U.S. Geological Survey


Middle Pliocene Paleoenvironmental Reconstruction:  PRISM2

By Harry J. Dowsett1, John A. Barron2, Richard Z. Poore1, Robert S. Thompson3, Thomas M. Cronin1, Scott E. Ishman4 and Debra A. Willard5

1U.S. Geological Survey, 955 National Center, Reston, VA 20192
2U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA  94025
3U.S. Geological Survey, Box 25046, Mail Stop 919, Denver, CO 80225
4Department of Geology, Southern Illinois University, Carbondale, IL  62901
5U.S. Geological Survey, 926A National Center, Reston, VA 20192

Also Available on the World Wide Web
Version 1.0

[NOTE: All tables are in PDF format and require Adobe Acrobat Reader. If Acrobat Reader is not installed on this computer, it can be downloaded free of charge from the Adobe Web site.]
[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.]

1.  Introduction and Background

Anthropogenic greenhouse gas emissions and modification of land surfaces are expected to cause the earth廣 climate to warm (IPCC, 1995).  However the amount and details of the warming are still highly uncertain.  Identifying and predicting any human related changes must take into account natural climate variability and the complex interactions of the different components of the Earth廣 climate system. As part of  the USGS  Global Change Research effort,   the PRISM (Pliocene Research, Interpretation and Synoptic Mapping) Project has documented the characteristics  of middle Pliocene climate on a global scale.  The middle Pliocene was selected for detailed study because it spans the transition from relatively warm global climates when glaciers were absent or greatly reduced in the Northern Hemisphere to the generally cooler climates of the Pleistocene with expanded Northern Hemisphere ice sheets and prominent glacial-interglacial cycles.

The PRISM Project had two primary goals.  The first was to identify and characterize the nature and variability of climate during this time of past global warming as an indication of how the Earth might respond to future warming.  The second goal was to develop a series of global scale, quantitative datasets for use in experiments to model climate and environmental conditions during the mid Pliocene.   The Pliocene reconstruction is being used  to test the ability of climate models to simulate past warmer conditions on earth and to provide insights into the mechanisms and effects of global warming (Dowsett et al., 1992; Chandler et, al., 1994; Sloan et al., 1996; Haywood et al., 1999).

The purpose of this report is to document and explain the  PRISM2 mid Pliocene reconstruction.  The PRISM2 reconstruction consists of a series of 28 global scale data sets (Table 1) on a 2° latitude by 2° longitude grid.  As such, it is the most complete and detailed global reconstruction of climate and environmental conditions  older than the last glacial.

PRISM2 evolved from a series of studies that summarized conditions at a large number of marine and terrestrial sites and areas (eg. Cronin and Dowsett, 1991; Poore and Sloan, 1996).  The first global reconstruction of mid Pliocene climate (PRISM1)  was based upon 64 marine sites and 74 terrestrial sites and included data sets representing annual vegetation and land ice, monthly sea surface temperature (SST) and sea-ice, sea level and topography on a 2°x2° grid  (Dowsett et al. (1996) and Thompson and Fleming (1996)).  The current reconstruction (PRISM2) is a revision of PRISM1 that incorporates several important differences:

1)  Additional sites were added to the marine portion of the reconstruction to improve previous coverage.  Sites from the Mediterranean Sea and Indian Ocean are incorporated for the first time in PRISM2.

2)  All Pliocene sea surface temperature (SST) estimates were recalculated based upon a new core top calibration to the Reynolds and Smith (1995) adjusted optimum interpolation (AOI) SST data set.  This reduced some of the problems previously encountered when different fossil groups were calibrated to different modern climatologies (Climate / Long Range Investigation Mapping and Predictions [CLIMAP], Goddard Institute for Space Sciences [GISS], Advanced Very High Resolution Radiometer [AVHRR], etc.).

3)  PRISM2 uses a +25m rise in sea level for the Pliocene (PRISM1 used +35m), in keeping with much new data that has become available.

4)  Although the change in global ice volume between PRISM1 and PRISM2 is minor, PRISM2 uses model results from Prentice (personal communication) to guide the areal and topographic distribution of Antarctic ice.  This results in a more realistic Antarctic ice configuration in tune with the +25m sea level rise.

All data sets are available by contacting hdowsett@usgs.gov  or visiting:

2.  PRISM Time Slab Concept

The PRISM2 reconstruction is a global synthesis of a period of relatively warm and stable climate lying between the transition of oxygen isotope stages M2/M1 and G19/G18 (Shackleton et al., 1995) in the middle part of the Gauss Normal Polarity Chron.  The reconstruction spans the interval of 3.29 Ma to 2.97 Ma (geomagnetic polarity time scale of Berggren et al., 1995) (Figure 1).  Previous PRISM reconstructions used the geomagnetic polarity time scale of Berggren et al. (1985) which dated the PRISM time slab at  3.15 to 2.85 Ma.  This interval occurs prior to the 2.5-2.4 Ma oxygen isotope excursion which represents a major climate step toward modern conditions (northern hemisphere ice volume increased, polar fronts were strengthened and glacial-interglacial variation intensified) (Sancetta and Silvestri, 1986; Raymo et al., 1989; Hodell and Ciesielski, 1991).
Fig. 1

Figure 1.  PRISM2 time slab correlated to the geomagnetic polarity time scale of Berggren et al. (1995) and the benthic oxygen isotope record from ODP Site 846 (Schackleton et al., 1995).  Numbers in parenthesis adjacent to magnetic polarity indicate ages of subchron boundaries according to Berggren et al. (1985).  Modern isotopic value from Schackleton et al. (1995) shown as vertical dashed line. 

While the interval of time between 3.29 and 2.97 Ma (PRISM time slab) is distinct in that mean conditions were different than the intervals immediately surrounding it, there is a high degree of variability within the time slab (Dowsett and Poore, 1991; Barron, 1992a; Hodell and Venz, 1992; Shackleton et al., 1995) (Figure 1).  Other than glacial stages KM2 (ca. 3.12 Ma) and G20 (ca. 3.01 Ma), benthic foraminiferal oxygen isotope values were either equal to or isotopically lighter than those of today (Shackleton and others, 1995).   Nevetheless, as emphasized by Tiedemann and others (1994), the 41-kyr period of Earth廣 obliquity dominates the Pliocene climate record.   For marine data points that were generated from time series studies, we have adopted a strategy whereby we develop an estimate of mean "interglacial" conditions within the time slab.  This minimizes the problems associated with point to point correlation between data sites separated by large geographic distances.  The late Pleistocene analog would be to provide a single SST value representing average winter and summer interglacial conditions at each site (e.g., average SST of isotope stages 5, 7 and 9).

The 3.29 to 2.97 Ma interval is long enough to be reliably identified and correlated between marine sequences independent of climatic characteristics because of its proximity to a number of biostratigraphic and magnetostratigraphic events (Berggren et al., 1985; 1995; Dowsett, 1989a,b).  Deep sea records and, to varying degrees, ocean margin records, can be correlated with some confidence to this interval.  Many of our terrestrial records come from short sequences that rely on limited radiometric dates and magnetostratigraphy for chronology.  The sparseness of long terrestrial time-series with multiple age control points makes identification of high frequency variability and integration of our terrestrial paleoclimate estimates into our time-slice interval less certain than our marine estimates.  This is a problem with all terrestrial paleoclimate reconstructions.

In the remainder of this report we use the terminology "3 Ma" and "middle  Pliocene" to indicate our time interval.

3.  Materials and Methods

The distribution of the 151 sites (Tables 2 and 3) from which fossil data were analysed for PRISM2 are shown in Figures2Aand2B. The terrestrial data locations have not changed from PRISM1.  The marine reconstruction benefits from the addition of sites in the Medditerranean, Indian Ocean, Southwest Pacific Ocean, and North Pacific Ocean (Figure 2A and Table 2).  These sites were chosen to fill gaps in our coverage.

3.1  Recalibration of SST estimates

A major change between this and the PRISM1 reconstruction is the recalibration of all modern marine data to the modern SST of Reynolds and Smith (1995).

Analysis of the CLIMAP modern data set (see Prell, 1985) and the modern SST data used by the Goddard Institute for Space Science (GISS) model showed significant differences with anomalies sometimes exceeding the magnitude of estimated Pliocene temperature change.  Because of this and inter-group calibration problems, we recalibrated all modern samples and all Pliocene localities, using the 1°x1° SST of Reynolds and Smith (1995).  Foraminifer transfer functions GSF18 and GSF21 were recalibrated and their resultant coefficients are reported in Dowsett and Verardo (in prep.).   All foraminifer, diatom and ostracode estimates of SST are now based upon the same modern temperature field.


