New Insight
into Sediment Deposition from Turbidity Currents and ‘Linked’ Debris Flows
Talling, Peter J.1,
Russell B. Wynn2, Lawrence Amy3 (1) University of
Bristol, Bristol, United Kingdom (2) National Oceanography Centre, Southampton,
Southampton, United Kingdom (3) Heriot-Watt
University, Edinbugh, United Kingdom
Deposits of individual submarine flows
have been correlated over an area of 120 x 30 km in the Miocene Marnoso Arenacea Formation of the
Italian Apennines. Bed correlations between 109 sections allow the lateral
evolution of sediment density flows to be analysed in
detail. This unique field data is compared to ongoing experimental and
numerical modelling. Previous models fail to
reproduce the observed deposit shape; suggesting a need to iterate basic models
of deposition from such flows.
Individual beds contain clean turbidite sandstone, mud-rich ‘linked debrite'
sandstone, clean ‘linked debrite'
sandstone and turbidite mudstone. We present
results of settling experiments in static tubes and an annular flume that show
how deposit textures can be related to parent sediment concentration, mud
content and flow deceleration rate.
Most large-volume beds contain an
internal erosion surface underlain by inversely-graded sandstone, recording
waxing and waning flow. These beds contain 0.7-7 km3 of sediment within the
outcrop area, and their total volume may have been significantly greater. Such
large volumes suggest flows were triggered by slope failure. This bed
architecture suggests that slope failure can generate a waxing and waning
turbidity current.
Amy, L.A. and Talling,
P.J., 2006, Anatomy of turbidites and linked debrites based on long distance (120 x 30 km) bed
correlation, Marnoso Arenacea
Formation, Northern Apennines, Italy. Sedimentology,
53, 161-212.
Amy, L., Talling,
P.J.,
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California