The paradoxical occurrence of oolitic limestone on the eastern islands of Great Bahama Bank: where do the ooids come from? - Perspectives in Carbonate Geology - page 111

The paradoxical occurrence of oolitic limestone on the eastern
islands of Great Bahama Bank: where do the ooids come from?

PASCAL KINDLER * and ALBERT C. HINE †
* Section of Earth Sciences, University of Geneva, Maraîchers 13, 1205 Geneva, Switzerland (E-mail: Pascal.
[e-mail])
† Coastal Planning and Engineering Inc, Tampa Bay Regional Offi ce, 101 16th Ave So. Suite 4, St Petersburg, FL
33701, USA

ABSTRACT

The origin of the ooids forming the bulk of many large Pleistocene and Holocene ridges
on the windward islands of Great Bahama Bank is not well understood. A formation
locus situated to the east of these islands would be consistent with present-day
sediment fl uxes, but outer platforms in these areas are extremely narrow today
and appear unsuitable for large-scale ooid production. The four models presented
suggest that ooids could originate (1) from these narrow outer platforms, (2) from wider
outer platforms that no longer exist, (3) from the bank interior via tidal channels, and (4)
directly from the bank interior by means of a westerly sediment fl ux. With the excep-
tion of option 3, all models are validated by fi eld observations in Eleuthera and in the
Exumas. Corroboration of models 2 (outer platform erosion) and 4 (westerly fl ux) fur-
ther indicates that past depositional environments and sedimentary processes on Great
Bahama Bank could have been signifi cantly different from those operating today.

Keywords Great Bahama Bank, Eleuthera, Exumas, Quaternary, ooids, oolites,
aeolianites.

INTRODUCTION

The main lesson that the fi rst author learned from
R.N. Ginsburg during his tenure at the University
of Miami in the early 1990s was that the funda-
mental duty of a scientist is to constantly pose
pertinent questions to himself and to others.
One of the questions raised by Ginsburg, at that
time, was about the paradoxical occurrence of
extensive Pleistocene oolites on the windward
islands of Great Bahama Bank (GBB; Fig. 1).
The petrographic composition of these ridges
is, indeed, peculiar because there is no obvious
source of ooids, unless sediment fl uxes were
opposite to those operating today. This paradox
is addressed in the following sections after a brief
review of the formation of ooids on GBB, of the
sediment transport vectors in the Bahamas, and of
the surfi cial geology of the windward islands.

N

Fig. 1. Geographical situation of the Great Bahama
Bank (GBB). The occurrence of islands (Eleuthera, Cat,
Exumas, Long) on the eastern margin of GBB is probably
related to the prevailing easterly winds. JC = Joulters Cays,
NPI = New Providence Island, TOTO = Tongue of the
Ocean, SC = Schooners Cays.

SETTING

that conditions required for the optimal production
of Bahamian ooids (i.e. aragonitic ooids with a
tangential crystal structure) are: (1) the presence
of sedimentary particles that can serve as nuclei;
(2) a fl at topography where these particles can

Ooid production on Great Bahama Bank

The vast majority of authors (Newell et al. , 1960;
Richter, 1983; Scholle & Ulmer-Scholle, 2003) agree