Palaeogeography of Atlantic Canada 13–0 kyr

Quaternary Science Reviews 21 (2002) 1861–1878

Palaeogeography of Atlantic Canada 13–0 kyr J. Shaw*, P. Gareau, R.C. Courtney Geological Survey of Canada, Bedford Institute of Oceanography (Atlantic), P.O. Box 1006, Dartmouth, Nova Scotia, Canada B2Y 4A2 Received 1 May 2001; accepted 27 December 2001

Abstract We combine isobase maps with a digital terrain model of Atlantic Canada to map coastlines from 13 14C kyr BP to the present. At 13 14C kyr BP there are ridges of high relative sea level (rsl) values over Newfoundland and the Maritime Provinces, and a re-entrant of low values in the Gulf of St. Lawrence. This pattern persists well into the Holocene, and reflects crustal response to the slow wasting of ice caps that persisted in Newfoundland and the Maritime Provinces for up to five millennia after the removal of ice from the Gulf of St. Lawrence by a migrating calving embayment. The palaeogeographic reconstructions reveal an archipelago on the outer shelf, from Grand Bank to the continent, that persisted from >13 14C kyr BP until ca. 8 14C kyr BP. Much of the Magdalen Shelf was exposed, but the Magdalen Islands were never connected to the mainland. Prince Edward Island was initially separated from the mainland, became connected after 11 14C kyr BP, and was separated again just before 6 14C kyr BP, when Northumberland Strait formed. The reconstructions are highly sensitive to relatively small changes in isobase values, especially on the shallow banks on the continental shelf. r 2002 Published by Elsevier Science Ltd.

1. Introduction Numerous sources provide evidence of lowered postglacial relative sea levels on the continental shelves of Atlantic Canada (Fig. 1), from which substantive geographic change must be inferred. Fader (1989) reviewed stratigraphic and geomorphic evidence for a ‘‘widespread, submarine, low sea-level stand’’ that occurred at a ‘‘present depth of 110–120 m across the Scotian Shelf’’. In the Bay of Fundy, terraces shallowed to a depth of 37 m (Fader et al., 1977). In the Gulf of St. Lawrence, sea-floor terraces along the edge of the Magdalen Shelf, at depths of 100–120 m, have been interpreted as indicating a brief sea-level stillstand at that depth (Loring and Nota, 1973). Josenhans and Lehman (1999) argued for a 120 m postglacial sea-level lowering in the southern Gulf, and terraces at various depths in Northumberland Strait led Kranck (1972) to infer postglacial sea levels below the modern level. Notwithstanding this evidence, there have been few attempts to map the postglacial palaeogeography of *Corresponding author. Tel.: +1-902-426-2396; fax: +1-902-4264104. E-mail address: [email protected] (J. Shaw). 0277-3791/02/$ - see front matter r 2002 Published by Elsevier Science Ltd. PII: S 0 2 7 7 - 3 7 9 1 ( 0 2 ) 0 0 0 0 4 - 5

Atlantic Canada, in part because the region has a complex, regionally and temporally varying rsl history, which has meant that the collection and compilation of index points has been slow. Furthermore, much of the region submerged during the Holocene, and the collection of index points from relatively deep water is difficult, expensive, and potentially fraught with interpretive problems. A benchmark palaeogeographic reconstruction (Dyke and Prest, 1987) shows the palaeogeography of Canada from 18 to 5 14C kyr BP. Large islands existed on the Atlantic continental shelf from 18 kyr until after 11 kyr, with Georges Bank connected to the continent by a peninsula in the west. The Magdalen Islands were connected to the mainland until after 13 14C kyr BP, and Northumberland Strait flooded and Prince Edward Island became an island after 5 14C kyr BP. Areas closer to the centre of the Laurentide Ice Sheet (e.g. North Shore of the Gulf of St. Lawrence) emerged throughout most of the postglacial period. Dyke (1996) presented a similar picture. The reconstructions extended only to the western part of the Grand Banks of Newfoundland, which were depicted as emerged at 14 14C kyr BP but not at 13 14C kyr BP. Bousefield and Thomas (1975) showed a very large island on Grand Bank at 12.5 14C kyr BP; it

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1862

Great Northern Peninsula

Quebec

Newfoundland Ca

18

t.

ur

en

tia

n

8 9

Grand Banks of Newfoundland 2 3

7 6 5

1

el

y nd

4

La

n an Ch

Nova Scotia

u

fF

yo Ba

tS

Prince Edward Island

New Brunswick USA

bo

12

10 f el 11 Sh n 13 otia 15 Sc 14

Gulf of Maine

16 17

1 2 3 4 5 6 7 8 9 10

Grand Bank Green Bank St. Pierre Bank Burgeo Bank Banquereau Artimon Bank Misaine Bank Canso Bank Middle Bank

11 12 13 14 15 16 17 18

Emerald Bank Sambro Bank LaHave Bank Roseway Bank Baccaro Bank Browns Bank Georges Bank Magdalen Shelf

Sable Island Bank

Fig. 1. Map of the study area, with offshore banks numbered.

was considerable shrunken by 9.5 14C kyr BP, and barely remained above water at 7.5 14C kyr BP. There have also been attempts to reconstruct the palaeogeography of smaller areas. For example, Grant (1975) showed a situation at 8 14C kyr BP when Georges Bank was a large peninsula, separated by a narrow strait from an emergent Browns Bank. Forbes et al. (1993) mapped extensive changes in the geography of the Port au Port/St. George’s Bay area (west Newfoundland) at 9.5 14C kyr BP, and Shaw and Edwardson (1994) demonstrated comparable changes on the northeast coast of Newfoundland. A considerable amount of new relative sea-level data has become available in recent years, making it possible to attempt improved palaeogeographic reconstructions of the postglacial geography of Atlantic Canada. In addition, there have been advances in the use of computer technology, specifically Geographic Information Systems (GIS), so improved tools now exist for the task. Our objectives, therefore, are to present new reconstructions of the distribution of land and sea in Atlantic Canada from 13 14C kyr BP onwards.

2. Study area The Northeast Newfoundland Shelf (Fig. 1) is relatively deep, and channels extend into fiords >600 m deep (Shaw et al., 1999). The Grand Banks of Newfoundland consists of Upper Palaeozoic and Tertiary rocks (Fader et al., 1982; Grant and McAlpine, 1990), and is separated from the mainland by basins. Several small banks similarly isolated are Green Bank, St. Pierre Bank, and Burgeo Bank. The Laurentian Channel is >400 m deep and extends from the shelf edge northwards into the Gulf of St. Lawrence, bifurcating around Anticosti Island. The Scotian Shelf comprises a series of shallow banks: Banquereau, Sable Island, Emerald, Middle, Canso, LaHave, Roseway, Baccaro, and Browns. Northeast Channel extends from the shelf edge into the Gulf of Maine. The bank to the westFGeorge’s BankFextends to the United States coast at Cape Cod. The shallow ( 40 m) Northumberland Strait separates Prince Edward Island from the mainland. To the north lies the Magdalen Shelf, a wide shallow platform bounded on

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

the north by the northwest extension of the Laurentian Channel.

3. Methods

1863

Canada. The final present day Atlantic Canada DEM (Fig. 2) has a 1 km grid resolution. Using Arc/Info’s GRID module, we subtracted the relative sea level change surface from the present day Atlantic Canada DEM to produce new palaeo-DEM for each 1 kyr time slice.

