Darien Fm

Period:

Paleogene

Age Interval:

Middle Eocene to Oligocene - Barat et al. (2014)

Province:
Eastern Panama

Type Locality and Naming

Esso Exploration and Production Panama (1970, 1971a, 1971b) estimated its thickness as between 500 m and 1500 m.

Occurs on the northeastern flank of the Chucunaque–Tuira Basin, in the fore-arc region and in the Majé Massif.

Synonym: Eocene units of the Darien Fm were first referred to as the Morti Tuffs, and Oligocene units (occurring only in the southwest of the Chucunaque-Tuira Basin) as the Pacific Tuffs (Bandy (1970); Bandy and Casey (1973)).

Lithology and Thickness

It consists dominantly of fine and medium tuff, agglomerate, radiolarian chert, and basalt in its lower part and of calcareous and siliceous mudstone, micritic calcarenite, and volcaniclastics in its upper part. Radiolaria indicate mostly early to middle Eocene deposition at bathyal depths on the southwestern flank of the Chucunaque Basin (Bandy and Casey (1973)).
In the Majé massif, its stratigraphy and composition is described with (from oldest to youngest) abundant breccia and agglomerate, wackestone, blackish volcaniclastic sandstone, conglomerate (Figure 1), chert (Figure 2), dark green fine-grained and medium grained tuff, green pebble conglomerate and fine sandstone. In the upper part of this sequence, the rounded pebbles suggest a distant clastic source, such as the San Blas–Darien Massif. The abundance of Globigerina sp. fossils in the sandstone indicates an open pelagic marine paleo-environment. A calcareous unit, with conglomerate, black sandstone and gray to white medium-grained tuff unconformably overlies the oldest volcaniclastic unit of the Darien Fm. This calcareous unit suggests a hemi-pelagic depositional environment, and the nannofossil assemblages indicate a Late Oligocene–Early Miocene age (Figure 3; Figure 4). This calcareous unit could correspond to the old Aquaqua Fm, which was first named by Shelton (1952), and which is now referred to as the Aquaqua Member of the Darien Fm. Barat et al. (2014)

Thickness: up to ~ 1500 m

[Figure 1. Conglomerates with green weathered andesite pebbles in the Majé Massif, Darien Fm (8.93588°, −78.55220°, WGS84). Barat (2013) and Barat et al. (2014).]

[Figure 2. Green and red siliceous azoic cherts in the Majé Massif, Darien Fm (8.93013°, −78.56126°, WGS84). Barat (2013) and Barat et al. (2014).]

[Figure 3. Gray and white fine-grained and medium-grained calcareous tuffs of the Late Oligocene, Aquaqua Mb, Darien Fm, (8.89477°, −78.52817°, WGS84); Barat (2013) and Barat et al. (2014).]

[Figure 4. Layered micritic limestone outcrop in the Curti river of the Majé Massif, Late Oligocene. Barat (2013).]

Lithology Pattern:

Volcanics

Relationships and Distribution

Lower contact

The formation is usually faulted against or nonconformably overlies the igneous basement of the San Blas Fm.

Upper contact

The formation is unconformably overlain by either the Porcona Fm or the Clarita Fm.

Regional extent

Eastern Panama

GeoJSON

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Fossils

See the “lithology” section.

Age

Age Span:

Beginning stage:

Lutetian

Fraction up in beginning stage:

Beginning date (Ma):

48.07

Ending stage:

Rupelian

Fraction up in the ending stage:

0.667

Ending date (Ma):

29.49

Depositional setting

The abundance of Globigerina sp. fossils in the sandstone indicates an open pelagic marine paleo-environment. The calcareous unit suggests a hemi-pelagic depositional environment

Depositional pattern:

Additional Information

References: Esso Exploration and Production Panama (1970, 1971a, 1971b); Bandy (1970); Bandy and Casey (1973); Ministerio de Comercio e Industrias (1991); Coates, Anthony G. et al. (2004); (APP-B4 and APP-B3); Barat et al. (2014);
In the Majé Massif, mesocratic to leucocratic dykes and andesites to dacites cross-cut the San Blas Complex Fm and the Darien Fm. These andesitic dykes are fine grained with phenocrysts of amphiboles and plagioclases. A few dacitic dykes are rich in quartz and show flow structures (Barat et al. (2014)).

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)