U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Palynological Data from Pliocene Sediments, DSDP Leg 5 Site 32, Northeastern Pacific Ocean by R. Farley Fleming Open-File Report 92-712 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. TABLE OF CONTENTS Introduction Materials and Methods Age Control Data Matrices Taxonomic Comments Discussion References Appendix 1 Appendix 2 Appendix 3 Appendix 4 ILLUSTRATIONS Figure 1 INTRODUCTION Studies of Pliocene sea-surface temperatures of the North Atlantic Ocean indicate that there were intervals during the Pliocene substantially warmer than modern conditions (Dowsett and Poore, 1990; 1991). One of these intervals occurs at about 3 Ma (Dowsett and Poore, 1991). One goal of PRISM (Pliocene Research, Interpretation, and Synoptic Mapping) is to produce a paleoclimatic map for the world at 3 Ma. As part of this effort, the Pliocene Continental Climates Project within PRISM is attempting to reconstruct terrestrial vegetation patterns along the west coast of North America during the Pliocene, especially at 3 Ma. This report contains palynological data from DSDP Site 32, located in the northeast Pacific Ocean approximately 380 km off the coast of California. The data reported here consist of a matrix of absolute count data (numbers of specimens) and a matrix of relative abundance data (percentages). These data will be used in the future as a basis for making semi- quantitative and quantitative estimates of climatic parameters during the Pliocene for western North America. Only preliminary interpretations are presented in this report. MATERIALS AND METHODS Locality and Setting Leg 5 of the Deep Sea Drilling Project (DSDP, now the Ocean Drilling Program, ODP) drilled 12 sites in the northeast Pacific Ocean in 1969. Site 32 of Leg 5 was drilled near the seaward margin of the Delgada Fan, off the coast of California, at 37 degrees, 7.63 minutes north latitude and 127 degrees, 33.38 minutes west longitude (Shipboard Scientific Party, 1970). Figure 1 shows the position of Site 32 off the west coast of California. The Delgada Fan contains a mixture of terrigenous and clastic sediments (McManus and others, 1970). Most of the terrigenous sediments are derived from areas now drained by the San Joaquin and Sacramento Rivers. At present, the San Joaquin River drains the southern part of the Great Valley and the Sacramento River drains the northern part of the Great Valley. During the Pliocene, the Delgada Fan presumably received sediment from the same general area, although a marine embayment filled much of the Great Valley (Cole and Armentrout, 1979). Approximately 215 m of sediment were cored at Site 32. Cores 3 through 6 contain a total of 28.5 m of Pliocene sediments (Shipboard Scientific Party, 1970). Cores 3 through 6 were taken with little difficulty and represent a continuously cored sequence, although some disturbance of sediments was reported. On the basis of diatom analyses by Barron (in press), these cores preserve a nearly complete and relatively undisturbed record from about 3.0 Ma to 5.0 Ma. ODP stores the cores at the ODP Core Repository at Scripps Oceanographic Institute in La Jolla, California. Sample collection and sample positions Appendix 1 lists the USGS sample number, DSDP core and section numbers, and depth information for each of the 31 samples collected from Site 32 for this study. Each core at Site 32 was 9 m in length and was divided into 1.5 m sections, numbered 1-6 from the top down. Top and bottom data provided for each sample collected from Site 32 were measured from the top of the section from which the sample was taken. The depth of each sample below seafloor (meters below seafloor, mbsf) was calculated using published DSDP depth data for Site 32 (Shipboard Scientific Party, 1970) and the depth information for each core and section. The "DSDP depth" provided by DSDP was calculated for the top of each sample. The "midpoint depth" calculated for this study is for the middle of each sample interval. Discrepancies are apparent between some depths provided by DSDP and the corresponding depths calculated in this report. Sample D7706(86.44) has a depth of 86.44 mbsf according to the sample listing provided by DSDP. However, calculating the depth using the figures in Table 1 reveals that 86.56 mbsf is more accurate for this sample. Similarly, sample D7706(105.9) has a DSDP depth of 105.9 mbsf and its depth calculated with Table 1 measurements is 105.80 mbsf. Appendices 2 and 3 use the depths calculated in this study, which are listed in "midpoint depth" column of Appendix 1. AGE CONTROL The initial paleontological study of Site 32 was based primarily on calcareous nannofossils (Shipboard Scientific Party, 1970). In the initial report, sediments from cores 3-6 were assigned to the Pliocene. All sediment from Core 3 was assigned to the upper Pliocene; all sediment from cores 4 and 5 and the upper 1.5 m of core 6 were assigned to the lower Pliocene. Barron (in press) integrated his diatom stratigraphy with the biostratigraphic studies of Bukry and Bramlette (1970) and