Cretaceous Great Valley Sequence Research Articles

A Regional View of Urban Sedimentary Basins in Northern California Based on Oil Industry Compressional-Wave Velocity and Density Logs

Compressional-wave (sonic) and density logs from 119 oil test wells provide knowledge of the physical properties and impedance contrasts within urban sedimentary basins in northern California, which is needed to better understand basin amplification. These wire-line logs provide estimates of sonic velocities and densities for primarily Upper Cretaceous to Pliocene clastic rocks between 0.1- and 5.6-km depth to an average depth of 1.8 km. Regional differences in the sonic velocities and densities in these basins largely 1reflect variations in the lithology, depth of burial, porosity, and grain size of the strata, but not necessarily formation age. For example, Miocene basin filling strata west of the Calaveras Fault exhibit higher sonic velocities and densities than older but finer-grained and/or higher-porosity rocks of the Upper Cretaceous Great Valley Sequence. As another example, hard Eocene sandstones west of the San Andreas Fault have much higher impedances than Eocene strata, mainly higher-porosity sandstones and shales, located to the east of this fault, and approach those expected for Franciscan Complex basement rocks. Basement penetrations define large impedence contrasts at the sediment/basement contact along the margins of several basins, where Quaternary, Pliocene, and even Miocene deposits directly overlie Franciscan or Salinian basement rocks at depths as much as 1.7 km. In contrast, in the deepest, geographic centers of the basins, such logs exhibit only a modest impedance contrast at the sediment/basement contact at depths exceeding 2 km. Prominent (up to 1 km/sec) and thick (up to several hundred meters) velocity and density reversals in the logs refute the common assumption that velocities and densities increase monotonically with depth. Online material: Borehole log regression parameters and metadata.

On the frequency distribution of turbidite thickness

The frequency distribution of turbidite thickness records information on flow hydrodynamics, initial sediment volumes and source migration and is an important component of petroleum reservoir models. However, the nature of this thickness distribution is currently uncertain, with log‐normal or negative‐exponential frequency distributions and power‐law cumulative frequency distributions having been proposed by different authors. A detailed analysis of the Miocene Marnoso Arenacea Formation of the Italian Apennines shows that turbidite bed thickness and sand‐interval thickness within each bed have a frequency distribution comprising the sum of a series of log‐normal frequency distributions. These strata were deposited predominantly in a basin‐plain setting, and bed amalgamation is relatively rare. Beds or sand intervals truncated by erosion were excluded from this analysis. Each log‐normal frequency distribution characterizes bed or sand‐interval thickness for a given basal grain‐size or basal Bouma division. Measurements from the Silurian Aberystwyth Grits in Wales, the Cretaceous Great Valley Sequence in California and the Permian Karoo Basin in South Africa show that this conclusion holds for sequences of disparate age and variable location. The median thickness of these log‐normal distributions is positively correlated with basal grain‐size. The power‐law exponent relating the basal grain‐size and median thickness is different for turbidites with a basal A or B division and those with only C, D and E divisions. These two types of turbidite have been termed ‘thin bedded’ and ‘thick bedded’ by previous workers. A change in the power‐law exponent is proposed to be related to: (i) a transition from viscous to inertial settling of sediment grains; and (ii) hindered settling at high sediment concentrations. The bimodal thickness distribution of ‘thin‐bedded’ and ‘thick‐bedded’ turbidites noted by previous workers is explained as the result of a change in the power‐law exponent. This analysis supports the view that A and B divisions were deposited from high‐concentration flow components and that distinct grain‐size modes undergo different depositional processes. Summation of log‐normal frequency distributions for thin‐ and thick‐bedded turbidites produces a cumulative frequency distribution of thickness with a segmented power‐law trend. Thus, the occurrence of both log‐normal and segmented power‐law frequency distributions can be explained in a holistic fashion. Power‐law frequency distributions of turbidite thickness have previously been linked to power‐law distributions of earthquake magnitude or volumes of submarine slope failure. The log‐normal distribution for a given grain‐size class observed in this study suggests an alternative view, that turbidite thickness is determined by the multiplicative addition of several randomly distributed parameters, in addition to the settling velocity of the grain‐sizes present.

