ABSTRACT. Bryophyte and vascular plant fossils occur at many late Tertiary sites in Alaska and northern Canada. A number of these floras are reviewed here. The oldest flora, possibly of late Early Miocene age, is probably the one from the Mary Sachs gravel at Duck Hawk Bluffs, Banks Island. The youngest are of early Quaternary age.The floras are of several types. The youngest (Cape Deceit Formation) contains only plants that grow in the Arctic and Subarctic today. The Meighen Island Beaufort Formation contains a few extinct taxa (Amcites globosa) and fossil plants, such as Sambucus, Comptonia, and Physocarpus, that are not found in the present subarctic and arctic regions of North America. Some of these floras also contain fossils of a five-needle pine that may represent the Japanese Stone pine (Pinus pumila). A third group of floras, from Cone Bluff and Lava Camp, Alaska, usually contains more extinct plants (Epiprernnum cmssum, Decodon and cf. Paliurus) as well as fossils of pines in the subsection Cembme. The Mary Sachs gravel flora, with taxa such as Metasequoia, Glyptostrobus, 'Ihxodium, Juglans, and Liriodendron, stands apart from all three of the above-mentioned floral types.
Mean long-term rates of peat accumulation are higher in boreal and temperate peat deposits than in subarctic regions of Canada, although peatlands are extensive in the subarctic. Climatic change probably accounts for the development of southern peatlands during the middle to late Holocene and for the late Holocene decline in growth of many subarctic peat deposits. In northwestern peat deposits, peat of wetSphagnumlawns and treed wetlands tended to accumulate more rapidly than peat ofSphagnumhummocks and sedge fens. Long-term net rates of carbon accumulation in Canadian peatlands typically range from 10 to 35 g C/m2/yr.
Illisarvik is the site of a thermokarst lake that was artificially drained in August 1978. The lake bed is now dry in most areas and wind erosion is extensive. The surface material is either sandy peat or organic lake mud, except along the eastern margin, where it is sandy. Substrate type appears to have had little influence on distributional patterns of the colonizing vegetation. More important factors are probably erosion, surface wetness, and proximity of the lake-bed margin. Common on the lake bed are Puccinellia borealis and Arctagrostis latifolia. Other widespread species include Senecio congestus, Carex aquatilis, Descurainia sophioides, Matricaria ambigua, Artemisia tilesii, Arctophila fulva, and Stellaria longipes. Senecio and Arctophila form dense stands around the two small residual ponds. Eroded surfaces have a very scant cover of Descurainia seedlings and Puccinellia tussocks. Many elements of Illisarvik's flora are common to other recently disturbed sites near the Arctic coast of northwestern North America.
Pollen, macrofossils and matrix composition are described for a 221 cm core from a polygonal peatland overlying a late‐Wisconsin lakebed. A hydroseral succession of wetland communities occurred at the site, and included a submerged assemblage with Chara, a Carex aquatilis ‐ Eleocharis marsh, a fen, and finally a Sphagnum ‐ Ledum bog. A transition about 9,600 B.P. to a wetter S. balticum ‐ Andromeda carpet is attributed to formation of permaforst and polygonal ice wedges. This community, sometimes with S. compactum and Chamaedaphne, prevailed until about 3,000 B.P. when the polygon became high centered, and peat growth declined. Peat growth rate is determined from 11 14C dates, and is used to calculate pollen influx. Apparent periodic oscillations every 2,000 years, in total influx, are not accepted as sufficient evidence of treeline fluctuations.
The marine strata here named the Hvitland beds occur above Paleogene sand and beneath glacial diamicton. They contain marine molluscs, ostracodes, and benthic foraminifers, and represent water depth of 10-30 m and water temperature slightly warmer than present. The assemblage comprises a mixture of Atlantic/Arctic and Pacific faunas. Mosses, vascular plants (herbs) and insects in the marine strata record tundra conditions on adjacent land. The foraminifers represent the Cibicides grossus Zone (minimum age of 2.4 Ma) which is also known from late Pliocene sites in the North Sea, Baffin Island, Greenland, the Beaufort-Mackenzie Basin, and Arctic Alaska. Ostracodes in the Hvitland beds include four extinct (since 2.4 Ma) species also present in the Gubik Formation of northern Alaska, and at Kap K¢benhavn and Loden Elv in northeastern Greenland. The paleomagnetically reversed Hvitland beds (with tundra vegetation) are younger than the Beaufort Formation (with forest vegetation) which, on Meighen Island, includes paleomagnetically reversed strata dating from the youngest (ca. 3 Ma) reversed zones of the Gauss magnetic chron. Thus, the Hvitland beds (also reversed but no younger than 2.4 Ma) must date from the earliest (reversed) part of the Matuyama magnetic chron which commenced ca. 2.5 Ma. Correlation with the Bigbendian unit of the Gubik Formation is suggested.
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