3.1. Derivation of palaeobathymetry Relative sea-level values were extracted from published radiocarbon-dated curves for 1 kyr intervals (all dates mentioned are 14C yr BP). The source curves are listed in Table 1. We also used two ICE-4G predicted curves supplied courtesy of R.W. Peltier, and converted the dates from sidereal to radiocarbon years before using. We are aware of several sources of potential error in our work. First, because of plateaus in calibration curves, particularly for radiocarbon dates in the 10–13 kyr period (see Stuiver et al., 1998), calibrated radiocarbon dates can have large ranges. Second, radiocarbon chronologies of the various sea-level curves have not been standardized; some laboratories automatically corrected shell material to d13C=0%, whereas others provided shell dates ‘‘normalised’’ to d13C=25%. Third, researchers commonly applied a 400-yr reservoir correction. However, reservoir age has varied spatially and temporally. Thus, Bard et al. (1994) argued that atmosphere-sea 14C difference was roughly 700–800 yr during the Younger Dryas event, whereas today it is 400–500 yr. None of these problems have been addressed with regard to the data complied for this paper. Relative sea-level values were plotted on maps, and isobases were drawn manually. Digital versions of the isobases were generated by on-screen digitizing within the MapInfo GIS software. The isobases were then exported out of MapInfo as E00 files and imported into ESRI’s Arc/Info GIS software. Using Arc/Info’s TIN (Triangulated Irregular Network) module, each 1 kyr isobase layer was used to generate a gridded (1 km resolution) relative sea-level change surface. A digital elevation model (DEM) was produced for present day Atlantic Canada (both topographic and bathymetic). The bathymetry data sources consist of: digital 1:250,000 Natural Resource Chart bathymetric contours, digital 1:1,000,000 NESS bathymetry contours, and a digital point dataset derived from the Geological Survey of Canada/Canadian Hydrographic Service northwest Atlantic bathymetric single beam survey data set (1950–1980s). The topographic elevation source data are based on the United States Geological Survey GTOPO30 gridded 30-arc seconds DEM of the world. We discovered that these data were seriously in error in western Anticosti Island, in the Gulf of St. Lawrence. We remedied this problem by replacing all Canadian data with data from the Canada3D 30 arc-second DEM, available from Natural Resources

3.2. Postglacial modification of bathymetry Bathymetry has changed substantially in some areas due to postglacial sedimentation. However, thick deposits of postglacial mud (see Fader et al., 1982; King and Fader, 1986; Shaw et al., 1999), are in relatively deep basins, and do not affect the reconstructions to any great extent. On the other hand, sediment thickness is a concern in shallow areas. For example, 20 m high sand waves formed on Georges Bank in the postglacial period (Emery and Uchupi, 1972) and the Holocene sand-ridge complex at Sable Island is up to 50 m thick (Amos and Nadeau, 1988). Other offshore banks with significant sand deposits are Middle Bank, Banquereau Bank, and Sable Bank. Milne Bank, a shoal off the eastern tip of Prince Edward Island, is about 40 m thick, and appears as a peninsula on the 6 14C kyr BP reconstruction. This is incorrect, because the shoal formed during the past few thousand years (Shaw et al., 2000b). Neither can postglacial erosion be discounted. Large moraines may have existed on submarine banks, and may have been eroded during sea-level lowering (e.g. Middle Bank and Browns Bank, G.B. Fader, pers. comm., 2001). Erosion has significantly deepened the sea floor in places. For example, a trough down the middle of Chignecto Bay is about 20 m deeper than the hydrographic chart indicates, suggesting continuing erosion of the seabed by currents (D.R. Parrott, pers. comm., 2001). By and large, changes due to erosion and deposition do not significantly affect the palaeogeographic reconstructions, and where they do (e.g. eastern Prince Edward Island, see above), we are aware of the scale of problem.

4. Relative sea-level curves We have relied on various authors’ published rsl curves, irrespective of whether there are a large or small number of index points. The rsl sites were assigned numbers (Fig. 3). We use the nomenclature of Quinlan and Beaumont (1981) to describe the shapes of rsl curves: type A (rsl falling continuously); type B (rsl dropping below the modern level before rising once more); type C (rsl always below the modern level, but dropping for a time to a lowstand, then rising); and type D (rsl always rising). Curves shown in Fig. 4 illustrate the variation of sea-level histories in the region.

1864

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

Table 1 References for sites with rsl information Northeast United States 1 2 3 4 5 6 7 8 9 10 53

Clinton, Connecticut Barnstable area, Maine Plum Island River, Maine Boston, Massachusetts Wells, Maine Gulf of Maine Phippsberg, Maine Goldsboro, Maine Machiasport, Maine Odihorne Pt., New Hampshire New York City

Pirazolli (1991) after van de Plassche et al. (1989) Pirazolli (1991) after Redfield and Rubin (1962) Pirazolli (1991) after Keene (1971) Pirazolli (1991) after Kaye and Barghoorn (1964) Gehrels et al. (1996) Barnhardt et al. (1995) Gehrels et al. (1996) Gehrels et al. (1996) Gehrels et al. (1996) Pirazolli (1991) after Keene (1971) Pirazolli (1991) after Newman et al. (1971)

New Brunswick 11 13 14 15 16

Mary’s Point Bocabec Lake Fort Beausejour Baie Verte Shippegan

Scott and Greenberg (1983) Scott and Medioli (1980) Scott and Greenberg (1983) Scott et al. (1995) Thomas et al. (1973)

Newfoundland 17 18 19 20 21 22 23 24 25 26 27 28 30 31 32 33 34 35 36 37

St. John’s Bay d’Espoir Port au Port La Poile Bay Hall’s Bay Bay of Exploits Hamilton Sd. Port Saunders South Port Saunders North Blanc Sablon, Labrador Pinware, Labrador Goose Bay, Labrador Groswater Bay, Labrador Makkovik, Labrador Hopedale, Labrador Nain, Labrador Okkak, Labrador South Torngat, Labrador Central Torngat, Labrador Cape Chidley, Labrador

Lewis et al. (1987) Shaw, unpub., Shaw and Forbes (1995) Forbes et al. (1993) Shaw, unpub., Shaw and Forbes (1995), Shaw et al. (2000a). Shaw et al. (1999) Shaw et al. (1999) Shaw et al. (1999), Shaw and Edwardson (1994) Grant (1994), modified after Renouf and Bell (1998) Grant (1994) Pirazolli (1991), after Bigras and Dubois (1987) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992) Clark and Fitzhugh (1992)

Nova Scotia 40 41 42 43 44 45

Chebogue Harbour Squally Point Chezzetcook Lunenberg Bay Granville Ferry Offshore Halifax

46 47 48 49 50

Chignecto Bay Amherst Point Kingsport Boot Island New Brunswick border

Scott and Greenberg (1983) Stea (2000) (www site) Scott et al. (1995) Scott and Medioli (1982) Scott and Greenberg (1983) Edgecombe et al. (1999), Stea et al. (1994), Shaw et al. (1993), Forbes et al. (1991) Amos and Zaitlin (1985 Shaw and Ceman (1999) Scott and Greenberg (1983) Grant (1970) Scott et al. (1987)

Prince Edward Island 54 55 56 57 58 59 60

Basin Head Northumberland Strait East Orwell Bay Northumberland Strait West Tryton Pisquid Percival River

Palmer (1974) after Kranck (1972) Scott et al. (1981) after Kranck (1972) Scott et al. (1981) Scott et al. (1981) Scott et al. (1981)

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1865

Table 1 (Continued). Quebec 61 63 64 65 66 67 68 69 70 71 72 73 89

Riviere-du-Loup Matane Tadoussac Ste. Fabien-sur.Mer Rivi"ere-la-Madelaine Haute Cote Lac St. Jean Anticosti Island west Ste. Anne-des-Monts Natashquan-Harrington Moyenne Cote Sept Isles Baie des Chaleurs

after Dionne (1990), Dyke and Peltier (2000) Dionne and Coll (1995) Dionne and Ochietti (1996) Pirazolli (1991) after Dionne, (1988) Gray (1987) Pirazolli (1991) after Bigras and Dubois (1987) Pirazolli (1991, after Hillaire-Marcel (1979) Grant (1989) Pirazolli (1991), after Hillaire-Marcel (1979) Pirazolli (1991) after Bigras and Dubois (1987) Pirazolli (1991) after Bigras and Dubois (1987) Pirazolli (1991), after Hillaire-Marcel (1979) after Bail (1983) and unpublished data.

