Palynology of the last interglacial-glacial cycle in midlatitudes of Southern Chile

QUATERNARY RESEARCH 16, 293-321 (1981)

Palynology of the Last Interglacial-Glacial Cycle in Midlatitudes of Southern Chile

CALVIN J. HEUSSER

Department of Biology, New York University, New York. Nell York 10003

Received December 23, 1980

Pollen and spores in stratigraphic sections located between 40 and 42% range in age from the Holocene, through much of the Llanquihue Glaciation, to the last interglaciation. Chronology of the stratigraphy derives from some 35 r4C ages and the age relations of Llanquihue Drift and related deposits. Q-Mode, rotated, principal-components analysis of four key pollen records covering the last interglacial-glacial cycle resulted in four leading components: Nothofagus dombeyi type, Gramineae, Weinmannia -Fitzroya type, and Myrtaceae. Analysis emphasizes interaction between the first two components. Loadings of Gramineae during the interglaciation are high, unlike the Holocene; Weinmannia-Fitzroya-type loadings, prominent in the Holocene, are negligible during the interglaciation. N. dombeyi type is the primary component during Llanquihue Glaciation: it becomes modified by increases of Gramineae sometime after 31,000 and before 14,000 yr B.P. and of Myrtaceae later. The Myrtaceae with Weinmannia -Fitzroya type also registers some activity around 42,000 yr B.P. Fluctuations in the belt of westerly winds, reflecting changing meteorological conditions in polar latitudes, are suggested by these data. With the belt located farther south than it is today, interglacial climate was much drier and warmer than during the Holocene: more northerly displacement of the belt obtained when climate was colder during Llanquihue Glaciation. Evidence from comparable latitudes in the Southern Hemisphere points toward a synchrony of major climatic events indicating harmonious fluctuations in the position of the westerlies.

INTRODUCTION

The Quaternary of much of the Southern Hemisphere remains a scientifically ne- glected field of inquiry. Aside from Ant- arctica, where a program of massive proportions was mounted during the Inter- national Geophysical Year (1957- 1958) and has continued on a modest scale to the present time, extensive regions in the Southern Hemisphere have received mostly scant attention by Quaternary scientists. The Northern Hemisphere, by contrast, continues to attract greater attention; of the more than 500 abstracts of papers presented at the X INQUA Congress held in Birming- ham, England, in 1977, less than 9% dealt with the Southern Hemisphere.

Recent studies in the Australian sector have demonstrated an abundance of Quaternary deposits and a utility for climatic reconstruction (Bowler et al., 1976). The relevance of Antarctica and its fluc- tuating ice sheets in affecting many of the

observed changes is stressed (Frakes, 1978); air masses and ocean currents cooled in the antarctic region influence world climate and apparently have done so since the middle Tertiary (Kennett, 1977). Thus, the Quaternary history of the polar latitudes may be chronicled and understood from records preserved in the sediments of the Southern Ocean and on the adjacent land masses of South America, New Zealand, and Tasmania.

The current series of Quaternary palynological studies in midlatitude Chile (Heusser, 1966, 1972, 1974, 1976, 1982; Heusser and Flint, 1977; Heusser and Streeter, 1980; Villagran, 1980) is representative of the South American sector and is a continuation of the work by Auer (1933, 1958) in Fuego-Patagonian Chile. Strati- graphic positions of sections studied for pollen and spores in the Pleistocene sequence are established from the distribution and age relations of the glacial deposits.

293 0033-5894/81/060293-29$02.00/O Copyright @I 1981 by the University of Washington All rights of reproduction in any form reserved.

294 CALVIN J. HEUSSER

The glacial record was investigated by has been utilized by palynologists in only a Brtiggen (1950) and since has been worked few instances (e.g., Frenzel, 1964). out by Mercer (1976), Flint (Heusser and Flint, 1977), and Porter (1981). Four drifts recognized by Porter (1981), beginning with the oldest, are Caracol, Rio Llico, Santa Maria, and Llanquihue. Ten of the pollen- studied sections occur in various relations to the Llanquihue Drift, which represents the last (Llanquihue) glaciation; two of these apparently consist of interglacial deposits that overlie Santa Matia Drift. Pollen and spores in one of the interglacial sections of eolian silt, close to 8 m thick, point out the value of this kind of deposit which

MIDLATITUDE SOUTHERN CHILE

The southern part of the Lake District to northern Isla Chiloe (40-423) is the region covered by this study (Fig. 1). A series of glacially scoured depressions occupied by Lagos Ranco, Puyehue, Rupanco, and Llanquihue is at the western foot of the Cordillera de 10s Andes while Lago Todos 10s Santos occupies an in- tramontane trench east of Lago Llan-

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FIG. 1. Midlatitude region of southern Chile showing locations of sites where sections of Quater- nary deposits were studied. Limit of Llanquihue Glaciation from Porter (1981).

-

PALYNOLOGY IN CHILE 295

quihue. The Andes constitute a formidable glaciated range some 130 km across marked by many high peaks, among which are Tronador (3554 m), Puyehue (2240 m), Puntiagudo (2490 m), Osorno (2660 m), Calbuco (2015 m), Yate (2111 m), and Hor- nopiren (1670 m). The unglaciated Cordi- llera de la Costa bordering the Pacific Ocean is only 30 km across and low, by comparison, with elevations below 950 m. Between the cordilleras stretches the Valle Longitu- dinal which becomes submerged at Puerto Montt, and is occupied by Seno Reloncavi, Golfo de Ancud, and an adjoining system of waterways to the south. The valley was the dumping ground for Pleistocene Piedmont glaciers on the west side of the Andes in these latitudes. It is here that sections of the glacial and nonglacial deposits of the last interglaciation, Llanquihue Glaciation, and the Holocene were measured and sampled for pollen and spores.

REGIONAL VEGETATION Natural vegetation of the region is out-

lined by Schmithtisen (1956, 1960) and Oberdorfer (1960). Four distinctive forest zones are recognized between sea level and the alpine tundra. In the Valle Longitudi- nal, original forest has been replaced almost entirely by farmland. Where the effect of settlement is not as great in the cordilleras, forest communities are least disturbed by human activity. Nevertheless, fires set by man and by volcanic eruptions have been catastrophic over extensive areas. Seismic as well as volcanic influence has had a con- siderable effect in maintaining vegetation instability throughout the region (Veblen and Ashton, 1978).

Remnants of the more northerly Lowland Deciduous Forest are scattered as far south as 41”s at the northern limit of the Valdi- vian Rain Forest and up to 150-200 m in elevation (Fig. 2). Characteristic is the de-

FELLFIELDS: 0 AZORELLA INCISA 0 ADESMIA LONOIPES 0 POA SP.

