Cozy Dell Formation Research Articles

Magnetic stratigraphy and tectonic rotation of the Middle Eocene Matilija Sandstone and Cozy Dell Shale, Ventura County, California: implications for sequence stratigraphic correlations

The Matilija Sandstone and Cozy Dell Shale in the western Transverse Ranges of California record a long history of Eocene regression from deep marine turbidites to non-marine red shales and then transgression to deep marine shales in a rapidly subsiding tectonic basin. In its type area along the Ventura River north of Ojai, the Matilija Sandstone consists of over 800 m of deep marine to non-marine sandstones, and the Cozy Dell Shale contains over 760 m of deep marine shales and turbidite sandstones. Paleomagnetic sampling of these rocks yielded a stable magnetic remanence which passed both a fold test and a reversal test; some samples were reversed at NRM after dip correction. Based on calibration from planktonic microfossils, the Matilija Sandstone spans the interval from Chron C21r to early Chron C20r (46.0–48.5 Ma), and the Cozy Dell from late Chron C20r to C19r (46.0–42.0 Ma). The samples show a tectonic rotation of approximately 85±18° clockwise, consistent with previous results reported for this tectonic block. Previous sequence stratigraphic correlations of these rocks are inconsistent with this chronostratigraphy. None of the sequence boundaries predicted from these sections matches the global sequence chart.

Abstracts: Magnetic Stratigraphy of the Type Matilija Sandstone and Cozy Dell Shale (Middle Eocene), Ventura County, California

Abstracts: Magnetic Stratigraphy of the Type Matilija Sandstone and Cozy Dell Shale (Middle Eocene), Ventura County, California

Abstract: Catastrophic Storm Deposit in a Sandstone Lens of the Eocene Cozy Dell Shale along Sespe Creek, Ventura County, California 

Abstract: Catastrophic Storm Deposit in a Sandstone Lens of the Eocene Cozy Dell Shale along Sespe Creek, Ventura County, California 

The Cozy Dell Formation--Delta Progradation and Turbidite Deposition During Sealevel Highstand: ABSTRACT

The Cozy Dell Formation--Delta Progradation and Turbidite Deposition During Sealevel Highstand: ABSTRACT

Sedimentation Response to Earthquake-Related Events, Middle Eocene Ventura Basin, California: ABSTRACT

Middle Eocene strata in the Topatopa Mountains, northeastern Ventura Basin, California, were deposited as five unconformity-bounded depositional sequences in a seismically-active basin characterized by rapid, episodic subsidence. Analysis of stratigraphic geometries, detailed facies analysis, and backstripping-derived subsidence rates indicate that tectonically-induced differential subsidence caused basin-wide migrations of the Topatopa depocenter at least every 2 m.y. Unusually abundant convolute laminations and a slumped interval may record the influence of earthquakes. The convulate laminations do not grade downward into ripple laminations and are not associated with dewatering dikes and pipes as would be expected if the laminations were formed by shear from an overlying current or by dewatering during rapid burial. Thus, formation during shock-induced liquefaction is more likely. Also a 20-m thick slumped interval in the uppermost Cozy Dell Formation underlies a sequence boundary interpreted as a surface across which depocenter migration took place. Association of this slumped interval with a tectonically-formed surface is consistent with deposition in a seismically-active environment. Rapid, differential subsidence in the Topatopa depocenter was probably episodic and associated with seismic events. Rapid, episodic subsidence with attending earthquakes is recorded in Holocene strata of the Humboldt basin, an analog to the Topatopa depocenter. Also, A Middle Tertiarymore » slumped interval in the southernmost San Joaquin basin is attributed to a seismic event. Similar earthquake-related events are recorded by sedimentation patterns in the Middle Eocene Ventura Basin and may be evident in the strata of other active-margin basins as well.« less

Depositional Environment and Paleogeography of Some Sandstone Lenses in the Upper Cozy Dell Formation. Upper Sespe Creek, Ventura County, California: ABSTRACT

Depositional Environment and Paleogeography of Some Sandstone Lenses in the Upper Cozy Dell Formation. Upper Sespe Creek, Ventura County, California: ABSTRACT

Comparison of Paleogene Paleogeography: Southern Coast Ranges and Western Transverse Ranges

