Geology of the Scotian Margin - Biostratigraphic Research

General Remarks

The biostratigraphic component of the Scotian Margin project involved a detailed examination of the Late Cretaceous-Cenozoic section in the following six wells (listed in order of study):

1. Shubenacadie H-100 (Fensome, 2000)
2. Onondaga E-84 (Fensome, 2001)
3. Demascota G-32 (Fensome 2002)
4. Shelburne (Fensome, 2003a)
5. Hesper I-52 (Fensome, 2003b)
6. Wenonah (Fensome, 2003c)

Map of Nova Scotia showing the location of the wells with Biostratigraphic information. Click in study area to zoom in on individual wells and recent biostratigraphic information.

The present study builds on earlier work summarized and referenced in Williams et al. (1990) and detailed in the Scotian Shelf Atlas (Cant, 1991). Since 1990, more refined event biostratigraphic techniques based on dinoflagellate tops (and bottoms where available) have been applied. This technique, together with major advances in dinoflagellate taxonomy of the last decade, has improved significantly the precision and consistency of dinoflagellate-based biostratigraphy. Key references are Fensome et al. (1993, 2004), Williams et al. (1998a,b, 1999).

Based on observations from this project, a "PalyAtlas" of Scotian Margin mid Cretaceous to Neogene dinoflagellate cysts has been assembled (Fensome and Williams, 2004).

Nature of the Samples

Most samples analyzed in this study were cuttings samples, though a few samples from sidewall cores could be used; only rarely was conventional core material available. For cuttings samples, only range tops (last occurrences, last appearance datums or LADs) are reliable stratigraphically; range bottoms (first appearance datums or FADs) are not meaningful because of down well contamination of caved material. FADs from sidewall samples are potentially more reliable, but assemblages from sidewalls are often sparser and material is not available for reprocessing using modern techniques, thus commonly reducing their utility. The palynological material used was all reprocessed for this study, with the exception of samples for Shubenacadie H-100.

Generally for this study, cuttings samples were taken over approximately 10 m every 30 m, and hence sampling is not continuous or horizon specific. Unless evidence from another source of information (such as lithology or well logs) compels an alternate interpretation, a boundary is by convention placed at the top of the appropriate sample. Logically therefore, a particular geochronologic boundary based on evidence from cuttings samples may occur within the range of the sample indicated (in the chart it is aligned with the top of the sample) or within the 20 m sampling gap above the indicated top.

Age Information

The timescale used is that of Gradstein and Ogg (1996). In assessing the ages of biostratigraphic events (LADS and FADS) observed in this study, both published and unpublished information have been used. The latest compilation of useful dinoflagellate events in northern temperate latitudes is that of Williams et al. (1999); unpublished events from the Scotian Basin are based on observations by the author (R.A. Fensome) and G.L. Williams, and it is planned that these will be detailed in a forthcoming publication. The dates are based on the latest correlations of dinoflagellate and other fossil ranges (especially nannofossils) with radiometrically dated deep sea cores (see Williams et al., 1999 for sources).

For several of the wells, "confidence levels" for the age picks are indicated in the charts, a score of 1 being low and a score of 5 high.

Taxonomy

Much basic taxonomy remains to be done for this region and many biostratigraphically useful species remain to be formally described. Hence, many species designations remain informal, in which cases the names or epithets are indicated by quotation marks. These and other taxa are informally described in the digital "PalyAtlas" discussed above (Fensome and Williams, 2004).

Acknowledgements

Graham Williams, Andrew MacRae, John Shimeld and Sonya Dehler provided valuable discussions and enthusaistic encouragement during the course of this study. Bernie Crilley processed the samples, Bill MacMillan compiled original charts and Patrick Upson converted them to web format. Many thanks to all of the above.

