For consideration by the dilletantes such as myself: this problem is not
cheap. Getting sand is cheap. Analyzing samples is not. Many questions
crop up. What is the natural abundance of various quartzes in beach sands
today and from known ancestral river floods and ancestral lake floods? Was
the Wasatch lake-draining a catastrophic event and would it have obliterated
signs that we seek? Is it the event that we seek? Would the lake have held
sediments away from the river that we might be looking for (i.e. would the
source quartz not be Uintah Mountain Quartzite but some other variety)? If
lacustrine deposits were made partially of old river flood deposits, owing
to a superior position of river sediment near a lava lake, then the tracer
quartz from the river deposits would pollute the purity of the lacustrine
deposit. The entire model of tracer quartz needs a bit of discussion.
Are we on the verge of hypothesizing and discovering the ancestral outflow
of the Colorado? Keep plugging. Who has deep pockets for the analyses? I
think we have enough authors for this paper in our gcboaters or riveraccess
groups, so we don't have to depend on pedigreed scientists except as
laboratory tools.
>
>Thanks for the reply. I am looking for ideas at the moment, not
>collaborators. I'll let you know if there gets to be money in this. There
>is a large group of amateur geomorphologists seeking to accomplish three
>things. 1) generate a picture of high river flows based on beach
>deposition; 2) generate a picture for lakes formed by lava dams; and 3)
>collaborate with real scientists to gather data (this, in a convoluted way,
>helps them to reduce their time on the Grand Canyon private river trip list
>from 10 years to somewhat less).
>
>The lacustrine/fluvial question is just forming, and is roughly like this.
>If sediments can be shown to derive partly or mostly from distant sources,
>then the beach is probably formed from river sediment brought in at extreme
>flood stages on the order of 10X the 500 year flood level. If the sediment
>contains only locally derived quartz, then the deposit is almost assuredly
>lacustrine and at a level above or a time after the river flood event. An
>example of distant quartz would be Uintah Mountain Quartzite whereas a local
>source would be Coconino Sandstone.
>
>How much sample would be required for an anaylsis to determine source?
>
>Dave
>
>
>
>
>At 01:22 PM 10/3/97 -0700, you wrote:
>>Hi,
>>
>>I'm not sure I understand a couple of aspects of your email...are you
>>asking for collaborators or just information? How does the source of the
>>quartz tell you it is lacustrine or fluvial? I would say yes, it is
>>possible to fingerprint quartz from sufficiently different sources.
>>Probably a combination of techniques would give the most unambiguous
>>answers. Two methods that come to mind are oxygen isotopes and electron
>>spin resonance. A lot of work would have to be done to characterize the
>>potential source formations; furthermore, the quartz in each has to be of
>>sufficiently different origin for this to work (eg. plutonic vs. volcanic
>>vs. metamorphic) for the oxygen. Regarding ESR fingerprinting of quartz
>>you should check out the paper by Toyoda and Goff (1996) in the 47th New
>>Mexico Geological Society Guidebook, "Jemez Mountains Region."
>>
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