pollen distribution in the northeast pacific ocean

QUATERNARY RESEARCH 7, 45-62 (1977)

Pollen Distribution in the Northeast Pacific Ocean

LINDA HEUSSER

Department of Biology, New York University, Box 608, Tuxedo, New York 10987

AND

WILLIAM L. BALSAM

Division of Natural Sciences, Southampton College of Long Island University, Southampton, New York 11968

Received January 26, 1976

Distributional patterns of palynomorphs in core tops from the continental margin of the northeast Pacific Ocean (30°-60’N lat 118°-1500W long) reflect the effects of fluvial and marine sedimentation as well as the distribution of terrestrial vegetation. Maximum pollen concentration ( grains/cm3 of marine sediment) occurs off the mouth of the Columbia River and off San Francisco Bay (the outlet of the San Joaquin and Sacramento Rivers) and appears to be coincident with areas of high terrigenous lutite deposition. The abundance of pollen and spores in shelf sediments is extremely variable with high concentrations typical only of the finest sediments. On the slope, rise and abyssal plain, pollen concentration shows a general decrease with distance from shore. This suggests that in the northeast Pacific pollen is transported into the marine environment primarily by rivers and that, in terms of sedimentation, pollen may be regarded as part of the organic component of fine-grained lutum.

Pinus, the principal pollen component of marine sediment on the northeast Pacific margin, is concentrated adjacent to the major drainage systems of areas in which pine grows. Tsuga heterophylla, Picea, and Alnus, important components of the temperate conifer forest, are concentrated off the area of their optimal development, western Washington. Quercus, Sequoia, and Compositae concentrations are greater off the southern California coast where they are prominent in the vegetation. The relative (percent) abundance of most of these pollen taxa in marine sediments reflects a positive relationship to their distribution on land. Picea an,d Alzus are relatively more important north of 45’N, Tsuga heterophylla between 45 -50 N, and Quercus, Sequoia, and Compositae south of 40 N. Pine percentages increase seaward, from less than 10% of the pollen sum in shelf sediments to over 50% in sediments on the abyssal plain. This seems to indicate selective transport of pine pollen. Factor analysis of pollen data from the 61 core tops results in four pollen assemblages. Three of these assemblages (Quercus-Compositae-Sequoia, Tsuga heterophylla-Pinus, and Alnus-Picea) reflect the distribution of vegetation on the adjacent continent, one (Pinus) reflects primarily the effects of marine sedimentation.

INTRODUCTION

The potential stratigraphic and ecologic significance of terrestrial microfossils in modern ocean sediments was recognized when pollen and spores were first described from marine cores and from coastal waters and sediments. This potential has yet to be realized due to the limited amount of meaningful data avail-

able. Several comprehensive studies have been published on the distribution of marine pollen in shelf sediments (Mulier, 1959; Traverse and Ginsburg, 1966; Davey, 1971), and on the distribution of pollen in relatively restricted marine waters such as the Sea of Okhotsk (Koroneva, 19573, and the Gulf of Cali- fornia (Cross et al., 1966). However,

Copynght 0 1977 by the Univerrity of Washington 411 rights of reproduction m any form reerved.

little information exists about the distri- northern branch flows parallel to the bution of pollen in surface sediments of coast and is called the Alaska Current, major oceans. while the southern branch which also

Preliminary studies of sediments of the flows parallel to the coast is called the Washington-Oregon slope (Florer, 1973; California Current (Fig. 1). Seasonal Heusser and Florer, 1973) indicated that changes in the circulation of shelf and pollen could be obtained in large enough subsurface currents off Oregon and Cali- quantities (between 200-500 grains/ fornia are related to yearly cyclic changes sample) to provide reliable estimates. in the North Pacific High and Aleutian This paper contains a qualitative and Low. Sea surface temperature and quantitative analysis of pollen from salinity gradients generally parallel the marine sediments on the margin of the coast, as do air temperature and pressure northeast Pacific Ocean and represents gradients on shore. The latter reflect the the first step in our long range program interaction of the prevailing westerlies to explore the potentials of marine with the northwest-southeast striking palynology. western cordillera, which rises to 5500 m

SETTING in Alaska.

