Late Quaternary sea surface conditions in the Laurentian Fan: Evidence from coccolith and dinocyst assemblages

Palaeogeography, Palaeoclimatology, Palaeoecology

Volumn 387, Issue , 2013, Pages 200-210

  Balestra, Barbara ^a,b   Bertini, Adele ^c,d   de Vernal, Anne ^e   Monechi, Simonetta ^c   Reale, Viviana ^c  

^a CITY UNIVERSITY OF NEW YORK   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

^c UNIVERSITY OF FLORENCE   (Italy)

^d SEZIONE DI FIRENZE   (Italy)

^e UNIVERSITÉ DU QUÉBEC À MONTRÉAL   (Canada)

Author keywords

Coccolith; Dinocyst; Holocene; Late Quaternary; Laurentian Fan; St. Lawrence River

Indexed keywords

BIOLOGICAL DEVELOPMENT; CLIMATE CONDITIONS; COCCOLITH; HOLOCENE; POPULATION DISTRIBUTION; QUATERNARY; SEA SURFACE; SPECIES DIVERSITY; WATER DEPTH;

ATLANTIC OCEAN; ATLANTIC OCEAN (NORTH);

HAPTOPHYCEAE;

EID: 84884203306     PISSN: 00310182     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.palaeo.2013.07.002     Document Type: Article

References (101)

