Relationship between relative sea level fluctuations and petrologic variation in forearc basin sedimentary rocks of Upper Cretaceous Rosario Formation at San Carlos, Baja California del Norte, Mexico

Conference · Fri May 01 04:00:00 EDT 1987 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6070754

Morris, W R; Busby-Spera, C

Petrographic study of a well-exposed submarine canyon fill sequence indicates that petrologic variation corresponds to changes in relative sea level. These changes are recorded as textural variation in the canyon fill: a basal coarse-grained unit capped by a middle fine-grained unit records a rise in sea level, and an upper coarse-grained unit records a temporary fall in sea level. These sea level fluctuations do not correlate with published eustatic sea level curves, although the temporary fall may be recorded on a regional (San Diego to San Carlos, 400 km) scale. Sandstone samples from the lower and upper coarse-grained units contain higher concentrations of volcanic rock fragments and plagioclase than the middle fine-grained unit, whereas the middle fine-grained unit contains higher concentrations of quartz and K-feldspar. Fluctuations in relative sea level may have been controlled by tectonic or magmatic events: (1) a tectonically controlled rise in relative sea level could have resulted in longer residence tie of the sediment in a nearshore environment, causing increased mechanical and chemical weathering of the least-resistant grains (i.e., plagioclase and volcanic fragments) relative to quartz and K-feldspar; or (2) a temporary lull in volcanism could have resulted in increased dissection of the arc and decreased sediment input due to lowered base level within the arc, resulting in a marine transgression and an increase in the concentration of quartz and K-feldspar in the sediment. The lack of significant alteration of the feldspar grains in the fine-grained unit relative to the coarse-grained units may favor the second hypothesis.

• Research Organization: Univ. of California, Santa Barbara
• OSTI ID: 6070754
• Report Number(s): CONF-870606-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 71:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
CRETACEOUS PERIOD
DEVELOPING COUNTRIES
FELDSPARS
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
GEOLOGY
LATIN AMERICA
MESOZOIC ERA
MEXICO
MINERALS
NORTH AMERICA
ROCKS
SANDSTONES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
STRATIGRAPHY
TECTONICS