Outer shelf 91 92

Sable Island Grand Bank

Peltier (unpubl.) Peltier (unpubl.)

Fig. 2. Shaded relief image of the Atlantic Canada DEM used for the reconstructions.

4.1. Northeast United States The curves for this region (1–10, and 53) are mostly short (typically o6 kyr) and show submergence. At site

4 (Boston) rsl has been rising since at least 10 14 C kyr BP, and at site 53 (New York City) since at least 9 14C kyr BP. The longest record (site 6, Gulf of Maine) is a type B, with rsl dropping from +70 m at 13

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1866

81

37

60 N

36

78 77

35 34 33

56 N 32 30

31 28 52 N

26 27

70

67

66

65

24

69

23 21 19 20

63

89 16 5760 5859 54 11 50 15 56 55 13 46 4148 14, 47 49 8 42 7 9 44 45 43 40 5 6 10 4 3 1 2 68

48 N

64

25

71

7372

22 18 17

61

44 N

53

72 W

68 W

64 W

92 91

60 W

56 W

52 W

Fig. 3. Locations of sites with relative sea-level data. References shown in Table 1.

evaluation (Bell and Renouf, 1996; Renouf and Bell, 1998) suggests that the curve for the area is actually type A, so a modified version of Grant’s curve has been adopted. Curves for sites 21, 22 and 23 show a transition from type A in the west (21) to type B in the east (Shaw and Forbes, 1990; Shaw and Edwardson, 1994; Shaw et al., 1999). Curve 19 (Forbes et al., 1993), developed from earlier work (Brookes et al., 1985; Brookes, 1969), shows rsl falling from +44 m to a postglacial lowstand of 25 m at ca. 9.5 14C kyr BP. The lowstand has just been validated by a radiocarbon date of 9410750 BP (Beta-150564; 410 yr reservoir correction applied) obtained on shell contained in bottomset beds of a lowstand delta off Flat Island spit (described by Shaw and Forbes, 1992). Submerged Holocene deltas record the spatially and temporally varying postglacial rsl lowstand along the south coast of Newfoundland (Shaw and Forbes, 1995). Relative sea level at La Poile Bay (20) fell to a 30 m lowstand ca. 10 14C kyr BP (Grant, 1989; Shaw et al., 2000a). Confidence in this has been enhanced by a new radiocarbon date of 9340740 BP (Beta-150565; 410 yr reservoir correction applied) on shell in postglacial mud immediately overlying bottomset beds of a lowstand delta in nearby White Bear Bay. At Bay d’Espoir (18) rsl fell from +50 m at ca. 12.5 14C kyr BP to a wellconstrained lowstand of 16 m at 8.5 14C kyr BP. At St. John’s (93) there is only a single data point. It shows that rising sea level flooded the 14 m sill by 10 14 C kyr BP (Lewis et al., 1987). Clark and Fitzhugh (1992) are the source of the bulk of the rsl information for Labrador (curves 27, 28, and 30–37). The isobases derived from these data parallel the coast, and show falling rsl throughout the postglacial period. The exception is at the northern tip of the Labrador Peninsula (37, Cape Chidley) where rsl fell below the modern level at 7 14C kyr BP. 4.3. New Brunswick

Fig. 4. Examples of relative sea-level curves used to plot isobases, extracted from original curves at 1 kyr intervals. Numbers refer to Table 1.

14

C kyr BP to et al., 1995).

55 m at 11–10.5

14

C kyr BP (Barnhardt

4.2. Newfoundland and Labrador Curves 24 and 25 are from the north of Newfoundland (Grant, 1994). Curve 25 is type A. Curve 24 is a type B, with a marine limit at +120 m and rsl falling below present sea level after 7.5 14C kyr BP. Re-

There are five rsl curves for New Brunswick (11 and 13–16). Curves 12 and 13 show rsl dropping below present level at 6 and 7 14C kyr BP respectively. Site 16 is Shippegan, in northern New Brunswick, where shells at sea level, dated at 12.6 14C kyr BP, were interpreted as indicating rsl dropped below modern level ca. 12 kyr (Thomas et al., 1973). However, the rsl curve for this site (see also Grant, 1989) was not used because there was no information on the depth and age of the postglacial rsl lowstand. 4.4. Nova Scotia At site 41 there is only one index point, showing that rsl stood B+40 m ca. 13 14C kyr BP (Stea, 2000).

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

Similarly, there is only a single point at 49, showing that rsl was 12.5 m at 4 14C kyr BP. Curves 46 and 50, from northern Nova Scotia, are type B, with rsl falling to relatively shallow depths (B 30 m) in the early Holocene. Curve 43 shows a postglacial lowstand at about 33 m at 9 14C kyr BP. The rsl curve for the area off Halifax, Nova Scotia, has been evolving since the early 1990s (Forbes et al., 1991; Shaw et al., 1993; Stea et al., 1994; Edgecombe et al., 1999). It displays a type C response, with rsl falling to a lowstand of 65 m at 11.3–11.7 14C kyr BP, before rising, rapidly at first, and less rapidly after 11 kyr. The Bras d’Or Lakes in Cape Breton Island, northeastern Nova Scotia, were marine after deglaciation, became fresh in the early Holocene, and returned to marine conditions ca. 5000 14C years ago when a 8 m sill was overtopped by rising sea level (de Vernal et al., 1985; de Vernal and Jette! , 1987). However, unpublished seismic and multibeam bathymetry data show that the level of the lakes fell to 25 m in the mid-Holocene, suggesting a deeper sill than was previously envisaged.

52 N

13 kyr

Nevertheless, the lake history noted above, and new (unpublished) evidence of lowered sea levels around coastal Cape Breton, are consistent with the isobase pattern obtained for this study. 4.5. Prince Edward Island Site 54 is a very short (3 kyr) record from the east end of Prince Edward Island (Palmer, 1974). The estimate that rsl was 10 m at 3 14C kyr BP may be in error, because dates were on bulk organic material, and may be too old due to incorporation of old carbon (as is common in salt-marsh settings; see Shaw and Ceman, 1999). Several unpublished radiocarbon dates and comparison with sites 55, 56 and 58–60, suggest that 3–6 m of submergence may be more likely in that time. The records at sites 55 and 57 are relatively long, and are based largely on dates on oysters, peat and shells from Northumberland Strait (Kranck, 1972). Data at site 55 show a type C response, with a lowstand at 48 m. Curve 57 is a type B, and is based on a single date from

52 N

110

1867

12 kyr

77 94

148

80

130

52

0

110

48 N

52

60

23

7

57

31

93

18

83

50

46

48 N

25

-10 35 2.5

0 130

0

30

12

44

70

72 W

52 N

8037-9

-40 -58

-18.5

52 W

11 kyr

48 W

-22.5

45

72 W

52 N

53

31

122

35

48 N

192

48 N

10 -18 -10

0

12

80

4

-10

-7.5 -14

-36

-40

-7.5 19 20

-82

-30

44 N

-74

-37 -79

-20

-80

-80

-20.5

72 W

68 W

64 W

60 W

-12

-24

-42 -88

27

97

-40

-50

48

-25

-22

40 8

25

-26.5

44 N

31 36

92

-23

-18

0

53

-30

0

120

40

45

30

74

-3

-20

56

120 80

0

44

48 W

37

16

70

52 W

56 W

60 W

10 kyr

66 67

-80

-95

64 W

68 W

76

42

-91

-63

44 N

40

56 W

60 W

64 W

22

38

1 -106

-80

-100

68 W

20

0 -40

-8

-14

40

40

44 N

10

56 W

52 W

48 W

72 W

68 W

Fig. 5. Isobase maps for 13–10 kyr.