Figure 2A.  Marine localities used in this study.

Click on figure for a high-quality version in a new window.

3.2 Foraminifers

Middle Pliocene foraminifers were analyzed from 34 sites by a number of workers (Table 2).  These sites are skewed toward the Atlantic (60%) but cover all major ocean basins.  In many cases existing magnetobiostratigraphy was sufficient to create age models but in some instances new biostratigraphic analysis was employed to help scale the sequences.  Sea-surface temperatures were estimated from these sites using factor analytic transfer functions, modern analog technique (MAT), or semiquantitative comparison to modern faunas (Dowsett and Poore, 1990, 1991; Dowsett, 1991; Dowsett et al., 1996; Dowsett and Robinson, 1998; Poore, 1999).

3.3 Diatoms

Middle Pliocene diatoms were counted by Barron (1995, 1996a, b) in 16 Southern Ocean  and 6 North Pacific deep sea-cores.  Age models for these cores were based on existing magnetostratigraphy and both published and refined diatom biostratigraphy (Barron, 1996a, b).  Diatom based SST estimates for the Southern Ocean were determined by estimating the relative position of the Antarctic Polar Front (APF) relative to the various sites.  North Pacific SST was estimated using equations generated by Barron (1995) based upon the relative ratios of key taxa.

3.4 Ostracods

Middle Pliocene ostracodes were counted from 12 sites in the Northern Hemisphere including Central America, the eastern United States coastal Plain, Tjornes, Iceland, Meighen Island, Alaskan Arctic coastal Plain, North Sea, and Japan.  In each region age models were constructed using  magnetobiochronology and shallow sea bottom temperatures were quantitatively estimated by transfer function, MAT, or environmental preference matching (Cronin and Dowsett, 1990; Cronin, 1991a,b; Wood et al., 1994).

3.5 Pollen and Plants

Information on middle Pliocene vegetation was compiled from fossil pollen and plant macrofossil data from over 75 sites (Table 3, Figure 2B) from all of the continents of the world (Thompson and Fleming, 1996).  Chronological controls for these sites were provided by a variety of methods, including radiometric dating, tephrochronology, and biostratigraphy.  Quantitative estimates of past terrestrial climates are available from very few sites, and thus most middle Pliocene paleoclimates on land are expressed as qualitative estimates of changes in temperature and precipitation relative to the present-day climates at the study sites.


Figure 2B.  Terrestrial localities used in this study.

Click on figure for a high-quality version in a new window.

4.  Data Sets

The PRISM2 reconstruction is presented as a series of matrices (see Table 1), each containing 90 rows and180 columns, thereby representing the earth at a resolution of 2° latitude by 2°longitude.  Each cell in this grid is designated either land or water, based on which element comprises the majority (>50%) of the cell.  If water, a cell has either a sea surface temperature or is covered by sea ice ( -1.8°C).  If a cell is designated land, it contains one of seven land cover categories (desert, tundra, grassland, deciduous forest, coniferous forest, rain forest or ice).  In addition, land cells are given a topographic elevation.   Each data set is discussed below.

4.1  Land-Sea Distribution (Sea Level)

The initial PRISM 8x10  and PRISM1 2x2 reconstructions used a +35m sea-level rise for determining land-sea elevations  (Dowsett et al., 1994; PRISM, 1995).  For PRISM2 we have adopted a more conservative +25m sea-level rise (Figure 3) in keeping with the conclusions of Kennett and Hodell (1993).  Based upon estimates of the sea level rise equivalent of various ice masses, a 25 m rise in sea level requires significant reduction of Greenland and Antarctic ice volume.

Figure 3

Figure 3.  Emergent land areas during the mid Pliocene plotted on a 2x2 grid. 

Elevational data from the ETOPO5 five-minute topographic grid (Edwards, 1992) were used to
provide the basis for constructing a middle Pliocene land-sea distribution grid.  In this process, we determined whether the elevation of each ETOPO5 point in a given 2° x 2° cell was below, at, or above the 25 m above present-day sea level.  If the number of ETOPO5 points at or above the 25 m elevation exceeded those below that elevation, then the 2° x 2° was determined to be land during the middle Pliocene.  If the number of ETOPO5 points below the +25 m sea level exceeded those at or above this elevation, then the 2° x 2° cell was declared to be covered by water.

The digital data for sea level are provided in Appendix 1, where "1" indicates land and "0" indicates water.

4.2  Sea Surface Temperatures

Table 2 lists 77 marine localities/sections that were used for our SST reconstructions.  Included are the modern February and August SST廣 at the sites (data from Reynolds and Smith, 1995), estimated Pliocene SST廣 and the resulting anomalies (Pliocene minus Modern) of these estimates used in the PRISM2 and previous PRISM1 reconstructions.  A  reference is made to the source of the SST data, the method used (quantitative, semi-quantitative, qualitative) in making the estimates, the average temporal resolution and an indication as to whether or not the mid Pliocene section was constrained by magnetic stratigraphy.  The distribution of control points for the reconstruction is uneven and primarily  reflects the availability of suitable material for study.  Details of the techniques are given in Dowsett and Poore (1991), Dowsett (1991), Cronin and Dowsett (1991), Dowsett and Robinson (1998). Barron (1996a,b), and Dowsett and Verardo (in prep).  When available,  estimates published by other  workers were used to augment and cross check the estimates derived by the PRISM2 study.

Several new data points have been added since PRISM1.  Estimates of Mediterranean SST were derived from planktic assemblages recovered on Sicily and Crete (Spaak, 1983).  These assemblages, along with data from Thunnell (1979) suggest a positive deviation in temperatures during the mid Pliocene relative to today.   Middle Pliocene samples from ODP Site 722 in the Indian Ocean were analysed and indicate a minor warming of +1 to +2°C.  South Pacific estimates now include a sequence taken within the Wanganui Basin of New Zealand.  While there is little evidence for paleotemperature change along the west coast of South America, the southwestern Pacific shows temperature anomalies of +2 to +3°C relative to today.

modern august

[A] Modern August SST - Modern Vegetation

Pliocene August

[C] Pliocene August SST - Pliocene Vegetation

modern february

[B] Modern February SST - Modern Vegetation

Pliocene February

[D] Pliocene February SST - Pliocene Vegetation

Figure 4.  A,B  Modern SST (after Reynolds and Smith, 1995) and vegetation (modified after Matthews, 1985).  C,D  Pliocene SST and vegetation.  Sea ice distributions shown in gray; vegetation legend.

Click on maps to view high-quality versions in new windows.

To create a global data set,  SST anomalies, determined by calculating differences between Pliocene estimates and modern temperatures (Figure 4) at the location of each site, were plotted as individual points on a 2°x2° grid representing the Earth.  Modern SST contours served as a rough guide in the drawing of mid Pliocene SST contours around the control points, because it was assumed that the general pattern of modern oceanic surface current systems was present in the mid Pliocene.   Boundaries between anomaly bands were smoothed so as to make even temperature gradients.  Finally, this smoothed, contoured anomaly field was added to the modern SST of Reynolds and Smith (1995) to create a mid Pliocene SST map (Figure 4).

Because we estimated winter and summer SST (February and August), we produced two primary Pliocene SST maps in this fashion (Figure 4).  The remaining 10 months of the year were constructed by fitting a sine curve to the February and August SST estimates (Dowsett et al., 1996).

On Appendices 2.1 - 2.12, each cell in a 2°x2° global grid designated as water (see section 4.1) is given a SST in degrees Celsius.  Cells designated land are given the code -999.  Sea-ice  is designated with SST set to -1.8°C.

4.3  Sea-Ice Distribution

Northern Hemisphere sea-ice distribution is unchanged from PRISM1 except for adjustments to accommodate the newer +25m sea level. (see Dowsett et al., 1996).  Southern Hemisphere sea-ice is slightly modified from PRISM1 (Barron, 1996a,b).  The PRISM2 August (peak winter) sea ice for the mid Pliocene has been arbitrarily placed at between 4 and 6° of latitude further to the south than the present day (Figure 4).  To obtain a  Pliocene winter sea ice coverage we started with the average summer sea ice coverage derived from the 14  year monthly sea-ice NOAA satellite data (Schweitzer, 1995).   The modern average summer coverage was  incorporated into a 2 x 2 degree matix and modified to fit the + 25 meter sea-land boundary and the Pliocene sea surface temperature projections discussed in the previous section (Figure 4).

