Terrestrial Analogs 2021 (LPI Contrib. No. 2595) 8023.pdf

FJORD-HEAD DELTAS IN FINNMARK, NORWAY: ANALOGS FOR PALEOLAKE FAN-DELTAS IN XANTHE TERRA, MARS. J. Wolak Luna1, K. Crane2, and G. D. Corner3; 1Department of Earth Sciences, Tennessee Tech University, 1 William L. Jones Drive, Cookeville, TN, 38505, [email protected], 2Department of Geosciences, Mississippi State University, 3Department of Geosciences, UiT The Arctic University of Norway.

Introduction: Fjord-head deltas are a subset of fan- on the surface of the delta plain, and channel widths deltas that form in subarctic to arctic latitudes on Earth. range from 30-70m. Wave-cut terraces are uplifted They are characterized by a prism of sediment deposited adjacent to the modern Björnnes fan surface, which at the mouth of a canyon or feeder channel debouching suggests a history of base level fall linked to local into a deep marine fjord [1, 2]. Most fjord-head deltas isostatic rebound [6, 7]. Terrestrial and martian orbital show classic Gilbert-type delta profiles and measure imagery shows lineations that cross-cut feeder canyons <10km in diameter. They demonstrate a change from on Earth and Mars. These features are likely tectonic, subaerial processes on the delta plain to subaqueous implying that structural deformation controls the processes on the delta slope and toe [3]. channel pathway and volume of sediment available for Assuming a cold and wet Mars scenario [4], fjord- these fan-delta systems. head deltas on Earth may be analogous to fan-deltas Future Work: Given that fjord-head deltas preserve formed in crater paleolakes on Mars. Both systems are a history of sea level change, our next step is to characterized by: (1) steep walls incised by feeder determine what geomorphic attributes—observable in canyons or channels; (2) deep basins of quiet water with orbital data—can be used as reliable indicators of minimal alongshore currents; (3) limited wave fetch; (4) paleoshorelines, e.g. terraces, beach ridges, distributary coarse-grained sand or gravel deposits; and (5) seasonal channels, barforms, etc. Applying these proxies to ice that may cover standing bodies of water. Fjord- or martian fan-deltas would allow us to reconstruct base fan-deltas are an ideal setting to reconstruct ancient level rise and fall in paleolake systems and tell us about shorelines, answer questions about the subaerial to the longevity of standing bodies of water on the ancient subaqueous transition, and investigate tectonic controls martian surface. on catchment development. Acknowledgements: This work was funded by a Field Work: In August of 2019, we conducted a Tennessee Tech Faculty Research Grant to JWL. Our preliminary field study of 12 fjord-head deltas in the work is dedicated to the memory of Åge Grøtta (1952- Finnmark region of northern Norway to determine 2020), captain of the Porsangerfjord vessel Bris. suitability as analogs for fan-deltas observed in the References: [1] Corner et al. (1990) IAS Spec. Pub. Xanthe Terra region of Mars (Figure 1). Field 10. [2] Nemec and Steel (1988) Fan Deltas: observations focused on characterizing the general Sedimentology and Tectonic Settings. [3] Prior et al. stratigraphy of each delta as well as documenting grain (1981) Nature, 290(5804). [4] Wordsworth et al. (2015) size, lithology, sedimentary structures, bedforms, and JGR: Planets, 120(6). [5] Rice (2014) GSL Spec. Pub. diagenesis on the modern fan surface. We used 390(1). [6] Corner and Eilertson (2008) 33rd IGC bathymetric maps to investigate offshore delta deposits Excursion Field Guide 40. [7] Romundset et al (2011) and a local fishing vessel to explore bathymetry of one Quat. Sci. Rev. 30(19-20). delta deposit in detail. Results: Among the study locations, the Björnnes delta exhibited characteristics most similar to martian fan-deltas. Björnnes, Norwegian for “Bear Point”, is located 25 km northeast of the community of Lakselv, Norway at 70.14°N, 25.25°E. The delta is surrounded by a prominent sandy beach ridge measuring >1km in diameter. Coarse-grained barforms and branching channels characterize the fan surface, and an active channel system transports sediment from the Björnnes canyon onto the delta slope. The fan is sourced by a narrow feeder canyon approximately 12 km long and cross-cutting lithologies of the metasedimentary Gaissa Nappe Complex [5]. Figure 1. Comparison of the Subur Vallis fan-delta The scale of the Björnnes delta is comparable to the system on Mars (top) with the Björnnes fjord-head delta Subur Vallis delta system on Mars (11.63°N, 306.85°E). system on Earth (bottom). Both features show incision of small, erosional channels