PEREZIA PEDICULARIFOLIA SCRUB-GRASSLAND:

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.PERNETTYA POEPPIGI I OP. PUMILA 0 HIEROCHLOE UTRICULATA l CORTADEFIIA PILOSA

BACCHARIS MAQELLANICA

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N. ANTARCTICA

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NOTHOFAGUS DDMBEYI DASYPHYLLUM DIACANTHOIDES PSEUDOPANAX LAETEVIRENS SAXEGOTHAEA CONSPICUA PODOCARPUS NUBIQENUS PILGERODENDRON UVIFERA FITZROYA CUPRESSOIDES

(ABOVE 800M) 0 NOTHOFAGUS DOMBEYI 0 EUCRYPHIA CORDIFOLIA

AEXTOXICON PUNCTATUM WEINMANNIA TRICHOSPERMA LAURELIA PHILIPPIANA

0 NOTHOFAQUS OBLIQUA CALDtiLUVIA PANICULATA w

0 PERSEA LINGUE LOMATIA FERRUGINEA VALDIVIAN RAIN FOREST

- 4 ci 0 LAURELIA SEMPERVIRENS (LOW MONTANE) 0 AEXTOXICON PUNCTATUM

EUCRYPHIA CORDIFOLIA MYRCEUGENIA PLANIPES MYRCEUGENELLA APICUL LOWLAND DECIDUOUS FOREST

- 0

FIG. 2. Vegetation distribution including characteristic species on the west slope of the Cordillera de 10s Andes at 415; leading components are indicated by dots. See text for sources.


ciduous species of southern beech, Notho- fugus obliqua, which grows in communities with Persea lingue and Laurelia sempervirens. In addition, Aextoxicon punctatum and Eucryphia cordifolia occur mixed in the stands; they become dominant to altitudes of ca. 2.50 m in local communities on lower slopes of both the coastal and andean cordilleras. Trees of myrtaceous affinity, Myrceugenia planipes and Myr- ceugenella apiculata, frequent the un- derstories.

The Valdivian Rain Forest, ahitudinahy higher in the cordilleras, reaches ca. 600 m and descends as a zone southward to the shore of Lago Llanquihue and to sea level along Seno Reloncavi and Golfo de Ancud. This vegetation unit extends as far as the southern end of Isla Chiloe (43”3O’S). Evergreen beech, N. dombeyi, with Euc- ryphia cordifolia are the principal trees in the forest which also contains arboreal species typical of the forests higher up and lower down the slopes, as well as species, for example, Caldcluvia paniculata, Lo- matia ferruginea, and the myrtaceous Amomyrtus luma, that appear to be most distinctive of this low montane zone. Veb- len et al. (1980) find that the regeneration of the relatively shade-intolerant beech in the low- and middle-elevation andean forests depends mainly on catastrophic distur- bance by mass movement and vulcanism.

North Patagonian Rain Forest between 600 and 1000 m is high montane; it extends south to 48%. Two leading components, Laurelia philippiana and Weinmannia trichosperma, are found in association with N. dombeyi, the arboreal composite Da- syphylium diacanthoides, and Pseudo- panax laetevirens, in addition to the gymnosperms, Saxegothaea conspicua, Podocarpus nubigenus, Pilgerodendron uvifera, and Fitzroya cupressoides. Upper slopes and summit elevations in the coastal cordillera and above 800 m in the Andes contain communities dominated by Fitz- roya. These are established today only at high montane elevations whereas formerly

they were extensive across the Valle Lon- gitudinal in a belt between Lago Llanquihue and Puerto Montt (Ramirez and Riveros, 1975; Veblen et al., 1976).

Subantarctic Deciduous Forest occupies the subalpine zone to timberline which is believed to be locally depressed 100-300 m in the region as a result of vulcanism (Veb- len et al., 1977; Veblen, 1979). The beech, N. pumilio, often with Chusquea tenui- f7ora, makes up most high-elevation stands. It grades downslope into a mixture with the evergreen N. betuloides; upslope, it becomes patchy krummholz, occurring exclusively or with N. antarctica to an elevation of 1370 m. Important in the shrub layer in the mostly open forest are Drimys winteri var. andina and Maytenus disticha with Ribes magellanicum, Ovidia andina, and a number of other species. The Subantarctic Deciduous Forest of N. pumilio and N. antarctica extends to the extreme southern Andes; N. betuloides with Pilgerodendron uvifera and Drimys winteri var. chilensis forms the Subantarctic Rain Forest south of 48”s in the humid coastal belt of southernmost Chile.

Alpine tundra above the krummholz consists of scrub-grassland beyond which lie high-altitude fellfields (Veblen et al., 1977; Veblen and Ashton, 1979). Much of this ground is rocky and broadly mantled by scoria and other volcanic ejecta. Species of the scrub-grassland communities are mostly low shrubs, Empetrum rubrum, Per- nettya poeppigii, and P. pumila, and tussock grasses, Hierochloe utriculata and Cortaderia pilosa; Baccharis magellanica and P. pumila var. leucocarpa are less common shrubs, and additional herbs include Quinchamalium chilense, Senecio chionophilus, S. trifurcatus, and Euphrasia trifida. Fellfields around 1450 m elevation are sparsely colonized by Azorella incisa, Adesmia longipes, Poa sp., Perezia pedicularifolia, Senecio julieti, Nassauvia ramosissima, N. revoluta, and Hypo- choeris arenaria, among less frequent species. Microtopography, downslope


movement of the mantle, and wind are the leading factors controlling species distribution. Cyclic changes observed in the scrub-grassland are attributed to shrub life cycles and the periodic burial of plants by unstable mantle.

CLIMATE

The region at 40-42”s lies across the seasonal swing of the polar front where air masses of the subpolar westerlies and the subtropical Pacific anticyclone are in contact; consequently, cyclonic storms associated with frontal systems of the westerlies and accompanied by strong wind and heavy precipitation are frequent (Lamb, 1959; Taljaard, 1972; Miller, 1976). Pre- cipitation is heaviest during fall and winter when cyclonic activity is most pronounced. At Puerto Montt (Fig. l), for example, 66% is received at this time and only 14% in summer (Almeyda and Saez, 1958). Aver- age annual precipitation is commonly 1500-2000 mm, increasing to 4000 mm in the coastal cordillera and over 5000 mm in the Andes. Temperature in January (summer) averages 14- 16°C and in July (winter) 7-8°C. Migration of the polar front during the Quaternary, the apparent result of at- mospheric circulation changes in polar latitudes, seems to be the key to explaining vegetation and climatic changes observable in the pollen records.

METHODS

Samples for study were obtained from freshly exposed measured sections of a river cut, several road cuts, lake bluffs, and sea cliffs including their adjacent intertidal aprons; in one case, a fen deposit was sampled using a Hiller borer. Pollen and spores in the samples were concentrated in the laboratory by methods outlined, for the most part, in Faegri and Iversen (1975). Treatment included boiling in 5% KOH SO-

lution followed first by HF treatment to re- move silica and later by acetolysis. Samples of silt and clay were treated with 0.1 M sodium pyrophosphate in the method de-

scribed by Bates et al. (1978). Nylon mi- croscreens of 7 and 150 pm served to re- move sediment outside the size range of pollen and spores.

