RECENT COASTAL SEDIMENTATION: CENTRAL LOUISIANA COAST.
Abstract
The Recent near-surface sediments of Vermilion, Iberia, and St. Mary Parishes, Louisiana, may be divided into two types: those sediments which were deposited by now abandoned Mississippi River distributaries and those carried along shore and deposited at the delta margins. Changes in delta position during the past 7000 years have resulted in an accumulation of cyclic deposits consisting of detrital sediments separated by in situ peat horizons. The physical, faunal, and floral properties obtained from a study of present-day surface sedimentary environments (natural levee, nearshore marine, mudflat, oyster reef, beach, marsh, brackish bay, lacustrine, and swamp) were used to interpret subsurface relationships and establish a stratigraphic section. Five laterally continuous peat horizons, now buried at depths ranging from 4 to 40 feet, were identified and indicate that a positive change of level had taken place since their formation. Abundant evidence for a stillstand in sea level during the past 2000 to 5000 years affords a fixed datum for differentiation between eustatic sea level rise and subsidence. The rate of subsidence in the study area is 0.24 foot per century. Using this rate, calculations reveal a eustatic sea level rise of approximately 23 feet in the interval from 7000 to 3650 years BP when stillstand was reached. There is no indication that sea level was higher than at present during the interval studied. Similar results were obtained by applying this method to published data on sea level changes in the Netherlands, Massachusetts, and Connecticut. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1966
- Accession Number
- AD0653092
Entities
People
- James M. Coleman
Organizations
- Louisiana State University