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Home My WebLink AboutGMC Data Report No. 037PETROLOGIC DESCRIPTION OF AMOCO CATHEDRAL RIVER NO. 1 SANDS by Barbara L. Dutrow Dutrow & Associates 3424 Wen twood Dallas, Texas 75225 December 2, 1982 SUMMARY Petrographic examination RIVER NO. I SAND, showed the 1 ithology to volcanic-rich l itharenites or feldspathic minor amounts of arkose, 1 ithic arkose and the sands were compacted with no remaining of 43 samples from AMOCO CATHEDRAL- be predominately 1 itharenites with only quartzite.* Typical ly porosity. Often vol- canic rock fragments became incoherent with compaction, molding around grains to form an interstitial matrix. Where compaction did not reduce all intergranular voids, authigenic cements formed. The cements are chlorite/smeCtite, laumontite, and carbonate. Veins of laumontite/heulandite cut the volcaniclastic sands. These phases also replace preexisting minerals. The most common accessory minerals were a green hornblendic amphibole, epidote and opaques (clasts and pyrite framboids). An abrupt transition, from the volcanic sands, to silty or sandy mudstones occurs in the interval between 7810' and 8500'. Below this level, the dominant iithology is a hematite-rich mud- stone with minor distinguishable grains of plagioclase and quartz. Pyrite framboids are common as are other opaques which occur in streaks to form pseudo-laminations. Grain sizes given are an average size for the sample. Most iithologies (especially above 7810') are poorly sorted with a large range in grain size. Typically more than one rock type is present in any thin section, consequently greater than one I ithology is described for any one interval. *The classification scheme used is Folk, 1968. CATHEDRAL RIVER SAMPLES CR. 2290-2320 Feldspathic litharenite: coarse sand (.62 mm), very poorly sorted, subrounded to subangular grains with longitudinal to concave grains contacts. Detrital grains: volcanic rock fragments - 55%; plagioclase 20%; quartz - 15%; amphibole - 10%; with minor components of biotite, tourmaline, opaques, apatite. Very compacted, no visible porosity. Plagioclase is altering to clays, laumontite, and sericite. Lithic siltstone' medium silt (.15 mm), poorly sorted subangular to subrounded grains floating in a matrix of squished volcanic rock fragments (compacted tuff?). Detrital grains: volcanic rock fragments - 68%; quartz - 25%; plagioclase - 5%; amphibole - 2%; with minor components of opaques, sphene. Abundant saussuritization. Zeolite (heulandite?) vein, no visible porosity due to small grain size and compaction. Granitoid: composed of coarse grained quartz, plagioclase, hornblende, sphene, and biotite. CR. 2520-2530 Feldspathic litharenite: fine sand (.155 mm), poorly sorted, angular to subrounded grains wi th longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 60%; plagioclase - 25%; quartz - 10%; biotite- 5%. Minor components: amphibole, epidote, opaques. Plagioclase altering to sericite, minor 1 aumonti te. Zeolite (heulandite) vein cutting the incoherent volcanic rock fragment matrix. Compacted with no visible porosity. Feldspathic litharenite: very fine sand (.074 mm), poorly sorted, subrounded grains with longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 65%; plagioclase 25%; quartz - 10%; with minor components of orthopyroxene, epidote, and polycrystalline quartz. Intergranular clays abundant. Less altered to clays than previous sample as the clays are confined to grain boundaries. Some fragments have amphibole and abundant saussurite so that grains are floating in the saussurite. Granitoid: calcite. coarse grained plagioclase and quartz wi th mi nor CR. 2530-2540 Arkose: very fine sand (.093 mm), moderately sorted, subrounded grains with longitudinal grain contacts. Detrital grains: plagioclase - 70%; quartz - 20%; volcanic rock fragments - 10%; with minor amphibole. Plagioclase is altering to sericite. Minor poikilitic laumontite cement. No visible porosity. Feldspathic litharenite: medium sand (.39 mm), poorly sorted, subrounded grains wi th longitudinal to concave contacts. Detrital grains: volcanic rock fragments - 48%; plagioclase -35%; quartz - 10%; amphibole - 5%; opaques - 2%; with minor epidote and biotite. Matrix, composed of squished and compacted volcanic rock fragments, is extremely altered to brown clays. No visible porosity. Feldspathic litharenite: coarse sand (.62 mm), poor to moderately sorted, subrounded to rounded grains with longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 57%; plagioclase - 30%; quartz - 10%; opaques - 3%; with minor amounts of biotite, epidote, and hornblende. Plagioclase is altered to sericite, kaolinite, and laumontite. Mi nor intergranular laumontite is present. Matrix is composed of compacted volcanic rock fragments. No visible porosity. CR. 