An unusual Upper Cretaceous (Santonian) hexactinellid sponge from the Great Valley sequence, western Sacramento Valley, Northern California

The new farreid hexactinellid spongeHormathospongia dictyotanew genus and new species, is described from the upper Santonian Dobbins Shale Member of the Forbes Formation of the Upper Cretaceous Great Valley Sequence from the west side of the Sacramento Valley, northwest of Sacramento. The relatively simple skeleton is composed of quadrangularly arranged hexactines with overlapping rays, an arrangement strikingly similar to the skeletal structure of early Paleozoic reticulosid hexactinellids. However, the California Cretaceous sponges clearly show those spicules embedded in siliceous beams that are united to form a solid dictyonal skeletal framework of only a single layer of regular mesh. Such an occurrence and stratigraphic relationships suggests that the dictyonine sponges had their origin from the simply spiculed reticulosid hexactinellids rather than from the more complex dictyosponges.

A new heteromorph ammonite from the Barremian (Cretaceous) of California

The fauna of the lower Chickabally Member of the Budden Canyon Formation, a part of the Cretaceous Great Valley Sequence in the Cottonwood District (Figures 1, 2) of northern California, was described by Murphy (1975). At that time, two specimens of the species described here were known, but they were not complete enough to be identified or classified. Recently, Embree collected three additional specimens from the same horizon that enable us to classify the taxon with the Heteroceratidae. However, the rate of whorl expansion of the cross section of the conch and the open coiling are different from all other Heteroceratidae and we regard it, like much of the associated fauna, as a genus and species endemic to California.

Primary fabric ellipsoids in sandstones: implications for depositional processes and strain analysis

When measuring strains in deformed clastic rocks, geologists usually assume one or more of the following: (1) objects were initially circular; (2) objects were initially non-circular but had uniform orientations; (3) object populations initially had a fabric, but that this fabric had a symmetrical relationship to bedding; or that (4) initial fabrics are recognizable even after straining. To evaluate these assumptions, we measured 43 fabric ellipsoids in non-strained, poorly sorted sandstones from four depositional settings: DSDP core 174 (fan and abyssal plain deposits off the coast of Oregon); the Cretaceous Great Valley sequence, California (fore-arc deposits): the Cretaceous Pigeon Point Formation, California (accreted and slumped turbidites); and crossbedded sandstones from intracontinental basins in California and Australia. Our results indicate the following: (1) in two-dimensional cuts, individual grains have variable but usually small axial ratios (<3/1) and grains with larger axial ratios are more often, but not always, oriented at small angles to bedding; (2) averaged ratios and orientations of populations of grains in three dimensions define non-spherical fabric ellipsoids, but with small axial ratios (average principal ratios = 1.31:1.14:1); (3) these fabric ellipsoids show a wide range of shapes; and (4) orientations of fabric ellipsoid XY planes have highly variable orientations and are not parallel to bedding or cross-bedding. These results indicate that fabric ellipsoids measured in deformed sandstones must be corrected for the presence of primary fabrics when attempting to calculate strains. However, because of the variable orientations and shapes of the primary fabric ellipsoids and lack of relationship to bedding, strains can, at best, only be bracketed by multiplying final ellipsoids measured in strained samples by reciprocal primary fabric ellipsoids having a variety of orientations and shapes. These data and microstructures in grains and matrix cements also argue against significant compaction during burial in these clast-supported, sand-rich units and instead suggest that the primary fabrics largely reflect grain packing processes during deposition, and/or slumping and packing in the case of the Pigeon Point samples.

Formation and thrusting in some great valley rocks near the Franciscan Complex, California, and implications for the tectonic wedging hypothesis

On the western side of Sacramento Valley in northern California, the Upper Jurassic and Cretaceous Great Valley sequence dips east at 40° to 70° in what has been regarded as a tilted but otherwise undeformed east dipping homocline containing strata collectively up to 15 km in thickness. This paper reports the results of structural mapping in the Paskenta area which suggests that, in contrast, steep dips are caused by westward directed thrusting and folding which led to tectonic thickening of the sedimentary pile. In a mainly east dipping sequence, thrusts are recognized by changes in the structural facing and vergence of both folds and cleavage. Although mainly affecting undated rocks of the Great Valley sequence, one major thrust rides on a serpentine‐matrix melange which forms the substrate of the Great Valley sequence. Differential shortening occurring in different blocks during thrusting was accommodated by left‐lateral movement on the Paskenta and Elder Creek fault zones which acted as tear faults. Ductile and brittle faulting have also occurred throughout the sequence, in the melange, and on the tear faults. From work described in this paper and from other reports of thrusts and deformation in the Great Valley sequence in the foothills west of Sacramento Valley, the hypothesis is advanced that these strata have all been tectonically thickened by westward directed thrusting of possible early Tertiary age. While the regional applicability of this hypothesis awaits future detailed structural work, it is no longer sufficient to assume that east dipping strata have been merely tilted. The proposed thrusting model is compatible with the recent tectonic wedge model proposed for the Coast Ranges‐Sacramento Valley by Wentworth et al. (1984). With respect to such a crustal model in which a tectonic wedge of Franciscan Complex was thrust east above older continental basement but below rocks of the Coast Range ophiolite and Great Valley sequence, thrusts of this paper are back thrusts developed above a gently west dipping floor thrust. Back thrusting, shortening, and structural elevation of the Great Valley sequence are direct consequences of this wedging. The uplifted strata lie east of a poorly defined triangle zone and define the western limb of a regional synclinorium that has some analogies with the Alberta syncline of the Canadian foothills.