References

• Cant, D.J. (co-ordinator) 1991. East Coast Basin Atlas Series, Scotian Shelf. Atlantic Geoscience Centre, Geological Survey of Canada, Dartmouth.
• Fensome, R.A. 2000. Palynological analysis of Shell et al. Shubenacadie H-100 well, Scotian Slope. Report no. M.RES.G.-PAL.2-2000RAF.
• Fensome, R.A. 2001. Palynological analysis of Shell Onondaga E-84 well, Scotian Shelf. Report no. M.RES.G.-PAL.10-2001RAF.
• Fensome, R.A. 2002. Palynological analysis of Shell Demascota G-32 well, Scotian Shelf Report no. M.R.G.-PAL.2-2002RAF.
• Fensome, R.A. 2003a. Palynological analysis of Petro-Canada et al. Shelburne G-29 well, Scotian Slope. Report No. M.R.G.-PAL.1-2003RAF.
• Fensome, R.A. 2003b. Palynological analysis of Petro-Canada-Mobil Hesper I-52 well, Scotian Shelf. Report No. M.R.G.-PAL.4-2003RAF.
• Fensome, R.A. 2003c. Palynological analysis of Petro-Canada-Shell Wenonah J-75 well, Scotian Shelf. Report No. M.R.G.-PAL.5-2003RAF
• Fensome, R.A. and Williams, G.L. 2004 Scotian Margin PalyAtlas: version 1. Geological Survey of Canada Open File 4677.
• Fensome, R.A., Taylor, F.J.R., Norris, G., Sarjeant, W.A.S., Wharton, D.I. and Williams, G.L. 1993. A classification of fossil and living dinoflagellates. Micropaleontology Press Special Paper, no.7, 351 p.
• Fensome, R.A., Lentin, J.K. and Williams, G.L. 2004. The Lentin and Williams Index of fossil dinoflagellates 2004 edition. American Association of Stratigraphic Palynologists, Contributions Series, in press.
• Gradstein, F. and Ogg, J. 1996. A Phanerozoic time scale by Gradstein and Ogg. Episodes, v.19, nos.1-2.
• Williams, G.L., Ascoli, P., Barss, M.S., Bujak, J.P., Davies, E.H., Fensome, R.A. and Williamson, M.A. 1990. Biostratigraphy and related studies: Offshore eastern Canada. Chapter 3 in M.J. Keen and G.L. Williams (eds.), Geology of the Continental Margin off Eastern Canada. Geological Survey of Canada, Geology of Canada, no. 2, p. 89-137 (also Geological Society of America, The Geology of North America, v. I-1).
• Williams, G.L., Lentin, J.K. and Fensome, R.A. 1998a. The Lentin and Williams Index of fossil dinoflagellates 1998 edition. American Association of Stratigraphic Palynologists, Contributions Series, no.34, 817 p.
• Williams, G.L., Brinkhuis, H., Bujak, J.P., Damassa, S.P., Hochuli, P.A., de Verteuil, L. and Zevenboom, D. 1998b. Dinoflagellate cysts. In: "Appendix to: Hardenbol J., Thierry J., Farley M.B., Jacquin Th., de Graciansky P.-C. and Vail P.R. Mesozoic and Cenozoic sequence chronostratigraphic framework of European basins." In: de Graciansky, P.C., Hardenbol, Jacquin, T. and Vail, P.R., Mesozoic and Cenozoic sequence stratigraphy of European basins; Society of Economic Paleontologists and Mineralogists (Society for Sedimentary Geology), Special Publication, no.60, p.764-765.
• Williams, G.L., Bujak, J.P. and Brinkhuis, H. 1999. Mesozoic-Cenozoic dinoflagellate short course, Urbino, Italy, May 19-22, 1999. (Unpublished manual.)

