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U.S. Geological Survey Open-File Report OF 03-008

Gulf of Mexico Planktic Foraminifer Core-top Calibration Data Set:  Raw Data

By Harry J. Dowsett[1], Charlotte A. Brunner[2], Stacey Verardo1, and Richard Z. Poore1

INTRODUCTION AND BACKGROUND

Paleoceanographers use the distribution of planktic foraminifers in sediment samples to estimate past oceanographic and paleoclimatic conditions (see Murray, 1995 for review).  Analysis of climate and environmental variability on the decadal to millenial scale requires a taxonomically stable and well-dated core-top calibration data set.  Databases used in global reconstructions of the last glacial maximum (Cline and Hays, 1976; CLIMAP, 1976; 1981), last interglacial (CLIMAP, 1984), and middle Pliocene (Dowsett et al., 1999) do not always meet these requirements.  In this report we present planktic foraminifer faunal census data and AMS 14C data which can be be used in investigations of climate variability in the Gulf of Mexico region (eg. Poore et al., in review). More comprehensive interpretation and analysis of these data, aimed at developing a temporally and taxonomically stable data set will follow in other publications (see Dowsett et al., 2002).

MATERIALS & METHODS

Core-top samples included in this report were originally retreived during Gulf of Mexico cruises of the RV Vema and RV Robert Conrad (Lamont Doherty Earth Observatory, LDEO), RV Trident (University of Rhode Island, URI), RV Gyre (Texas A&M University, TAMU), RV Knorr (Woods Hole Oceanographic Institute, WHOI), RV Ida Green (University of Texas Marine Science Institute) and the RV Marion-Dufresne (French Polar Institute),  dating as far back as 1954.   Samples are from piston cores, trigger weight cores or gravity cores. Core sites selected for this study represent a range of depth and environment and are distributed througout the Gulf of Mexico (Figure 1 and Appendix 1).

The faunal data assembled here are a combination of planktic foraminifer counts from Gulf of Mexico core-top samples processed by the U.S. Geological Survey (USGS), URI, and Brown University (under the direction of Nilva Kipp).  The processing technique is standard but differences between the labs are noted below.   Additional information regarding methodology can be found in Imbrie & Kipp (1971), Brunner and Cooley (1976), Brunner (1979, 1982), and Dowsett & Poore (2001).  Careful attention was paid to the taxonomic concepts of the various authors so that the resulting data set is internally taxonomically-consistent.

Raw samples aquired by the USGS were processed by first oven drying (<=50°C) and then soaking in dilute Calgon or H2O2 solution for several hours to disaggregate the sediment.  Disaggregated sediment was washed through a 63Ám mesh and oven dried at <=50°C.  Dry residue was then dry-sieved at 150Ám with the >150Ám fraction reserved for faunal analysis.  When necessary (>300 individuals in the >150Ám fraction) samples were split using a CARPCO or OTTO microsplitter to obtain a representative sample of 300 specimens.  Next (for samples analyzed at the USGS), individuals were fixed on a standard 60-square micropaleontological slide based upon their designation as species.  Samples analyzed at URI were counted directly from a strew on a tray.

Distribution of samples within the Gulf of Mexico displayed on January 2001 mean sea-surface temperature (SST) ma

Figure 1.  Distribution of samples within the Gulf of Mexico displayed on January 2001 mean sea-surface temperature (SST) map.  Orange colors represent warmest SST and highlite the advection of warm water into the Gulf of Mexico from the Caribbean and the position of the Loop Current. (SST map provided by Space Oceanography Group, Johns Hopkins University Applied Physics Laboratory)

FAUNAL DATA

The taxonomies of Parker (1962, 1967), Blow (1969), Kennett and Srinivasan (1983), and informal notes of Nilva Kipp, were employed for identification. Faunal census data are reported here using  the following taxonomic categories:

Orbulina universa d'Orbigny

Globigerinoides conglobatus (Brady)           

Globigerinoides ruber (d'Orbigny).  White and pink varieties of this species are tallied together.