64 W

60 W

56 W

52 W

48 W

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1868

Kranck (1972) and two radiocarbon dates showing marine overlap in western Prince Edward Island at 12.4 and 12.7 14C kyr BP (Prest, 1973). Because this is a total of only three dates, there is some uncertainty about the lowstand depth, here placed at 31 m. 4.6. Quebec Relative sea-level curves are mostly either type A or modified types A and B with transgressions and regressions peculiar to the region (see Dyke and Peltier, 2000). The modified type A curve at Tadoussac shows rsl falling until 6 14C kyr BP then rising until 2 14 C kyr BP, before falling again. At Matane (63), the curve is actually a modified type B: rsl drops below modern sea level ca. 7 14C kyr BP, then rises to peak above modern level at ca. 5 14C kyr BP, before falling again. Curve 89 (Baie des Chaleurs) is based on data published by Bail (1983) and Gray (1987). Shell and wood dates indicate rsl fell below modern level just

52 N

9 kyr 40 0

28

19

46

80

102

48 N

20

49

Dates on freshwater and salt-marsh peats constrain the rsl history of Sable Island only as far back as only

90

29

15

-4

-45

-15

7 -5

-16

-22 -32

-16.5

31

-23 -28

-46

-33

-33

8

-60

-67

-48

-27 -27

-40

-19

-18

-59

-30

44 N

-39

-30

-40

-44

-16 -17

-14

72 W

80 0 4 32

39

72 W

52 N

6 kyr

4 -5

8

-15

-15

-14 -18

-8

-10

-11 -10 -11 -26

-37

-29

-20

-26

44 N

56 W

52 W

48 W

72 W

-15 -21

-13 -9 -9 -11 -12

60 W

-25

-20 -23 -19

-22

-12 -14

64 W

-15

-21 0

-30

-14

68 W

-3

-8

-28

-27

2 -11

8

-8

2,0

5

8 7

0

-7

1

48 N

-16

12

17 9

11

25

-17

18

20

12

48 W

8

40

13

52 W

56 W

60 W

64 W

68 W

11

0

0

2

48 W

12 20

27 12

12

29

52 W

56 W

60 W

64 W

68 W

7 kyr

72 W

18

22

13, 14

44 N

20

0

19

-31

48 N

40

10

15

48 N

-28

-24

52 N

29

11 102

62

44 N

80

80

14

34

-16

-25

48

19

8 kyr

33

19 148

4.7. Outer shelf

52 N

25 40 124

before 10 14C kyr BP. Bail (1983) speculated that rsl fell to 10 m in the early Holocene, but Syvitski (1992) argued that it dropped to 90 m. This was based, in part, on the presence of fluvial channels incised into glaciomarine sediments to this depth. However, a multibeam bathymetry survey in 1998 reveals that the channels are not fluvial, but are parallel flutes oriented along the axis of the bay and have probably formed as a result of erosion by tidal currents soon after deposition. Farther towards the head of the bay, multibeam data reveal that a submarine moraine appears to have a beveled surface at about 45 m (see also Syvitski, 1992), with primary glacial morphology visible below this depth. This depth is adopted as the best available evidence of the postglacial sea-level lowstand in the area.

-20 68 W

Fig. 6. Isobase maps for 9–6 kyr.

64 W

60 W

56 W

52 W

48 W

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

ca. 8.1 14C kyr BP (Scott et al., 1984, 1989), when rsl was about 35.4 m. The lack of sufficient data on the outer shelf presents a problem that we circumvented by using predictions of the ICE-4G geodynamic model supplied courtesy of W.R. Peltier. The ICE-4G predicted curve for Sable Island is a type-D, with rsl at 100 m at 13 14 C kyr BP, rising steeply in the early Holocene, and lesssteeply thereafter. The ICE-4G predicted curve for Grand Bank is similar to that at Sable Island, with rsl starting at 106 m at 13 14C kyr BP. There are no curves based on empirical data here, but Lewis et al. (1995) presented a compilation of radiocarbon dates for Grand Bank, and argued that the rsl lowstand was B 100 m ca. 18 14C kyr BP, and that the lower bound of the lowstand was 125 m.

5. Isobase maps Isobase maps for the periods 13–10 14C kyr BP are shown in Fig. 5, and for 9–6 14C kyr BP in Fig. 6. At 13 14 C kyr BP a ridge of high values extends over Newfoundland, separated from a similar ridge over the

1869

Maritime Provinces by a trough of low rsl values that extends up the Gulf of St. Lawrence. These features are much more extreme than in previously published isobase maps (Andrews, 1989; Dyke, 1996). This pattern is broadly similar to that of the marine limit (Grant, 1989; see also early maps shown in modified form by Andrews (1989). The pattern is persistent, with the zero isobase moving northwards and towards the interiors of land areas (e.g. island of Newfoundland) and the range of rsl values diminishing. (At 13 kyr rsl ranges from 100 to +140 m; at 8 kyr it ranges from 40 to +100 m.) By 11 14C kyr BP, the area below modern sea level has expanded greatly in the Gulf of St. Lawrence, and the gradient of isobases is relatively steep over the inner St. Lawrence Estuary and New England (see Thompson et al., 1998 for discussion of emerged glaciomarine deltas and steep isobase gradients). By 9 14C kyr BP the New England gradient has lessened, but that over the St. Lawrence Estuary remains steep. At 8, 7 and 6 14 C kyr BP, gradients everywhere are much lessened, with the steepest gradients still along the north shore of the St. Lawrence Estuary.

Fig. 7. 13 kyr palaeogeography, also showing ice margins adapted from Dyke and Prest (1987).

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1870

6. Palaeogeography 6.1. 13

14

C kyr BP palaeogeography

Because of low relative sea level, parts of the offshore banks are emergent, forming islands, the largest of which occupies Grand Bank (Fig. 7). On the Scotian Shelf there is a cluster of islands at Sable Island Bank, Banquereau, Middle Bank, Emerald Bank, and Canso Bank. Georges Bank is an island, and there are some smaller islands between there and the mainland. In New England and New Brunswick there is significant submergence of low-lying coastal regions, forming embayments that penetrate far inland along modern river valleys (e.g., Saint John River). In the Gulf of St. Lawrence, a large emerged area surrounds the Magdalen Islands. In Newfoundland, submergence is observed on low-lying parts of the Burin Peninsula. The position of the 13 kyr ice margin (Dyke and Prest, 1987) shows that some ice covered areas were below sea level, particularly northern and northeastern Newfoundland and the North Shore of the Gulf of St. Lawrence. The ice margin was in contact with the ocean

in the embayments of New England and New Brunswick. However, alternate ice scenarios (Stea, 2000) show much more ice in Nova Scotia at 13 kyr in the Chignecto Phase (13.2–12.5 kyr). It is unknown, therefore, whether or not the narrow isthmus linking Nova Scotia to the remainder of the continent was actually flooded. 6.2. 12

14

C kyr BP palaeogeography

The island of Grand Bank has shrunk; across the Cabot Strait, Canso Bank has submerged (Fig. 8). On the other hand, there is increased emergence in southwest mainland Nova Scotia, and just offshore, Browns Bank is emergent. Farther southwest, the emergent George’s Bank is separated from the mainland by a narrow channel in the area of the modern Great South Channel. Inundation of New England and New Brunswick is reduced compared with 13 kyr, and Nova Scotia is now connected to the mainland. The emerged area around the Magdalen islands has shrunk. In Newfoundland, the tip of the Great Northern Peninsula remains submerged. In this area, glacial ice

Fig. 8. 12 kyr palaeogeography.

