INTRODUCTION Although the primary role of orbital forcing in driving Quaternary glacial cycles is well estab- lished (Hays et al., 1976), causes of more re- cently detected abrupt climate changes at the mil- lennial scale remain unresolved. One of the last periods to register significant climate change at this scale is the late glacial, between ca. 15 000 and 10 000 14 C yr B.P., when the transition from last glacial to present interglacial conditions included several marked swings in climate. The final cold pulse, widely referred to as the Younger Dryas chron (or Greenland Stadial-1; Björck et al., 1998) between 11 000 and 10 000 14 C yr B.P., involved temporary reversion to glacial con- ditions, following a period of rapid global warm- ing (Greenland Interstadial-1), which cannot be directly explained by orbital forcing. Initially thought to be confined to the North Atlantic region, the global extent and timing of Younger Dryas cooling and the preceding warming are controversial (Singer et al., 1998; Thompson et al., 1998). The two most favored explanations for extensive cooling during the Younger Dryas invoke massive discharge of glacial meltwater into the North Atlantic; one model suggests delayed transmission of cooling to other parts of the planet via thermohaline circulation, and the other invokes virtually instantaneous transmis- sion via greenhouse gases (e.g., Lowell et al., 1995). Alternatively, it has been suggested that at other times during the late Quaternary, Southern Hemisphere climate changed before that of the Northern Hemisphere (Hays et al., 1976; Kim et al., 1998). To resolve these problems, we con- sider here two fundamental questions: (1) do shorter-term climatic oscillations register in both hemispheres, and, if so, (2) are they registered simultaneously or otherwise? Terrestrial records from New Zealand in the middle latitudes of the Southern Hemisphere should answer these questions. Although there is strong geomorphological evidence for ice advance in the Southern Alps of New Zealand at the begin- ning of Younger Dryas time (Denton and Hendy, 1994; Ivy-Ochs et al., 1999), pollen data so far show no unequivocal cooling event (McGlone, 1995) and have even been used to argue that ice advances during the Younger Dryas were localized and caused by increased precipitation, not cooling (Singer et al., 1998). However, the value of previ- ously published late-glacial pollen records from New Zealand is reduced to some extent by poor chronology, poor sampling resolution, or compla- cency to climate change (Newnham, 1999). LOCATION, METHODS, AND CHRONOLOGY We investigated the late-glacial pollen stra- tigraphy at Kaipo Bog (Fig. 1), a 73 ha ombroge- nous peat bog at 980 m altitude within montane- subalpine beech forest and shrubland in eastern North Island (38°40′S, 177°10′E). Modern pollen spectra at the site record pollen from around the site and from other altitudinally distinct vegeta- tion communities, in particular lowland to mon- tane mixed podocarp-angiosperm-beech forest at lower altitudes and grassland-shrubland commu- nities at higher altitudes. Because altitudinal zona- tion of vegetation in these uplands is controlled largely by temperature (McKelvey, 1973), the Kaipo pollen record provides an indicator of past temperature change in the region. Numerous radiocarbon dates supplement 16 independently dated tephra layers identified in the 4.4-m-long sequence, which spans the past ~15 000 14 C yr (Lowe et al., 1999). The late- glacial part of this record consists of a basal sandy mud unit overlain by two dark peat units, separated by a pale brownish-gray inorganic mud unit (Fig. 1A). Mean sedimentation rates (exclud- ing tephra layers) vary in three distinct phases: relatively slow (0.2 mm· yr –1 ) prior to ca. 12 000 14 C yr B.P., relatively fast (0.5 mm· yr –1 ) from ca. 12 000 to 9 000 14 C yr B.P., and very slow (0.1 mm· yr –1 ) thereafter (Fig. 1B). Most of the sequence was sampled at 1 cm intervals (or finer), representing an average of one sample per ~24 yr. A coarser time resolution, of one sample per ~300 yr, in the upper part of the basal sandy mud unit, dated to between ca. 14 500 and 13 200 14 C yr B.P., reflects generally lower pollen con- centrations in those samples (Fig. 2). RESULTS AND DISCUSSION Late-Glacial Warming Pollen assemblages in the basal sandy mud are dominated by grasses, other herbs, and subalpine shrubs (Fig. 2) and match those reported at other last-glacial sites in this region (Newnham et al., 1989). However, low pollen influx rates suggest that much of the pollen rain at this time was non- local, particularly Fuscospora (beech) pollen, which is capable of long-distance transport and may be strongly overrepresented in nonforested landscapes. The low ratio of lowland-montane (warm temperate) podocarp pollen to upland grass pollen (the lp:g ratio; Fig. 2) reflects a cold climate throughout the montane and higher alti- tudes of the region. The frost-hardy shrub podocarps Phyllocladus and Halocarpus were dominant at the bog margins then as they are today. Pollen influx and carbon [C] content of the sediments remained low in the lowermost peat dated at 13 420 14 C yr B.P., but were rising steadily by ca. 13 300 14 C yr B.P., accompanied by a steep increase in tree podocarp pollen, notably Prumnopitys taxifolia, while grasses and other herbs declined. This distinctive change in the pollen spectra indicates the upward expansion of podocarp forest, which had begun in lowland areas of this region at least 1000 14 C yr earlier in response to initial postglacial warming (Newnham et al., 1989). The marked increase in tree podocarp pollen and the lp:g ratio from ca. 13 300 14 C yr B.P., following the transition from sandy mud to peat accumulation at Kaipo, indicates a second and stronger phase of postglacial warming. Tree pollen reached a peak of about 65%–70% total dryland pollen, similar to Holocene levels at this site, by about 13 000 14 C yr B.P. (marked by Puketarata Tephra). The subsequent decline in Fuscospora pollen probably reflects replacement of beech trees by podocarps in low- to mid- altitude forests of the region (Newnham et al., 1995; McGlone et al., 1996). Geology; August 2000; v. 28; no. 8; p. 759–762; 3 figures. 759 Fine-resolution pollen record of late-glacial climate reversal from New Zealand Rewi M. Newnham* Department of Geographical Sciences, University of Plymouth, Plymouth PL4 8AA, UK David J. Lowe* Department of Earth Sciences, University of Waikato, Private Bag 3105, Hamilton, New Zealand *E-mail: r.newnham@plymouth.ac.uk; d.lowe@ waikato.ac.nz. ABSTRACT The temporal relationship between rapid climate shifts in the Northern and Southern Hemispheres at the end of the last glacial is crucial to understanding how the global climate sys- tem functions during periods of major transition. A detailed Southern Hemisphere mid-latitude pollen record from a climatically sensitive and well-dated upland site in New Zealand, unlike previous interpretations, shows clear evidence of late-glacial climate changes similar in struc- ture to those in the Northern Hemisphere, including a cooling interval from ca. 11 600 to 10 700 14 C yr B.P. Because the cooling interval occurred ca. 600 14 C yr before the Younger Dryas chron, our record thus also suggests that some global climatic events during the last deglaciation may have registered earlier in the Southern Hemisphere. Keywords: late glacial,Younger Dryas, palynology, tephrochronology, New Zealand.