The La Toca Formation is a geologic formation in the northern and eastern part of the Dominican Republic. The formation, predominantly an alternating sequence of marls and turbiditic sandstones, breccias and conglomerates, is renowned for the preservation of insects and other arthropods in amber, known as Dominican amber. The formation is dated to the Burdigalian to Langhian stages of the Miocene period (Hemingfordian in the NALMA classification).[1]
| La Toca Formation | |
|---|---|
| Stratigraphic range: Burdigalian-Langhian (Hemingfordian) ~ | |
| Type | Formation |
| Underlies | La Jaiba Conglomerate, Villa Trina Formation |
| Overlies | Los Hidalgos Formation |
| Lithology | |
| Primary | Sandstone, marl, conglomerate, breccia |
| Other | Dominican amber |
| Location | |
| Coordinates | 19°12′N 69°18′W / 19.2°N 69.3°W |
| Approximate paleocoordinates | 19°00′N 68°06′W / 19.0°N 68.1°W |
| Region | Duarte, Hermanas Mirabal, Puerto Plata Province, Samaná Province & La Vega Provinces |
| Country |  Dominican Republic |
| Extent | Cordillera Septentrional, Cordillera Central |
| Type section | |
| Named for | La Toca mine |
| Named by | Redmond |
| Year defined | 1982 |
  La Toca Formation (the Dominican Republic) | |
Description edit
La Toca Formation was first defined by Redmond in 1982.[2] The formation mainly consists of marls and turbiditic sandstones and conglomerates deposited in the northeastern part of Hispaniola.[3] The formation overlies the Los Hidalgos Formation and is overlain by the La Jaiba Conglomerate and in places by the Villa Trina Formation.[4] It is laterally and time-equivalent with the Altamira and Luperón Formations and the Agua Clara Unit.[5]
- Esperanza
In the vicinity of Esperanza,[6] La Toca Formation is cropping out in the northeast of the geologic map, while it is also present in the neighboring municipalities of Imbert and San Francisco Arriba. The formation in this area comprises rhythmic alternations of ochre fine-to-medium-grained, locally grading to course-grained sandstones and greyish clayey and ochre marls. This succession is locally cut by meters thick microconglomerates and conglomerates with rounded and subrounded clasts. Analysis of the clasts in San Francisco Arriba shows the clasts consist of up to ten percent of volcanic rock fragments, mainly limestone fragments (23-42%), quartz (8-33%), chert of up to five percent and minor metamorphic rock fragments. The matrix which comprises about a quarter of the volume is micritic.
The formation is in this area poor in microfossils, although foraminifera of Catapsydrax af. dissimilis, Globigerinoides trilobus, Globigerina sp., Globorotalia sp., Cibicides sp., Brizalina sp., Reophax sp., ?Cassidulina sp. and Pirgo sp. have been found in the succession.[6]
Turbidite deposition moved to the northeast during the Miocene.[7]
Tectonics and depositional environment edit
La Toca Formation is in places inverted and put in contact with the San Marcos Formation along the Camú Fault.[8] The Septentrional Fault bounds the formation to the south.[9]
Individual outcrops edit
The formation crops out in the provinces Puerto Plata and Hermanas Mirabal.[10][11][12]
- Puerto Plata
In Puerto Plata Province, two sections of La Toca Formation are visible. The type section along the Bajabonico River shows volcaniclastic breccias with clasts originating from the Pedro García Formation. The breccias are poorly stratified and contain angular clasts of vesicular basalts and andesites, polymictic conglomerates of various provenance and chlorite-rich feldspathic arenites. This sequence is overlain by bluish-grey marls and black silty shales with conglomeratic intercalactions.[10]
A second outcrop in Puerto Plata shows a less typical debris flow setting, with a varied sedimentological character.[11]
- Hermanas Mirabal
The section of La Toca Formation in Hermanas Mirabal Province displays a thick series of matrix supported conglomerates. The clasts of these massively bedded conglomerates are characterized by two main lithology types; tuff and limestone. The limestone clasts are dark grey and white, where the light colored limestones contain carbonate platform fauna including corals. The clasts are well-rounded and medium-sized. The succession increases upwards in bedding thickness where limestone clasts become more dominant, larger in size and more angular. The total visible thickness of the succession is approximately 100 metres (330 ft).[12]