Gartner (1970) and concluded that a nearly complete interval was recovered in cores 3-6 that ranges from 3.0 to 5.0 Ma. Also, Barron (in press) refined the Pliocene diatom stratigraphy for California based on calibration with paleomagnetic and radiometric studies in the Centerville Beach outcrop section (northern California), the Harris Grade outcrop section (southern California), and DSDP Site 32. His study provides critical absolute ages for diatom horizons in the interval between 5.0 and 2.8 Ma (Barron, in press). This allows more accurate and precise dating of samples from Site 32. Appendix 1 lists the age estimates for all samples from Site 32 used in this study. J. Barron provided the first set of samples from Site 32 with his age assignments based on his calibration of diatom datums, and these dates are italicized under "age" in Appendix 1. I collected additional samples from Site 32 cores and extrapolated and interpolated the ages for these samples based on Barron's analyses. This approach accepts Barron's conclusion that the core records a complete and uniform record for the interval 3-5 Ma and assumes a constant sedimentation rate of 18 m/m.y. DATA MATRICES The data matrix of Appendix 2 contains the absolute count data for the 31 samples from Site 32. Some samples were too sparse for adequate statistical counts. For four of the sparse samples, only the presence of a taxon or category is noted; two of these samples have preliminary count data that are not considered reliable but is reported nonetheless. Some fossils were observed during preliminary scans (i.e., before statistical counts were made) that were not encountered in the sample counts. These are listed in Appendix 2 as "trace." Appendix 2 also presents fossils that were unidentified because of their preservation. These are listed as "broken," "concealed," "corroded," or "crumpled." The data matrix of Appendix 3 contains relative abundances for most of the pollen categories listed in Appendix 2. Appendix 3 omits two categories of Appendix 2, Pinus bladders and Pinus bodies. The percentage of Pinus includes one-half of the Pinus bladders counts and excludes Pinus bodies. The percentages are based on the sum of the terrestrial pollen and exclude spores, algae (freshwater and marine), and pollen of aquatic plants (i.e., Potamogeton/Triglochin). Occurrences listed as "trace" in Appendix 2 are listed as "0" in Appendix 3. The unidentified categories of Appendix 2 are combined as a single percentage in Appendix 3 and entered under " indeterminates." Appendix 3 contains count data for 27 of the 31 samples collected from Site 32. The four samples excluded from Appendix 3 are the barren samples of Appendix 2. TAXONOMIC COMMENTS Some categories included in the raw data matrix (Appendix 2) and the relative abundance data matrix (Appendix 3) need explanation. All samples from Site 32 contained common to abundant pollen referable to the Taxodiaceae, Cupressaceae, or Taxaceae. Pollen morphology in these three gymnosperm families is basically the same, with subtle differences that may permit identification at the individual family or genus level. All pollen of this group lacking diagnostic features for family or generic level taxa were referred to "TCT undifferentiated." If the pollen grain exhibited a papilla without critical details of the wall structure preserved, it was assigned to the Taxodiaceae. If a papillate fossil within this group preserved details of the wall structure associated with the tenuitas, then it was assigned to Sequoia or Taxodium as appropriate. There are six morphological categories that were not assigned to a particular botanical group. "Monosulcate type 1" is simple monosulcate pollen that could be produced by gymnosperms (e.g., cycads) or angiosperms (e.g., magnoliids). "Monosulcate type 2" is reticulate monosulcate pollen possibly produced by palms or the Agavaceae, but too few specimens were observed to allow definitive assignment at this time. "Tricolpate type 1" is simple tricolpate pollen that is prolate, psilate, and relatively small. This type is produced by a number of plant families. "Tricolpate type 2" pollen is prolate to spheroidal pollen with long colpi and a eureticulate wall having a fine reticulum. "Tricolporate type 1" is tricolporate, prolate, psilate pollen similar to tricolpate type 1 except that it is tricolporate; this type is also produced by a number of plant families. "Tricolporate type 2" is the most abundant of the types assigned to morphological categories. This pollen is tricolporate and prolate and has a very fine reticulate or foveolate pattern on the surface of the grain. Besides "dinoflagellates undifferentiated," two additional dinoflagellate types were counted. "Dinoflagellate type 1" is a small chorate cyst. "Dinoflagellate type 2" is a distinctive cyst that lacks processes, has an intercalary archeopyle, and a surface ornamentation that appears finely reticulate. Question marks beside generic names (e.g., Acer?) indicate that the identification is only tentative. This usually indicates that only one