2820-2830 Litharenite: fine sand (.234 mm), very poorly sorted, subangular to subrounded grains floating in a matrix of incoherent volcanic rock fragments. Detrital grains: volcanic rock fragments - 65%; plagioclase - 20%; quartz - 15%; with minor amphibole, opaques, biotite, epidote and polycrystalline quartz. Hematitic rich matrix, very compacted with no visible porosity. Feldspathic litharenite: medium sand (.312 mm), moderately sorted, subrounded to rounded grains with longitudinal to concave grain contacts. Detrital ~grains: volcanic rock fragments - 70%; plagioclase - 25%; quartz - 5%; with minor biotite, amphibole, polycrystalline quartz. Minor poikilitic laumontite cement with zeolite (clinoptilolite?) vein cutting the matrix. Plagioclase is altered to kaolinite (brown clays) and sericite. Compacted with no visible porosity. CR. 2830-2840 Lithic arkose: medium sand (.30 mm), poorly sorted, to subrounded grains with concave grain boundaries. subangular Detrital grains: plagioclase - 45%; volcanic rock fragments 35%; quartz - 20%; with minor biotite {altering to chlorite) opaques. Plagioclase is altered to kaolinite (brown clays). Compacted with no visible porosity. and Feldspathic litharenite' fine sand (.15 mm), poorly sorted, subrounded grains, with concave grain contacts. Detrital grains' volcanic rock fragments - 60%; plagioclase - 30%; quartz - 5%; amphibole - 5%; with minor biotite (altering chlorite). Plagioclase altering to kaolinite. The sample is characterized by a ubiquitous alteration to brown clays as previous samples. Compacted with no visible porosity. fo Litharenite- very fine sand {.10 mm), poorly sorted subrounded grains floating in a hematitic, clay rich matrix {compacted and altered volcanic rock fragments). Detrital grains: volcanic rock fragments - 75%; quartz - 20%; plagioclase - 5%; with minor amphibole and opaques. Plagioclase is altered to kaolinite (brown clays). Zeolite (heulandite?) vein and isolated patches of carbonate. Compacted with no visible porosity. CR. 3100-3110 Feldspathic litharenite: coarse sand (.62 mm), moderately sorted, subangular to rounded grains with longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 55%; plagioclase - 25%; quartz -'15%; amphibole - 5%; with minor epidote, biotite, polycrystalline quartz, and opaques. Pervasive alteration to yellow-brown clays with clays rimming grains. Mi nor laumontite cement. Zeolite {heulandite?) vein with carbonate occurring in the center of the vein cuts the sample. Compacted with no visible porosity. Additional chips of this composition are very poorly sorted (.15 -1.5 mm) wi th abundant intergranular yellow-brown clays wi th or without saussurite. Litharenite: fine sand (.15 mm), poorly sorted, subrounded grains wi th longitudinal to concave grains contacts. Detrital grains: volcanic rock fragments - 68%; plagioclase - 10%; quartz - 15%; hornblende - 7%; with minor polycrystalline quartz. Grains occur in a matrix of squished volcanic rock fragments with abundant clays. Zeolite (heulandite?) veins cut the sample. Very compacted with no visible porosity. CR. 3150-3160 Feldspathic litharenite: fine sand (.19 mm), poorly sorted subrounded grains with longitudinal to concave contacts. grains Detrital grains: volcanic rock fragments - 62%; plagioclase - 25%; quartz - 10%; amphibole - 3%; with minor opaques, biotite and epidote. Similar to previous sample with incoherent rock fragments altering to clays. Clays are rimming grains. Minor laumontite cement and heulandite(?) as a vein mineral. Abundant saussurite. Compacted with no visible porosity. Additional chips of this composition are present which differ in grain size [coarse silt (.062mm)], and in amounts of constituents ( volcanic rock fragments - 65%; quartz - 20%; plagioclase - 15% : litharenite). Some chips are very fine grained and floating in a matrix of hematite and clays. CR. 3160-3170 Lithic arkose: coarse sand (.7 mm), well sorted, angular to subrounded clasts with longitudinal grains contacts. Detrital grains' quartz - 50%; plagioclase - 20%; vOlcanic fragments - 15%; amphibole -~15%; with minor epidote and opaques. Intergranular clays compacted with no visible porosity. rock Sandy siltstone' coarse silt (.05 mm), well sorted angular to subrounded grains floating in a clay rich matrix. Detrital grains: quartz; plagioclase; volcanic rock fragments; amphibole; and opaques. Clay rich sediment cut by veins of laumontite and opaques. Feldspathic litharenite: coarse sand (.60 mm), very poorly sorted angular to subrounded grains wi th longitudinal grain contacts. Detrital grains: plagioclase - 30%; quartz - 30%; volcanic rock fragments - 31%; amphibole - 3%; biotite - 2%; epidote - 2%; sphene - 1%; and opaques - 1%; with minor polycrystalline quartz. Incoherent rock fragments compri sing matrix. Compacted wi th