The sequence of conglomerates and provenance of the clasts point to sedimentation in a deltaic to shallow marine environment, where the clasts were transported by fluvial systems in the hinterland.[12]
Paleontological significance edit
La Toca mine of La Toca Formation
La Toca Formation is one of the formations of the Dominican Republic where Dominican amber is found. The amber is known for the many types of insects and other arthropods it contains and even mammalian hair, a leptodactylid frog and a gilled mushroom have been discovered in the Dominican amber.[13] Decades of study have led to an increased understanding of the invertebrate terrestrial fauna of the subtropical Early Miocene. Several genera have been described on the basis of these inclusions in resin from the fossil Hymenaea protera tree and the many fossils found in the amber provided a unique insight in the paleobiology of the Caribbean of the time. Of the 82 genera of spiders in Dominican amber, one third are extinct and about thirty percent are congeneric with extant taxa.[14]
Fossil content edit
The following fossils have been found in the formation:
See also edit
- List of fossiliferous stratigraphic units in the Dominican Republic
- El Mamey Formation - Dominican amber formation of the Dominican Republic
- Yanigua Formation - Dominican amber formation of the Dominican Republic
- Thomonde Formation - Early Miocene formation of Haiti
- Lagunitas Formation - Burdigalian fossiliferous formation of Cuba
- Cucaracha Formation - Burdigalian to Langhian fossiliferous formation of Panama
- Castillo Formation - Burdigalian fossiliferous formation of Venezuela
- Honda Group - Langhian fossiliferous formation of Colombia
References edit
- ^ La Toca Formation at Fossilworks.org
- ^ Hoja de Esperanza - 6074-IV, 2010, p.20
- ^ Díaz de Neira, 2017, p.663
- ^ Hoja de Puerto Plata - 6075-II, 2010, p.105
- ^ Hoja de Esperanza - 6074-IV, 2010, p.18
- ^ a b Hoja de Esperanza - 6074-IV, 2010, pp.37-39
- ^ Hoja de Esperanza - 6074-IV, 2010, p.99
- ^ Hoja de Puerto Plata - 6075-II, 2010, p.100
- ^ Díaz de Neira, 2017, p.662
- ^ a b (in Spanish) Museo Virtual - Geositio Puerto Plata type section - SGN
- ^ a b (in Spanish) Museo Virtual - Geositio Puerto Plata - SGN
- ^ a b c (in Spanish) Museo Virtual - Geositio Hermanas Mirabal - SGN
- ^ Henwood, 1992, p.902
- ^ Poinar, 2010, p.27
- ^ a b El Valle at Fossilworks.org
- ^ a b Golub & Popov, 2000
- ^ a b c d La Toca mine (AMNH coll) at Fossilworks.org
- ^ a b c d Davis & Engel, 2006
- ^ Heikkilä et al., 2018
- ^ a b c d e f g h i La Toca mine (Poinar coll) at Fossilworks.org
- ^ a b c d e f g h i Nel et al., 2006
- ^ Poinar, 2006
- ^ Poinar & Brown, 1993
- ^ a b c d La Bucara mine (Poinar coll) at Fossilworks.org
- ^ a b c d Poinar, 2011
- ^ a b El Valle locality (Poinar coll) at Fossilworks.org
- ^ a b Mohrig & Röschmann, 2005
- ^ a b La Toca mine (SMF coll) at Fossilworks.org
- ^ a b Johnson et al., 2001
- ^ La Vega group of mines (AMNH coll) at Fossilworks.org
- ^ Grimaldi et al., 1993
- ^ a b Ron Cauble coll at Fossilworks.org
- ^ a b Poinar, 2009
- ^ a b El Valle locality (MCZ coll) at Fossilworks.org
- ^ a b Wilson, 1985
- ^ De Andrade & Urbani, 1999
- ^ a b La Bucara mine (Manchester coll) at Fossilworks.org
- ^ a b Penney et al., 2012
- ^ Los Cacaos (INHS coll) at Fossilworks.org
- ^ Mockford & García Aldrete, 2014
Bibliography edit
- General geology
- Díaz de Neira, J.A.; J.C. Braga; F. Pérez Cerdán, and E. Lopera. 2017. Las terrazas marinas del Promontorio de Cabrera (Pleistoceno, norte de la República Dominicana). Boletín Geológico y Minero 128. 657–674. Accessed 2019-02-07.
- Dominican amber
- De Andrade, Maria, and Cesare Urbani. 1999. Diversity and adaptation in the ant genus Cephalotes, past and present (Hymenoptera, Formicidae). Stuttgarter Beiträge zur Naturkunde. Serie B (Geologie und Paläontologie) 271. 548–549. Accessed 2019-02-08.
- Davis, S.R., and M.S. Engel. 2006. A weevil of the genus Caulophilus in Dominican amber (Coleoptera: Curculionidae). Polskie Pismo Entomologiczne 75. 101–104. Accessed 2019-02-07.