Upper crustal structure, Livermore Valley and vicinity, California coast ranges

We have interpreted two reversed seismic refraction profiles in the Livermore Valley area of California using travel times and amplitudes calculated with asymptotic ray theory. The upper crustal structure to 5 km depth is different on either side of the Greenville fault zone. The fault does not appear to extend below 5 km. The fault zone disrupts arrivals of rays which turn in the fault zone, but does not appear to affect rays that turn below 5 km. East of the Greenville fault zone, the boundary between the Cretaceous Great Valley sequence and Franciscan assemblage rocks occurs along a north-dipping interface below 4.5 km depth. West of the Greenville fault, the boundary between valley fill sediments and Franciscan rocks was not observed. Miocene sediment having a high compressional velocity, 5.0 km/sec, is present beneath Livermore Valley to at least 5 km depth. In contrast, the maximum velocity associated with adjacent Cretaceous sediments is 4.2 km/sec. The high velocity of the Livermore basin sediments seen in the refraction data is also observed on sonic logs made in exploratory wells in the basin which bottom in Miocene sediments. This last finding is important, since velocities of 4.8 to 5.0 km/sec have previously been associated with shallow Franciscan rocks. This observation calls into question the use of seismic velocities to distinguish between different Coast Range-Great Valley lithologies without other corroborating data.

Remagnetization of the coast range ophiolite and lower part of the Great Valley Sequence in northern California and southwest Oregon

Overprinted magnetizations have been found at four localities in the Middle Jurassic Coast Range ophiolite and the overlying Upper Jurassic and Lower Cretaceous Great Valley sequence in northern California and at one locality in the partially correlative Lower Cretaceous Days Creek Formation in southwest Oregon. At Del Puerto Canyon, on the east side of the Diablo Range, a pilot study of the upper Jurassic Lotta Creek Formation gives in situ paleomagnetic directions grouped around the present geomagnetic field, suggesting magnetic overprinting long after deposition and folding. We suggest that the loss of original magnetization could be the result of long burial at about 7 km depth, followed by Late Tertiary uplift; the possibility of chemical remagnetization, however, can not be excluded. Paleomagnetic data from sandstones from the Lower Cretaceous Great Valley sequence in the Wilbur Springs area suggest Cenozoic remagnetization that could be related to Pliocene and Pleistocene volcanic and hydrothermal activity in the area. The results from calcareous concretions in the Wilbur Springs area, from 21 sites from basalts and overlying sedimentary rocks of the Great Valley sequence at Stonyford, and from several sites in various rock types in the Coast Range ophiolite and Great Valley sequence near Paskenta suggest unblocking of magnetization during the long period of burial at depth of 7 km or more and remagnetization during tectonic uplift in the Late Cretaceous or Tertiary. Chemical remagnetization, however, can not be excluded. The paleomagnetic data from six sites in Lower Cretaceous sedimentary rocks of the Days Creek Formation in southwest Oregon, which overlies a dismembered ophiolite, fail the fold test. In situ paleomagnetic directions group near the expected Tertiary field directions. These sedimentary rocks may have been remagnetized during a major Eocene tectonic event known to have occurred in this region. The paleomagnetic results confirm that the Coast Range ophiolite and the seemingly little‐deformed Great Valley sequence in northern California, as well as correlative rocks in southwest Oregon have had a complex tectonic history. Once the nature and timing of these events are better understood, the timing of remagnetization may be further constrained, which, in turn, could give further insight into the nature of the tectonic events.

