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| Punaré Formation | |
|---|---|
| Name | Punaré Formation |
| Type | Geological formation |
| Period | Miocene |
| Primary lithology | Sandstone, marl |
| Otherlithology | Conglomerate, siltstone |
| Region | Herrera Province, Panama |
| Country | Panama |
| Underlies | Unconformity with younger units |
| Overlies | Gatuncillo Formation |
| Thickness | up to ~120 m |
| Namedby | Henry W. Menendez |
| Year ts | 1950s |
Punaré Formation is a Neogene stratigraphic unit exposed in Herrera Province, Panama that preserves marine and marginal-marine deposits. The formation is known for its sandstones, marls, and conglomerates and for yielding fossil assemblages that inform regional biostratigraphy and paleoenvironments. Punaré has been cited in discussions of the Panama Isthmus's geological evolution, the closure of the Central American Seaway, and Neogene faunal migrations.
The Punaré Formation crops out near the town of Parita and along the southern foothills of the Cordillera de Talamanca region in central Panama. Geological mapping by teams from Smithsonian Institution-affiliated researchers and regional surveys by Instituto Geológico y Minero de Panamá first characterized the unit during mid-20th century fieldwork. The formation sits stratigraphically above the older Gatuncillo Formation and beneath younger Neogene and Quaternary cover, sharing contacts with units examined in studies by G. Hubbell, A. Woodring, and later researchers affiliated with University of Panama.
Punaré comprises medium- to coarse-grained, cross-bedded sandstones intercalated with fossiliferous marls and localized conglomeratic beds. Petrographic studies correlate clast compositions with provenance from uplifted segments of the Central American Volcanic Arc and reworked material linked to erosion of the Panamanian Block. Stratigraphic sections measured near Las Minas and Santiago de Veraguas show an overall coarsening-upward trend with channelized conglomerates interpreted as fluvial to deltaic distributary deposits. Regional correlation uses marker beds tied to lithostratigraphic frameworks developed by U.S. Geological Survey teams and comparative sections in Costa Rica and Colombia.
Biostratigraphic indicators and radiometric constraints place Punaré in the early to middle Miocene, broadly overlapping with regional units dated in studies by O. P. Hay and later calibrated using isotopic work from Argon-argon dating laboratories at California Institute of Technology collaborators. Depositional interpretations favor shallow marine, estuarine, and delta-front environments influenced by changing sea levels and rapid tectonic uplift associated with the collision between the Caribbean Plate and the Panamanian microplate. Sequence-stratigraphic analyses link Punaré transgressive-regressive cycles with global eustatic events recognized in comparisons to sequences from the Mediterranean Basin and the Gulf of Mexico.
Punaré preserves diverse marine fossils including benthic foraminifera, mollusks (bivalves and gastropods), and occasional vertebrate remains. Molluscan assemblages show affinities to Miocene faunas described by W. P. Woodring and have been compared to collections cataloged at the Smithsonian National Museum of Natural History and the Natural History Museum, London. Foraminiferal biostratigraphy employs zonations developed by A. H. Hedley and adapted by Central American micropaleontologists to refine age models. Isolated teeth and bone fragments attributed to marine mammals have triggered comparisons with Miocene cetacean records from Peru and Venezuela, while shark teeth similarities recall taxa documented by L. D. Springer and field teams from Florida Museum of Natural History.
The sand-prone units of the formation function as local aquifers exploited by municipal wells serving communities such as Parita and Pesé, and their porosity-permeability attributes have been evaluated in hydrogeological assessments by the Panama Canal Authority and regional water agencies. Conglomeratic horizons have been investigated for aggregate resources by Ministry of Commerce and Industries (Panama) engineers. Geologically, Punaré contributes to models of Isthmus of Panama emergence that affect interpretations of Neogene oceanographic changes central to paleoclimate reconstructions conducted by teams from Woods Hole Oceanographic Institution and paleoceanographers at Scripps Institution of Oceanography.
Initial descriptions of Punaré trace to reconnaissance mapping by Henry W. Menendez in the 1950s with subsequent systematic study by Alfredo Bedoya and collaborators from Universidad de Panamá during the 1970s. Later refinements of lithostratigraphy and paleontology were published by researchers associated with the Smithsonian Tropical Research Institute and joint projects with the U.S. Geological Survey and Panama Geological Service. Modern work integrates sedimentology, paleontology, and geochronology by international teams led from institutions including University of California, Berkeley, University of Florida, and Universidad de los Andes (Colombia) to situate the unit within broader Central American Neogene frameworks.
Category:Geologic formations of Panama