Wilson, R. C. L. and Hiscott, Richard N. (2007): Ar/Ar dating of white mica clasts in early to late postrift sediments sampled during OPD Leg 210 off Newfoundland

Leg/Site/Hole:
ODP 210
ODP 210 1276
Identifier:
2007-087751
georefid

10.2973/odp.proc.sr.210.106.2007
doi

Creator:
Wilson, R. C. L.
Open University, Department of Earth Sciences, Milton Keynes, United Kingdom
author

Hiscott, Richard N.
IFREMER Centre de Brest, France
author

Identification:
Ar/Ar dating of white mica clasts in early to late postrift sediments sampled during OPD Leg 210 off Newfoundland
2007
In: Tucholke, Brian E., Sibuet, Jean-Claude, Klaus, Adam, Arnaboldi, Michela, Delius, Heike, Engstrom, Anna V., Galbrun, Bruno, Gardin, Silvia, Hiscott, Richard N., Karner, Garry D., Ladner, Bryan C., Leckie, R. Mark, Lee, Chao-Shing, Manatschal, Gianreto, Marsaglia, Kathleen M., Pletsch, Thomas K., Pross, Joerg, Robertson, Alastair H. F., Sawyer, Dale S., Sawyer, Derek E., Shillington, Donna J., Shirai, Masaaki, Shryane, Therese, Stant, Sharon Audra, Takata, Hiroyuki, Urquhart, Elspeth, Wilson, Chris, Zhao, Xixi, Proceedings of the Ocean Drilling Program; scientific results; drilling the Newfoundland half of the Newfoundland-Iberia transect; the first conjugate margin drilling in a nonvolcanic rift; covering Leg 210 of the cruises of the Drilling Vessel JOIDES Resolution; St. Georges, Bermuda, to St. John's, Newfoundland; sites 1276 and 1277; 6 July-6 September 2003
Texas A&M University, Ocean Drilling Program, College Station, TX, United States
210
Fifty-seven white mica clasts were separated from five samples taken from near the bases of turbidites ranging in age from early Albian to middle Eocene. Twenty two (39%) of the micas have ages between 260 and 340 Ma and five (9%) have older ages ( approximately 400-600 Ma). The former age range is characteristic of the North American Alleghenian orogeny and the Iberian Variscan orogeny. The latter range is characteristic of the North American Acadian orogeny and older basement rocks in the Grand Banks and Newfoundland areas. Both age ranges are present in the middle Eocene sample, but only the younger range occurs in the middle Albian sample. This difference could be a sampling artifact. If this is not the case, then the most likely explanation is that the Acadian- aged micas within the Meguma Zone underlying the Grand Banks were totally reset by Alleghenian reactivation of the zone, a feature which occurs extensively in Nova Scotia. The addition of Acadian-aged micas in the middle Eocene sample may reflect a change in sediment provenance as drainage systems unrelated to rift topography developed. With the exception of one clast dated at 186 Ma, the 12 other micas obtained from the upper Paleocene sample yielded ages between 55 and 74 Ma, with 7 falling within + or -2 m.y. of the 57-Ma age of the sample indicated by the biostratigraphic age-depth plot for Site 1276. This, together with the volcaniclastic content of the sample, indicates an input from near-contemporaneous volcanism. The nearest known occurrences of near-contemporaneous late Paleocene volcanism that could have produced white micas are in Greenland and Portugal, some 2000 and 1500 km distant, respectively, from Site 1276 during the Paleocene. However, ages of volcanism in these areas indicate that they could probably not be sources of micas younger than 60 m.y., which suggests some as-yet unknown volcanic source in the North Atlantic area. Accumulation in the Grand Banks area of airborne-transported volcaniclastic material from eruptions of slightly different ages, followed by a single resedimentation event, could account for the spread of dates obtained from the sample. White micas from the lowermost Albian sample show a spread of ages between 37 and 284 Ma that is completely different from the age distribution pattern of the middle Albian and middle Eocene samples. The sample location is between, and at least 25 m above and below, two igneous sills dated at 98 and 105 Ma. The sills have narrow thermal aureoles and ages older than the youngest detrital micas in the sample. It is unlikely, therefore, that the spread of mica ages in the sample is due to partial resetting of ages caused by thermal effects associated with the intrusion of the sills. The resetting may have been associated with a longer lived thermal event.
English
Coverage:Geographic coordinates:
North:45.2400
West:-44.4700East: -44.4700
South:45.2400

Stratigraphy; Geochronology; absolute age; Ar/Ar; Atlantic Ocean; Canada; Cenozoic; clastic rocks; clasts; continental margin; cores; Cretaceous; dates; detritus; Eastern Canada; Flemish Cap; Grand Banks; Leg 210; Meguma Terrane; Mesozoic; mica group; muscovite; Newfoundland; Newfoundland and Labrador; North Atlantic; Northwest Atlantic; Ocean Drilling Program; ODP Site 1276; paleo-oceanography; paleocurrents; Paleogene; paleogeography; provenance; sedimentary rocks; sheet silicates; silicates; Tertiary;

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