The Minerva project is characterized by a sequence of thick bedded limestones with black chert nodules of the Santa Elena formation, overlying the Washita group consisting of interbed
thin clayey and sandy limestones.
In turn, at the depth of 5 m, an interbed
of aggradate muds between sands and gyttia of a similar thickness is not registered on the cumulative resistivity vs.
Leguillon, "The role of the interbed
thickness on the step-over fracture under overburden pressure," International Journal of Rock Mechanics & Mining Sciences, vol.
The complex is dominated by silty bioclastic mudstones and wackestones that interbed
those debrites and turbidites.
A mudstone was silicified to form the microcrystalline silcrete: this was probably an interbed
within the Lower Jurassic sandstone.
Drilling has identified three primary sub horizontal gold zones; an upper zone at the Permian limestone/Tertiary sediment unconformable contact, a middle horizon at a marble/silty limestone interbed
and a lower zone at a volcanic lava/silty limestone contact and a fourth zone of post surface weathering/oxidation of the primary lodes (regolith) occurring in modern karst environment.
This suggests the megaripple sandstone/fine grained sandstone/siltstone interbed
sequence formed in a fluctuating shallow-marine environment characterized by fluctuating energy conditions in which deposition alternated between just below and within wave base.
In the Wulong landslide example (Figure 1.), the main strata are [Q.sup.4] soil, [T.sub.3xj] sandstone and mudstone weak interbed
. The combined strata of [Q.sup.4] soil, [J.sub.2][S.sup.2] sandstone and mudstone is typical at many building sites in the Chongqing urban district, as shown in Figure 2.
One hundred independent quadrats (0.25 [m.sup.2]) were placed on random marks along a 100-m transect, 1.25 m above MLW at two treatment locations: (1) locations behind Spartina beds occupied by at least three cobble beach plant species (bed locations), and (2) locations that were on portions of the shore not bordered by a bed (interbed
locations), but at the same tidal height as the bed locations.
At aquifer depth (~975-1130 m), sandstones interbed
with clay layers; some of which are up to 20 m thick.
The immediate roof of this roadway is siltstone with a thickness of 8~10 m, and the main roof with a thickness of 2~4m is the interbed
of siltstone and fine sandstone.
The laboratory permeability test is widely used, mainly because of its easy operation and simple equipment; however, it has some disadvantages: (1) soil disturbance, (2) inaccurate permeability test, especially sand inclusion or interbed
, (3) not simulating field boundary conditions, and (4) the heavy workload and high cost.