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

has retreated to the south by this time, and is probably grounded in shallow water (Dyke and Prest, 1987). On the other hand, ice still covers most of the ‘‘inundated’’ zone of the North Shore of the Gulf, and the St. Lawrence Estuary. 6.3. 11

14

C kyr BP palaeogeography

The island chain on the outer shelf remains, except for Emerald Bank, now submerged (Fig. 9). Most islands are smaller, in particular, Grand Bank. Browns Bank, however, is larger than at 12 kyr, while the emerged area in southwest Nova Scotia has extended farther southwards. Georges Bank is now a peninsula. Prince Edward Island is slightly larger than at 12 kyr, and the emerged area around the Magdalen Islands is much larger. There is still submergence in northern Great Northern Peninsula (note the large island on the north coast of modern Hare Bay), North Shore of the Gulf of St. Lawrence (still partly ice-covered), and the St. Lawrence Estuary. (The extent of ice at this time is problematic. Whereas Dyke and Prest (1987)

1871

depict small ice caps in the interior of Nova Scotia, Stea (2000) shows extensive ice off eastern Prince Edward Island.) 6.4. 10

14

C kyr BP palaeogeography

Browns Bank is submerged and Georges Bank is an island once more, separated from the adjacent peninsula by nearly 100 km of open water (Fig. 10). Banquereau has broken into several parts, and Grand Bank has shrunk in extent. Part of Northumberland Strait is dry land, so that Prince Edward Island is connected to the mainland. The extent of submergence in northern areas is further reduced. On the Great Northern Peninsula of Newfoundland a large island remains on the north side of modern Hare Bay 6.5. 9

14

C kyr BP palaeogeography

Grand Bank is smaller than at 10 kyr (Fig. 11). Small islands have emerged on St. Pierre Bank. The islands in the Sable Island area are smaller in extent, or have

Fig. 9. 11 kyr palaeogeography.

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1872

Fig. 10. 10 kyr palaeogeography.

broken into several parts due to submergence. Georges Bank is similarly reduced in extent. The emergent areas around Prince Edward Island, the Magdalen Islands, and Cape Breton Island have reached their greatest extent. A wide peninsula extends northeast into the Gulf from western Prince Edward Island, and a similar peninsula extends from northeastern New Brunswick. In Newfoundland we see the small areas of emergence in the southwestFSt. George’s Bay and Port au Port Bay. The north of the Great Northern Peninsula remains submerged except for the large island north of modern Hare Bay. The coastal fringe of the mainland (south Labrador and south Quebec) is also submerged.

point of disappearing (Fig. 12). Similarly, only small parts of Banquereau and Middle Bank remain above water (although there are large sandy bedforms in these areas, so they may have been submerged by this date). On the other hand, in the southern Gulf of St. Lawrence, Northumberland Strait remains emergent, with large lakes in places, and an emerged fringe still surrounds the Magdalen Islands. The submerged coastal fringe in the northern Gulf of St. Lawrence, St. Lawrence Estuary, and north Newfoundland continues to contract due to rebound. On the Great Northern Peninsula, the former large island north of Hare Bay is now joined to the peninsula. 6.7. 6

6.6. 8

14

C kyr BP palaeogeography

Continued submergence on the outer shelf has greatly diminished the size of the formerly large islands at Georges Bank and Grand BankFthe latter is on the

14

C kyr BP palaeogeography

By this time (Fig. 13), the geography of the region is very close to the modern situation. Northumberland Strait, separating Prince Edward Island from the mainland, is now open. Areas of submergence in the north are now very restricted.

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1873

Fig. 11. 9 kyr palaeogeography.

7. Discussion 7.1. Isobases and deglaciation As Josenhans and Lehman (1999) showed, the calving embayment proposed by Thomas (1977) migrated rapidly into the Gulf of St. Lawrence after 14 kyr, and reached Anticosti Island by 13.7 kyr. By 11.4–11.6 kyr (Rodrigues, 1992) the marine incursion reached the St. Lawrence Lowlands, forming the Champlain Sea (Gadd, 1988). Similarly, an embayment may have developed in the Gulf of Maine/Bay of Fundy, for ice that had formerly extended seaward (Fader et al., 1977) had reached the coast of New England by 14 kyr; southern Maine was rapidly deglaciated between 14 and 13 kyr, forming the now emerged glaciomarine deltas of the region (Thompson et al., 1998). The rapid removal of ice in the Gulf and on the Atlantic shelves isolated ice caps in the Martitime Provinces and Newfoundland. For example, the ice margin stabilized at fiord mouths along the south coast of Newfoundland by 14 kyr, retreated to fiord heads by 12.5, and remained inland

after 10 kyr (Shaw et al., 2000a). Stea (2000) shows extensive ice in parts of the Maritime Provinces as late as the Younger Dryas period. The pattern observed in the isobases reflects several factors. The first is the relatively enhanced crustal loading by glacier ice in areas that are now land (Newfoundland, the Maritime Provinces, and the Quebec/Labrador mainland), exceeding the effective loading in the Gulf of St. Lawrence and the Laurentian Channel (450 m deep). The ice in the latter areas may have been at much lower elevation than the surrounding areas (and hence thinner) if occupied by ice streams (Thomas, 1977; Hughes, 1998). Secondly, the observed isobases reflect the persistence of glacier ice in Newfoundland and the Maritime Provinces for 5000 years after evacuation of ice from the Laurentian Channel. Thirdly, the strong gradient of the isobases near the North Shore of the Gulf of St. Lawrence and in southern Quebec reflects the slow decay of the Laurentide Ice Sheet in the interior of Quebec (Dyke and Prest, 1987). This demonstrates that the combined glacioisostatic, eustatic, and hydro-isostatic processes in a

1874

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

Fig. 12. 8 kyr palaeogeograph.

region with a complex deglaciation history can produce greater inter-regional variation in rsl history than was previously suspected. We suggest that the ice histories employed in global glacial-eustatic sea-level models (e.g., Peltier, 1998) reflect only longer wavelength temporal and spatial modes of the actual ice loading, and we further suggest that local variances from the ‘‘average’’ ice loading model have a significant and measurable effect on local measurements of rsl. The horizontal scales of our suggested variances in the ice loading history are large enough (wavelengths in the order of 300–1000 km) that we can expect significant amounts of induced lithospheric flexure. In addition, the spherically symmetric models (e.g. Peltier, 1998), used to explain global glacial eustasy, do not account for regional changes in lithospheric flexural strength but rather they parameterize the effect using a mean global elastic thickness. The global mean must be considered in context with the global application; obviously, such estimates are not applicable locally at mid-ocean ridges, for example. Local changes in the lithospheric strength effectively

modify the ‘‘low pass filter’’ effect of ice loading. Given that effective elastic thickness estimates derived for eustatic studies are around 100 km, the load spectrum in the 300–1000 km wavelength range is most sensitive to changes in this quantity, and we suggest this sensitivity may well be best recorded in the local pattern of rsl. The local variance of observed rsl from the predictions of the global models arises from a complex interplay between the local ice-loading history, the lithospheric thickness, astheospheric viscosity and selfgravitation, and these effects will be addressed in future work. 7.2. Sensitivity of reconstructions The palaeogeographic reconstructions evolved as we adjusted the isobase maps to take account of new or modified sea-level curves. This iterative process revealed that in many regions, palaeogeographic reconstruction is highly sensitive to positioning of isobases. For instance, at an early stage we employed the 90 m postglacial lowstand depth (Syvitski, 1992) for Baie des

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

1875

Fig. 13. 6 kyr palaeogeography.

