La Quinta Formation, Mexico

For other uses, see La Quinta Formation.

La Quinta Formation
Stratigraphic range: Late Oligocene – Early Miocene 24–20  Ma [1] PreꞒ Ꞓ O S D C P T J K Pg N Pal. Eocene Oligo. Miocene P P
Type	Geological Formation
Unit of	Simojovel Group
Sub-units	See: Members
Underlies	Mazantic Shale
Overlies	Rancho Berlin Sandstone
Thickness	2,900 ft (880 m)
Lithology
Primary	Sandstone
Location
Region	Chiapas
Country	Mexico

La Quinta Formation, sometimes referred to as the Simojovel Formation, is a geological formation in Chiapas, Simojovel in Mexico, deposited during the Late Oligocene into the early Miocene. It is the oldest known formation where Mexican amber can be found.

Geology

The La Quinta Formation is a part of the larger Simojovel Group, and can be found outcropping near Chiapas in Mexico. It is overlain by the Mazantic Shale, whilst it is underlain by the Rancho Berlin Sandstone. ^[2]

Members

The La Quinta Formation is composed of three fossiliferous members, which are as follows, in stratigraphic order (lowest to highest):

• Camino Carretero Member: This member, know to get up to 2,650 ft (810 m) in thickness, is primarily composed of various sandstones. Some of the sandstone layers are noted to be cemented with calcium carbonate, whilst non-calcareous sandstones layers range from brown-ochre to grey weather limoitic fine-grained, alternating massive to thin-bedded fine to coarse-grained brown weathering, coarse-grained arkosic, blue-grey to buff-micaceous fine-grained buff to brown weathering, and buff medium-grained micaceous buff to ochre weathering tuffaceous medium-grained with inter-bedded calcareous rocks. Towards the upper 800 ft (240 m) of the member, the various sandstones give way to tuffaceous sandstones, ranging from buff to limonitic or red tuffaceous sandstone, which is inter-bedded with siltstone, to massive silty medium-grained micaceous tuffaceous limonitic weathering sandstone. Throughout this member, shales are also present, starting as a blue-grey calcareous shale in the lower sections of the member, giving way to sandy shale, buff to micaceous-green shale, buff-micaceous silty ochre weathering shale, fissule limonitic shale, and reddish-brown fissile shale towards the middle sections, although almost become completely absent in the upper sections, save for a layer of dark-grey to black shale. Siltstones are also common within the lower sections of the member, ranging from sandy siltstone, buff to ochre-micaceous siltstone, tan siltstone with inter-bedded marly, tan to dark green-grey weathering siltstone to fine-grained sandstone, blue-grey to brown calcareous siltstone to fine-grained sandstone, tuffaceous massive grey limonitic weathering siltstone to medium-grained sandstone, and minor tuffaceous limonitic weathering sandy siltstones. Limestones can also be found, although it is notably uncommon, only being found as thin layers in the lower and upper sections of member. ^[3]

• Florida Limestone Member: This member, known to get up to 150 ft (46 m) in thickness, is predominately composed of silty limestone, calcareous shale, sandy limestone. In other outcroppings, the member is also composed of algal limestone, lignitic limestone, and massive white limestone. ^[3]

• Finca Carmitto Member: This member, which is roughly 100 ft (30 m) thick, is primarily composed of sandy pebble conglomerate in its lower section, whilst in the upper section it is composed of dark-grey to black rubbly shale and thin light buff-whitish weathering medium-grained calcareous sandstone, which is laminated in nature. ^[3]

Dating

Using U–Pb dating on zircon samples collected from around the upper amber bearing sections, the Mexican amber biota of the La Quinta Formation was constrained to between 24  Ma and 20  Ma . ^[1]

Paleobiota

The biota of the La Quinta Formation is primarily composed of various arthropods, from wasps such as Hyptia deansi , ^[4] to ostracods as Thalassocypria . ^[5] It is also home to a wide variety of plants, such as the fabacid Simojoflorum mijangosii . ^[6]

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Insecta

Genus	Species	Notes	Images
Hyptia [4]	H. deansi	Ensign wasp.
Schwenckfeldina [7]	S. archoica	Fungus gnat.
Mastotermes [8]	M. electromexicus	Termite.
Termitaradus [9]	T. protera	Termite bug.
Aphaenogaster [10]	A. praerelicta	Ant.
Dicromantispa [11]	D. electromexicana	Mantidfly.
Leptopharsa [12]	L. tacanae	Lace bug.
Trichoribates [13]	T. roynortoni	Ceratozetid mite.
Erpetogomphus [14]	E. shii	Gomphid dragonfly.
Argia [14]	Argia sp.	Coenagrionid dragonfly.
Eulaema [15]	E. (Apeulaema) zigrasi	Apid bee.