Our study area (Fig. l), the continental Much of the warm, temperate north-

margin of the northeast Pacific Ocean, west Pacific coast is covered by conifer

may be divided into several physiographic forest with stands of Pseudotsuga men-

provinces. The continental margin off ziesii, Tsuga heterophylla, Chamaecyparis noo tka tensis and Picea sitchensis which

California is composed of a relatively narrow shelf incised by submarine canyons

reaches optimal development in north- western and

which traverse the slope and lead to dis- Washington (Franklin

crete marginal basins bordered by crests Dyrness, 1973). Sequoia sempervirens becomes a distinctive member of the

of the midocean ridge system (Fig. 1). Pacific Coastal Forest in northern Cali- Off Washington and Oregon continental slope topography is characterized by

fornia, while P. sitchensis and T. hetero-

north-northwest trending ridges and in- phylla become more prominent in northern British Columbia and Alaska.

tervening troughs. A structural trench, Southeastern Alaska is characterized by the Washington-Oregon Trench, trends northward along the base of the conti-

extensive muskeg development. Cali- fornia coastal vegetation is primarily

nental margin and is probably a continu- ation of a similar trench off British

Sage Scrub, chaparral, and Mediterranean woodland in which herbs and shrubs

Columbia and southeast Alaska (Kulm such as composites (characteristic genera and Fowler, 1974). The shelf broadens are Artemesia and Baccharis) and oaks off Washington and British Columbia and is comparatively wide along the Alaskan

are important (Heusser, 1960; Munz, 1974; Officials of NOAA, 1974). Conif-

coast. The continental slope off Alaska erous forests in southern California are is narrow and dips steeply to the Alaska restricted to higher altitudes. Trench in the north and to a broad rise in the east (McManus, 1967). Seaward SAMPLE LOCATIONS AND

of the trench, an outer ridge borders the PREPARATION PROCEDURES

Alaska Abyssal Plain. Four criteria were used in selecting the Surface circulation is dominated by 61 core-top locations.

the eastward flowing Westwind Drift (1) Cores (Fig. 1) were selected pri- which splits about 500 km west of the marily from the continental slope and continent near 45”N lat (Fig. 1). The rise, areas presumed to have high concen-

46 HEUSSER AND BALSAM

POLLEN DISTRIBUTION 47

45”

35”N

145” w 140” 135”

40”

CALIFORNIA

CURRENT

FIG. 1. Physiographic map showing the distribution of the coretops in the northeast Pacific Ocean. The numbers (1-61) correspond to core numbers listed in Table 1. The contours are in fathoms.

trations of pollen-bearing terrigenous tions should have a reasonably uniform lutites (Carlson, 1967; Duncan, 1968; geographic distribution. This criterion Griggs, 1969). had to be modified due to lack of cores

(2) Cores in which the upper few in several areas. centimeters (O-5 cm) were available were (4) Wherever possible, trigger weight chosen in order to obtain the most tops or grab samples were used in the recently deposited sediments. Pollen expectation that surface-sediment would samples from this sediment should closely be obtained. correlate with present continental vegeta- Sample preparation followed proce- tion. dures described in Balsam and Heusser

(3) The distribution of core loca- (1976). These procedures were de-


TABLE 1 Core-Top Locations and Depths. The Core Numbers Correspond

to the Numbers on Fig. 1

Core Core number name Institutiona

Latitude N

Longitude W

Depth M

1 LFGS-27 2 Y70-4-51 3 Y70-3-50 4 Y70-4-53 5 Y70-2-40 6 Y70-2-41 7 RCll-177 8 LFGS-30 9 LFGS-38

10 MUK H-32 11 MUK B-23 12 LFGS-39 13 RClO-220 14 Y70-4-61 15 Y70-4-59 16 RClO-222 17 Y70-5-63 18 Y70-5-62 19 RClO-221 20 Y70-5-65

21 Y70-5-67 22 TT-029 004 23 TT-029 003 24 TT-039 015 25 TT-039 013 26 TT-039 012 27 TT-039 011 28 RClO-225 29 TT-039 014 30 ‘M’-039 018 31 TT-039 017 32 TT-039 016 33 V20-77 34 V20-76