Globigerinoides tenellus Parker       

Globigerinoides sacculifer (Brady).  We include in this category specimens assignable to Globigerinoides quadrilobatus (d'Orbigny) and Globigerinoides trilobus (Reuss). 

Sphaeroidinella dehiscens (Parker & Jones)

Globigerinella aequilateralis (Brady)

Globigerinella calida (Parker)           

Globigerina bulloides d'Orbigny     

Globigerina falconensis Blow

Globigerina digitata Brady

Globigerina rubescens Hofker        

Turborotalita quinqueloba (Natland)

Neogloboquadrina pachyderma (Ehrenberg).  Right and left coiling varieties are counted separately in this report.      

Neogloboquadrina dutertrei (d'Orbigny)

Globorotaloides hexagona (Natland)

Pulleniatina obliquiloculata Parker & Jones

Globorotalia inflata (d'Orbigny)

Globorotalia truncatulinoides (d'Orbigny). Right and left coiling varieties are counted separately in this report.      

Globorotalia crassaformis (Galloway & Wissler)

Neogloboquadrina pachyderma - Neogloboquadrina dutertrei (P - D ) intergrade.  Specimens of right-coiling Neogloboquadrina with more than four chambers in the final whorl, transitional between Neogloboquadrina pachyderma (Ehrenberg) and Neogloboquadrina dutertrei (d'Orbigny). 

Globorotalia hirsuta (d'Orbigny)

Globorotalia scitula (Brady)

Globorotalia menardii (Parker, Jones, and Brady) s.l.  Our Gl. menardii complex includes

Gl. menardii, Globorotalia tumida (Brady) s.l. and Globorotalia ungulata Bermudez.

Candeina nitida d'Orbigny  

Globigerinita glutinata (Egger) s.l.

Hastigerina pelagica (d'Orbigny)    

Other.  Unidentified specimens or specimens that are rare within the Gulf of Mexico assemblages.

Raw counts of planktic foraminifers in each of 135 samples  are provided in Appendix 1.

AMS 14C DATA

Archival core-top material from many of the cores shown on Figure 1 and listed in Appendix 1, is no longer available.  Therefore, direct dating of core-top assemblages is for the most part, impossible.  In many cases, we were able to obtain samples close to the core-top and estimate core-top ages by extrapolation.   Several numerical techniques were devised to determine the probability of assemblages representing "modern" core-top conditions and will be discussed elsewhere (see also Dowsett et al., 2002).

Samples selected for Accelerator Mass Spectrometry (AMS) 14C dating were processed as indicated above.  Unless indicated otherwise (Table 1), dates were obtained from mixed planktic foraminifers hand picked from the >150Ám washed residue.  Graphite targets for AMS dating were made at the USGS in Reston, Virginia.  The carbon from these samples was captured as CO2 by acidification of the entire sample with 85% phosphoric acid (H2PO4) in a vacuum chamber.  The COwas then dried by forcing the gas through a bath cooled (using alcohol and dry ice) to approximately -80°C.  The dried CO2 was converted to pure carbon in the form of graphite by placing a measured volume (equivalent to 1mg carbon) in a chamber with iron powder, hydrogen, and zinc as a catalyst at 575°C for ten hours.  The sample carbon (precipitated on the iron) was pressed into aluminum targets for AMS analysis. 

Dating was done at the Lawrence Livermore Laboratory Center for Accelerator Mass Spectrometry (CAMS) in Livermore, CA (Roberts et al., 1997).  Ages were reported in radiocarbon years (BP) using the Libby half-life of 5568 years.  AMS 14C dates were converted to calendar years (BP) by calibration to the INTCAL98 database (Stuiver et al., 1998) and a estimated marine reservoir correction of 400 years.

Table 1 lists results of AMS 14C dating.  An initial analysis of some of the data presented here can be found in Dowsett et al. (2002).

Table 1.  AMS 14C  results.  Samples composed of mixed planktics unless otherwise noted.