no visible porosity. CR. 3170-3200 Feldspathic litharenite: fine sand (.16 mm), poorly sorted, subangular to rounded grains with longitudinal to concave'grain contacts .. Detrital grains: v.olcanic rock fragments - 60%; plagioclase - 25%; quartz - 15%; with minor amounts of epidote, amphibole, opaques, biotite, polycrystalline quartz, and sphene. Plagioclase is altered to sericite, laumontite and kaolinite. Matrix consists of squished volcanic rock fragments containing abundant clays. Very compacted with no visible porosity. Arkose: fine sand (.16 mm), poorly subangular to subrounded grains with longitudinal to concave grain contacts. Detrital grains: plagioclase - 60%; quartz - 20%; volcanic fragments - 15%; with minor epidote, muscovite, opaques and rock polycrystalline quartz. Plagioclase is altered to sericite and kaol i ni te. Minor poikilitic laumontite cement with a vein of heulandite(?). Additional chips of this lithology are present but differ in . grain size (medium silt - .03 mm) and have a greater percent of amphibole and epidote grains. Abundant hematite and clays may al so be present. All samples are compacted wi th no vi sible porosity. CR. 3200-3210 Feldspathic litharenite: medium sand (.31 mm), poor to moderately sorted subrounded to. rounded grains wi th longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 50%; plagioclase - 45%; quartz - 5%; with minor epidote, amphibole, polycrystalline quartz, biotite, sphene and opaques. Minor laumontite cement. Intergranular clays are present. Some chi ps of this lithology have- greater amounts of laumontite cement with less volcanic rock fragments, or volcanic rock fragments compacted so as to fill intergranular voids. Compacted wi th no visible porosity. Lithic arkose: coarse siltstone (.062 mm), poorly sorted, angular to subrounded grains with longitudinal to concave grain contacts.. Detrital grains: quartz -40%; plagioclase - 30%; volcanic rock fragments - 25% amphibole '- 5%; with minor biotite, epidote and opaques. -" Abundant intergranular clays from the breakdown of volcanic rock fragments. Many rock fragments incoherent and filling voids. Minor laumontite cement and carbonate clasts. Compacted with no visible porosity. CR. 3390-3400 Lithic arkose: medium sand (.31 mm), poorly sorted, subangular to subrounded grains with longitudinal to concave grain contacts. Detrital grains: plagioclase - 35%; volcanic rock fragments - 30%; quartz - 25%; amphibole - 10%; with minor epidote, biotite, metamorphic rock fragments, opaques, carbonate and saussurite. Plagioclase altered to kaolinite and laumontite, volcanic rock fragments altered to laumontite. Clays rimming grains with poikilitic laumontite cement. Fel dspathic litharenite: sorted, subangular to subrounded grains concave grain contacts.. Detrital grains: quartz - 50%; volcanic plagioclase - 15%; amphibole - 10%; with previous sample. Greater amount of hematite in groundmass medium silt (.031 mm), moderately with longitudinal to rock fragments - 25%; accessory phases as clays. Compacted wi th no porosi ry. Subarkose: fragment composed of fine sand (.234 mm) clasts of polycrystall ine quartz (metamorphic rock fragment) , plagioclase, and quartz; totally carbonate cemented, no visible porosity. CR. 3400-3410 Lithic Arkose: very fine sand (.12 mm), poorly sorted, subangular to rounded grains with longitudinal to concave grain contacts. Detrital grains: plagioclase - 50%; volcanic rock fragments - 23%; quartz - 25%; amphibole - 2%; with minor epidote and opaques. Plagioclase altered to kaolinite. Minor poikilitic laumontite cement. Ubitiquous dusty brown alteration with minor clays rimming grains. Abundant saussurite. The thin section is so thick that most minerals display third order colors, therefore is it nearly impossible to distinquish with certainity the other rock chips. No visible porosity. cR. 3500-3510 Lithic arkose: coarse sand (.78 mm), very poorly sorted, subrounded grains with longitudinal grain contacts. Detrital grains: plagioclase - 45%; volcanic rock fragments - 45%; quartz - 10%; with minor amphibole, epidote, opaques. Plagioclase altered to kaolinite and laumontite. Ubiquitous alteration to brown clays. Minor intergranular calcite. Lithic arkose/feldspathic 1. itharenite: medium sand (.40 mm), poor to moderately sorted, subangular to rounded grains with longitudinal to concave grain contacts. Detritai grains: plagioclase - 30%; quartz - 30%; volcanic rock fragments - 30%; amphibole - 5%; epidote - 5%; with minor cl inopyroxene, saussurite, metamorphic rock fragments, and calcite. Plagioclase altered to kaoiinite. Yellow/brown clays rimming grains and sprinkled throughout sample. Compacted with minor intergranular laumontite cement. No visible poros i ry. Zeol itic vein fragment: Minor plagioclase lath altered to zeoi ires and kaolinite, quartz, hornblende and biotite with a matrix of laths of heulandite?