151:
315:, and abundant sandstones and conglomerates. During this time the seashore gradually regressed to the west, as the large mountains eroded and filled the floodplain with alluvium. Over time the depositional environment changed from continental to marine, due to changes in surface elevation and sea level; the marine sedimentary formation equivalent to the Sespe is known as the Alegria Formation, and is more often found to the west, for example in southwestern Santa Barbara County. A peculiarity of the Sespe Formation is the presence of an
41:
354:
218:
Epoch (around 40 million years ago) through the lower
Miocene. It is often distinctive in appearance, with its sandstones weathering to reddish-brown, maroon, pinkish-gray, tan, and green. Since many of its sandstones are more resistant to erosion than many other regional sedimentary units it often
345:
In the
Oligocene the land subsided, creating a shallow, warm marine environment. Sediments continued to accrete, but now they were mixed with the shells of near-shore creatures, similar to those in modern shallow tropical seas. The geologic unit which resulted from deposition in this environment,
587:
Minor, S.A., Kellogg, K.S., Stanley, R.G., Gurrola, L.D., Keller, E.A., and Brandt, T.R., 2009, Geologic Map of the Santa
Barbara Coastal Plain Area, Santa Barbara County, California: U.S. Geological Survey Scientific Investigations Map 3001, scale 1:25,000, 1 sheet, pamphlet, 38
405:
have producing horizons within the Sespe, and as such the unit is of economic importance. Within
Southern California, the combined Sespe-Vaqueros coarse-grained clastic rocks form the second-most important petroleum-bearing unit, second only to the Pliocene-age
307:, ranging in size from microscopic particles to pebbles and even larger rocks, deposited in an extensive coastal floodplain intersected with rivers. The sedimentary rocks which resulted from the millions of years of deposition included
813:. Vol. I (1998), Vol. II (1992), Vol. III (1982). California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR). 1,472 pp. PDF file available on CD from www.consrv.ca.gov. pp. 290, 532
255:
The Lower Unit has a large proportion of conglomerate, as well as sandstone, and a smaller amount of mudstone and shale. Distinguishing this unit are the clasts within the conglomerate, which originated from a source
357:
Typical outcrop of the Sespe
Formation, north of Santa Barbara, California. The red rocks in the center are Sespe; lighter-colored rocks on the mountainside in the background are the Coldwater Formation.
838:
Kendell A. Dickinson & Joel S. Leventhal. "The
Geology, Carbonaceous Materials, and Origin of the Epigenetic Uranium Deposits in the Tertiary Sespe Formation in Ventura County, California"
498:"Recalibration and Causes of Marine Regressive-Transgressive Cycle Recorded by Middle Eocene to Lower Miocene Nonmarine Sespe Formation, Southern California Continental Plate Margin"
365:
fossils have been found in the Sespe, with the principal locations of the finds north of Simi Valley in
Ventura County. A few of the many species associated with the Sespe include
615:
Thomas W. Dibblee, Jr. and Helmut E. Ehrenspeck. "Geology of Santa Rosa Island, California." California
Islands Symposia: 5th California Islands Symposium (1999). Available
775:"A PRACTICAL APPROACH TO PETROPHYSICAL MODEL CONSTRUCTION IN ARKOSIC AND SUB-ARKOSIC SEDIMENTS OF THE SESPE FORMATION USING LOG BASED GEOCHEMICAL SPECTROSCOPY DATA"
894:
616:
338:
period, and the sudden occurrence of redbeds have been used – for example by Thomas
Dibblee – to demarcate the beginning of the Sespe from the end of the
884:
779:
319:
throughout much of the geographic distribution of the unit, representing a gap of millions of years and including most or all of the early
428:
Sandstone from the Sespe also is used as a building material, and colorful boulders of its sandstones are sometimes used for landscaping.
879:
864:
198:
geologic unit in southern and south central
California in the United States. It is of nonmarine origin, consisting predominantly of
278:
The Upper Unit of the Sespe Formation consists of interbedded sandstone, mudstone, and siltstones, without the conglomerates; the
874:
826:, U.S. Geological Survey Digital Data Series DDS-30, Release 2, one CD-ROM, 19 p. + supporting maps, figures, and tables.
45:
Weathered, poorly sorted conglomerate from the lower member of the Sespe Formation, Santa Ynez Mountains, California. The
683:
734:"Oligocene epoch." The Columbia Encyclopedia, Sixth Edition. 2008. Retrieved September 05, 2010 from Encyclopedia.com:
534:"Magnetic Stratigraphy of the Lower Miocene (Early Hemingfordian) Sespe-Vaqueros Formations, Orange County, California"
251:
The Sespe Formation has been divided into three clearly differentiable subunits, designed Lower, Middle, and Upper.
722:
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The Middle Unit also contains conglomerates and sandstones, but the clasts within the conglomerates include
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279:
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633:"Preliminary Geologic Map of the Simi 7.5' Quadrangle, Southern California, A Digital Database"
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385:
In some places, certain high-porosity sandstones within the Sespe unit have been deformed into
203:
108:
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272:
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at this time no longer included the pebbles and boulders which result in conglomerate beds.
240:
8:
447:
339:
80:
661:
Late cretaceous and cenozoic mammals of North America: biostratigraphy and geochronology
442:
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70:
66:
718:
664:
572:
411:
735:
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300:
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687:
486:. Bulletin 186, California Division of Mines and Geology. San Francisco, 1966.
