about the geology of Carroll Cave are being accepted for publication on
this website. James Helwig published a paper based on his undergraduate thesis
(St. Louis University, 1963) in the
NSS Bulletin in 1965. The papers by Morris
Hall are being developed currently (2002). Mr. Hall is a
professional (petroleum) geologist and past member of the Lake Ozark
Grotto (1970's). He has maintained his interest in the cave over the
years and also submitted the following letter.
nice to have met you and the other caver diggers...the geology of the cave
is very well described in the report by Helwig, (NSS
Bulletin Volume 27, Number 1, January 1965) and is way ahead of
it's time in terms of cave genesis thought and basic geologic reasoning...
the description of the geology of the Gasconade, amazingly enough, is
entrance shaft provides a rare opportunity to describe the upper
Gasconade along a significant, fresh exposure and will be important both
from a geologic and hydrologic perspective. Not only does the shaft
provide rocks for analysis, but water samples taken at the various
entrance points along the shaft will provide insight into the vertical
profile of water
chemistry, ph, solution potential, etc. that when compared with the cave's
hydrology, might give some valuable insight into the creation of the
monster we know as Carroll.
back briefly over the topo map, the cave will definitely extend westward to
the plateau sinks south of Montreal...the intriguing idea is presented by
the sink that you describe and showed that would be north of the left
(D6-7) passageway in lower Thunder River. That would suggest a significant
portion of the cave system could exist N and NW of the present cave.
rarity of Carroll is because of several factors:
thickness of soluble rock (300' Gasconade dolomite).
boundaries (bedding planes) providing horizontal paths for solution
and tectonic fractures of both Ordovician and Pennsylvanian age
creating vertical areas of weakness
-40 " rainfall per year...
favorable for dolomite dissolution
lowers rainfall's ph and helps in creation of carbonic acid
uplift- creation of drainage of phreatic conditions to primarily
vadose conditions ( not a severe tectonic event...)
potential drainage area of Toronto Spring watershed. Chemical
equilibria analysis of Toronto Springs suggests that the effluent is
still capable of dissolving lots of rock (i.e.) the groundwater is under saturated
with respect to calcite and dolomite. A very simple
analysis....1MMGal/day lower thunder river = app.20 miles of
cave....where is the cave system that contains the other 3MMGal/day ?
(where is the other 60+ miles of cave?). Probably allot of it is
water-filled (i.e. below the level of the siphon), but the chemical
analysis suggests that allot is air-filled...
10/4/02 from Morris Hall)
Thin sections have been
received...very interesting..the left photo is at 55' showing a quartz
sandstone, with well rounded grains and a clay matrix...glauconite is
present in trace amounts. 10% porosity this is the Roubidoux
formation. the second photomicrograph at 75' is a medium grained, surcosic
dolomite showing non-uniform euhedral crystal fomation...little calcite
present. 20% porosity..this is the upper Gaconade...some relic texture
is visible...other slides show replacement chert where the chert replaces
fossil fragments..maybe the lower Gasconade contact....neat stuff.. we spent
$180 on 9 samples...the shaft photos will help nail it down but..
0-9' Soil, weathered Roubidoux
55+'-100' Upper Gasconade
100'-Total depth Lower Gasconade
Upper Gasconade is approximately
we may need 4 to 5 additional