Core Interval (cm) Age (BP)a ▒(Yrs) CalYr (BP)b,c Comments
RC09-17 8-10 1595 40 725  
RC09-17 20 4210 45 3736  
RC10-262 10-12 2930 40 2176  
RC10-262 30-32 7100 35 7235  
RC10-262TW 0-1 3515 35 2870  
RC10-263 9-11 3500 30 2856  
RC10-263 34-36 6270 30 6279  
RC10-264 17-19 18185 50 20570  
RC10-264 38-40 27640 120 -- Too old to be converted
RC10-265 15-17 1855 40 981  
RC10-265 34-36 4590 40 4266  
RC10-268 13-15 2950 40 2246  
RC10-268 34-36 4740 35 4443  
RC10-270 10-12 3295 40 2702  
RC10-270 31-33 3085 40 2343  
RC12-09 15-17 2290 30 1417  
RC12-09 36-38 3815 30 3306  
RC12-05 10-12 2435 40 1593  
RC12-05 30-32 3700 40 3150  
RC12-07 18-20 1455 40 633  
RC12-07 37-39 2635 40 1832  
RC12-07TW 0-1 1680 35 824  
RC12-10 0-2 940 35 167  
RC12-10 16-18 1390 30 557  
RC12-10 50-51 3185 60 2489  
RC12-10 100-101 5325 60 5276  
RC12-10 134-136 6985 50 7139  
RC12-10 172-174 9350 40 9528  
RC12-10 210-212 12085 45 13153  
RC12-10 254-256 15710 45 17722  
RC12-11 50-51 5470 200 5442  
RC12-11 100-101 9595 75 9826  
RC12-11TW 0-1 1280 35 500  
VM03-32 18-20 6255 40 6272  
VM03-32 108-110 9395 40 9613  
VM03-35 8-10 4080 35 3584  
VM03-42 10-12 6325 40 6311  
VM03-42 46-48 4835 30 4574  
VM03-45 10-12 6400 40 6402  
VM03-45 35-37 9630 35 9835  
VM03-49 39-41 8845 50 8932  
VM03-49 89-91 3875 40 3351  
VM03-69 47-48 3430 65 2774  
VM03-69 97-98 5460 120 5437  
VM03-96 15 1755 40 910  
VM03-96 30 3955 40 3438  
VM03-123 5 9465 40 9786  
VM03-123 23 26590 90 -- Too old to be converted
VM03-146 8-10 22580 70 -- Too old to be converted
VM03-146 30-32 32430 160 -- Too old to be converted
VM24-22 9-11 1880 35 1030  
VM24-22 34-36 7385 120 7473  
VM24-22TW 0-1 2640 35 1842  
VM26-142 0-1 1860 40 987  
VM26-142 30-32 4400 40 3985  
GY97-06PC20 11-12 830 30 --  
GY97-06PC20 40 2340 40 1501  
GY97-06PC20 77-78 3540 30 2914  
GY97-06PC20 100 4900 40 4698  
GY97-06PC20 140 6870 40 6950  
GY97-06PC20 160 8300 40 8357  
GY97-06PC20 185-186 10050 35 10310  
IG19-3-35 20-21 3570 40 2946  
IG19-3-35 60-61 7710 40 7752  
TR126-10 118-120 26100 90 -- Too old to be converted
TR126-10 118-120 29910 130 -- Globorotalia truncatulinoides (too old)
TR126-10 118-120 34380 340 -- Neogloboquadrina dutertrei (too old)
TR126-10 200-202 49100 1100 -- Too old to be converted
TR126-10 400-402 49100 1100 -- Too old to be converted
