Implications of a sand volcano in the Late
Cretaceous Upper Member of the Wahweap Formation
Wolf, Hannah L.,
Simpson,
Edward
L., Storm,
Lauren P., Tindall,
Sarah
E.,
Wizevich, Michael C., and Simpson, Wendy S., 2008, Implications
of
a sand volcano in the Late Cretaceous Upper Member of the Wahweap
Formation [abs]: Cordilleran Section (104th Annual) and Rocky
Mountain Section (60th Annual) Joint Meeting (19–21 March 2008),
Geological Society of America Abstracts with Programs, Vol. 40, No. 1,
p. 40.
A
vertical slice through a well-preserved sand volcano was discovered 1.8
meters above the base of the Late Cretaceous upper member of the
Wahweap Formation at the Gut in Grand Staircase – Escalante National
Monument, Utah. The internal structure of the sand volcano permits the
reconstruction of the vertical fluid flow pathways and interpretation
of seismogenesis during local faulting.
The 1.3 meter long conduit for the sand volcano cuts across eight beds
composed of lithic sandstone. In its lower reaches the conduit is a
narrow dike-like feature cross cutting a low-permeability fine-grained
sandstone seal. Above the seal, the pipe widens and the pipe edges are
more diffuse in high permeability sandstone, whereas the pipe contracts
in diameter through lower permeability sandstones. The change in
character of the pipe and the structureless sandstone near the pipe
indicates that lateral flow to the conduit was greater in the high
permeability zones. Within the pipe a winnowed concentration of pebbles
30 cm below the vent indicates that vertical fluid flow was of
suffucient velocity to elutriate fine sand forming the surface sand
volcano. The internally massive, cone-shaped surface volcano is
slightly asymmetrical measuring ~120 cm in apparent diameter and ~20 cm
in height. The volcano onlaps the lee face of a fluvial dune.
Modern sand volcanoes often develop with high magnitude seismic events
proximal to faults. This sand volcano is in close proximity to a series
of normal faults with preserved syntectonic deposits in the Waheap
Formation indicating that the fault slip history included some intense
high magnitude seismic activity.