Identification under the microscope was by means of descriptions and keys (Heus- ser, 1971) and a modern reference collec- tion of species in the Chilean flora. The identification of Nothofagus is workable only as two groups: the N. dombeyi type (N. dombeyi, N. nitida, N. betuloides. N. pumilio, N. antarctica, N. leoni, and N. alessandri) with apertures marked by annular thickenings and the N. obliqua type (N. obliqua, N. alpina, and N. glauca) which is colpate without thickenings or in- aperturate. In the study region, the N. dombeyi type reflects high levels of humid- ity and cool temperature conditions whereas the N. obliqua type is indicative of relative dryness associated with greater warmth.

Pollen sums are mostly of at least 300 grains in each sample and are the basis for the pollen data presented in the form of frequency diagrams (Figs. 3- 10); frequencies shown for spores of vascular plants and oc- casionally for Sphagnum are computed from sums of pollen plus spores (plus signs indicate values <2%). Pollen influx was not calculated owing to the lithological variation in sediments in the sections and to generally widely spaced 14C dates. Plant nomenclature in general follows MuAoz (1966); Table 1 contains data on the Chilean plants in the text.

STRATIGRAPHIC SECTIONS

Rio Caunahue

The section, located northeast of Lago Ranco (Fig. l), is on the west side of the river at 140 m elevation, ca 1.5 km up- stream from the bridge crossed by Route T-55. The exposure shows 860 cm of mostly laminated silt containing several layers of organic remains and a pair of tephra layers, the upper some 3 mm and the lower 3-5 cm thick (Fig. 3). The tephra layers rest be-


TABLE 1. LIFE FORMS AND FAMILY RELATIONSHIPS OF PLANTS MENTIONED IN THE TEXT INCLUDING SPECIES REPRESENTATIVES OF GENERA SHOWN IN THE POLLEN DIAGRAMS

Seed plants Trees

Aextoxicon punctatum R. & Pav. Aextoxicaceae Amomyrtus luma (Mol.) Legr. & Kausel Myrtaceae Caldcluvia paniculata (Cav.) D. Don Cunoniaceae Dasyphyllum diacanthoides Less. Compositae Drimys winteri Forst. var. chilensis (DC.) A. Gray Winteraceae Embothrium coccineum Forst. Proteaceae Eucryphia cordifolia Cav. Eucryphiaceae Fitzroya cupressoides (Mol.) Johnston Cupressaceae Gevuina avellana Mol. Proteaceae Griselinia scandens (R. & Pav.) Taub. Comaceae Laurelia philippiana Looser Monimiaceae L. sempervirens (R. & Pav.) Tul. Monimiaceae Lomatia dentata (R. & Pav.) R. Br. Proteaceae L. ferruginea (Cav.) R. Br. Proteaceae L. hirsuta (Lam.) Diels Proteaceae Maytenus boaria Mol. Celastraceae Myrceugenia planipes (Hooker & Am.) Berg Myrtaceae Myrceugenella apiculata (DC.) Kausel Myrtaceae Nothofagus antarctica (Forst.) Oerst. Fagaceae” N. betuloides (Mirb.) Oerst. Fagaceae N. dombeyi (Mirb.) Oerst. Fagaceae N. obliqua (Mirb.) Oerst. Fagaceae N. pumilio (Poepp. & Endl.) Krasser Fagaceae Ovidia pillopillo (Gay) Meissn. Thymeliaceae Persea lingue Nees Lauraceae Pilgerodendron uvifera (D. Don) Florin Cupressaceae Podocarpus andinus Poepp. Podocarpaceae P. nubigenus Lindl. Podocarpaceae P. salignus D. Don Podocarpaceae Pseudopanax laetevirens (Gay) Seeman Araliaceae Saxegothaea conspicua Lindl. Podocarpaceae Weinmannia trichosperma Cav. Cunoniaceae

Shrubs Raccharis magellanica (Lam.) Pers. Compositae Chusquea tenuiflora Phil. Gramineae Corynabutilon vitifolium (Cav.) Keamey Malvaceae Desfontainea spinosa R. & Pav. Desfontaineaceae Drimys winteri Forst. var. andina Reiche Winteraceae Empetrum rubrum Vahl Empetraceae Ephedra americana Humb. & Bonpl. Ephedraceae Fuchsia magellanica Lam. Onagraceae Maytenus disticha (Hooker f.) Urb. Celastraceae Ovidia andina (Poepp. & Endl.) Meissn. Thymeliaceae Pernettya poeppigii (DC.) Klotzch Ericaceae P. pumilu (L. f.) Hook. Ericaceae P. pumila var. leucocarpa (DC.) Krauss Ericaceae Ribes magellanicum Poir. Saxifragaceae

Woody parasites Lepidoceras kingii Hooker f. Loranthaceae Myzodendron linearifolium DC. Myzodendraceae Phrygilanthus tetrandus (R. & Pav.) Eichl. Loranthaceae

Lianas Cissus striara R. & Pav. Ampelidaceae Hydrangea integerrima (Hooker & Am.) Engl. Hydrangeaceae


TABLE l-Continued

Herbs Acaena ovalifolia R. & Pav. Rosaceae Adesmia longipes Phil. Papihonaceae Azorella incisa (Griseb.) Wedd Umbelhferae Cortaderia pilosa (D’Urv.) Hack. Gramineae Euphrasia trifida Poepp. Scrophulariaceae Gunnera magellanica Lam. Gunneraceae Hierochloe utriculata (R. & Pav.) Kunth Gramineae Hypochoeris arenaria Gaud. Compositae Marsippospermum grandiflorum Hooker Juncaceae Nassauvia ramosissima DC. Compositae N. revoluta Don Compositae Perezia pedicutarifotia Less. Compositae Quinchamalium chilense Lam. Santalaceae Senecio chionophilus Phil. Compositae S. julieti Phil. Compositae S. trifurcatus (Forst.) Less. Compositae Tetroncium palustre L. Juncaginaceae Valeriana tapatht$olia Vahl. Valerianaceae

Vascular cryptogams Blechnum chitense (Kaulf.) Mett. Polypodiaceae Botrychium lunaria (L.) SW. var. dasenii Chr. Ophioglossaceae Equisetum bogotense Kunth Equisetaceae lsoetes savatieri Franchet Isoetaceae Lophosoria quadripinnata (Gmel.) C. Chr. Cyatheaceae Lycopodium fuegianum Roivainen Lycopodiaceae L. magettanicum (Pahsot de Beauvois) Swartz Lycopodiaceae L. panicutatum Desvaux Lycopodiaceae Polypodium feuittei Bert. Polypodiaceae

(1 Also frequently occurring as a shrub.

tween an overlying lo-cm-thick organic silt containing pieces of wood 14C-dated 10,780 -t- 250 yr B.P. (GX-3805) and an underlying, 2-cm-thick leaf-rich horizon dated 12,200 + 400 yr B.P. (GX-2935; Mercer, 1976). About 100 cm of coarse gravel are exposed above the silt unit; below are ca 40 cm of interbedded sand and gravel underlain by granitic boulders, mostly 30-40 cm across, resting in a bed of sand of which 50 cm are exposed above river level.