/iaumontite? CR. 3560-3570 Lithic arkose: fine sand (.217 mm), poorly sorted subangular to rounded grains with longitudinal to concave grain contacts. Detrital grains: plagioclase - 40%; volcanic rock fragments - 40%; quartz - 20%; with minor ci inopyroxene, biotite, polycrystall ine quartz and opaques. [Amounts of const i tuents vary throughout the sample]. Plagioclase altered to kaolinite. "Fresher" appearance than previous samples, although a thin coating of brown clays is present. Yellow/brown clays rimming some grains. Minor poikil itic laumontite cement, with minor calcite cement. Additional 'chips of this composition are present but differ: in the amount of brown clays (kaolinite); plagioclase altered to zeolites and kaolinite; presence of biotite, sericite/muscovite, amphibole, epidote, or tourmaline; or compacted volcanic rock fragments forming matrix. No visible porosity in any sample. Altered igneous rock - basalt? Plagioclase laths and microphenocrysts altered to kaolinite and zeol ites, plus epidote in a hematitic-clay rich §roundmass. Laumontite/heulandite vein cutting sample. Metamorphic Rock Fragment: polycrystalline quartz + biotite clase + opaques, al igned. + plagio- $iltstone: coarse silt (.062 mm), quartz and plagioclase grains floating in a matrix of Izematitic clays with calcite cement. CR, 4000-4010 Siltstone: medium silt (.O31 mm), moderately well, sorted subangular to subrounded grains floating in a clay rich matrix (VRF's?). Detrital grains: quartz; plagioclase; biotite; amphibole; and opaques. Abundant yel low clays. Additional fragments have distinquishable grains in the medium sand range (.31 mm) = sandy siltstone. Detrital grains: quartz, plagioclase, polycrystall ine quartz, amphibole, epidote. Very compacted with no visible porosity. Very poorly sorted. Arkose: coarse grains of plagioclase - 50%; and minor amphibole and intergranular detrital clays. quartz - 50%; with CR. 5OO0-5010 Siltstone: fine silt (.O12 mm), moderately to well sorted grains floating in a clay rich matrix. Detrital grains: plagioclase; quartz; opaques; amphibole. Minor carbonate and saussurite in addition to clays. Other chips have mol'e abundant authigenic chlorite/smectite growing radially from grains and less detrital clays/compacted VRF's. Zeol ires (laumontite/heulandite?) surrounding some grains and replacing grains. Compacted with no visible porosity. CR. 5630-5640 Lithic arkose: very fine sand (.124 mm), p.oorly sorted, subrounded grains with concave grain contacts. Detrital grains: volcanic rock fragments - 30%; plagioclase - 25%; quartz - 15%; laumontite - 30% with minor cl inopyroxene, epidote, opaques, amphibole, chlorite and tourmaline. Plagioclase altered to iaumontite, volcanic rock fragments altered to chlorite-rich clays. Poikil itic laumontite (heulandite?) cement throughout matrix and in volcanic rock fragments. Zeol itic vein (iaumontite/heulandite?) cuts sample. G~een clays throughout sample but concentrated in the volcanic rock fragments. Compacted with no visible porosity. Siltstone: coarse silt (.062 mm) , moderately well sorted, subrounded grains with longitudinal grain contacts. Detrital grains: volcanic rock fragments - 50%; quartz - 30%; plagioclase - 20%; with abundant clays and accessory minerals as above, plus polycrystal Iine quartz. Minor laumontite cement with abundant clays (detrital) rimming grains, with a hematitic alteration. Some chips have essentially all hematitic rich clays with few distinguishable grains. Very fine grained, compacted and no visible porosity. Feidspathic l itharenite.' medium sand (.31 mm), moderately sorted, subangular to subrounded grains with longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 50%; quartz - 30%; plagioclase - 20%; with minor epidote, chlorite and opaques. Hematitic rich clays at grain boundaries in addition to saussurite, Compacted with no visible porosity. CR. 5640-5650 Feldspathic litharenite: fine sand (.156 mm), moderately sorted, subrounded grains with longitudinal to concave grain contact-s. Detrital grains: volcanic rock fragments - 60%; plagioclase - 25%; quartz - 15%; with minor chert, polycrystalline quartz, amphibole; epidote, opaques (plus pyrite framboids), biotite and chlorite. Plagioclase altered to zeolites. Abundance of saussurite. Matrix consists of hematitic rich clays (yellow and brown) lining grains and filling interstices. Minor authigenic clay (chlorite/ smectite?) development, and minor zeolites in groundmass. No visible porosity. Additional chips of this l ithology are present but differ in grains size (.062 mm,very fine sand/coarse silt). Zeolite veins (laumontite/ heulandite?) are present. One fragment consists totally of crystalline zeol ires (heulandite/laumontite?). One fragment