The  model experiments require a sea ice configuration for each of the twelve months of the year.   In order to create 12 sets of sea-ice distribution we took  the winter and summer end-member distributions for each polar area and then used the modern monthly average sea-ice data compiled in  Schweitzer, (1995) and the PRISM2 Pliocene monthly sea surface temperature projections to guide modification of the  winter and summer end- members into  12 monthly intervals  of sea-ice coverage.

Twelve 2°x2° global grids are provided with estimated average monthly sea-ice distributions (Appendices 3.1 - 3.12).  Sea ice is designated with "1", land with "8" and water without sea-ice as "0".  Sea-ice can also be read off the SST fields where cells with SST set to -1.8°C are designated as sea-ice.

4.4  Land Ice Distribution

In the PRISM2 reconstruction, ice volume and areal coverage on Greenland was reduced by 50%.  All other Northern Hemisphere ice (Iceland and mountain glaciers) were removed.  The PRISM2 reconstruction uses model results from Prentice (personal communication) to guide the areal and topographic distribution of Antarctic ice.  This results in a more realistic distribution of ice.

The areal distribution of ice can be read from Appendix 5 which designates vegetation and land cover categories for each cell in the 2°x2° global grid (see section 4.6).

4.5  Land Surface Topography

As discussed in Thompson and Fleming (1996), Pliocene elevations were apparently lower than present-day in the western Cordillera of western North America and in the Andes of South America (Figure 5).  The reduction in the size of the Greenland and Antarctica Ice Sheets also resulted in a net reduction in elevation in those areas.  On the other hand, data discussed in Thompson and Fleming (1996) suggest that the east African rift zone was elevationally higher than at present.  Following these authors, we set Pliocene elevations in parts of North and South America at half of their modern values, and the elevation of portions of the Greenland Ice Sheet were reduced.  The elevations of Antarctica were taken directly from Prentice (personal communication).  The elevations of grid points in the east African rift zone were set at 500 m above those on the modern grid.

Figure 5

Figure 5.  Pliocene topography.  Contour Interval 500m.

Appendix 4 provides elevation in meters above sea level for each cell in the 2°x2° global grid.

4.6  Vegetation Distribution

PRISM2 vegetation is identical to that in PRISM1 (see Thompson and Fleming,1996).  We use seven land cover categories that are a simplification of the 22 land cover types of Matthews (1985).  The distribution of vegetation or land cover categories can be found in Figure 4 and Appendix 5 where cells designated 0 = water, 1 = desert, 2= tundra, 3= grassland, 6= deciduous forest, 7= coniferous forest, 8= rainforest, and 9= land ice ( See Figure 4).

5.  Summary

The PRISM2 reconstruction is an internally consistent  global summary of many important components of the earth廣 climate and surface conditions during the mid Pliocene.  It is the most complete summary of the earth廣 climate and environmental condition beyond the last interglacial and provides an opportunity to test and refine our ability to decipher past environments and model climates that are different from the present.

Important features of PRISM2 compared to modern are:

1.  Greatly reduced continental ice volume with a small ice cap on Greenland being the only continental ice in the Northern Hemisphere.

2.  Greatly reduced sea-ice with the Arctic being seasonally ice free.

3.  Sea level change of + 25 meters which requires substantial reduction of the Antarctic Ice Sheet.

4.  Increased SST in high latitudes and unchanged SST in low latitudes.  Warming is most pronounced in the northeastern North Atlantic sector.

5.  Expansion of evergreen forests to the margins of the Arctic Ocean,  a reduction of desert area in equatorial Africa and essential elimination of polar desert and tundra regions in the Northern Hemisphere.  A small amount of deciduous vegetation occurred at the edge of the Antarctic continent.

6.  Acknowledgements

Earlier versions of this text were read and reviewed by Mark Chandler (NASA), Thomas Crowley (Texas A&M) and Milan Pavich (USGS).  We thank these individuals for their comments which greatly improved the final product.  Over the course of this study scores of researchers from around the world kindly provided their time, data and expertise.  Any attempt to list these individuals would be impossible.  To all of you, both critics and supporters, we thank you.  It was your input that helped make the PRISM2 reconstruction possible.  The PRISM effort was supported by the USGS Global Change Program.  The marine reconstruction would not have been possible without the cooperation of the Ocean Drilling Program.

7.  References

This section contains all references cited in the text as well as publications related to data or interpretations used in the reconstructions.

Adam, D.P., 1994.  Pliocene pollen data set dynamics:  Tulelake, California and Lost Chicken Mine, Alaska.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23: 6-10.

Adam, D.P., Bradbury, Rieck, H.J., and Sarna-Wojcicki, A.M., 1990.  Environmental Changes in the Tulelake basin, Siskiyou and Modoc Counties, California, from 3 to 2 million years before present.  U.S. Geological Survey Bulletin 1933: 1-13.

Adam, D.P., Sarna-Wojcicki, A.M., Rieck, H.J., Bradbury, J.P., Dean, W.E., and Forester, R.M., 1989.  Tulelake, California:  the last 3 million years.  Palaeogeography, Palaeoclimatology, Palaeoecology, 72: 89-103.

Ager, T.A., 1994.  Terrestrial palynological and paleobotanical records of Pliocene age from Alaska and Yukon Territory.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23:  2-3.

Akhmetiev, M. A., 1991. Flora, vegetation, and climate of Iceland during the Pliocene. Pliocene Climates of the Northern Hemisphere:   abstracts of the Joint US/USSR Workshop on Pliocene Paleoclimates, Moscow, USSR, April, 1990. U.S. Geological Survey Open-File Report 91-447:  8-9.

Akhmetiev, M. A., G. M. Bratoeva, Giterman, R.E., Golubeva, L.V., and Moiseeya, A.I., 1978.  "Late Cenozoic stratigraphy and flora of Iceland." Transactions, Academy of Sciences of the USSR 316.

Andersson, C., 1997.  Transfer function vs. modern analog technique for estimating Pliocene sea surface temperatures based on planktic foraminiferal data, western equatorial Pacific Ocean.  Journal of Foraminiferal Research, 27: 123-132.

Axelrod, D.I., 1944.  The Sonoma flora (California).  Carnegie Institute of Washington Publication, 553: 167-206.

Ballog, R.A., and Malloy, R.E., 1981.  Neogene palynology from the southern California continental borderland, Site 467, Deep Sea Drilling Project Leg 63.  In:  Yeats, R.S., Haq, B.U., et al. (Editors), Initial Reports of the Deep Sea Drilling Project, 28:  565-576.  U.S. Government Printing Office, Washington, D.C.

Barron, J.A., 1992a. Pliocene paleoclimatic interpretation of DSDP Site 580 (NW Pacific) using diatoms. Marine Micropaleontology, 20:23-44.

Barron, J.A., 1992b. Paleoceanographic and tectonic controls on the Pliocene diatom record of California. In Tsuchi, R., and Ingle, J.C., Jr., eds., Pacific Neogene: Environment, Evolution, and Events. Univ. of Tokyo Press: Tokyo: 25-41.

Barron, J.A., 1995.  High resolution diatom paleoclimatology of the middle part of the Pliocene of the northwest Pacific.  In Rea, D.K., Basov, I.A., Scholl, D.W., and Allan, J.F., eds., Proc. ODP, Sci. Results, 145: 43-53. College Station, TX (Ocean Drilling Program)

Barron, J.A., 1996a. Diatom constraints on the position of the Antarctic Polar Front in the middle part of the Pliocene.   Marine Micropaleontology, 27:195-213.

Barron, J. A., 1996b.  Diatom constraints on sea surface temperatures and sea ice distribution during the middle part of the Pliocene.  U.S. Geological Survey Open-File Report, 96-713: 1-45.

Berggren, W.A., Kent, D.V. and Couvering, J.A., Van, 1985.  Neogene geochronology and chronostratigraphy.  In, Snelling, N.J., ed., The Chronology of the Geological Record.  London, Geological society of London Memoir 10: 211-260.

Berggren, W.A., Kent, D.V., Swisher, C.C. and Aubry, M.-P., 1995.  A revised Cenozoic geochronology and chronostratigraphy.  In, .Berggren, W.A., Kent, Aubry, M.-P. and Hardenbol, J. eds., Geochronology, time scales and global stratigraphic correlation.  Tulsa, Society for sedimentary geology special publication 54: 129-212.

Bertolani Marchetti, D., 1975.  Preliminary palynological data on the proposed Plio-Pleistocene boundary type-section of La Castella.  L'Atheneo Parmense Acta Naturalia, 11: 467-485.

