Seismic Stratigraphy I

1
Seismic Stratigraphy I
-
February 8


Basic concepts

Seismic data



Seismic stratigraphic concepts



Seismic Stratigraphy II - February 13



Seismic stratigraphy of non-glacial and glacial
margins


Overview and examples



Regional seismic stratigraphy and core data



Antarctic Peninsula



Weddell Sea



Prydz Bay



Wilkes Land



Ross Sea





Seismic Stratigraphy III
- February 20

• Student presentations

• Seismic Stratigraphy II wrapup
• Special topics Seismic stratigraphers
  cookbook (Ross Sea Atlas),
• backstripping, Pliocene?
  event

2
Excerpt from the Dec. 3, 2006 weekly report
(quoted from Ross Powell and Tim Naish)

• The core continues to deliver an impressive
  stratigraphy and range of glacimarine facies.
• The cycles continue from the previous week with
  five, 30-50m-thick cycles between 241-376mbsf
  dominated by diamictite (glacials) with thinner
  intervening diatomites (interglacials) ..
• Ultimately we hope the differing degrees of
  paleoenvironmental changes can be related to
  external forcings, such as climatic changes, so
  we can determine what the critical trigger points
  or thresholds can be for the Ross Ice Shelf and
  West Antarctic Ice Sheet systems.

http//andrill.org/report/
3
LAST CLASS ROSS POWELL (Co-chief on ANDRILL)
First results of the 2006 drilling season the
lithostratigraphic record http//andrill.org/repor
t/
4
Student Presentations
5
Wilkes Land margin seismic and drilling
6
There are 2 DSDP drill sites along this segment
of the Antarctic margin.
Reflection geometries are similar to other
Antarctic margin segments. Recent seismic
surveys by Australia and Russia allow regional
mapping of the unconformities.
2004
E.Mio.?
Late Olig.- E.Mio.?
Eocene?
7
Wilkes Land margin
CS4 WL4 CS3 WL3
8
Similarites in acoustic geomtries on the East
Antarctic margin
Recent seismic surveys by Russia and Australia
further illustrate general similarities in
reflection geometries for Neogene sections.
Russian data 1986-1995 2000-2005
Leitchenkov (2005)
9
Regional depositional features derived from
seismic surveys (from Leitchenkov, 2005)
Leitchenkov, 2005, pers.comm.
10
DRIFT FORMATION ON THE CONTINENTAL RISE
From Kuvaas et al., 2004 Leitchenkov pers.comm.
Rebesco et al. 1997
11
Ross Sea seismic and drilling
12
In the Ross Sea, there is large variability in
seafloor and subsurface geologic and seismic
facies (and varied paleo depositional
environments).
13
Ross Sea Seismic Facies Map
The seismic facies map shows that there are
regional systematic variations in sediment
deposits.
14
Ross Sea drilling recovered mostly marine
glacial rocks, indicating that the Ross Sea has
been submerged and that glaciers have been
nearby since at least early Oligocene time.
ANDRILL
Cape Roberts
CRP AnDr
15
Seismic Interpreters Cookbook
With examples from the Ross Sea Stratigraphic
Atlas AGU Antarctic Research Series, V. 68, 1995
16
Regional Mapping Seismic Interpretation
techniques
Examine data bases and select seismic profiles
17
Identify seismic facies on reflection profiles.
Desantis et al. (1995)
18
Covert reflection times to depth along ship tracks
Measure reflection times to the seafloor .
..and from the seafloor to subsurface
unconformities.
Cochrane et al (1995)
Calculate velocities of subsurface layers from
sonobuoy seismic profiles (and/or multichannel
seismic data)... use the velocity information
to convert reflection times (in sec.) to depths
(in m).
19
Use water depths from all tracklines to make a
bathymetric map of the sea floor. This is atlas
plate 1a.
20
Use seismic characteristics to make facies maps
for different time periods.
21
The bathymetric map shows the morphology of the
seafloor, and the evidence of large ice streams
that carved wide troughs.
22
Backstripping Taking the clothes layers
off the shelf
23
Laura De Santis Giuliano Brancolini Angelo
Camerlenghi Michele Rebesco
2-D backstripping modelling of three Antarctic
continental margins (Ross Sea, Antarctic
Peninsula, Prydz Bay)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
The Eastern Ross Sea Margin
28
END OF LECTURE