GEOLOGIC MAP OF THE TIERRAS BLANCAS AREA, ESTADO …Rhyolite and dacite lava ˜ows of Cerro Santa...
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MEX 55 MEX 55 2550 2550 2750 2650 2650 2500 2500 2500 2550 2650 2500 2550 2500 2500 2550 2700 TIERRAS BLANCAS LAGUNITA SAN BARTOLO LAS ARENAS SAN PEDRO DE LOS METATES Pastores fault Pastores fault Cerro Santa Lucía 6 60 15 6 12 20 16 18 19 17 21 22 23 24 LP LE LC LA LR CA TE ED 6 10 11 13 15 14 8 9 7 25 1 2 3 4 5 Qa Qc Tr Tr Tr Ta Tv Tv Tv Tv Tv Tr Tr Tr Qva Qvb Qvb Qvb Qvb Qc Qc Qc Qvb Qvb Qvb Qva Qva Qva Qva Qva Qva Qva Qva Qva Qva Qva Qva Qva Qa Qa Qa Qa Qao Qao Qao Qao Qao Qao Qao Qc Qc Qc Qc Qc Qc Qc Qao Qao Qao Qao Qao Qc Qc Qc Qc Qc Qc Qc Qc Qc Qc Qc Qc Qc Qc Qc Qao Qao Qao Qao Qc Qa Qa Qa Qa Qa Qc Qc Qc Qc Qc Qc Qao Qao Qao Qao Qc Qa Qa Qa Qa Qa Qa Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Ttb Tl Tl Tl Tl Tl Tl Tl Tl Tl Tl Tl Tl Tl SB CE A' A 99°51'W 99°52'W 99°53'W 99°54'W 19°53'N 19°52'N 19°51'N 19°50'N 19°54'N 99°51'W 99°52'W 99°53'W 99°54'W 19°53'N 19°52'N 19°51'N 19°50'N 19°54'N SCALE 1:10,000 1 1 2 3 KILOMETERS 0 .5 CONTOUR INTERVAL 10 METERS GEOLOGIC MAP OF THE TIERRAS BLANCAS AREA, ESTADO DE MEXICO Lonnie T. Mercer, Bart J. Kowallis, Eric H Christiansen, and Wade E. Miller, Brigham Young University Oscar Carranza-Castañeda, Universidad Nacional Autónoma de México Isabel Israde-Alcantara, Universidad Michoacana de San Nicolás de Hidalgo Description of Map Units Map Symbols MEASURED SECTION LOCALITY CONTACT -- Dashed where inferred or approximately located. inclined horizontal VOLCANIC VENT STRIKE AND DIP OF BEDS 20 FAULT -- Dashed where inferred or approxi - mately located, dotted where covered; bar and ball on downthrown side. SAMPLE LOCALITY – See map text for description of samples 22 LA N DIGITAL MAP AND CHART SERIES DMCH018 DOI: 10.1130/2014.DMCH018 Published by The Geological Society of America, Inc. 3300 Penrose Place • P.O. Box 9140 Boulder, Colorado 80301-9140 © 2014 The Geological Society of America. All rights reserved. For permission to copy, contact [email protected]. 50 0 100 150 200 m 5x vertical exaggeration Tv Tv Tv Tl Tl Tl Ttb Ttb Ttb Qva Qva Qao Qa Qa Alluvium, unconsolidated sand and gravel in drainages and main graben valley. Colluvium, unconsolidated sand and gravel on slopes. Andesite lava flows, high-K 2 O; 0.4 ± 0.1 Ma; dark gray to black groundmasses with 5-10% plagioclase phenocrysts and sparse pyroxene; abundant xenocrysts of quartz and partially disaggregated clots of glassy feldspar, quartz, and biotite; felsic inclusions are medium grained and up to 1 cm across. Basaltic andesite lava flows and cinder cones, high-TiO 2 ; approx. 0.8 to 1.1 Ma; commonly have gray to dark gray groundmass with <5% plagioclase and pyroxene phenocrysts. Tierras Blancas beds, mammal fossils indicate an age of Late Pliocene to Early Pleistocene; divided into four lithofacies: 1) sandy mudstone, 2) diatomaceous mudstone, 3) massive mudstone, and 4) volcaniclastic sandstone. Lagunita beds, sparse mammal fossils indicate an Early Pliocene age; gray to brown volcanic breccias, very light brown tuffaceous mudstones, two thin distal pyroclastic fall layers, and a 3 m thick ash flow tuff; has five lithofacies: 1) tuffaceous mudstone, 2) volcaniclastic sandstone, 3) lapilli ash-flow tuff, 4) fallout tuff, and 5) volcanic breccia (debris flow/lahar). Tr Rhyolite and dacite lava flows of Cerro Santa Lucia, medium-K 2 O, probably Late Pliocene to Early Pleistocene, light gray groundmass with phenocrysts of plagioclase, quartz, biotite, and amphibole. Intermediate to silicic volcanic and volcaniclastic rocks, Miocene to Pliocene; one low- silica dacite lava flow with light tan to light gray groundmass and no prominent phenocrysts was analyzed from this group. Ta Andesite lava flow, geochemically distinct, medium-K 2 O magnesian, undated but probably Late Pliocene to