Bertolani Marchetti, D., Accosi, C.A., Pelosio, G., and Raffi, S., 1979.  Palynology and stratigraphy of the Plio-Pleistocene sequence of the Stirone River (northern Italy).  Pollen et Spores, 21: 149-167.

Bint, A.N., 1981.  An Early Pliocene Pollen assemblage from Lake Tay, south-western Australia, and its Phytogeographic implications.  Australian Journal of Botany, 29: 277-291.

Bonnefille, R., Vincens, A., and Buchet, G.,  1987.  Palynology, stratigraphy and palaeoenvironment of a Pliocene hominid site (2.9-3.3 M.Y.) at Hadar, Ethiopia.  Palaeogeography, Palaeoclimatology, Palaeoecology, 60: 249-281.

Borisova, O.K., 1991.  Neogene temperature fluctuations on the southeastern Russian Plain. Pliocene Climates of the Northern Hemisphere:   abstracts of the Joint US/USSR Workshop on Pliocene Paleoclimates, Moscow, USSR, April, 1990. U.S. Geological Survey Open-File Report. 91-447:  14-15.

Borisova, O.K., 1994.  Landscape and climate of the south-central and southeastern Russian Plain in the Pliocene.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23: 61-64.

Brouwers, E.M., Jorgensen, N.O. and Cronin, T.M., 1991.  Climatic significance of the ostracode fauna from the Pliocene Kap Kobenhavn Formation, north Greenland.  Miropaleontology 37: 245-276

Brouwers, E.M., 1994.  Late Pliocene paleoecologic reconstructions based on ostracode assemblages from the Sagavanirktok and Gubik Formations, Alaskan North Slope.  Arctic 47(1): 16-33.

Burckle, L.H. and Cirilli, J., 1987.  Origin of diatom ooze belt in the Southern Ocean:  Implications for Late Quaternary paleoceanography.  Micropaleontology 33: 82-86.

Burckle, L.H. and Potter, N., Jr., 1996. Pliocene-Pleistocene diatoms in Paleozoic and Mesozoic sedimentary and igneous rocks from Antarctica: A Sirius problem solved. Geology, 24:235-238.

Burckle, L.H., Stroeven, A.P., Bronge, C., Miller, U., and Wassel, A., 1996.  Deficiencies in the diatom evidence for a Pliocene reduction of the East Antarctic Ice Sheet.  Paleoceanography, 11:379-390.

Caratini, C., and Tissot, C., 1988, Paleogeographical evolution of the Mahakam Delta in Kalimantan, Indonesia during the Quaternary and Late Pliocene.  Review of Palaeobotany and Palynology, 55: 217-228.

Cerling, T. E., J. R. Bowman, J.R., and O'Neil, J.R., 1988.  An isotopic study of a fluvial-lacustrine sequence:  the Plio-Pleistocene Koobi Fora Sequence, East Africa.  Palaeogeography, Palaeoclimatology, Palaeoecology, 63: 335-356.

Cerling, T.E., 1992.  Development of grasslands and savannas in East Africa during the Neogene.  Palaeogeography, Palaeoclimatology, Palaeoecology (Global and Planetary Change Section), 97: 241-247.

Chandler, M., Rind, D. and Thompson, R., 1994.  Joint investigations of the middle Pliocene climate II: GISS GCM Northern Hemisphere results.  Global and Planetary Change 9: 197-219.

Choi, D.K. and Bong, P.Y., 1986.  Neogene palynomorphs from lignite beds of Bugyeong and Yeonghae areas, Korea.  Journal of the Paleontological Society of Korea, 2:  1-17.

Clapperton, C. and Sugden, D.E., 1990.  Late Cenozoic glacial history of the Ross Embayment, Antarctica.  9(2/3): 253-272.

Committee on Glaciology, 1984.  Environment of West Antarctica:  potential CO2-induced changes.  Rep. Workshop held at Madison, Wisconsin, July 1983.  National Academy Press, Washington D.C., 236p.

Cravatte, J., and Suc, J.-P., 1981.  Climatic evolution of North-Western Mediterrean Area during Pliocene and early Pleistocene by Pollen-Analysis and Forams of Drill Autan 1.   Chronostratigraphic correlations.    Pollen et Spores, XXIII(2): 247-258.

Cronin, T.M., 1991a.  Late Neogene marine ostracoda from Tjörnes, Iceland.  Journal of Paleontology 65(5): 767-794.

Cronin, T.M., 1991b.  Pliocene shallow water paleoceanography of the North Atlantic Ocean based on marine ostracodes.  Quaternary Science Reviews 10(2/3): 175-188.

Cronin, T.M., 1999. Principles of Paleoclimatology. New York, Columbia University Press. 1-560.

Cronin, T.M. and Dowsett, H.J., 1990.  A quantitative micropaleontologic method for shallow marine paleoclimatology:  Application to Pliocene deposits of the western North Atlantic Ocean.  Marine Micropaleontology 16(1/2): 117-148.

Cronin, T.M., Kitamura, A., Ikeya, N., Watanabe, M. and Kamiya, T., 1994.  Late Pliocene paleoceanography, Sea of Japan:  The Yabuta Formation.  Palaeogeography, Palaeoclimatology, Palaeoecology 108: 437-455.

Cronin, T.M., Whatley, R.C., Wood, A., Tsukagoshi, A., Ikeya, N., Brouwers, E.M. and Briggs, W.M., 1993.  Microfaunal evidence for elevated mid-Pliocene temperatures in the Arctic Ocean.  Paleoceanography 8: 161-173.

Crowley, T.J., 1996.  Pliocene climates:  the nature of the problem.  Marine Micropaleontology, 27: 3-12.

Crowley, T.J., Yip, K.-J.J. and Baum, S.K., 1994.  Effect of altered Arctic sea ice and Greenland ice sheet cover on the climate of the GENESIS general circulation model.  Global and Planetary Change 9: 275-288.

Denton, G.H., Bockheim, J.G., Wilson, S.C., Leide, J.E. and Andersen, B.G., 1989.  Late Quaternary ice-surface fluctuations of Beardmore Glacier, Transantarctic Mountains.  31: 183-209.

de Vernal, A., and Mudie, P.J., 1989a.  Late Pliocene to Holocene palynostratigraphy at ODP Site 645, Baffin Bay.  Proceedings of the Ocean Drilling Program, Scientific Results, 105: 387-399.

de Vernal, A., and Mudie, P.J., 1989b.  Pliocene and Pleistocene palynostratigraphy at ODP Sites 646 and 647, eastern and southern Labrador Sea.    Proceedings of the Ocean Drilling Program, Scientific Results, 105: 401-422.

Dowsett, H.J., 1989a.  Application of the graphic correlation method to Pliocene marine sequences.  Marine Micropaleontology 14: 3-32.

Dowsett, H.J., 1989b.  Improved dating of the Pliocene of the eastern South Atlantic using graphic correlation:  Implications for paleobiogeography and paleoceanography.  Micropaleontology 35(3): 279-292.

Dowsett, H.J., 1991.  The development of a long-range foraminifer transfer function and application to Late Pleistocene North Atlantic climatic extremes.  Paleoceanography 6(2): 259-273.

Dowsett, H.J., 1996. Middle Pliocene planktonic foraminiferal assemblages from ODP Site 704:  Paleoceanographical implications. In Moguilevsky, A., and Whatley, R., eds., Microfossils and Oceanic Environments, p. 177-186.  Aberystwyth, University of Wales Press.

Dowsett, H., Barron, J., and Poore, R., 1996.  Middle Pliocene sea surface temperatures: a global reconstruction.   Marine Micropaleontology, 27:13-26

Dowsett, H.J. and Cronin, T.M., 1990.  High eustatic sea level during the Middle Pliocene:  Evidence from the southeastern U.S. Atlantic Coastal Plain.  Geology 18: 435-438.

Dowsett, H.J., Cronin, T.M., Poore, R.Z., Thompson, R.S., Whatley, R.C. and Wood, A.M., 1992.  Micropaleontological evidence for increased meridional heat transport in the North Atlantic Ocean during the Pliocene.  Science 258: 1133-1135.

Dowsett, H.J. and Ishman, S.E., 1995.  Middle Pliocene planktic and benthic foraminifers from the sub-Arctic North Pacific:  Sites 883 and 887.  In Rea, D.K., Basov, I.A., Scholl, D.W., and Allan, J.F., eds., Proceedings of the Ocean Drilling Program, Scientific Results, 145: 141-156.  College Station, TX.

