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    [Illustration: Cover Picture: Selected “buttons” from the clay bank
    along the beach at Button Bay State Park. (×0.8).]




                             THE GEOLOGY OF
                         BUTTON BAY STATE PARK


                                  _By_
                          HARRY W. DODGE, JR.


                    DEPARTMENT OF FORESTS AND PARKS
                      Perry H. Merrill, _Director_

                     VERMONT DEVELOPMENT DEPARTMENT

                       VERMONT GEOLOGICAL SURVEY
                   Charles G. Doll, _State Geologist_


                                  1962




                             THE GEOLOGY OF
                         BUTTON BAY STATE PARK


                                  _By_
                          Harry W. Dodge, Jr.




                              INTRODUCTION


Button Bay State Park is located on the eastern shore of Lake Champlain
with lake frontage on Button Bay (see maps, Figs. 1 and 2). This Vermont
State Park is reached from the nearest large town, Vergennes, by
proceeding southwest, toward Addison, on State Route 22A for .25 miles
beyond the bridge over Otter Creek, thence, right on the Basin
Harbor-Panton road for another 1.4 miles to the first road entering from
the right. Turn right on this, the Basin Harbor road, and proceed for
4.5 miles, thence, left for 1.4 miles to Button Bay State Park (see map,
Fig. 2, note arrows). A more direct road is planned to connect the Basin
Harbor Road with the Park, however, this route has still not been
completed.

Prior to its present name, Button Bay, the “sickle-shaped bay” on which
Button Bay State Park is located was termed _Button Mould Bay_[1]. In
“The Journal of William Gilliland” which is found in the “Pioneer
History of the Champlain Valley” by Winslow C. Watson, Albany, 1863, and
under the date of September 7, 1765, is found an entry which speaks of
“his (Gilliland) overtaking ‘_the Governors and other gentlemen_’[2] at
Button Mould Bay, and going aboard their sloop.”

A book of charts by Captain William Chambers contains one entitled “Baye
du Roche Fendue (Split-Rock Bay) and the soundings taken in August
1779.” At the upper corner of the chart is the name “Button Mould Bay.”
The first appearance of the shortened version, Button Bay, seems to be
in Whitelaw’s map of 1796 which was used as the frontispiece of the
Census volume, “Heads of Families, Vermont, 1800.”

    [Illustration:                 _FIGURE 1_
                MAP OF WEST-CENTRAL VERMONT AND EASTERN NEW YORK]

    [Illustration:                 _FIGURE 2_]

Why the name Button Bay? H. M. Seely (1910, p. 274)[3] when discussing
the shoreline of this bay states, “Besides shells, _concretions_[4],
some of strange imitative forms (many shaped like animals), are loosened
from the clay.” He goes on to say that a “form particularly abundant in
the banks of the bay (and on the beach) has the shape and size of a
turned wood button-mold (mold is commonly spelled ‘mould’ by the
British), a disc with a hole in the center, plane (flat) on one side and
convex on the other” (see Fig. 3 and cover picture). The abundance of
these button mold-shaped concretions obviously led to the older name,
Button Mould Bay which was later shortened to Button Bay.




                  THE GEOLOGY OF BUTTON BAY STATE PARK


If the visitor confines his wanderings to the State Park the most
conspicuous geological features, or clues to the Park’s past history,
are concentrated in the clay banks and adjacent beach which border Lake
Champlain (see Fig. 4). The clays which cover the entire Park record
thousands of years of rather recent events, _geologically speaking_[5],
which took place in the Champlain Valley. These clays also record a very
significant phase in the development of present Lake Champlain. Before
discussing the clays it will be necessary to outline some of the
geological events which preceded the deposition of the clays, that is,
some of those events which took place as the last glacial ice lobe
slowly retreated up the Champlain Valley and into Canada. The author has
borrowed heavily from an article by Donald H. Chapman entitled
“Late-Glacial and Post-glacial History of the Champlain Valley” which
was published in the 1941-1942 “Report of the State Geologist on the
Mineral Industries and Geology of Vermont, twenty-third of (the)
Series.”

    [Illustration: Figure 3. Water-worn concretions seen on the beach of
    Button Bay State Park. The button-mold shape of some concretions led
    to the incorporation of the word “Button” in the name Button Bay
    (Originally, Button-Mould Bay). The chisel portion of the Alpine ice
    ax head is about 5 inches long.]