35 RCll-186 36 V20-75 37 RClO-226 38 TT-063 013 39 BB-326-036

40 TT-053 021 41 6705-7 42 6705-11 43 RClO-228 44 6609-28 45 RClO-229 46 6509-l-26 47 6609-7 48 6609-4 49 6609-3 50 6910-l 51 6910-2 52 6910-4

SIO osu osu osu osu osu LD SIO SIO SIO SIO SIO LD osu osu LD osu osu LD osu

osu uw uw uw uw uw uw LD uw uw uw uw LD LD LD LD LD uw uw uw osu osu LD osu LD osu osu osu osu osu osu osu

59O14’ 59Oo5’ 58’06’ 57’32’ 56O31’ 57OlO’ 57O58’ 56’58’ 54’08’ 54Oo4’ 53O50’ 53Oo5’ 51°03’ 51°09’ 50’23’ 49O57’ 50’28’ 50°30’ 50°33’ 49O49’ 48O17’ 48O44’ 48’42’ 49O12’ 49O45’ 49O23’ 49’08’ 48’45’ 48O42’ 48’26’ 48’13’ 48’11’ 47O42’ 47O54I 47O54’ 48’12’ 47’27’ 47Oo9’ 46’29’ 46O13’ 46’03’ 46OlO’ 45O56’ 45Oo5’ 45O35’ 44O39’ 43O12’ 43OOl’ 42O48’ 41°13’ 41°16’ 41°19’

142’51’ 2639 143O40’ 3650 141°39’ 3545 144O43’ 3870 143O49’ 3847 141°04’ 3384 139°00’ 2957 139O12’ 3341 136’48’ 2739 135O25’ 2620 136’20’ 3115 133’27’ 2895 133O44’ 3157 136’15’ 3575 139O15’ 3774 135O14’ 3559 132’48’ 3662 132’32’ 3164 131°37’ 2834 135’25’ 3495 132’53’ 3382 130°45’ 3325 130°03’ 2751 129O14’ 2396 128’46’ 2328 128’08’ 2341 127’46’ 2480 127’45’ 2536 128’42’ 2486 129O52’ 2765 130°01’ 2793 130°57’ 2857 128’40’ 2659 127O39’ 2628 127’12’ 2582 126’10’ 1657 127’16’ 3922 125’10’ 1657 124’42’ 658 125’23’ 1928 126’38’ 2730 127OO8’ 2753 127’00’ 2765 127’21’ 3015 126’09’ 2582 125’23’ 2861 126’41’ 2911 126’09’ 2956 125O58’ 2850 126’22’ 3072 127OOl’ 2615 128OO9’ 3130

POLLEN DISTBIBUTION 49

TABLE 1 (Continued\

Core Core Latitude Longitude Depth number name Institution’ N W M

53 FAN-BG-18 SIO 39O14’ 125OO3’ 3200 54 FAN-HMS-11G SIO 37OOl’ 125’21’ 4350 55 FAN-BG-16 SIO 37Oll’ 124’34’ 3850 56 LFGS2G SIO 36”40’ 123’16’ 3328 57 ANTP-19PG SIO 36’29’ 122O49’ 3019 58 PIF-59G SIO 36’25’ 122’48’ 2935 59 ANTP-2OPG SIO 36O26’ 123’06’ 3229 60 Y71-1-2 osu 32’12’ 120’03’ 576 61 MEN-1G SIO 32O36l 118’07’ 1920

=Core repositories are abbreviated as follows: LD = Lamont-Doherty Geological Observatory, OSU = Oregon State University, SIO = Scripps Institution of Oceanography, and UW = University of Washington.

signed to minimize the destruction of pollen grains.

RESULTS

Approximately fifty pollen taxa, rep- resentatives of the dominant vegetation of western North America, were identified. Some grains, such as T. heterophylla, could be specifically determined; however, most were classified according to genera or family. The problems of separating many pollen taxa using light microscopy, (the fifteen species of Pinus growing in the Pacific Northwest for ex- ample) are heightened in marine samples where preservation of pollen is often relatively poor and grains are frequently filled or covered with opaque material, possibly pyrite or oil. Spores present were members of the Polypodiaceae, Lycopodiaceae, Selaginellaceae, and Sphagnaceae families. Dinoflagellate cysts were more numerous than microforami- nifera (chitinous inner tests of foraminif- era), both of which were counted (Evitt, 1969). Redeposited palynomorphs, identified by stain or morphological charac- teristics, were not numerous (~3% of the total number of pollen and spores).

