Browsing by Author "Baker, Donald R."
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Item A diagenetic study of the lower coralline limestone (oligocene), the Maltese Islands(1980) Budai, Joyce M.; Wilson, James Lee; Baker, Donald R.; Warme, John E.The Maltese Islands are located on a broad platform extending from northern Africa to Sicily which divides the Mediterranean Sea into an eastern and western basin. Strata exposed on the islands range from Upper Oligocene to Upper Miocene in age and are predominantly carbonates with one pelagic shale unit. This study focuses on the lowest formation, the Lower Coralline Limestone which is of Upper Oligocene (Chattian) age. The mid-Tertiary was a tectonically active time in the central Mediterranean. The western Mediterranean basin was forming during the Neogene and tectonic thrusting occurred to the west, north and east of the study area. Malta's location on a shallow, relatively stable platform in the center of a tectonically active Mediterranean places it in an interesting setting for diagenetic study. Unlike Recent carbonate sediments, the original mineralogic composition of the Lower Coralline Limestone was dominated by high magnesian and low magnesian calcite with only minor amounts of aragonite. Such a mineralogic assemblage would stabilize to low magnesian calcite rapidly and could conceivably affect early marine cementation and later episodes of fresh-water diagenesis. Fine-grained, fibrous marine cementation is present, but poorly preserved and limited to packstones and grainstones. Fresh-water, phreatic cements occurring in the Lower Coralline are more varied in crystal habit and abundant than the early marine cements. Three stages of meteoric cementation are recognized. An early period of syntaxial rim cements on echinoid fragments, accompanied or followed by grain compaction, forms the dominant cement type found in these rocks. These overgrowths display stratigraphically continuous luminescent zones like those reported in Mississippian limestones in New Mexico (Meyers, 1974) . The second phase of meteoric cementation produced fine- to medium-grained scal enohedra cement that clearly follows compaction and echinoid overgrowth development. These cements do not luminesce and constitute less than 20 percent of the fresh-water cements. The final stage of fresh-water cementation produced fine to medium grained, equant granular. void-filling spar. Diagenetic features examined in the Lower Coralline Limestone indicate at least two separate episodes of emergence and fresh-water cementation. Timing of emergent periods can be limited by extent of phreatic diagenesis within the lower units exposed on Malta. Stratigraphic relations of overlying formations that have been down-faulted into subsidence structures created by collapse of solution caverns within the Lower Coralline Limestone (Pedley, 1974) and limited erosional contacts in the lower part of the section provide possible times of fresh-water influence. In addition, proposed periods of subaerial exposure coincide closely with eustatic sea level drops described by Vail et al. (1978) .Item A petrologic study of Weddell Sea sediments: implications for provenance and glacial history(1984) Andrews, Barbara Ann; Anderson, John B.; Baker, Donald R.; Bally, Albert W.Knowledge of subglacial geology in Antarctica is restricted due to limited outcrop exposure. Investigations of terrestrially derived sediments deposited on the Antarctic continental margin have proved successful for gaining increased understanding of this ice-covered continent. Petrologic analyses conducted on glacial, glacial marine, and sediment gravity flow deposits from the Weddell Sea continental margin provide important evidence concerning subglacial geology and glacial history of land areas contiguous to the Weddell Sea. Petrologic data validates identifications, originally based on sed imen to 1ogic criteria, of basal tills on the Weddell Sea continental shelf. The presence of basal tills indicates a major expansion and coincident grounding of the East or West Antarctic Ice Sheet to the shelf edge. Petrologic evidence suggests that glacial expansion in the area of study was chiefly that of the East Antarctic Ice Sheet. Basal tills and transitional glacial marine sediments form distinct petrologic provinces on the Weddell Sea shelf. Most province boundaries extend inland parallel to ii reconstructed ice paleoflow lines. Till lithologies are dominated by volcanics and quartzose sedimentary rocks, in contrast to metamorphic outcrops of the Weddell Sea region. Comminution does not effectively bias till composition. Till lithologies suggest that mountainous outcrops are not representative of subglacial geology and that sedimentary basins exist beneath the Antarctic Ice Sheet. Four provenance areas for the Weddell