The paleogene stratigraphic sequence exposed in the southwestern San Rafael Mountains at the southern terminus of the Coast Ranges, consists of up to 850 m (2,800 ft) of the marine limestone, sandstone, and mudstone that lies with a unique depositional contact upon Franciscan Complex rocks. Lithofacies identified represent four sedimentary environments: (1) foreslope talus deposits of a neritic algal bank (Sierra Blanca limestone), (2) bathyal basin plain and outer submarine fan deposits (Juncal/Anita Formation and Cozy Dell Shale), (3) suprafan lobe deposits of a bathyal submarine fan (lower Mitilija Sandstone), and (4) sublittoral shelf deposits (upper Matilija Sandstone). Similarities between paleogene rocks in the southwest San Rafael mountains and the western Santa Ynez Mountains of the Transverse Ranges, approximately 60 km (40 mi) to the west, suggest deposition in a similar paleogeographic setting. Paleomagnetic data suggests post-Paleogene clockwise rotations of the western Transverse Ranges of 90{degree}+. Counterclockwise rotation of the western Transverse Ranges by this amount aligns the similar depositional sequences of the western Transverse Ranges with the northwest-trending Paleogene forearc basin of the southern Coast Ranges and eliminates the necessity for an east-west-oriented Paleogene basin at the site of the present western Transverse Ranges.

Sequence Stratigraphy and Facies Architecture of a Middle Eocene Shallow Marine to Basin Transition, Sespe Wilderness Area, California

Several unconformity bounded depositional sequences are present in the Middle Eocene Coldwater, Cozy Dell, and Matilija formations in the Sespe Wilderness Area of California. Five of the sequence-bounding unconformities can be correlated from the canyon walls of Lower Sespe Gorge to the Sespe oil fields 5 km to the east. Three of these unconformities are characterized by a basinward shift of the overlying facies. The Cozy Dell unconformity is a flooded sequence boundary which formed as a surface of bypass and erosion during base-level fall but which was subsequently flooded during subsidence-induced deepening of the basin. The middle Coldwater unconformity is incised 58 m into a depositional sequence recognized on well logs, and alluvial valleys incised into the same unconformity in outcrop contain 58 m of estuarine fill. The unconformity on the paleotopographic highs is a combined flooding surface/sequence boundary with deeper water facies above the unconformity than below. In contrast, the unconformity in the paleotopographic lows is a sequence boundary with shallower water facies above the unconformity than below. The Cozy Dell Formation in outcrop is equivalent to a highstand systems tract, whereas the interval identified by lithology as Cozy Dell in well logs is equivalent to the condensedmore » section at the base of the same systems tract. The systems tract is dominantly shale and contains interbedded lenticular turbidite sandstones on the downthrown, basinward side of an Eocene growth fault. Continuing landward, the turbidites are eventually replaced by shoaling upward parasequences.« less

Fan Sedimentation on Continental Margins: A Comparison of Miocene Gulf Coast Systems with the Middle Eocene Cozy Dell Formation of Southern California: ABSTRACT

Recent seismic and subsurface stratigraphic studies of the Miocene System, offshore Texas resulted in the development of a depositional model that documents and explains the deposition of sand-prone fans on the outer shelf during times when these areas were still covered by several hundred feet of water. This model suggests that sediment transport was by turbid flow and that sedimentation resulted in the development of leveed channel systems. The geometries and scales of these fan systems have been documented by three-dimensional seismic analysis and field-wide well penetrations in the Matagorda 668 field. It further advances the hypothesis that global eustatic levels were generally higher and basin water budgets greater during the Miocene than during later times in at least the Gulf Coast area. Translation of this model to outcrop areas is hampered in the Gulf Coast, and detail verification and refinement of the model has been restricted to subsurface work alone. This has also hampered the authors attempt to carry this model to non-Miocene-age systems. Work on the middle Eocene Cozy Dell Formation exposures in the Topatopa and Santa Ynez Mountains of southern California has revealed that this formation has a depositional history which may not be different than thatmore » interpreted for the Gulf Coast Miocene. This formation was deposited by turbidity currents in what has been interpreted to be an upper slope setting. The fans deposited by these currents have well-developed channel-levee complexes and display scales of geometry similar to those seen in the Gulf Coast Miocene. This formation displays seismic-sequence scale stratal geometries that suggest that it was deposited during lowstands of sea level.« less

Submarine slope mudstone facies, cozy dell formation (Middle Eocene), California

A 120 m thick section of the Cozy Dell Formation (middle Eocene), southem California, consists of a graylaminated mudstone and a tanungraded mudstone; sandstone beds are associated with the laminated mudstone. Sedimentary structures, stratification sequences, foraminiferal distributions, and composition indicate that the ungraded mudstone is an upper slope hemipelagic deposit, while the laminated mudstone is an overbank deposit associated with shallow channels or gullies in which the sandstone beds were deposited. This depositional setting may be analogous to that of the modern Mississippi River delta front.