407:
680:
858:
484:
Geology of the central Santa Ynez Mountains, Santa Barbara County, California
418:, a shale deposited in a deep-sea environment, serves as an impermeable cap.
261:
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with granitic and volcanic rocks, probably in the vicinity of the modern-day
192:
156:
24:
839:
327:, the gap corresponded to an erosional event lasting about 8 million years.
316:
632:
324:
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171:
849:
R.D. Reed, "Sespe Formation, California." AAPG Bulletin, Vol. 13, 1929.
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forms dramatic outcrops and ridgelines in many local mountain ranges.
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and has produced 400 million barrels (64,000,000 m) of oil in
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and which follows the Sespe in lithologic sequence, is named the
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found in the Sespe are similar to those characteristic of the
715:
The terrestrial Eocene-Oligocene transition in North America.
268:
122:
46:
697:
695:
681:
Irvine Valley College: the geologic history of Orange County
414:, which are usually much nearer the surface. The overlying
286:
471:
James M. Galloway. "Santa Barbara-Ventura Basin Province."
243:, where it was first named in 1897 and redefined in 1924.
692:
571:. Prentice-Hall, Inc., Upper Saddle River, NJ. 1997.
811:
California Oil and Gas Fields, Volumes I, II and III
736:http://www.encyclopedia.com/doc/1E1-Oligocen.html
856:
389:structures, and contain considerable amounts of
532:Prothero, Donald R.; Donohoo, Linda L. (2001).
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303:eroded over many millions of years, with their
299:mountain ranges in the present-day vicinity of
895:Natural history of Ventura County, California
767:
49:range in size from boulders to small pebbles.
780:American Association of Petroleum Geologists
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625:
83:("Coldwater Sandstone", "Coldwater Shale")
39:
287:Depositional environment and paleontology
622:
352:
239:, about four miles (6 km) north of
857:
495:
425:deposits of potential economic value.
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885:Geology of Ventura County, California
663:. Columbia University Press, 2004.
181:Watts (1897); redefined by Kew (1924)
717:Cambridge University Press, 1996.
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14:
906:
880:Oligocene Series of North America
865:Geologic formations of California
291:During the Oligocene Epoch, the
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91:0–7,500 ft (0–2,286 m)
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638:United States Geological Survey
875:Eocene Series of North America
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214:environment between the upper
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421:The Sespe Formation contains
342:in the stratigraphic column.
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137:Southern and south central
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395:Ventura County, California
701:Minor, et al., map legend
496:Lander, E. Bruce (1994).
397:. For example, both the
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606:Minor et al., map legend
403:West Montalvo Oil Fields
369:(an Eocene rhinoceros),
280:depositional environment
824:Ventura Basin Province
783:. gsa.confex.com. 2010
549:Cite journal requires
513:Cite journal requires
375:Sespedectes singularis
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271:and sandstones of the
231:of the Sespe is along
755:Dibblee (1966), 41-42
659:Woodburne, Michael.
641:. pubs.usgs.gov. 1997
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323:; in the vicinity of
870:Paleogene California
597:Dibblee, 1966, p. 36
567:Deborah R. Harden.
822:Keller, Margaret.
746:Prothero, Emry, 157
713:, Robert J. Emry.
448:Coldwater Formation
381:Economic importance
340:Coldwater Sandstone
81:Coldwater Formation
25:Stratigraphic range
890:Topatopa Mountains
711:Donald R. Prothero
686:2008-11-21 at the
569:California Geology
482:Dibblee, Thomas.
443:Monterey Formation
438:Vaqueros Formation
412:Repetto Formations
359:
348:Vaqueros Formation
273:Franciscan complex
237:Topatopa Mountains
71:Monterey Formation
67:Vaqueros Formation
764:Woodburne, p. 124
210:, shoreline, and
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416:Rincon Formation
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301:San Diego County
191:is a widespread
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229:type locality
223:Type locality
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193:fossiliferous
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157:United States
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785:. Retrieved
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317:unconformity
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188:
186:
163:Type section
109:conglomerate
787:9 September
645:9 September
325:Simi Valley
247:Subdivision
233:Sespe Creek
196:sedimentary
172:Sespe Creek
58:sedimentary
29:Late Eocene
859:Categories
725:p. 155-157
536:: 242–253.
459:References
387:anticlinal
363:vertebrate
313:siltstones
212:floodplain
200:sandstones
139:California
671:. p. 124
391:petroleum
361:Numerous
321:Oligocene
309:mudstones
168:Named for
105:Sandstone
96:Lithology
88:Thickness
63:Underlies
684:Archived
500:: 79–88.
432:See also
305:alluvium
297:volcanic
293:granitic
241:Fillmore
208:riverine
178:Named by
129:Location
119:Mudstone
77:Overlies
423:Uranium
371:Simimys
336:Permian
332:redbeds
258:terrane
235:in the
145:Country
101:Primary
721:
667:
575:
216:Eocene
154:
134:Region
47:clasts
269:chert
123:shale
115:Other
789:2010
719:ISBN
665:ISBN
647:2010
617:here
573:ISBN
555:help
519:help
410:and
408:Pico
401:and
330:The
295:and
227:The
202:and
187:The
55:Type
473:97.
861::
777:.
694:^
635:.
624:^
588:p.
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540:{{
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504:{{
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31:-
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
