Deposition history and paleo-current activity on the southeastern Lomonosov Ridge and its Eurasian flank based on seismic data

• Main Authors: Weigelt, Estella, Jokat, Wilfried, Schlager, Ursula
• Format: Conference Object
• Language: unknown
• Published: 2020
• Subjects: Amundsen Basin; Arctic; Arctic Ocean; amundsen basin; Fram Strait; Lomonosov Ridge; North Atlantic
• Online Access: https://epic.awi.de/id/eprint/51004/; https://hdl.handle.net/10013/epic.b8682893-7402-46aa-8faf-11b28a402f46

The Lomonosov Ridge (LR) presents a major morphologic feature in the Arctic Ocean. Its tectonic evolution influenced the development of the ocean current system, sedimentation environment, glacial processes and ecosystem. These events are preserved in the setting of sedimentary layers which in turn can be studied and derived from the reflection pattern and reflector configuration of seismic lines. We present a regional seismic data set serving as pre-site survey for the upcoming drilling project IODP-377 (ArcOP). The findings comprise information on depth and setting of target layers in the south-eastern Arctic Ocean. 10 drilling locations can be proposed on the LR to recover the entire Miocene sedimentary sequence or even down to sediments of Lower Eocene age at about 900 mbsf. Four major seismic units are identified which provide constraints on the coupled evolution of subsidence, deposition, and circulation history. First, the core of the LR consists of Mesozoic sediments. A regional unconformity indicates erosion during subsidence of the ridge. The second stage, as indicated by a prominent high-amplitude-reflector sequence, was a time of widespread changes in depositional conditions, likely controlled by the ongoing subsidence of the LR and gradual opening of the Fram Strait. Episodic incursions of water masses from the North Atlantic and erosion of the ridge’s crest probably were the consequences, and led to the deposition of sediments of strongly different lithology. The third stage is marked by continuous deposition since the early Miocene. At that time, the ridge no longer posed an obstacle between the Amerasia and Eurasia Basins and pelagic sedimentation established. Drift bodies along the flanks of the LR and sediment waves in the Amundsen Basin indicate the onset and intensification of circulation. Faulting on the ridge slope has led to a series of terraces. We suggest that ongoing sagging of the ridge and strong currents may have shaped the steep sediment free flanks of the terraces. Lastly, a sequence of high-amplitude reflectors marks the transition to the early Pliocene large-scale Northern Hemisphere glaciations.