DATE:

Friday, February 22nd, 2019

TIME:

3:30 PM

LOCATION:

GMCS-314

SPEAKER:

Dr. Svetlana Kostic, CSRC Associated Faculty

ABSTRACT:

Supercritical sediment gravity flows may play a crucial role in the onset,
growth and evolution of marine and glaciolacustrine deltas. Upper-flow-regime
bedforms emplaced by these flows on deltas appear to be much more common than
previously though in both unconfined and confined settings. These bedforms on
deltas are transient, unstable features, which means that a slight increase in
flow energy can trigger stable antidunes to transition into unstable antidunes,
unstable antidunes into chutes-and-pools, and chutes-and-pools into cyclic steps.
Thus, their deposits are expected to display interbedding of their end members,
i.e. cyclic steps and antidunes, as well as an intermediate bedforms that
represent a superposition of both end members. More importantly, the presence
of upper-flow-regime bedforms in deltaic deposits reveals that the formative
sediment gravity flows fluctuate frequently and broadly.

The most commonly reported bedforms on deltas are undulated sediment features on foresets. Early
on, they were interpreted as sediment deformation and slope failure features.
More recently, these interpretations were seriously questioned and it was
proposed that many fields of sediment waves were in fact formed by sediment
transport processes. Mixed theories suggesting i.e. initial sediment deformation
and growth by differential sediment accumulation patterns were also proposed.

In this talk, I combine numerical analysis with digital elevation models, outcrop,
borehole, and high-resolution seismic data. My objective is: a) demonstrate that
undulated sediment features on deltas are most likely transitional upper-flow-regime
bedforms; b) use recent field case studies of deltas in Italy and Canada to examine
the role of supercritical sediment gravity in delta evolution; and c) briefly discuss
contemporary and ancient upper-flow-regime bedforms that we have been recently recognized
on Martian deltas, with contemporary upper-flow-regime bedforms being attributed to the
sporadic presence of flowing water on Mars.

HOST:

Jose Castillo

DOWNLOAD:

PDF File