Sea basal tills are modeled; correlations between modeled provenance areas and till petrologic provinces are good. Ice-rafted lithologies are limited in number and do not show the expected varied assemblage of Antarctic rock types. Derivation from a limited source area or from lateral moraines is suggested. Sediment gravity flow deposits from the Weddell Sea continental slope and abyssal plain are compositionally very different. Intracanyon slope debris flows and turbidites, composed chiefly of lithic fragments, were generated from basal tills on the adjacent shelf. Abyssal plain turbidites show substantial quartz enrichment and could not have been sourced directly from shelf tills.Item Carbon and oxygen isotope evolution in the Magnet Cove Complex, Arkansas(1975) Johnson, Michael Lee; Baker, Donald R.The Magnet Cove Complex is a highly differentiated ring dike sequence of alkaline igneous rocks and carbonatite. Analyses of silicate rocks show increasing -values (vs. SMOW) from early to late differentiates: trachyte (+8.6%;), phonolite (+7.9%), nepheline syenites (+8.8 to +9.7%) , jacupriangite (+9.4%), melteigite (+11.%) , ijolite (+11.1%) and late dikes (+12.6 to +13.8%). 6-values of calcites from silicate rocks display a similar trend. Carbonatite, a supposed late-stage differentiate, has a 6 -value of +8.6%. Unexpectedly, this value corresponds with the -values shown by early silicate rocks and associated calcite. OC -values of calcites from the silicate rocks show a decrease with differentiation ranging from -4.8 to -6.7% vs. PDB. Similarly the OC -value of the carbonatite, -5.4, coincides with early rather than late differentiates. Early crystallization and removal of A-enriched mafic minerals shifts the late residuals to higher 6 -values. The 6C -trend is explained by loss of isotopically heavy CO during differentiation. The discrepancy between 6 and 6C values of the late stage silicate rocks and the carbonatite may result from early separation of an immiscible carbonate liquid. The narrow range of 6C values displayed by the complex indicates that the carbonatite carbon source (mantle C?) was uniform in isotopic composition and isotopically similar to supposed sources of carbonatites world wide.Item Carbon and stable carbon isotopes in mantle derived material(1973) Pearson, Daniel B.; Baker, Donald R.In this investigation, three possible forms of carbon were identified in mantle-derived material: volatile carbon (methane and carbon dioxide), residual carbon of uncertain location, and carbonate carbon. Volatiles were separated by vacuum crushing, the residuals and total carbon by vacuum fusion, and carbonate carbon by acid evolution. Isotopic analyses of the evolved gases indicate that the residual carbon has a carbon isotope value of approximately -15% to -2%, the volatile carbon gas has a value of less than -21% , and the carbonate about -6.8%, all values being relative to PDB. The different isotopic values displayed by the separate forms of carbon indicate that there are several forms of carbon in the mantle. Carbon as a volatile phase may be of importance in the magmatic and intrusive processes of mantle material upward into the crust.Item Contact metamorphism of the mancos shale near Crested Butte, Colorado(1974) Capers, William Allen; Baker, Donald R.The objective of this study is to examine the mineralogical transformations across the profile of incipient metamorphism in the Mancos Shale in order to develop a better understanding of the significance of clay mineral assemblages and thermally induced changes for the interpretation of the low temperature history of sedimentary rocks. Particular attention is given to the thermal dehydration of mixed-layer illite-montmorillonite and the relationship this has to similar transformations observed in deep bore-holes. The principal conclusions regarding the preintrusive conditions in the Mancos Shale, the effect of contact metamorphism on the Mancos Shale, and the thermal history of the Crested Butte area are: (1) A preintrusive temperature of about 15°C was attained in the Mancos Shale in the Crested Butte and Glenwood Springs areas as a result of depth of burial. (2) The low temperature contact metamorphic transformations observed in the Mancos Shale are compatible with the transformations observed in the Gulf Coast bore-hole studies when variations due to differing bulk compositions are taken into account. (3) The irreversible decrease in expandability of mixed-layer illitemontmorillonite to a completely dehydrated state occurs as a continuous step with increasing temperature. (4) The complete irreversible loss of expandability of the mixedlayer illite-montmorillonite is the first change in the Mancos Shale which signifies the onset of metamorphism. (5) The process of irreversible dehydration without structural