Pollen stratigraphy of 25 sampled levels between 400 and 840 cm in the section is divided into three pollen assemblage zones: RC- 1, Nothofagus dombeyi type- Wein- mannia -Hydrangea; RC-2, N. dombeyi type-Myrtaceae-Hydrangea-Myzoden- dron; and RC-3, N. dombeyi type- Gramineae. N. dombeyi type at 70% and more at most levels dominates the section.

A lake apparently occupied the site for

over 1400 yr following wastage of Pleis- tocene ice in the Rio Caunahue valley. Mercer (1976) describes glacial drift beneath the silt unit and states that the overlying gravel becomes part of a delta deposit downvalley. Drainage of the lake and onset of fluvial erosion apparently date to the early Holocene; the RC-1 assemblage for the upper part of the section is regarded as being regionally characteristic of this time interval (Heusser, 1966).

Puerto Octay

The first of two sections from the northwestern border of Lago Llanquihue (Fig. I) is of a fen formed in the upper tributary of Rio Chifin. The site is on the north side of Route U-95, ca. 2 km northwest of the junction of Route U-55-V near Puerto Octay. The drainage was the Pleistocene spillway of Lago Llanquihue at the time the


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lake level was ca. 100 m higher than today; it is related to another tributary of Rio Chi- fin studied previously (Heusser, 1974; Mercer, 1976). A 300-cm section consists of basal sand overlain by 200 cm of gyttja, which is fibrous in the upper 170 cm, and by 100 cm of fibrous peat containing much silt in the upper 20 cm (Fig. 4). The base of the section is 14C-dated 18,900 ? 370 yr B.P. (UW-418); additional levels at 240, 170, and 110 cm are dated, respectively, 15,800 & 550 (RL-1185), 16,580 + 730 (RL-1184), and 12,500 + 370 yr B.P. (RL-1183).

Six pollen assemblage zones are: POS-1, Gramineae-N-dombeyi type; POS-2, Myrtaceae-N. dombeyi type- Weinman- nia-Gramineae; POS-3, Myrtaceae-Hy- drangea; POS-4, N. dombeyi type- Gramineae-Cyperaceae-Polypodiaceae; POS-5, Gramineae-Cyperaceae-N. dombeyi type; and POS-6, Gramineae-Tubuli- florae-N. dombeyi type. Zone POS-1 contains as much as 72% nonarboreal components; represented are ruderal species (Pinus, Rumex, Lotus, and Piantago, for example) indicative of settlement and forest clearance; in zones POS-2 and -3, the arboreal component by contrast is 70% or more, and a hiatus in the record is suspected between zones POS-1 and -2. Zone POS-4 shows the beginning of a pro- gressive shift toward nonarboreal domi- nance which continues in zones POS-5 and -6 with values never less than 54% and reaches 89% at the beginning of the section. Comparable ages bracketing zone POS-5 suggest rapid sedimentation during the interval.

Pollen stratigraphy at this and the first spillway site studied, only 2 km to the east, is much the same. Differences in amounts of pollen and spore taxa are probably ac- counted for by rates of autogenic change. At the first site, quantities of Cyperaceae are higher and those of N. dombeyi type lower below the contemporaneous peaks of Myrtaceae and Hydrangea in both sections; also, N. dombeyi type is best represented in the upper 100 cm and the Myrtaceae are less prominent. The ages of the first site,

dated 17,370 r 670 yr B.P. (RL-120) and 18,170 + 650 yr B.P. (GX-5274; J. H. Mercer, pers. commun., 1978), and those of the current site appear comparable.

The second section from the vicinity of Puerto Octay is of a cut excavated for the realignment of Route V-55-U, located at 150 m in elevation ca. 1 km southwest of town (Fig. 1). A 60-cm-thick bed of peat and peaty silt rests above 50 cm of gravel, exposed to the base of the section, and below 800 cm of interbedded sand and gravel overlain by 100 cm of till which is covered by 150 cm of loess (Fig. 5). The unit of peat and peaty silt is 14C-dated 29,600 k 350 yr B.P. (QL-1338) at the top and 37,400 + 500 yr B.P. (QL-1339) at the base.

Four pollen assemblage zones cover 18 sampled levels in the section: PO-l, Gramineae-N. dombeyi type; PO-2, N. dombeyi type- Gramineae- Tubuliflorae; PO-3, N. dombeyi type-Tubuliflorae- Gramineae; and PO-4, N. dombeyi type- Gramineae- Myrtaceae. N. dombeyi type dominates the record in amounts reaching over 60% except in samples 1 and 2 at the top and sample 18 at the base. The sequence contained in zones PO-2 to PO-4 re- sembles the older of two sequences in a record near Rupanco, 25 km to the northeast (Fig. 1; Heusser, 1974). N. dombeyi type between 46 and 61% is also dominant, the Gramineae are secondary, and the Tubuliflorae and Myrtaceae form most of the remainder in the record dated 36,300 2 2600 yr B.P. at the top; the Gramineae in basal levels is over 60%.

Puerto Varas

Near the southwestern edge of Lago Llanquihue, three measured sections in Puerto Varas are 5 1 - 74 m in elevation and a fourth at 140 m is 2 km to the west (Fig. 1). Sections in the town are discussed by Mercer (1976) and Porter (1981) in connec- tion with changes in lake level related to fluctuations of the glacier terminus of late Llanquihue age. Section P. Varas A (Fig. 6) is a road cut in the upper part of a bluff