Facies History of the Upper Jurassic-Lower Cretaceous Great Valley Sequence: Response to Structural Development of an Outer-Arc Basin

ABSTRACT The facies history of the Great Valley sequence is closely linked to structural events in an arc-trench system. Upper Jurassic-Lower Cretaceous marine rocks, as much as 8,500 m thick along the western margin of the Sacramento Valley, northern California, were deposited on slopes and submarine fans that extended over an unstable basement floored by ophiolitic rocks. Paleocurrent and paleoslope analyses indicate that eastward subduction, initiated as early as Kimmeridgian, created an outer-arc ridge which bounded the west side of the basin. Debris was shed dominantly from the north and east, but significant contributions were ridge-derived. Sediment fabrics, structures, and bedding styles indicate that earliest deposition on basin plains and on eastward facing slopes was followed, at le st until the Valanginian, by a stable sedimentological framework of prograding and avulsing submarine fans characterized by broad, shallow midfan channels, depositional lobes, and abundant, thick deposits of interchannel mud. The Great Valley rocks are transected by northwest-trending faults that produced strike separation of the east-dipping strata. Smooth facies transitions, but with abrupt thickness variations across faults, suggest that faulting with some normal component of motion was contemporaneous with deposition during latest Jurassic and earliest Cretaceous. Later movement, either strike-slip or reverse, brought coarse, inner-fan facies that were deposited on Klamath basement into fault contact with basin-plain facies that were deposited on ophiolitic basement.

Paleomagnetic study of some Cretaceous and Tertiary sedimentary rocks of the Klamath Mountains province, California

Paleomagnetic investigation of Cretaceous outliers and Tertiary sedimentary strata of the Klamath Mountains province, and of onlapping Cretaceous strata, has shown the rocks to be largely remagnetized. Samples studied are from the Upper Jurassic to Upper Cretaceous Great Valley sequence, Upper Cretaceous Hornbrook Formation, Eocene Montgomery Creek Formation, and Oligocene(?) Weaverville Formation. Cretaceous samples that survived the remagnetization have a mean remanence direction that is very close to the expected direction of the Cretaceous magnetic field at the locality of the Klamath Mountains. Data from both primary and remagnetized samples suggest the possibility of 11.5° ± 15.8° of post-Cretaceous clockwise rotation of the Klamath Mountains province. None of the data from either the primary or remagnetized samples shows evidence of the large amounts (∼ 70°) of clockwise rotation that other workers have measured for the lower Tertiary of the Oregon Coast Range. Our data indicate that the Oregon Coast Range and Klamath Mountains province did not behave as a single rigid block during the early Tertiary. They also suggest that any post-Oligocene rotation of the Klamath Mountains province is less than the approximately 30° post-Oligocene rotation recently proposed for a combined Oregon Coast Range–Klamath Mountains–Cascade Range block.

The Upper Cretaceous (Campanian) ammonite and inoceramid bivalve succession at Sand Creek, Colusa County, California, and its implications for establishment of an Upper Cretaceous Great Valley Sequence ammonite zonation abb: 2

The Upper Cretaceous (Campanian) ammonite and inoceramid bivalve succession at Sand Creek, Colusa County, California, and its implications for establishment of an Upper Cretaceous Great Valley Sequence ammonite zonation abb: 2

Submarine fan facies of the Upper Cretaceous Great Valley sequence, northern and central California

The Upper Cretaceous part of the Great Valley Sequence provides a unique opportunity to study deep-marine sedimentation within an arc-trench gap. Facies analysis delineates submarine fan facies similar to those described from other ancient basins. Fan models and facies of Mutti and Ricci-Lucchi allow reconstruction of the following depositional environments: basin plain, outer fan, midfan, inner fan, and slope. Basin plain deposits are characterized by hemipelagic mudstone with randomly interbedded thin sandstone beds exhibiting distal turbidite characteristics. Outer fan deposits are characterized by regularly interbedded sandstone and mudstone, and commonly exhibit thickening-upward (negative) cycles that constitute depositional lobes. The sandstone occurs as proximal to distal turbidites without channeling. Midfan deposits are characterized by the predominance of coarse-grained, thick, channelized sandstone beds that commonly are amalgamated. Thinning-upward (positive) cycles and braided channelization also are common. Inner fan deposits are characterized by major channel-fill complexes (conglomerate, pebbly sandstone, and pebbly mudstone) enclosed in mudstone and siltstone. Positive cycles occur within these channel-fill complexes. Much of the fine-grained material consists of levee (overbank) deposits that are characterized by rhythmically interbedded thin mudstone and irregular sandstone beds with climbing and starved ripples. Slope deposits are characterized by mudstone with little interbedded sandstone; slumping and contortion of bedding is common. Progressions of fan facies associations can be described as retrogradational and progradational suites that correspond, respectively, to onlapping and offlapping relations in the basin. The paleoenvironments, fan facies associations, and tectonic setting of the Late Cretaceous fore-arc basin are similar to those of modern arc—trench systems.

Sedimentology of Fluvial to Bathyal Sandstones of Cretaceous Great Valley Sequence, California: ABSTRACT

Sedimentology of Fluvial to Bathyal Sandstones of Cretaceous Great Valley Sequence, California: ABSTRACT