The rocks which underlie Button Bay State Park can be seen along the
small creek which is located just south of the Park. It is suggested
that the visitor walk southward (to the right if approaching the road
from the lake front) along the main park road until the first culvert
beneath the road is reached. Looking down the creekbed toward the lake,
one can readily see the older rocks (see A, Figure 11). _Fossils_[18]
are found in these tilted rocks which tilt or dip toward the northeast
and “strike” northwestward. Fossils date the rocks underlying Button Bay
State Park as Middle _Ordovician_.[19] The most abundant fossil is a
trilobite, _Triarthrus_, but, even this ancient _arthropod_[20] is not
easily found in these limestones and limy shales. A sketch of
_Triarthrus_ (that portion found fossilized) appears in Plate 1. These
rocks containing _Triarthrus beckii_ belong to the Stony Point formation
and are of late Sherman Fall or Denmarkian age.
One of the jobs of the geologist is to reconstruct the paleogeography
(ancient geography) of a region. The different kinds of rocks present
and their distribution patterns, together with the types of fossil
plants and animals found, tell the geologist of past lands and seas,
warm and cold climates. The rocks of the Stony Point formation (the
rocks which underlie most of the Park) tell of warm marine waters, a
past sea, bordered by relatively low land areas. The fossils contained
in the Stony Point formation attest to the presence of relatively
shallow marine waters. The fact that these Ordovician rocks are tilted
and broken by faults proves that _major earth movements_[21] took place
sometime after their lithification.
[Illustration: _PLATE 1_]
1A, B, C; _Maclurites magnus_ Lesueur (X 0.5). Lower, upper and side
views. Crown Point limestone. GASTROPOD (snail).
2; _Triarthrus beckii_ Green (X 3). Top view of central part of head
region. Stony Point shale. TRILOBITE.
3; _Saxicava_ (X 3). Pleistocene marine clays. PELECYPOD.
4; _Macoma_ (X 3). Pleistocene marine clays. PELECYPOD.
5A, B; _Rhinidictya_ (X 9 and X 1). Orwell limestone. BRYOZOAN.
6A, B, C: _Cryptolithus tesselatus_ Green (X 2). Top, side and front
views. Glens Falls limestone. TRILOBITE.
7; _Rafinesquina._ Internal view. Orwell and Glens Falls limestones.
BRACHIOPOD.
[Illustration: _FIGURE 11_
GEOLOGIC MAP
OLDER ROCKS]
(fault)
CROWN POINT LIMESTONE
CHAZY (VALCOUR?) (Clay covered in most areas)
ORWELL LIMESTONE (clay covered)
GLENS FALLS LIMESTONE (clay covered in most areas)
(fault)
STONY POINT FORMATION (clay covered in most areas)
GEOLOGY NORTH OF PARK BOUNDARY ADAPTED FROM CHARLES W. WELBY—1961
From the north boundary of the Park and along the Lake Champlain
shoreline older and older Ordovician rocks are _encountered_.[22] The
rocks (see geologic map, Fig. 11), primarily tilted marine limestones,
display a variety of fossils, some of which are illustrated in Plate 1.
Figure 12 is a view of the west side of Button Island showing an 18-inch
thick reefy zone in the Orwell limestone. The reefy zone is composed
largely of tumbled heads of colonial corals and stromatoporoids. A
selected list of reference books and articles, some of which contain
plates picturing Ordovician fossils, is found at the end of this
section.
Ordovician and older rocks were lifted, folded and faulted during the
Taconic Disturbance. Dramatic evidence for this period of crustal
instability is seen in the Champlain Thrust, a major series of faults
which can be seen east of Button Bay State Park. The evidence for such a
fault system, which is more fully discussed in another pamphlet, is
readily seen on Mount Philo where older Cambrian rocks have overridden
(been thrust over) younger Ordovician ones.
As time passed in the Button Bay region younger and younger sediments
were deposited over the top of folded and eroded Ordovician rocks. These
sediments became rock and in turn slowly broke into fragments which were
transported to other areas where they were deposited again as sediments.
The glaciers passed over, leaving their rock debris behind as they
wasted northward. Marine clays were slowly deposited from the waters of
the Champlain Sea. Today only the marine clays resting on the beveled
edges of Middle Ordovician rocks can be seen in the Park.
The history of the earth is open for all to read. Button Bay State Park
can tell us only the history which is recorded in its clays and
underlying rocks. As we have seen, there are certain giant geologic time
gaps in the Park area, but many of these do not exist in other places
and in other Parks. If this pamphlet has stimulated an interest in
filling in these time gaps through your study of rocks in other places,
then it has fulfilled its purpose. The present interest in Space demands
a good long look at the Planet Earth. Good Hunting!
[Illustration: Figure 12. Bedded Orwell limestone on open-lake side
of Button Island, showing patches of stromatoporoids and colonial
corals (white areas). Photo by C. W. Welby.]