During the final retreat of the last ice sheet to invade the New England
states (some 11,000 to 12,000 years ago) an ice lobe, which occupied the
Hudson-Champlain Valley, slowly wasted northward toward the Canadian
border. Melt-water derived from the melting glacial ice together with
atmospheric water (rain and snow) formed a succession of lakes dammed on
the north by the glacial ice. These lakes emptied to the south through
the Hudson Valley. This succession of lakes and intermediate lake stages
will be discussed in the following paragraphs.

    [Illustration: Figure 4. View of beach, Button Bay State Park,
    looking toward the southeast. The beach demonstrates several
    water-level and storm-level debris lines. Note the conspicuous lack
    of sand on this “clay” beach.]

The oldest lake recognized by the geologists is termed “Lake Albany” and
was confined to the Hudson Valley. At this time the area of present-day
Lake Champlain, north of the Hudson Valley, was still covered by glacial
ice which was slowly melting as the general regional climate throughout
New England became warmer and warmer. Soon the whole Hudson Valley
region began to _rise_[6] out from beneath the lake waters and “Lake
Albany” shallowed. Eventually a rock ledge emerged just south of
Schuylerville, New York (actually at Coveville, New York) over which the
waters from a new lake, Lake Vermont, began to flow.

Lake Vermont, with its rock ledge dam at Coveville, began to expand
northward as the ice front retreated up the Champlain Valley. Several
distinct stages in its development are now recognized in _features_[7]
demonstrating past lake levels which are abundantly displayed close to
Button Bay State Park. The “lake-level indicators” or features tell us,
in addition to the number of distinct lake stages in a given area,
something about past earth movements. A “line of
lake-level-_elevation_”[8] is drawn through those features outlining
each past lake or lake stage followed by a comparison of each line with
those lines constructed for older and younger lakes or lake stages. If,
for any two lake-level lines compared, these lines are not parallel, it
can be assumed that the earth’s crust was tilted during the time between
the formation of their lake-level features. This idea of tilting of the
earth’s surface, which is supported through the study of successive lake
levels, has proven the key to the present status of Lake Champlain.

At the beginning of its history Lake Vermont emptied to the south
through an outlet channel located in the vicinity of Coveville, New York
(see map, Fig. 5A). This stage in the development of Lake Vermont, often
referred to as the Coveville Stage, saw lake waters fill the Champlain
Valley from the Green Mountains on the east to a position west of the
present New York-Lake Champlain shoreline. Such Vermont towns as
Middlebury, Vergennes, Hinesburg, Burlington and Colchester would have
been submerged beneath the lake waters (see map, Fig. 5B). Certain high
areas such as Mount Philo, Pease Mountain and Cobble Hill show
lake-level features along their sides which prove that these areas were
islands rising above the level of this past lake. If you visit Mt. Philo
State Park, located approximately 11 miles north of Vergennes, one of
these lake-level features, a wave-cut terrace, can be seen at an
elevation of 545 feet and on the south side of the hill (at the level of
the second reverse turn in your trip to the _summit area_).[9]

    [Illustration:                 _FIGURE 5_
                    _EARLY COVEVILLE_    _MAXIMUM COVEVILLE_]

    [Illustration: Figure 6. Looking west from the top of Mount Philo
    State Park. The Adirondack Mountains are on the skyline, Lake
    Champlain in middle background and the Champlain Lowlands stretch
    from Lake Champlain to the base of Mount Philo.]

    [Illustration:                 _FIGURE 7_
                     _FORT ANN MAXIMUM_    _MARINE MAXIMUM_]

Shortly after Coveville Lake Vermont reached its maximum size (see map,
Fig. 5B), a southern gorge-outlet was formed at an elevation lower than
the previous Coveville outlet in the vicinity of Fort Ann, New York
(Fort Ann is located approximately 8 miles south of the present southern
extremity of Lake Champlain). The level of Lake Vermont’s water dropped
to the new Fort Ann Stage (see map, Fig. 7A). Evidence for this new lake
level is seen on the slopes of Mt. Philo, Snake Mountain and Cobble
Hill. These lake-level features are parallel to and found 100 feet below
those of the Coveville Stage. These parallel features, then, indicate
that very little, if any, tilting of the earth’s crust had taken place
between the Coveville and Fort Ann lake stages.