Distribution of the most significant marine palynomorphs is summarized by contour maps of the relative frequency and concentration of pollen and spores

from the sixty-one core tops in which more than 100 pollen grains could be identified.l Samples with less than 100 grains and shelf samples were not in- cluded as they appeared to be unreliable statistically. The variation in pollen composition between two adjacent shelf samples was often greater than in deep samples separated by 5 or 10 degrees latitude. The geographic range of plants from which pollen in the core tops may have been derived is indicated on the contour maps (except for the ubiquitous Compositae and the widely distributed Polypodiaceae).

Maximum pollen concentration (5- 10,000 grains/cm3) occurs off the mouth of the Columbia River (between 45”N and 49”N), and off the outlet of the Sacramento and San Joaquin Rivers (36”N). These high concentrations occur approximately 50-100 km offshore in depths ranging from 500-3000 m (Fig. 2). Low pollen concentration (<500 to >lOO grains) is found in all samples north of 53”N. In addition, pollen concentration is low in samples more than 250 km from shore.

Pinus, which was identified in all sam-

1 The original palynomorph data are available at the National Auxiliary Publications Service (NAPS).


FIG. 2. Maps showing distribution of the concentration (grains/cm3 marine sediment) of total pollen (upper left), Pinus (upper right), Tsuga heterophylla (lower left), and Picea (lower right). Contours are in grains x 103/cm3. Geographic extent of species from which pollen in marine sedi- merits is derived is indicated by shading.

ples, is concentrated south of 50”N (Fig. 38”-33”N. The greatest number of

2). T. heterophylla, Picea (Fig. 2), and Polypodiaceae spores (about I$ that of

Alms (Fig. 3), are localized between pollen, 1000 spores/cm3) occurs north-

44”-50”N; Sequoia, Quercus, and Com- west of the Columbia River and south-

positae (Fig. 3) are concentrated between east of San Francisco Bay (Fig. 4).


a FIG. 3. Maps showing distribution of concentration (grains/cm3 marine sediment) of Alnus (up-

per left), Sequoia (upper right), Quercus (lower left), and Compositae (lower right). Contours are in grains X 103/cm3. Geographic extent of Alnus, Sequoia, and Quercus species from which pollen in marine sediments is derived is indicated by shading.

Dinoflagellate cysts (>1000/cm3 ) are creases uniformly offshore to more than clustered in the northern parts of the 50% (Fig. 4). Ninety-eight percent of Northeast Pacific with peak abundance the samples contain more than 20% pine between 45”-50”N (Fig. 4). pollen and 85% of the samples have more

The relative frequency of Pinus in- than 30% Pinus. Samples from the conti-

HEUSSER AND BALSAM

FIG. 4. Maps showing distribution of concentration (grains/cm3 marine sediment) of Poly- podiaceae (upper left) and Dinoflagellates (upper right), and the relative abundance (percent of the pollen sum) of Pinus (lower left) and Z’suga heterophyk (lower right). Concentration contours are in grains X 103/cm3. Geographic extent of Tsuga heterophylla, and Pinus species from which pollen in marine sediments is derived is indicated by shading.

nental shelf of the northeast Pacific nearshore between 46”-50”N to 10% (Heusser, unpublished data), although south of 42”N and north of 59”N (Fig. highly variable, generally contain only 4). No T. heterophyllu grains were found 10 to 20% pine pollen. T. heterophyllu in sediments from the extreme north- decreases radially from more than 30% eastern and southeastern parts of the

POLLEN DISTRIBUTION

FIG. 5. Maps showing distribution of the relative abundance (percent of the pollen sum) of Picea (upper left), Alms (upper right), Sequoia (lower left), and Quercus (lower right). Geographic extent of species from which pollen in marine sediments is derived is indicated by shading.

study area. Percentages of Picea and off the coast of southern British Colum- Alnus (Fig. 5), which reach 20% in the bia, Washington, and Oregon. Sequoia, northern half of the Northeast Pacific, Quercus (Fig. 5), and Compositae (Fig. diminish seaward and southeastward, and 6), each rapidly decrease from a maxi- are absent in southern-most sites. Alnus mum of 20% off the southern California is relatively more abundant than Picea coast. Sequoia pollen is absent north of

HEUSSER AND BALSAM

FIG. 6. Maps showing distribution of the relative abundance (percent of the pollen sum) of Compositae (upper left); relative abundance (percent of the sum of pollen and spores) of Poly- podiaceae (upper right), and relative abundance (percent of all palynomorphs) of Dinoflagellates (lower map).