contains minor carbonate cement. Sil.tstones are also present, as described above. CR. 5830-5840 Litharenite: medium sand (.31 mm), poor to moderately sorted, sub- angular to rounded grains with concave grain contacts. Detrital 'grains: volcanic rock fragments - 70%; plagioclase - 20%; quartz - 10%; with minor polycrystal 1 ine quartz, chert, epidote, biotite, chlorite, or hornblende. Plagioclase is fresh or altered to zeol ites. VRF's altered to clays. Groundmass consists of compacted and crushed volcanic rock fragments (VRF's) with microphenocrysts of plagioclase. Clays are present intergranularly from the breakdown of VRF°s. Amount of clays and grain size is variable throughout the sample. One chip appears to have authigenic hematitic-rich clay, with radial fibers filling interstices. CI inoptiloi ite (heulandite?) vein present. Compacted with no visible porosity. 10 Additional fragments of this I ithology have al 1 the plagloclase altered to zeolites, brown clays rimming grains with kaolinitic alteration throughout the sample. Hornblende and epidote may or may not be present. Fragments of a zeol itic (heulandite/cl inoptilol ire?) vein and a hematitic-rich siltstone (as above) are also present. CR. 5840-5850 Arkose: fine (.186 mm) to medium (.312 mm) sand, moderately sorted, subrounded grains with longitudinal to concave grain contacts. Detrital grains: plagi.oclase - 85%; volcanic rock fragments - IO%, quartz - 3%; amphibole- 2%; with minor opaques, biotite, epidote and chlorite. Plagioclase altered to zeolites and kaolinite. Abundant alteration to brown clays (kaolin'ire), with poikilitic laumontite (heulandite?) cement. Compacted with no visible porosity. Litharenite: medium sand (.312 mm), poorly sorted subangular grains floating in a groundmass of squished and compacted volcanic rock fragments. Detrital grains: volcanic rock fragments - 85%; plagioclase - IO%; quartz - 5%; with minor biotite. Rock fragments altered to clays and saussurite. Pyrite framboids are also present. Authigenic zeol ires are present in groundmass, intergranular and replacing rock fragments. Authigenic clays rimming grains with zeolites filling voids. Very compacted, no visible porosity. Sandy siltstone: fine sand (.156 mm) grains floating in a clay rich matrix (squished volcanic rock fragments). Detritai grains: quartz, polycrystalline quartz, plagioclase, opaques, epidote, and chlorite. Some fragments have a greater amount of opaques and hematite, and chlorite with minor zeol ires rimming and replacing grains. Compacted with no visible porosity. Altered rhyolite fragment: plagioclase laths oriented in a matrix of chlorite/smecti.te (produced from devitrification of glass and alteration of groundmass material). Minor amphibole, biotite and quartz is present. Groundmass altered to clays and zeolites. CR. 6070-6100 Siltstone: coarse silt (.062 mm) moderately sorted, subrounded grains with concave grain contacts. Detrital grains: volcanic rock fragments - 70%; quartz - 20%; plagioclase - I0%; with minor biotite, pyrite framboids, amphibole. VRF's altered to ci'ays, minor saussurite and zeol ires. VRF's compacted and squished to fill interstices, biotite bent. Very compacted. Minor authigenic chlorite/smectite intergranularly. Some grains are compacted so as to produce ! ineation within the samples by al ignment of opaques and clays. Carbonate cement may or may not be present. Extremely compacted with no visible p.o~ros~ty. il Sandy mudstone: hematitic-rich clays forming a groundmass with minor distinguishable grains of quartz, polycrystall ine quartz, plagioclase, pyrite framboids and opaques. Zeol itic vein (cl inoptilol ire?) fragment is also present. CR. 6100-6130 Sill:stone/Feldspathic litharenite: medium silt (.O31 mm), moderately sorted, subrounded g.rains with longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 50%; quartz - 30%; plagioclase- 20%; with minor biotite, epidote and pyrite framboids. VRF's incoherent and forming matrix. Abundant clays rimming grains. Minor authigenic chlorite filling interstices. Extremely compacted, no visible porosity. Additional fragments of this composition may have less interstitial VRF's comprising matrix and a greater amount of authigenic chlorite and zeolites in interstices. Zeolites form plagioclase and as discrete clasts. Grain size is variable, as is the amount of saussurite and hematite and carbonate. Carbonate totally cements some fragments. Veins of cl inoptilol ite/heulandite? with or without carbonate. , CR. 6800-6810 Siltstone/Litharenite: coarse silt (.062 mm), moderately well sorted, subrounded grains with longitudinal to concave grain contacts in a matrix of compacted volcanic rock fragments. Detrital grains: volcanic'rock fragments - 55%; quartz - 30%; plagioclase - 15%; with minor epidote, amphibole, carbonate, chlorite, pyrite