Semeniuk & Semeniuk: Wetland sedimentary fill - particles, sediments, classification 
with fragments c. 1 cm (gravel-sized angular fragments 
of peat), down to sand size (Fig. 5D-F). Chemically, and 
in terms of the texture of the fine-grained organic matter 
that comprise the breccia clasts and sand, they are similar 
to the peat deposits described above. Structurally and 
granulometrically, however, the sediments are 
homogeneous, brecciated to conglomeratic, grading to 
sand-sized clasts of peat, or are layered with alternating 
grain size (pebble-sized, very coarse sand-sized, to coarse 
sand-sized fragments of indurated peat) of breccia and 
conglomerate, and locally root-structured. Texturally, 
these deposits consist of gravel to sand-sized angular to 
rounded clasts of peat set in a fine-grained organic matter 
< 63 pm in size, with root fibres, plant detritus particles 
and scattered quartz sand. Cores through peat intraclast 
gravel and sand show alternating grainsize-differentiated 
layers of peat clasts, and locally, vesicular structure. 
Calcilutite 
Calcilutite is cream, pink, or grey fine-grained 
carbonate sediment (Fig. 5H). The sediment is 
homogeneous, laminated, burrow-mottled, root- 
structured, bioturbated, or colour mottled. Texturally, the 
calcilutite consists of mixtures of silt-sized and clay-sized 
carbonate particles 63 pm to < 1 pm in size, ranging 
down to sediments composed dominantly of carbonate 
clay-sized particles, generally <4 pm. Compositionally it 
is mainly calcite, with lesser amounts of organic carbon. 
In some wetlands, there is admixed Mg-calcite, aragonite 
and dolomite, and in some the muds are dominantly 
aragonitic. The sediment may contain freshwater snails 
and/or pelecypods, and ostracods, as gravel or sand¬ 
sized components, or their comminuted fragments, in 
layers, or scattered in random orientation throughout the 
sediment in low abundance (< 5%). The gradation of 
gravel and sand-sized particles through to clay-sized 
particles with consistent microstructure and 
ultrastructure throughout, together with the elemental 
composition determined by EDS, indicate that the <63 
pm fraction of carbonate particles is the accumulation of 
disintegrated (highly comminuted) mud-sized remains of 
charophytes and calcareous fauna such as molluscs and 
crustaceans. Reflecting the various biotic sources, 
calcilutite particle mineralogy may be calcite, low Mg 
calcite (Mg content 1-4%), high Mg calcite (Mg content 
4-10%), and aragonite, with the particles deriving from 
calcitic shell, or disintegrated charophytes of calcitic or 
Mg-calcite mineralogy, or Mg-calcite shell, or aragonitic 
mollusc shell, respectively). The mineralogy of the mud 
also depends on the range of diagenetic precipitates that 
may occur within the sediment (e.g., aragonite crystal 
sprays, or dolomite). 
Using a modern species of Char a as an example, Figure 
9 A,B,C illustrates the progression from 10-50 micron¬ 
sized aggregates (internally composed of units of micron¬ 
sized carbonate crystals), embedded in the walls of Chara, 
through to particulate carbonate sediment of micron¬ 
sized crystals. Calcilutite composed of fine-grained 
particles derived from invertebrate skeletons is shown in 
Figures 9 E & F. Similar transitions can be documented 
for the disintegration of carbonate-impregnated 
filamentous algae to calcitic and Mg-calcitic mud. 
Carbonate skeletal gravel and sand 
Carbonate skeletal gravel and sand are a cream or 
grey medium to coarse grained suite of sediments. 
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