1. Andersen C., Koç N., Moros M. A highly unstable Holocene climate in the subpolar North Atlantic: evidence from diatoms. Quaternary Science Reviews 2004, 23:2155-2166.
2. Andrews J.T., Giraudeau J. Multi-proxy records showing significant Holocene environmental variability: the inner n. Iceland shelf (Húnaflói). Quaternary Science Reviews 2003, 22(2-4):175-193.
3. Andruleit H. A filtration technique for quantitative studies of coccoliths. Micropaleontology 1996, 42:403-406.
4. Andruleit H. Coccolithophore fluxes in the Norwegian Greenland Sea: seasonality and assemblage alterations. Marine Micropaleontology 1997, 31:45-64.
5. Andruleit H., Baumann K.-H. History of the last deglaciation and Holocene in the Nordic seas as revealed by coccolithophore assemblages. Marine Micropaleontology 1998, 35:179-201.
6. Arhan M., Colin de Verdiere A., Mercier H. Direct observations of the mean circulation at 48°N in the Atlantic Ocean. Journal of Physical Oceanography 1989, 19:161-181.
7. Balestra B., Ziveri P., Monechi S., Troelstra S. Coccolithophorids from the Southeast Greenland Margin (Northern North Atlantic): production, ecology and the surface sediment record. Micropaleontology 2004, 50(supplement no.1):23-34.
8. Balestra B., Ziveri P., Baumann K.-H., Monechi S., Troelstra S. Surface water dynamics in the Reykjanes Ridge area during the Holocene as revealed by coccolith assemblages. Marine Micropaleontology 2010, 76:1-10.
9. Baumann K.-H., Freitag T. Pleistocene fluctuations in the northern Benguela current system as revealed by coccolith assemblages. Marine Micropaleontology 2004, 52:195-215.
10. Baumann K.-H., Matthiessen J. Variations in surface-water mass conditions in the Norwegian sea - evidence from Holocene coccolith and dinoflagellate cyst assemblages. Marine Micropaleontology 1992, 20:129-146.
11. Baumann K.-H., Andruleit H.A., Samtleben C. Coccolithophores in the Nordic seas: comparison of living communities with surface sediment assemblages. Deep Sea Research Part II: Topical Studies in Oceanography 2000, 47:9-11. (1743-1772). J.D. Milliman (Ed.).
12. Belkin I.M., Levitus S. Temporal variability of the Subarctic Front near the Charlie-Gibbs Fracture Zone. Journal of Geophysical Research 1996, 101(C12):28,317-28,324.
13. Berger A.L. Long term variations of caloric insolation resulting from the earth's orbital elements. Quaternary Research 1978, 9(2):139-167.
14. Berner K.S., Koc N., Divine D., Godtliebsen F., Moros M. A decadal-scale Holocene sea surface temperature record from the subpolar North Atlantic constructed using diatoms and statistics and its relation to other climate parameters. Paleoceanography 2008, 23:PA2210.
15. Bertini A. Cambiamenti paleoambientali sul lato Nord Occidentale dell'Atlantico settentrionale durante gli ultimi 20Ka sulla base delle associazioni a palinomorfi. Report: Advanced Fellowship NATO-CNR 1998.
16. Bertini A., de Vernal A., Hillaire-Marcel C., Bilodeau G. Palaeoceanographical changes in the northwest North Atlantic since ca. 20Ka based on dinocyst assemblages. Dino 6. NTNU Vitensk. Mus. Rapp. Bot. Ser. 1998, 14-15. 1998, Abstract.
17. Bollmann J., Baumann K.-H. Global dominance of Gephyrocapsa coccoliths in late Pleistocene: selective dissolution, evolution, or global environmental change?. Paleoceanography 1998, 13:517-529.
18. Bond G., Showers W., Cheseby M., Lotti R., Almasi P., deMenocal P., Priore P., Cullen H., Hajdas I., Bonani G. A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates. Science 1997, 14(278):1257-1266.
19. Bond G., Kromer B., Beer J., Muscheler R., Evans M.N., Shower W., Hoffmann S., Lotti, Bond R., Hajdas I., Bonani G. Persistent solar influence on North Atlantic climate during the Holocene. Science 2001, 294:2130-2135.
20. Bonnet S., de Vernal A., Gersonde R., Lembke-Jene L. Modern distribution of dinocysts from the North Pacific Ocean (37-64°N, 144°E-148°W) in relation to hydrographic conditions, sea-ice and productivity. Marine Micropaleontology 2012, 84-85:87-113.
21. 3) flux in the Sea of Okhotsk: seasonality, settling and alteration processes. Marine Micropaleontology 2000, 39:179-200.
22. Brown C.W., Yoder J.A. Coccolithophorid blooms in the global ocean. Journal of Geophysical Research 1994, 99:7467-7482.