reorganization of the mixed-layer illite-montmorillonite has predominated in the contact metamorphosed Mancos Shale in the Crested Butte area. (6) Excellent correlation is obtained between the temperature dependent changes which have been observed in the organic matter contained in the Mancos Shale and the irreversible dehydration of the mixedlayer illite-montmorillonite. (7) The structural reorganization of the mixed-layer illite-montmorillonite and/or its breakdown with the formation of new phases did not occur in the Mancos Shale until a temperature nearly high enough to form metamorphic biotite was attained. (8) Biotite is the first new product of recrystallization in the Mancos Shale. (9) Theoretical calculations of the thermal distribution around the laccolithic intrusions indicate that they could not have caused the contact metamorphic effects observed at large distances from the contacts. (1) It is apparent that there is an intrusive mass at a relatively shallow depth which is large enough to cause significant contact metamorphic effects over a very large area.Item Incipient metamorphism and the organic geochemistry of the Mancos Shale near Crested Butte, Colorado(1972) Hamilton, J. R. (John Richard), 1934-; Baker, Donald R.The purpose of this study is to examine the changes in the organic matter of a typical organic shale caused by extremely low grade, or incipient, metamorphism and to interpret the geothermal history of the study area. The samples are from the Mancos Shale, taken from an area near Crested Butte, Colorado, where the sediments have been intruded by igneous rocks of Tertiary age and subjected to contact metamorphism. Samples were taken from near the main intrusive trend outward, along the East River and the Slate River, and from near Glenwood Springs, about fifty miles to the north, in order to provide an approximately gradational temperature profile. The bitumen was extracted from the crushed rock by soxhlet extraction with benzene. The extracts were separated into saturate and aromatic fractions via elution chromatography with hexane and benzene, respectively. The saturate fractions were analyzed using gas chromatography. Organic carbon was determined by combusting crushed samples in an induction furnace and measuring the evolved CO2. The principal conclusions drawn from this study were: (1) Metamorphism drastically reduces the amount of extractable bitumen in organic shales. (2) Hydrocarbon content is much more drastically reduced by metamorphism than is organic carbon, i.e., metahydrocarbon morphism reduced the ratio. (3) No relationship organic carbon between metamorphism and saturate/aromatic ratio was found in the Crested Butte samples. (4) Aromatic fractions from metamorphosed samples were lighter in color than those from unmetamorphosed samples. (5) The n-paraffins between C16 and C33 from the unmetamorphosed samples were rather evenly distributed, while those from metamorphosed samples were predominately C16, C17, C18, and C19. Metamorphism decreases the average molecular weight of the n-paraffins. (6) The carbon preference index for the unmetamorphased samples was close to 1. The hydrocarbons were probably somewhat mature before metamorphism occurred. (7) Metamorphism causes an increase in the ratio of iso- and cycloparaffins to normal paraffins. (8) Increased induration of shale and the disappearance of swelling clays were associated with metamorphism. (9) All of the noted changes occurred in approximately the same region, about five to seven miles from the main intrusive trend. The samples from between five and fifteen miles of the intrusive trend resembled the unmetamorphosed samples from Glenwood Springs more closely than they did the samples from within five miles of the trend. Thus, the profile probably does not represent a gradation in temperature, but rather defines two zones, one metamorphic and one submetamorphic. (10) The region of metamorphism may delineate the boundaries of a subjacent igneous mass related to other regional structures.Item Paleoenvironmental and diagenetic implications of selected siderite zones and associated sediments in the Upper Atoka Formation, Arkoma Basin, Oklahoma-Arkansas(1976) Campbell, Michael David; Baker, Donald R.Occurrences of "clayband" and "black-band" siderite and zones of siderite-replaced marine fossils and associated sediments are reported in selected sandstone and shale sequences of the upper Atoka Formation of Arkansas and Oklahoma. Outcrops near Pocola, Oklahoma and Hackett, Arkansas were examined to characterize the paleoenvironmental conditions of deposition that may have promoted the genesis of siderite. Eight types of bedded or redistributed siderite are defined, each showing specific responses to bioturbation, to physical erosion and transport, and to chemical replacement and