Dowsett, H.J. and Loubere, P., 1992.  High resolution Late Pliocene sea-surface temperature record from the Northeast Atlantic Ocean.  Marine Micropaleontology 20: 91-105.

Dowsett, H.J. and Polanco, E.F., 1992.  Pliocene planktic foraminifer census data from Deep Sea Drilling Project Holes 541 and 546.  U.S. Geological Survey Open File Report (92-418), 4p.

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.

Dowsett, H. and Robinson, M., 1998.  Application of the modern analog technique (MAT) of sea surface temperature estimation to middle Pliocene North Pacific planktic foraminifer assemblages.  Paleontologia Electronica, 1(1).   http://www-odp.tamu.edu/paleo/1998_1/dowsett/issue1.htm

Dowsett, H.J., Thompson, R.S., Barron, J.A., Cronin, T.M., Fleming, R.F., Ishman, S.E., Poore, R.Z., Willard, D.A. and Holtz, T.R., 1994.  Joint investigations of the middle Pliocene climate I:  PRISM paleoenvironmental reconstructions.  Global and Planetary Change 9: 169-195.

Dowsett, H.J. and Verardo, S., in prep.  A circum-Antarctic foraminiferal transfer function.  U.S. Geological Survey Open File Report 99-xxx.  Xp.

Dowsett, H.J. and West, S., 1993.  Pliocene planktic foraminifer census data from Deep Sea Drilling Project Hole 445.  U.S. Geological Survey Open File Report (93-307): 5p.

Dowsett, H.J. and Wiggs, L.B., 1992.  Planktonic Foraminiferal assemblage of the Yorktown Formation, USA.  Micropaleontology, 38: 75-86.

Dupont, L. and Leroy, S., 1994.  Steps toward drier climatic conditions in north-western Africa during the upper Pliocene.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23: 44-51.

Edwards, M., 1992. Global Gridded Elevation and Bathymetry, in Kineman, J.J., and Ohrenschall, M.A., eds., Global Ecosystems Database, Version 1.0 (on CD-ROM), Documentation Manual, Disc-A: National Geophysical Data Center, Key to Geophysical Records Documentation No. 26 (Incorporated in:  Global Change Database, Volume 1): Boulder, CO, National Oceanic and Atmospheric Administration, p. A14-1 to A14-4.

Evernden, J.F. and James, G.T., 1964.  Potassium-argon dates and the Tertiary floras of North America.  American Journal of Science, 262: 945-974.

Fleming, R.F., 1992.  Palynological data from Pliocene sediments, DSDP Leg 5 Site 32, Northeastern Pacific Ocean.  U.S. Geological Survey Open-File Report 92-712.  24 pp.

Fleming, R.F., 1994b.  Cretaceous pollen in Pliocene rocks:  implications for Pliocene climate in the southwestern United States.  Geology, 22: 787-790.

Fleming, R.F. and Barron, J.A., 1996.  Evidence of Pliocene Notofagus in Antarctica from Pliocene marine sedimentary deposits (DSDP Site 274).  Marine Micropaleontology, 27: 227-236.

Foley, K.M. and Dowsett, H.J., 1992.  Pliocene planktic foraminifer census data from Ocean Drilling Program Holes 667 and 659A.  U.S. Geological Survey Open File Report (92-434): 6p.

Fradkina, A. F. 1991.  Pliocene climatic fluctuations in the Far North-East of the USSR. Pliocene Climates of the Northern Hemisphere:   abstracts of the Joint US/USSR Workshop on Pliocene Paleoclimates, Moscow, USSR, April, 1990. U.S. Geological Survey Open-File Report 91-447: 22.

Fyles, J.G., Marincovich, L., Matthews, J.V. and Barendregt, R., 1991.  Unique mollusc find in the Beaufort Formation (Pliocene) on Meighen Island, Arctic Canada.  Geologic Survey of Canada, Current Research, Part B 91-1B: 105-112.

Fuji, N., 1988.  Palaeovegetation and palaeoclimate changes around Lake Biwa, Japan during the last ca. 3 Million years.  Quaternary Science Reviews, 7: 21-28.

Gersonde, R., and Burckle, L. H., 1990. Neogene diatom biostratigraphy of ODP Leg 113, Weddell Sea (Antarctic Ocean). In Barker, P. F., Kennett, J. P., et al., Proc. ODP, Sci. Results, 113: College Station, TX (Ocean Drilling Program), 761-789.

Giterman, R. E., Sher, A.V., and Matthews, J.V., Jr., 1982.  Comparison of the development of tundra-steppe environment in west and east Beringia:  pollen and macrofossil evidence from key sections. In:  Paleoecology of Beringia. New York, Academic Press. p. 43-73.

Gladenkov, Y.B., Barinov, K.B., Basilian, A.E., and Cronin, T.M., 1991.  Stratigraphy and Paleoceanography of Pliocene deposits of Karaginsky Island, eastern Kamchatka, U.S.S.R., Quaternary Science Reviews, 10: 239-246.
Graham, A., 1989.  Late Tertiary paleoaltitudes and vegetational zonation in Mexico and Central America.  Acta Bot. Neerl. 38(4): 417-424.

Graham, A., 1994.  Neogene palynofloras and tererestrial paleoenvironments in northern Latin America.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23: 23-30.

Gregor, H.-J., 1990.  Contributions to the Late Neogene and Early Quaternary Floral History of the Mediterrean.  Review of Palaeobotany and Palynology, 62: 309-338.

Grichuk, V. P., 1991.  Vegetation and climate of the middle Akchaghylian (Late Pliocene) on the Russian Plain. Pliocene Climates of the Northern Hemisphere:   abstracts of the Joint US/USSR Workshop on Pliocene Paleoclimates, Moscow, USSR, April, 1990. U.S. Geological Survey Open-File Report 91-447: 26-27.

Groot, J. J., 1991.  Palynological evidence for late Miocene, Pliocene and early Pleistocene climate changes in the middle U.S. Atlantic coastal plain.  Quaternary Science Reviews, 10(2/3): 147-162.

Hansen, J., Russell, G., Rind, D., Stone, P., Lacis, A., Lebedeff, S., Ruedy, R. and Travis, L., 1983.  Efficient three-dimensional global models for climate studies:  models I and II.  Monthly Weather Review, 111: 609-662.

Hays, P.E., Pisias, N.G. and Roelofs, A.K., 1989.  Paleoceanography of the eastern equatorial Pacific during the Pliocene:  A high resolution study.  Paleoceanography 4: 57-73.

Haywood, A.M., Valdes, P.J. and Sellwood, B.W., 1999. Palaeoclimate reconstruction of the Middle-Pliocene Climate using the UKMO GCM:  Report submitted to the USGS PRISM Group September, 1999. The University of Reading, UK.

Haq, B. H., Hardenbol, J. and Vail, P. R., 1987a.  Chronology of fluctuating sea levels since the Triassic:  Science, 235: 1156-1167.

Haq, B.U., Hardenbol, J. and Vail, P.R., 1987b. The new chronostratigraphic basis of Cenozoic and Mesozoic sea level cycles. Cush. Found. Foram. Res., Spec. Pub., 24: 7-13.

Harwood, D.M., 1986.  Diatom biostratigraphy and paleoecology with a Cenozoic history of antarctic ice sheets. Ph.D. Dissertation, Ohio State Univ., Columbus, OH, 592 pp.

Heusser, L.E., 1981.  Pollen analysis of selected samples from Deep Sea Drilling Project Leg 63.  In:  Yeats, R.S., Haq, B.U., et al. (Editors), Initial Reports of the Deep Sea Drilling Project, 28.   U.S. Government Printing Office, Washington, D.C. p. 559-563.

Hill, R.S., and Macphail, M.K., 1985.  A fossil flora from rafted Plio-Pleistocene mudstones at Regatta Point, Tasmania.  Australian Journal of Botany, 33: 497-517.

Hodell, D.A. and Ciesielski, P.F., 1991.  Stable isotopic and carbonate stratigraphy of the Plio-Pleistocene of Ocean Drilling Program (ODP) Hole 704A:  Eastern subantarctic South Atlantic.  Proceedings of the Ocean Drilling Program, Scientific Results, 114: 409-436.

Hodell, D.A. and Venz, K., 1992.  Toward a high-resolution stable isotopic record of the Southern Ocean during the Pliocene-Pleistocene (4.8 to 0.8 Ma).  Antarctic Research Series 56: 265-310.