    [Illustration: Figure 8. Beach and clay banks exposed along the Lake
    Champlain portion of Button Bay State Park. This view is toward the
    northwest and includes a major portion of the Park’s lake frontage.
    Photo by Robert B. Williams.]

This Champlain ice lobe continued to melt and retreat toward the
Canadian border and beyond. As the glacial front approached the St.
Lawrence valley, fresh water from Lake Vermont began to seep through the
retreating ice lobe and into the marine waters which filled the St.
Lawrence area. Several shoreline (lake-level) features are found at
different elevations below the Fort Ann Stage of Lake Vermont and attest
to a slow lowering of the lake level by the escape of fresh water to the
north.

The conspicuous clays of Button Bay State Park were deposited during the
next episode in the history of the Champlain Valley, a development
heralded by continued retreat of the ice lobe and contact with the St.
Lawrence marine waters. Let’s take a look at the clays so well displayed
along the Button Bay State Park beach and see if we can piece together
their history.




                   THE CLAYS OF BUTTON BAY STATE PARK


The best location in the park for a good look at the clays which cover
the entire Park area is along the lake beach (see Figs. 4 and 8). The
bank averages 23 feet in height measured from the beach to the top of
the bank. The width of the beach varies seasonally and during storms as
the water level of Lake Champlain fluctuates (see Figs. 4 and 8). A walk
along the beach will reveal some interesting facts about the composition
of the beach and the adjacent clay banks.

One cannot help observing the scarcity of _sand_[10] on the beach. The
only adjacent material to build this beach is clay, which here contains
a small quantity of sand and some concretions containing lime. The
sickle shape of Button Bay keeps most foreign sand from the beach. The
small patches of sand present soon give way to _blue clay_[11] which, in
many places, forms the base of the beach. This blue clay can also be
seen in the base of the bank in the southern portion of the Park, where
it underlies and is therefore older than the _brown clay_.[12]

Actually very little of the blue clay is exposed in the Park. From other
locations along the shore of Lake Champlain and in the more inland areas
of the Champlain Lowlands geologists have found many clues to help our
understanding of its history.

    [Illustration: Figure 9A. View of the Brown Clay at the base of the
    clay-cliff, Button Bay State Park. For scale, note the small
    ballpoint pen resting on top of ledge (left of center). A close-up
    view of this ledge (pen in same location) is seen in Figure 10.]

    [Illustration: Figure 9B. Close-up view showing general
    characteristics of the Brown Clay. Notice the vertical cracks in the
    clay. These cracks or joints are very common in the clays of this
    State Park.]

In August 1849 the incomplete skeleton of a _whale_[13] was found in a
railroad cut being excavated for the Rutland and Burlington Railroad.
This cut was located approximately 12 miles south of Burlington and a
mile east of Lake Champlain. The significant fact about this “find” is
that these bones were found in the same type of blue clay that occurs at
the beach in Button Bay State Park. Clam and oyster shells (Pelecypods)
were found in association with the whale bones. These _pelecypod
shells_[14] and the whale bones show that these animals lived and died
in cold marine waters. Lake Champlain today is a fresh-water lake and
the fish and other organisms in it are those of fresh, not salty water.
Yet the blue clays (and we are soon to learn, the brown clays) hold
evidence proving the existence of sea water in an area where a
fresh-water lake is found today. Can this be explained?

The brown clay forms most of the Park’s clay banks (see Figs. 9A and 9B
). It can be examined easily by the visitor. The bank is composed of
clay and variable amounts of _fine sand_[15] in thin lens-shaped bodies.
The hard dry outer clay, if rain has not just fallen, of the upper 15
feet of the bank appears light brown or tan-white and commonly contains
interspersed white and blue streaks. In the section of the bank which
was the object of detailed study, two conspicuous _convoluted beds_[16]
were found, one 5 feet above the beach, the other nearly 2 feet above
the first.

