Middle Eocene terebratulide brachiopods from the Bateque Formation, Baja California Sur, Mexico

1995 ◽  
Vol 69 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Michael R. Sandy ◽  
Richard L. Squires ◽  
Robert Demetrion
Keyword(s):  
North America ◽  
Baja California ◽  
Pacific Coast ◽  
Middle Eocene ◽  
Central American ◽  
Baja California Sur ◽  
Invertebrate Fauna ◽  
The West ◽  
The Pacific ◽  
Central American Seaway

Two species of terebratulide brachiopods are described from the upper part of the Bateque Formation (middle Eocene) on the Pacific coast of Baja California Sur, Mexico, Terebratulina cf. Terebratulina louisianae Stenzel, 1940, and Terebratalia batequia n. sp. Terebratalia batequia n. sp. is the earliest confirmed record of the genus Terebratalia Beecher, 1893, which has been an important component of Pacific brachiopod faunas through to the present day. The occurrence of Terebratulina cf. Terebratulina louisianae Stenzel is one of the earliest records of the genus from the west coast of North America. These brachiopods, like other elements of the Bateque invertebrate fauna, may record Eocene migration from the Atlantic to Pacific Ocean via the Central American seaway.

A new genus of cassiduloid echinoid from the lower Eocene of the Pacific coast of western North America and a new report of Cassidulus ellipticus Kew, 1920, from the lower Eocene of Baja California Sur, Mexico

1995 ◽  
Vol 69 (3) ◽  
pp. 509-515 ◽  
Author(s):  
Richard L. Squires ◽  
Robert A. Demetrion
Keyword(s):  
North America ◽  
New Genus ◽  
Baja California ◽  
Pacific Coast ◽  
Middle Part ◽  
Baja California Sur ◽  
Western North America ◽  
Lower Eocene ◽  
Shallow Marine ◽  
The Pacific

The cassiduloid echinoid Calilampas californiensis n. gen. and sp. is described from middle lower Eocene (“Capay Stage”) shallow-marine sandstones in both the middle part of the Bateque Formation, Baja California Sur, Mexico, and the lower part of the Llajas Formation, southern California. The new genus is tentatively placed in family Pliolampadidae. The cassiduloid Cassidulus ellipticus Kew, 1920, previously known only from the “Capay Stage” in California, is also present in “Capay Stage” shallow-marine sandstones of the Bateque Formation.

Uranium-Series Ages of Marine Terrace Corals from the Pacific Coast of North America and Implications for Last-Interglacial Sea Level History

1994 ◽  
Vol 42 (1) ◽  
pp. 72-87 ◽  
Author(s):  
Daniel R. Muhs ◽  
George L. Kennedy ◽  
Thomas K. Rockwell
Keyword(s):  
North America ◽  
Sea Level ◽  
Baja California ◽  
Pacific Coast ◽  
Baja California Sur ◽  
Marine Terrace ◽  
San Nicolas Island ◽  
Uranium Series ◽  
Marine Terraces ◽  
The Pacific

AbstractFew of the marine terraces along the Pacific coast of North America have been dated using uranium-series techniques. Ten terrace sequences from southern Oregon to southern Baja California Sur have yielded fossil corals in quantities suitable for U-series dating by alpha spectrometry. U-series-dated terraces representing the ∼80,000 yr sea-level high stand are identified in five areas (Bandon, Oregon; Point Arena, San Nicolas Island, and Point Loma, California; and Punta Banda, Baja California); terraces representing the ∼125,000 yr sea-level high stand are identified in eight areas (Cayucos, San Luis Obispo Bay, San Nicolas Island, San Clemente Island, and Point Loma, California; Punta Bands and Isla Guadalupe, Baja California; and Cabo Pulmo, Baja California Sur). On San Nicolas Island, Point Loma, and Punta Bands, both the ∼80,000 and the ∼125,000 yr terraces are dated. Terraces that may represent the ∼105,000 sea-level high stand are rarely preserved and none has yielded corals for U-series dating. Similarity of coral ages from midlatitude, erosional marine terraces with coral ages from emergent, constructional reefs on tropical coastlines suggests a common forcing mechanism, namely glacioeustatically controlled fluctuations in sea level superimposed on steady tectonic uplift. The low marine terrace dated at ∼125,000 yr on Isla Guadalupe, Baja California, presumed to be tectonically stable, supports evidence from other localities for a +6-m sea level at that time. Data from the Pacific Coast and a compilation of data from other coasts indicate that sea levels at ∼80,000 and ∼105,000 yr may have been closer to present sea level (within a few meters) than previous studies have suggested.

