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