redistribution. The clay minerals contained within the siderite zones and associated shale consist of kaolinite and illite in nearly equal proportions, with the former also possibly consisting of a kaolinite-type chamosite and the latter consisting of a significant 2M muscovite polytype. Interpretations based on sedimentary structures, texture and mineralogy of the sediments associated with the siderite zones indicate that specific sequences may have been deposited in a tidal flat or intra-deltaic environment in proximity to normal marine conditions. A primary or syngenetic origin is proposed for the bedded types of siderite occurrence. Other sequences indicate that marine conditions also prevailed. Physio-chemical requirements for siderite genesis suggest that siderite does not form syngenetically in a marine depositional environment but could syndiagenetically result under normal post-burial conditions involving organic-rich material (fecal matter?) or a subsurface environment with a high Fe+2:Ca+2 ratio and low SO3 in solution. These conditions could promote characteristic siderization of calcareous material within marine sediments in proximity to or down the geohydraulic gradient from areas of either syngenetically-produced siderite or ironrich subsurface water derived from coal-forming swamps. Paleogeographic control of a siderite facies is a distinct possibility, within certain limits, if syndiagenesis plays a subordinate role in siderite genesis or if the character of the siderization of marine sediments can be contrasted to the character of the siderite formed syngenetically, as indicated in this investigation.Item Petrology and geochemistry of intermediate rocks in gabbro-granite contact zones, Wichita Province, Oklahoma(1981) Kennedy, Jerry Wilson; Powell, Benjamin N.; Leeman, William P.; Baker, Donald R.The investigation of intermediate rocks in two granite-gabbro contact zones in the Wichita province of southwestern Oklahoma has established petrologic and geochemical constraints which suggest intrusive relationships exist between the major silicic and basic plutonic rocks. Field studies of the Poko Mountain area in the eastern portion of the province indicate the contact of the younger granite with the underlying gabbro is discordant and is characterized by the presence of gabbro xenoliths within the granite. Whole-rock and trace element chemistry disclose the intermediate rock found highest in the gabbro section at this exposure is more fractionated than the contact phase of the granite. Negative Eu anomalies demonstrate the granite has experienced strong plagioclase fractionation. The gabbro, however, shows no complimenatry positive Eu patterns. In addition, the plagioclases of the gabbro exhibit reverse cryptic variation with the most calcic plagioclase (An67) being found in the intermediate rock immediately below the granite contact. Petrogenesis of the intermediate rock at Poko Mountain is therefore attributed primarily to crystal fractionation of the gabbro and secondarily to alkali metasomatism from the overlying granite. Examination of the Twin Mountains outcrop in the western part of the province reveals the contact between granite and intermediate rock is knife-sharp. The intermediate rock, originally an anorthositic cumulate, is volumetrically composed of approximately 8% plagioclase but is now identified by a negative Eu anomaly. Contact thermal alteration and resorption of plagioclase within the intermediate rock are evident and indicate disequilibrium. The data suggest the development of the intermediate rock at this locale is due solely to hydrothermal contamination of the basic rock by alkali metasomatism from the adjacent granite. The evidence thus suggests that at neither outcrop are the granites a product of differentiation of the basic rocks. ' Most probably the granites originated by partial melting of the Precambrian granitic basement by upwelling basic magmas during the rifting associated with the evolution of the southern Oklahoma aulacogen.Item Petrology and geochemistry of the Mormon Mountain volcanic field, Arizona(1978) Gust, David A; Baker, Donald R.Geologic mapping, petrologic and geochemical studies have confirmed the existence of a contemporaneous bimodal suite in the Mormon Mountain volcanic field, Arizona. This suite is composed of a transitional alkalic basalt series with high alumina affinities and a calc-alkalic silicic series. The basalts represent a complex interplay of partial melting of mantle pyrolite (.1 per cent water) at depths of 5 to 7 km and fractional crystallization. Two petrogenetic models are proposed for the calc-alkalic series, a co-genetic model and a non co-genetic model, least squares linear mixing calculations, phase chemistry and petrologic observations suggest that the calc-alkalic rocks may be related to the