Cayo Agua Fm

Period:

Neogene

Age Interval:

Pliocene (5.0-3.4 Ma) - Coates et al. (2005)

Province:
Bocas del Toro basin

Type Locality and Naming

The Cayo Agua Fm was named by Coates et al. (1992) for the island of the same name in the Bocas del Toro archipelago, that lies about 6 kms to the west of Toro Point, Valiente Peninsula (Figure 1). The formation is well exposed along the east coast. Coates et al. (2005)

A detailed section measured on Cayo Agua has revealed that the stratotype is slightly more complex structurally than indicated by Coates et al. (1992). The stratotype for the formation (Section 19 in Coates (1999)) is now calculated to be slightly thinner because a small block immediately to the south of Nispero point is rotated to dip to the northeast and repeats a portion of the section (Section 20 in Coates (1999)). The defined stratotype (Section 19 in Coates (1999) runs from just south of North Point along the east coast southward to Nispero Point, and then from the northernmost to the southernmost exposures on the coast surrounding Tiburon Point. Additional reference sections described by Coates (1999) are Section 16, immediately west of North Point; Section 18, north of Red Rock Point; and Section 17, on the south coast immediately west of Red Rock Point.

[Figure 1. Geological map of Cayo Agua Island. Coates et al. (2005)]

Synonym:

Lithology and Thickness

The Cayo Agua Fm is distinguished lithologically as a pervasively bioturbated gray blue, muddy, silty lithic sandstone with common horizons of abundant thick shelled mollusks and ahermatypic corals. Occasional horizons of pebble conglomerate and very coarse-grained volcaniclastic sandstone are common in the middle of the formation. Compared to the Shark Hole Fm and Escudo De Veraguas Fm, the Cayo Agua Fm is consistently coarser-grained, with common basalt grains and granules, phosphatic pebbles, and wood fragments. A distinctive marker bed of packed ahermatypic corals occurs near the top of the formation and is well exposed at Tiburon Point and the unnamed point to the south (Coates et al. (2005)). In addition, the mollusks and corals in the Cayo Agua Fm are larger and more heavily calcified than those of the Shark Hole Fm and Escudo De Veraguas Fm. Evidence from benthic foraminifera (Collins (1993)) confirms the inference from grain size and fauna that the Cayo Agua Fm represents a more shallow-water facies than either the Shark Hole Fm or Escudo De Veraguas Fm. It represents onshore and offshore siliciclastic shelf sediments deposited at paleo-bathymetries of 10-80 m and 100-150 m respectively (Todd & Collins (2005))

Thickness: 293 m according to Section 19 in Coates (1999).

The stratigraphic order of the Tobabe Sandstone Fm, Nancy Point Fm and Shark Hole Fm (three of the five formations which make up the Bocas Del Toro Gr) has been determined by physical superposition. The two remaining formations of the Bocas Del Toro Gr (Escudo De Veraguas Fm and Cayo Agua Fm) as well as the younger Pleistocene Swan Cay Fm are known only on islands and their position relative to the other units has been determined by biostratigraphic evidence (Figure 2). The age of the Cayo Agua Fm is dated at the base ∼5.0-3.5 Ma and at the top 3.7-3.4 Ma, which suggests it is a contemporary, shallow water equivalent of the Shark Hole Point Fm and the lowermost part of the Escudo De Veraguas Fm.

[Figure 2. Correlation of measured sections in the Bocas del Toro Basin. Coates (1999). (Reproduced with permission of the Paleontological Research Institution, Ithaca, New York)]

Lithology Pattern:

Siltstone

Relationships and Distribution

Lower contact

The Cayo Agua Fm is equivalent in age to the upper part of the Shark Hole Point Fm and the lower part of the Escudo De Veraguas Fm and represents a shallower water facies. No contacts are known.

Upper contact

No contacts are known.

Regional extent

Valiente Peninsula (Figure 1). The formation is well exposed along the east coast.

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[-82.05,9.183],[-82.029,9.172],[-82.008,9.154],[-82.005,9.145],[-82.009,9.134],[-82.024,9.128],[-82.035,9.129],[-82.054,9.142],[-82.067,9.152],[-82.062,9.162],[-82.057,9.176],[-82.05,9.183]]]]}}

Fossils

Wood fragments, Corals, Mollusks (Figure 3) (Vermeij, 1988), Crabs (Todd & Collins (2005) suggest burial of whole crabs in gravity flows). Landau et al. (2011 & 2012b) study the Strombus and Cancellariidae gastropods from the Cayo Agua Fm. According to O'Dea et al. (2007), the best localities to collect fossils from the Cayo Agua Fm are from the faces of the cliffs and fallen blocks of rocks in Punta Tiburon (9º 9.11’N, 82º 1.427’W), Punta Piedra Roja (9º 8.364’N, 82º 1.004’W), and Punta Norte (9º 10.493’N, 82º 2.545’W), where fresh material can always be found.

[Figure 3. Representative fossils of the Cayo Agua Fm, Bocas del Toro. Nicely preserved shells of the herbivorous Strombus sp. (top left). Species of the predator gastropod Conus sp. (top right). The filtering bivalve Anadra (Arcidae family) (bottom left). An ahermatipic coral (which lives without symbiotic algae) of the family Caryophyllidae (bottom right). Scale = 2cm. O’Dea et al. (2007)]

Age

Age Span:

Beginning stage:

Zanclean

Fraction up in beginning stage:

Beginning date (Ma):

5.34

Ending stage:

Piacenzian

Fraction up in the ending stage:

Ending date (Ma):

3.60

Depositional setting

Shallow water facies

Depositional pattern:

Additional Information

References: Olsson (1922); Jung (1989); Cairns (1995); Collins et al. (1999a & 1999b); Coates (1999); Coates et al. (2005) ; Todd & Collins (2005); O'Dea et al. (2007); Beu (2010); Landau et al. (2012b) ; Schwarzhans et al. (2013); Aguilera et al. (2016).

Compiler:

Jacques LeBlanc (2021), Stratigraphic Lexicon: The Onshore Cenozoic Sedimentary Formations of The Republic of Panama. Biosis: Biological Systems, 2(1), 173 pp. https://doi.org/10.37819/biosis.002.01.0095 (or via https://sites.google.com/site/leblancjacques)