Hooghiemstra, H., 1994a.  Pliocene-Quaternary floral migration, evolution of Northern Andean ecosystems and climatic change:  implications from the closure of the Panamanian Isthmus.  Profil, 7:  413-425.

Hooghiemstra, H., 1994b.  Paleoclimatic conditions around 3 million year BP:  pollen evidence from Colombia.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23: 31-37.

Hooghiemstra, H., and Sarmiento, G., 1991.  Long continental pollen record from a tropical intermontane basin:  Late Pliocene and Pleistocene history from a 540-meter core.  Episodes 14:. 107-115

Horowitz, A., 1989.  Continuous pollen diagrams for the last 3.5 M.Y. from Israel:  vegetation, climate and correlation with the oxygen isotope record.  Palaeogeography, Palaeoclimatology, Palaeoecology, 72: 63-78.

Horowitz, A., and Horowitz, M., 1985.  Subsurface late Cenozoic palynostratigraphy of the Hula basin, Israel.  Pollen et Spores, 27(3-4): 365-390.

Hsü, J., 1983.  Late Cretaceous and Cenozoic vegetation in China, emphasizing their connections with North America.  Annals of the Missouri Botanical Garden, 70:  490-508.

Hughes, T. J., 1981. The weak underbelly of the West Antarctic Ice Sheet. Journal of Glaciology, 27: 518-525.

Hunt, C. O., 1989.  The palynology and correlation of the Walton Crag (Red Crag Formation, Pliocene).  Journal of the Geological Society, London, 146: 743-745.

IPCC, 1995.  Climate Change 1995:  Impacts, Adaptations and Mitigation of Climate Change:  Scientific-Technical Analyses.  Watson, R.T., Zinyowera, M.C., and Moss, R.H., (Eds.), Cambridge University Press, Cambridge, 879 p.

Igarashi, Y., Yoshida, M., and Tabata, H., 1988.  History of vegetation and climate in the Kathmandu Valley.  In:  Jain, D.V.S., Agrawal, D.P., Sharma, P., and Gupta, S.K. (Editors), Palaeoclimatic and palaeoenvironmental changes in Asia during the last 4 million years.  Indian National Science Academy, pp. 212-225.

Ikeya, N. and Cronin, T., 1993.  Quantitative analysis of ostracoda and water masses around Japan:  application to Pliocene and Pleistocene paleoceanography.  Micropaleontology 39: 263-281.

Jansen, E., Sjoholm, J., Bleil, U., and Erichsen, J.A., 1990.  Neogene and Pleistocene glaciations in the northern hemisphere and late Miocene-Pliocene global ice volume fluctuations:  Evidence from the Norwegian sea.  In, Bleil, U. and Theide, J., (Editors), Geologic History of the Polar Oceans:  Arctic vs Antarctic, pp. 677-705, Kluwer, Amsterdam.

Jenkins, D.G., 1992a.  The paleogeography, evolution and extinction of Late Miocene-Pleistocene planktonic foraminifera from the southwest Pacific:  In, Ishizaki, K. and Saito, T., (Editors), Centenary of Japanese Micopaleontology, Terra Scientific Publishing Company, Tokyo, 27-35.

Jenkins, D.G., 1992.  Predicting extinctions of some extant planktic foraminifera.  Marine Micropaleontology 19: 239-243.

Kedves, M., 1984.  Étude palynologique d'un lignite Tertiaire de Blao, Viet-Nam -1-.  Acta Biol. Szeged., 30: 91-105.

Keller, G., 1978.  Late Neogene biostratigraphy and paleoceanography of DSDP Site 310 Central North Pacific and correlation with the Southwest Pacific.  Marine Micropaleontology, 3: 97-119.

Kennett, J.P. and Hodell, D.A., 1993.  Evidence for relative climatic stability of Antarctica during the early Pliocene:  A marine perspective.  Geografiska Annaler 75: 205-220.

Khan, A. M., 1974.  Palynology of Neogene sediments from Papua (New Guinea) stratigraphic boundaries.  Pollen et Spores, 16: 265-284.

Koizumi. I., 1985. Late Neogene paleoceanography in the western North Pacific.  In: Heath, G.R., Burckle, L.H., et al. (Editors), Initial Reports of the Deep Sea Drilling Project, vol. 86.  U.S. Govt. Printing Office, Washington, D.C., pp. 429-438.

Krantz, D.E., 1991.  A chronology of Pliocene sea level fluctuations:  The U.S. middle Atlantic Coastal Plain record.  Quaternary Science Reviews 10: 163-174.

Lagoe, M.B., Eyles, C.H., Eyles, N., and Hale, C., 1993.  Timing of late Cenozoic tidewater glaciation in the far North Pacific.  Geol. Soc. Am. Bull., 105:1542-1560.

Leopold, E. B. and Wright, V. C., 1985.  Pollen profiles of the Plio-Pleistocene transition in the Snake River Plain, Idaho. Late Cenozoic history of the Pacific Northwest.  American Association for the Advancement of Science, Pacific Division. Pp. 323-348.

Leroy, Suzanne, and Dupont, Lydie, 1994.  Development of vegetation and continental aridity in northwestern Africa during the Late Pliocene:  the pollen record of ODP Site 658.  Palaeogeography, Palaeoclimatology, Palaeoecology, 109: 295-316.

Litwin, R. J., and Andrle, V. A. S., 1992a.  Modern palynomorph and weather census data from the U.S. Atlantic Coast (Continental Margin Program samples and selected NOAA weather stations).  U.S. Geological Survey Open-File Report 92-263.  31 p.

Mackensen, A., 1992.  Neogene benthic foraminifers from the Southern Indian Ocean (Kerguelen Plateau): biostratigraphy and paleoecology. In: Wise, S.W., Jr., Schlich, R., et al., Proceedings Ocean Drilling Program, Scientific Results, vo. 120.  Ocean Drilling Program, College Station, TX, pp. 649-673.

Mamedov, A. V., 1991.  The paleogeography of the Trans-Caucasus Region during the Pliocene climatic optimum. Pliocene Climates of the Northern Hemisphere:   abstracts of the Joint US/USSR Workshop on Pliocene Paleoclimates, Moscow, USSR, April, 1990. U.S. Geological Survey Open-File Report 91-447: 28-31.

Marchant, D.R. and Denton, G.H., 1996.  Miocene and Pliocene paleoclimate of the Dry Valleys region, Southern Victoria land:  a geomorphological approach.  Marine Micropaleontology, 27: 253-271.

Matthews, E. 1985.  Prescription of land-surface boundary conditions in GISS GCM II:  a simple method based on high-resolution vegetation data bases.  NASA Report No. TM 86096 : 20 p.

Matthews, J. V., Jr., 1987.  Plant macrofossils from the Neogene Beaufort Formation on Banks and Meighen Islands, District of Franklin.  Current Research, Part A, Geological Survey of Canada, Paper 87-1A : 73-87.

Matthews, J. V., Jr., 1990.  New data on Pliocene floras/faunas from the Canadian Arctic and Greenland. Pliocene climates:  scenario for global warming.  Abstracts from USGS workshop, Denver, Colorado, October 23-25, 1989. Washington, D.C., U.S. Geological Survey Open-File Report 90-64: 29-33.

Matthews, J.V., Jr. and Ovenden, L.E., 1990.  Late Tertiary plant macrofossils from localities in Arctic/Subarctic North America: a review of the data. Arctic, 43: 364-392.

Meier, M.F., 1985.  Mass balance of the glaciers and small ice caps of the world. In Meier, M.F. et al. (Editors), Glaciers, Ice Sheets, and Sea Level: Effect of a CO2-Induced Climatic Change, 139-144, DOE/EV/60235-1: 139-144.

Mercer, J. H., 1978. West Antarctic Ice Sheet and CO2 greenhouse effect: A threat of disaster. Nature, 271: 321-325.

Mildenhall, D.C., and Harris, W.F., 1970.  A cool climate pollen assemblage from the type Waipipian (Middle Pliocene) of New Zealand.  New Zealand Journal of Geology and Geophysics, 13:  586-591.

Mildenhall, D.C., and Pocknall, D.T., 1983.  Palaeobotanical evidence for changes in Miocene and Pliocene climates in new Zealand.  in  Vogel, J.C., ed., Late Cainozoic Palaeoclimates of the Southern Hemisphere.  Rotterdam:  A.A. Balkema, pp. 159-171.