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along the lake ca 0.5 km north of the Plaza section for interdrift sediments of post- de Armas (Northwest Bluff site of Porter, Santa Matia, pre-Llanquihue age. The ex- 1981). A peat bed 15 cm thick rests on a posure measured (Fig. 7) shows 150 cm of gravel unit below a succession of laminated till of Llanquihue age overlain by 100 cm of silt, a pair of lahars, and loess; the 14C age loess in the upper part; drift of Santa Maria of the top of the peat is 13,145 2 235 yr B.P. age, containing a weathered granitic boul- (UW-480). P. Varas B is an exposure of the der as much as 130 cm across, is exposed at bluff at Calle Santa Rosa 539, just south off road level at the base. Nonglacial sediments the Plaza (Calle Santa Rosa site of Porter, of a paleosol between the glacial deposits 1981). Peat and peaty clay 15 cm thick rest consist of 140 cm of pumiceous silt above between beds of laminated silt, the upper the basal drift and an overlying lO-cm-thick bed capped by two lahars; the top of the ligneous layer which rests below 180 cm of peat here is dated 14,820 ? 230 yr B.P. (I- silty clay containing pebbles in the lower 5033). P. Varas C is on the south side of 130 cm and a cobble horizon. Wood from Route 225, ca. 200 m southeast of the Hotel the layer is ‘*C-dated 57,800 ?3# yr B.P. Bellavista (Bella Vista bluff site of Porter, (QL-1336); the age of a log resting beneath 1981). Here only 5 cm of peat exposed in the till in a section 10 m to the east is more the bluff is interbedded with laminated silt than 39,900 yr old (I-4170; Mercer, 1976). overlain by a lahar, another bed of lami- Four pollen assemblage zones covering nated silt, and two more lahars. The age of 41 sampled levels at Puerto Varas Longitu- the peat at the site is 13,965 c 235 yr B.P. dinal are: PVL-I. N. dombeyi type- (UW-481). A nearby site (Bella Vista Park Gramineae-Tubuliflorae- Myrtaceae; of Porter, 1981), located ca. 30 m nearer the PVL-2, Gramineae-N. dombeyi type: hotel, was dated 15,715 -t 440 yr B.P. PVL-3, N. dombeyi type - Gramineae - (GX-5275; J. H. Mercer, pers. commun., Tubuliflorae-Drimys-Lomatiu; and PVL- 1978). 4. Gramineae-N. dombeyi type. Zones

Pollen assemblage zones for the sections PVL-1 and PVL-3 in their richness of are: PVA for the youngest section P. Varas taxa contrast PVL-2 and PVL-4 which are A, Gramineae-Cyperaceae-N. dombeyi dominated by the Gramineae with few ad- type; PVB for P. Varas B, Gramineae- ditional taxa. Total arboreal pollen values Cyperaceae-Tubuliflorae-N. dombeyi rise to over 50% in zones PVL-1 and type; and PVC for P. Varas C, Grami- PVL-3; however, the zones differ, princi- neae-N. dombeyi type-cyperaceae- pally in the Drimys (maximum 32%) and Tubuliflorae. All assemblages are pre- Corynabutilon (cf. vitifolium) in PVL-3 and dominantly nonarboreal; N. dombeyi the Myrtaceae, Lycopodiumfuegianum and type, virtually the exclusive arboreal, Sphagnum in PVL- 1. The nonglacial sedi- is at most between 26 and 32% in P. Varas ments included by zones PVL-2 to PVL-4 C. These records correspond in part with are believed to be interglacial on the basis another bluff record along Calle San Jose of their stratigraphic position between the (Railroad Bridge site of Porter, 1981) which Llanquihue and Santa Maria Drifts, their dates between 13,300 and 16,270 yr B.P. pronounced weathering characteristics, (Heusser, 1974). and the indication from their pollen con-

The site of the fourth section to the west tent that ameliorated conditions were in of Puerto Varas is the south side of a road effect at the time of deposition. The “C cut along Route V-50, ca. 50 m west of the age of 57,800 yr B.P. is evidently minimal; junction of Route 5, the Longitudinal or Pan Porter (1981) points out that modern con- American Highway (Fig. 1). It is located ca. taminants could have been present in the 200 m west of the Llanquihue Drift-type sample of wood used for the age determi- section of Porter (1981) and is his reference nation. Conditions durine this interval. as . ..- . . - - ~~. ~~ ~~ -v


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indicated by the striking proportion of Gramineae, were apparently warmer and much drier than today, particularly in zones PVL-2 and PVL-4. The highly weathered sediments at the site also suggested to Mercer (1976) “that the last interglacial in this area was much warmer, or longer, or both, than the present interglaical thus far.” Zone PVL- 1, when climate appears to have become cooler and more moist, is

provisionally accorded an early Llanquihue age. Spores of the magellanic L. fuegiunum at three levels in the unit are indicative of this environmental modification.

Nueva Braunau

This section is a road cut at approxi- mately 120 m elevation on the north side of Route V-50,0.5 km west of the intersection of Route V-86 in Neuva Braunau and 7 km

PALYNOLOGY IN CHILE

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beyond the Llanquihue Drift border (Fig. 1). Some 800 cm of sediments of apparent eolian origin, including at least two paleosols distinguished by weathering hori- zons, overlie Santa Maria Drift (Fig. 8). The sediments are almost uniformly silts containing some plant fragments and pieces of pumice. Pollen counts in samples of 79 levels beginning 10 cm below the surface are at least 500 grains/sample to 450 cm,

mostly 200-300 grains/sample to 560 cm, and lOO- 150 grains in each of the four sample levels between 660 and 710 cm; re- maining samples contained only a few grains or were totally barren.

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Gramineae; and NB-4, Gramineae-N. dombeyi type. Zone NB-3, representative of the paleosol at the top of the silt 2 unit, shows a distinctively developed profile of N. obliqua type which is unlike pro- tiles in regional Holocene deposits (Heusser, 1966); otherwise, spectra for taxa of lower zone NB-2 are not different than spectra for samples of the paleosol. The abundant Liguliflorae (probably Hypochoeris) along with Plantago and Rumex in zone NB-1 are derived from cultivation and were not in- corporated when the silt 1 unit was de- posited; these plants are adventives intro- duced since the time Europeans settled in the region.

The sequence of zones NB-2 to NB-4 is not unlike the PVL-3 to PVL4 zonal sequence at Puerto Vat-as Longitudinal (Fig. 7) which is to be expected since both records postdate Santa Maria Glaciation. Nueva Braunau stratigraphy (Fig. 8) is the more detailed of the two owing to the greater number of sample levels over what seem to be equivalent intervals; it is the better record of the apparent early part of Llanquihue- Santa Maria interglaciation. The silt sequence at Nueva Braunau evidently resulted during the wastage of the glacier of Santa Maria age and may include in the record a number of stades and in- terstades .

Assemblages at Nueva Braunau and at Puerto Varas Longitudinal appear to re- semble assemblages described for the Rio Ignao nonglacial deposit located west of Lago Ranco (Fig. 1; Heusser, 1976). This deposit, considered to cover an early interstade of Llanquihue Glaciation, is dated by 14C enrtchment at 62,600 ?:T”$ yr B.P. (QL-61; Stuiver et al., 1978). One of the key differences, however, is again the presence of Lycopodium fuegianum; spores of this species are characteristic of Llanquihue age deposits and are not found in the apparent interg1acial sediments at Nueva Braunau and Puerto Varas Longitudinal.

It needs to be emphasized that the taxa in these records interpreted as interglacial, in-

eluding the consistent presence of certain thermophilic indicators, for example, N. obliqua type and Corynabutilon (cf vitifolium), are features of the modern vegetation northward in the Valle Longitudinal; the large amount of the Gramineae is also suggestive of open vegetation to the north of the study region today. Conspicuous in the Nueva Braunau and Puerto Vat-as Lon- gitudinal diagrams are the poorly developed or missing profiles of Saxegothaea conspicua, Podocarpus nubigenus, Fitzroya type, Weinmannia trichosperma, Pseudo- panax laetevirens, and Tepualia stipularis which are typical of regional Holocene profiles (Heusser, 1966).