23. Dale B. Dinoflagellate cyst ecology: modeling and geological applications. Palynology: Principles and Applications 1996, vol. 3:1249-1275. American Association of Stratigraphic Palynologists Foundation, Dallas, TX. J. Jansonius, D.C. McGregor (Eds.).
24. Dale B., Dale A. Dinoflagellate contributions to the deep sea. Ocean Biocoenosis Series 1992, 5:02543. Woods Hole Oceanographic Institution, Woods Hole, MA.
25. de Vernal A., Hillaire-Marcel C. Provincialism in trends and high frequency changes in the northwest North Atlantic during the Holocene. Global and Planetary Change 2006, 54:263-290.
26. de Vernal A., Bilodeau G., Hillaire-Marcel C., Kassou N. Quantitative assessment of carbonate dissolution in marine sediments from foraminifer linings vs. shell ratios: Davis Strait, northwest North Atlantic. Geology 1992, 20:527-530.
27. de Vernal A., Turon J.L., Guiot J. Dinoflagellate cyst distribution in high latitude environments and quantitative reconstruction of sea-surface temperature, salinity and seasonality. Canadian Journal of Earth Sciences 1994, 31:48-62.
28. de Vernal A., Henry M., Matthiessen J., Mudie P.J., Rochon A., Boessenkool K.P., Eynaud F., Grøsfjeld K., Guiot J., Hamel D., Harland R., Head M.J., Kunz-Pirrung M., Levac E., Loucheur V., Peyron O., Pospelova V., Radi T., Turon J.-L., Voronina E. Dinoflagellate cyst assemblages as tracers of sea-surface conditions in the northern North Atlantic, Arctic and sub-Arctic seas: the new n=677 data base and its application for quantitative palaeoceanographic reconstruction. Journal of Quaternary Science 2001, 16:681-698.
29. de Vernal A., Eynaud F., Henry M., Hillaire-Marcel C., Londeix L., Mangin S., Matthiessen J., Marret F., Radi T., Rochon A., Solignac S., Turon J.-L. Reconstruction of sea-surface conditions at middle to high latitudes of the Northern Hemisphere during the Last Glacial Maximum (LGM) based on dinoflagellate cyst assemblages. Quaternary Science Reviews 2005, 24:897-924.
30. de Vernal A., St-Onge G., Gilbert D. Oceanography and Quaternary geology of the St. Lawrence Estuary and the Saguenay Fjord. IOP Conference Series: Earth and Environmental Science 2011, 14:012004.
31. Dietrich G.K., Kalle K., Siedler G. General Oceanography, (translated by S. and H.U. Roll) 1980, Wiley, New York, NY, (626 pp.).
32. Farmer E.J., Chapman M.R., Andrews J.E. Centennial-scale Holocene North Atlantic surface temperatures from Mg/Ca ratios in Globigerina buloides. Geochemistry, Geophysics, Geosystems 2008, 9. (15 pp.).
33. Flores J.A., Sierro F.J., Francés G., Vázquez A., Zamarreño L. The last100,000years in the western Mediterranean: sea surface water and frontal dynamics as revealed by coccolithophores. Marine Micropaleontology 1997, 29:351-366.
34. Fofonof N.P., Hendry R.M. Current variability near the southeast Newfoundland Ridge. Journal of Physical Oceanography 1985, 15:963-984.
35. Furevik A., Nilsen J.E.Ø. The large-scale atmospheric circulation variability and its impact in the Nordic Seas ocean climate: a review. Geophysical Monograph Series, AGU 2005, 158:105-136. Washington, D. C. 10.1029/158GM09. H. Drange, T. Furevik, R. Gerdes, W. Berger (Eds.).
36. Gartner S., Chow J., Santon Jr Late Neogene paleoceanography of the eastern Gulf of Mexico and the eastern equatorial Pacific. Marine Micropaleontology 1987, 12:255-304.
37. Geitzenauer K.R., Roche M.B., McIntyre A. Coccolith biogeography from North Atlantic and Pacific surface sediments. Oceanic Micropaleontology 1977, 973-1008. Academic Press, New York. A.T.S. Ramsey (Ed.).
38. Giraudeau J., Monteiro P.M.S., Nikodemus K. Distribution and malformation of living Coccolithophores in the Northern Benguela upwelling system off Namibia. Marine Micropaleontology 1993, 22(1-2):93-110.
39. Giraudeau J., Cremer M., Manthé S., Labeyrie L., Bond G. Coccolith evidence for instabilities in surface circulation south of Iceland during Holocene times. Earth and Planetary Sciences Letters 2000, 179:257-268.
40. Giraudeau J., Jennings A.E., Andrews J.T. Timing and mechanisms of surface and intermediate water circulation changes in the Nordic seas over the last 10,000calyears: a view from the north Iceland shelf. Quaternary Science Reviews 2004, 23(20-22):2127-2139.
