CIG   05423
CENTRO DE INVESTIGACIONES GEOLOGICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Sill-Dominated Clastic Intrusions Sourced from Adjacent Deep-Water Submarine Channels: Geometry and Emplacement Models (Isaac Formation, Neoproterozoic Windermere Supergroup, Southern Canadian Cordillera)
Autor/es:
SCHWARZ, E., AND ARNOTT, R.W.C.
Lugar:
Long Beach, USA
Reunión:
Congreso; 2007 AAPG Annual Convention and Exhibition; 2007
Institución organizadora:
AAPG
Resumen:
AbstractRecently outcrop and seismic examples of postdepositionally
mobilized sediment (injections) have become increasingly recognized, and commonly
occur as bedding-discordant dikes. In strata of the Neoproterozoic Windermere
Supergroup, however, injections are dominated by coarse-grain, bedding-concordant
sills (<2.5 m thick) that typically intrude thin-bedded turbidites. Sills
are most common at the bases of coarse-grained channel fills where they form
sharply-bounded, fingerlike projections that taper and eventually pinch out
over horizontal scales of several meters to 50 meters. Almost invariably the
intrusion fill consists of poorly-sorted, very coarse sandstone with dispersed
granules. Generally grain size varies little along the length of the sill, but
near its terminus fines rapidly. Mudstone clasts are common immediately
adjacent to the channel-fill margin, but decrease rapidly in abundance and size
laterally.
Intrusions are interpreted to be the result of
short-lived, catastrophic fluidization of shallowly-buried channel-fill
sediment. Initially pore-fluid pressures in the sand/gravel channel deposits
were probably elevated by the influx of fluid expelled from adjacent,
compacting, mud-rich, thin-bedded turbidites. Later, pore pressures became
significantly elevated, in some cases by the instantaneous loading of overlying
debris-flow deposits. Sand and granules most probably intruded adjacent strata
as a network of coalescing elements that in many places completely surrounded
and isolated clasts of thin-bedded strata (in-situ brecciation). Further away
from their sediment source (i.e. channel fill) intrusions preferentially
intruded along sand-rich layers in the thin-bedded turbidites, and then thinned
rapidly and terminated. Although dikes are uncommon, these sill-dominated intrusion
complexes may connect adjacent channel-fill deposits and enhance channel
reservoir connectivity.