Punta Penas

The first of two sections located along the northern border of Seno Reloncavi is on Route V-65 at Punta Penas, 3.5 km east of Puerto Montt (Fig. 1). The 280~cm-thick section (Fig. 9) is discontinuous as a result of road construction; the upper 100 cm is exposed on the north side of the road and the lower 180 cm is intertidal below a sea- wall on the other side. In the upper part, a 20-cm-thick peat rests between beds of Iaminated silt. In the lower, which is de- formed, an 8-cm-thick peat between beds of cobble gravel overlies two peat/clay hori- zons, 27 and 10 cm thick, also interrupted by gravel beds; the thicker of these hori- zons contains a 2-cm-thick tephra layer. Wood from the lower part is 14C-dated 42,400 + 500 yr B.P. (QL-1337). Wood from peat in the upper is dated 14,200 4 135 (UW-421) and plant fragments 15,200 + 160 yr B.P. (UW-442); wood was previously dated 15,400 2 400 yr B.P. (W-948; Do- brovolny and Lemke, 1961). The laminated silt higher in the sea cliff is capped by till. Samples were taken at 32 levels of the interbedded peat and clay.

Four pollen assemblage zones are: PPS-1, N. dombeyi type- Gramineae; PPS-2, N. dombeyi type- Myrtaceae; PPS-3, N. dombeyi type-Polypodiaceae; and PPS-4, N. dombeyi type-Gramineae-

PALYNOLOGY IN CHILE

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Tubuliflorae. N. dombeyi type with values frequently over 75% (maximum 92% in PPS-1) is the primary component. Values are much higher than in sections from Puerto Octay and from Puerto Varas A, B, and C (Figs. 4, 6) where N. dombeyi type forms assemblages with the Grami- neae over the same interval. The distinctive peak of the Myrtaceae in PPS-2, which is younger than 42,400 yr B.P., may correlate with the peak in zone PO-4 at Puerto Octay (Fig. 5) that is dated about 37,400 yr B.P. Trends in zones PPS-2 to PPS-4 appear not to have been influenced by facies changes over the course of sedimentation.

Punta Pelluco

The second section studied on Seno Re- loncavi is 6 km southeast of Puerto Montt at Punta Pelluco (Fig. 1). Remains of alerce (Fitzroya cupressoides) are intertidal at the site, exposed as a result of changes in level caused by the 1960 earthquake (Klohn, 1976). Logs and in situ trunks measuring up to 100 cm in diameter are found buried in coarse sand at low tide. No basal flaring characteristic of stumps was evident, suggesting that trees were buried standing in place and the forest floor in which trees are rooted is at depth. Ages of the remains de- termined by the radiocarbon laboratory at Hannover are 42,600 +ztg and over 45,600 yr B.P. (K. Klohn, pers. commun., 1977).

A succession of 400 cm of interbedded peat, silt containing wood fragments, and sand is stratigraphically higher than the forest bed across the intertidal area (Fig. 10). Broken by some 100 cm of coarse beach deposit, the succession continues higher through 500 cm of interbedded peat, silt, and sand into 300 cm of laminated silt to an unconformity below ice-contact stratified drift. The laminated silt in places higher up changes into sand which reaches a thickness of 10 m or more before being covered by drift.

Pollen stratigraphy of 21 samples in the section is divisible into four pollen assemblage zones: PPO-1, N. dombeyi

type- Gramineae-Tubuliflorae; PPO-2, N. dombeyi type- Gramineae- Cyperaceae; PPO-3, Gramineae-N. dombeyi type- Tubuliflorae; and PPG-4, N. dombeyi type-Podocarpus nubigenus -Gramineae. None of these, except possibly zone PPO-4, reflects the Fitzroya forest remains; P. nubigenus, reaching 7% in this zone, is a common associate of Fitzroya. This record of N. dombeyi type between 67 and 80%, Gramineae 8 and lo%, and only moderate diversity of taxa, in conjunction with the age determinations of the forest remains, suggests a middle Llanquihue, interstadial age for PPO-4. The zone appears to predate PPS-4 at Punta Penas (Fig. 9) which contains as much as 40% Gramineae while correlation of PPO-3 containing significant amounts of Gramineae (60%) with PPS-4 seems reasonable. Although not necessar- ily conclusive, the tephra layer in the Punta Penas section, which is younger than PPS-4 and is not in evidence at Punta Pelluco, supports this correlation.

THE INTERGLACIAL-GLACIAL POLLEN RECORD

Selected sections covering different intervals of the record are each shown with their respective pollen assemblage zones in Fig. 11. Included are regional, previously reported sections (Fig. 1) from Alerce (Heusser, 1966), Taiquemo (Heusser and Flint, 1977), Rupanco and Puerto Varas (Heusser, 1974). Some 35 14C measure- ments control the chronostratigraphy; within limits, data are chronostratigraphic and also biostratigraphic. Utility of the sections shown is somewhat variable owing to differences in thicknesses of the deposits, in sampling intervals, and in numbers of age determinations.

The section from Alerce is the most detailed for the millennia of the Holocene and for the late-glacial to 16,085 + 800 yr B.P.; additional late-glacial detail is contained in corresponding sections from Puerto Octay, Rio Caunahue, Punta Penas, and Puerto Varas. Continuity of the Llanquihue glacial


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record from the base of Puerto Octay dated interrupted succession at Taiquem6, con- 18,900 + 370 yr B.P. is shown by the upper taining eight 14C-dated levels to around sequence at Rupanco dated 19,450 + 350 yr 42,400 + 1000 yr B.P., provides a connec- B.P.; however, there is a gap between tion as well as correlation for other sections 23,750 f 620 yr B.P. at Rupanco and the earlier sequence at Puerto Octay dated

represented by this time span. The early levels at Taiquem6 are correlated with the

29,600 k 350 yr B.P. Fortunately, the un- Rupanco, Punta Penas, and ostensibly part


of the Punta Pelluco stratigraphy. The Puerto Varas Longitudinal and Nueva Braunau sections, infinitely dated more than 39,900 yr B.P., cover the last interglaciation following the close of Santa Maria Glaciation. The oldest limiting ages for the interglaciation are 57,800 ZZ$g and 62 600 ?:tg yr B.P. Correspondence of the lo&er pollen assemblage zone (PPO-4) at Punta Pelluco and the upper zone (PVL-1) at Puerto Varas, suggesting continuity, is uncertain.

Q-Mode, rotated, principal components (factor)-analysis (CABFAC; Imbrie and Kipp, 1971) of 19 leading taxa in the pollen data was carried out on sections at Alerce, Taiquemo, Puerto Varas Longitudinal, and Nueva Braunau representative of the last interglacial-glacial cycle. The purpose of the analysis, which examined 264 stratigraphic levels, was to single out the rank- ing taxa or combinations of taxa and to ascertain their behavior over the length of record. Four components, found to account for 93% of the data, are, in the order of their importance, Nothofagus dombeyi type, Gramineae, Weinmannia-Fitzroya type, and Myrtaceae. These are diagrammed relative to their factor loadings in each of the four sections (Fig. 12). However, the diagram is not set to a uniform time scale and, consequently, sections which are of different lengths appear only in part chronostratigraphic.

