Tempestite facies variability and storm‐depositional processes across a wide ramp: Towards a polygenetic model for hummocky cross‐stratification

• Published in: Sedimentology
• Main Authors: Jelby, Mads Engholm, Grundvåg, Sten-Andreas, Helland-Hansen, William, Olaussen, Snorre, Stemmerik, Lars
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: VDP::Mathematics and natural science: 400::Geosciences: 450::Sedimentology: 456; VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Sedimentologi: 456; Svalbard; Helland; Rurikfjellet; Spitsbergen
• Online Access: https://hdl.handle.net/10037/18502; https://doi.org/10.1111/sed.12671

This is the peer reviewed version of the following article: Jelby, M.E., Grundvåg, S.‐A., Helland‐Hansen, W., Olaussen, S. & Stemmerik, L. (2020). Tempestite facies variability and storm‐depositional processes across a wide ramp: Towards a polygenetic model for hummocky cross‐stratification. Sedimentology, 67 , 742-781, which has been published in final form at https://doi.org/10.1111/sed.12671 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions . The hydrodynamic mechanisms responsible for the genesis and facies variability of shallow‐marine sandstone storm deposits (tempestites) have been intensely debated, with particular focus on hummocky cross‐stratification. Despite being ubiquitously utilized as diagnostic elements of high‐energy storm events, the full formative process spectrum of tempestites and hummocky cross‐stratification is still to be determined. In this study, detailed sedimentological investigations of more than 950 discrete tempestites within the Lower Cretaceous Rurikfjellet Formation on Spitsbergen, Svalbard, shed new light on the formation and environmental significance of hummocky cross‐stratification, and provide a reference for evaluation of tempestite facies models. Three generic types of tempestites are recognized, representing deposition from: (i) relatively steady and (ii) highly unsteady storm‐wave‐generated oscillatory flows or oscillatory‐dominated combined‐flows; and (iii) various storm‐wave‐modified hyperpycnal flows (including waxing–waning flows) generated directly from plunging rivers. A low‐gradient ramp physiography enhanced both distally progressive deceleration of the hyperpycnal flows and the spatial extent and relative magnitude of wave‐added turbulence. Sandstone beds display a wide range of simple and complex configurations of hummocky cross‐stratification. Features include ripple cross‐lamination and ‘compound’ stratification, soft‐sediment deformation structures, local shifts to ...