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Marine Incursions: Marine Incursions: Implications for crustal Implications for crustal
thinning and regional strainthinning and regional strain
Kristin McDougallKristin McDougallU.S. Geological SurveyU.S. Geological Survey
Flagstaff, Arizona 86001Flagstaff, Arizona [email protected]@usgs.gov
with assistance from Ana Luisa Carreno, with assistance from Ana Luisa Carreno, Rebecca Dorsey, Arturo Martin, and Michael Rebecca Dorsey, Arturo Martin, and Michael
Oskin Oskin
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QuestionsQuestions
Number of Number of incursionsincursions
AgeAge ExtentExtent EnvironmentEnvironment
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Lower Colorado Lower Colorado RiverRiver
Salton TroughSalton Trough Gulf of Gulf of
CaliforniaCalifornia
LocationsLocations
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Correlation Correlation lower Colorado River, Salton lower Colorado River, Salton Trough, and Gulf of CaliforniaTrough, and Gulf of California
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Middle Miocene microfossilsMiddle Miocene microfossils
Range of reworked planktic foraminifers or calcareous nannofossilsRange of reworked planktic foraminifers or calcareous nannofossils
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Age diagnostic Middle Miocene TaxaAge diagnostic Middle Miocene Taxa
SectionsSections1.1. Hermosillo/Hermosillo/
GuaymasGuaymas
2.2. Cerro PrietoCerro Prieto
3.3. Fish CreekFish Creek
4.4. Whitewater/Whitewater/CabazonCabazon
5.5. Laguna SaladaLaguna Salada
6.6. San FelipeSan Felipe
7.7. Tres Marias IslandsTres Marias Islands
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Middle Miocene microfossilsMiddle Miocene microfossils
Range of reworked planktic foraminifers or calcareous nannofossilsRange of reworked planktic foraminifers or calcareous nannofossils
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Correlation Correlation lower Colorado River, Salton lower Colorado River, Salton Trough, and Gulf of CaliforniaTrough, and Gulf of California
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Gulf of Gulf of CaliforniaCalifornia
Late Miocene ~ 6-8 Late Miocene ~ 6-8 MaMa
Plio-Pleistocene <5.3 Plio-Pleistocene <5.3 MaMa
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Salton Salton TroughTrough
Late Miocene ~ 6-8 MaLate Miocene ~ 6-8 Ma
Plio-Pleistocene < 5.3 MaPlio-Pleistocene < 5.3 Ma
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Age of the Fish Creek Age of the Fish Creek sectionsection
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Whitewater and Whitewater and Cabazon Cabazon SectionsSections
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Paleoecology of the Paleoecology of the Whitewater and Cabazon Whitewater and Cabazon
sectionssections
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Lower Lower ColoradColorado Rivero River
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Distribution of Foraminifers in Distribution of Foraminifers in the Bouse Formationthe Bouse Formation
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Cross section of LCRP wells Cross section of LCRP wells between Cibola and Parkerbetween Cibola and Parker
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BiofaciesBiofacies
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PaleoecologyPaleoecology
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QuestionsQuestions
Number of Number of incursionsincursions
AgeAge ExtentExtent EnvironmentEnvironment
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Middle Miocene incursionMiddle Miocene incursion
11-14 Ma11-14 Ma In situIn situ faunas suggest this faunas suggest this
incursion extends at least as incursion extends at least as far north as the Hermosillo far north as the Hermosillo and Guaymasand Guaymas
Reworked microfossils found Reworked microfossils found further north. further north.
The age of the sediments The age of the sediments middle Miocene faunas are middle Miocene faunas are reworked in to becomes older reworked in to becomes older to the north.to the north.
Northern limit of this incursion Northern limit of this incursion has not been determined. has not been determined.
Deposition occurred during Deposition occurred during warm climatic conditions and warm climatic conditions and high sea level.high sea level.
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Late Miocene incursionLate Miocene incursion 6-7 Ma6-7 Ma Extends as far north Extends as far north
as San Gorgonio Pass, as San Gorgonio Pass, California, and as far California, and as far east as Yuma, Arizona. east as Yuma, Arizona.
Wide variety of Wide variety of environments in a environments in a warm climatic interval warm climatic interval and high sea leveland high sea level
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Plio-Pleistocene incursionPlio-Pleistocene incursion Post 5.3 MaPost 5.3 Ma Extends throughout Extends throughout
most of the Salton most of the Salton Trough and lower Trough and lower Colorado River region Colorado River region as well as the current as well as the current Gulf of California.Gulf of California.
The marine section was The marine section was strongly affected by the strongly affected by the Colorado River, which Colorado River, which rapidly filled the area rapidly filled the area with fresh water and with fresh water and sediment, reducing the sediment, reducing the marine influencemarine influence
Wide variety of Wide variety of depositional depositional environmentsenvironments