Flint Island A natural resources inventory

[From the U.S. Government Printing Office, www.gpo.gov]

Coastal Zone
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FLINT ISLAND- A NATURAL RESOURCES INVENTORY

Con ducted for the Nature Conservancy
by Philip W. Conservancy
1. General

Location: Pleasant Bay, Harrington, Washington

County, Maine

440 2831 30" N. Latitude
670 47' 30" W. Longitude
COSTAL ZONE
Area: 170 acres
INFORMATION CENTER
Relief: 75 ft.
Date surveyed: 6/21/75, 6/22/75, 6/23/75

Description

Flint Island lies approximately 5 miles south

of Harrington in Pleasant Bay. Dyer Island is

directly to the north and Shipstern Island lies

to the west. The coast is rocky,interspersed

with cobble beaches. A rela'ively high bluff

isolated on the northwest side of the island near

the most convenient landing beach makes an

attractive place to camp. The relief is generally

gentle on the north shore and steep on the south

and east. Flint is mostly spruce-fir forest

interspersed with old fields.

Land Use History

The relative distance of Flint from the main-

land and the few landing sites make this island

more remote than all but a few in Pleasant Bay.

The only discernable path on the island travels

from the above-mentioned cobble beach to the old

field bluff. The size of Flint, the dense foi@est'

and steep shores reinforce its inaccessibility.,

According to'J.C. Strout a boatsman from Mil-

bridge, Flint was used for grazing sheep.up until

15 years ago. S igns of grazing are still evident
(see vegetation). Most island,s in this area

were used for grazing since island weather was

less severe; there was less snow and sheep didn't

need to be fed even during the winter. They are

able to forage along the shore to maintain them-

selves. In addition to grazing, lobstermen used

islands for storing nets, buoys, and other gear in

rough structures. On Flint,:in the grove of

spruce near the north head shore there is a store

of weir st.@kOs once iised to hold nets for her-

ring fishing. With the decline of the sardine

industry in Maine, weir fishing for herring has

also declined nd few weir traps are actively

tended.

-In 1972, George Milmine a summer resident of

Harrington donated -the island to the Nature

Conservancy. A small plaque in memory of his

mother has been placed on a rock near the landing

beach.

Though picnickers are not*the rule on Flint,

Outward Bound School at Hurricane Island visits

the island on expedition stop-overs. Two 12-man
boats generally make up an expedition. They bring

their own food, collect any trash left from

other visitors, and remain on the island over-

night except in weather. According to Outward
Bound Director, Peter Willauer, Flint Island is'

used on two or sometimes three occasions between

March and October.

IV,. Geology

The bedrock geology of Flint Island is strik-

ingly different from any other island in Pleasant

Bay and has geological features which taken to-

gether may make it unique to the entire coast of

eastern Maine. The following description of the
bedrock of Flint is heavily dependent on the inter-
pretation of.William J. Metzger from the Department
of Geology, State University College, -Fre@donia,

New York who.visited the island with this writer

and who is in the process of publishing an article

on the - gp 6 lo&r of Flint Island. William Tv7et2ger is

a former student of Carleton Chapman, the foremost

bedrock geologist of the Mount Desert area and.
author of The Geology of Acadia National Park

(1962)0

The geologi cal history of the island is best

viewed by a.wal k along the northern shore of Flint.

Beginning at the landing beach on the north side,

one sees beau'Liful,lavendar-grey-blue Cliffs

flanking the beach on both sides. These rocks, for

quite some distance.along the northern shore,

consist mainly of fine-grained siltstones with

thin, discontinuous lenses of limestone. Inter-

bedded in these water-laid rocks are various vol-@-

canic ashes and tuffs. These whitish cliffs,

striking, in the summer sun, include beds so fine-

grained that they appear "'cherty" or "flinty",

from whence comes the name Flint Island. Along

the north.shore for some distance these rocks dip

to the south and are split by largely vertical

northeast-sout-hwest trending fractures. The

latter, where concentrated, are partially res-

ponsible for the formation of Flint's numerous,:

deeply-incised tlflunderholes. The easily-ercd6d

fracture system also has helped form-lovely,'isol-

ated tide pools and a host of other marine envir"'

onments discussed in a later section (see Marine

Environments).