FACTOR 1

TSWA "ETEROP"YLU

FACTOR 3

is’ FACTOR 2 I

\

FIG. 7. Maps showing distribution of factor loadings of Factor 1, Tsuga heterophylla-Pinus (upper left); Factor 2, Quercus-Compositae-Sequoia (upper right); Factor 3, Pinus (lower left); and Factor 4, Alms-Picea (lower right).


44”N, Quercus pollen north of 49”N, and Compositae pollen forms less than 5% of the pollen total north of 50”N.

The relative number of polypod spores (vascular spores/pollen + vascular spores) decreases seaward and southeastward from 40% north of 48”N to 2% (Fig. 6). Lycopods not found in core tops south of 47”N, appear locally important in cores north of 53”N. Offshore in the same region, i.e., north of 47”N, between 25% and 75% of all palynomorphs are dinoflagellates. The relative abundance of dinoflagellate cysts decreases shore- ward, seaward and southward (Fig. 6).

Factor analysis (Imbrie and Kipp, 1971) was used to simplify the data by grouping covarying taxa into assemblages. Four factors, which accounted for more than 97% of the variability were selected.’ The geographic distribution of the factors is illustrated in Fig. 7. Thirty-nine percent of the variance is accounted for by factor 1, which has a high weighting of T. he terophy lla. High loadings diminish regularly away from a coastal strip between 45”-57”N. Factor 2 (with 14% of the variance) is informally called the California factor due to the high weightings of Quercus, Compositae, and Sequoia off California. Accounting for 32% of the variance, the Pinus factor (factor 3) is important along the coast from 37”- 42”N and seaward north of 42”N. North of 47”N, the fourth factor, Alnus-Picea (accounting for 13% of the variance), has higher loadings offshore except along the northern-most Alaskan margin.

DISCUSSION

In sediments of the continental margin of the northeast Pacific Ocean, pollen

*The factor description matrix which describes the weightings of the taxa in the assemblages, and the principal factor loading matrix (B matrix, Imbrie and Kipp, 1971), which describes the factor composition of each core top, communaiities, and the amount of variance explained by each factor are available from the National Auxiliary Publications Service (NAPS).

concentration ranges from 100 to 10,000 grains/cm3, which is comparable to quantities of pollen obtained from two core tops in the America trench (5000/g, Habib et al., 1970) and from several cores in the Pacific Ocean (3000/g, Groot and Groot, 1971), but lower than that of sediments from the Gulf of California (80,000/g, Cross et al., 1966). Not un- expectedly, the number of pollen grains in marine sediments is proportionately less than in adjacent continental sediments which are closer to the pollen source. Small quantities of pollen are found in marine sediments off Alaska (100 grains/cm3, this study; 1 grain/cm3, Colinvaux, 1974). In this area vegetation is restricted and pollen concentrations from terrestrial peats are extremely low ( 300/cm3 in peat from the Aleutian Islands, Heusser, 1973). The maximum pollen concentration in marine sediments occurs off southern British Columbia and western Washington where terrestrial concentration in peat of the lush temperate forests averages 60,000/g (Mathewes, 1973).

Oceanic regions with the greatest concentration of pollen (5000-10,000 grains) are coincident with the plume of the Columbia River, the major source of suspended sediment in the northeast Pacific (Holeman, 1968), and with run- off from rivers discharging into the Pacific Ocean via San Francisco Bay (Fig. 2). Sediment from areas offshore of smaller drainage basins and of rivers with intermittent flow contains less pollen.

The distribution of pollen in marine sediments suggests that fluvial transport is a prominent factor controlling pollen influx in the northeast Pacific Ocean. Some pollen in marine sediments is un- doubtedly derived from the air, from the reportedly small amount involved in long distance aeolian transport (Faegri and Iversen, 1964), and/or from that pro- duced by vegetation relatively close to the ocean. (Pollen in coastal waters de-


rived from vegetation close to the ocean may be comparatively insignificant due to the presence of prevailing onshore winds.) The importance of fluviomarine transport on the continental shelf and in restricted basins has been demonstrated by Muller (1959), Cross et al. (1966), Davey (1971), Koroneva (1971), and McAndrews and Power (1973).

