Channelized debris‐flow deposits and their impact on turbidity currents: The Puchkirchen axial channel belt in the Austrian Molasse Basin

Abstract

Deposits of submarine debris flows can build up substantial topography on the sea floor. The resulting sea floor morphology can strongly influence the pathways of and deposition from subsequent turbidity currents. Map views of sea floor morphology are available for parts of the modern sea floor and from high‐resolution seismic‐reflection data. However, these data sets usually lack lithological information. In contrast, outcrops provide cross‐sectional and lateral stratigraphic details of deep‐water strata with superb lithological control but provide little information on sea floor morphology. Here, a methodology is presented that extracts fundamental lithological information from sediment core and well logs with a novel calibration between core, well‐logs and seismic attributes within a large submarine axial channel belt in the Tertiary Molasse foreland basin, Austria. This channel belt was the course of multiple debris‐flow and turbidity current events, and the fill consists of interbedded layers deposited by both of these processes. Using the core‐well‐seismic calibration, three‐dimensional lithofacies proportion volumes were created. These volumes enable the interpretation of the three‐dimensional distribution of the important lithofacies and thus the investigation of sea floor morphology produced by debris‐flow events and its impact on succeeding turbidite deposition. These results show that the distribution of debris‐flow deposits follows a relatively regular pattern of levées and lobes. When subsequent high‐density turbidity currents encountered this mounded debris‐flow topography, they slowed and deposited a portion of their sandy high‐density loads just upstream of morphological highs. Understanding the depositional patterns of debris flows is key to understanding and predicting the location and character of associated sandstone accumulations. This detailed model of the filling style and the resulting stratigraphic architecture of a debris‐flow dominated deep‐marine depositional system can be used as an analogue for similar modern and ancient systems.

The role of mass-transport deposits and turbidites in shaping modern lacustrine deepwater channels

“…Recent studies using outcrops and 3D seismic imaging have thoroughly explored the role of MTD emplaced in channels (Bernhardt et al, 2012;Ortiz-Karpf et al, 2015), which control the distribution, morphology and evolution of avulsion lobe complexes in ancient records. Nevertheless, the response of turbidity currents to channel floor morphology inherited from prior MTDs is poorly understood (Bernhardt et al, 2012).…”

“…Nevertheless, the response of turbidity currents to channel floor morphology inherited from prior MTDs is poorly understood (Bernhardt et al, 2012). Similarly, little is known in regards to short-term geomorphological changes affecting unconsolidated MTDs which might not be preserved in the sedimentary record.…”

The Role of Mass Wasting In the Progressive Development Of Submarine Channels (Espírito Santo Basin, Se Brazil)

“…These studies have shown that turbidity flows can deposit upstream and above MTDs (e.g., Bernhardt et al 2012;Ortiz-Karpf et al 2015;Corella et al 2016), or, instead, can be erosive to create large-scale scours above MTDs (e.g., Shultz et al 2005). Furthermore, turbidity flows can be diverted by topographic highs created by MTDs, leading to the generation of new sediment routes (Hansen et al 2013;Masalimova et al 2015;Kertznus 2009;Corella et al 2016).…”

“…To better understand accommodation space as a function of MTD geometry and internal structure, the interaction between MTDs and turbidity currents has been documented in a number of studies based on outcrop analogues (e.g., Shultz et al 2005;Lucente and Pini 2008;Jackson and Johnson 2009), seismic data (e.g., Kertznus 2009;Bernhardt et al 2012;Masalimova et al 2015;Ortiz-Karpf et al 2015;Kneller et al 2016), bathymetric data (Corella et al 2016), well and core data (Eggenhuisen et al 2010;Corella et al 2016), and numerical models (Stright et al 2013). These studies have shown that turbidity flows can deposit upstream and above MTDs (e.g., Bernhardt et al 2012;Ortiz-Karpf et al 2015;Corella et al 2016), or, instead, can be erosive to create large-scale scours above MTDs (e.g., Shultz et al 2005).…”

“…However, the role of mass-wasting processes in channel initiation and development is still poorly understood due to the lack of good-quality seismic and stratigraphic data. Compared to outcrop studies, which are not ideal for conducting morphological analyses of large-scale MTDs and channels due to their limited exposure, 3D seismic data provides detailed images of MTDs and associated channel-fill deposits (e.g., Bernhardt et al 2012;Masalimova et al 2015;Ortiz-Karpf et al 2015;Kneller et al 2016).…”