TR126-10 700-702 49300 1200 -- Too old to be converted
TR126-11 100-102 30600 140 -- Too old to be converted
TR126-11 350-352 46580 890 -- Too old to be converted
TR126-23 0-1 1910 35 1053  
TR126-30 0-1 4865 35 4625  
TR126-33 0-1 4920 50 4743 GlobigerinoidesRuber and G sacculifer
KN159JPC6TW 0-1 2210 40 1338  
KN159JPC6 0-1 940 35 167  
KN159JPC6 5 730 35 -- Too young to be converted
KN159JPC6 20 1145 40 410  
KN159JPC6 49-50 1820 35 951  
KN159JPC6 100-101 2610 35 1813  
KN159JPC6 128-129 3460 35 2811  
KN159JPC31-1-1 3-4 1510 40 658  
KN159JPC31-1-3 0-1 6100 30 6111  
KN159JPC33 0-1 730 30 -- Too young to be converted
KN159JPC33 60-61 2290 40 1417  
KN159JPC34 2-3 610 40 -- Too young to be converted
KN159JPC34 81-82 3630 40 3039  
KN159JPC35 5 900 40 123  
KN159JPC35 20 1495 40 651  
GY94H2GC2 11-13 540 50 -- Too young to be converted
GY94H2GC2 11-13 940 50 167 Benthics
GY94H2GC2 13-14.5 580 40 -- Too young to be converted
GY94H2GC2 46-48 1330 50 524  
GY94H2GC2 46-48 1520 40 662 Benthics
GY94H2GC2 48-50 1320 30 518  
GY94H2GC2 48-50 1510 30 658 Benthics
GY94H8GC8 14-16 470 60 -- Too young to be converted
GY94H8GC8 46-48 760 50 -- Too young to be converted
GY94H17GC16 10-12 400 60 -- Too young to be converted
GY94H17GC16 10-12 630 50 -- Benthics (too young)
GY94H17GC16 12-14 390 40 -- Too young to be converted
GY94H17GC16 12-14 620 30 -- Benthics (too young)
GY94H17GC16 49-51 790 40 -- Too young to be converted
GY94H17GC16 49-51 940 50 167 Benthics
GY94H17GC16 51-53 870 40 66  
GY94H17GC16 51-53 1160 40 421 benthics
GY94H23GC23 11-13 610 40 -- Too young to be converted
GY94H23GC23 11-13 640 50 -- Benthics (too young)
GY94H23GC23 48-49 1140 50 404  
GY94H23GC23 48-49 1390 50 557 Benthics
GY94H39GC36 12-14 1300 50 509 Benthics
GY94H39GC36 30-32 1860 50 987 Benthics
GY94H50GC43 10-12 1590 40 721  
GY94H50GC43 40-42 3700 50 3150  
GY94H50GC43 40-42 4640 40 4351 Benthics
GY94H114GC81 6-8 1610 40 736  
GY94H114GC81 6-8 2360 50 1515 Benthics
GY94H114GC81 16-18 1790 40 928  
GY94H114GC81 16-18 2800 40 2020 Benthics
GY94H121GC88 10-12 610 40 -- Too young to be converted
GY94H121GC88 42-44 1300 40 509  
GY94H121GC88 42-44 1650 30 781 Benthics
MD02-2553 5-6 605 40 -- Too young to be converted
MD02-2553 100-101 3265 40 2685  
MD02-2553 200-201 5155 40 4987  
MD02-2553 300-301 8520 45 8582  