This entire series of rocks is put by dark

gray basalt and lighter granitic (acidic porphyry)

dikes. These dikes follow the direction of the

fracture system. Mr. Metzger feels that if these

t'10 latter rocks can be dated by potassium-argon

methods in the labortory to be Middle Silurian in

age, as he thinks likely from other evidence, they

then indicate that igneous activity in the,north-

ern Appalachians occurred much earlier than had

been supposed. This latter hypothesis is of con-

siderable scientific and academic importance, mak-

ing the Flint Island white cliffs to be of prime
/I's well as scenic va'
scientifiga lue. Mr. Pletzger

believes this series on Flint to be correlative

if not coeval with the Bar Harbor series on

Mount Desert Island. If so, it is the first con-
tinuity of this series recognized th'is fdr east

of Mount Desert.

Following these cliffs further east, which

previously have been exposed only to rather low-

grade metamorphism, the rocks begin to show signs

of cross bedding. Then, instead of gently dip-

ping to the south, folds and twists became not-

iceable and the.series becomes more shattered and,

distorted. Concretions, or extraneous mineral

masses, become larger and more frequent. To@@,rard
C__

the northeast tip of Flint, t-he rocks undergo a

radical change. Large, angular highly metamor-

phosed, recrystallized rocks are intruded into a

rude shatter zone. Further on, blocks with th.ese

blocks surrounded in turn by magonatic granitic

can be discerned. The flow patterns wit@in these

latter angular, whitish blocks are multi-direct-

ional indicating violent, extrusive volcanic a'c-.

tivity. Mr. Metzger concludes that these rocks

once formed an ancient volcano; were located in

the neck or vent and were torn from the sides of

the volcano during the violent eruptions of Pal-

eozoic times. Again another rock formation on

Flint is of unique scientific and educational

value.

Located at. several points along this northern

shore between the whitish-lavender flinty cliffs

and the highly metamorphosed section is athird

unique geological resourse. In a-dark Eray fine

grained series is a fossil bearing rock, at least

420 million years old. The tiny marine fossils are
crinoids, an echir@derm still preserving its

&I-acked, sauce,r-lil@p structure when viewed in cross

section.- In these gray, pitted rocks on several

beaches one can also find brachiopod, tetracoral,
and -tribbite fossils. These fossils identified

as Silurian marine invertebrates, support Metzger's.

hypothesis of an early Pa.leozoic intrusive history

of eastern Maine coastal plutons.

The surficial deposits on Flint Island are less

dramatic; blue-gray marine clays, de,positbd dur-

ing a coa8tal submergence, underlie th e alder

swamps and bog. The remainder of the island is

topped with a shallow ground moraine, e xcept on.

the high parts of Flint where the soil has been

scraped away by glacial action. The glacier is

also partially responsible for the steep-sloped

southern face of Flint. The glacier "plucked"

volcanic boulders from this lee side.and has

formed not only steep cliffs, but also a giant

step-like descent to the shore composed of large

boulders "quarried" from the cliff behind.

V. Vegetation

1. Spruce-fir.

On the shallow sandy loam tills the spruce and

fir do not grow to anymore than 50 or 60 feet in

height. White spruce, more salt tolerant -than

red spruce, rings the shore line while red spruce

dominates the inland areas. The forest is dis-

tinctly two-aged. The oldest red spruce seat-

tered throughout the areas of lower elevation

were obviously field grown, developing as "wolf"

trees at a time when much of the vegetation was

cropped back by grazing sheep. These are approx-
imately 115 years old. The rest of the pole-sized

spruce '.(--12'-'14 @'DBH)-:-on the- inner, part of."Flih't are,

some 20 years younger than those with thick low

lying branches. One of the dead white spruce proV_
ides a nesting site for a pair of osprey. . The'

herbaceous cover is typical;dominated by jewel

Vleed, bunch berry, lycopodium and wood sorrel in

the cool moist Woods. Blueberry,.grey birch and

creeping juniper are found on the sandy topped-

bedrock outcrops. One white pine is found grow-

ing near one of these outcrops.

