Waypoint 75: Middle Eocene, Mexico

List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
Malacostraca - Decapoda
Xanthoidea indet. MacLeay 1838
see common names

Geography
Country:Mexico State/province:Baja California Sur
Coordinates: 26.7° North, 113.0° West (view map)
Paleocoordinates:26.9° North, 99.9° West
Basis of coordinate:stated in text
Time
Period:Paleogene Epoch:Eocene
10 m.y. bin:Cenozoic 2-3
Key time interval:Middle Eocene
Age range of interval:47.80000 - 37.71000 m.y. ago
Stratigraphy
Formation:Bateque
Stratigraphy comments: There are a few interpretations of the stratigraphic relations. McClean and Barron, 1988, mention that “the Bateque formation conformably overlies the Paleocene Ballenas Formation of Sorensen (1982) and is unconformably overlain by several units, including marine and nonmarine sedimentary and volcanic rocks that range in age from Oligocene to Holocene. The oldest overlying unit is the San Gregorio Formation, a late Oligocene and early Miocene sequence composed mainly of siliceous and phosphatic shale, diatomite, and white vitric tuff.” Squires and Demetrion., 1992, say that its base is not exposed and has disconformity with volcanic and sedimentary rocks, with age ranges from Upper Eocene to Holocene. Also, Sandy et al., 1995, mention that mention that in the southern outcrops of the Bateque Formation (between San Juanico and La Purisima) it shows a discordant stratigraphic relation with Isidro Formation (Miocene). In specific localities, the outcrop thickness of the Bateque Formation rarely exceeds 220m (McClean and Barron, 1988).
Lithology and environment
Primary lithology:fine,yellow sandstone
Lithology description: McClean and Barron., 1988, mention that the Bateque Formation is an arkosic marine sandstone and siltstone sequence that contains occasional unaltered, interbedded, white, diatomaceous beds. They also mention that some of arkosic facies are composed of orangish-weathering, fine-grained sandstone with low-angle cross lamination and are interbedded with intensely bioturbated siltstone. Noncalcareous rocks are moderately friable, whereas calcareous lenses are well indurated. Squires and Demetrion 1990, 1990b, and 1994b also mention that the Bateque Formation consists of very fine-grained sandstone.
Environment:coastal indet.
Geology comments: The authors (Schweitzer et al., 2006b) state that the fossils come from the northernmost part of Bateque outcrops in the vicinity of Laguna San Ignacio and Mesa La Salina. It has been correlated with the Capay stage, which is considered middle early Eocene. Squires and Demetrion, 1994, show that the Capay stage (middle early Eocene) had depositional environments consisting of a braid delta and shallow marine environment, possibly coral reef influenced. They also indicate that some macrofossils may have had post-mortem transport and accumulated as channel lag deposits. Some authors mention that the Bateque Formation is indicative of deep sea, outer shelf, and upper slope environments (McClean and Barron, 1988; Morales-Ortega et al., 2016), which may correlate with the offshore component of the stratigraphic column in Squires and Demetrion, 1994, but these fossils seem to be shallower, inner shelf, and possibly nearshore. Therefore, “Coastal Indet.” Is selected as the depositional environment.
Taphonomy
Modes of preservation:body
Size of fossils:macrofossils
Collection methods and comments
Reason for describing collection:taxonomic analysis
Metadata
Database number:228603
Authorizer:J. Wolfe Enterer:A. Lynch
Created:2022-12-16 13:38:45 Last modified:2022-12-16 13:38:45
Access level:the public Released:2022-12-16 13:38:45
Creative Commons license:CC BY
Reference information

Primary reference:
19827.decapod C. E. Schweitzer, R. M. Feldmann, G. Gonzalez-Barba and V. Cosovic. 2006. New Decapoda (Anomura, Brachyura) from the Eocene Bateque and Tepetate Formations, Baja California Sur, Mexico. Bulletin of the Mizunami Fossil Museum 33:21-45 [C. Schweitzer/C. Schweitzer/M. Uhen]