Abstract Folded reservoir rocks (Eumeralla Formation) within the Otway Basin are of significant exploration interest for their geothermal and tight gas reservoir potential. Brittle deformation within the Eumeralla Formation (ca 113–100 Ma), along the Otway coastline of Victoria, reflects a protracted history of extension, contraction, erosion and uplift, since Australian–Antarctic separation in the Early Cretaceous. This paper investigates the relative timing of heterogeneously distributed fracture populations within both folded and unfolded areas along the Otway coastline. Data collection occurred across two stratigraphic units spanning the Early Cretaceous (Eumeralla Formation) to the late Cenozoic (Demons Bluff Group), in order to measure fracture geometries and determine the relative timing of fracture formation. An unmanned aerial vehicle has been used to facilitate the systematic and inexpensive acquisition of high-resolution orthophotographs along coastal platforms, in order to complement traditional field mapping of fracture populations. A NE–SW-orientated fracture set is observed exclusively within the Eumeralla Formation (St George fold hinge), while a NW–SE-orientated fracture set pre-dates hinge-parallel fractures. Significant fracture formation has been linked to a period of mid-Cretaceous uplift within the eastern Otway Basin (ca 95 Ma). The Eumeralla Formation and Demons Bluff Group also host a NNW–SSE-orientated fracture set that is inferred to largely post-date mid-Cretaceous folding. Sinistral displacement of fold hinges within the Eumeralla Formation, combined with thrust faulting within Cenozoic sediments, is interpreted to have occurred during an episode of late Miocene to early Pliocene shortening. This paper provides new insights into the history of brittle deformation in the eastern Otway Basin.

中文翻译：

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维多利亚州大洋路东奥特韦海岸线裂缝的时间和特征

摘要 Otway 盆地内的褶皱储层（Eumeralla 组）因其地热和致密气藏潜力而具有重要的勘探兴趣。沿着维多利亚州奥特韦海岸线的 Eumeralla 组（约 113-100 Ma）内的脆性变形反映了自早白垩世澳大利亚 - 南极分离以来的延伸、收缩、侵蚀和隆起的长期历史。本文研究了沿奥特韦海岸线折叠和未折叠区域内不均匀分布的裂缝种群的相对时间。数据收集跨越早白垩世（Eumeralla 组）到晚新生代（Demons Bluff Group）的两个地层单元，以测量裂缝几何形状并确定裂缝形成的相对时间。无人机已被用于促进沿海岸平台系统和廉价地获取高分辨率正射影像，以补充传统的裂缝种群实地测绘。NE-SW 方向的裂缝组仅在 Eumeralla 组（圣乔治折叠铰链）内观察到，而 NW-SE 方向的裂缝组早于铰链平行裂缝。显着的裂缝形成与奥特韦盆地东部（约 95 Ma）内白垩纪中期隆起有关。Eumeralla 地层和 Demons Bluff 群还拥有一个 NNW-SSE 取向的裂缝组，据推测，该裂缝组主要是晚白垩世中期褶皱。Eumeralla组内褶皱铰链的左旋位移，结合新生代沉积物中的逆冲断层，被解释为发生在中新世晚期至上新世早期的缩短期。本文为奥特韦盆地东部脆性变形的历史提供了新的见解。