2. Alder Swamp

There are at least 4 different alder swamps

where impermeable layers beneath the vegetation

trap ground water run off. One of these is large

enough and persistent enough to have created a

small fresh water acidic bog with white and black
spruce and tamarack, in it. The other alder swamps

are smaller and are most.likely maintained by the

spring and early summer rains. Whereas speckled

alder and gray birch interspersed with variou.s

ferns are the only species found in the latter'

areas, a more complex and interesting flora exists

in and around the fresh water bog. The ground

cover is sphagnum and cotton grass. Black grass

grows near where run off empties on to the beach.

Marsh St. Jbhnswort, labrador.tea,.and rhod6ra

grow in patches in association with the stunted

spruce and tamarack. This fresh water bog is

fast being reclaimed. A peaty soil exists in

places where smooth gooseberry, beach flag iris

and raspberries have gained a hold. The fresh

water bog was almost certainly a tidal marsh at

one point in the long history of lint Island.

Underlying the dark fresh water peat one would

expect to find a lighter colored salt water peat

with flecks of salt marsh grass in it.

As indicated earlier, the bog is underlain partly

by marine clays, though there may be evidence of

a sandy-gravel beach formed before the present

cobble beach closed the tidal inlet off.

Old Field

On Flint, in addition to the numerous areas

showing evidence of having been in field at one

time, there are two Ereen old fields typically

covered with rose, raspberry and a great diversity
of flowering herbaceous plants. The latter in-

clude pearly everlasting, blue-eyed grass, mullein,

sandworts and stitchworts. Mats of ericaceous

plants grow over exposures of ledge at the peri-
pheries of both fields. Crowberry, cranberry,

P,
and blueberry make up these maps.

4. Sea Strand

The flora, of this community is-also discussed

10.

in the Marine Environments secti on of this report.

Depending on the exposures and surficial deposits,

sea plantain, mertensia, sea rocket, milkwort,

beach pea and angelica are common. Ground cherry

and strawberry are found near shore where shallow

soils have developed between rock outcrops. Boreal

fo.rbs, notable seaside -olantain,'iris and bog

aster occur especially where seaward expos ures

are wet by frequent coastal,fogs. Growing on

L,op of ledge exposures on the steep north and
east faces of Flint are particularly beautiful

mats of ericaceous shrubs, which when in flower.

and fruit strike a stunning contrast with the

whitened rocks of the Bar Harbor Series. Red-

fruited mountain cranberry, black fruited crow-

berry crowd under and around the pink flowered

small cranberry. From grassy areas above these

mats, the fragile bcreal perrenial artic beach

flag grows. According to Paul Favor, retired

chief Naturalist of Acadia Park, this arctic

beach flag grows only on a few isla.nds.in Penob-

scot and Frenchmants Bays.

V1. Wildlife

A nesting osprey is the most visible member of

the wildlife community of Flint. Since Flint

is remote the pair of osp rey were distinctly

less. used to human disturbance than other osprey

nesting closer to shore. Two nestlings were ob-

served from the vantage of a nearby tree. Other

large birds were seen continuously off shore in-

cluding guillenot, black-backed and-herring gulls,

and eiders. On the southeastern tip of Flint Is-

land there is good evidence of nesting Leach's

Petrel. The large droopin g mats of crowberry and

cranberry have formed a shallow loose soil where

digging is easy and protection is improved by

burrows dug back into the unincorporated organic

matter.