basalts by fractional crystallization of undersaturated amphibole from a hydrous alkali basalt (co-genetic relation). An alternative non co-genetic origin for the calc-alkalic series involves the melting of lower crust material (gabbro or norite). These petrogenetic models can be tectonically related to the Cenozoic activity of the East Pacific Rise and the probable sub-oceanic mantle characteristics of the Basin and Range province.Item Petrology of the Cenozoic volcanic rocks of the basal Clarno Formation, central Oregon(1973) Wilson, Patricia McDowell; Rogers, John J. W.; Baker, Donald R.; Lallemant, Hans G. AvéThe Clarno Formation is a volcanic unit of Eoceneearly Oligocène age in central Oregon. It is unconformably underlain by the Cretaceous clastic rocks of the HudspethGable Creek Formations and succeeded by the tuffs of the John Day Formation. The basal 2-3 feet of the Clarno Formation, consisting of flows, lahars, and pyroclastics, was examined near the town of Mitchell. The flow units were sampled for major element analysis. Analyses were performed for twenty-six basal flows by means of x-ray fluorescence and neutron activation. Several chemical parameters were used to delineate the calcalkaline nature of the basal Clarno Formation: AFM diagrams of Clarno data reveal no iron enrichment; K2O contents range from .4% - 3.56%; KgO/NagO ratios are generally lower than .5* Chemical criteria were also used to classify the Clarno Formation as continental, including: the slope of the potash vs. silica variation diagram, the level of KgO at 55% SiOg, the values of T = [(AlgOg - Na2)/Ti2], and the values of the ratio of total iron to magnesium. An attempt is made to relate the geochemistry of the basal Clarno Formation to the general tectonic regime of the developing continental margin of the Cenozoic Northwestern United States.Item Potassium-argon age and petrography of the Sierra Blanca Peak igneous intrusives Hudspeth County, Texas(1983) Matthews, William K.; Adams, John A. S.; Baker, Donald R.; Bally, Albert W.Rhyolite and diorite intrusives are exposed six miles west of Sierra Blanca (Hudspeth County) in West Texas. StructuraUy, they lie between the relatively undeformed Diablo Platform and the folded and faulted Chihuahua Tectonic Belt (Laramide). In thin sections the rhyolite was homogeneous and the diorite proved more variable in mineralogy. Detailed field mapping (1:24) confirmed the general outlines of the five rhyolite laccoliths described by earlier workers. New details of rhyolite dikes, autobrecciation, and flow banding were recognized. A rhyolite age of 36.1 m.y. was reported by earlier workers. The new mapping documented over fifty previously unreported diorite dikes and sills with a concentrated swarm near Sierra Blanca Peak. A potassium-4/argon-4 age of 88 +4 m.y. from a single hornblende phenocryst from a 3 foot dike in the diorite swarm is the oldest Mesozoic age reported to date in this region. Mineralogical differences between the rhyolite and diorite and the 5 m.y. interval between emplacements increase the probability that they are from unrelated magma sources and different tectonic regimes.Item Structure of the Oxbow area, Oregon and Idaho(1980) Schmidt, William Jay; Lallemant, Hans G. Avé; Baker, Donald R.; Oldow, John S.Item The organic geochemistry and water-rock system across a contact metamorphic profile in the Mancos shale near Crested Butte, Colorado(1982) Cuddihee, John Lee; Baker, Donald R.; Lallemant, Hans G. Avé; Valley, John W.; Heymann, DieterA Mid-Tertiary igneous intrusion into the Upper Cretaceous Mancos Shale provides an excellent natural laboratory to study the thermal effects of an intrusion on the organic geochemistry and water-rock system across a contact metamorphic profile. The intrusion, is believed to have established a high temperature gradient across a two mile long sampling profile. This study investigated the isotopic and chemical evolution of both kerogen and extractable organic material. Kerogen displayed a net weight loss of 11% due to methane generation. Kerogen showed essentially no carbon isotopic change. Bitumen contents decreased dramatically across the profile with a measurable 1.5 per mil depletion in 12C for the highest temperature samples. The relatively unique time-temperature history of the study area, and the difference in the kinetics of bitumen and kerogen degradation, is believed to be responsible for the difference in behavior of kerogen and bitumen. Oxygen isotope ratios of matrix calcite suggest that the calcite exchanged with connate water or a very small volume of meteoric water. The final oxygen isotopic ratio of calcite is a function of temperature and the water/calcite volume ratio. Finally, a thermal model involving conductive heating due to a subjacent extension of the White Rock pluton beneath the study area is shown to be capable of generating a temperature of 3°C.Item The temperature/pressure conditions of grenville-age granulite-facies metamorphism of the Oaxacan Complex, Southern Mexico.