Geoscience Reference
In-Depth Information
in subsurface well logs. Van den Bold (1972), a noted biostratigrapher of Caribbean
ostracodes, disagreed with the revised stratigraphic interpretation of Woodring (1964)
by demonstrating that stratigraphic sections containing the E.L. and overlying sedi-
ments (i.e., La Boca Formation) were correlative with the Culebra Formation, based
on ostracode biostratigraphy. Specifically, his zones I and IIA of the “La Boca For-
mation” are correlative with the Culebra Formation (Figure 4). Later studies have
followed the stratigraphy as originally proposed by Woodring and Thompson (1949),
based on data gathered in support of the current study (Johnson and Kirby, 2006;
Retallack and Kirby, 2007).
Figure 4. Summary of stratigraphic nomenclature for the formations exposed along the Gaillard Cut
portion of the Panama Canal.
All of the stratigraphic models that have been proposed for the Gaillard Cut over
the past 100 years can be divided into two groups, which are herein called the (1) Culebra
model and the (2) La Boca model (Figure 5). The Culebra model places all of the
Culebra Formation (sensu Woodring and Thompson, 1949) underneath the Cucaracha
Formation (Escalante, 1990; MacDonald, 1919; Van den Bold, 1972; Woodring and
Thompson, 1949). The La Boca model, on the other hand, places the lower portion of
the Culebra Formation (sensu Woodring and Thompson, 1949) (marked by blue in Fig-
ure 5) into the La Boca Formation above the Cucaracha Formation (Graham et al., 1985;
Stewart et al., 1980; Woodring, 1964). As the upper portion of the Culebra Formation
(marked by purple in Figure 5) remains beneath the Cucaracha Formation in this mod-
el, the La Boca model considers the Culebra Formation of Woodring and Thompson
(1949) to actually be two different formations (i.e., Culebra and La Boca formations),
with the Cucaracha Formation lying between two (Figure 5). If the La Boca Formation
(marked by blue in Figure 5) is found to be younger than the Cucaracha Formation, then
 
Search WWH ::




Custom Search