origin and diagenesis of clay minerals in the monterey formation ...

Clays and Clay Minerals, Vol. 39, No. 5, 449-466, 1991.

ORIGIN AND DIAGENESIS OF CLAY MINERALS IN THE MONTEREY FORMATION, SANTA MARIA BASIN AREA, CALIFORNIA JOHN S. COMPTON Department of Marine Science, University of South Florida, St. Petersburg, Florida 33701 Abstract--The clay mineralogy of the Miocene Monterey Formation was determined for onshore and offshore sequences in the Santa Mafia basin area, California. The 0.5 m m rock chips were ultrasonicated to remove drilling m u d from their surfaces. The chips were then crushed in an agate mortar and pestle in deionized water, ultrasonically suspended in 3% sodium hexametaphosphate solution, and sep-

arated into > 38-~m, 2-38-gm, and 0.1-2-#m-fractions by sieving and centrifuging. The < 0.1-~tm fraction was collected using a porous ceramic filter candle. The different size fractions were m o u n t e d on glass slides and analyzed using a Scintag XDS 2000 X-ray diffractometer and C u K a radiation. Oriented, air-dried clay m o u n t s were saturated with ethylene glycol and analyzed on the X R D to determine the percent expandable layers using the techniques described by Reynolds and Hower (1970), Reynolds (1980), and Srodofi (1980). Reichweite (R) nomenclature (Jadgozinski, 1949) was used to indicate the ordering type with R = 0 for randomly interstratified I/S and R = 1 for ordered US (altemating ISIS . . . ) . X R D clay mounts on ceramic tiles were heated to 550~ for 1 hour and analyzed to identify chlorite. Clinoptilolite was differentiated from heulandite by heating the samples to 600*(2.

Modal analysis Homogeneous, powdered splits of bulk samples were sent to X-ray Assay Laboratories (XRAL, Ontario) for

452

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Vol. 39, No. 5, 1991

Clay mineral diagenesis in the Monterey Formation

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major and trace element analysis using X-ray fluorescence spectroscopy (XRF) (Table 1). Total carbon and carbonate carbon were measured coulometrically on a separate split, and total sulfur was determined by X R F on a separate split. The approximate mineral composition o f the samples (Table 2) was determined by combining the relative mineral abundances from the X R D data (integrated peak areas) and the major oxide elemental analyses (Table 1). A set o f linear equations, representing the chemical composition o f each o f the minerals identified by X R D analysis, was solved simultaneously to yield a mineral composition consistent with the X R D results. The following procedure was used to assign the elemental analyses to the minerals identified by X R D : 1. Carbon--Total carbon was subtracted from carbonate carbon to give organic carbon, and kerogen was calculated as 1.4 x organic carbon (Tissot and Welt, 1984). Carbonate carbon was attributed to dolomite and calcite. The small a m o u n t o f carbonate present in francolite (3-6 mole %) was neglected. 2. Calcium-Ca was assigned first to dolomite and calcite, and then to francolite to account for the analyzed P205. The remaining Ca was assigned to plagioclase feldspar (anorthite) and to I/S as an exchangeable interlayer cation. 3. Magnesium--Mg was assigned first to dolomite, and then to I/S and mica minerals. The relative abundance o f the mica minerals was estimated by the intensity o f the 10.0 A and 4.48 A peaks. The relative amounts o f the different mica minerals that were observed in petrographic thin sections (discrete illite, biotite, muscovite) were not determined. A n average chemical composition for the mica minerals was used that assumed an equal proportion ofillite, biotite, and muscovite. 4. Potassium--K was assigned to mica minerals, K-feldspar, and I/S. 5. Sodium--Na was assigned to plagioclase feldspar (albite) and to I/S as an exchangeable cation. 6. Aluminum--excess AI was assigned to kaolinite. 7. Silica--Detrital quartz was estimated as 1.4 x A1203 (Isaacs et aL, 1983). Excess Si was assigned to opal-A, opal-CT, or quartz, F o r opal-A or opal-CT rocks, excess Si was assigned to the predominent silica phase because small amounts o f opal-A were difficult to detect. This simplification gives the false impression that opal-A and opal-CT are mutually exclusive in Table 2. 8. Iron--Fe was first assigned to pyrite to account for analyzed S. Fe was then assigned to I/S, mica minerals, and ferroan dolomite. A n y remaining Fe is reported as excess Fe203 in Table 2. This excess Fe m a y be present as X-ray amorphous Fe-oxides or m a y be the result o f underestimating the Fe content o f the mica minerals or dolomite. 9. Sulfur--excess S (total S-pyrite S) was assigned to kerogen because kerogen from the Monterey F o r m a t i o n was reported to contain up to 10 wt. % S (Orr, 1984). Samples from the B-2 well were not analyzed for S, but the S content o f the bulk rocks was estimated from the linear relationship be-

