposed, 6–9 m high, striated, and locally polished fault surfaces, cutting uniformly northeastward-dipping limestone beds at high angles and documenting active faulting. Sharply delimited ribbons on free rock faces show different colors, varying karstification, and lichen growth and suggest stepwise footwall exhumation, which is typical of repeated normal faulting during earthquake events. Displacements, surface rupture lengths, and geometries of the outcropping fault planes imply paleoearthquakes with Mw≈6 ± 0.5 and slip rates of ∼ 0.5–1.5 mm yr−1 since the Last Glacial Maximum. This is well in line with (more reliable, higher-resolution) slip rates based on cosmogenic 36Cl data from the scarps for which modeling suggests 1.5 ± 0.1 mm yr−1 and 6–15 cm slip every 35–100 years during the last ∼ 6 kyr. The total throw on both NFSs – although poorly constrained – is estimated to ∼ 200 m and offsets the basal thrust of a regionally important tectonic unit. The NFSs are incipient extensional structures cutting (and postdating emplacement of) the uppermost Dinaric thrust stacks down to an unknown depth. To explain their existence in a region apparently under pure contraction, we consider two possibilities: (i) syn-convergent NFS development or – less likely – (ii) a hitherto undocumented propagation of extensional tectonics from the hinterland. Interestingly, the position of the extensional features documented here agrees with geodetic data, suggesting that our study area is located broadly at the transition from NE–SW-directed shortening in the northwest to NE–SW-directed extension to the southeast. While the contraction reflects ongoing Adria–Europe convergence taken up along the frontal portions of the Dinarides, the incipient extensional structures might be induced by rollback of the Hellenic slab in the southeast, whose effects on the upper plate appear to be migrating along-strike of the Hellenides towards the northwest. In that sense, the newly found NFSs possibly provide evidence for a kinematic change of a thrust belt segment over time. However, with a significantly higher probability, they can be regarded as second-order features accommodating geometrical changes in the underlying first-order thrust faults to which they are tied genetically.

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Ongoing shortening in the Dinarides fold-and-thrust belt: A new structural model of the 1979 (Mw 7.1) Montenegro earthquake epicentral region

Cited by 20 publications

References 42 publications

Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

Post‑collisional mantle delamination in the Dinarides implied from staircases of Oligo‑Miocene uplifted marine terraces

Aegean-style extensional deformation in the contractional southern Dinarides: incipient normal fault scarps in Montenegro

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Ongoing shortening in the Dinarides fold-and-thrust belt: A new structural model of the 1979 (Mw 7.1) Montenegro earthquake epicentral region

Cited by 20 publications

References 42 publications

Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

Post&#8209;collisional mantle delamination in the Dinarides implied from staircases of Oligo&#8209;Miocene uplifted marine terraces

Aegean-style extensional deformation in the contractional southern Dinarides: incipient normal fault scarps in Montenegro

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Post‑collisional mantle delamination in the Dinarides implied from staircases of Oligo‑Miocene uplifted marine terraces