specimen was recovered and preservation or orientation allowed only tentative assignment. Familial categories are included for families that have more or less distinctive pollen but for which generic distinctions are lacking or difficult to determine. DISCUSSION Preliminary analysis of the data of Appendix 3 reveals patterns that suggest departures from modern climatic conditions during the Pliocene. In Appendix 4, relative abundances of selected taxa are plotted against absolute time. These data are compared with modern palynological data from Heusser and Balsam (1977), who determined absolute and relative abundance of palynomorphs in core top samples from 61 cores taken along the continental margin of the northeast Pacific. One of Heusser and Balsam's cores, number 54, was taken approximately 200 km east of Site 32 (Figure 1); this core will be used for comparison with Pliocene sediments from Site 32. Heusser and Balsam (1977) also compared pollen relative abundance with modern terrestrial vegetation distribution along the Pacific northwest, which may allow inferences to be made about the differences between modern and Pliocene vegetation. Although Heusser and Balsam provide a useful basis for comparison, they did not report the presence of undifferentiated TCT pollen. As discussed below, TCT is the dominant fossil in most Site 32 samples. At this time, data on TCT abundance in modern marine sites near Site 32 is lacking. All samples from Site 32 are dominated by pollen of TCT and Pinus. Plot 1 (Appendix 4) shows the relative abundance of these two groups plotted against age. In general, TCT is dominant from 4.5 Ma to 2.8 Ma. Pinus becomes dominant at about 3.75 Ma and again at 3.0 Ma. Plot 2 shows the Pinus relative abundance profile with the level of Pinus in Heusser and Balsam's modern site shown with a horizontal arrow. This comparison suggests that, except for the times around 3.75 Ma, Pinus is not as abundant in Site 32 as it is in the modern site. Adam and others (1990) reported higher TCT values in the Pliocene than in younger sediments at Tule Lake. They developed a model in which increased TCT with respect to Pinus indicates warmer conditions. Using this model, they inferred warmer conditions in the Pliocene from 2.8 Ma to 2.6 Ma (Adam and others, 1990). Sequoia pollen was present in low amounts in Site 32. Although fossils referred to the Taxodiaceae could be Sequoia or Taxodium, they are more likely to be Sequoia. Even if the Taxodiaceae and Sequoia are added together (thus representing the maximum possible Sequoia), the relative abundance of this type is significantly lower than values for Sequoia in Heusser and Balsam's modern sample (see Plot 3). Heusser and Balsam's data indicate that Sequoia stands today contribute significant amounts of pollen to adjacent marine environments. Data from Site 32 indicate that Sequoia stands were significantly reduced during the Pliocene. Other taxa in Site 32 have relative abundances similar to the modern values. For example, the relative abundance of Alnus in Site 32 (Plot 4) was more or less similar to modern values except at 3.0 Ma, when Alnus increased significantly. Several exotic taxa are present in Pliocene sediments from Site 32 that were apparently present in the Pliocene but have since been extirpated from California. These taxa are Carpinus, Carya, Ilex, Taxodium, Tilia, Pterocarya, and Ulmus. The presence of these taxa in the California Neogene is already known. For example, Axelrod (1950, 1980) reports Pterocarya and Ilex from Pliocene Sonoma florules of California; Daubenmire (1978) reports the presence of Tilia, Ulmus, and Carya in the Neogene of west central North America. Heusser (1981) recovered pollen of Ilex, Ulmus, Tilia, and Pterocarya from lower Pliocene sediments of DSDP Leg 63. Apparently Taxodium has not previously been reported from the Pliocene of California, although Leopold and Denton (1987) report Taxodium leaf fossils from Miocene rocks in the Columbia basin west of the Rocky Mountains and east of the Cascades. Some Taxodium is present at 3.61 Ma and 3.08 Ma in Site 32. Taxodium is present in swamps in southeastern U. S. today and thrives in habitats that have standing water throughout the year. Today Pterocarya occurs only in the Old World, in the Caucasus Mountains and in China and Japan (Leopold and MacGinitie, 1972). Leopold and MacGinitie (1972) estimate that modern Pterocarya grows in areas with effective temperatures equivalent to those found in central California today. In areas where it grows today, it appears to require summer rainfall. Also, Axelrod (1950) concludes that the presence of Ilex and Pterocarya indicate summer precipitation during the Pliocene. This is consistent with the presence of Taxodium and its need for year-round precipitation. These data are preliminary but some of the patterns suggest that paleoclimate in California during the Pliocene was different from the present climate. The presence of Ilex, Pterocarya and Taxodium suggests that adequate moisture was present year-round. The reduction in Sequoia