454

Clays a n d Clay Minerals

Compton Table 2. Calculated mineralogy o f bulk rock samples. Sample

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13 35 41 19 37 0 0 0 0 0 0 3 0

0 0 0 0 0 45 29 0 85 29 70 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0

16 12 10 11 8 9 10 0 2 4 4 1 2

20 51 60 60 130 140 140 260 270 280 307

0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0

5 23 0 0 29 0 0 7 21 9 4

B-2 Well, Platform Hermosa 5010( 5 5 % illite layers agrees with the change in morphology documented by Keller et aL (1986) and by Pollastro (1985) (compare Figures 4B, 10B and 8A, 8B). Keller et al. suggested that the compact and planar I/S with scalloped flake edges that terminate in sharp points reflects polytypic changes in the crystal structure o f the I/S when the percent illite layers exceeds 55%. The mineral association observed in the Monterey

Vol. 39, No. 5, 1991

Clay mineral diagenesis in the Monterey Formation

Formation, I/S, kaolinite, chlorite, quartz, and dolomite, suggests that the availability o f K is limited during the illitization o f smectite (reaction 4). A limited source o f K is supported by the low abundance o f K-feldspar in the Monterey Formation. The low abundance o f K-feldspar does not appear to be the result o f its dissolution during the illitization reaction. The K-feldspar content o f the Monterey F o r m a t i o n at Pt. Pedernales, where no illitization has occurred, is not noticeably different from the K-feldspar content o f equivalent-aged rocks from the Lions H e a d area or the offshore B-2 well that have undergone extensive illirization. The ratio o f KzO to A1203 from the elemental analyses o f bulk samples varies by less than 30% and shows no systematic change with burial depth (Table 1; Isaacs et aL, 1983). This is consistent with previous studies o f clay mineral diagenesis where no systematic bulk chemical trends were observed as a function of burial depth (e.g., Dunoyer de Segonzac, 1970; Hower et aL, 1976; and others). Mica minerals are c o m m o n in the Monterey F o r m a t i o n and are another possible source o f K, but dissolution o f mica grains was not observed and the abundance o f mica minerals does not appear to decrease with depth in the illitization zone. A n additional indication that K is limited during illitization is the unusually high a m m o n i u m content o f the I/S (Tables 3, 4). A m m o n i u m released from the thermal degradation o f organic matter in organic-rich rocks can substitute for K in the illite structure (Williams et al., 1989). F i x e d - a m m o n i u m contents were found to be significantly higher in rocks from the offshore B-2 well (located in the Pt. Arguello oil field) than in rocks from the Lions H e a d area. The mineralization o f a m m o n i u m in rocks from the B-2 well is p r o m o t e d by the coincidence o f the illitization ofsmecrite and the release o f a m m o n i u m during the generation o f hydrocarbons (Compton et al., 1991). It is unlikely that the kaolinite in the Monterey Formarion in the B-2 well and the Lions Head area is detrital in origin because o f the lack o f a suitable source area, the absence o f kaolinite from equivalent-aged rocks at Pt. Pedernales, and the abundance and texture o f kaolinite in metabentonite beds from the Lions H e a d area (Figure 10A). Authigenic kaolinite occurs in a large number o f samples from the disturbed belt o f Montana, including bentonite and metabentonite beds, and was proposed to form from the alteration o f volcanic glass, smectite, and plagioclase feldspar (Hoffman and Hower, 1979). Kaolinite can form directly from the alteration o f volcanic glass. F o r example, tonsteins are volcanic ash beds in coal deposits that have altered completely to kaolinite (Bohor et al., 1978). However, no kaolinite was observed in the bentonite beds studied from the Pt. Pedernales area. The extent to which K limits the illitization ofsmectite appears to have varied because individual metabentonite beds from the Lions H e a d area contain significantly more kaolinite than