Alerce and Taiquem6 show similarities over the past 16,600 yr by high loadings for the Myrtaceae factor and by the subsequent pair of peak loadings for Weinmannia-Fitz- roya type; it is obvious that the Alerce data set is the far more detailed of the two. Earlier than 16,000 yr B.P., loadings for N. dombeyi type and Gramineae factors are highest and show the greatest changes; Weinmannia -Fitzroya type and Myr- taceae, although comparatively low, reveal consistent synchronous increases when N. dombeyi type values become high, and they decrease when Gramineae values rise. The Gramineae factor at Taiquemd loads higher

before 14,100 and after 31,200 yr B.P.; earlier at 42,400 yr B.P., it increases, continues to increase at Puerto Varas Longitu- dinal, and then fluctuates over the time of the last interglaciation as loadings of N. dombeyi type become higher. These fluctuations are also evident in the Nueva Braunau data set which covers the last interglaciation. The Gramineae factor is strong in these sets and indicates greater importance of the factor during the interglaciation and early Llanquihue Glacia- tion relative to the late-glacial and the Holocene.

DISCUSSION

Interaction chiefly between Nothofagus dombeyi type and the Gramineae during the last interglaciation and Llanquihue Glacia- tion can be explained by vegetation changes resulting from major shifting of storm tracks that bring moisture to mid-latitude Chile. The mechanism involves the migration of the polar front where frontal systems of the southern westerlies contact the Pacific anticyclone; today, storm tracks developed by frontal systems from the west do not penetrate, for the most part, north of 31”s (Miller, 1976). Historical evidence from various sources, including data from meteorological records (Lamb, 1972) and tree rings (LaMarche, 1975), points to the greater influence of the southern westerlies at times in effecting short-term fluctuations of rainfall in midlatitudes of Chile. This may explain the short-term fluctuations of temperature and precipitation over the past 16,000 yr reconstructed from Alerce pollen data (Heusser and Streeter, 1980). During glacial and interglacial ages of the Pleis- tocene, displacement of the westerly wind and contiguous belts was apparently pronounced and of a long-term nature. Hasten- rath (1971), plotting snowline depression during the Pleistocene in the northern Chi- lean Andes, suggested a 5” of latitude equatorward displacement in the zonal pattern of circulation. This is close to the extent of variation evident in the marine


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NotttOfaQuS Wltrmmnnia- OomLeya Gromineoe Fiy;tzrp Myrtacaaa

‘h-is- I! I 4 --z-T.4

Factor LoOdlnQ

FIG. 12. Factor loadings of Nothofagus dombeyi type, Gramineae, Weinmanniu -Arzroya type, and Myrtaceae in four representative sections-Alerce, Taiquemb, Puerto Varas Longitudinal, and Nueva Braunau--covering the Holocene, the Llanquihue Glaciation, and the last interglaciation. Relationship shown between sections at Puerto Varas Longitudinal and Nueva Braunau is provisional.

record from the Southern Ocean which indicates that the Antarctic Polar Front 18,000 yr ago was in places as much as 5-7” of latitude nearer the equator (Hays, et al., 1976; Morley and Hays, 1979). Oce- anic system changes are also evident in the latitudinal shifting of the Subtropical Con- vergence observed during times of glaciation and interglaciation (Be and Duplessey, 1976; Prell et al., 1979).

Regional interglacial conditions in midlatitude Chile were apparently relatively dry and more subtropical with warm, rain-

less summers when the Gramineae, in the beginning, almost exclusively constituted the pollen record (Figs. 7, 8). At that time the polar front is believed to have been located farther south. Later, higher levels of moisture under more temperate conditions were brought on as the front moved northward, favoring increased storm frequency and an influx of Nothofagus and other mesic taxa. During late interglaciation, climate again appears to have been relatively warm and dry when the front shifted pole- ward. It is evident from the greater propor-

tion of the Gramineae during the interglaci- species in midlatitude Chile about 12,000 yr ation that climate was far drier than it was B.P. is timed with the closing phase of the in the Holocene. Lianquihue Glaciation under conditions of

At times during the Llanquihue Glacia- rising temperature. The summer average at tion, the middle latitudes seem also to have that time was probably close to 8.5-9°C been drier than during the Holocene and which is the temperature at which L. mostly wetter than during the interglacia- fuegianum grows today. tion. Proportions of N. dombeyi type and Stratigraphic sequences of the last in- the Gramineae serve as indices in this re- terglaciation at Puerto Varas Longitudinal gard (Fig. 11). At Taiquem6, precipitation and Nueva Braunau (Figs. 7, 8) do not and temperature were both lower between contain L. fuegianum; moreover, the taxa some time before 3 1,000 and 14,000 yr B .P. and their proportions in the pollen dia- than they were during the Holocene; ear- grams, including the pronounced ratio of lier, at about 43,000 yr B.P. both were the Gramineae, are indicative of a climate higher and resembled times during the much drier and more subtropical than that Holocene (Heusser et al., 1981). prevailing regionally at present. Northward

Species of Nothofugus during the Llan- in the Valle Longitudinal, modem vegeta- quihue Glaciation probably included a large tion and climate bear a relationship to the proportion of N. pumilio and N. antarctica interglacial record. Beginning at 38-39”S, when relative cold and dryness prevailed; Nothofugus becomes less frequent in the at times of cold and wet climate, the pro- valley, and plants representative of genera portion of N. betuloides was apparently in the interglacial sequence, for example, greater. This relationship of the species Drimys winteri var. chilensis, Embothrium with climatic factors holds in the modem coccineum, Lomatia hirsuta, L. dentatu, vegetation of southernmost Chile where N. Maytenus boaria, Corynabutilon vitifolium, pumilio and N. antarctica make up the and Ovidia piflopitlo (Reiche, 1907), are forest fringe at the edge of the steppe in the characteristic members of the arboreal dry interior and gradually give way west- communities; grasses, composites, and ward to N. betuloides of the humid, Pacific other herbs and shrubs are typical of the coastal forest communities. Across this open vegetation. The climatic regime is transition at about 53”S, average January marked by 500- 1000 mm less precipitation (summer) temperatures decrease from 11 to and about 6°C higher average summer tem- 8°C while annual precipitation increases perature than in the study region (Almeyda from 300 to 2000 mm (Almeyda and S&ez, and She,, 1958). These more northerly 1958). Pollen of Nothofugus in surface latitudes are winter-wet and receive less samples along the gradient changes from 8 than half the summer precipitation recorded to 87% of the total and the Gramineae at 41”s. change from 72 to ~5% (Table 2). These Active eolian transport of silt and other data suggest a set of modem analogs. fine-grained sediments is an outstanding