Sedimentology and Reservoir Potential of Matilija Sandstone: An Eocene Sand-Rich Deep-Sea Fan and Shallow-Marine Complex, California

The Matilija Sandstone of the Santa Ynez Mountains of southern California records a major regressive event in the Eocene Santa Ynez basin in which turbidites were deposited and subsequently covered by shallow-marine deposits. Despite thick, favorable source beds and generally good initial reservoir characteristics, the Matilija Sandstone is not a productive unit in the basin. Low reservoir permeability (generally less than 1 md) and porosity (1 to 10%) are interpreted to be the result of early compaction, cementation, and diagenesis. The lower part of the Matilija Sandstone is a 1,300 ft (400 m) thick sand-rich deep-sea fan complex, which overlies basin plain turbidite deposits of the Juncal Formation. The Matilija Sandstone consists of anastomosing outer fan lobes, lobe fringe, and interlobe deposits overlain by channelized middle and inner fan deposits. The upper Matilija Sandstone consists of shallow-marine cross-bedded sandstone, red beds, and carbonate-evaporite-lignite sequences which overlie the turbidites. Deposition of the Matilija Sandstone was terminated by a rapid basin deepening event which culminated in deposition of basin plain, slope, and turbidite deposits of the Cozy Dell Formation. The lower Matilija Sandstone deep-sea fan deposits have a high sandstone to shale ratio (4:1 to 10:1) and consist of submature arkoses (Folk, 1980). The depositional lobes consist of facies B, C, and D turbidites and a channelized sequence of facies A and B turbidites. The average sandstone is medium grained, moderately sorted, subangular to subrounded, and massive, containing 40% quartz, 35% feldspar (about equal amounts of plagioclase and potassium feldspars), 10% lithic fragments (mostly volcanic and metamorphic types), and minor amounts of detrital clay (illite), mica, chert, and heavy minerals. Early compaction, carbonate cementation, and authigenic pore-lining and pore-filling chlorite, albite, potassium feldspar, quartz, and localized laumontite have reduced the initial porosit and permeability. The only remaining porosity is secondary, resulting from the dissolution of detrital feldspars, and minor fracture porosity.

Hydrocarbon Potential of Matilija Sandstone, an Eocene Sand-Rich, Deep-Sea Fan and Shallow-Marine Complex, California: ABSTRACT

The Matilija Sandstone Member, exposed in the Santa Ynez Mountains, California, records a major regressive event in the Eocene Santa Ynez basin in which turbidites were deposited in the basin and subsequently covered by shallow-marine complexes. Despite thick favorable source beds and generally good initial reservoir characteristics, the Matilija sandstone is not a productive unit in the basin. Lowered reservoir rock permeability (< 1 md) and porosity (0-10%) are due to early compaction, cementation, and diagenesis. The lower part of the Matilija sandstone is a 700-m-thick sand-rich deep-sea fan complex which overlies basin plain and turbidite deposits (Juncal shale). The Matilija sandstone consists of anastomosing outer-fan depositional lobes overlain by channelized middle- and inner-fan deposits. Cross-bedded sandstone, red-bed, and carbonate-evaporite sequences overlie the turbidites. Matilija sandstone deposition closed with rapid transgression which culminated in the deposition of basin plain and turbidite deposits (Cozy Dell shale). The Matilija sandstone lower deep-sea fan complex has a high sandstone and shale ratio (4:1) and consists of submature arkoses of facies B. The average sandstone is medium grained, moderately sorted, subangular, massive, and contains 40% quartz, 35% feldspar (about equal amounts of potassium and plagioclase feldspars), 10% lithic fragments (mostly granitic and volcanic types), and smaller amounts of mica, chert, and heavy minerals. Early compaction, carbonate cementation, and authigenic pore-lining chlorite, albite, and quartz have reduced the initial porosity and permeability. Minor secondary fractures are the only effective porosity in these rocks now. End_of_Article - Last_Page 740------------

Matilija Sandstone; a transition from deep-water turbidite to shallow-marine deposition in the Eocene of California