Mildenhall, D.C., and Suggate, R.P., 1981, Palynology and age of the Tadmor Group (Late Miocene-Pliocene) and Porika Formation (early Pleistocene), South Island, New Zealand.  New Zealand Journal of Geology and Geophysics, 24: 515-528

Mohr, B. A. R., 1986.  Die Mikroflora der Oberpliozänen tone Von Willershausen (Kreis Northeim, Niedersachsen).  Palaeontographica, Abt. B. 198: 133-156.

Nelson, R. E., and Carter, L. D., 1985.  Pollen analysis of a late Pliocene and early Pleistocene section from the Gubik Formation of arctic Alaska.  Quaternary Research, 24: 295-306.

Nelson, C.S., Mildenhall, D.C., Todd, A.J., Pocknall, D.T., 1988.  Subsurface stratigraphy, paleoenvironments, palynology, and depositional history of the late Neogene Tauranga Group at Ohinewai, Lower Waikato Lowland, South Auckland, New Zealand Journal of Geology and Geophysics, 31: 21-40

Oerlemans, J., 1982.  Response of the Antarctic ice sheet to a climatic warming: a model study. Journal of Climatology, 2: 1-11.

Oerlemans, J. and van der Veen, C. J., 1984.  Ice Sheets and Climate.  D. Reidel Publishing:  Dordrecht, 217 pp.

Oglesby, R. J., 1989.  A GCM study of Antarctic glaciation.  Climate Dynamics, 3:135-156.

Partridge, T.C., Wood, B.A., and deMenocal, P.B., in press, Influence of global climatic change and regional uplift on large mammal evolution in east and southern Africa.  In:  Vrba, E.S., Denton, G.H., Burckle, L.H., and Partridge, T.C. (Editors), Paleoclimate and evolution with emphasis on human origins.  Yale University Press, New Haven.

Planderová, E., 1974.  The problem of the floristic boundary between Pliocene-Pleistocene in Western Carpathians mounts on the basis of palynological examination.  Bureau de Recherches Geologiques et Minieres, Memoires, 78(2): 547-551.

Poore, R.Z., 1999.  Mid-Pliocene planktic foraminifers and environmental estimates DSDP Site 36.  In, The Pliocene:  Time of Change, Wren, J.H. Suc, J.-P., and Leroy, S., (ed.), American Association of Stratigraphic Palynologists Special Publication XX, p. 198-208.

Poore, R.Z., Phillips, L., Schneider, D., and Ishman, S.E., 1994.  Pliocene of Northwind Ridge, Western Arctic Ocean.  In, Ishman, S.E.(ed.), Pliocene High Latitude Climate Records.  U.S. Geological Survey Open File Report 94-0603: 21-22a.

Poore, R.Z. and Sloan, L.C., 1996.  Climates and Climate Variability of the Pliocene, Eds.  Marine Micropaleontology, 27: 326p.

Prell, W.L., 1985. The stability of low-latitude sea-surface temperatures:  An evaluation of the CLIMAP reconstruction with emphasis on the positive SST anomalies. Washington, D. C., Dep. of Energy.

PRISM Project Members, 1994.  PRISM 8° x 10° Northern Hemisphere paleoclimate reconstruction:  Digital data.  U.S. Geological Survey Open File Report 94-281: 23 p.

PRISM Project Members, 1996.  Pliocene planktic foraminifer census data from the North Atlantic region.  U.S. Geological Survey Open File Report 96-669: 30 p.

Quade, J.,  Cerling, T.E., and Bowman, J.R., 1989.  Development of Asian Monsoon revealed by marked ecological shift during the latest Miocene in northern Pakistan.  Nature, 342: 163-166.

Raymo, M.E., Ruddiman, W.F., Backman, J., Clement, B.M. and Martinson, D.G., 1989.  Late Pliocene variation in Northern Hemisphere ice sheets and North Atlantic deep water circulation.  Paleoceanography 4(4): 413-446.

Robinson, M.M. and Dowsett, H.J., 1996.  Pliocene planktic foraminifer census data from DSDP Site 592, Southwestern Pacific Ocean. .  U.S. Geological Survey Open-File Report 96-544, 6p.

Rousseau, D.-D., Taoufiq, N.B., Petit, C., Farjanel, G., Méon, H., and Puisségur, J.-J., 1992.  Continental late Pliocene paleoclimatic history recorded in the Bresse Basin (France).  Palaegeography, Palaeoclimatology, Palaeoecology, 95: 253-261.

Reynolds, R.W. and Smith, T.M., 1995.  A high resolution global sea surface temperature climatology.  Journal of Climatology, 8: 1571-1583.

Sancetta, C. and Silvestri, S., 1986.  High-resolution biostratigraphic and oceanographic events in the late Pliocene and Pleistocene North Pacific Ocean.  Paleoceanography 1(2): 163-180.

Schwarzbach, M. and Pflug, H. D., 1957.  Das klima des jüngeren Tertiärs in Island.    Neues Jahrbuch Geologie und Paläontologie, 104: 279-298.

Schweitzer, P. N. 1995.  Monthly averaged polar sea-ice concentration.  U.S. Geological Survey Digital Data Series: Virginia, Ed 1. DDS-27.

Scott, L. and Partridge, T.C., 1994.  Some manifestations of Pliocene warming in southern Africa.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23: 54-55.

Shackleton, N.J., Hall, M.A., and Pate, D., 1995.  Pliocene stable isotope stratigraphy of Site 846.  In Pisias, N.G., Mayer, L.A., Janecsek, T.R., et al., Proc. ODP, Sci. Results, 138.  College Station, TX (Ocean Drilling Program), p. 337-355.

Shatilova, I. I., 1980.  Palynolgic study of late Cainozoic and modern deposits in the eastern part of the Black Sea area. IV International Palynological Conference, Lucknow, India.

Shatilova, I. I., 1986.  The palynological base of stratigraphical subdivision of late Cainozoic deposits of the western Transcaucasus.  Review of Palaeobotany and Palynology, 48: 409-414.

Shatilova, I. I., Macharadze, N. V., and Davitashivilli, L.S., 1991. The Pliocene Climate of western Georgia. Pliocene Climates of the Northern Hemisphere:   abstracts of the Joint US/USSR Workshop on Pliocene Paleoclimates, Moscow, USSR, April, 1990. U.S. Geological Survey Open-File Report 91-447: 35-37.

Shipboard Scientific Party, 1994.  Initial Reports, East Greenland Margin.  Proceedings of the Ocean Drilling Program, 152.

Sloan, L.C., Crowley, T.J. and Pollard, D., 1996.  Modelling of middle Pliocene climate with the NCAR GENESIS general circulation model.  Marine Micropaleontology, 27:  51-61.

Spaak, P., 1983.  Accuracy in correlation and ecological aspects of the planktonic foraminiferal zonation of the Mediterranean Pliocene.  Utrecht Micropaleontological Bulletins 28: 159 pp.

Stroeven, A.P. and Prentice, M.L., 1997. A case for Sirius Group alpine glaciation at Mount Fleming, South Victoria Land, Antaforca: A case against Pliocene East Antarctic Ice Sheet reduction.  Geol. Soc. Am. Bull., 109(7):825-840.

Stuchlik, L., and Shatilova, I. I., 1987.  Palynological study of Neogene Deposits of southern Poland and western Georgia.  Acta Palaeobotanica, 27(2): 21-52.

Suc, J.-P., 1984.  Origin and evolution of the Mediterreanean vegetation and climate in Europe.  Nature, 307: 429-432.

Suc, J.-P., and Zagwijn, W.H., 1983.  Plio-Pleistocene correlations between the northwestern Mediterrean region and northwestern Europe according to recent biostratigraphic and palaeoclimatic data.  Boreas, 12: 153-166.

Svetlitskaya, T.V., 1994.  Landscape and climate of the southwestern Russian Plain in the Pliocene.  In:  Thompson, R.S. (Editor), Pliocene terrestrial environments and data/model comparisons.  U.S. Geological Survey Open-File Report 94-23, p. 56-60.

Thompson, R.S., 1991.  Pliocene environments and climates in the western United States.  Quaternary Science Reviews, 10(2/3): 115-132.

Thompson, R.S., 1992.  Palynological data from a 989-ft. (301-m) core of Pliocene and Pleistocene sediments from Bruneau, Idaho.  U.S. Geological Survey Open-File Report 92-713.  28 pp.

Thompson, R.S., 1996. Pliocene and early Pleistocene environments and climates of the western Snake River Plain, Idaho. Marine Micropaleontology, 27(1/4): 141-156.

Thompson, R.S. and Fleming, R.F., 1996.  Middle Pliocene vegetation:  reconstructions, paleoclimatic inferences, and boundary conditions for climatic modeling.  Marine Micropaleontology, 27(1/4):  13-26.

