Allen Roy
---------- Forwarded message ----------
Date: Sat, 1 Nov 1997 11:50:53 -0700
The whole issue of looking at isolated stratigraphic sequences, and
attempting to determine a fit to general stratigraphy falls down when
looking at this, and other localities for that matter. Correlation may be
difficult, if not impossible. In addition to the problems with sequencing
of local events, such as eruptions, by deposition of sediments, there are
the classic problems of INTERPRETATION of the fossils they contain.
Palynology, in my opinion, is a somewhat vague way to determine
environmental influences in the stratigraphic record. Let me indicate why
using one limited example. In the area that I live, the mountains contain
primarily pines. At times during the year, great clouds of pine pollen
exit the front ranges of the Rockies, and are deposited in the lakes and
ponds of the area. The Foothills trees are primarily larches, aspens and
cottonwoods, with some pines present in the mix. Depending on wind
direction, time of year, plus other factors such as sediment influx, lake
inflow/outflow, etc. many variables are introduced to alter sediment
entrainment of pollen grains.
If one were to core the lake and pond sediments, one would find a
surprising stratification of a variety of pollen zones. One could surmise
that a pine forest grew in the area at one time, then a mixed forest grew
there, then at another, a deciduous forest grew there, then something
else, all requiring great periods of time. One can be led to all kinds of
explanations and interpretations, but it is very difficult to conclusively
KNOW what events occured at the time. We can speculate, to no end.
Further, there is an explanation within a short period timeframe for these
sorts of observations as I have indicated.
Further, the fact that the cores extracted are unlithified (uncemented) is
no indication of age, or even burial depth, in my opinion.
The following personal and literature observations point out the dilema
that geologists face:
Apparent or Lithification
Indicated Age or Cementation State
************** ********************
Young strata: poor
Young strata: moderate
Young strata: well
Old strata: poor
Old strata: moderate
Old strata: well
What this indicates is that the degree of lithification is no indicator of
age. Young strata (Recent) can be well cemented. Older strata (supposed)
can be poorly cemented. What is important is to understand that we are
only beginning to truly understand lithification processes. (More creationary
research to do.)
Jumping to conclusions regarding age and time required for sequencing of
events, based on interpretations of stratigraphic and fossil evidence can
lead us down some winding paths. Let's not get snared.