La Toca Formation Explained

La Toca Formation
Type:Formation
Age:Burdigalian-Langhian (Hemingfordian)
~
Period:Langhian
Prilithology:Sandstone, marl, conglomerate, breccia
Otherlithology:Dominican amber
Namedfor:La Toca mine
Namedby:Redmond
Year Ts:1982
Region:Duarte, Hermanas Mirabal, Puerto Plata Province, Samaná Province & La Vega Provinces
Coordinates:19.2°N -69.3°W
Paleocoordinates:19°N -68.1°W
Underlies:La Jaiba Conglomerate, Villa Trina Formation
Overlies:Los Hidalgos Formation
Extent:Cordillera Septentrional, Cordillera Central

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]

Description

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]

EsperanzaIn 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

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

The formation crops out in the provinces Puerto Plata and Hermanas Mirabal.

Puerto PlataIn 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 MirabalThe 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 100m (300feet).

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

See also: Dominican amber. 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

The following fossils have been found in the formation:

Group Fossil Location Notes
Brachypogon (Isohelea) dominicanus El Valle [15] [16]
Forcipomyia (Lepidohelea) sp.
Forcipomyia (Lepidohelea) antilleana
Forcipomyia (Lepidohelea) chrysosuccinea
Forcipomyia (Lepidohelea) domibicolor
Miomyia
Protortalotrypeta grimaldii
Archicratyna arcana
Procolobostema roseni
Forcipomyia (Forcipomyia) sp. La Toca mine [17] [18]
Procolobostema roseni
Antiquatortia histuroides align=center [19]
Culex malariager La Toca mine (Poinar coll)
Dominimyza tanyacaena
Diceratobasis worki
Feroseta prisca align=center [20]
Polyvena horatis align=center [21]
Enischnomyia stegosoma La Bucara mine (Poinar coll) align=center
Archicratyna arcana El Valle locality (Poinar coll) align=center [22] [23]
Leptopharsa evsyunini El Valle align=center
Enicocephalus omen La Toca mine
Enicocephalus seniculus
Enicocephalus subvitreus
Amnestus electricus
Empiploiariola inermis
Prisciba dominicana La Toca mine (Poinar coll) [24] [25]
Apicrenus fossilis
Praecoris dominicana
Panstrongylus hispaniolae
Schizoptera dominicana
Electromyrmococcus abductus La Toca mine (SMF coll) [26] [27]
Acropyga sp.
Minyscapheus dominicanus La Bucara mine (Poinar coll) [28] [29]
Prisciba serrata
Hypselosoma dominicana
Schizoptera hispaniolae
Enicocephalus prius La Vega group of mines (AMNH coll) align=center [30] [31]
Electrobates spinipes El Valle locality (Poinar coll) align=center
Okamninus annae La Toca mine
Caulophilus ashei
Electroborus brighti
Bicalcasura maculata La Bucara mine (Poinar coll) align=center
Dominibrentus leptus Ron Cauble coll align=center
Pseudomyrmex antiquus La Toca mine (Poinar coll)
Wanderbiltiana wawasita
Technomyrmex hispaniolae El Valle locality (MCZ coll) [32] [33]
Proceratium gibberum
Cephalotes integerrimus [34]
Proanaxipha latoca La Toca mine (Poinar coll)
Anaxipha dominica
Borinquena parva La Bucara mine (Manchester coll) align=center
Palaeodiplogaster brentiphila Ron Cauble coll align=center [35] [36]
?Sphyrotheca sp. La Bucara mine (Manchester coll) align=center [37] [38]
Myopsocus arthuri La Toca mine (Poinar coll) align=center
Troctopsocoides gracilis Los Cacaos (INHS coll) align=center [39] [40]
Tityus geratus La Toca mine (Poinar coll)
Habrotrocha sp.
Bdelloidea indet.
Dipoena dominicana La Toca mine (SMF coll) align=center
Clonistria dominicana La Bucara mine (Poinar coll) align=center
Coprinites dominicana La Toca mine (Poinar coll) align=center [41]

See also

References

Bibliography

General geology
Dominican amber

Maps

Notes and References

  1. http://www.fossilworks.org/cgi-bin/bridge.pl?action=displayStrata&geological_group=&formation=La%20Toca&group_formation_member=La%20Toca La Toca Formation
  2. Hoja de Esperanza - 6074-IV, 2010, p.20
  3. Díaz de Neira, 2017, p.663
  4. Hoja de Puerto Plata - 6075-II, 2010, p.105
  5. Hoja de Esperanza - 6074-IV, 2010, p.18
  6. Hoja de Esperanza - 6074-IV, 2010, pp.37-39
  7. Hoja de Esperanza - 6074-IV, 2010, p.99
  8. Hoja de Puerto Plata - 6075-II, 2010, p.100
  9. Díaz de Neira, 2017, p.662
  10. Museo Virtual - Geositio Puerto Plata type section - SGN
  11. Museo Virtual - Geositio Puerto Plata - SGN
  12. Museo Virtual - Geositio Hermanas Mirabal - SGN
  13. Henwood, 1992, p.902
  14. Poinar, 2010, p.27
  15. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=125970 El Valle
  16. Golub & Popov, 2000
  17. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=123393 La Toca mine (AMNH coll)
  18. Davis & Engel, 2006
  19. Heikkilä et al., 2018
  20. Poinar, 2006
  21. Poinar & Brown, 1993
  22. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=155411 El Valle locality (Poinar coll)
  23. Mohrig & Röschmann, 2005
  24. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=124475 La Toca mine (Poinar coll)
  25. Nel et al., 2006
  26. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=124596 La Toca mine (SMF coll)
  27. Johnson et al., 2001
  28. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=134455 La Bucara mine (Poinar coll)
  29. Poinar, 2011
  30. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=140223 La Vega group of mines (AMNH coll)
  31. Grimaldi et al., 1993
  32. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=138708 El Valle locality (MCZ coll)
  33. Wilson, 1985
  34. De Andrade & Urbani, 1999
  35. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=134457 Ron Cauble coll
  36. Poinar, 2009
  37. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=134944 La Bucara mine (Manchester coll)
  38. Penney et al., 2012
  39. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=162585 Los Cacaos (INHS coll)
  40. Mockford & García Aldrete, 2014
  41. Nel et al., 2006

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "La Toca Formation".

Except where otherwise indicated, Everything.Explained.Today is © Copyright 2009-2024, A B Cryer, All Rights Reserved. Cookie policy.