Thompson, R.S., Oviatt, C.G., Roberts, A.P., Buchner, J., Kelsey, R., Bracht, C., Forester, R.M., and Bradbury, J.P., 1995.  Stratigraphy, sedimentology, paleontology, and paleomagnetism of Pliocene-early Pleistocene lacustrine deposits in two cores from western Utah.  U.S. Geological Survey Open-File Report 95-1.  94 pp.

Thunell, R.C., 1979a.  Climatic evolution of the Mediterranean Sea during the last 5.0 million years.  Sedimentary Geology 23: 67-79.

Thunell, R.C., 1979b.  Pliocene-Pleistocene paleotemperature and paleosalinity history of the Mediterranean Sea:  Results from DSDP Sites 125 and 132.  Marine Micropaleontology 4: 173-187.

Thunell, R.C., 1991.  An overview of the Post-Messinian paleoenvironmental history of the western Mediterranean.  Paleoceanography 6(1): 143-164.

Tiedmann, R., Sarnthein, M., and Schackleton, N.J., 1994.  Astronomic timescale for the Pliocene d18O and dust records of Ocean Drilling Program Site 659.  Paleoceanography, 9(4):619-638.

Traverse, A., 1982.  Response of world vegetation to Neogene tectonic and climatic events.  Alcheringa, 6: 197-209.

Turnbull, I.M., Lindqvist, J.K., Mildenhall, D.C., Hornibrook, N. de B., and Beu, A.B., 1985.  Stratigraphy and paleontology of Pliocene-Pleistocene sediments on Five Fingers Peninsula, Dusky Sound, Fiordland.  New Zealand Journal of Geology and Geophysics, 28: 217-231

Van de Weerd, Anne, 1983.  Palynology of some upper Miocene and Pliocene formations in Greece.  Geologisches Jahrbuch, 48: 3-63.

Van der Hammen, T.  1985.  The Plio-Pleistocene climatic record of the tropical Andes.  J. Geol. Soc. London, 142: 483-489.

Volkova, V. S., 1991.  Pliocene climates of west Siberia. Pliocene Climates of the Northern Hemisphere:   abstracts of the Joint US/USSR Workshop on Pliocene Paleoclimates, Moscow, USSR, April, 1990. U.S. Geological Survey Open-File Report 91-447: 44-45.

Wardlaw, B.R. and Quinn, T.M., 1991.  The record of Pliocene sea-level change at Enewetak Atoll.  Quaternary Science Reviews 10(2/3): 247-258.

Webb, P.-N. and Harwood, D.M., 1991.  Late Cenozoic glacial history of the Ross Embayment, Antarctica.  Quaternary Science Reviews 10: 215-223.

Webb, P.-N. and Harwood, D.M., 1993.  Pliocene fossil Nothofagus (southern beech) from Antarctica:  phytogeography, dispersal strategies, and survival in high latitude glacial-deglacial environments.  In:  Alden, J. et al. (eds.), Forest Development in Cold Climates.  Plenum Press, New York.  pp. 135-165.

Webb, P.-N., Harwood, D.M.,  Mabin, M.G.C., and McKelvey, B.C., 1996.  A marine and terrestrial Sirius group succession, middle Beardmore Glacier - Queen Alexandra range, transanarctic Mountains, Antarctica.  Marine Micropaleontology, 27:273-297.

Webb, P.-N., Harwood, D.M., McKelvey, B.C., Mercer, J.H.  and Stott, L.D., 1984.  Cenozoic marine sedimentation and ice-volume variation on the East Antarctic craton.  Geology, 12, 287-291.

Wijninga, V.M. and Kuhry, P., 1990.  A Pliocene flora from the Subachoque Valley (Cordillera Oriental, Colombia).  Review of Palaeobotany and Palynology, 62: 249-290.

Willard, D. A., 1992.  Late Pliocene pollen assemblages from Ocean Drilling Project Hole 646B:  census data and paleoclimatic estimates.  U.S. Geological Survey Open-File Report 92-405.  12 pp.

Willard, D.A., 1994.  Palynological record from the North Atlantic region at 3 Ma: vegetational distribution during a period of global warmth.  Review of Paleobotany and Palynology, 83: 275-297.

Willard, D.A., Cronin, T.M., Ishman, S.E., and Litwin, R.J., 1993.  Terrestrial and marine records of climate and environmental change during the Pliocene in subtropical Florida.  Geology, 21: 679-682.

Williamson, P. G., 1985.  Evidence for an early Plio-Pleistocene rainforest expansion in East Africa.  Nature, 315: 487-489.

Wilson, G.S., 1993.  Ice induced sea level change in the late Neogene.  Victoria University, Wellington.

Wolfe, J.A., 1990.  Estimates of Pliocene preciptiation and temperature based on multivariate analysis of leaf physiognomy.  In:  Gosnell, L.B. and Poore, R.Z. (eds.), Pliocene climates:  scenario for global warming.  U.S. Geological Survey Open-File Report 90-64: 39-42.

Wood, A., Whatley, R.C., Cronin, T.M. and Holtz, T., 1993.  Pliocene paleotemperature recombination for the southern North Sea based on Ostracoda:  A review.  Quaternary Science Reviews 12(9): 747-767.

Zagwijn, W. H., 1992.  The beginning of the Ice Age in Europe and its major subdivisions.  Quaternary Science Reviews, 11: 583-591.

Zalasiewicz, J. A., Mathers, S. J. , Hughes, M.J., Gibbard, P.L., Peglar, S.M., Harland, R., Nicholson, R.A., Boulton, G.S., Cambridge, P., and Wealthall, G.P., 1988.  Stratigraphy and palaeoenvironments of the Red Crag and Norwich Crag formations between Aldeburgh and Sizewell, Suffolk, England.  Philosophical Transactions of the Royal Society of London, B.  Biological Sciences, 322: 221-272.

Zarate, M.A., and Fasana, J.L., 1989.  The Plio-Pleistocene record of the central eastern Pampas, Buenos Aires, Province, Argentina:  the Chapadmalal Case Study.  Palaeogeography, Palaeoclimatology, Palaeoecology, 72: 27-52.

Zhou, Z., Zhao, J., and Yin, P., 1989.  Characteristics and tectonic evolution of the East China Sea.  In: Zhu, X. (editor), Chinese Sedimentary Basins.  Elsevier Science Publishers, Amsterdam.  pp. 165-179.

Zielinski, U. and Gersonde, R., 1997. Diatom distribution in Southern Ocean surface sediments: Implications for paleoenvironmental reconstructions.  Palaeogeography, Palaeoclimatology, Palaeoecology, 129:213-250.

8.  Appendices

Only Appendices 2, 4 and 5 are included with hard copy version of this report to save space.  All data can be derived from these appendices.  All appendices are stored in Microsoft® EXCEL or ASCII TEXT format.  These files are available at  http://geology.er.usgs.gov/eespteam/prism/prism_data.html  or by contacting  Harry Dowsett.
Appendix 1.  PRISM2.LAND

2x2 global grid showing ocean cells as "0",  land cells as "1", and land cells covered by land ice as "9".  Based upon a +25m sea level.

Appendices 2.1 - 2.12.  PRISM2.SST

subdirectory contains 12 2x2 global grids with estimated average monthly pliocene sea surface temperatures.  Sea ice is designated as -1.8 degrees C.  Land cells are designated with -999.

Appendices 3.1 - 3.12.PRISM2.SEAICE

subdirectory contains 12 2x2 global grids with estimated average monthly pliocene sea ice distributions.  Sea ice is designated as "1", land cells as '8' and  water cells as '0.'  This information can alternatively be extracted from the 12 SST grids descibed in Appendix 2.

Appendix 4. PRISM2.TOPO

2x2 global grid showing Pliocene topography  in meters above sea level.

Appendix 5.  PRISM2.VEG

2x2 global grid showing Pliocene vegetation cover using the following categories:  0-water, 1-desert,  2-tundra, 3-grassland, 6-deciduous forest, 7-coniferous forest, 8-rainforest, 9-land ice.

Appendices 6.1 - 6.7  MODERN.DATA

subdirectory contains assorted modern data including SST (6.1 & 6.2), vegetation (6.3), and topography (6.4).  Other modern data can be derived from these appendices.

Approved for publication October 26, 1999

This site is https://pubs.usgs.gov/openfile/of99-535/
Maintained by the Eastern Publications Group Web Team
Last revised 07-08-08