463

adjacent siliceous mudstone and dolostone beds, and rock chips from the B-2 well (Table 2). Pollastro (1981) observed kaolinite associated with pyrite in the foraminiferal tests o f the Cretaceous Niobrara Formation. He suggested that organic matter degradation within the foraminiferal tests provides a microenvironment favorable to kaolinite and pyrite precipitation. Kablanow and Surdam (1983) observed a nearly 1:1 correlation between kaolinite and migrated hydrocarbons in the Huasna Basin. They proposed that organic matter decomposition leads to the formation o f acidic pore fluids that dissolve clay and feldspar minerals, and that authigenic kaolinite precipitates from these aluminosilicate-rich fluids. The alteration ofsmectite to kaolinite in reaction (4) requires the release o f octahedral Mg and Fe, which can go into the formation o f chlorite, ferroan dolomite, or ankerite if calcite is present: 2 CaCO3 q- 0.5 Mg 2§ + 0.5 Fe 2§ = CaMgo.sFe0.5 (CO3)2 + Ca 2§

(5)

F o r example, late diagenetic ankerite was proposed to form from Mg and Fe released during the illitizarion o f smectite in the Wilcox G r o u p o f Texas (Boles and Franks, 1979), and late ferroan dolomite was observed associated with argillaceous marine carbonates (McHargue and Price, 1982). In the Santa M a r i a basin area, most o f the original biogenic calcite (foraminifers and nannofossils) has been replaced by calcian or ferroan dolomite (Compton, 1988). Most o f this dolomite appears to form during early diagenesis, but some m a y form or recrystallize at the deeper burial depths o f the illitization reaction. The small amounts o f chlorite c o m p a r e d to I/S and kaolinite in the Monterey Formation m a y result from the formation o f late dolomite rather than chlorite and the fact that chlorite contains a greater proportion o f Mg and Fe to AI than smectite. F o r example, reaction (4) will yield roughly six times more kaolinite than chlorite unless additional sources o f Mg and Fe are available. Fe- and Mg-rich smecrites appear to alter to illite more slowly than aluminous smectites and result in a greater release o f Fe and Mg at deeper burial depths (Boles and Franks, 1979). This would predict kaolinite to be more abundant than chlorite in the early stages o f illitization, and chlorite to increase in abundance in the later stages o f illitization. Authigenic Fe-rich chlorite appears to form after kaolinite in the G u l f Coast region, with chlorite replacing kaolinite in places (Burton et aL, 1987). A n increase in the release o f Fe and Mg from the alteration o f smectite to illite m a y lead to the formation o f the chlorite in the Monterey Formation, possibly by replacement o f earlier-formed kaolinite. Corrensite from the base o f the Lions H e a d sequence is most likely locally derived from weathering o f the Mg-rich mafic rocks associated with the underlying ophiolite complex.

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Compton

Origin o f the zeolite minerals

There are few reports o f zeolite minerals in the Monterey Formation. Hein et al. (1979) tentatively identified laumontite in the Pt. Conception COST well. Diagenesis o f zeolite minerals in the Obispo Tuff, which is overlain by the Monterey F o r m a t i o n in the Pismo Basin, was studied by Surdam and Hall (1984). They found that clinoptilolite and mordenite are the pred o m i n a n t zeolite minerals, in addition to some analt i m e . In the present study, zeolite minerals were found to be ubiquitous in the Monterey Formation, but in m i n o r to trace amounts. The controls on the diagenesis o f zeolite minerals are complex and include initial composition and grain size o f the glass, temperature, and pore water chemistry (e.g., Hay, 1963; Iijima, 1978). The stability fields for the different zeolite minerals are known only approximately and are based largely on field observations. Clinoptilolite is most abundant in opal-CT rocks from the Pt. Pedernales area. In diatomaceous sediments from the Bering Sea, abundant clinoptilolite was found to coincide with the opal-A to opal-CT transformation and it was suggested that diagenesis o f biogenic silica is an important factor (Hein et al., 1978). F o r m a t i o n o f a n a l c i m e is favored by a high ana/aH ratio and a low asi: clinoptilolite + N a + = analcime + quartz + K +

(6)

