Ammonites—Shared Efforts
Memorial Day Field Trip to Lake Texoma
by Neal “field trip” Immega
Member of the Houston Gem
& Mineral Society
quid? It
may seem very strange to go to the
north of Texas to look for squids,
and that is
what the park ranger on Lake
Texoma thought.
More than
one passerby commented to Inda, while she was holding down
“headquarters” at
the boat dock at Lake
Texoma, that there
were
people on the lakeshore who did not seem to be fishing like normal
folks.
Indeed, it looked like they were wandering around, beating on the rocks
with
hammers! It wasn’t that they held Inda responsible for our actions;
they just
seemed to find the very strange behavior of these rock-pounders worthy
of
comment. Inda might have been smart to deny all knowledge of our group,
but no,
she bailed us out. She reported that the ranger had no comprehension of
what a
fossil squid looked like, but he reckoned that there was probably no
bag limit
for 90 million year old, marine squids in a freshwater lake. Whew, I
did not
know that Inda could fast-talk a ranger. I wonder if I could rent her
out to
Brian Honsinger for duck hunts.
A little ancient
history—a classically trained British
paleontologist named a fossil squid for the rams horn headpieces worn
by
priests of the Egyptian sun god Ammon-Ra—i.e., ammonite. A sun god
seems
appropriate because North Texas was
having
more than its share of sun just then. Now, I wouldn’t go so far as to
say that
ammonites exposed in Lake
Texoma were causing
the drought. My patented Immega rain jinx arrived with the field trip,
cooled
things off a bit, but did little to raise the level of the lake.
Excellent! You
probably recall that Peter Ragusa’s trip last year did very well even
though
the lake was high. I do think we must have found the place where old
ammonites
went to die. Well, actually, it was more the place where ammonite
shells ended
up after they died, bloated with gas, rose to the surface, and washed
ashore—maybe
the strand line of the Cretaceous sea.
For us to find an
ammonite fossil, its shell must have been
filled with lime mud. This is not as easy as it sounds. This critter
was not a
snail with a single, spiral chamber. Ammonite shells, like those of the
modern
chambered nautilus, had septa (separators) between their chambers. All
we find
now is an internal mold of the filled chambers and the suture lines of
the
septa. This is because their shells were aragonite, an unstable form of
calcium
carbonate. All too often we only find the outer living chamber because
that is
open to the ocean and easy to fill with lime mud, producing just a
partial
spiral. The shell has to be broken to fill the inside chambers with
lime mud.
Very rarely was the shell material preserved. Jewelry-grade ammonite
shell
material, “ammolite,” comes from places like Canada
and South Dakota
where the ammonite shells were buried in a rock that did not allow
water
penetration to dissolve the aragonite.
It is just a lucky
accident that the Corps of Engineers
decided to build a dam in a place where Cretaceous shales alternate
with
limestones containing ammonites. The shales are very important because
ammonites found in the limestone just above a shale layer are much
easier to
extract. Equally important is that wave action from the lake erodes the
limestone/shale package much more quickly than a 100% limestone
section. The
Hill Country of Texas has lots of ammonites, too, but they are not so
easily
extracted because the rock is almost all hammer-ringing limestone.

Row, row, row your
boat! Our trip that found the
much lower water level revealed a much wider collecting area, just as
if Moses
(or Ammon-Ra?) had parted the lake for us. The only problem is that
HGMS was
not the first one there. People had been collecting a lot because there
were
piles of ammonite sections laid out on the rocks. We had to work for
our
ammonites, but that is only fair. Last year we had to hand carry the
ammonites
a mile or more to the cars parked at the main boat dock. I warned the
field
trip participants that we had to find a different solution, and people
were
very creative.
One member, Tom Lammers,
is a serious remodeling contractor
(and dino dig slab maker). He and his business partner are not afraid
of real
work, and they know about demolition! Their solution to the
transportation
problem was to bring a canoe with three kids to power it, and to move
Tom’s
pickup to the old boat dock to shorten the voyage. The lack of a road
did not
stop Tom—he just drove cross-country to the boat dock. The kids have a
great
future in industry as long as they do not learn about things like
minimum wage.
They cleaned the place out of ammonite fragments—a volume job.