suggests that, even though there was enough moisture for Taxodium, climatic conditions did not allow enough fog for Sequoia to exist in amounts comparable to today. Today Sequoia occupies foggy coastal areas (Axelrod, 1986). Additional sites along the west coast of North America (e.g., the Centerville Beach section near Eureka, California) may provide corroborative trends that will increase confidence in the patterns observed at Site 32. Results from Site 32 will be integrated with results from other sites to reconstruct a paleovegetational and paleoclimatic picture of western North America during the Pliocene. REFERENCES Adam, D. P., Bradbury, J. P., Rieck, H. J., and Sarna-Wojcicki, A. M., 1990, Environmental changes in the Tule Lake Basin, Siskiyou and Modoc Counties, California, from 3 to 2 million years before present. U. S. Geological Survey Bulletin 1933, 13 pages. Axelrod, D. I., 1950, Studies in late Tertiary paleobotany II: A Sonoma florule from Napa, California. Carnegie Institution of Washington Publication 590, 71 pages. Axelrod, D. I., 1980, Contributions to the Neogene Paleobotany of central California. University of California Press, 212 pages. Axelrod, D. I., 1986, The Sierra Redwood (Sequoiadendron) Forest: End of a dynasty. Geophytology 16(1):25-36. Barron, J. A., 1992, Paleoceanographic and tectonic controls on the Pliocene diatom record of California, in Tsuchi, Tyuichi, and Ingle, J.C., Jr., editors, Pacific Neogene: Environment, Evolution and Events. Proceedings of the 5th International Congress on Pacific Neogene Stratigraphy, International Geological Correlation Program 246, p. 25-41. Bukry, David, and Bramlette, M. N., 1970, Coccolith age determinations Leg 5, Deep Sea Drilling Project. Initial Reports , Deep Sea Drilling Project, volume 5, U.S. Government Printing Office, Washington, D.C., p. 487-494. Cole, M. R., and Armentrout, J. M., 1979, Neogene paleogeography of the western United States, in Armentrout, J. M., Cole, M. R., and TerBest, Harry, Jr., (editors), Cenozoic Paleogeography of the Western United States: Pacific Coast Paleogeography Symposium 3, Society of Economic Paleontologists and Mineralogists, p. 297-323. Daubenmire, Rexford, 1978, Plant geography with special reference to North America. Academic Press, New York, NY, 338 pages. Dowsett, H. J., and Poore, R. Z., 1990, A new planktic foraminifer transfer function for estimating Pliocene through Holocene sea surface temperatures. Marine Micropaleontology 16(1/2):1-23. Dowsett, H. J., and Poore, R. Z., 1991, Pliocene sea surface temperatures of the North Atlantic Ocean at 3.0 Ma. Quaternary Science Reviews 10(2/3): 189-204. Gartner, Stefan, 1970, Coccolith age determinations Leg 5, Deep Sea Drilling Project. Initial Reports , Deep Sea Drilling Project, volume 5, U.S. Government Printing Office, Washington, D.C., p. 495-500. Heusser, L. E., 1981, Pollen analysis of selected samples from Deep Sea Drilling Project Leg 63. Initial Reports , Deep Sea Drilling Project, volume 63, U.S. Government Printing Office, Washington, D.C., p. 559-563. Heusser, L. E., and Balsam, W. L., 1977, Pollen distribution in the northeast Pacific Ocean. Quaternary Research 7(1):45-62. Leopold, E. B., and Denton, M. F., 1987, Comparative age of grassland and steppe east and west of the northern Rocky Mountains. Annals of the Missouri Botanical Gardens 74:841-867. Leopold, E. B., and MacGinitie, H. D., 1972, Development and affinities of Tertiary floras in the Rocky Mountains, in Graham, Alan, (editor), Floristics and paleofloristics of Asia and eastern North America: Proceedings of Symposia for the Systematics Section, XI International Botanical Congress, Elsevier, p. 147-200. McManus, D. A., Weser, Oscar, Borch, C. C. van der, Vallier, Tracy, Burns, R. E., 1970, Regional aspects of deep sea drilling in the northeast Pacific. Initial Reports, Deep Sea Drilling Project, volume 5, U.S. Government Printing Office, Washington, D.C., p. 621-636. Shipboard Scientific Party, 1970, Site 32. Initial Reports , Deep Sea Drilling Project, volume 5, U.S. Government Printing Office, Washington, D. C., p. 15-56. APPENDIX 1 Appendix 1 contains sample data for the 31 samples from DSDP Site 32. Italicized numbers in age column are dates provided by John Barron and are based on his analysis of DSDP Site 32 (Barron, in press). Depths are given in meters below seafloor (mbsf). APPENDIX 2 Appendix 2 contains absolute count data for the 31 DSDP Site 32 samples in this study. Numbers in each cell are the numbers of specimens counted in the samples for each palynomorph category. APPENDIX 3 Appendix 3 contains relative abundances for selected pollen categories. All values are percentages calculated using the data in Appendix 2. See text for discussion of the categories included in this appendix. Four samples of Appendix 3 are not included because of insufficient palynomorph recovery -- these are labeled "barren" in Appendix 2. APPENDIX 4 Appendix 4 contains plots of relative abundance profiles (percentage versus age) for selected taxa from DSDP Site 32. See text for discussion. (end)