EXTENSIONAL STRUCTURES IN THE OUTER UKRAINIAN CARPATHIANS (CASE OF FIELD STUDY OF THE MENILITE FORMATION IN THE FRONTAL PART OF THE SKYBA NAPPE AT THE VERKHNYE SYNYOVYDNE VILLAGE)

• Дата: 2026
• Автори: Гнилко, О.М., Муровська, А.В., Богданова, М.І., Artoni, A., Chizzini, N.
• Формат: Стаття
• Мова: Англійська
• Опубліковано: Institute of Geological Sciences, NAS of Ukraine 2026
• Теми: Outer Carpathians; Menilite Formation; extensional structure; normal fault; stress field
• Онлайн доступ: http://geojournal.igs-nas.org.ua/article/view/345730
• Назва журналу: Geological journal

The article represents results field study of mainly extensional structures including faults and associated folds within well-known outcrop of the Oligocene Menilite Formation located in frontal part of the Outer Carpathians (Skyba Nappe) near the village of Verkhnie Synyovydne. Most of studied faults are of normal type, and thrust faults are also observed. The latter ones are associated with drag folds and stack-like compression duplexes. The normal faults are mainly of listric-type ones and represented by zones of brittle breccias. The kinematics of normal faults is recorded by flexural-like drag folds and near-vertical striations on the slicken-sides. Based on a set of tectonic mirrors, we reconstructed an extension steress field, with a horizontal axis of maximum extension σ3 across strike of the Skyba Nappe. Intermediate axis σ2 of the reconstructed stress field is also horizontal and directed along the Skyba nappe, and its value is close to the maximum extension σ3. Vertical striations on the tectonic mirrors overlap horizontal striation and are clearly the youngest. Normal faults are interpreted as reflecting the most latest extensional stage developed during the rapid growth of the orogen. The extensional stage could be caused by the detachment of the heavy oceanic slab from the lighter platformian continental crust partly subducted under the Outer Carpathians, which led to isostatic uplift of the orogen and so-called 'orogen collapse'. In addition, normal faults in the flysch allochthone could be formed as a consequence of the direct influence of normal faults fixed in the Carpathian autochthone platformian basement.