Southernmost Chile is also where feature of the record of the last interglacia- Lycopodium fuegianum exists today in the tion, as is apparent from the succession of Subantarctic Rain Forest and Magellanic thick silt beds in the Nueva Braunau sec- Moorland around 54”s (Heusser, 1972). tion (Fig. 8). The silt is evidently derived Spores of this plant are found commonly at from the load that was carried to the low- many levels in Llanquihue-age sediments of land during Santa Maria Glaciation. The this study and at Rupanco, Puerto Octay, extent of the Santa Maria glacier, which Puerto Varas, Rio Ignao, and Taiquem6 was greater than the limit reached by the (Fig. 1; Heusser, 1974, 1976; Heusser and glacier of Llanquihue age, is probably a Flint, 1977). The last occurrence of the factor relating the amount of sediment



TABLE 2. POLLEN (%) IN SURFACE SAMPLES FROM SITES IN FOREST, FOREST-STEPPF AND STEPPE VEGETATION IN THE PROVINCE OF MAGALLANES, CHILE (53”37’S, 70”56’W to 52-38’S, 71”29’W)

Taxa” Forest Forest- Steppe Steppe

1 2 3 4 5 6 7 8

Nothofagus dombeyi type 87 87 78 40 22 12 8 11 Drimys + + + + -

Maytenus + + - -

Gramineae + + s 51 64 38 72 72 Myzodendron 10 4 + + + + + + Caryophyllaceae - - - + + + Acaena + - - + 8 2 + Empetrum - 8 7 - - + + + Gunnera + + 6 + -t + + + Umbelliferae - - 2 29 7 + Ericaceae + - - + 4 - + + Valeriana + + + + + + - Liguliflorae + - + + + + i 7 Tubuliflorae + + + 6 2 8 8 5 Other + f + + + + + +

I’ Nothofagus dombeyi type is represented by N. betuloides of the Subantarctic Rain Forest and by N. pumilio and N. antarctica of the Subantarctic Deciduous Forest; plus symbols denote <2%.

b Site data are averages of five samples/site.

available for reworking by wind. Winds draining the wasting andean glacier com- plex at that time appear to have been ex- ceptionally strong. The openness of the landscape, which as reconstructed was dominated by grassland, contributed to the transport of the sediments. In the forested landscape of the Holocene, or present interglaciation, deposition of eolian silt has been limited in both time and space. Local thicknesses of l- 1 .S m for early Holocene sections contrast the 5- 8 m for widespread interglacial deposits.

Pollen records from the midlatitudes of Tasmania and New Zealand, which tend to show synchrony with the events in Chile, indicate that migration of the polar front over the course of the last interglacial-glacial cycle probably has been broadly uniform throughout the temperate regions of the Southern Hemisphere. The evidence is oc- casionally fragmentary and also equivocal, but the timing and direction of change appear in a general way to be similar to the Chilean record. Data come from several

sources covering the last interglaciation. Colhoun (1980) describes the Pieman Dam section in western Tasmania which is more than 54,000 14C yr old. Interglacial Notho- fagus -Eucalyptus temperate rain forest, resembling existing forest, is reconstructed from the data; at the close of interglaciation, the forest was replaced by nonarboreal subalpine and alpine vegetation. In the Waimakariri River valley of east- central South Island, New Zealand, Moar and Gage (1973) describe a section dated more than 45,000 yr B.P. that traces the replacement of interglacial Nothofagus forest, reflecting modern temperate climate, by grassland and shrub vegetation. This transition is also recorded from north Westland at about the same latitude (Dickson, 1972); in south Westland, the early interglacial was represented by grassland, followed by grassland-shrub vegetation, and later by Nothofagus forest (Nathan and Moar, 1975). In northwestern South Island, data from interglacial sections more than 49,000 yr old imply early


Nothofagus and late Dacrydium and Nothofagus forest phases with grassland intervening (Moar and Suggate, 1979).

Data for the last glaciation in Tasmania come from the Huon River valley in the south and from Pulbeena Swamp in the northwest (Colhoun and Goede, 1979). A relatively warm, moist interstade between 53,400 and 41,150 yr B.P. is interpreted in the Huon valley when temperate rain forest succeeded and later was replaced by wet sclerophyll forest; at Pulbeena Swamp, a sequence 14C-dated 48,400 and 44,700 yr B.P. implies increased moisture at about the same time when Eucalyptus woodland developed between episodes of grassland. On South Island, New Zealand, the north Westland section at Blue Spur Road (Moar and Suggate, 1973) represents a later interstade that lasted from before 30,500 to an estimated 25,000 yr B.P. At that time, Nothofagus fusca forest appears to have replaced forest of Dacrydium cupressinum; later cooling is indicated by an increase of N. menziesii forest accompanied by grassland. In central South Island, grassland was dominant under a cold climate until about 12,000 yr ago (Moar, 1980). Since the end of glaciation, vegetation structural changes and climatic variations in Tasmania, New Zealand, and southern Chile apear also to have been temporally parallel (Macphail, 1979; Moat-, 1971, 1973).

This emerging set of relationships for the higher latitudes of the Southern Hemisphere is further broadened to include recent data from Antarctica. The 30,000-yr isotope climatic record from an ice core taken at Dome C in east Antarctica (Lorius et al., 1979) shows changes that appear to follow closely the climatic variations evident from the pollen records on the adjoining conti- nents. Data on snow accumulation rate from the core suggest relatively low values (drier conditions) during cold intervals of the Pleistocene and high values (snowier conditions) during the milder Holocene. The low rates appear to coincide chrono- logically with the maximum reached by the

West Antarctic Ice Sheet during the cold interval about 21,200 to 17,000 14C yr B.P. (Stuiver et al., 1981).

ACKNOWLEDGMENTS

These studies were supported by National Science Foundation Grants EAR76-02655 and ATM78-17048 to New York University. Ground transportation and field personnel were provided by the Empresa National de1 Petroleo (ENAP) in Santiago and arranged by C. Mor- dojovich K. and E. Gonzalez P. Field work was carried out in 1977 with S. C. Porter, M. Marino P. (ENAP), and L. E. Heusser and also in 1976 with R. F. Flint, C. Mutioz P., H. Valenzuela N. (ENAP), and L. E. Heusser; the Rio Caunahue site was sampled in 1974 with J. H. Mercer. Samples were prepared in the laboratory by L. E. Heusser; S. A. Lavery and S.S. Streeter factor analyzed the pollen data; and 14C age determinations were made by M. Stuiver and A. W. Fairhall of the University of Washington and by C. S. Tucek of Radiocarbon Ltd. S. C. Porter, T. T. Veblen, and W. A. Watts read the manuscript and made a number of constructive comments for improvement. Grateful acknowledgment is expressed to these per- sons and organizations for assistance.

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Documents

Palynology of the last interglacial-glacial cycle in midlatitudes of Southern Chile