Geoscience Reference
In-Depth Information
wall tiles, from many commercial dealers
in the United States. Like many of North
America's fossil deposits, it was the
driving of the Union Pacific Railroad in
the 1860s that was responsible for the
first major find while excavating west of
Green River, Wyoming. AW Hilliard and
LE Ricksecker, employees of the Union
Pacific Company, collected many
specimens which they sent to Ferdinand
Hayden, Director of the United States
Geological Survey of the Territories, who
named this locality the 'Green River
Shales' (Grande, 1984).
Hayden published a preliminary report
in 1871 and asked the notorious dinosaur
hunter, Edward Drinker Cope of
Philadelphia (see pp. 153-4), to describe
the fish, which included
Knightia
,
Phareodus
,
Erismatopterus
, and
Asineops
.
Cope was not, however, the first to describe
a Green River fish; this honor befell Joseph
Leidy, Professor of Anatomy at the
University of Pennsylvania, who named the
herring
Clupea humilis
(now
Knightia
eocaena
) in 1856 after being sent a
specimen by Dr John Evans, a geologist who
had collected the first recorded Green
River fish from near Green River, Wyoming
in the same year (Grande, 1984).
Cope developed his own collecting
program through the 1870s and it was
also during this period that JW Powell
described the Green River Formation
from Utah (Uinta Mountains), while
AC Peale discovered the formation in
northwest Colorado (
187
). Both sent
their specimens to Cope for inclusion in
his classic monograph published in 1884.
Exactly one hundred years later Lance
Grande of the Chicago Field Museum
published the second edition of his own
classic text on the Green River Formation
(Grande, 1984).
Grande (1984) paid tribute in his
monograph to the many amateur
collectors who have worked the quarries
continuously for the last hundred years
and who have been responsible for most
of the major finds now in public and
private museums. In particular, he
mentioned Robert Lee Craig who dug
from 1897 through the late 1930s, three
generations of the Haddenham family,
who collected from 1918 until 1970, and
the families of Carl Ulrich and Robert
Tynsky who between them have been
collecting Green River fossils from 1947 to
the present day.
S
TRATIGRAPHIC SETTING AND
TAPHONOMY OF THE
G
REEN
R
IVER
F
ORMATION
The Green River Formation dates from
the late Paleocene to the late Eocene
(from approximately 38 to 55 million
years ago;
189
) and is one of the largest
known accumulations of lacustrine
sedimentary rock anywhere in the
world. Its outcrop in Wyoming,
Colorado, and Utah covers an area of
over 65,000 square kilometres (25,000
square miles;
187
) and is on average
approximately 600 m (2,000 ft) thick
(Grande, 1984). These deposits represent
of the world's longest-lived systems of
Great Lakes, lasting for approximately
17 million years.
The Formation is not a homogeneous
unit, but instead comprises a complex
system of lacustrine sediments deposited
in three major lakes situated within
intermontane basins which formed in
early Tertiary times during the uplift of
the Rocky Mountains. Large quantities of
ash within the sediments testify to the
presence of active volcanoes, and drainage
from these tectonic highlands formed
extensive freshwater lakes supporting a
varied fauna. The deposits from these
three lakes differ considerably in their
stratigraphy and lithology and their biotas
should not be considered as a single
community.
The three lakes also had a very
different depositional history (
189
) with
the largest, Lake Uinta (which straddles
present day Utah and Colorado), first
appearing during the late Paleocene and
persisting until the late Eocene. Lake
Gosiute and the much smaller Fossil Lake
(both in what is now southwestern
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