Fining-Upward Lithostratigraphy of a Modern Muddy Coastline Deposit from Suriname, South America—a Record of Sea Level Fluctuations and Longshore Mud Transport*

By

James M. Rine¹

Search and Discovery Article #50018 (2005)

Posted September 27, 2005

*Oral presentation at AAPG Annual Convention, with SEPM, Calgary, Alberta, June 19-22, 2005

Click to view presentation in PDF format.

¹OMNI Laboratories, Inc, Houston, TX ([email protected])

Abstract

The lithostratigraphy of the Holocene coastal plain of Suriname records not only the two main processes of transgression and longshore transport of muddy sediments from the Amazon River but also fluctuations in both these processes. Overall the Holocene coastal plain stratigraphy of Suriname, up to 24m thick, consists of three distinct lithologies:

1)      Peat-rich mud deposited 9000 to 7000 BP

2)      Sandy mud deposited 6000 to 3500 BP

3)      Silty clay with surface cheniers deposited after 3500 BP.

The peat-rich unit, which unconformably overlies stiff, oxidized Pleistocene clays, is an onlapping unit that records the landward retreat of mangrove swamps in response to a rising sea level. The sandy mud unit records a typical coarsening upward, prograding coastal sequence that probably was terminated by a rapid lowering in sea level followed by infusion of longshore-transported muds from the Amazon. The top unit of the Holocene accumulation consists of silty clays with isolated surface sand cheniers. This predominantly mud unit, which is accumulating today, was deposited by 10 km–scale migrating mud banks separated by interbank zones of erosion. The relative rate of mudbank deposition versus interbank erosion may be controlled by minor sea level fluctuations, sediment output from the Amazon River, or alteration of shelfal oceanographic processes. The deciphering of this lithostratigraphic record not only pertains to the Holocene coastal plain of Suriname but also to other modern and ancient coastal deposits where sedimentary record of erosion and deposition are generally attributed to major fluctuations in sea level.

       Location map

      Suriname and Guiana coastal stratigraphy