framboids. Plagioclase altered to zeol ires, VRF's altered to clays. Variable degrees of saussurite and intergranular volcanic rock frag- ments. Grain size vari'es but l ithology remains constant. Extremely compacted with no visible porosity. Arkose.' very fine sand (.124 mm), moderately sorted, subrounded float ing in carbonate cement. Detrital grains: plagioclase - 60%; volcanic rock fragments - quartz - 20%; with minor opaques. Totally carbonate cemented, with no visible porosity. Additional fragments of this lithology contain amphibole epidote, with no calcite cement. Here compacted VRF' Minor zeol ites are present in the groundmass and as products of plagioclase. Hematitic-rich siltstone fragments are also present. and/or grains 20%; s form matrix. al terat ion CR. 701 0-7020 Litharenite: very fine sand (.093 mm), poorly sorted, subangu~lar to rounded grains with longitudinal to concave grain contacts or floating in a matrix of volcanic rock fragments. Detritai grains: volcanic rock fragments - 65%; quartz - 20%; plagioclase - 15%; with pyrite framboids. 12 Variable amounts of hematite and saussurite are present in the groundmass. Plagioclase altered to zeolites as well as VRF's. Feldspathic litharenite: very fine sand (.124 mm), moderately sorted subangular grains in a matrix of incoherent volcanic rock fragments. Detrital grains: volcanic rock fragments - 65%; plagioclase - 25%; quartz - IO%. Similar to the above sample but a greater abundance of volcanic rock fragments (most of which are altered to zeolites and clays), and plagioclase with less quartz. Extremely compacted with veins of opaques. CR. 7020-7030 I. itharenite: very fine sand (.078 mm), moderately sorted, subangular to subrounded grains with longitudinal to concave grain boundaries. Detrital grains: volcanic rock fragments - 55%; quartz - 30%; plagioclase - 15%; with minor opaque clasts, carbonate and laumontite. Abundant pyrite framboids. VRF's altered to clays and filling interstices. Clays rimming grains and filling voids. Extremely compacted with no visible porosity. Additional fragments fine sand (.234) and include: epidote, bi quartz~ clay cl'asts with no visible poro are also l itharenites but variable sizes, medium silt (.O31 mm). Accessory minerals otite, cl inopyroxene, opaques, polycrystal 1 ine and minor carbonate. Also extremely compacted sity. Textural features are as above. Lithic arkose: medium sand (.468 mm), moderately sorted, subrounded grains with longitudinal to concave grain boundaries. Detrital grains: plagioclase - 35%; quartz - 35%; volcanic rock fragments 35%; with minor amphibole, biotite, opaques and pyrite framboids (rimmed by sphene). Plagioclase altered to kaolinite, zeolites; biotite to chlorite. Grains are rimmed by clays in addition to intergranular clays. Compacted with no visible porosity. CR. 7380-7390 Litharenite: very fine sand (.093 mm), moderately sorted, subangular grains-with longitudinal to concave grain contacts in a matrix of incoherent volcanic rock fragments. Detritai grains: volcanic rock fragments - 65%; quartz - 20%; plagioclase - 15%; with minor cl inopyroxene amphibole, epidote, opaques, carbonate, pyrite framboids, chlorite and polycrystal 1 ine quartz. Volcanic rock fragments altered to clays and zeol ires; plagioclase altered to zeol ires. Abundant intergranular authigenic chlorite/smectite filling interstices, I ining grains and replacing clasts. Some clay is hematite rich. Very compacted with no visible porosity. Feldspathic 1 itharenite: fine sand (.234 mm), moderately sorted, subrounded grains with longitudinal to concave grain contacts. 13 Detri tal grains.' volcanic rock fragments - 40%; quartz - 20~; plagioclase - 15%; matrix clays - 25%; with minor polycrystalline quartz, amphibole, epidote and opaques. Greater amount of hematitic-rich clays intergranular and rimming grains. Chlorite/smectite fi 11 lng interstices. Compacted with no visible porosity. $iltstone: medium silt (.O31 mm), similar in appearance and composition to the I|tharenite fragment. CR. 7580-7590 Litharenite: fine sand (.155 mm), moderately sorted, subrounded grains with longitudinal to concave grain contacts. Detritai grains: volcanic rock fragments - 55%; quartz .- 30%; plagioclase - 15%; with minor amphiboles and opaques (as clasts and as pyrite framboids). VRFIs altered to clays, plagioclase altered to kaolinite and zeolites. Compacted, the intergranular hematitic-rich clays appear detrital in origin. No visible porosity. Feldspathic l itharenite: very fine sand ( 093 mm), moderately sorted, subrounded grains with concave grain contacts. Detrital grains: volcanic rock fragments - 50%; plagioclase - 25%; quartz - 25%; with minor polycrystalline quartz, amphiboles, epidote, chlorite clasts and opaques (clasts and framboids). Plagioclase altered to kaolinite, VRF's altered to clays (chlorite/ smectite) and zeol ires. Clays rimming grains, incoherent VRF's comprising matrix. Very compacted with no visible porosity. Arkose.' very fine sand (.093 mm), moderately well sorted, subrounded grains floating on a matrix of carbonate (siderite?) cement. Detritai grains: qt~artz - 15% plagioclase - IO%; opaques - 10%; carbonate - 65%; with minor amphibole and pyrite framboids. Totally carbonate cemented with no visible porosity. CR. 7590-7620 Feldspathic I itharenite: very fine sand (. 