Dark Bands in the Submarine Nankai Accretionary Prism – Comparisons with Miocene–Pliocene Onshore Examples from Boso Peninsula - Accretionary Prisms and Convergent Margin Tectonics in the Northwest Pacific Basin - page 236

character cause deformation style

layer-parallel to bedding
no deformed and crushed grains
flakes of clay minerals are concentrated
along the boundary

increase of
pore-fluid pressure
by burial

independent
particulate flow

Type 1-1

oblique to bedding
no deformed and crushed grains
flakes of clay minerals are distributed
pervasively in the dark bands

horizontal tectonic
compression
during accretion

flexural-slip
faults
(thrust sense)

Type 1-2

under submarine landslide
ductile deformation similar to an S-C'
structure

slide planes of
submarine landslides

Type 2 submarine landslides

horizontal tectonic
compression
during accretion

dislocation bedding
inside grains are strongly sheared

thrust faults
with Riedel shears

Type 3

Type 1-1 Type 1-2

bedding plane (sandstone)

host siltstone

ca. 1 mm

ca. 1 km

Type 2 Type 3

rapid loading

bedding plane (sandstone)

bedding plane

horizontal
tectonic
compression

host siltstone

ca. 1 mm

ca. 1 mm

Fig. 6 Classification and formation mechanisms of the dark bands on Boso Peninsula (After
Michiguchi and Ogawa ( 2011 )). Type 1-1 was formed by an increase of pore pressure resulting
from low permeability or liquefaction caused by earthquake shaking during deposition. This
causes independent particulate flow. Type 1-2 corresponds to a flexural-slip fault where, under the
extreme compression of accretion, frictional sliding on the fault is replaced by cataclastic defor-
mation. Type 2 is formed under normal consolidation conditions in the slip plane of a submarine
landslide. Type 3 occurs when, under the extreme compression associated with accretion, the
frictional sliding on a thrust fault is converted to cataclastic deformation