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Further reading
: K211
significantly increased since the 1980s. Many studies
deal with the impact of siliciclastic sedimentation on
reef growth. Other studies focus on the influence of
siliciclastic influx on the development of carbonate plat-
forms and shelves.
Overviews:
Walker et al. (1983) proposed the first
model for carbonate to terrigenous clastic sequences,
another model was suggested by Mount (1984). Doyle
and Roberts (1988) edited a topic describing the as-
pects of carbonate-clastic transitions in modern envi-
ronments. Lomando and Harris (1991) presented case
studies of ancient mixed carbonate-siliciclastic se-
quences on the scale of core data. Mount (1985) sug-
gested a classification of sediments that are composed
of mixtures of carbonate and siliciclastic material (see
Sect. 8.5; Pl. 49). Important papers on carbonate-si-
liciclastic mixtures were collated in the SEPM Reprint
Series by Budd and Harris (1990).
16.6.1.1 Modern CarbonateSiliciclastic
Environments
Siliciclastic and carbonate sediments are often mutu-
ally exclusive within modern environments because of
the biogenic origin of most carbonates. Fine-grained
siliciclastics frequently dilute carbonate sediments and
negatively effect carbonate production by reducing the
light available to autotrophs and/or covering filter-feed-
ing organisms.
Transitions from siliciclastic to carbonate sedimen-
tation occur in near-coast and inner shelf environments
(Fig. 16.18) where rivers transport eroded terrigenous
material to the sea, and on low to high-latitude shelves.
The input of siliciclastics affects the carbonate produc-
tion of platforms and ramps, and is an important con-
trol on reef growth. The transition between the two
depositional systems is largely controlled by climate,
sea level and tectonic setting, influencing in turn hin-
terland erosion and carbonate production. In equato-
rial settings, siliciclastic or volcaniclastic influx has a
major influence on regional carbonate development,
local carbonate deposition and sequence development
(see Wilson and Lokier 2002 for an excellent study of
causal relationships).
Coeval carbonate and siliciclastic sedimentation re-
quires specific conditions. Terrigenous influx has to be
low enough to allow the growth of carbonate-produc-
ing organisms. This can be achieved by a temporary
shift of the siliciclastic depocenter (e.g. abandonment
of delta lobes), the winnowing of fine-grained mate-
rial by currents, or spatial separation of siliciclastic and
carbonate depocenters.
16.6 Mixed Carbonate-Siliciclastic
Settings and Limestone/Marl
Sequences
The following text deals with carbonates formed in
mixed carbonate-siliciclastic environment and dis-
cusses limestone-marl sequences.
16.6.1 Carbonate-Siliciclastic Environments
Mixtures of siliciclastic and carbonate rocks in shelf
settings are a result of lateral facies mixing, or by sea-
level changes and/or variations in sediment supply caus-
ing vertical variation in the stratigraphic succession.
Having long been neglected, the study of modern and
ancient mixed carbonate-siliciclastic environments has
