Geoscience Reference
In-Depth Information
51
51 Beechers quarry today,
looking downstream west.
bulldozer and back-hoe to re-excavate the
quarry. It turned out later that their first
excavation was actually in Walcott's
quarry but, nevertheless, Beecher's Bed
had been rediscovered. Once located,
further excavations were made in 1989 by
a joint team from the Smithsonian
Institution, Washington DC, and the
American Museum of Natural History,
New York (Briggs and Edgecombe, 1992,
1993) and, more recently, by a team from
the Yale Peabody Museum. Both
Beecher's and Walcott's quarries are now
re-exposed for study (
51
), but the main
obstacle to collecting lies in the fact that
the near-horizontal bed runs straight into
the river bank, so tons of overburden
would need to be removed to expose
more of it.
52
S
TRATIGRAPHIC SETTING AND
TAPHONOMY OF
B
EECHER
S
T
RILOBITE
B
ED
Beecher's Trilobite Bed is a 4 cm (1.5 in)
bed of hard mudrock almost
indistinguishable from the under- and
overlying Frankfort Shale beds except for
its inclusion of beautiful pyritized trilobites
(
52
). The surrounding beds contain thin
layers rich in the planktonic graptolite
Climacograptus
, scattered parts of
Triar thrus
, articulated brachiopods, and
large, orthocone (straight) nautiloids (
53
).
There is some post-compaction pyritization
52 A pyritized Triarthrusfor which Beechers
Trilobite Bed is famous. This specimen, or one
very similar, was the model for 50 YPM.
Animal is about 3 cm 1.2 in long excluding
antennae.
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