Early Pleistocene, no clear age relationship with Tierras Blancas and Lagunita beds, so it may be older or younger than they are. Qao Older alluvium, at higher elevations than the current drainage; may include a package of semi-consolidated sand and tuff beds (1.20 ± 0.13 Ma) at the base of the unit (Cemeterio Beds). The age of a fallout ash in this unit is older than the Qva and Qvb ages, but some of the alluvium in this unit is likely also younger than those flows. Qa Qc Qc Qc Qc Qc Qvb Qvb Qvb Tv Quaternary Tertiary A’ A South North Quaternary alluvium and colluvium Andesite lava flows associated with scoria cones, volcanic rock samples: Arenas, Cerro, Chosto, Ejido, Garabato, Lanzados, San Bartolo, Sur, Tejocote. Basaltic andesite lava flows associated with scoria cones. Reverse magnetic polarity correlated to the Matuyama chron (1.1-0.78 Ma), samples Cascada, Cerrito, Metates, Mondragon, Rio, TB Silicic/intermediate lava flows from a parasitic lava dome (Cerro Santa Lucía) on the eastern flank of the early Pliocene San Pedro stratovolcano (Norato-Cortez, 1998), volcanic rock samples D1, D2, DSB, Loma Cementerio beds and older alluvium: Interbedded, tuffaceous, fluvial/alluvial sediments and a tuff unit, volcanic ash samples MX-2000-06, AG-2002-04, AG-2002-08; sandstone samples AG-01-01, AG-03-01, AG-04-03, AG-04-04, AG-06-01, AG-08-01, AG-08-02, AG-08-03, AG-10-01 Tuff - white, distal pyroclastic fall deposit, volcanic ash bed sample AG-2002-14 Intermediate to silicic volcanic rocks exposed in the footwall of the Pastores fault (Aguirre-Díaz et al., 2000), volcanic rock sample Curva Metasedimentary rocks, mafic and felsic dikes. Exposed in footwall of the south-central Acambay graben (Aguirre-Díaz et al., 2000). Angular unconformity 10 m unconformity Sandy mudstone - tan, massive sandy mudstone. Samples AG-06-03 and AG-10-03 Lagunita beds (Tl) unnamed volcanics (Tv) Volcanic breccias - gray to brown, lahar/debris flow breccias Tuff - brown, distal pyroclastic fall deposit. Volcanic ash bed sample AG-2002-12 Lapilli tuff - light gray to white, thin (3 m) ash flow tuff Tuffaceous mudstones and volcaniclastic sandstones, white to light gray, interbedded fluvial and alluvial sediments Late Pliocene - Pleistocene Quaternary Tierras Blancas beds (Ttb) unnamed (Tr and Ta) Tlalpujahua complex: Mesozoic Early Pliocene Miocene - Pliocene (?) Qa Qc Qao Qvb Qva Diatomaceous mudstone - white, laminated lacustrine sediments; all diatom samples Diatomaceous mudstone - white, laminated lacustrine sediments Mudstone - brown, massive marginal lacustrine deposits Volcaniclastic sandstone - thin (5-30 cm) dark gray, fluvial/sheet sandstone, samples AG-02-02, AG-02-03, AG-03-02, AG-05-02. 0.4 ± 0.1 Ma 1.20 ± 0.13 Ma
Transcript of GEOLOGIC MAP OF THE TIERRAS BLANCAS AREA, ESTADO …Rhyolite and dacite lava ˜ows of Cerro Santa...
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GEOLOGIC MAP OF THE TIERRAS BLANCAS AREA, ESTADO DE MEXICOLonnie T. Mercer, Bart J. Kowallis, Eric H Christiansen, and Wade E. Miller, Brigham Young University
Oscar Carranza-Castañeda, Universidad Nacional Autónoma de MéxicoIsabel Israde-Alcantara, Universidad Michoacana de San Nicolás de Hidalgo
Description of Map Units
Map Symbols
MEASURED SECTION LOCALITY
CONTACT -- Dashed where inferred or approximately located.
inclined horizontal
VOLCANIC VENT
STRIKE AND DIP OF BEDS20
FAULT -- Dashed where inferred or approxi-
mately located, dotted where covered; bar and ball on downthrown side.
SAMPLE LOCALITY – See map text for description of samples
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DIGITAL MAP AND CHART SERIES DMCH018DOI: 10.1130/2014.DMCH018
Published byThe Geological Society of America, Inc.3300 Penrose Place • P.O. Box 9140Boulder, Colorado 80301-9140
© 2014 The Geological Society of America. All rights reserved. For permission to copy, contact [email protected].