a radiocarbon years

b calendar years (Stuiver et al., 1998)

c samples with no entry in this column are too young/old to be calibrated

ACKNOWLEDGEMENTS

We thank Lynn Wingard and Thomas Cronin for thoughtful reviews of this work.  We thank Bethany Boisvert, Kate Pavich, and Jessica Darling for help with sample procurement and processing. John McGeehin provided assistance with AMS 14C analyses.  We are grateful to Nial Slowey and William Bryant (TAMU), Rusty Lotti (LDEO), Arman Silva and Steven Carey (URI) for providing material.  The LDEO core lab is funded under NSF Grant OCE97-11316 and Office of Naval Research Grant N00014-96-10186.  The URI core lab is funded under NSF Grant OCE-0002226.  This work was supported by the USGS Earth Surface Dynamics Program. 

REFERENCES

Blow, W.H., 1969.  Late middle Eocene to Recent planktonic foraminiferal biostratigraphy.  In: Bronnimann, P. and Renz, H.H., (Eds.), Proceedings of the First Planktonic Conference:  Leiden (E.J. Brill), p. 199-422.

Brunner, C.A., 1979.  Distribution of planktonic foraminifera in surface sediments of the Gulf of Mexico.  Micropaleontology, 25(3): 325-335.

Brunner, C.A., 1982.  Paleoceanography of surface waters in the Gulf of Mexico during the Late Quaternary.  Quaternary Research, 17: 105-119.

Brunner, C.A. and Cooley, J.F., 1976.  Circulation in the Gulf of Mexico during the last glacial maximum.  Geological Society of America, Bulletin, 87: 681-686.

CLIMAP, 1976.  The surface of the ice-age earth.  Science, 191: 1131-1137.

CLIMAP, 1981.  Seasonal reconstructions of the Earths surface at the last glacial maximum.  In: McIntyre, A., Map and Chart Series 36, Geological Society of America.

CLIMAP, 1984.  The last interglacial ocean.  Quaternary Research, 21: 123-224.

Cline, R. and Hays, J. (eds.), 1976.  Investigation of Late Quaternary paleoceanography and paleoclimatology.  Geological Society of America Memoir 145.

Dowsett, H.J., Barron, J.A., Poore, R.Z., Thompson, R.S., Cronin, T.M., Ishman, S.E., and Willard, D.A., 1999.  Middle Pliocene paleoenvironmental reconstruction:  PRISM2.  USGS Open File Report 99-535, http://pubs.usgs.gov/openfile/of99-535/.

Dowsett, H.J., Brunner, C.A., Poore, R.Z. and Boisvert, B.A., 2002.  Gulf of Mexico planktic foraminifer core-top data.  EOS Transactions AGU, 83(19), Spring Meeting Supplement, Abstract GS41A-09.

Dowsett, H.J. and Poore, R.Z., 2001.  Planktic foraminifer census data from the northwestern Gulf of Mexico.  U.S. Geological Survey Open File Report 01-108: 1-6.

Imbrie, J. and Kipp, N.G., 1971.  A new micropaleontological method for quantitative paleoclimatology:  Application to a late Pleistocene Caribbean core.  In: Turekian, K.K. (ed.), The Late Cenozoic Glacial Ages.  New Haven, Yale University Press: 72-181.

Kennet, J.P. and Srinivasan, S., 1983.  Neogene planktonic foraminifera:  a phylogenetic atlas.  Hutchinson Ross, New York, 265p.

Murray, J., 1995.  Microfossil indicators of ocean water masses, circulation and climate, In, Bosence, D. and Allison, P. (eds.), Marine palaeoenvironmental analysis from fossils, Geological Society Special Publication 83: 245-264.

Parker, F.L., 1962.  Planktonic foraminiferal species in Pacific sediments.  Micropaleontology, 8:  219-254.

Parker, F.L., 1967.  Late Tertiary biostratigraphy (Planktonic Foraminifera) of tropical Indo-Pacific deep-sea cores:  Bulletins of American Paleontology, 8:  115-208.

Poore, R.Z., Dowsett, H.J.,Verardo, S., and Quinn, T.M., in review.  Millenial to century scale variability in Gulf of Mexico Holocene climate records.  Paleoceanography.

Roberts, M., Bench, G., Brown, T., Caffee, M., Finkel, R., Freeman, S., Hainsworth, L., Kashgarian, M., McAninch, J., Proctor, I., Southon, J., and Vogel, J., 1997.  The LLNL AMS Facility, In:  Jull, J., Beck, J., and Burr, G., Eds., Proceedings of the Seventh International Conference on Accelerator Mass Spectrometry, Tucson, AZ, USA, North Holland Press, p. 57-61.

Stuiver, M., et al., 1998.  INTCAL98 Radiocarbon age calibration.  Radiocarbon 40(3): 1041-1083.



[1] U.S. Geological Survey, 926A National Center, Reston, Virginia, 20192

[2] Department of Marine Science, University of Southern Mississippi, Stennis Space Center, Mississippi, 39529

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