New Eocene marine bivalves from Baja California Sur, Mexico

1990 ◽  
Vol 64 (3) ◽  
pp. 382-391 ◽  
Author(s):  
Richard L. Squires ◽  
Robert Demetrion
Keyword(s):  
North America ◽  
West Coast ◽  
Type Species ◽  
Baja California ◽  
Middle Eocene ◽  
Central Area ◽  
Baja California Sur ◽  
Left Valve ◽  
The West ◽  
Lower Eocene

A new genus, a new subgenus, and five new species of pterioid bivalves are described from shallow-marine faunas in the middle lower to middle Eocene Bateque Formation in the vicinity of Laguna San Ignacio to about 105 km southward, Pacific coast of Baja California Sur, Mexico. Batequeus n. gen. is a medium-sized pectinid with equally convex valves, a short byssal notch, anterior auricles smaller than the posterior ones, the left valve with numerous very closely spaced radial riblets that show the imbricated growth lines very well, the right valve with about 30 low, flat-topped radial ribs that can be grooved, and intercalary ribs on both valves. It is only known from its type species, Batequeus mezquitalensis n. sp., which is from the middle Eocene part of the Bateque Formation. Spondylus batequensis n. sp., a very spinose species, is from the middle lower Eocene part of the Bateque Formation and is only the second reported Spondylus from the lower Eocene of the west coast of North America. Pycnodonte (Phygraea) pacifica n. sp., a species characterized by a radial sulcus that originates in the umbo area, occurs in both the middle lower and middle Eocene parts of the Bateque Formation. Phygraea has not been reported previously from the west coast of North America. Pycnodonte (Pegma) n. subgen. has a plicate left valve with a large attachment area (that can cover the entire valve) and a right valve that usually has an inflated smooth central area surrounded by plicate margins. It is only known from its type species, Pycnodonte (Pegma) bajaensis n. sp., which occurs in both the middle lower and middle Eocene parts of the Bateque Formation. Cubitostrea mezquitalensis n. sp., a strongly ornamented species, is from the middle Eocene part of the Bateque Formation and is the first occurrence of this genus from the west coast of North America.

scholarly journals Middle Eocene Ostracoda from Baja California Sur, Mexico

1993 ◽  
Vol 12 (2) ◽  
pp. 141-153 ◽  
Author(s):  
Ana Luisa Carreño ◽  
Thomas M. Cronin
Keyword(s):  
New Genus ◽  
Baja California ◽  
Pacific Coast ◽  
Gulf Coast ◽  
Middle Eocene ◽  
Water Environment ◽  
Baja California Sur ◽  
The Pacific ◽  
Gulf Coast Region ◽  
Coast Region

Abstract. One genus and six new species of ostracodes are described from the Bateque Formation on the Pacific Coast of Baja California Sur, Mexico. Planktonic foraminifers indicate a mid Eocene age and the whole assemblage is characteristic of a shallow warm-water environment. Paijenborchella mezquitalensis sp. nov. is the second record of the genus Paijenborchella from the Eocene of North America. Except for this species and the new genus Bajacythere, the ostracode association has strong affinities with those described from the lower Tertiary Gulf Coast region.

scholarly journals MIS 5e sea-level history along the Pacific Coast of North America

2021 ◽  
Author(s):  
Daniel R. Muhs
Keyword(s):  
North America ◽  
Sea Level ◽  
Baja California ◽  
Pacific Coast ◽  
Level Indicator ◽  
Sequence Of Events ◽  
Marine Terraces ◽  
The Pacific ◽  
Mis 5E ◽  
Good Agreement