41. Giraudeau J., Grelaud M., Solignac S., Andrews J.T., Moros M., Jansen E. Millenial-scale variability in Atlantic water advection to the Nordic Seas derived from Holocene coccolith concentration records. Quaternary Science Reviews 2010, 29(9-10):1276-1287.
42. Guiot J., de Vernal A. Chapter thirteen transfer functions: methods for quantitative paleoceanography based on microfossils. Developments in marine geology 2007, 1:523-563.
43. Hald M., Aspeli R. Rapid climatic shifts of the northern Norwegian Sea during the last deglaciation and the Holocene. Boreas 1997, 26:15-28.
44. Hay W.W. Carbonate fluxes and calcareous nannoplankton. Coccolithophores-from molecular to global impact 2004, 509-527. Springer-Verlag, Berlin. H.R. Thierstein, J.R. Young (Eds.).
45. Head M.J., Harland R., Matthiessen J. Cold marine indicators of the late Quaternary: the new dinoflagellate cyst genus Islandinium and related morphotypes. Journal of Quaternary Science 2001, 16:621-636.
46. Henriksson A.S. Coccolithophore response to oceanographic changes in the equatorial Atlantic during the last 200,000years. Palaeogeography, Palaeoclimatology Palaecology 2000, 156:161-173.
47. Hillaire-Marcel C., de Vernal A., Bilodeau G., Weaver A.J. Absence of deep water formation in the Labrador Sea during the last interglacial period. Nature 2001, 410:1073-1077.
48. Hillaire-Marcel C., de Vernal A., Bilodeau G., Stoner J.S. Changes of potential density gradients in the northwestern North Atlantic during the last climatic cycle based on a multiproxy approach. Geophysical Monograph Series 2001, 126:83-100.
49. Hillaire-Marcel C., de Vernal A., Piper D.J.W. Lake Agassiz Final drainage in the northwest North Atlantic. Geophysical Research Letters 2007, 34(L15601):5pp.
50. Hughen K.A., Baillie M.G.L., Bard E., Bayliss A., Beck J.W., Bertrand C., Blackwell P.G., Buck C.E., Burr G., Cutler K.B., Damon P.E., Edwards R.L., Fairbanks R.G., Friedrich M., Guilderson T.P., Kromer B., McCormac F.G., Manning S., Bronk Ramsey C., Reimer P.J., Reimer R.W., Remmele S., Southon J.R., Stuiver M., Talamo S., Taylor F.M., van der Plicht J., Weyhenmeyer C.E. Marine04 marine radiocarbon age calibration, 0-26cal. kyr BP. Radiocarbon 2004, 46:1059-1086.
51. Hughes P.D.M., Blundell A., Charman D.J., Bartlett S., Daniell J.R.G., Wojatschke A. An 8500cal. year multi-proxy climate record from a bog in eastern Newfoundland: contributions of meltwater discharge and solar forcing. Quaternary Science Reviews 2006, 25:1208-1227.
52. Incarbona A., Martrat B., Di Stefano E., Grimalt J.O., Pelosi N., Patti B., Tranchida G. Primary productivity variability on the Atlantic Iberian Margin over the last 70,000years: evidence from coccolithophores and fossil organic compounds. Paleoceanography 2010, 25:PA2218. 10.1029/2008PA001709.
53. Keigwin L.D., Pickart R.S. Slope water current over the Laurentian Fan on interannual to millennial time scales. Science 1999, 286:520-523.
54. Klitgaard-Kristensen D., Sejrup H.P., Haflidason H. The last 18kyr fluctuations in Norwegian Sea surface conditions and implications for the magnitude of climatic change: evidence from the North Sea. Paleoceanography 2001, 16:1-13.
55. Knappertsbusch M., Cortés M.Y., Thierstein H.R. Morphologic variability of the coccolithophorid Calcidiscus leptoporus in the plankton, surface sediments and from the Early Pleistocene. Marine Micropaleontology 1997, 30:293-317.
56. Koc N., Jansen E., Haflidason H. Paleoceanographic reconstructions of surface ocean conditions in the Greenland, Iceland and Norwegian seas through the last 14ka based on diatoms. Quaternary Science Reviews 1993, 12:115-140.
57. Kokinos J.P., Eglinton T.I., Goni M.A., Boon J.J., Martogliio P.A., Anderson D.M. Characterization of a highly resistant biomacromolecular material in the cell wall of a marine dinoflagellate resting cyst. Organic Geochemistry 1998, 28:265-288.
58. Krauss W. The North Atlantic Current. Journal of Geophysical Research 1986, 91:5061-5074.
59. Lamarche L., Bondue V., Lemelin M.-J., Lamothe M., Roy A.G. Deciphering the Holocene evolution of the St. Lawrence River drainage system using luminescence and radiocarbon dating. Quaternary Geochronology 2007, 2:155-161.