These conditions are most likely to occur in quartz rocks from the Monterey F o r m a t i o n where the silica activity is low relative to opal-A or opal-CT rocks, and the activity o f N a is high relative to the activity o f K because o f K removal during the illitization reaction. This m a y explain why clinoptilolite was not observed in quartz rocks. Precipitation o f clinoptilolite is a sink for K and its alteration to analcime a source o f K for the illitization reaction. The transformation o f analcime to albite was not observed in the Monterey Formation and the transformation o f analcime to K-feldspar seems unlikely because o f the high a r J a ~ ratio anticipated as a result o f the illitization reaction. Zeolite minerals can also transform to clay minerals as observed in late, fault-controlled diagenesis o f the Obispo Tuff(Surdam and Hall, 1984). SUMMARY 1. A significant a m o u n t o f the I/S in the Monterey F o r m a t i o n from the distal Santa Maria Basin appears to be derived from the alteration o f volcanic material disseminated in the rocks and concentrated in ash beds. The alteration o f volcanic glass to smectite appears to be rapid and to coincide approximately with the opal-A to opal-CT transformation. The alteration o f volcanic glass to smectite m a y inhibit the opal-A to opal-CT transformation by the removal o f pore-water Mg, promote dolomitization by raising the pH, and alter the Sr isotopic composition o f the pore water.

Clays and Clay Minerals

2. Initial illitization o f smectite coincides with the opal-CT to quartz transformation. The percent illite layers in the US increases from 10% to 80% over a stratigraphic depth o f 0.8 k m that corresponds to a present-day temperature range o f 80-115~ The d o m inance o f plagioclase over K-feldspar, the presence o f diagenetic kaolinite, and the anomalously high fixeda m m o n i u m content o f the I/S suggest that K availability limits the a m o u n t o f illitization and results in the transformation o f smectite to kaolinite, chlorite, and possibly late ferroan dolomite. 3. Zeolite minerals are c o m m o n in m i n o r to trace amounts in m a n y o f the Monterey rocks studied. Clinoptilolite was observed primarily in opal-CT rocks and was not observed in quartz rocks. Analcime and mordenite were tentatively identified primarily in quartz rocks. F o r m a t i o n o f zeolite minerals m a y be limited, in part, because the p H is buffered by the precipitation o f dolomite. ACKNOWLEDGMENTS Financial support for this study is gratefully acknowledged from the Donors o f the Petroleum Research Fund, administered by the American Chemical Society, and a Creative Scholarship G r a n t from the University o f South Florida. Samples from the offshore Santa Maria Basin were provided by Chevron U S A with the assistance o f T o m MacKinnon. I thank Osmonics, Inc. for providing ceramic filter candles. Toedsit Netratanawong assisted with sample processing and analysis, and Tony Greco assisted with the SEM. This paper benefited from the comments and suggestions o f Alden Carpenter, D a v i d Pevear, and Richard Pollastro. REFERENCES Bemer, R. A. (1982) Burial of organic carbon and pyrite sulfur in the modem ocean: Its geochemical and environmental significance: Amer. J. Sci. 282, 451-473. Bohor, B. F., Pollastro, R. M., and Phillips, R. E. (1978) Mineralogical evidence for the volcanic origin of kaolinitic partings (tonstein) in Upper Cretaceous and Tertiary coals of the Rocky Mountain Region: 15th Ann. Mtg., Clay Minerals Society, Bloomington, Indiana, p. 47 (abst.). Boles, J. R. and Franks, S. G. (1979) Clay diagenesis in Wilcox sandstones of southwest Texas: Implications of smectite diagenesis on sandstone cementation: J. Sed. Petrol. 49, 55-70. Bramlette, M.N. (1946) The Monterey Formation of California and the origin of its siliceous rocks: U.S. Geol. Surv. Prof Paper 212, 57 pp. Bremner, J.M. (1965) Inorganic forms of nitrogen: in Methods ofSoilAnalyses, C. A. Black, ed., Part 2, Agronomy 9, Am. Soc. Agronomy, Inc., 1179-1237. Burst, J. F., Jr. (1969) Diagenesis of Gulf Coast clayey sediments and its possible relation to petroleum migration: Amer. Assoc. Petrol. Geol. Bull. 53, 73-93. Burton, J. H., Krinsley, D. H., and Pye, K. (1987) Authigenesis of kaolinite and chlorite in Texas Gulf coast sediments: Clays & Clay Minerals 35, 291-296. Compton, J. S. (1986) Early diagenesis and dolomitization

