Relationship of Fluviodeltaic Facies to Coal Deposition in the Lower Fort Union Formation (Palaeocene), South-Western North Dakota

  1. R. A. Rahmani and
  2. R. M. Flores
  1. Edward S. Belt1,2,
  2. Romeo M. Flores1,
  3. Peter D. Warwick1,3,
  4. Kevin M. Conway2,
  5. Kirk R. Johnson2 and
  6. Robert S. Waskowitz2

Published Online: 28 APR 2009

DOI: 10.1002/9781444303797.ch10

Sedimentology of Coal and Coal-Bearing Sequences

Sedimentology of Coal and Coal-Bearing Sequences

How to Cite

Belt, E. S., Flores, R. M., Warwick, P. D., Conway, K. M., Johnson, K. R. and Waskowitz, R. S. (1985) Relationship of Fluviodeltaic Facies to Coal Deposition in the Lower Fort Union Formation (Palaeocene), South-Western North Dakota, in Sedimentology of Coal and Coal-Bearing Sequences (eds R. A. Rahmani and R. M. Flores), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303797.ch10

Author Information

  1. 1

    United States Geological Survey, Box 25046, DFC, MS 972 Denver, CO 80225, USA

  2. 2

    Amherst College, Amherst, MA 01002, USA

  3. 3

    University of Kentucky, Lexington, KY 40506, USA

Publication History

  1. Published Online: 28 APR 2009
  2. Published Print: 26 MAR 1985

ISBN Information

Print ISBN: 9780632012862

Online ISBN: 9781444303797

SEARCH

Keywords:

  • relationship of fluviodeltaic facies to coal deposition in lower front union formation – south-western North Dakota;
  • facies analysis;
  • paleographic maps;
  • lenticular and sheet sands;
  • floodbasin deposits

Summary

Facies analysis of the Ludlow and Tongue River Members of the Palaeocene Fort Union Formation provides an understanding of the relationship between fluviodeltaic environments and associated coal deposition in the south-western Williston Basin. The Ludlow Member consists of high-constructive delta facies that interfinger with brackish-water tongues of the Cannonball Member of the Fort Union Formation. The lower part of the Ludlow Member was deposited on a lower delta plain that consisted of interdistributary crevasse and subdelta lobes. The upper part of the Ludlow Member was deposited in meander belts of the upper delta plain. The delta plain facies of the Ludlow Member is overlain by alluvial plain facies consisting of swamp, crevasse-lobe, lacustrine, and trunk meander belt deposits of the Tongue River Member. The Ludlow delta is believed to have been fed by fluvial systems that probably flowed from the Powder River Basin to the Williston Basin undeterred by the Cedar Creek Anticline. However, the evidence indicates that the Cedar Creek Anticline was prominent enough, during early Tongue River Member deposition, to cause the obstruction of the regional fluvial system flowing from the SW, and the formation of local drainage.

The Ludlow Member contains 18 coal beds in the area studied, of which the T-Cross and Yule coals are as thick as 4 m (12 ft). Abandoned delta lobes served as platforms where coals formed, which in turn, were drowned by mainly fresh water and subordinate brackish water. Repetition of deltaic sedimentation, abandonment, and occupation by swamp led to preservation of the T-Cross and Oyster coals in areas as extensive as 260 km2 (< 100 miles2).