The concentration of pollen in marine sediments appears to vary directly with the amount of suspended sediment sup- plied by rivers. Work by Peck (1973) indicates that this relationship between terrigenous influx and pollen concentration is reasonable. As shown by Peck (1973), in a small English river, pollen and lithogenous concentration were positively correlated.

Pollen concentration in the northeast Pacific does not decrease linearly with distance from shore or depth of water; rather it is polymodal, being lower on the shelf, higher on the slope and rise, and decreasing to lower values in basins. Pollen concentration seems to be positively related to the distribution of lutites which according to Kulm et al. (1975) bypass the outer shelf and are transported to the slope by subsurface currents and particle settling from over- lying waters. This agrees with previous suggestions that pollen is hydraulically similar to lithogenous particles 4-16 pm in diameter (Muller, 1959; Traverse and Ginsburg, 1966; Stanley, 1969).

Sedimentation of pollen in the northeast Pacific, therefore, is probably con- trolled by the same factors which govern the sedimentation of hydraulically equiv- alent suspended lithogenous particles. Factors controlling the sedimentation of these particles are: (1) river discharge, (2) estuarine circulation, (3) wave di- mension and direction, (4) subsurface and bottom currents, (5) density strati- fication of the water column, and (6) benthic organisms (Kulm et al., 1975).

In addition, dissolved-oxygen concentration of near-bottom waters and sedi-

mentation rate probably affect the distribution of pollen in marine sediments. Pollen is highly susceptible to destruction by oxidation (Faegri and Iversen, 1964). Therefore, preservation is presumably en- hanced in areas with low dissolved- oxygen content or where rapid sedimentation decreases the time of exposure to potentially destructive oxygenated waters. A positive relation between pollen concentration and sedimentation rate has been suggested by Bottema and van Straaten (1966) and Cross (1973). Like pollen, total organic carbon is more abundant in the rapidly deposited lutites of the continental slope of the northeast Pacific (Gross et al., 1972).

Concentrations of individual pollen taxa (Figs. 2 and 3) reflect primarily the influence of fluvial and marine sedimentation and secondarily the distribution and abundance of vegetation. Maximum concentrations of taxa widely distributed throughout the Pacific Northwest, Pinus, T. heterophylla, Picea, and Alms, are localized off the Columbia River. Taxa which are prominent in the southern por- tion (Sequoia, Quercus, Compositae) show maximum concentration off the Sacramento-San Joaquin Rivers, as does Pinus which is important in the California mountains.

As with pollen, the maximum concentration of polypod spores (Fig. 4) is lo- cated off the major rivers of the northwest Pacific coast. The resemblance of the distributions of both pine and polypod concentrations suggests a similar controlling parameter, probably related to hydraulic efficiency, as has been suggested by Koroneva (1957). The pattern of dinoflagellate concentration (Fig. 4) is not unlike that of pollen which may indicate a common controlling variable, such as marine sedimentation. The simi- larity in the distribution of pollen and dinoflagellate abundance on the south- west African shelf was considered to be a function of marine sedimentary factors, current, and sediment size according to


Davey (1971). Dinoflagellate concentration has been ascribed to factors controlling cyst productivity (temperature, turbidity, salinity, nutrients) and sedimentation (Wall, 1971). It would seem that the abundance of dinoflagellates in the northeast Pacific Ocean reflects nu- trient input of the Columbia River, although input of nonmarine dinoflagellates may also be a factor. The diminution of cyst concentration south of 44”N suggests the presence of some ecologic or sedimentary barrier.