Rick
Rexroad, our
Paleo Section President, devised a great solution involving a kayak and
an
inner tube. He loaded the tube with enough ammonites to almost sink it,
and
just paddled back to the boat ramp. Picture a bright red kazoo pulling
a rubber
ducky! The only problem came when Rick returned by himself in the
evening to
transport more fossils. It seems that a local (and well known) criminal
ripped
off his kayak while Rick was moving his equipment from lake level to
the top of
the boat ramp. Fortunately an alert boater got a license plate number,
and Rick
was able to get help from the local sheriff to get his stuff
back—everyone was
incredibly helpful. Oddly, the thief did not take any of the ammonites.
No
taste!
Al
Mowery has to
get the “heavy equipment award.” He brought a canoe and a
portable
engine-powered air compressor to run his jackhammer. Okay, he never had
to
deploy the jackhammer, but he was PREPARED. I was glad that I
did not
have to help levitate this device into his canoe.
All together now!
The real story is about the
cooperation among our field trippers. The size of our prey made working
together a really good idea. Stand by for an exposé on our Past
HGMS President Elizabeth Fisher.
Those of you who know Eliz will
recall that she is a bit puny compared to Tony, Rusty, and me. But that
is all
right, because she was smart enough to bring along Al Mowery as her heavy. Al must have gotten
strong from his gold
mining activities, though maybe not from handling large quantities of
bullion.
Actually, I do have some doubts about Eliz’s wisdom, because
she told me
that she wanted the biggest ammonite in the state! No way—the Texas Memorial
Museum has some that are four
feet
across that weigh more than 300 pounds, and those were not found at Lake Texoma.
Whew, saved by geology! Unsuccessfully, I pointed out that the really
pretty
ammonites are those with a distinct keel and distinct ribs that stick
out with
a double row of knobs on the edge. These beauties max out at a foot
across and
are suitable for discriminating collectors. The big ones are smooth
without
distinguishing features and are mostly suitable for Paul McGarry to cement into the rock wall
around his house. I
failed to convince her. Some people just want quantity rather than
quality.

Eliz went to the site I
call “Ammonite
Beach”
and quickly glommed onto the biggest ammonite there. Everyone who had
been
there before walked right past it because it was embedded in a nice
hard
limestone block that just happened to weigh about a thousand pounds.
Eliz
attacked it like a woodpecker with a tiny rock pick—and the hammer just
bounced
off. This was probably a good tactic because Al shooed her off and
started in
with a serious pry bar and a much bigger hammer. In an effort to avoid
being
sucked into this project, I stood around taking pictures and offering
sage
advice like “Don’t stand directly in line with the swing of the
hammer,” and “Don’t
put your toes under the rock while you pry on it.” I took dozens of
pictures,
but Eliz paid me to include this one which shows just her working on
the
fossil, as if she had done it all by herself (she remembered that I run
a
business called Incriminating Photos, Bought and Sold). Sunday Bennett claimed that she was
gathering
evidence for my business with her nonstop video camera, but to me it
looked
like she was just experiencing the effects of too much sun and was
standing
around talking to herself.
After Al’s delicate
extraction, the ammonite weighed about 200
pounds and did not seem inclined to go anywhere by itself. It needed to
go
boating, but only Rusty Bennett had the muscle to get it into the
canoe, so he
did just that—an amazing act of levitation. (Just in case you find
yourself in
the same situation but superman is off doing something else at the
moment, Tony Lucci suggests
that people can move serious
loads by putting the load on a tarp and having four people grab the
corners.)
You might think that Al
and Eliz could then paddle happily off
to the boat ramp, but no. The rangers roared up to their very heavily
loaded
canoe and nearly swamped it. The rangers said that they wanted to see
whether
Al had a life jacket in the canoe, but I suspect that they just wanted
to see
what was going on.
Onward, toward the dock,
and we were almost done. Superman, a.k.a.
Rusty, got the huge but homely fossil out of the canoe into the pickup,
and
finally Eliz had her prize. Truly, it was a group effort. This ammonite
now
resides in Eliz’s garden, but all of us have visiting rights!! It’s not
sour
grapes; her ammonite is so plain that it is appropriate to leave
outside
because no one will steal it.

Diane Sisson gets the
award for the best specimen of the trip.
She has a really good eye and found an ammonite surrounded by sea
urchins, and
she got one like it a year ago! It is a really nice piece that we are
going to
feature in the update of the Texas Cretaceous Echinoids book.
You know it was a good
trip when at the end, everyone stands
around looking at the stuff in the backs of the vehicles and no one
wants to
trade! It was very congenial for North Texas
to provide squids for us, particularly since we are, currently, much
closer to
an ocean than they are. The Club had a very productive trip because
everyone
helped everyone in every way.