Ostracoda

Genus	Species	Notes	Images
Thalassocypria [5]	T. cumangulus T. electri T. resinae T. nicokaraszi	Candonid ostracods.
Paracypria [5]	P. inujimensis	Candonid ostracod.
Parapontoparta [5]	Parapontoparta sp. P. lagranjae	Candonid ostracods.
Dolerocypria (?) [5]	D. (?) robinsmithi	Candonid ostracod.
Hemicypris [5]	Hemicypris sp.	Cypridid ostracod.
Edessa [16]	E. protera	Pentatomid insect.

Copepoda

Genus	Species	Notes	Images
Cletocamptus (?) [17]	Cletocamptus (?) sp.	Harpacticoid copepod.
Enhydrosoma [17]	Enhydrosoma sp.	Harpacticoid copepod.
Darcythompsonia [17]	Darcythompsonia sp.	Harpacticoid copepod.
Leptocaris [17]	Leptocaris sp.	Harpacticoid copepod.

Nematoda

Genus	Species	Notes	Images
Oligaphelenchoides [18]	O. atrebora	Aphelenchoidid nematode.
Oligodiplogaster [18]	O. antiqua	Diplogasterid nematode.
Vetus [18]	V. robustus	Rhabditid nematode.

Cnidaria

Genus	Species	Notes	Images
Colpophyllia [19]	C. willoughbiensis	Mussid coral.
Goniopora [19]	G. hilli	Poritid coral.
Porites [19]	P. anguillensis P. portoricensis P. waylandi	Poritid coral.
Siderastrea [19]	S. conferta	Siderastreid coral.
Acropora [19]	A. panamensis	Acroporid coral.
Diploastrea [19]	D. crassolamellata	Diploastraeid coral.
Antiguastrea [19]	A. cellulosa	Merulinid coral.
Goniastrea [19]	G. canalis	Merulinid coral.
Montastraea [19]	M. canalis M. endothecata	Montastraeid coral.

Flora

Genus	Species	Notes	Images
Hymenaea [20]	H. mexicana H. allendis	Legume fabacids.
Simojoflorum [6]	S. mijangosii	Mimosoid fabacid.
Acacia [2]	Acacia sp.	Mimosoid fabacid.
Crudia [2]	Crudia sp.	Detarioid fabacids.
Cedrela [2]	Cedrela sp.	Meliacid angiosperm.
Guarea [2]	Guarea sp.	Meliacid angiosperm.
Pelliciera [2]	Pelliciera sp.	Tetrameristacid angiosperm.
Rhizophora [2]	Rhizophora sp.	Rhizophoracid angiosperm.
Tapiriraizophora [2]	T. durhamii	Anacardiacid angiosperm.
Ilex [2]	Ilex sp.	Aquifoliacid angiosperm.
Staphylea [21]	S. ochoterenae	Staphyleacid angiosperm.
Swietenia [22]	S. miocenica	Meliacid angiosperm.
Picea [2]	Picea sp.	Pinacid spruce tree pollen.
Pinus (?) [2]	Pinus (?) sp.	Pinacid spruce tree pollen.
Podocarpus [2]	Podocarpus sp.	Podocarpacid tree pollen.
Selaginella [2]	Selaginella sp.	Selaginellacid lycophyte pollen.
Sphaeropteris [2]	Sphaeropteris sp.	Cyatheacid tree fern pollen.
Ceratopteris [2]	Ceratopteris sp.	Pteridacid fern pollen.
Pteris [2]	Pteris sp.	Pteridacid fern pollen.
Antrophyum [2]	Antrophyum sp.	Vittarioid fern pollen.
Cryosophila [2]	Cryosophila sp.	Coryphoid palm tree pollen. Misspelled as Crysophila in Graham, 1999.

Undetermined

Genus	Species	Notes	Images
Cletodidae copepod [17]	Cletodidae sp.	Harpacticoid copepod of uncertain affinities, although is assignable to the family Cletodidae.
Laophontidae copepod [17]	Laophontidae sp.	Harpacticoid copepod of uncertain affinities, although is assignable to the family Laophontidae.
Ectinosomatidae (?) copepod [17]	Ectinosomatidae (?) sp.	Harpacticoid copepod of uncertain affinities, tentatively is assignable to the family Ectinosomatidae.
Palmae type 1 [2]	???	Palm tree pollen of unknown affinity.
Aguiaria type [2]	???	Bombacacid pollen of unknown affinity, bears similarities to Aguiaria.
Ericaceae pollen [2]	???	Ericacid pollen of unknown affinity.
Juglandaceae pollen [2]	???	Juglandacid pollen of uncertain affinity, either assignable to Alfaroa or Oreomunnea .
Myrtaceae pollen [2]	???	Myrtacid pollen of uncertain affinity, either assignable to Eugenia or Myrcia .
Unknown 1 - 5 [2]	???	Pollens of unknown affinity.

