2.4 V olcaniclastic Sediments
71
a
PRIMARY TRANSPORT DISTANCES FROM SOURCE
VOLCANIC ASH FROM ASH CLOUDS
several 100 10 1000 km
DEBRIS FLOWS ANO MUD FLOWS (L AHARS )
0
RY
L-::==================!~:;:;:::?::-: -- ---. -- ---- ~ SEC NDA
I- several 10 10 100 km
TRANSPORT
PYROCLASTIC FLOWS
-------------~
-- several 10 10 100 km
SURGE DEPOSITS
~==-"'! ~~:::::::::-=- I 10 10 km
____________ ---- ------------7
(F LUV1Al.
EOLIAN .
OCEAN
CURRENTS)
-
LAVA FLOWS. BRECCIA. ETC ,
~
-
:::::- 1 10 100 km
---------->
b
CONTINENTAL AND LACUSTRINE ENVIRONMENTS
PROXIMAL
MEDIAL
DISTAL
PLATEAU
VOLC . ASH
VOLC . ASH
LAKE SED 'L-~~~-M~~ __
ELTA .
c
DOMINANT
WINDS
MARINE ENVIRONMENTS
VOLCAN ICLASTIC APRON
ASH TURBIOITES
Fig. 2.27. a Common ranges of primary transport
distances of various tephra. b Volcaniclastics in con(juvenile) and reworked (epiclastic) volcanic material
to the fill of various sedimentary basins is of particular interest. This contribution varies greatly, but only
a few major basin types can be briefly mentioned in
which volcaniclastics play an important part.
Intraplate continental volcanism is associated with
an extensional state of the crnst allowing mantle
tinental environments in relation to distance from
source. c Same as b, but in marine environments.
magma to ascend to the surface. This situation corresponds with the early stage of a continental sag basin
or aulacogen which does not evolve into an advanced
rift zone (see below). The nature of the volcanism is
mostly basaltic, but more acid types also occur. Characteristic features of this volcanism are extensive,
thick lava sheets (plateau basalts), valley fill lavas,
and many cinder cones. In a continental realm, flu-