Chaleurs. When applied to the DEM, the resulting isobase pattern resulted in subaerial exposure of most of the Magdalen Plateau at 9 kyr. Even very small changes in isobase patterns result in large variations in palaeogeography on the shallow, flat banks on the outer shelf. We found, for example, that small changes in isobase positions on the western Newfoundland Shelf produced a large island on St. Pierre Bank at 10–9 kyr. 7.3. Comparison with previous palaeogeographic maps To what extent do our reconstructions differ from those previously published? The extent of postglacial submergence closely corresponds with that depicted by Grant (1989), particularly in the largest areas of submergence: New England/New Brunswick, northern Newfoundland, North Shore of the Gulf of St. Lawrence. However, on the continental shelf our reconstructions show fewer islands than depicted by Dyke and Prest (1987). In particular, we show less emergence of LaHave Bank and St. Pierre Bank. We also find that some of the banks on the continental shelf have more complex histories than

previously thought. Georges Bank was an island, expanded to become a peninsula, then shrank again, and submerged just after 8 kyr. Browns Bank emerged for a brief period (B12–11 kyr) and then submerged again. It is interesting to note that the maximum extent of the Georges Bank Peninsula, and exposure of Browns Bank, was ca. 11 kyr. Green (1986) noted that there were two pathways for migration of Abies and Fraxinus into Nova Scotia: via the narrow isthmus separating that province from New Brunswick, and also into southwest Nova Scotia from the southwest. These taxa appear in southwest Nova Scotia at 11.9 and 11.5 kyr respectively. Green stated that ‘‘the tree migration patterns implied by first arrival times are consistent with exposed areas on Georges and Brown Banks having acted as land bridges’’ (p. 1177). Perhaps the most fascinating changes were in the southern Gulf of St. Lawrence, where Northumberland Strait was emergent for a considerable period, so that Prince Edward Island was not an island. This scenario is similar to that depicted by Kranck (1972). We find that the island became separated from the mainland before

1876

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

6 kyr, whereas Dyke and Prest (1987) show it still connected at 5 kyr. We do not find that the Magdalen Islands were connected to the mainland at 13 kyr, as shown by Dyke and Prest. 7.4. Future research The paucity of relative sea-level data for the Gulf of St. Lawrence and the Atlantic Canadian shelves, allied with the sensitivity of reconstructions in these areas to changes in isobase positions, dictate that future reconstructions will require improved rsl data. The collection of index points will probably continue at a slow pace, and the greatest hope for the future arguably lies with a refined version of the ICE-4G geodynamic model (Peltier, 1998) that will provide plausible sea-level curves across the region. This model at present uses LGM ice margins located at modern coasts, rather than at the shelf edge, as new data demand (Piper et al., 1998).

Acknowledgements We acknowledge Tracy Quinlan who (as a student) made the first compilation of data and drew the first isobase maps. We thank Don Forbes and Gordon Fader for constructive criticism of early drafts of the paper and John Andrews and Claude Hillaire-Marcel for critically reviewing the paper. This is Geological Survey of Canada Contribution 2000300.

References Amos, C.L., Nadeau, O.C., 1988. Surficial sediments of the outer banks, Scotian Shelf, Canada. Canadian Journal of Earth Sciences 25, 1923–1944. Amos, C.L., Zaitlin, B.A., 1985. The effect of changes in tidal range on a sublittoral macrotidal sequence, Bay of Fundy, Canada. GeoMarine Letters 4, 161–169. Andrews, J.T. 1989. Postglacial emergence and submergence. In: Fulton, R.J. (Ed.), Chapter 8 of Quaternary Geology of Canada and Greenland; Geological Survey of Canada, Geology of Canada, no. 1 (also Geological Society of America, The Geology of North America, v. K-1). Bail, P., 1983. Probl"emes g!eomorphologiques de l’englacement et de la transgression marine pl!eistoc"enes en Gasp!esie sud-orientale. Unpublished D. Phil. Thesis, Department of Geography, McGill University, Montreal. Bard, E., Arnold, M., Mangerud, J., Paterne, M., Labeyrie, L., Duprat, J., Melieres, M.-A., Snstegaard, E., Duplessy, J.-C., 1994. The North Atlantic atmosphere-sea surface 14C gradient during the Younger Dryas climatic event. Earth and Planetary Science Letters 126, 275–287. Barnhardt, W.A., Gehrels, W.R., Belknap, D.F., Kelley, J.T., 1995. Late Quaternary relative sea-level change in the western Gulf of Maine: evidence for a migrating glacial forebulge. Geology 23, 317–320. Bell, T.,Renouf, M.A.P., 1996. Integrating archaeology and sea level history at Port aux Choix, northwestern Newfoundland. Proceed-