Less visible, but perhaps more significant

fauna associated with Flint Island are the harbor

seals observe,d playing and feeding off the-ledges

on the north side. Other ledges are,found off the

southeastern side o,f Flint but cormorants and

gulls were the only animal life observed. It'is

not known whether these ledges are used by harbor

or' grey seals as whelping sites, but given the

current-extention of bo th species range and num-

these ledges should be reEarded as potential.

areas for pups to be born.

Vll. Matine Environments

Partially as a result of Elint's unique geol-

ogic history and partially as a result of its

geographic location in southernmost Pleasant Bay,

Flint Island's shore environments are very diverse.

12..

Four such beaches.are found on the island:

l.-,Gravel beach

Wave-accumulated gravel,particles have been dep-

osited in the inter-tidal zone from storm high tide

to mean low tide. Mostly boulder and cobble sized

particles. These beaches are.well--sorted as they

are inundated twice daily by tides. The beach to

the south, exposed to high wave energ
y, storm winds

and storm tides has formed a double-decked seawall.

During severe storms the cobbles may be hurled

shoreward and tossed over its crest. The landinc,

s1lore on the north side is a beautiful cobble beach

formed IF'rom the same rocks as the nearby outcrop of

Bar Harbor Series. The laminated nature of these

when rounded and weathered are all of interesting

texture and composition. Vegetation at the heads

of these beaches includes beach pea, vetch, sea

rocket, scotch lovage,, willow herb and sea blite.

Particularly large and pretty mats of oyster leaf,

when in flower in early Augustioffer soft lavendar

blue hue as contrast to the nearby rocks.

2. Lowtide terrace

Lowtide terrace is a flat platform of mixed

sand and pebble-sized gravel just seaward of gravel

beaches where it is found. These terraces are

often the longshore current deposits which have

13.

passed over cobble beaches and carried off the

smaller particles. Subsequently transport is both

onshore and alongshore. Such areas are ex posed

only at low tide, are permanently water' saturated

and support no vegetation.

3.- Tidal channel

This environm ent is described as an elongate

intertidal or subtidal channel- composed of either

coarse sand, shell, gravel or exposed ledge. On

Flint the channel is formed in the area between

the above-mentioned northern ledges and the rocky

shore. Its bottom is muddy and supports an

extensive mussel bed of Dotential cornmercial-val-

ue. Algal vegetation includes wrack, rockweed,

and Irish sea moss. Marine invertebrates in this

environment are barnacles, periwinkles, green

crabs, rock crab and sea urchins. This tidal

channel is an important feeding ground for.eiders
and gulls. On two of the three visits to Flint

the bald e agles which nest on Shipstern were

seen flying over the ledges and probably use

them for their shellfish and scavenEe at low tide.

On one occasion, a young eagle was chased off by

the osprey, a resident on the opposite side of the

island.

4.Ledge

The intertidal and subtidal bedrock outcrops

are exposed to a high wave energy climate.. On

certain exposed ledges, particularly those of the
eastern side of Flint, one sees.good examples of

intidal zonation of algae. . Green algae occupy the
small niches nearest mean high tide leve 4 n tide
pools of the Bar Harbor Series. Brown wrack and'

rockweed are found underneath, and occupying

.niches under-them are the red dulse and kelps.

As mentioned above,these ledges, both off the

northeastern and southeastern faces of Flint, are

important habitat for seal.

V,111. Critical Areas

From both scenic and scientific poihts of
view the various geological features on Flint

Island are of a degree of significance to estab-

lish them as critical areas according to -the

States definition contained in the Critical Area

Act. These geological features include the

whitish-lavendar cliffs of the north edge of

Flint, the fossiliferous sequence along the same

edge and@the evidences for the presence of an

ancient volcanic neck on the northeast tip of

Flint.

The osprey nest annually Isupports a pair of

these hawks and their young. Os.prey nests are

15.

generally included on critical ar-eas registers.

If Leach's petrels are found to be nesting

along the eastern and southern edges of Flint,

these places should be placed under the classif-

ication of a critical area.

