La Peñita Fm

Period:

Neogene

Age Interval:

Pliocene (Zanclean) - Cortés et al. (2019)

Province:
Burica Peninsula

Type Locality and Naming

Coryell et al. (1942) believe it to correlate with the Charco Azul Fm. Corrigan et al. (1990), originally named the “Charco Azul Gr” as the “Charco Azul Fm” as well as its three Members “La Peñita”, “Burica” and “Armuelles”. It is only later that it was renamed as a Group, while each of its members were given the designation of “Formation”.

The Stratotype of the “La Peñita” Fm is located along the La Peñita river (8 ° 14.283'N, 82 ° 57.852'W) on the Burica Peninsula (Chiriqui Province). On that same Peninsula, the formation also outcrops along La Peña river (8º 12.794'N, 82º 56.820'W) (Figure 046). The formation can also be found at least at one location in the Osa Peninsula in Costa Rica. Coates et al. (1992)
The La Peñita Fm (basal formation of the Charco Azul Gr) is coarse with locally channelled conglomerates, some of which form a distinctive suite defined as the La Vaca Member by Coates et al. (1992).

Synonym: La Penita Fm; “Peñita Member”; “Peñitas Fm”; Peñitas Fm”; See “Charco Azul Gr” for some additional comments on synonymy. La Vaca Fm (Synonym of La Vaca Member).

Lithology and Thickness

It is mainly composed of limolite with sutures of conglomerate (Olsson (1942a)). Clayey, bluegreen siltstone and litharenite consistently rich in benthic and planktic foraminifers, deposited in a forearc slope environment. This basal formation is coarse with locally channelled conglomerates, some of which form a distinctive suite defined as the La Vaca Member. These coarse deposits record a detrital paralic and fan-delta depositional environment at the base of the Charco Azul Gr. Coates et al. (1992)

Thickness: 1200m

[Figure 104. Stratigraphic column of the Charco Azul Gr showing the location of the “La Vaca” Member within the “La Peñita” Fm according to Coates et al. (1992). Modified from Morell et al. (2011).]

Lithology Pattern:

Clayey limestone

Relationships and Distribution

Lower contact

Cretaceous Seamount Complex

Upper contact

Burica Fm (Figure 046), also part of the Charco Azul Gr

Regional extent

On Burica Peninsula, Chiriqui Province.

GeoJSON

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Fossils

Locally rich in mollusks and other fossils that suggest deposition occurred in a shallow water coastal environment. For example, cirripeds, typically living in intertidal and subtidal conditions, are common, and numerous spines of the echinoderm Eucidaris can be found; these usually live in areas exposed to strong waves (Figure 103). Filtering mollusks such as Arca and Chione dominate but predatory gastropods such as Olivella, Conus and Cancellaria are also common. The distribution of these mollusks today also suggest that the La Peñita Fm was deposited in a shallow coastal sea. Coates et al. (1992)

[Figure 103. Representative fossils of the La Peñita Fm. Spines and plates of the marine/inter-tidal echinoderm Eucidaris sp., known as the sea urchin "Pencil point" (top left). The carnivorous gastropod Terebra sp. (family Terebridae) (top right). The Anadara bivalve (family Arcidae) (bottom left). The predator gastropod Cancellaria (family Cancellariidae) (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 coastal sea

Depositional pattern:

Additional Information

References: Coryell et al. (1942); Olsson (1942a); Obando (1986); Coates et al. (1992); Kolarsky (1992); Kolarsky et al. (1995a, 1995b); Schlegel (1996); O’Dea et al. (2007); Morell et al. (2011); Cortés et al. (2019);

Relevant documents discussing the La Vaca Member:

Woodring (1960). A «tentative » undefined formation name of unknown origin for strata, referred to middle Miocene on unspecified grounds, in the Burica Peninsula, Chiriqui Province.
Keroher et al. (1966); An undefined formation name. Miocene(?).
Coates et al. (1992) rename it “La Vaca Member” of the La Peñita Fm.
Morell et al. (2011)

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)