The three-dimensional architecture, spatial complexity, and pore type
distribution, are mapped in a near-surface analog of a coalesced,
collapsed-paleocave system in the Lower Ordovician Ellenburger Group near
the city of Marble Falls in central Texas. The surface area of the site
has approximate dimensions of $\sim$ 350 $\times$ 1000 m. The data
collected include $\sim$12 km of 50 MHz ground penetrating radar (GPR)
data arranged in a grid of orthogonal lines, 29 cores $\sim$15 m length,
and detailed facies maps of an adjacent quarry face.  Electrical property
measurements along with detailed core descriptions were the basis of
integrated interpretation of the GPR data. Three main GPR facies are
defined on the basis of degree of brecciation in the corresponding cores;
undisturbed host rock, disturbed host rock, and paleocave breccia. This
GPR facies division defined the major paleocave trends and the
distribution of porosity types, which correlate with reservoir quality.  
Highly brecciated zones are separated by disturbed and undisturbed host
rock.  The breccia bodies that outline the trend of collapsed cave
passages are up to 300 m wide;  the intervening intact areas between
breccias are up to 200 m wide.  Understanding the breccia distribution in
a reservoir analog will help in defining strategies for efficient
development of coalesced, collapsed paleocave reservoirs.