Late Quaternary Shift of Mixed Siliciclastic-Carbonate Environments Induced by Glacial Eustatic Sea-Level Fluctuations in Belize

1999 ◽  
Author(s):  
C. Elmer Ferro ◽  
André W. Droxler ◽  
John B. Anderson ◽  
David Mucciarone
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Sea Level Fluctuations

The Origin of Modern Atolls: Challenging Darwin's Deeply Ingrained Theory

2021 ◽  
Vol 13 (1) ◽  
pp. 537-573 ◽  
Author(s):  
André W. Droxler ◽  
Stéphan J. Jorry
Keyword(s):  
Sea Level ◽  
Late Quaternary ◽  
Direct Interaction ◽  
Evolutionary Model ◽  
Reef Growth ◽  
Sea Level Fluctuations ◽  
Fringing Reefs ◽  
Volcanic Islands ◽  
Karst Model ◽  
The Tropical Pacific

In 1842, Darwin identified three types of reefs: fringing reefs, which are directly attached to volcanic islands; barrier reefs, which are separated from volcanic islands by lagoons; and ring reefs, which enclose only a lagoon and are defined as atolls. Moreover, he linked these reef types through an evolutionary model in which an atoll is the logical end point of a subsiding volcanic edifice, as he was unaware of Quaternary glaciations. As an alternative, starting in the 1930s, several authors proposed the antecedent karst model; in this model, atolls formed as a direct interaction between subsidence and karst dissolution that occurred preferentially in the bank interiors rather than on their margins through exposure during glacial lowstands of sea level. Atolls then developed during deglacial reflooding of the glacial karstic morphologies by preferential stacked coral-reef growth along their margins. Here, a comprehensive new model is proposed, based on the antecedent karst model and well-established sea-level fluctuations during the last 5 million years, by demonstrating that most modern atolls from the Maldives Archipelago and from the tropical Pacific and southwest Indian Oceans are rooted on top of late Pliocene flat-topped banks. The volcanic basement, therefore, has had no influence on the late Quaternary development of these flat-topped banks into modern atolls. During the multiple glacial sea-level lowstands that intensified throughout the Quaternary, the tops of these banks were karstified; then, during each of the five mid-to-late Brunhes deglaciations, coral reoccupied their raised margins and grew vertically, keeping up with sea-level rise and creating the modern atolls.

Quaternary depositional patterns and sea-level fluctuations, Northeastern North Carolina

2007 ◽  
Vol 67 (1) ◽  
pp. 83-99 ◽  
Author(s):  
Peter R. Parham ◽  
Stanley R. Riggs ◽  
Stephen J. Culver ◽  
David J. Mallinson ◽  
John F. Wehmiller
Keyword(s):  
North Carolina ◽  
Sea Level ◽  
Late Quaternary ◽  
Drainage System ◽  
Drill Hole ◽  
Estuarine Sediments ◽  
Early Pleistocene ◽  
Sea Level Fluctuations ◽  
Marine Deposits ◽  
Sea Level Oscillations

AbstractA detailed record of late Quaternary sea-level oscillations is preserved within the upper 45 m of deposits along an eight km transect across Croatan Sound, a drowned tributary of the Roanoke/Albemarle drainage system, northeastern North Carolina. Drill-hole and seismic data reveal nine relatively complete sequences filling an antecedent valley comprised of discontinuous middle and early Pleistocene deposits. On interfluves, lithologically similar marine deposits of different sequences occur stacked in vertical succession and separated by ravinement surfaces. Within the paleo-drainage, marine deposits are separated by fluvial and/or estuarine sediments deposited during periods of lowered sea level. Foraminiferal and molluscan fossil assemblages indicate that marine facies were deposited in a shallow-marine embayment with open connection to shelf waters. Each sequence modifies or truncates portions of the preceding sequence or sequences. Sequence boundaries are the product of a combination of fluvial, estuarine, and marine erosional processes. Stratigraphic and age analyses constrain the ages of sequences to late Marine Isotope Stage (MIS) 6 and younger (∼ 140 ka to present), indicating multiple sea-level oscillations during this interval. Elevations of highstand deposits associated with late MIS 5 and MIS 3 imply that sea level was either similar to present during those times, or that the region may have been influenced by glacio-isostatic uplift and subsidence.

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