ings, Workshop on Assessing the State of the Environment of Gros Morne National Park, Rocky Harbour, November 1996. Bigras, P.,Dubois, J.M.M., 1987. R!epertoire comment!e des datations 14 C du nord de l’estuaire et du golfe du Saint-Laurent, Qu!ebec et Labrador. Research Bulletin Department of Geography, University of Sherbrooke, 92–95–96, 166pp. Bousefield, E.L., Thomas, M.L.H., 1975. Postglacial distribution of littoral marine invertebrates in the Canadian Atlantic region. In: Ogden III, J.G., Harvey, M.J. (Eds.), Environmental Change in the Maritimes. Nova Scotian Institute of Science, Halifax, pp. 47–60. Brookes, I.A., 1969. Late-glacial marine overlap in western Newfoundland. Canadian Journal of Earth Sciences 6, 1397–1404. Brookes, I.A., Scott, D.B., McAndrews, J.H., 1985. Postglacial relative sea-level change, Port au Port area, west Newfoundland. Canadian Journal of Earth Sciences 22, 1039–1047. Clark, P.U., Fitzhugh, W.W., 1992. Postglacial relative sea level history of the Labrador coast and interpretation of the archaeological record. In: Johnson, L.L., Stright, M. (Eds.), Palaeoshorelines and Prehistory: An Investigation of Method. CRC Press, Boca Raton, USA, 243pp. de Vernal, A., Jett!e, H., 1987. Analyses palynologiques de s!ediments holoc"enes du lac Bras d’Or (carotte 86-036-016P), #ısle du CapBreton, Nouvelle-Ecosse, Geological Survey of Canada, Paper 87-1A, 11–15. de Vernal, A., Lortie, G., Larouche, A., Richard, P., et Scott, D.B., 1985. Evolution du milieu littoral et remont!ee du niveau relatif de la mer a" l’Holoc"ene sup!erieur dans la region de l’!etang McDougall (#ısle du Cap-Breton, Nouvelle-Ecosse). Canadian Journal of Earth Sciences 22, 315–323. Dionne, J.-C., 1988. Holocene relative sea-level fluctuations in the St. Lawrence estuary, Qu!ebec, Canada. Quaternary Research 29, 233–244. Dionne, J.-C., 1990. Observations sur le niveau marin relatif a" l’Holoc"ene, a" Rivi"ere-du-Loup, estuaire du Saint-Laurent, Qu!ebec. G!eographie Physique et Quaternaire 49, 363–380. Dionne, J.-C., Coll, D., 1995. Le niveau marin relatif dans la r!egion de Matane (Qu!ebec) de la d!eglaciation a" nos jours. G!eographie physique et Quaternaire 44, 43–54. Dionne, J.-C., Ochietti, S., 1996. Aperc-u du Quaternaire a" l’embouchure du Saguenay, Quebec. G!eographie physique et Quaternaire 50, 5–34. Dyke, A.S., 1996. Preliminary palaeogeographic maps of glaciated North America. Geological Survey of Canada, Open File 3296. Dyke, A.S., Peltier, W.R., 2000. Forms, response times and variability of relative sea-level curves, glaciated North America. Geomorphology 32, 315–333. Dyke, A.S., Prest, V.K., 1987. Late Wisconsinan and Holocene retreat of the Laurentide Ice Sheet. Geological Survey of Canada, Map 1702A, scale 1:5 000 000. Edgecombe, R.B., Scott, D.B., Fader, G.B., 1999. New data from Halifax Harbour: Palaeoenvironment and a new Holocene sea-level curve for the inner Scotian Shelf. Canadian Journal of Earth Sciences 36, 805–817. Emery, K.O., Uchupi, E., 1972. Western North Atlantic Ocean: Topography, rocks, structure, water, life, and sediments. American Association of Petroleum Geologists, Tulsa, Oaklahoma, USA. 532pp. Fader, G.B.J., 1989. A late Pleistocene low sea-level stand of the southeast Canadian offshore. In: Scott, D.B., Pirazolli, P.A., Honig, C.A. (Eds.), Late Quaternary Sea-Level Correlation and Applications. Kluwer Academic Publishers, Dordrecht, pp. 71–103. Fader, G.B.J., King, L.H., MacLean, B., 1977. Surficial geology of the eastern Gulf of Maine and Bay of Fundy. Geological Survey of Canada Paper 76–17, 23pp. & map. Fader, G.B.J., King, L.H., Josenhans, H.W., 1982. Surficial geology of the Laurentian Channel and the western Grand Banks of

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878 Newfoundland. Marine Sciences Paper 21, Geological Survey of Canada Paper 81-22. Department of Energy, Mines and Resources, Ottawa. 37p and map. Forbes, D.L., Boyd, R., Shaw, J., 1991. Late Quaternary sedimentation and sea level changes on the inner Scotian Shelf. Continental Shelf Research 11, 1155–1179. Forbes, D.L., Shaw, J., Eddy, B.G., 1993. Late-Quaternary sedimentation and the postglacial sea-level minimum in Port au Port Bay and vicinity, west Newfoundland. Atlantic Geology 29, 1–26. Gadd, N.R. (Ed.), 1988. The late Quaternary development of the Champlain Sea Basin. Geological Association of Canada Special Paper 25, 312pp. Gehrels, W.R., Belknap, D.F., Kelley, J.T., 1996. Integrated highprecision analyses of Holocene relative sea-level changes along the coast of Maine. Geological Society of America Bulletin 108, 1073–1088. Grant, D.R., 1970. Recent coastal submergence of the Maritime Provinces, Canada. Canadian Journal of Earth Sciences 7, 676–689. Grant, D.R., 1975. Recent coastal submergence of the Maritime Provinces; Nova Scotian Institute of Science, Proceedings, Vol. 27, Supplement 3, pp. 83–102. Grant, D.R., 1989. Quaternary geology of the Atlantic Appalachian region of Canada. In: R.J. Fulton (Ed.), Quaternary Geology of Canada and Greenland. Vol. 1, Geological Survey of Canada, Geology of Canada, pp. 393–440. Grant, D.R., 1994. Quaternary Geology of Port Saunders Map Area, Newfoundland. Geological Survey of Canada Paper 91–20, 59pp. Grant, A.C., McAlpine, K.D., 1990. The continental margin around Newfoundland. In: M.J. Keen, G.L. Williams, (Eds.), Geology of the Continental Margin of Eastern Canada, Vol. 2. Geological Survey of Canada, Geology of Canada, pp. 239–292 (also Geological Society of America, the Geology of North America, Vol. I-1). Gray, J.T., 1987. Quaternary processes and palaeoenvironments in the Gaspe Peninsula and the lower St. Lawrence Valley. Field Excursion C-4, XIIth INQUA Congress, Ottawa. National Research Council of Canada, Ottawa. 84pp. Green, D.G., 1986. Pollen evidence for the postglacial origin of Nova Scotia’s forests. Canadian Journal of Botany 65, 1163–1179. Hillaire-Marcel, C., 1979. Les mers postglaciares du Qu!ebec: quelques aspects. Th"ese Universit!e de Paris VI, Vol. 1, 293pp; Vol. 2, 241 fig. and 26 pl. Hughes, T.J., 1998. Ice Sheets. Oxford University Press, New York, 343pp. Josenhans, H., Lehman, S., 1999. Quaternary stratigraphy and glacial history of the Gulf of St. Lawrence, Canada. Canadian Journal of Earth Sciences 36, 1327–1345. Kaye, C.A., Barghoorn, E.S., 1964. Late Quaternary sea-level change and crustal rise at Boston, Massachusets, with notes on the autocompaction of peat. Geological Society of America Bulletin 75, 63–80. Keene, H.W., 1971. Postglacial emergence and salt marsh evolution in New Hampshire. Maritime Sediments 7, 64–68. King, L.H., Fader, G.B.J., 1986. Wisconsinan glaciation of the Atlantic continental shelf of southeast Canada. Geological Survey of Canada, Bulletin 363. 72pp. Kranck, K., 1972. Geomorphological development and post-Pleistocene sea level changes, Northumberland Strait, Maritime Provinces. Canadian Journal of Earth Sciences 9, 835–844. Lewis, C.F.M, Macpherson, J.B., Scott, D.B., 1987. Early sea level transgression, eastern Newfoundland. INQUA 87 Programme with abstracts, Ottawa, July 31–August 9, 1987, p. 210. Lewis, C.F.M., Sonnichsen, G.V., Simms, A.E., Chouinard, L.E., 1995. The seafloor iceberg scour record off Newfoundland,

