Macroflora

Abstract: Introduction Part I. Time Scales: 1. Numerical time scale in 1989 2. Magnetic polarity time scale Part II. Circum-Pacific Base Map: 3. Reconstruction of the circum-Pacific region Part III. Regional Geology and Stratigraphy: 4. Western Canada and United States 5. Meso-America 6. Western South America 7. Australasia 8. Indonesia 9. Southeast Asia and Japan 10. Eastern China 11. Eastern Soviet Union Part IV. Chronostratigraphy, Index and Guide Fossils: 12. Ammonite zones of the circum-Pacific region 13. Palynomorphs in the circum-Pacific region 14. Radiolarian biozones of North America and Japan 15. Ostracods of western Canada 16. Bivalve zones and assemblages of the circum-Pacific region 17. Belemnites of the Southwest Pacific Part V. Biogeography: 18. Macroflora of eastern Asia and other circum-Pacific regions 19. Ostracods and foraminifers of western interior North America 20. Ostracods of China 21. Corals of the circum-Pacific region 22. Brachiopods of the western Pacific 23. Belemnites of the circum-Pacific region 24. Ammonites of the circum-Pacific region 25. Fish of the circum-Pacific region 26. Marine reptiles of the circum-Pacific region 27. Climate and oceanography of the Pacific region Part VI. Atlas of Index and Guide Fossils.

Abstract: Seeds and other plant macrofossils were extracted from cores used previously for pollen analysis, and the results are presented in the style of pollen diagrams. The Zone A macroflora is characterized by abundant Picea (spruce) and Larix (tamarack) needles. The remaining species are widely distributed on swampy lake shores, in silty lakes, or in forest-floor communities. The macroflora contains no arctic element and confirms an earlier view that it is analogous to the present-day Boreal Forest in southern Manitoba. In Zone B macrofossils of Betula papyrifera (paper birch) and Abies balsamea (fir) replace Picea and Larix. Aquatic plants suggest a lake with a well-developed reed swamp and with floating-leaved and submerged aquatics. In lower Zone C-a the macrofossils continue to suggest a deep, well-vegetated lake. Higher in Zone C-a, and more strikingly in Zone C-b, annual species and shallow-water plants are common. The abundance of Zone C-b annual plants at four separate levels implies drought periods in which reed-swamp vegetation was destroyed and annuals grew on exposed lake mud. Fossils from one of the drought periods are analyzed at 2-cm intervals from a wide-diameter core. This permits an unusually close comparison of pollen and macrofossil results. Apart from the drought periods, the steady presence throughout Zone C-b of abundant annuals accompanied by shallow-water aquatics suggests a period of low water levels at Kirchner Marsh. In Zone C-c annual plants are no longer prominent, and the macroflora indicates a return to stable, deep-water conditions. In the seed diagrams the seed abundance for each taxon is shown either as percentages of the total seeds from a variable volume of sediment or as absolute numbers for a standard volume. The percentage method is preferred for general-purpose diagrams in order to clarify the main stratigraphic trends of the macrofossils and to facilitate comparison with similarly styled diagrams. The type of diagram used, however, depends on its purpose and on the material available. The characteristics of pollen and seeds as fossils are compared. Some concepts of pollen-analysis—regional parallelism, overrepresented species, pollen sum, and pollen rain—are found to apply usefully to seed analysis. Seeds are not so suitable as pollen for statistical study because they are less efficiently mixed in the “seed rain.” Seed diagrams, however, may show marked regional parallelism, which is empirical evidence of a crude mixing of seeds. Because of this process, the largest contributors to the “seed rain” are consistently represented in a seed diagram. In this sense, the principles of pollen analysis apply equally well to seed analysis, and the differences between the methods are of degree and not of kind.

Abstract: Few South American macrofloras of Paleocene age are known, and this limits our knowledge of diversity and composition between the end-Cretaceous event and the Eocene appearance of high floral diversity. We report new, unbiased collections of 2516 compression specimens from the Paleocene Salamanca Formation (ca. 61.7 Ma) from two localities in the Palacio de los Loros exposures in southern Chubut, Patagonia, Argentina. Our samples reveal considerably greater richness than was previously known from the Paleocene of Patagonia, including 36 species of angiosperm leaves as well as angiosperm fruits, flowers, and seeds; ferns; and conifer leaves, cones, and seeds. The floras, which are from siltstone and sandstone channel-fills deposited on low-relief floodplain landscapes in a humid, warm temperate climate, are climatically and paleoenvironmentally comparable to many quantitatively collected Paleocene floras from the Western Interior of North America. Adjusted for sample size, there are >50% more species at each Palacio de los Loros quarry than in any comparable U.S. Paleocene sample. These results indicate more vibrant terrestrial ecosystems in Patagonian than in North American floodplain environments ∼4 m.y. after the end-Cretaceous extinction, and they push back the time line 10 m.y. for the evolution of high floral diversity in South America. The cause of the dis parity is unknown but could involve reduced impact effects because of greater distance from the Chicxulub site, higher latest Cretaceous diversity, or faster recovery or immigration rates.

Abstract: Two small ponds in Bartow County, Georgia, northwest of Atlanta, originated by subsidence of unconsolidated surface deposits into solution hollows in the underlying lower Paleozoic Knox Dolomite. The pond sediments consist of copropelic clays 250—400 cm thick with well—preserved plant remains, covered by as much as 150 cm of colluvial deposits with moderately to poorly preserved plant fossils. The clays yield radiocarbon dates of 20,100 and 22,900 BP near their base, contemporaneous with the main Wisconsin glaciation. The full—glacial sediments are rich in pollen and plant macrofossils. The pollen assemblage is dominated by Pinus (pine), with small amounts of Picea (spruce), Quercus (oak), Ostrya type (hophornbeam), and herbaceous types. It closely resembles published full—glacial pollen assemblages from southeastern North Carolina. Pinus banksiana (jack—pine) and Picea sp. are represented by fossil needles at many levels, and the rich macroflora of aquatics shows a marked phytogeographical relationship w...