Shells of _pelecypods_[17] occur at two and perhaps three levels within
the bank. They can be seen easily in many slumped clay bodies along the
beach (see Fig. 10, in which the shells are mainly _Macoma_ and
_Saxicava_). These shells once belonged to living animals whose very
close relatives and identical younger generations are found living today
in cold Arctic waters. Brown clays were deposited in a marine Champlain
Sea. How did these marine waters get into the Champlain Valley?

    [Illustration: Figure 10. Close-up view showing the pelecypod (clam)
    shells which occur within the Brown Clays. Note small Ballpoint pen
    for scale. These shells tell us of the marine origin for these
    clays. The pelecypods here are _Saxicava_ and _Macoma_.]

Remember from the previous discussion of Lake Vermont that as the
Champlain ice lobe retreated into Canada, fresh water from Lake Vermont
began to seep through the ice lobe into the St. Lawrence Valley. This
seepage caused a gradual lowering of the Lake Vermont water-level until
the lake reached a stage lower than the marine waters of the St.
Lawrence Sea. Soon the sea water began to flood Lake Vermont and true
marine conditions were reached. These marine waters reached as far south
as Whitehall, New York, which is located near the southern end of
present-day Lake Champlain.

The maximum area covered by the Champlain Sea did not equal the greatest
size attained by the fresh waters of Lake Vermont. For instance, the sea
did not extend as far east as the Green Mountains except in the very
northernmost region of Vermont. In the vicinity of Button Bay State Park
these waters extended less than a mile east of Vergennes, and the towns
of Middlebury, Hinesburg and Charlotte would have been entirely above
water (see map, Fig. 7B).

It has been postulated that marine waters extended throughout the length
of the Champlain Valley and into the Hudson Valley, forming a continuous
strip of marine water from the Gulf of St. Lawrence to the Atlantic
Ocean at the mouth of the Hudson River. If this were true, New England
would have been an island only a few years ago (geologically speaking).
The weight of evidence available today does not support the prior
existence of this connecting ribbon of sea water. Today Lake Champlain
contains fresh water again, and the marine conditions have retreated
back into the Gulf of St. Lawrence. What happened to permit a return to
fresh water conditions?

The lakes and lake-stages discussed are known from the presence of
various shoreline features, most of which are now “high and dry.” Each
lake or lake-stage has its own set of lake-level features. An
interesting fact emerges from a study of any one former lake. The
present elevation above sea level of delimiting lake-level features is
_not_ the same throughout. To explain this more fully, the present
elevation of those features formed when the Champlain Sea was at its
maximum extent will be examined.

At Shelburne Falls the present elevation of these features is 300 feet,
at St. Albans 440 feet, and at Roxton, Quebec, 552 feet. It will be
noted that proceeding from south (Shelburne Falls) to north (Roxton) a
difference of over 250 feet is found between features formed at an
identical time in the past. The water in any lake is practically level.
It therefore follows that the present 300, 440 and 552 foot elevations
of the shoreline features are the result of subsequent tilting of the
earth’s surface. Perhaps the following reference to the water level of
present Lake Champlain will help in your understanding of this tilting.

The present-day average level of the water in Lake Champlain is about 92
feet above the level of the Atlantic Ocean. This water-level elevation
is constant throughout the extent of Lake Champlain and _is not_, say,
92 feet at Button Bay and 192 feet at Burlington. Again, the only way
that features demonstrating past lake margins or levels could, for any
one lake or lake-stage, now exist at different elevations would be if
some earth movements took place after the formation of the features,
resulting in a change from their original elevations.

The earth’s crust has been tilted, higher in the north than in the
south, during recent times. This tilting provides the clue to the
formation of present-day Lake Champlain. Major tilting took place after
the maximum marine invasion. Tilting continued, at a decreasing rate,
perhaps, to the present day. This tilting, with greater relative rise in
the northwest, eventually reached a point where marine waters were
excluded from the Champlain Basin.

Fresh water slowly diluted the salty marine water. The lake gathered
more and more fresh water through rain and melting snow, and a new
outlet formed in the north, in the approximate location of the present
Richelieu River. The area of Lake Champlain slowly increased to its
present size, and the clays which once formed lake and sea bottom became
the “hard earth” of the Champlain Lowlands. Continued tilting caused
flooding of the streams, especially in the southern portion of Lake
Champlain, such as the now swampy Otter Creek and its tributary Dead
Creek (see map, Fig. 2). This concludes the story of the Park clays.
From the rocks which crop out within a short walking distance of Button
Bay State Park a much older segment of geologic history can be studied.




