scholarly journals Stratigraphy and depositional history of some Upper Proterozoic Sedimentary Rocks on northwestern Baffin Island, District of Franklin

1979 ◽  
Author(s):  
T R Iannelli
Keyword(s):  
Sedimentary Rocks ◽  
Baffin Island ◽  
Depositional History ◽  
Upper Proterozoic ◽  
History Of

Geochronology of the Belt Series, Montana

1968 ◽  
Vol 5 (3) ◽  
pp. 737-747 ◽  
Author(s):  
J. D. Obradovich ◽  
Z. E. Peterman
Keyword(s):  
Average Rate ◽  
Sedimentary Rocks ◽  
Time Interval ◽  
Depositional History ◽  
Middle Cambrian ◽  
Basement Rocks ◽  
Field Evidence ◽  
Minimum Age ◽  
History Of ◽  
Central Montana

This paper presents new radiometric data that permit some qualified statements to be made on the depositional history of the Belt sedimentary rocks. The period of deposition of sedimentary rocks of the Precambrian Belt Series has been placed within a broad time interval, for they rest on metamorphosed basement rock dated at ~ 1800 m.y. and are overlain by the Middle Cambrian Flathead Quartzite (circa 530 m.y.). Prior geochronometric data gathered during the last decade indicate most of the Belt Series to be older than ~ 1100 m.y.K–Ar and Rb–Sr techniques have been applied recently to a variety of samples selected from the whole gamut of the Belt Series. Glauconite from various formations in the sequence McNamara Formation down to the uppermost beds of the Empire Formation in the Sun River area has been dated at 1080 ± 27 m.y. by the K–Ar method and at 1095 ± 22 m.y. by the Rb–Sr mineral isochron method. A Rb–Sr whole-rock isochron based on argillaceous sedimentary rocks from this 5000-ft section gives an age of 1100 ± 53 m.y. The concordance of the preceding results and the K–Ar ages (1075 to 1110 m.y.) on Purcell sills and lava imply that this age represents the time of sedimentation of these units.A Rb–Sr isochron based on whole-rock samples stratigraphically far below the Umpire Formation— the Greyson Shale, Newland Limestone, Chamberlain Shale, and Neihart Quartzite in the Big Belt and Little Beit Mountains—yields an age of 1325 ± 15 m.y. This result is interpreted as indicating a substantial unconformity beneath the Belt Series, at least in central Montana; it also suggests a major hiatus, unsuspected from field evidence, between the uppermost part of the Empire Formation and the Greyson Shale.The results for the youngest of Belt rocks—the Pilcher Quartzite and the Garnet Range Formation, which are exposed in the Alberton region—are equivocal in that there is widespread dispersion. A large component of detrital muscovite in some of the samples could readily account for the magnitude and sense of this dispersion. A maximum age of ~930 m.y. based on an isochron of minimum slope through the various points may be inferred for this sequence. A K–Ar age of 760 m.y. obtained on biotite from a sill in the Garnet Range Formation provides a minimum age for these younger Belt rocks.Three distinct periods of sedimentation for Belt rocks sampled are suggested at ≥ 1300, 1100, and ≤ 900 m.y., with two substantial hiatuses of 200 m.y. or more. In addition the data for the sequence in the Big and Little Belt Mountains suggest that sedimentation may not have commenced for a period of possibly 400 m.y. after the metamorphism that affected basement rocks, while the data for the Garnet Range and Pilcher sequence suggest that sedimentation ceased some 200 to 400 m.y. prior to the deposition of the Middle Cambrian Flathead Quartzite.To suggest that the Belt sediments were deposited continuously over a period of 400 m.y. or more would imply an unusually low average rate of deposition of ≤ 0.1 ft/1000 yr, and this for the thickest part of the Belt Series. As a realistic expression of the depositional history of the Belt Series, both viewpoints are open to question, but the viewpoint that the Belt basin has been characterized by discontinuous sedimentation would be more in keeping with the principle of uniformity.

Structural and depositional history of East Timor

2018 ◽  
Author(s):  
T.A. Reed
Keyword(s):  
East Timor ◽  
Depositional History ◽  
History Of

CLIMATIC AND DEPOSITIONAL HISTORY OF THE LOWER PALEOCENE UPPER NACIMIENTO FORMATION, SAN JUAN BASIN, NEW MEXICO

2016 ◽  
Author(s):  
Caitlin E. Leslie ◽  
◽  
Ross Secord ◽  
Daniel J. Peppe ◽  
Stacy Atchley ◽  
...  
Keyword(s):  
New Mexico ◽  
San Juan ◽  
Depositional History ◽  
San Juan Basin ◽  
History Of

PROVENANCE AND SYNTECTONIC DEPOSITIONAL HISTORY OF THE MIOCENE CAMERINO DEEPWATER BASIN, CENTRAL ITALY

2020 ◽  
Author(s):  
Alan Pitts ◽  
◽  
Achim D. Herrmann ◽  
John T. Haynes ◽  
Gabriele Giuli ◽  
...  
Keyword(s):  
Central Italy ◽  
Depositional History ◽  
History Of ◽  
Deepwater Basin

Late Quaternary depositional history of the North Evvoikos Gulf, Aegean Sea, Greece

2006 ◽  
Vol 232 (3-4) ◽  
pp. 157-172 ◽  
Author(s):  
T.H. Van Andel ◽  
C. Perissoratis
Keyword(s):  
Late Quaternary ◽  
Aegean Sea ◽  
Depositional History ◽  
The North ◽  
History Of
Sign in / Sign up

Export Citation Format

Share Document