See also

• List of fossiliferous stratigraphic units in Mexico
• 2017 in arthropod paleontology

References

1. Riquelme, Francisco; Ortega-Flores, Berlaine; Estrada-Ruiz, Emilio; Córdova-Tabares, Víctor (1 June 2025). "Zircon U–Pb ages of the Chiapas Amber-Lagerstätte in the uppermost Simojovel Formation, southwest Mexico". Canadian Journal of Earth Sciences. 62 (6): 1088–1103. doi:10.1139/cjes-2024-0100.
2. Graham, Alan (January 1999). "Studies in Neotropical paleobotany. XIII. An Oligo‐Miocene palynoflora from Simojovel (Chiapas, Mexico)". American Journal of Botany. 86 (1): 17–31. doi:10.2307/2656951.
3. Allison, R. C. (1967). The Cenozoic Stratigraphy of Chiapas, Mexico: With Discussions of the Classification of the Turritellidae and Selected Mexican Representatives. University of California. pp. 1–553. ISBN   9781085391153.
4. Jennings, J.T.; Krogmann, L.; Mew, S. (2012). "Hyptia deansi sp. nov., the first record of Evaniidae (Hymenoptera) from Mexican amber" (PDF). Zootaxa. 3349: 63–68. doi:10.11646/zootaxa.3349.1.7.
5. Matzke-Karasz, Renate; Serrano-Sánchez, María de Lourdes; Pérez, Liseth; Keyser, Dietmar; Pipík, Radovan; Vega, Francisco J. (7 February 2019). "Abundant assemblage of Ostracoda (Crustacea) in Mexican Miocene amber sheds light on the evolution of the brackish-water tribe Thalassocypridini". Historical Biology. 31 (2): 65–101. doi:10.1080/08912963.2017.1340471.
6. Hernández-Damián, Ana L.; Rubalcava Knoth, Marco A.; Gómez-Acevedo, Sandra L.; Cruz-Durán, Ramiro; Cevallos-Ferriz, Sergio R. S. (13 January 2026). "Simojoflorum mijangosii gen. et sp. nov. preserved in the Mexican amber unravels the polycarpellate condition in the tribe Mimoseae (Caesalpinioideae, Fabaceae)". Historical Biology: 1–16. doi: 10.1080/08912963.2025.2604147 .
7. Solórzano Kraemer, M. M.; Mohrig, W. (2007). "Schwenckfeldina archoica sp. nov. (Diptera, Sciaridae) from the middle Miocene Mexican amber" (PDF). Alavesia. 1: 105–108.
8. Krishna, K.; Emerson, A. E. (1983). "A New Fossil Species of Termite from Mexican Amber, Mastotermes electromexicus (Isoptera, Mastotermitidae)" (PDF). American Museum Novitates (2767): 1–8.
9. Poinar, G.; Doyen, J. T. (1992). "A fossil termite bug, Termitaradus protera sp. n. (Hemiptera: Termitaphididae), from Mexican amber". Entomologica Scandinavica. 23: 89–93. doi:10.1163/187631292X00047.
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14. Zheng, Daran; Nel, André; Jarzembowski, Edmund A.; Chang, Su-Chin; Zhang, Haichun; Wang, Bo (2 January 2019). "Exceptionally well-preserved dragonflies (Insecta: Odonata) in Mexican amber". Alcheringa: An Australasian Journal of Palaeontology. 43 (1): 157–164. doi:10.1080/03115518.2018.1456562.
15. Engel, Michael S. (13 May 2014). "An orchid bee of the genus Eulaema in Early Miocene Mexican amber (Hymenoptera: Apidae)". Novitates Paleoentomologicae (7): 1. doi:10.17161/np.v0i7.4726.
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18. Poinar, George O. (1977). "Fossil Nematodes From Mexican Amber". Nematologica. 23 (2): 232–238. doi:10.1163/187529277X00589.
19. Frost, Stanley H.; Langenheim, Ralph L. (1974). Cenozoic reef biofacies: Tertiary larger Foraminifera and scleractinian corals from Chiapas, Mexico. DeKalb, Ill: Northern Illinois University Press. ISBN   0875800270.
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