60. Mann C.R. The termination of the Gulf Stream and the beginning of the North Atlantic Current. Deep Sea Research 1967, 14:337-359.
61. Marchal O., Cacho I., Stocker T.F., Grimalt J.O., Calvo E., Martrat B., Shackelton N., Vautravers M., Cortijo E., van Kreveld S., Andersson C., Koç N., Chapman M., Sbaffi L., Duplessy J.-C., Sarnthein M., Turon J.-L., Duprat J., Jansen E. Apparent cooling of the sea surface in the northeast Atlantic and Mediterranean during the Holocene. Quaternary Science Reviews 2002, 21:455-483.
62. Marino M., Maiorano P., Lirer F. Changes in calcareous nannofossil assemblages during the mid-Pleistocene revolution. Marine Micropaleontology 2008, 69:70-90.
63. Marino M., Maiorano P., Flower B.P. Calcareous nannofossil changes during the Mid-Pleistocene Revolution: paleoecologic and paleoceanographic evidence from North Atlantic Site 980/981. Palaeogeography, Palaeoclimatology, Palaeoecology 2011, 306:58-69.
64. Marret F., Scourse J. Control of modern dinoflagellate cyst distribution in the Irish and Celtic seas by seasonal stratification dynamics. Marine Micropaleontology 2002, 47:101-116.
65. Marret F., Zonneveld K.A.F. Atlas of modern organic-walled dinoflagellate cyst distribution. Review of Palaeobotany and Palynology 2003, 125:1-200.
66. Matthews J. The assessment of a method for the determination of absolute pollen frequencies. New Phytologist 1969, 68:161-166.
67. Mayewski P.A., Rohling E.E., Stager C., Karlen W., Maasch K.A., Meeker L.D., Meyerson E.A., Gasse F., Van Kreveld S., Holmgren K., Thorp J.-L., Rosqvist G., Rack F., Staubwasser M., Schneider R.R., Steig E.J. Holocene climate variability. Quaternary Research 2004, 62:243-255.
68. McIntyre A., Bé A.W.H. Modern coccolithophorae of the Atlantic Ocean- I. Placoliths and cyrtholiths. Deep Sea Research 1967, 14:561-597.
69. Moros M., Jansen E., Oppo D.W., Giraudeau J., Kuijpers A. Reconstruction of the Late-Holocene changes in the Sub-Arctic Front position at the Reykjanes Ridge, North Atlantic. The Holocene 2012, 22(8):877-886.
70. Mudie P.J., Rochon A. Distribution of dinoflagellate cysts in the Canadian Arctic marine region. Journal of Quaternary Science 2001, 16(issue 7):603-620.
71. National Oceanographic Data Center (NODC), 2011. World Ocean Atlas. Silver Spring, Md. Available from http://www.nodc.noaa.gov/OC5/WOA01/pr_woa01.html.
72. Pickart R.S., Torres D.J., Mckee T.K., Caruso M.J., Przystup J.E. Diagnosing a meander of the shelfbreak current in the middle Atlantic Bight. Journal of Geophysical Research 1999, 104:3121-3132.
73. Piper D.J.W., Skene K.I. Latest Pleistocene ice-rafting events on the Scotian Margin (eastern Canada) and their relationship to Heinrich events. Paleoceanography 1998, 13:205-214.
74. Pujos A. Stratigraphical and paleoecological distribution of calcareous nannofossils throughout the Quaternary in the Caribbean Sea. Transactions of the 11th Caribbean Geological Conf., Barbados, 20-26 Juillet, 1986 1988, 8. (1-8-13).
75. Rahman A. Reworked nannofossils in the North Atlantic Ocean and subpolar basins: implications for Heinrich events and ocean circulation. Geology 1995, 23(6):487-490.
76. Rahman A., de Vernal A. Surface oceanographic changes in the eastern Labrador Sea; nannofossil record of the last 31,000years. Marine Geology 1994, 121:247-263.
77. Ran L., Jang H., Knudsen K.L., Eiriksson J., Gu Z. Diatom response to the Holocene climatic optimum on the North Iceland Shelf. Marine Micropaleontology 2006, 60:226-241.
78. Renaud S., Ziveri P., Broerse A.T.C. Geographical and seasonal differences in morphology and dynamics of the coccolithophore Calcidiscus leptoporus. Marine Micropaleontology 2002, 890:1-23.
79. Reynaud T.H., Weaver A.J., Greatbatch R.J. Summer mean circulation of the Northwestern Atlantic Ocean. Journal of Geophysical Research 1995, 100:779-816.
80. Risebrobakken B., Jansen E., Anderson C., Mjelde E., Hevrøy K. A high-resolution study of Holocene paleoclimatic and paleoceanographic changes in the Nordic Seas. Paleoceanography 2003, 18:1017.