ABSTRACT The Matilija Sandstone (middle-upper Eocene), exposed in the Santa Ynez Mountains, California, records a major regressive event in the Eocene Santa Ynez Basin in which turbidites were deposited in the basin and subsequently covered by shallow-marine complexes. The Matilija Sandstone is underlain by the Juncal Formation and overlain by the Cozy Dell Shale. The Juncal Formation--a distal turbidite sequence--grades upward into a proximal turbidite sequence in the lower part of the Matilija Sandstone. This proximal turbidite sequence is overlain by a shallow-marine complex which is divisible into coastal and restricted-coastal lithofacies. Recognition and interpretation of these facies is based on fossil occurrences, petrography, biogenic and sedimentary features. Deposition of the Matilija Sandstone documents shoaling from outer neritic and/or bathyal depths in the Juncal Formation and basal part of the Matilija Sandstone to neritic and littoral depths in the upper part of the Matilija. It closed in a rapid transgression which culminated in the deposition of the Cozy Dell Shale (neritic to bathyal depths). The vertical sequence of sedimentary features, facies, and aerial distribution of the Matilija Sandstone suggest that it was deposited as a progradational deltaic complex. Progradation resulted in deposition by traction currents on the shelf, high-concentration sediment gravity flows initiated by slumping and sliding of material on the slope to upper basin, and deposition by lower concentration sediment gravity flows in the basin. As the delta prograded and filled the basin, it covered the deeper-water sediments derived from it.

Age and Correlation of the Eocene Ulatisian and Narizian Stages, California

Paleogene strata crop out along the western boundary of the San Joaquin Basin, in the Santa Barbara Embayment, and in the San Diego Basin, California. Eocene strata are represented by the Ulatisian and Narizian benthic foraminiferal stages (middle and late Eocene, respectively) of Mallory (1959). These provincial stages are used currently for both age assignment and interbasin correlation. Planktonic foraminifers in the Rose Canyon Shale, Poway Conglomerate, and the Matilija, Cozy Dell, Lodo, and Sacate Formations suggest that these formations, as a whole, range in age from late early Eocene to late middle Eocene. Previous authors assigned various elements of the aforementioned formations either to the Ulatisian or Narizian stages. Planktonic foraminiferid species suggest that the Ulatisian stage ranges in age from late early Eocene to early middle Eocene, and the Narizian stage ranges in age from early middle Eocene to late middle Eocene. The time-transgressive nature of ecologically controlled benthic foraminifers is apparent. Furthermore, stages based on benthic foraminifers are not valid means of correlation between tectonically discrete basins of deposition. The occurrence of Subbotina patagonica (Todd) in both the Rose Canyon Shale and Cozy Dell Formation suggests time-equivalence of the two units (early middle Eocene in age).

Foraminiferal and Sedimentological Trends in the Tertiary Section of Tecolote Tunnel, California

A quantitative study was made of the microfossil and sedimentology of most of the Tertiary section in Tecolote Tunnel, Santa Barbara County, California. Foraminiferal evidence indicates that the Cozy Dell shale and Coldwater sandstone are middle Eocene bathyal deposits with an abundance of turbidites. A major middle Tertiary basinal cycle commenced in the Oligocene with the alluvial fan deposits of the Sespe Formation, giving way to middle bathyal deposits with turbidites in the upper Vaqueros Sandstone and Richon Shale formations, and finally to deeper-silled basin deposits in the Mohnian part of the Monterey Shale, also with turbidites. One planktonic foraminiferal zone is recognized for the middle Eocene, and 3 were established for the Miocene. Carbonate/nitrogen ratios were useful in selecting the division between the nonmarine Sespe Formation and the marine paralic facies of the basal Vaqueros Sandstone. The stages of the California Miocene are adjusted to the standard European section by evaluating the Orbulina universa datum.

