Microfossils from Cerro Prieto geothermal wells, Baja California, Mexico
To aid in a paleonenvironmental and age reconstruction of the Cerro Prieto reservoir system, 59 samples of well cuttings were analyzed for microfossils. The cuttings were obtained at depths from 351 to 3495m in 14 geothermal wells in the Cerro Prieto field, Baja California, Mexico. Foraminifera was found in 6 samples, ostracodes in 19 samples and mannoplankton as coccoliths in 24 samples. Other groups, such as molluscus, insects, fish skeletal parts, and plant material were occasionally present. Detailed interpretations at this time cannot be made because of poor preservation of samples. This is primarily due to causes: dissolution by geothermal fluids that reach 350/sup 0/C, and the extensive mixing of filled Cretaceous forms (reworked from the Colorado Plateau region) with Tertiary species during drilling. Further studies of ostracodes and foraminifera from colder portions of the wells are needed. The abundant and well-preserved ostracodes indicate marine to backish water inviroments that correspond in part, to lagoonal or estuarine facies. The presence of the mid-Tertiary (15-m.y.-old) marine foraminifera, Cassigerinela chipolensis, in wells M-11 and M-38, 350 to 500m deep, is perplexing. These are not laboratory contaminates and, as yet have not been found in the drilling mud. If further studies confirm their presence at Cerro Prieto, established ideas about the opening of the Gulf of California and about Pacific Coast mid-Tertiary history will need to be rewritten.
- Research Organization:
- Univ. of Southern California, Los Angeles
- OSTI ID:
- 7369517
- Report Number(s):
- CONF-8208109-Vol.2-17; ON: DE87003674
- Resource Relation:
- Conference: 4. symposium on the Cerro Prieto geothermal field, Guadalajara, Mexico, 10 Aug 1982; Related Information: In: ACTAS proceedings: Volume 2, by
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CERRO PRIETO GEOTHERMAL FIELD
GEOLOGY
PALEONTOLOGY
FOSSILS
GEOTHERMAL WELLS
GEOTHERMAL FIELDS
WELLS
Geothermal Legacy
150202* - Geology & Hydrology of Geothermal Systems- Non-USA- (-1989)
150302 - Geothermal Exploration & Exploration Technology- Geochemical Techniques & Surveys