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Qa Alluvium, unconsolidated sand and gravel in drainages and main graben valley.
Colluvium, unconsolidated sand and gravel on slopes.
Andesite lava �ows, high-K2O; 0.4 ± 0.1 Ma; dark gray to black groundmasses with 5-10% plagioclase phenocrysts and sparse pyroxene; abundant xenocrysts of quartz and partially disaggregated clots of glassy feldspar, quartz, and biotite; felsic inclusions are medium grained and up to 1 cm across.
Basaltic andesite lava �ows and cinder cones, high-TiO2; approx. 0.8 to 1.1 Ma; commonly have gray to dark gray groundmass with <5% plagioclase and pyroxene phenocrysts.
Tierras Blancas beds, mammal fossils indicate an age of Late Pliocene to Early Pleistocene; divided into four lithofacies: 1) sandy mudstone, 2) diatomaceous mudstone, 3) massive mudstone, and 4) volcaniclastic sandstone.
Lagunita beds, sparse mammal fossils indicate an Early Pliocene age; gray to brown volcanic breccias, very light brown tu�aceous mudstones, two thin distal pyroclastic fall layers, and a 3 m thick ash �ow tu�; has �ve lithofacies: 1) tu�aceous mudstone, 2) volcaniclastic sandstone, 3) lapilli ash-�ow tu�, 4) fallout tu�, and 5) volcanic breccia (debris �ow/lahar).
TrRhyolite and dacite lava �ows of Cerro Santa Lucia, medium-K2O, probably Late Pliocene to Early Pleistocene, light gray groundmass with phenocrysts of plagioclase, quartz, biotite, and amphibole.
Intermediate to silicic volcanic and volcaniclastic rocks, Miocene to Pliocene; one low-silica dacite lava �ow with light tan to light gray groundmass and no prominent phenocrysts was analyzed from this group.
TaAndesite lava �ow, geochemically distinct, medium-K2O magnesian, undated but probably Late Pliocene to Early Pleistocene, no clear age relationship with Tierras Blancas and Lagunita beds, so it may be older or younger than they are.
QaoOlder alluvium, at higher elevations than the current drainage; may include a package of semi-consolidated sand and tu� beds (1.20 ± 0.13 Ma) at the base of the unit (Cemeterio Beds). The age of a fallout ash in this unit is older than the Qva and Qvb ages, but some of the alluvium in this unit is likely also younger than those �ows.
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Quaternary
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A’ ASouth North
Quaternary alluvium and colluvium
Andesite lava flows associated with scoria cones, volcanic rock samples: Arenas, Cerro, Chosto, Ejido, Garabato, Lanzados, San Bartolo, Sur, Tejocote.
Basaltic andesite lava flows associated with scoria cones. Reverse magnetic polarity correlated to the Matuyama chron (1.1-0.78 Ma), samples Cascada, Cerrito, Metates, Mondragon, Rio, TB
Silicic/intermediate lava flows from a parasitic lava dome (Cerro Santa Lucía) on the eastern flank of the early Pliocene San Pedro stratovolcano (Norato-Cortez, 1998), volcanic rock samples D1, D2, DSB, Loma
Cementerio beds and older alluvium: Interbedded, tuffaceous, fluvial/alluvial sediments and a tuff unit, volcanic ash samples MX-2000-06, AG-2002-04, AG-2002-08; sandstone samples AG-01-01, AG-03-01, AG-04-03, AG-04-04, AG-06-01, AG-08-01, AG-08-02, AG-08-03, AG-10-01
Tuff - white, distal pyroclastic fall deposit, volcanic ash bed sample AG-2002-14
Intermediate to silicic volcanic rocks exposed in the footwall of the Pastores fault (Aguirre-Díaz et al., 2000), volcanic rock sample Curva
Metasedimentary rocks, mafic and felsic dikes. Exposed in footwall of the south-central Acambay graben (Aguirre-Díaz et al., 2000).
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Sandy mudstone - tan, massive sandy mudstone. Samples AG-06-03 and AG-10-03
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Volcanic breccias - gray to brown, lahar/debris flow breccias
Tuff - brown, distal pyroclastic fall deposit. Volcanic ash bed sample AG-2002-12
Lapilli tuff - light gray to white, thin (3 m) ash flow tuff
Tuffaceous mudstones and volcaniclastic sandstones,white to light gray, interbedded fluvial and alluvial sediments
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Diatomaceous mudstone - white, laminated lacustrine sediments; all diatom samples
Diatomaceous mudstone - white, laminated lacustrine sediments
Mudstone - brown, massive marginal lacustrine deposits
Volcaniclastic sandstone - thin (5-30 cm) dark gray, fluvial/sheet sandstone, samples AG-02-02, AG-02-03, AG-03-02, AG-05-02.
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