Stratigraphy and Structure of Mountains Northeast of Santa Barbara, California

The district discussed in this paper includes parts of the Santa Ynez and San Rafael ranges near the coast of Southern California. The oldest rocks belong to the Franciscan group (Jurassic?) and consist chiefly of structurally disorganized dark shale with isolated bodies of sandstone, contorted chert, and other types of rock. The stratigraphic section is remarkable for its great thickness (more than 28,000 feet) of Cretaceous and Eocene sandstone and shale. These sediments, which are marine but only scantily fossiliferous, greatly predominate over the other rocks in areal extent. In this paper the Cretaceous strata are divided into three formations: the Undifferentiated Cretaceous shale, the Debris Dam sandstone, and the Pendola shale, the two latter formations being newly named. Lower Eocene rocks are lacking. There is an important angular unconformity at the base of the middle Eocene section. The well known Sierra Blanca limestone of middle Eocene age locally comprises the basal unit of the Eocene rocks. It is overlain by the thick Juncal formation (middle Eocene shale and sandstone) which is here defined for the first time. Above this are the Matilija sandstone, Cozy Dell shale, and Coldwater sandstone,--all upper Eocene in age, and all previously described by others. The Oligocene is represented by the non-marine Sespe formation, and the Miocene rocks include Temblor sandstone and Monterey shale. At the base of the Miocene section, there is a striking angular unconformity. The Santa Ynez fault, which extends east and west across the area (and beyond), is the most important structural feature. It is a steeply dipping fault of Quaternary age, probably with both a reverse and a strike-slip component of displacement. North of this fault the rocks are folded along northwest-southeast axes in accordance with the general pattern of California Coast Range structure. South of the fault, however, the formations in general strike east-west in harmony with the Transverse Ranges, of which the Santa Ynez Mountains are a member. The rocks of the Santa Ynez Range in this area comprise a locally overturned limb of a large syncline whose trough lies south of the mountains. On the north the limb may have once been shared by an anticline, but the Santa Ynez fault now occupies the supposed axial region. Near the fault the Cretaceous and Eocene beds are interrupted and truncated by a body of Franciscan rocks which, although mainly sedimentary, have apparently been forced upward in the manner of an intrusive mass. The writers describe other structural features and give a chronology of tectonic events. End_Page 1727------------------------------

Geology of Tecolote Tunnel: ABSTRACT

The Tecolote Tunnel, one of the essential features of the Bureau of Reclamation's Cachuma Project, is located in the southeast part of Santa Barbara County, California. The tunnel, now under construction through the Santa Ynez Mountains, connects Cachuma Reservoir in the Santa Ynez Valley with the narrow coastal plain in the Santa Barbara region. Rocks penetrated have a stratigraphic thickness of more than 10,000 feet, range from upper Miocene to middle Eocene age, and include the following formations: Monterey, Rincon, Vaqueros, Sespe, Alegria, Coldwater (Sacate), Cozy Dell, Matilija, Anita (Juncal), and possibly Jalama (Upper Cretaceous age). Three major structural units are found along the tunnel line: (1) the south limb of a major east-west-trending anticline, cut off on the north side by the Santa Ynez fault; (2) a much broken, moderately sheared and deformed, homoclinal sequence which is bounded on the south by the Santa Ynez fault and on the north by a minor fault zone; and (3) a minor northwest plunging syncline. Regularly spaced samples of rock in the tunnel have been and are being taken for the purpose of lithologic, paleontologic, and porosity-permeability studies. Preliminary work on the microfossils from these samples reveals a prolific Miocene fauna but a rather sparse yield from the Eocene. Parts of the tunnel have been logged by using conventional radioactivity (gamma ray) logging equipment with lead shields spaced normal to the ionization chamber. Favorable correlations are found between the log and lithologic units. Uncemented sands, washed and blown into the tunnel by formational water and gas, have caused much delay in progressing through the Santa Ynez fault zone. Large flows of water, more than 4 million gallons per day, from fractured parts of the Cozy Dell formation have also impeded progress. Very minor traces of petroleum have been observed in both of these sections of the tunnel. End_of_Article - Last_Page 2634------------

Eocene Stratigraphy in Western Santa Ynez Mountains, Santa Barbara County, California

This paper describes the critical Eocene section at Canada de Santa Anita, Santa Barbara County, California. The formation of early workers is subdivided into the Anita shale (new name), Matilija sandstone, Cozy Dell shale, Sacate formation (new name), and Gaviota formation in ascending stratigraphic order. Detailed study was confined to the Eocene strata below the type Gaviota formation. The general east-west trending anticlinal structure is complicated by strike faulting. Foraminifers in the Anita shale, which is disconformable on Cretaceous beds, suggest a middle Eocene age for the formation. The molluscan faunule in the Matilija is believed to belong in Clark and Vokes' (1936) Transition stage below the Tejon and above the Domengine. Of particular sign ficance are faunules from the Cozy Dell; these belong in Laiming's (1940) Zones A-1 and A-2. The upper member of the Sacate formation contains a Turritella related to T. variata, the abundant Gaviota species.