1877

Canada: responses to glacial and palaeo-oceanographic change. Poster, Fifth International Oceanographic Conference, Halifax, 10–14th October 1995. Loring, D.H., Nota, D.J.G. 1973. Morphology and Sediments of the Gulf of St. Lawrence. Bulletin 182, Fisheries Research Board of Canada, Ottawa. 147pp and maps. Newman, W.S., Fairbridge, R.W., March, S., 1971. Marginal subsidence of glaciated areas: United States, Baltic and North Seas. In: Ters M. (Ed.), Etude sur le Quaternaire dans le Monde, VIII1 Congress INQUA Paris, 1969, pp. 795–801. Palmer, A.J.M., 1974. Diatom stratigraphy and post-glacial history of Basin Head Harbour, Prince Edward Island. Unpublished M.Sc. Thesis, Dalhousie University, Halifax, 143pp. Pirazolli, P.A., 1991. World Atlas of Holocene sea-level changes. Elsevier Oceanography Series, Amsterdam, 300pp. Peltier, W.R., 1998. Postglacial variations in the level of the sea: implications for climate dynamics and solid earth geophysics. Reviews of Geophysics 36, 603–690. Piper, D.J.W., Shaw, J., Fader, G.B.J., Josenhans, H.W., Sherin, A.G., 1998. Late Wisconsinan ice extent and retreat from Atlantic Canada. Abstract, Meeting of the Geological Society of America, Toronto, October 1998. Prest, V.K., 1973. Surficial deposits, Prince Edward Island; Geological Survey of Canada, Map 1366A, Scale 1: 126,720. Quinlan, G., Beaumont, C., 1981. A comparison of observed and theoretical postglacial relative sea level in Atlantic Canada. Canadian Journal of Earth Sciences 18, 1146–1163. Redfield, A.C., Rubin, M., 1962. The age of salt marsh peat and its relation to recent changes in sea level at Barnstable, Massachusets. Proceedings of the National Academy of Science 48, 1728–1735. Renouf, M.A.P., Bell, T., 1998. Searching for the Maritime Archaic Indian habitation site at Port aux Choix, Newfoundland: an integrated approach using archaeology, geomorphology and sea level history. Report of the 1997 field season at Port aux Choix, northwestern Newfoundland. Unpublished report, Government of Newfoundland and Labrador, Department of Tourism, Culture and Recreation, Culture and Heritage Division, 19pp. Rodrigues, C.G., 1992. Successions of invertebrate microfossils and the late Quaternary deglaciation of the central St. Lawrence Lowland, Canada and United States. Quaternary Science Reviews 11, 503–534. Scott, D.B., Greenberg, D.A., 1983. Relative sea-level rise and tidal development in the Fundy tidal system. Canadian Journal of Earth Sciences 20, 1554–1564. Scott, D.B., Medioli, F.S., 1980. Post-glacial emergence curves in the Maritimes determined from marine sediments in raised basins. In: Proceedings, Canadian Coastal Conference 1980 (Burlington, Ontario). Associate Committee for Research on Shoreline Erosion and Sedimentation, National Research Council of Canada, pp. 428–446. Scott, D.B., Medioli, F.S., 1982. Micropalaeontological documentation for early Holocene fall of relative sea level on the Atlantic coast of Nova Scotia. Geology 10, 278–281. Scott, D.B., Williamson, M.A., Medioli, C.F., 1981. Marsh foraminifera of Prince Edward Island: their recent distribution and application for former sea-level studies. Maritime Sediments and Atlantic Geology 17, 98–129. Scott, D.B., Medioli, F.S., Duffett, T.E., 1984. Holocene rise of relative sea level at Sable Island, Nova Scotia, Canada. Geology 12, 173–176. Scott, D.B., Boyd, R., Medioli, F.S., 1987. Relative sea-level changes in Atlantic Canada: observed level and sedimentological changes vs. theoretical models. Special Publication 41, the Society of Economic Palaeontologists and Mineralogists, pp. 87–96. Scott, D.B., Boyd, R., Douma, M., Medioli, F.S., Yuill, S., Leavitt, E., Lewis, C.F.M., 1989. Holocene relative sea-level changes and

1878

J. Shaw et al. / Quaternary Science Reviews 21 (2002) 1861–1878

Quaternary glacial events on a continental shelf edge: sable island bank. In: Scott, D.B., Pirazolli, P.A., Honig, C.A. (Eds.), Late Quaternary Sea-Level Correlation and Applications. Kluwer Academic Publishers, Dordrecht, pp. 105–119. Scott, D.B., Brown, K., Medioli, F.S., 1995. A new sea-level curve from Nova Scotia: evidence for a rapid acceleration of sea-level rise in the late mid-Holocene. Canadian Journal of Earth Sciences 32, 2071–2081. Shaw, J., Ceman, J., 1999. Salt-marsh aggradation in response to late Holocene sea level rise at Amherst Point, Nova Scotia. The Holocene 9, 439–451. Shaw, J., Edwardson, K.A., 1994. Surficial sediments and post-glacial relative sea-level history, Hamilton Sound, Newfoundland. Atlantic Geology 30, 97–112. Shaw, J., Forbes, D.L., 1990. Relative sea-level change and coastal response, northeast Newfoundland. Journal of Coastal Research 6, 641–660. Shaw, J., Forbes, D.L., 1992. Barriers, barrier platforms, and spillover deposits in St. George’s Bay, Newfoundland: paraglacial sedimentation on the flanks of a deep coastal basin. Marine Geology 105, 119–140. Shaw, J., Forbes, D.L., 1995. The postglacial relative sea-level lowstand in Newfoundland. Canadian Journal of Earth Sciences 32, 1308–1330. Shaw, J., Taylor, R.B., Forbes, D.L., 1993. Impact of the Holocene transgression on the Atlantic coastline of Nova Scotia. G!eographie physique et Quaternaire 47, 221–238. Shaw, J., Forbes, D.L., Edwardson, K.A., 1999. Surficial sediments and placer gold on the inner shelf and coast of northeast Newfoundland. Geological Survey of Canada Bulletin 532, 104pp. Shaw, J., Grant, D.R., Guilbault, J.-P., Anderson, T.W., Parrott, D.R., 2000a. Submarine and onshore end moraines in southern Newfoundland: implications for the history of late Wisconsinan ice retreat. Boreas 29, 295–314.

Shaw, J., Taylor, R.B., Li., M., Frobel, D., 2000b. Role of a submarine bank in the long-term evolution of the coast of Prince Edward Island, Canada: new evidence from multibeam bathymetry mapping systems. Periodicum Biologorum, Croatian Society of Natural Sciences, Vol. 102, Supplement 1, pp. 589–594. Stea, R.R., 2000. Virtual Field Trip web site, Nova Scotia Natural Resources, Mines and Energy Branch: http://www.gov.ns.ca/ NATR/MEB/field/vista.htm#vista Stea, R.R., Boyd, R., Fader, G.B.J., Courtney, R.C., Scott, D.B., Pecore, S.S., 1994. Morphology and seismic stratigraphy of the inner continental shelf off Nova Scotia, Canada: evidence for a 65 m lowstand between 11,650 and 11,250 C14 yr B.P. Marine Geology 117, 135–154. Stuiver, M., Reimer, P.J., Bard, E., Beck, J.W., Burr, G.S., Hughen, K.A., Kromer, B., McCormac, G., van der Plicht, J., Spurk, M., 1998. INTCAL98 radiocarbon age calibration, 24,000-0 cal BP. Radiocarbon 40, 1041–1083. Syvitski, J.P.M., 1992. Marine Geology of Baie des Chaleurs. G!eographie physique et Quaternaire 46, 331–348. Thomas, R.H., 1977. Calving bay dynamics and ice sheet retreat up the St. Lawrence valley system. G!eographie physique et Quaternaire 31, 347–356. Thomas, M.L.H., Grant, D.R., de Grace, M., 1973. A late Pleistocene marine shell deposit at Shippegan, New Brunswick. Canadian Journal of Earth Sciences 10, 1329–1332. Thompson, W.B., Crossen, K.J., Borns, H.W. Jr., andAndersen, B.G., 1998. Glaciomarine deltas of Maine and their relation to Late Pleistocene-Holocene crustal movements. In: Anderson, W.A., Borns, H.W. Jr. (Eds.), Neotectonics of Maine: Studies in seismicity, crustal warping, and sea-level change, Bulletin 40, Department of Conservation, Maine Geological Survey, pp. 43–67, 228pp. van de Plassche, O., Mook, W.G., Bloom, A.L., 1989. Submergence of coastal Connecticut 6000-3000 (14C) years B.P. Marine Geology 86, 349–354.