                            THE OLDER ROCKS


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.]




                           SUGGESTED READING


_Historical Geology_, by Carl O. Dunbar, John Wiley & Sons, Inc., New
      York, 1960. Good general treatment of what the rocks can and do
      tell geologists about the history of the Earth.

_Handbook of Paleontology for Beginners and Amateurs_, Part 1, The
      Fossils, by Winifred Goldring, New York State Museum Handbook 9
      (obtainable from: Paleontological Research Institution, 190
      Dearborn Place, Ithaca, N. Y.).

_Fossils, An Introduction to Prehistoric Life_, by W. H. Matthews III,
      1962, Barnes and Noble, Inc., New York. Earth history and
      paleontology, a general guide for the amateur collector.

_Bedrock Geology of the Central Champlain Valley of Vermont_, by Charles
      W. Welby, 1961. Vermont Geological Survey Bulletin 14. Standard
      work for the geology in the region of Button Bay State Park.

_Paleontology of the Champlain Basin in Vermont_, by C. W. Welby,
      Vermont Geology Series, Vermont Geological Survey. A treatise on
      the paleontology of the Champlain Basin designed for the amateur.
      In press.

_Index Fossils of North America_, by H. W. Shimer and R. R. Shrock,
      1944, John Wiley & Sons, Inc., New York. Contains many plates
      depicting several of the fossils found in and adjacent to Button
      Bay State Park.




                               Footnotes


[1]Most of the information for this section was graciously supplied by
    Clara E. Follette, Librarian and Museum Director, Vermont Historical
    Society, Montpelier, Vermont, in a letter to the author dated April
    26, 1961.

[2]“The governors (and other gentlemen) appear to have included Sir
    Henry Moore, Governor of New York, General Carleton, Governor of
    Quebec, Brig. General Philip Schuyler (and Adolphus Benzel, map
    maker). The activities of these persons on the lake at that time
    were evidently concerned with making observations, primarily to
    determine boundaries.”

[3]Seely, H. M., 1910, Preliminary Report of the Geology of Addison
    County; Vermont State Geologist, 7th Biennial Report, p. 257-315.

[4]Concretions consist of concentrations of certain chemical elements
    and compounds into regular or irregular masses. Many times the
    center of a concretion consists of a definite nucleus such as a
    grain of sand or shell fragment. For a general idea of the size and
    shape of the concretions seen along the Button Bay State Park beach
    see Fig. 3 and cover picture.

[5]These clays were deposited from marine waters which flooded the
    Champlain Valley after the final retreat of the glaciers which
    completely covered New England during the “Great Ice Age” or
    Pleistocene Epoch. The Pleistocene Epoch began approximately one
    million years ago and if the age of the Earth is considered to be
    five billion (5,000 million) years, then, the clays do record recent
    geologic history.

[6]As the weight of the ice was removed from the Hudson Valley region
    the earth’s crust, in way of adjustment to this removal of weight,
    slowly began to rise. Some geologists doubt whether the removal of
    ice weight alone can account for the crustal rise and propose other
    internal forces as partly or wholly responsible. The fact remains
    that the earth’s crust did rise in this area.

[7]As the ice retreated, a succession of lakes formed in the Champlain
    Valley. Each lake had a level waterline during its history and
    certain lakeshore features formed, as they do in any present-day
    lake, with respect to each past level water-line. For example,
    ridges of sand and gravel were heaped along the shoreline by lake
    waves. Wave-cut and wave-built flat areas or terraces were formed
    along the margins of lakes or along the sides of islands within a
    lake. Streams entering a lake built deltas by depositing materials
    it had carried down from the surrounding highlands.

[8]Elevation is measured in feet above the mean sea level of today, with
    mean sea level being zero feet.