Additional References Cited on Charts

• Ascoli, P. 1976. Foraminiferal and ostracod biostratigraphy of the Mesozoic-Cenozoic, Scotian Shelf, Atlantic Canada.. Maritime Sediments, Special Publication, no. 1, p. 653-771.
• Ascoli, P. 1989. Report on the biostratigraphy (Foraminifera and Ostracoda) and depositional environments of the Shelburne G-29 well, Scotian Shelf, from 2730 to 3990 m (T.D. 4005). Report No. BAS-PAL.6-89PA, 6 p.
• Audretsch, A.P. 1983. Palynological summary report. In: Shell et al. well history report for Shubenacadie H-100.
• Bujak-Davies Group 1985. Palynological report. In: Well history report for Petro-Canada et al. Shelburne G-29; curated by Canada-Nova Scotia Offshore Petroleum Board.
• Clark, D.F. 1973 Nannoplankton analysis of 10 wells from Scotian Shelf: Mobil Sable Island C-67, Shell Onondaga E-84, Shell Oneida O-25, Shell Naskapi N-30, Shell Mohawk B-93, Shell Cree E-35, Shell MicMac J-77, Shell MicMac H-86, Shell Missisauga H-54, and Shell Huron P-96. Report No. EPGS-PAL.9-73DFC. (Unpublished report.)
• Davies, E.H. 1980 Palynological analysis of the Shell Onondaga E-84 well, Sable Island, Scotian Shelf, offshore eastern Canada. Report No. EPGS-PAL.27-80EHD, 8 p. (Unpublished report.)
• Doeven, P.H. 1979 Late Cretaceous nannofossil stratigraphy, offshore Eastern Canada, Part I. Report No. EPGS-PAL.29-79PD, 13 p. (Unpublished report.)
• Doeven, P.H. 1983. Cretaceous nannofossil stratigraphy and paleoecology of the Canadian Atlantic Margin. Geological Survey of Canada, Bulletin 356, 70 p.
• Gradstein, F.M. 1978. Foraminiferal stratigraphy of Petro-Canada-Shell Wenonah J-75. Report No. EPGS-PAL.11-78FMG, 2 p.
• La Borde Micropaleo Consulting 1986 Biostratigraphic report. In: Well history report for Petro-Canada et al. Shelburne G-29; curated by Canada-Nova Scotia Offshore Petroleum Board.
• Leskiw, K. 1983. Micropaleontology summary report. In: Shell et al. well history report for Shubenacadie H-100.
• MacLean, B.C. and Wade, J.A. 1993. East coast basin atlas series: seismic markers and stratigraphic picks in Scotian Basin wells. Atlantic Geoscience Centre, Geological Survey of Canada, 276 p.
• Petro-Canada 1976 Biostratigraphic report. In Well history report for Box Valley / Husky et al. Hesper P-52; curated by Canada-Nova Scotia Offshore Petroleum Board.
• Robertson Research. 1972. Micropaleontology, palynology and stratigraphy report. In: Well history report; curated by Canada-Nova Scotia Offshore Petroleum Board.
• Shell Canada Limited, 1970a. Palynology report. In: Well history report for Shell Onondaga E-87; curated by Canada-Nova Scotia Offshore Petroleum Board.
• Shell Canada Limited, 1970b. Micropaleontology report. In: Well history report for Shell Onondaga E-87; curated by Canada-Nova Scotia Offshore Petroleum Board.
• Texaco, 1972. Biostratigraphy report. In: Well history report for Shell Onondaga E-84; curated by Canada-Nova Scotia Offshore Petroleum Board.
• Thomas, F.C. 1991. Report on the Cenozoic biostratigraphy (Foraminifera) and depositional environments of the Shell Onondaga E-84 well, Scotian Shelf, from 907 to 3977' (top of Cretaceous). Report No. BAS-PAL.9-91FCT, 5 p. (Unpublished report.)
• Thomas, F.C. 2000. The Cenozoic interval of Shell et al. Shubenacadie H-100, its foraminiferal content, depositional environment, interpretation, and implications for local seismic stratigraphy. Report No.M.Res.G.-MAF.2-2000CTF, 11 p.
• Thomas, F.C. 2001. PetroCanada-Shell Wenonah J-75 revisited - Cenozoic micropaleontology and paleoenvironments. Report No. M.Res.G.-PAL.10-2001FCT, 9 p.