In summary, the critical areas or features of

Flint Island are:

(1) the northern shore cliffs

(2) the marine fossils in sliore rocks

(3) the volcanic neck

(4) the osprey nest

(5) possible nesting Leach's petrel

JX. Manapement Recommendations

With -the exception of the possibility of

nesting petrels, none of the critical features

on Flint Island are easily disturbed by moderate

use of the island. Some of the fossils could be

taken from Flint, but. since they are tiny and

require identification by one with substantial

geologic knowledge, this problem is not likely

to arise.

There is no reason, in the writer's opinion,

to prohibit all camping on Flint. Since it is

remote, access difficult,, and the forest dense

and swampy in many spots, overuse of Flint Island':

resources has not occurred. As long as this con-

16.

dition prevails, occasional visits by Hurricane.

Island Outward Bound expeditions should pose no

serious problem.

X. Species List bV Vegetational Community

A. Spruce-Fir

scientific name common name

Abies balsamea balsam fir
Betula papyrifera white birch
B. pupulifolia grey birch
Clintonia borealis blue bead lily
Cornus canadensis bunchberry
Equisetum arvense horsetail
Impatiens capensis jewel weed
Lycopodium obscurum lycopodium
Mianthemum canadensis Canada mayflower
Monotropa uniflora indian pipe
Osmunda cinnamomea cinnamon fbrn
Oxalis montana wood sorrel
Picea glanca white spruce
P. rubens . red spruce
Pinus strobus white pine
Sorbus americana mountain ash
Trientalis borealis twin flower

B. Alder Swamp and :R-,og

Alnus crispa common alder
Aster nemoralis bog aster
Betula populifolia* grey birch
Cotton grass cotton grass
Dryopteris theypteris marsh fern
Hypbricum virginicum marsh St. Jbhnswort
Juncus voemarianas black rush grass
Larix laricina eastern larch
Ledum groenlandicum labrador tea
Picea mariana black spruce
Ribes hirtellum smooth gooseberry
Sphagnum s-P. sphagnum
Viola sD. violets

C. Old Field

Achillea millefolium yarrow
Arenaria laterf-lora grove sandivort
Aster siD-P. aster

17.

Old Field, cont.

Circeum arvense sow thistle
Euphrasia americana eyebright
Fragaris virginiana strawberry
Hieracium. pratense king devil
H. spp. hawkweed
Iris versicolor blue flag iris
Juncus spp. grasses
Juniperus communis juniper
J. horizontalis juniper
Oenothera biennis evening primrose.
Prunella vulgaris seal-heal
Prunus maritimus ground cherry
Rhinanthus crista-galli yellow rattle
Rosa rugosa rugose rose
Rubus allegheniensis blackberry
R. flagellaris dewberry
R. strigosus red raspberry
Rumex acetosella field sorrel
Sisyrinchium mucronatum blue-eyed grass
Solidago spp goldenrods
Scnchus spp thistles
Spirea latifolia meadowsweet
Stellaria graminea grove sandwort
S. sp. chickweed
Vaccinium angustifolia low blueberry
Verbascum thapsus mullein
Viola spp. violets

D. Sea-Strand

Angelica atropurpurea Alexander's angelica
Atriplex patula orach
Cakile endulata sea rocket
Empetrum. nigrum crowberry
Epilobium leptophyllum narrow willow herb
Glaux maritima sea milkwort
Iris sp. arctic beach flag iris
Juncus voemarianus black rush grass-
Lathyrus maritima beach pea
Ligusticum scothium scotch lovage
Mertensia maritima oysterleaf
M. virginica blue bells
Plantago oliganthos sea plantain
Pramanthes sp. licus foot
Scutellaria epilobiifolia marsh skullcap
Suaeda maritima sea blite
Vaccinium oxycoccus small cranberry V. vitus-idaea mountain-cranberry
Vicia cracca cow vetch

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