(1983) Mora, Claudia Ines; Valley, John W.; Baker, Donald R.; Lallemant, Hans G. AvéCoexisting feldspar thermometry for charnockites and quartzofeldspathic gneisses in the Grenville-age Oaxacan Complex, southern Mexico, yields an average temperature of T=762+5°C at 7kb. Reintegration of coarsely-exsolved perthites yields internally consistent peak temperature estimates. Texturally-homogeneous alkali-feldspar has reequilibrated at low temperature. Unusually extensive solid-solution of albite (Abs to Ab5§) and anorthite (Ang.3 to An^ç) necessitated extrapolation of the Stormer (1975) determinative curves beyond their explicit limits. This results in unreasonably high temperature estimates of up to 975°C for feldspar pairs in which X/yj /^f>.4 and suggests that extrapolation is unwarranted. The distribution of albite between coexisting feldspars is consistent with the shape of the Brown and Parsons (1981) general form for the graphical two-feldspar thermometer. Peak metamorphic pressure was estimated using the Newton and Perkins (1982) anorthite+enstatite=pyrope 2/3 grossular 1/3 + quartz geobarometer which yields P=7.5+lkb. The experimentally determined geobarometer anorthite+ferrosilite=almandine 2/3 grossular 1/3 + quartz (Bohlen et al., 1983) yields P=7.25+lkb. The assemblage dolomite+diopside+forsterlte+calcite restricts the metamorphic temperature to 764°C at PQ) =7kb, calculating from the 5kb experimental reversal of the buffering reaction 3dolomite+ldiopside= 2forsterite+4calcite+2C2 by Kase and Metz (1981). Using the temperature estimated by two-feldspar thermometry, at P=7kb the assemblage buffers the fluid composition to Xco =.8. The estimated pressures and temperatures are consistent with metamorphic conditions indicated by the occurrence of quartz+K-feldspar+garnet +sillimanite+biotite in the pelitic gneisses and orthopyroxene+plagioclase+ garnetjMclinopyroxene in the mafic gneisses of the terrane.Item Thermal metamorphism of the organic matter in the Mancos Shale near Crested Butte, Colorado(1973) Ferreira, Justo Camejo; Baker, Donald R.The area of this study is located in west central Colorado, near the town of Crested Butte. In this area, Cretaceous and Tertiary sedimentary rocks have been intruded by Tertiary igneous rocks. The results of previous work on the organic geochemistry of the Mancos Shale in this area were somewhat unexpected, since a continuous transition from metamorphosed to non-metamorphosed conditions from the hot "backbone” of the Ruby Range outward was not confirmed. Instead, two zones were defined: one very extensive metamorphosed zone and one non-metamorphosed zone. This led to the interesting possibility of an underlying igneous mass as the agent of the observed metamorphic effects. This being the case, all the expected changes in the organic matter in the Mancos Shale would occur in-a narrow, "critical" transition zone. The main purpose of the present investigation was the study of a series of samples from the "critical" zone in order to achieve a better understanding of the thermal history of the area and its metamorphic effects. A continuous transition between the metamorphosed and the non-metamorphosed zone was found well recorded by: total extractable bitumens; ratio hydrocarbons/organic carbon; ratio resins/organic carbon; coal; ratio n-paraffins/iso-cycloparaffins; kerogen; normal paraffin distribution and pristane/phytane ratio. The total extractable bitumens decrease from the nonmetamorphosed to the metamorphosed zone. The same was observed with the ratios hydrocarbons/organic carbon, resins / organic carbon, n-paraffins/iso-cycloparaffins and pristane/phytane. The cbal increase in rank from the non-metamorphosed zone (bituminous) to the metamorphosed zone (semi-anthracite). The thermal alteration index of the kerogen increases from the non-metamorphosed to the metamorphosed zone, the color changing from light brown to black. The n-paraffin distribution in the C13 to C33 interval Shows a predominance of C17, C18 and C19 paraffins In the metamorphosed zone, while in the non-metamorphosed and in the transition zone the n-paraffins are more evenly distributed. The above results strongly suggest an underlying batholith, to which the entire igneous complex must be related. Other interesting conclusions frpm the present study ares 1) The resins seem to be as sensitive as the hydrocarbons to low grade thermal metamorphism; 2) The relative proportion of pristane and phytane decreases with respect to the normal paraffins, and also with respect to the iso-cycloparaffins; 3) The pristane/phytane ratio decreases with increasing metamorphism.