12 mm) , moderately sorted, subangular to subrounded grains with longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 45%; plagioclase - 30%; quartz - 20%; polycrystall ine quartz - 5%; with minor epidote, opaques, calcite and laumontite. Plagiocl~se altered to kaolinite as wel I as VRF's. Minor micritic calcite and iaumontite distributed throughout the slide. Incoherent VRF's forming matrix, very compacted with no visible porosity. Litharenite: very coarse sand (l.I mm), poorly sorted, to subrounded grains with concave grain boundaries. Detrital grains: volcanic rock fragments - 65%; quartz plagioclase - IO%; opaques - 5%; with minor chlorite and subangu 1 a r - 20%; laumont i re. 14 Plagioclase altered to kaolinite, VRF's altered to kaolinite and zeol ires. Patchy micritic calcite in samples as well as laumontite. VRF's incoherent, compacted to produce matrix. No visible porosity. Altered glass?: vermicular chlorite/smectite masses of radial fibers with minor interstitial hematite and laumontite. Chlorite/ smectite - 80%; laumontite - i0%; hematite - 10%. No visible porosity. CR. 7800-7810 Feldspathic 1 itharenite: fine sand (.21 mm) , moderately sorted, subangular to subrounded grains with longitudinal grain contacts. Detrital grains: volcanic rock fragments - 50%; plagioclase - 25%; quartz - IO~; calcite - 15%; with minor chlorite and epidote. Plagioclase~'~:~red to kaolinite as well as volcanic rock fragments. Minor authigenic chlorite,,cement, and laumontite. Less clays rimming grains. Compacted with no visible porosity. Silty mudstone: Hemat. itic clay (.OO3.mm) rich min.or silt (.03 mm) grains. Detrital grains: plagioclase, quartz, epidote, Plagioclase is well twinned and unaltered. Extremely compacted with no Visible porosity. matrix supporting opaques and laumontite. Altered glass?/voicanic: vermicular chlorite/smectite masses fibers with interstitial hematite and laumontite. Chlorite laumontite - 10%; hematite - 10%. No visible porosity. of radial - 80%; CR. 8500-8510 Silty mudstone: Minor silt (.03 mm) grains floating in a hematite and opaque, clay-rich matrix. Detrital grains: abundant opaques, quartz, and plagioclase. Minor iaumontite. Very opaque rich, dispersed throughout sample imparting a near black appearance. No visible porosity. Altered glass?: vermicular chlorite/smectite masses of radial fibers, with laumontite and opaques interstitially. Chlorite/smectite - 75%; opaques - 15%; laumontite - 10%. CR. 9080-9110 Sandy mudstone.' Very fine sand (.15 mm) grains floating in a hematitic, clay-rich matrix, with streaks of' opaques defining Iineat ions. Detrital grains: plagioclase, quartz and opaques. Sample cut by carbonate vein. Quartzite: Wel 1 sorted, rounded grains of quartz with interpenetrating grain contacts. Quartz is full of fluid inclusions. Individual grains .2-.7 mm. CR. 94OO-9410 ~5 Silty mudstone: Silt (.02 mm) grains floating in a hematitic, clay-rich matrix with abundant opaques. Detrital grai-r~s:~ 'plagioclase, quartz and opaques. Opaques~occur in streaks which define a l ineation. Sample cut by varbonate veins, one of which has an inclusion of the vermicular chlorite/smectite. Very compacted with no visible porosity. Sil~ty 'mUd'stone: Silt (.06 mm) grains rich matrix. Oetrital grains: plagioclase, quartz Opaques concentrated in the center of throughout sample. Compacted wi th no floating in a laumontite-, and opaques. clasts and clays visible porosity. dispersed Carbonate vein fragment. clay- CR. 9810-9820 Sandy mudstone: Very fine sand (.07 mm) grains floating in of hematite-rich clays and opaques. Detrital grains: plagioclase, quartz, opaques and calcite. Minor calcite and laumontite occur as replacement products of preexisting grains. Opaques streaked and define a l ineation. Very compacted with no visible porosity. Altered glass?: vermicular chlor fibers with hematite filled inter hematite - 15%. ite/smectite masses of radial stices. Chlorite/smectite - Carbonate vein fragment with comb structure. a matrix 85%; CR. I0010-101OO Silty mudstone.' Minor silt (.05 mm) grains floating in a hematite and clay-rich matrix. Detrital grains: quartz, plagioclase, and opaques (plus pyrite framboids). Streaks of opaques define a l ineation. Minor laumontite and carbonate. Carbonate vein cuts sample. Vein also contains euhedral quartz. CR. !0540-10550 Subarkose: fine sand (.17 mm), moderately well sorted, angular to subrounded grains with longitudinal grain contacts. Detrital grains: quartz - 75%; plagioclase - 25%. Plagioclase replaced by laumontite and calcite. Pyrite framboids are also present. Authigenic laumontite, carbonate, and chiorite/smectite are interstitial to grains. Compacted and cemented with no visible porosity. 