81. Rochon A., de Vernal A., Turon J.-L., Matthiessen J., Head M.J. Distribution of recent dinoflagellate cysts in surface sediments from the North Atlantic Ocean and adjacent seas in relation to sea-surface parameters. American Association of Stratigraphic Palynologists Contribution Series 1999, 35. (Houston, TX).
82. Saez A.G., Probert I., Geisen M., Quinn P., Young J.Y., Medlin L. Pseudo-cryptic speciation in coccolithophores. PNAS 2003, 100(12):7163-7168.
83. Samtleben C., Bickert T. Coccoliths in sediment traps from the Norwegian Sea. Marine Micropaleontology 1990, 16(1-2):39-64.
84. Samtleben C., Schröder-Ritzrau A. Living coccolithophores communities in the Norwegian-Greenland sea and their record in sediments. Marine Micropaleontology 1992, 19:333-354.
85. Samtleben C., Baumann K.H., Schröder-Ritzrau A. Distribution, composition, and seasonal variation of coccolithophore communities in the northern North Atlantic. 5th Ina Conference In Salamanca Proceedings 1995, 219-235. Flores, Sierro (Eds.).
86. Samtleben P., Schäfer C., Andruleit H., Baumann A., Baumann K.-H., Kohly A., Matthiessen J., Schroder-Ritzrau A. Plankton in the Norwegian-Greenland Sea: from living communities to sediment assemblages. An actualistic approach. Geologische Rundschau 1995, 84:108-136.
87. Schmitz W., McCartney M. On the North Atlantic circulation. Reviews of Geophysics 1993, 31(1):29-49.
88. Skene K.I., Piper D.J.W. Late Quaternary stratigraphy of Laurentian Fan: a record of events off the Eastern Canadian continental margin during the last deglacial period. Quaternary International 2003, 99-100:135-152.
89. Solignac S., de Vernal A., Giraudeau J. Comparison of coccolith and dinocyst assemblages in the northern North Atlantic: how well do they relate with surface hydrography?. Marine Micropaleontology 2008, 68:115-135.
90. Solignac S., Grøsfjeld K., de Giraudeau J., Vernal A. Distribution of recent dinocyst assemblages in the western Barents Sea. Norwegian Journal of Geology 2009, 89:109-119.
91. Solignac S., Seidenkrantz M.S., Jessen C., Kuijpers A., Gunvald A.K., Olsen J. Late-Holocene sea-surface conditions offshore Newfoundland based on dinoflagellate cysts. The Holocene 2011, 21-4:539-552.
92. 14C database and revised CALIB radiocarbon calibration program. Radiocarbon 1993, 35:215-230.
93. Teller J.T., Leverington D.W., Mann J.D. Freshwater outbursts to the oceans from glacial Lake Agassiz and their role in climate change during the last deglaciation. Quaternary Science Reviews 2002, 21:879-887.
94. Traverse A. Production, dispersal, sedimentation and taphonomy of spores/pollen in relation to the interpretation of palynofloras, paleopalynology. Topics in Geobiology 2007, 28:497-542. Springer, Netherlands. Second edition.
95. Westbroek P., Van Hinte G.-J., Brummer M., Veldhuis M., Brownlee C., Green J.C., Harris R., Riddervold Heimdal B. Emiliania huxleyi as a key to biosphere-geosphere interactions. The Systematics Association Special 1994, volume No. 51:321-334. Claredon Press, Oxford. J.C. Green, B.S.C. Leadbeater (Eds.).
96. Williams K.M. Late Quaternary paleoceanography of the western Baffin region: evidence from fossil diatoms. Canadian Journal of Earth Sciences 1990, 27:1487-1494.
97. Young J.R., Geisen M., Cros L., Kleijne A., Probert I., Sprengel C., Ostergaard J.B. A guide to extant coccolithophore taxonomy. Journal of Nannoplankton Research Special Issue 2003, 1:124.
98. Ziveri P., Thunell R.C. Coccolithophore export production in Guaymas basin, Gulf of California: response to climate forcing. Deep Sea Research Part II: Topical Studies in Oceanography 2000, 47:2073-2100.
99. Ziveri P., Baumann K.-H., Böckel B., Bollmann J., Young J. Biogeography of selected Holocene coccoliths in the Atlantic Ocean. Coccolithophores from molecular processes to global impact 2004, 403-428. H.R. Theirstein, J.R. Young (Eds.).
100. Ziveri P., de Bernardi B., Baumann K.-H., Stoll H.M., Mortyn P.G. Sinking of coccolith carbonate and potential contribution to organic carbon ballasting in the deep ocean. Deep Sea Research Part II: Topical Studies in Oceanography 2007, 54:659-675.
101. Zonneveld K.A.F., Versteegh G.J.M., de Lange G.J. Preservation of organic-walled dinoflagellate cysts in different oxygen regimes: a 10,000year natural experiment. Marine Micropaleontology 1997, 29:393-405.