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Clay mineral diagenesis in the Monterey Formation

of the Monterey Formation, California: Ph.D. thesis, Harvard University, Cambridge, Massachusetts, 174 pp. Compton, J. S. (1988) Sediment composition and precipitation of dolomite and pyrite in the Neogene Monterey and Sisquoc formations, Santa Maria basin area, California: in Sedimentology and Geochemistry of Dolostones, V. Shukla and P. A. Baker, eds., SEPM Spec. Publ. 43, 53-64. Compton, J. S. (1991) Porosity reduction and burial history of siliceous rocks from the Monterey and Sisquoc formations, Pt. Pedernales area, California: Geol. Soc. Amer. Bull. 103, 625-636. Compton, J. S. and Siever, R. (1986) Diffusion and mass balance of Mg during early dolomite formation, Monterey Formation: Geochim. Cosmochim. Acta 50, 125-135. Compton, J. S., Williams, L. B., and Ferrell, R. E., Jr. (1991) Mineralization of organogenic ammonium in the Monterey Formation, California: Geochim. Cosmochim. Acta (in press). Cook, H.E. (1979) Geologic Studies of the Point Conception Deep Stratigraphic Test Well OCS-CAL 78-164 No. 1, Outer Continental Shelf Southern California, United States." U.S. Geol. Surv. Open-File Report 79-1218. Crain, W. E., Mero, W. E., and Patterson, D. (1985) Geology of the Point Arguello discovery: Amer. Assoc. Petrol. Geol. Bull. 69, 537-545. Dunoyer de Segonzac, G. (1970) The transformation of clay minerals during diagenesis and low-grade metamorphism: A review: Sedimentology 15, 281-346. Dunham, J. B. and Blake, G.H. (1987) Guide to the Coastal Outcrops of the Monterey Formation of Western Santa Barbara County, California: Pacific Section SEPM 53, 36 pp. Eberl, D. and Hower, J. (1976) Kinetics ofillite formation: Geol. Soc. Amer. Bull. 87, 1326-1330. Elderfield, H. and Gieskes, J. M. (1982) Sr isotopes in interstitial waters of marine sediments from Deep-Sea Drilling Project cores: Nature 300, 493-497. Friedman, I. and Murata, K . J . (1979) Origin of dolomite in Miocene Monterey shale and related formations in the Tremblor Range, California: Geochim. Cosmochim. Acta 42, 1357-1365. Garrels, R. M. (1984) Montmorillonite/illite stability diagrams: Clays & Clay Minerals 32, 161-166. Gorsline, D. S. and Emery, K. O. (1959) Turbidity-current deposits in San Pedro and Santa Monica Basins of southern California: Geol. Soc. Amer. Bull. 70, 279-290. Grivetti, M. C. (1982) Aspects of stratigraphy, diagenesis, and deformation in the Monterey Formation near Santa Maria-Lompoc, California: M.S. thesis, University of Califoruia, Santa Barbara, California, 155 pp. Hall, C. A., Jr. (1981) San Luis Obispo transform fault and Middle Miocene rotation of the western transverse ranges, California: J. Geophys. Res. 86(B2), 1015-1031. Haq, B. Q., Hardenbol, J., and Vail, P.R. (1987) Chronology of fluctuating sea levels since the Triassic: Science 235, 1156-1167. Hay, R.L. (1963) Stratigraphy and zeolitic diagenesis of the John Day Formation of Oregon: Univ. of Calif. PubL in GeoL Sei. 42, 199-262. Hein, J. R., Scholl, D. W., Barron, J. A., Jones, M. G., and Miller, J. (1978) Diagenesis of late Cenozoic diatomaceous deposits and formation of the bottom simulating reflector in the southern Bering Sea: Sedimentology 25, 155181. Hein, J. R., Vanek, E., and Allen, M . A . (1979) X-ray mineralogy and diagenesis: in Geologic Studies of the Point Conception Deep Stratigraphic Test Well OCS-CAL 78-164 No. 1, Outer Continental Shelf, Southern California. United States, H. E. Cook, ed., U.S. Geol. Surv. Open-File Report 79-1218, 79-96. Hoffman, L and Hower, J. (1979) Clay mineral assemblages