[9]A most impressive view can be gained from any one of the several
    lookout points at the summit level of Mt. Philo. Looking to the
    west, toward Lake Champlain, and south in the direction of Vergennes
    and Button Bay State Park, a three dimensional view of an old lake
    (Lake Vermont) can be seen. In this view the present Lake Champlain
    Lowlands represent the old lake bottom and the numerous hills rising
    above this Lowland were once islands or near-islands which dotted
    the surface of the lake. It takes very little imagination to place
    yourself on the “island of Mt. Philo” and to visualize a boat tied
    to a dock just below the rocky cliffs on which you stand. A trip to
    Mt. Philo with its spectacular view of the Champlain Lowlands (see
    Fig. 6) is recommended.

[10]One word of caution, the Park authorities may import sand from other
    areas of Vermont to improve the swimming facilities along the beach.
    In this case, the abundant sand on the beach will not constitute the
    “natural beach composition” for Button Bay State Park.

[11]The blue color is due to the presence of ferrous iron (bivalent
    iron) together with iron compounds in which iron has its higher
    chemical valence (ferric iron). This ferrous iron demands a
    chemically reducing environment for its formation and indicates that
    the clays were deposited in a shallow sea or that they remained for
    some time beneath a stable water-table. They contained a fair
    quantity of decaying organic material.

[12]The brown color is due to the presence of the ferric hydroxide,
    goethite (HFeO₂).

[13]This fossil whale is scientifically known as _Delphinapterus
    vermontanus_ (_Thompson_).

[14]The pelecypods found are scientifically known as _Macoma
    groenlandica_ and _Saxicava rugosa_.

[15]The size limits of sand lie between 2mm in diameter (largest) and
    ¹/₁₆mm in diameter (smallest). Two millimeters (mm) equals
    approximately ²/₂₅ inches. Fine sand would fall between ¼mm and ⅛mm
    in diameter.

[16]Convolute beds show their layers thrown into a series of folds (some
    quite irregular) which result from the pressing weight of overlying
    sediments on highly plastic layers beneath. Some feel that these
    folds were the result of actual flowage of the layers in the
    direction of their tilt, and others credit the distorted bedding to
    the pressing weight of large boulders. These dragged across the
    layers while still frozen to overriding glacial ice.

[17]The author noted both _Macoma groenlandica_ and _Saxicava rugosa_
    (see Fig. 10 and Plate 1, Sketches 3 and 4).

[18]Fossils are the preserved evidence of past life (animal or plant) as
    found in rocks or sediments, for example, the clams found in the
    clays. They may be direct evidence, such as the actual shells or
    mineralogically replaced shells of long-dead animals; or indirect
    evidence, such as the tracks or trails of animals now preserved in
    rocks.

[19]Geologic time is divided into four Eras which are designated from
    oldest to youngest: Precambrian, Paleozoic, Mesozoic, and Cenozoic.
    Each of these Eras is divided into geologic Periods of time. The
    Ordovician Period is next to the oldest Period of the Paleozoic Era.
    This Period began some 420 million years ago, and ended
    approximately 360 million years ago.

[20]Present Arthropods include the insects, spiders and crabs.
    Arthropods, which are invertebrate animals (without backbones), are
    characterized by jointed legs, chitinous outer covering and
    segmented body parts. Trilobites were very numerous in the early
    Paleozoic seas, but became extinct before the end of that Era.

[21]The folding and the faulting of the Ordovician rocks took place
    sometime between the closing phases of the Ordovician Period and the
    beginning of late Silurian time (between 360 and 330 million years
    ago). Usually these earth movements are ascribed to the Taconic
    Disturbance which took place at the end of the Ordovician Period.

[22]A walk along the beach in the direction of Button Island or “sickle
    point” (west and then south from the northern boundary of the Park)
    traverses the following geologic formations: the Glens Falls
    limestone which can be seen on Ship Point (actually an island off
    the northern end of the Park); the Orwell limestone, seen on Button
    Island; the Valcour formation which makes up “sickle point”; and the
    Crown Point limestone which is found on the Basin Harbor-side of
    “sickle point.” These rock units belong to the Chazyan Stage (Crown
    Point limestone and Valcour formation) and the next younger
    Mohawkian Stage (Orwell and Glens Falls limestones) of the Middle
    Ordovician Champlainian Series.




                          Transcriber’s Notes


—Silently corrected a few typos.

—Retained publication information from the printed edition: this eBook
  is public-domain in the country of publication.

—In the text versions only, text in italics is delimited by
  _underscores_.