Colleagues,
An Excel application called ONLAPSE which BHPB have selectively released
in the past is now available to the general public on the TecTask
website
(http://www.tectonique.net/tectask/index.php?option=com_frontpage&Itemid
=1) . Like my previous two applications, this is a basic
forward-modeling calculation which is designed to simulate the geometry
of growth strata in deep water depositional environments. In contrast to
the other simple spreadsheets DRAWL and STRATOMATIC, which both attempt
to use some basic geological principles to generate topography (salt
withdrawal and movement on an irregular fault surface, respectively, for
ONLAPSE you simply specify a structural profile which is allowed to grow
with time. You can change the rate of structure growth, the rate of rise
of sediment base level, and the rate of hemipelagic background
deposition, and the rates can be constant or varying through time.
Ru Smith published some simple simulations of the geometry of onlapping
sediments in recent Geol Soc of London special publications. This
application was inspired by Ru's (unpublished) spreadsheet and was
designed to take it a couple of steps further - to investigate what
happens with complex topography, or varying growth rates. On of the
simplest of all geological structures is the onlap of sediment on to a
planar, dipping surface. This is one of the options which you can
investigate before launcing in to more complex scenarios.
The basic assumptions made in this spreadsheet are
(i) all structure movement is vertical
(ii) there is no erosion
(iii) each layer of pelagic background sedimentation (grey layer) is
deposited uniformly across the whole model
(iv) each layer of turbiditic sedimentation (yellow layer) fills up the
remaining topography up to the current sediment base level
(v) there is no compaction
Yellow layers represent the turbiditic component of deposition duruing
that time interval, not the net sand
This application is designed for use on IBM compatible windows. It may
not run on Apple systems. It contains many macros which are needed for
it to run - you will need to enable macros if these are disabled.
Your feedback would be most welcome. If you use it and you like it, you
can buy me a beer some time.
Regards
Frank Peel
Global Geological Advisor, BHP Billiton Petroleum
This message and any attached files may contain information that is confidential and/or subject of legal privilege intended only for use by the intended recipient. If you are not the intended recipient or the person responsible for delivering the message to the intended recipient, be advised that you have received this message in error and that any dissemination, copying or use of this message or attachment is strictly forbidden, as is the disclosure of the information therein. If you have received this message in error please notify the sender immediately and delete the message.
|