Abstract. The primary last interglacial, marine isotope substage (MIS) 5e records on the Pacific Coast of North America, from Washington (USA) to Baja California Sur (Mexico), are found in the deposits of erosional marine terraces. Warmer coasts along the southern Golfo de California host both erosional marine terraces and constructional coral reef terraces. Because the northern part of the region is tectonically active, MIS 5e terrace elevations vary considerably, from a few meters above sea level to as much as 70 m above sea level. The primary paleo-sea level indicator is the shoreline angle, the junction of the wave-cut platform with the former sea cliff, which forms very close to mean sea level. Most areas on the Pacific Coast of North America have experienced uplift since MIS 5e time, but the rate of uplift varies substantially as a function of tectonic setting. Chronology in most places is based on uranium-series ages of the solitary coral Balanophyllia elegans (erosional terraces) or the colonial corals Porites and Pocillopora (constructional reefs). In areas lacking corals, correlation to MIS 5e can sometimes be accomplished using amino acid ratios of fossil mollusks, compared to similar ratios in mollusks that also host dated corals. U-series analyses of corals that have experienced largely closed-system histories range from ~124 to ~118 ka, in good agreement with ages from MIS 5e reef terraces elsewhere in the world. There is no geomorphic, stratigraphic, or geochronology evidence for more than one high-sea stand during MIS 5e on the Pacific Coast of North America. However, in areas of low uplift rate, the outer parts of MIS 5e terraces apparently were re-occupied by the high-sea stand at ~100 ka (MIS 5c), evident from mixes of coral ages and mixes of molluscan faunas with differing thermal aspects. This sequence of events took place because glacial isostatic adjustment processes acting on North America resulted in regional high-sea stands at ~100 ka and ~80 ka that were higher than is the case in far-field regions, distant from large continental ice sheets. During MIS 5e time, sea surface temperatures (SST) off the Pacific Coast of North America were higher than is the case at present, evident from extralimital southern species of mollusks found in dated deposits. Apparently no wholesale shifts in faunal provinces took place, but in MIS 5e time, some species of bivalves and gastropods lived hundreds of kilometers north of their present northern limits, in good agreement with SST estimates derived from foraminiferal records and alkenone-based reconstructions in deep-sea cores. Because many areas of the Pacific Coast of North America have been active tectonically for much or all of the Quaternary, many earlier interglacial periods are recorded as uplifted, higher elevation terraces. In addition, from southern Oregon to northern Baja California, there are U-series-dated corals from marine terraces that formed ~80 ka, during MIS 5a. In contrast to MIS 5e, these terrace deposits host molluscan faunas that contain extralimital northern species, indicating cooler SST at the end of MIS 5. Here I present a standardized database of MIS 5e sea-level indicators along the Pacific Coast of North America and the corresponding dated samples. The database is available in Muhs (2021)  [https://doi.org/10.5281/zenodo.5557355].

Peniculus asinus (Copepoda: Pennellidae), a new species of copepod parasitic on fishes of the genus Sebastes along the west coast of North America

1977 ◽  
Vol 55 (12) ◽  
pp. 1988-1991 ◽  
Author(s):  
Z. Kabata ◽  
S. N. Wilkes
Keyword(s):  
New Species ◽  
North America ◽  
West Coast ◽  
Pacific Coast ◽  
The West ◽  
Unique Member ◽  
The Pacific ◽  
The Family ◽  
A New Species

Peniculus asinus, a new species of copepod parasitic on Sebastes (Pisces: Teleostei) off the Pacific coast of Canada is described and illustrated. The copepod is an unique member of its genus in that it possesses cephalothoracic holdfast processes. The discovery of a Peniculus with these processes is taken as evidence confirming the place of this genus in the family Pennellidae.

New early Eocene marine gastropods from Baja California Sur, Mexico

1990 ◽  
Vol 64 (1) ◽  
pp. 99-103 ◽  
Author(s):  
Richard L. Squires ◽  
Robert Demetrion
Keyword(s):  
North America ◽  
West Coast ◽  
Baja California ◽  
Western Hemisphere ◽  
Baja California Sur ◽  
The West ◽  
Lower Eocene ◽  
Marine Gastropods ◽  
First Occurrence ◽  
Molluscan Fauna

Three gastropod species are described from a previously unknown shallow-marine molluscan fauna in the lower Eocene Bateque Formation, southwest of San Ignacio, Baja California Sur, Mexico. Velates batequensis n. sp., a commonly occurring neritid in the Bateque, is the only ribbed Velates known from the Western Hemisphere. The fairly rare Platyoptera pacifica n. sp. is the earliest record of this strombid genus and its first occurrence on the west coast of North America. The very rare Cypraedia sp. is also the first occurrence of this cypraeid-like genus on the west coast of North America.

scholarly journals The artisanal elasmobranch fishery of the Pacific coast of Baja California Sur, Mexico, management implications

2013 ◽  
Vol 77 (3) ◽  
pp. 473-487 ◽  
Author(s):  
Felipe Galvan-Magaña ◽  
Sergio R. Ramirez-Amaro ◽  
Daniel Cartamil ◽  
Gerardo Gonzalez-Barba ◽  
Jeffrey B. Graham ◽  
...  
Keyword(s):  
Baja California ◽  
Pacific Coast ◽  
Baja California Sur ◽  
Management Implications ◽  
The Pacific
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