16 Sandy mudstone: very fine sand (-.1 mm) floating in a hematite and clay-rich matrix with opaques. Detrital grains: plagioclase, quartz and opaques (+ pyrite framboids). Amount of clastic grains and opaques varies throughout sample. Opaques are streaked to form l ineations. Minor laumontite and calcite are dispersed throughout the sample. Sparry calcite veins cut some fragments. Compacted with no visible porosity. CR. IO510-10540 Arkose: fine sand (.12 mm), moderately we.il sorted, subrounded grains with longitudinal grain contacts. Detrital grains: Plagioclase - 70%; quartz - 30%; with minor opaques (ieucoxene, hematite) and chlorite. Carbonate replacing plagioc~i.ase. Interstitial laumontite and carbonate. Minor chlorite (after biotite) and in a vein. Zeolitic veins. Compacted, cemented with no visible porosity. Sandy mudstone: Very fine sand (.07 mm), subrounded grains floating in a hematite, clay-rich matrix or with longitudinal grain contacts. Detrital grains: plagioclase, quartz, chlorite, and opaques. Opaques often streaked to define a l ineation. Laumontite and carbonate within matrix. minor CR. 11000-11010 Sandy mudstone: very fine sand (.O1 mm) floating in a hematite, clay-rich matrix. Detrital grains: plagioclase, quartz, chlorite, and opaclues, which vary in amount throughout the sample. Plagioclase altered to laumontite. Streaks of opaques define lamination. Laumontite and carbonate occur in the matrix. Compacted with no visible porosity. Zeolitic vein (laumontite/heulandite?) fragment composed of zeolite crystals. CR. lIOIO-11020 Silty mudstone: medium silt (.O1 mm) floating in a hematite, clay- rich matrix. Detrital grains: quartz, plagioclase and 6paques (+ pyrite framboids). Plagioclase altered to laumontite and calcite. Streaks of opaques form I ineations. Laumontite and minor calcite interstitially. Additional fragments of the mudstone have carbonate veins cutting the sample. The carbonate is sparry and grew in a comb structure. The fragment is slightly coarser grained (.1 mm), has abundant pyrite framboids and matrix carbonate and laumontite. 17 CR.. 12OOO-12OIO Silty mudstone: medium silt (.02 mm) floating in a hematitic, clay-rich matrix. Detrital grains: plagioclase, quartz, and opaques. , Streaks of opaques, up to I mm in cross-section, define a lamination. Minor laumontite and calcite is present in the matrix. No visible poros i ry. CR. 13280-13310 Lithic arkose: coarse sand (1.4 mm), poorly sorted, subangular to subrounded grains with longitudinal grain contacts. Detrital grains: plagioclase - 65%; volcanic rock fragments - 30%; quartz - 5%; with minor epidote, devitrified glass, opaques and chlorite. Plagioclase altered to kaolinite and laumontite. Carbonate and laumontite veins cut the sample. Compacted with no visible porosity. Silty mudstone: medium silt (.O1 mm) floating in a hematitic, clay- rich matrix. Detrital grains: quartz, epidote, and opaques. Minor carbonate. Streaks of opaques define a lineation within the sample. CR. 13540-13550 Feidspathic 1 itharenite: very coarse sand (1.67 mm), poorly sorted, subrounded to subangular grains with longitudinal to concave grain contacts. Detrital grains: volcanic rock fragments - 50%; plagioclase laumontite - 20%. Plagioclase altered to laumontite. Glass altered to chlorite/smectite. Minor epidote and opaques. Carbonate as a replacement phase within grains and as veins. Compacted with no visi'ble porosity. - 30%; CR. 13550-13560 Silty mudstone: fine silt (.007 mm) floating in clay-rich matrix. Detrital grains: quartz and opaques. Laminations defined by more hematitic rich clays clays. Opaques also form streaks and framboids. Additional fragments of the mudstone have larger of quartz and plagioclase with laumontite .cement. rim grains. Compacted with no visible porosity. a hematitic, and quartz-richer Carboate vein fragment with interstitial ser.icite(?). (.04 mm) clasts Opaques also 18 CR. 14240-14290 Silty mudstone.' medium silt (.02 mm) floating in a hematitic, rich matrix. Detrital grains: quartz, plagioclase and opaques. Opaques occur in streaks which define laminations. Clasts have variable size. Minor calcite is present. Compacted with no visible porosity. clay - Carbonate vein fragment, with or without laumontite. Laumontite vein fragments, with .or to form an intermediate zone between mudstone and the "pure" mudstone. without calcite. These appear the totally carbonate cemented