Page 32 - Carbonate Sedimentology and Sequence Stratigraphy

CHAPTER 2: PRINCIPLES OF CARBONATE PRODUCTION 23

Magnesian Calcite
Fig. 2.15.— Mineralogic composition of sed-
iments of the three factories. C and T factory
M based on X-ray analyses of recent sediments
based on Bathurst (1971), Milliman (1974),
Morse and Mackenzie (1990). M factory based
on point-counting of thin-section micrographs
in Russo et al. (1997), Triassic, and Neuweiler
(1995), Cretaceous. Assumptions: Automicrite
= magnesian calcite; fibrous cements = 1:1
mixture of aragonite and magnesian calcite.

C T
contours of
2x, 8x and 16x
mean data density

Calcite Aragonite

0 T 1 0 M 1 0 C 1 Fig. 2.16.— Production rates and depth win-
0 m dow of production of carbonate factories. Width
of shaded bars represents estimated production
rate at a given depth as a fraction of the tropical
standard. Dominance of photo-autotrophic (i.e.
light-dependent) organisms in the tropical fac-
100 tory leads to very high production rates but only
in a narrow depth window. Production of the
other factories is largely independent of light,
genuine
the depth windows extend over hundreds of me-
drowning
ters and their lower limits are poorly known. In
200 possible
modern oceans, production by the M factory
is low at shallow depths, probably because of
competition by the T factory . After Schlager
(2003), modified.
300

400

500

also: also:
production localized
around methane production on
seeps in deep current-swept
sea deep-sea floors