Transcript Geology Field Guide of Jemez Caldera and Capulin Volcano

Geology Field Guide of
Jemez Mountains and
Capulin Volcano
By Dorey Smith
Stop 1 Dinosaur Quarry
• North West Oklahoma • Geology History
– Zuni Sequence
• Exiting Great Plains
– Surface Neogene
– Upper Morison
Formation (Upper
Jurassic)
– Mesozoic sands
• Cross bedded
sandstone (current
activity)
• Easter egg shale
(pastel colors)
• Coarsening upward
• Possible river system or
flood plain
Environment
• Terrestrial
Samples
• Sandstone
current activity
• Shale
Samples
• Slip Slide
• Burrows
Stop 2 Clastic Dikes
• The remains of a
volcanoes innards
• Volcanic plumbing
system
• Remnant of volcanic
cone after erosion
• Vent grow younger as
you move east
Black Mesa
• Pliocene Basalt Flows
• Remnants of Lava
flows after erosion
and streams
broadening their
valleys result in
isolated lava capped
mesas
Stop 3 Chiflo
• Dasite volcanic cone
surrounded by later
flows from other
cones
• Vent of flow is south
of the cone
• Located on edge of
Rio Grande Rift
Samples
• Basalt
– Some olivine crystals
in basalt
Stop 4 Chiflo
Stop 5 Valle Caldera in Jemez
Mountains
• Caldera formed 1.2
Mya
• Ash released was
approximately
300km2 forming the
Tshirege Member of
the Upper Bandelier
Tuff
Stop 5 Bandelier Tuff
Pumas beds several
meters thick from
Valle eruption
Sample
• Pumas
– Dark with obsidian
fragments
– Very viscous
Stop 6 Guaje pumice bed
• Pumas bed
– Light in color without
volcanic glass
fragments
– Less viscous
Stop 7 Basalt flow of the Cerro del
Rio volcanic field
• Basalt flow partially
altered (yellowish
brown in color)
• Guaje Pumice
(1.62Mya)
• Otowi member
• Tshirege Member of
the Bandelier Tuff
Samples
• Basalt flow where it
meets the surface
• Basalt on top, surface
sediments (at time of
eruption) on bottom
• Root cast in sediment
rock under basalt flow
Samples
• Bandelier Tuff
• Crystals in basalt
resulting from slow
cooling
Stop 8 White Rock Overlook
• Looking North
towards Black Mesa
• Mafic flows overlie the
Puye Formation and
the Santa Fe
sedimentary deposits
Stop 9 Capulin Volcano
• Cinder cone
– Eruption from fissure
vent 60,000 years ago
– Molten rock few into
the air and cooled
falling to Earth in small
rocks called cinder
(frothy volcanic rock)
and large chunks
called volcanic bombs
– Form cone shape
around vent
Capulin
• First lava flow was to the
east oozing through the
cinder
• After the gas magma was
depleted the explosive
eruption ended
• The second lava flow was
to the south
• Between the east and
south lava flows there are
wagon track from the
Santa Fe trail
Capulin
• The third flow was to the
southwest.
• The forth flow to the north
east
• The lava flows cover
about 16 square miles
• Ripple marks formed on
the crust as lava
continued to flow showing
the direction of the flow
movement
Capulin
• Center of cone in at a
lesser elevation than
the rim due to the
formation of a cinder
cone
• View of vent in the
cone of volcano
Samples
• Cinder – frothy
volcanic rock very
viscous
• Basalt – with some
viscosity due to slow
cooling
Resources
• www.ees1.lanl.gov/roadgeology.html
• www.nps.gov/cavo/lava.htm