The relative abundance of Pinus pollen (Fig. 4) in marine sediments along much of the coast reflects the multiplicity of pine trees and the voluminous produc- tion of pine pollen. Pinus forms up to 70% of pollen deposited in the Sierra Nevada (Adam, 1964), up to 50% of pollen from treeless sites in the Columbia Basin, Washington (Mack and Bryant, 1974), and up to 25% of samples from coastal southeast Alaska where pine is largely restricted to muskegs (Heusser, 1960). The relative abundance of pine pollen strongly reflects the influence of marine sedimentation. At least 30% of the pollen in most of our samples is pine. This includes samples adjacent to areas where pine is prolific as well as where pine trees and pollen are absent, such as the northern and southern extremities of the coast. This extension of pine beyond its terrestrial range probably indicates transport of pine pollen by currents, both the northwest setting Alaskan current and the south setting California current. Similar observations on the importance of surface currents in the distribution of pine pollen were made by Traverse and Ginsburg (1966) on the Great Bahama Bank.

Even more striking is the uniform increase of Pinus pollen seaward, which reflects the relative hydrodynamic efficiency of pine pollen grains, although some differential resistance to destruction may also be involved (Havinga, 1964). The selective effects of marine

transport on pinaceous pollen have been described by Cross et al. (1966) in the Gulf of California; Koroneva (1968), in a reconnaissance study of the western Pacific Ocean; and by Lubliner-Mianow- ska (1962), in the Bay of Gdansk, Poland.

Contours of T. heterophylla percentages (Fig. 4) appear to reflect the relative importance of western hemlock in the vegetation and terrestrial pollen rain, particularly north of 50”N. In the area between 50”N-57”N, however, the relative abundance of western hemlock in marine sediments does not achieve the maxima recorded in bogs and lakes of the Alexander Archipeligo, southeast Alaska (Heusser, 1960). This discrepancy may be due to the small number of northern marine samples, or to a relative increase of pine pollen resulting from current transport. Certainly the latter may account for the progressive decrease in T. heterophylla pollen away from the shoreline.

Percentages of Picea pollen in marine sediments (Fig. 5) appear cc.mparable in importance to spruce in northern forests and terrestrial pollen records. The bisaccate grains of Picea, although similar morphologically to those of Pinus, are apparently not as efficient hydro- dynamically. Picea, unlike Pinus, is not found in marine deposits off southern California, and apparently is not carried south by the California current from the spruce-hemlock forests of western Wash- ington. There is a suggestion of an offshore increase in spruce pollen;.however, further sampling is needed for verifica- tion. In the Sea of Okhotsk, Koroneva (1957) found similar differences in the relative frequency of Picea and Pinus, the former being relatively restricted to source areas, the latter, widespread.

Although geographically diverse, Alnus in particularly important in disturbed areas such as the logged forests of Oregon, Washington, and British Colum- bia, or the glacially disturbed coast of

POLLEN DlSTRIBUTION .59

Alaska. The marine record of alder percentages (Fig. 5) appears to mirror those areas of greater importance; however, the large percentages of alder pollen recorded from Alaskan sections by Heusser (1960) are not found at these offshore marine sites. Core tops from the Gulf of Alaska shelf, however, do have comparable percentages (Heusser, unpublished data). The seaward decrease in Alms may be due to differential destruction or to the hydraulic efficiency of different types of pollen grains.

The percent abundance distribution of Sequoia pollen (Fig. 5) is closely tied to the limited geographic distribution of the two Sequoia species; that of Quercus (Fig. 5) reflects the prominence of oak (more than 16 species) in California vegetation. Although four species of oak range north of California, they are only locally abundant and the relative unim- portance of oak in the continental pollen rain (4%, Hansen, 1949) is reflected in the low percentage of Quercus (less than 5%) in marine sediments off Washington and Oregon. Oak is absent in continental and marine records north of 50”N. The seaward decrease in the relative abundance of Quercus pollen was also noted in the Gulf of California by Cross et al. (1966).

The relative amount of composite pollen (Fig. 6) seems directly related to composite abundance in terrestrial vegetation and pollen rain. Maximum marine values are found in sediments bordering the composite-dominated Coastal Sage Scrub which carpets much of the cismon- tane region of southern California (Munz, 1974). The higher percentages south of San Francisco Bay may also partly reflect input from the Central Valley where composite values up to 40% were recorded by Adam (1964). Compositae percentages in marine sediments near the Columbia River are roughly comparable to the mean of composite pollen found in surface samples from eastern Washing- ton (Hansen, 1947).

