Fig. 3. Photographs of peat fragments from two large samples.
(A) Fibrous peat from sample RL 3 that shows holes bored by
pelecypods into the top surface, indicating that the peat was
broken from a larger mass that had remained in an undisturbed
(B) Peat
position on the sea floor for a long period of time.
from sample RL 2 showing abundant pieces of wood enclosed
in a fibrous matrix.
2 along with notations of the kind
of wood that was present. The pollen
counts provided the basis for assignment of the samples to pollen zones
A, B, and C, respectively. Several samples also contained pollen of Nymphaea
(water lily), Cyperaceae (sedges), Sagittaria (arrowhead), or abundant fern
spores, or all of these, which provides
additional evidence of their freshwater
origin.
Efforts to construct standard pollen
sequences of general stratigraphic and
chronologic application to late glacial
and postglacial climatic and vegetational history of New England have resulted in the generalized scheme given
in Fig. 4. The major palynological
divisions, designated zone A (spruce
dominance), zone B (pine dominance),
and zone C (oak-mixed hardwood
dominance), have repeatedly been veri-
fied
from
intensive
study
of
both
coastal and inland postglacial sediments
from the northeastern United States.
Although analyses of specific palynological sequences may differ in detail.
climatic control of the basic vegetational succession can be demonstrated
in the samples studied in this investigation (Table 2). It should be noted, however, that latitude influences the chronology of this sequence of forest transition. For example, the transition from
zone A of spruce dominance to zone
B of pine dominance clearly took place
Table 2. Identified pollen and wood in peat samples. P, present; D. dominant: n.s., not significant.
No.
Water
Fir
OP 1
Spruce
0
0
BS
0
<5
BARN
0
RL 3
B 3
M 28
AL
Vv
0
2
1
0
0
RLi
Pine
Oak
22
40
liky
and ‘or
sedge
ns.
18-50
2-28
20-58
0
30
47
0
0
15
26
12
36
17
60
60
73
13
20
7
2
2
3
5
6
6
2
10
P83
9
BT 9A
0
0
P
3
7
21
15
16
15
4
11
E 1
BOS
SO
TB.
ROG
2
12
8
2
<5
0
5
ers
Wood
38
zone
C
?
References
(36), Fig. 7,
2.0-2.7 m
Cc
(37), Fig. &,
23
Cc
(32), Fig. t,
58
10
10
9
38
Cc
B
B
A-B
A
8
56$
5
4
11
634
4
1
50
>384
22
2
35
36
Juniper
Spruce
Juniper
Birch
Lower Peat
327 inches
:
(28)
(28)
A
A
A
A
A?
A
A
A
See also (38),
Fig. 1, 43-49 em
(36). Fig. 7,
13.1~-13.5 m
(33)
(39), Plate 1
(40)
(30), Fig. 3A,
14.5 m
Conifer
* Nor stated in publication.
rédeposited
fern
spores.
1304
Oth-
0
1s.
G 2198
sphagnum
Pollen
Dt
RL 2
OP 2
spores,
+ Pure sphagnum peat. a freshwater indicaior.
{Mostly worn and
§ Abundant
Ericacea.
| Mostly
birch.
Includes
fern | spores,
Lyeopedium,
and
len spectar B3 and M 28 from near
the mouth of Chesapeake Bay, and of
E 1 (fable 2) that is far out on the
shelf at about the same latitude. The
age of the first two samples, in terms
of New England forest history, would
indicate occurrence in zone A; instead,
they are in zone B, in which pine
rather than spruce is dominant. The
third sample has pollen ratios that differ
from those of New England for the
same date, but they still indicate zone
A, Apart from these three samples, the
_ pollen zones and the radiocarbon dates
of peat samples from the more north-
easterly areas agree closely (Fig. 5).
Accordingly, two samples (V and AL)
Pollen percentages
Sample
at an earlier date in the southern parts
of the New England coastal plain than
in the more northern and uplandsites.
The generalizations regarding the latitudinal variations of the major forest
transitions are verified by the two pol-
arrowhead.
an
that were too small for radiocarbon dating can be approximately dated by their
pollen content.
Support for the freshwater origin of
several samples of matrix and wood
is provided by measurements of stable
carbon isotopes. As shown in Table
3, the §C'3 measurements are between
—23.5 and —27.8 per mil, in contrast
to measurements of between —11.6 and
—15.5 per mil for six samples of salt-
marsh peat from Barnstable salt marsh
at approximately the same position as
BARN (Table 1 and Fig. 2). Each of
the sets of measurements is well within the range that characterizes freshwater organic matter and marine organic materials, respectively (14). We
were surprised that the value for salt-
marsh peat was so clearly typical of ma-
rine plants, in view of the fact that the
peat surface is exposed to the air a
large part of the time. This point was
further investigated by determining the
' §C'8 fpr.a composite sample of the
SCIENCE, VOL, 158