Emergence and Evolution of Barbados
Emergence and Evolution of Barbados is a three-part analysis of the Quaternary geologic and geomorphologic evolution of the island of Barbados in the southeastern Caribbean. “Geology of Southeastern Barbados” assembles and integrates detailed observations into a complex 700 k.y. history of marine sculpting and riverine flooding processes. “Marine Terrace Evolution of Windward Barbados” revises the Quaternary stratigraphy of the island, describes the tectonics of emergence, and demonstrates that uplift rates vary by location. “Active Emergence, Chronology, and Limestone Facies in Southeastern Windward Barbados” is the first comprehensive study to integrate marine erosion and deposition with tectonic uplift rates. Major findings of this work are that Barbados’ Central Highlands are an erosional remnant, and that terraces originated principally by marine erosion rather than by reef construction.
Marine terrace evolution of windward Barbados
*Deceased: 1933–2003; published posthumously.
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Published:June 09, 2021
ABSTRACT
The geomorphic evolution of southeastern windward Barbados is embodied in the development of a terraced seaward island slope on a tectonically rising scarp. The island slope is wholly erosional and a product of marine and subaerial processes. Modulation of the slope by terraces has occurred fundamentally by marine erosion at eustatic stillstands but includes morphologic additions by limestone deposition. The ongoing phase of morphologic development and island emergence began at or before ca. 700 ka. Emergence has proceeded at an increasing rate northwestward along the island’s southeastern coastline. The terraced island slope is markedly affected by post-terrace denudation.
As many as eight marine terraces are preserved on the windward island slope below the planed surface of the Central Highlands, which is counted as terrace 1. Relics of an upper set of terraces are perched on the face of Second High Cliff, the ancient erosional margin of the oldest limestone capping Barbados. Second High Cliff developed by successive marine incisions over a probably long duration preceding oxygen isotope stage 9. A lower terrace set was excised in stages 9 through 5a in the siliciclastic island foundation or (and) in limestone cover of preceding terraces.
Marine terrace floors extend seaward from an erosional backcliff and shoreline angle to a younger erosional cutoff. The most broadly preserved terrace floors indicate the following systematic succession of seaward profile elements: narrow upper ramp; broad upper flat; lower ramp; and on one, a lower flat. Carbonate cover is chiefly clastic on the upper ramp and flat, and chiefly reefal on the lower ramp. Most shoal-water reefal facies appear to be in fringe reef blankets.
Terrace profile geometries are explained by a simple theory of wave abrasion in proportion to duration of sea level at a shoreline. At stillstands, the wave impact caused large shoreline recession and development of flats, whereas in transgression and regression, rapid sea-level change permitted only minor recession. Corresponding differences in cover facies are explained as functions of duration of breaking waves and seabed stability.
Widespread post-terrace denudation is attributed to floods of upland provenance, local overland flow, and marine flooding. Riverine processes have produced channelization and a high degree of terrace preservation on the interfluves in the steeper, foundation-based northern windward region. This differs markedly from the more diffuse, shallow gullying and stripping of the limestone-covered shallow slopes of the southern region. An intensely stormy spell is suggested between stages 5e and 5c.
- actinides
- Antilles
- Barbados
- carbonate rocks
- Caribbean region
- Cenozoic
- erosion
- eustasy
- isotopes
- landform evolution
- Lesser Antilles
- limestone
- marine terraces
- metals
- oscillations
- Quaternary
- radioactive isotopes
- sea-level changes
- sedimentary rocks
- shore features
- terranes
- Th-230
- thorium
- transgression
- uplifts
- West Indies
- Windward Islands