Generally, the relative abundance of polypod spores (Fig. 6) in marine sediments reflects the prominence of ferns in plant communities and continental pollen spectra. Polypods, which succeed rapidly on glacially disturbed terrain and form dense ground cover in the coastal forests of the northwest Pacific, are per- haps best developed in western Washing- ton and British Columbia where they compose >40% of the pollen and spore sum (Heusser, 1960). Offshore, Poly- podiaceae form over half of the total pollen and spores. Lycopod spores are localized off the Alaskan coast where they are common in the cool, moist coastal forests and in heath and tundra environments. No lycopods were found in California sediments, either marine or continental.

Dinoflagellate percentages (Fig. 6) appear to be a function of pollen and spore accumulation as well as cyst formation and sedimentation. High dinoflagellate abundance values (> 50%) are usually found at sites in which pollen and spore concentration is comparatively low (<500/cm3). Low values (<25%) of dinoflagellate abundance are found in cores from deep waters, and are probably related to the hydraulics of pollen and spore transport.

The essence of the relative abundance of all the major pollen taxa in the North- east Pacific Ocean is expressed by the four assemblages (factors). These assemblages reflect the terrestrial geographic distribution and abundance of vegetation and pollen, as well as the selective effects of marine sedimentation. Maps of factor loadings (Fig. 7) for factors 1, 2, and 4 are closely related to the distribution of areas of optimal development of T. he terophy lfa, Quercus- Compositae-Sequoiu, and Alnus-Picea. Factor loadings of Pinus, factor 3, (Fig. 7) represent both differential marine sedimentation and the distribution of pine in forests of the Pacific Northwest. Factor analysis, a parsimonious, repro-


ducible method of analyzing large data sets, has been applied successfully to continental pollen data by Webb and Bryson (1972) and Adam (1974), and to marine organic-walled microfossils by Williams and Sarjeant (1967). Our application of factor analysis to pollen data from the continental slope and rise, and basins of the northeast Pacific Ocean suggests that pollen from marine cores is amenable to the use of statistical techniques and that these techniques are use- ful tools in simplifying complex data sets.

CONCLUSIONS

(1) The distribution of pollen on the continental margin of the northeast Pacific Ocean is a function of terrestrial vegetation, fluvial transport, and marine sedimentation. Pollen is transported into the marine environment primarily by rivers, and thereafter is transported with other fine sediments. High pollen concentrations in marine sediments appear to be positively correlated with areas where fine-grained terrigenous sediment is deposited rapidly. Pollen accumulation in marine sediments is af- fected not only by fluvial transport, but also by bottom topography, surface and subsurface currents, oxidation, and pollen concentration on the adjacent continent.

(2) The relative frequency of pollen in marine core tops from the northeast Pacific Ocean reflects the distribution of Pacific coast vegetation and secondarily the effects of hydraulic sedimentation. Marine transport seems to be a more prominent factor controlling the distribution of pine pollen. Pollen concentration, on the other hand, reflects primarily transportational and depositional processes.

(3) In the northeast Pacific, the ap- parent distinction of marine pollen assemblages-an Alaska assemblage in which Alms and Picea are relatively prominent; an Oregon-washington-

southern British Columbia assemblage in which Tsuga heterophylla is prominent; and a California assemblage in which Sequoia, Quercus, and Compositae are prominent-has been verified by factor analysis.

Future investigations of the various aspects of transport and deposition of pollen in marine sediments suggested in this paper and by others should lead to the use of pollen as a significant sedi- mentologic, stratigraphic, and ecologic tool.

ACKNOWLEDGMENTS

We wish to thank D. Cook, P. Helms, T. Moore, Jr., R. Roberts, J. Thiede, T. Walsh, and others of the core repositories at Lamont- Doherty Geological Observatory of Columbia University, Oregon State University School of Oceanography, Scripps Institution of Oceanog- raphy, and the University of Washington De- partment of Oceanography for help in obtaining samples. C. Heusser and T. Webb III made valuable suggestions about the contents of the paper during its preparation and F. Balsam provided stylistic criticisms. This research was in part supported by National Science Founda- tion Grant GB 36864 to C. Heusser and Na- tional Science Foundation Grant GX-28672 to J. Imbrie. We also wish to acknowledge grants ONR (N00014-75-C-0210) and NSF DES72 - 01568 A04 to Lamont-Doherty Geological Observatory.

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