- Golub, V.B., and Y.A. Popov. 2000. New Cenozoic lace bugs (Heteroptera: Tingidae). Paleontological Journal 34. S290–S297. Accessed 2019-02-07.
- Grimaldi, D.A.; C. Michalski, and K. Schmidt. 1993. Amber fossil Enicocephalidae (Heteroptera) from the Lower Cretaceous of Lebanon and Oligo-Miocene of the Dominican Republic, with biogeographic analysis of Enicocephalus. American Museum Novitates 3071. 1–30. Accessed 2019-02-07.
- Heikkilä, Maria; John W. Brown; Joaquin Baixeras; Wolfram Mey, and Mikhail V. Kozlov. 2018. Re-examining the rare and the lost: a review of fossil Tortricidae (Lepidoptera). Zootaxa 4394(1). 41–60. Accessed 2019-02-07.
- Henwood, Alison A. 1992. Soft-part preservation of beetles in Tertiary amber from the Dominican Republic. Palaeontology 35. 901–912. Accessed 2019-02-07.
- Johnson, C.; D. Agosti; J.H. Delabie; K. Dumpert; D.J. Williams; M. Tschirnhaus, and U. Maschwitz. 2001. Acropyga and Azteca ants (Hymenoptera: Formicidae) with scale insects (Sternorrhyncha: Coccoidea): 20 million years of intimate symbiosis. American Museum Novitates 3335. 1–18. Accessed 2019-02-07.
- Mockford, E.L., and A.N. García Aldrete. 2014. A new genus and two new species, one extant and one fossil, in the family Troctopsocidae (Psocodea: 'Psocoptera': Troctomorpha: Amphientometae: Electrentomoidea). Zootaxa 3869. 159–164. Accessed 2019-02-07.
- Mohrig, W., and F. Röschmann. 2005. Sciarid flies from Dominican amber (Diptera, Sciaridae). Beiträge zur Entomologie 55. 319–361. Accessed 2019-02-07.
- Nel, A.; A. Waller, and G.O. Poinar. 2006. The first fossil Myopsocidae (Psocoptera) in Dominican amber. Zootaxa 1349. 63–68. Accessed 2019-02-07.
- Penney, D.; A. McNeil; D.I. Green; R.S. Bradley; J.E. Jepson; P.J. Withers, and R.F. Preziosi. 2012. Ancient Ephemeroptera-Collembola symbiosis fossilized in amber predicts contemporary phoretic associations. PLoS One 7. e47651. Accessed 2019-02-07.
- Poinar, George. 2011. A walking stick, Clonistria dominicana n. sp. (Phasmatodea: Diapheromeridae) in Dominican amber. Historical Biology 23. 223–226. Accessed 2019-02-07.
- Poinar, George. 2010. Palaeoecological perspectives in Dominican amber. Annales de la Société Entomologique de France 46. 23–52. Accessed 2019-02-07.
- Poinar, George. 2009. Dominibrentus leptus, n. gen., n. sp. (Curculionoidea, Brentidae, Cyphagoginae, Dominibrentini, n. tribe), a straight-snouted weevil in Dominican amber. Historical Biology 21. 51–55. Accessed 2019-02-07.
- Poinar Jr., G. 2006. Feroseta priscus (Neuroptera : Mantispidae), a new genus and species of mantidflies in Dominican amber. Proceedings of the Entomological Society of Washington 108(2). 411–417. Accessed 2019-02-08.
- Poinar, G.O., and J.W. Brown. 1993. A new fossil tortricid (Lepidoptera: Tortricidae) from Dominican amber. Insect Systematics & Evolution 24. 25–29. Accessed 2019-02-08.
- Wilson, E.O. 1985. Ants of the Dominican Amber (Hymenoptera: Formicidae) 3. The Subfamily Dolichoderinae. Psyche: A Journal of Entomology 92. 17–37. Accessed 2019-02-07.
Maps edit
- Ramírez Merino, José Ignacio et al. 2010. Mapa geológico de la República Dominicana - Escala 1:50.000 - Hoja Esperanza (6074-IV), 1–132. Servicio Geológico Nacional República Dominicana. Accessed 2019-02-07.
- Monthel, Jacques et al. 2010. Mapa geológico de la República Dominicana - Escala 1:50.000 - Hoja Puerto Plata (6075-II), 1–160. Servicio Geológico Nacional República Dominicana. Accessed 2019-02-07.
Further reading edit
- Engel, M.S., and D.A. Grimaldi. 2007. The neuropterid fauna of Dominican and Mexican amber (Neuropterida, Megaloptera, Neuroptera). American Museum Novitates 3587. 1–58. Accessed 2019-02-08.