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as low grade metamorphic geothermometers: Application to the thrust faulted disturbed belt of Montana, U.S.A.: in Aspects ofDiagenesis, P. A. Scholle and P. R. Schluger, eds., SEPM Spec. Pub1. 26, 55-79. Hower, J., Eslinger, E. V., Hower, M., and Perry, E.A. (1976) The mechanism of burial metamorphism of argillaceous sediments: 1. Mineralogical and chemical evidence. Geol. Soc. Amer. Bull. 87, 725-737. Iijima, A. (1978) Geological occurrences ofzeolite in marine environments: in Natural Zeolites--Occurrence, Properties, Use, L. B. Sand and F. A. Mumpton, eds., Pergamon Press, New York, 175-198. Ingle, J. C., Jr. (1981) Origin ofNeogene diatomites around the north Pacific Rim: in The Monterey Formation and Related Siliceous Rocks of California, R. E. Garrison and R. G. Douglas, eds., Pacific Section SEPM, 159-180. Isaacs, C.M. (1980) Diagenesis in the Monterey Formation examined laterally along the coast near Santa Barbara, California: Ph.D. thesis, Stanford University, 329 pp. Isaacs, C. M. (1982) Influence of rock composition on kinetics of silica phase changes in the Monterey Formation, Santa Barbara area, Califomia: Geology 10, 304-308. Isaacs, C. M., Keller, M. A., Gennai, V. A., Stewart, K. C., and Taggart, J. E., Jr. (1983) Preliminary evaluation of Miocene lithostratigraphy in the Point Conception COST well OCS-CAL 78-164 No. 1, off southern California: in Petroleum Generation and Occurrence in the Miocene Monterey Formation, California, C. M. Isaacs and R. E. Garrison, eds., Pacific Section SEPM, 99-111. Jadgozinski, H. (1949) Eindimensionale Fehlordnung in Kristallen und ihr Einfluss auf die Riintgeninterferenzen. I. Berechnung des Fehlordnungsgrades aus der Rrntgenintensit,ten: Acta Crystallogr. 2, 201-207. Johns, W. D., and Shimoyama, A. (1972) Clay minerals and petroleum-forming reactions during burial and diagenesis: Amer. Assoc. Petrol. Geol. Bull. 56, 2160-2167. Kablanow, R. I., II, and Surdam, R. C. (1983) Diagenesis and hydrocarbon generation in the Monterey Formation, Huasna Basin, California: in Petroleum Generation and Occurrence in the Miocene Monterey Formation, California, C. M. Isaacs and R. E. Garrison, eds., Pacific Section SEPM, 53-68. Kastner, M., Keene, J. B., and Gieskes, J. M. (1977) Diagenesis of siliceous oozes--I. Chemical controls on the rate of opal-A to opal-CT transformation--an experimental study. Geochim. Cosmochim. Acta 41, 1041-1059. Kastner, M., Mertz, K., Hollander, D., and Garrison, R. (1984) The association ofdolomitite-phosphorite-chert: Causes and possible diagenetic sequences: in Dolomites of the Monterey Formation and Other Organic-Rich Units, R. E. Garrison, M. Kastner and D. H. Zenger, eds., Pacific Section SEPM 41, 75-86. Keller, W. D., Reynolds, R. C., Jr., and Inoue, A. (1986) Morphology of clay minerals in the smectite-to-illite conversion series by scanning electron microscopy: Clays & Clay Minerals 34, 187-197. Kennett, J. P., McBirney, A. R., and Thunell, R. C. (1977) Episodes of Cenozoic volcanism in the circum-Pacific region: Jour. of Volcanology and Geothermal Res. 2, 145163. McHargue, T. R. and Price, R. C. (1982) Dolomite from clay in argillaceous or shale-hosted marine carbonates: J. Sediment. Petrol 52, 873-886. Mizutani, S. (1977) Progressive ordering ofcristobalitic silica in early stage of diagenesis: Contrib. to Mineral. and Petrol. 61, 129-140. Moore, D. M. and Reynolds, R. C., Jr. (1989) X-Ray Diffraction and the Identification and Analysis of Clay Minerals: Oxford University Press, New York, 332 pp. Murata, K. J. and Larson, R. R. (1975) Diagenesis of Mio-

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