Semeniuk & Semeniuk: Wetland sedimentary fill - particles, sediments, classification 
mud", or "calcilutite" (the Latin equivalent for "calcium 
carbonate mud"). The term "calcilutite" has had a 
complex and varied history. Originally introduced by 
Grabau (1903) to refer to limestone composed of mud¬ 
sized calcite, the meaning of the term has since expanded 
to encompass fine-grained limestones, consolidated 
calcareous mud, and unconsolidated calcareous mud 
(Bathurst 1971; Jackson 1997), and from an original 
concept involving only calcitic mud, the term now also 
has broadened in meaning to include aragonitic mud 
(Bathurst 1971). In Western Australia, the term 
"calcilutite" has been used to refer to formations (e.g., the 
Bridport Calcilutite of Semeniuk & Searle 1987) as well as 
consolidated earlier Holocene carbonate deposits 
(Backhouse 1993). In this paper, conforming with the 
now broadened usage, addressing the issue that 
carbonate mud in wetlands of the Swan Coastal Plain can 
grade mineralogically from calcite-dominated to 
aragonite-dominated, and in recognition that the 
majority of mud deposits are calcitic or low Mg calcitic, 
the term "calcilutite" is used to refer to all carbonate 
deposits, whether consolidated, semi-consolidated, or 
unconsolidated, and whether the mud-sized particles 
comprising the calcilutite are wholly calcitic, or 
dominantly aragonitic, or mixtures of calcite and 
aragonite. 
In the literature, water-saturated sand has been 
referred to as "gley", or "gleysol", a term in soil science 
referring to any water-saturated unconsolidated material 
(FitzPatrick 1983; FAO UNESCO 1974; USDA 1975; 
Jackson 1997), particularly if it is anoxic. The original 
term "gley" was a Russian local name for a "mucky soil 
mass", to connote water-saturated conditions, but has 
since been redefined in the Soil Sciences to denote sand 
or soils that are water saturated, in the reduced state 
(ferrous ion) and grey-green, but with ferric mottles, and 
within a zone of fluctuating water table (Hunt 1972, 
Etherington 1983, Mitsch & Gosselink 1986, Sprecher 
2001). However, within the Soil Sciences, there is no 
connotation as to whether the water-saturated sand is a 
transported sediment or in situ soil, as the term can be 
applied to both settings. The term "gley" is not used in 
this paper to denote water-saturated sands because of 
this imprecision, and because the amount of water 
saturation of wetland sedimentary fill is not relevant to 
defining and describing wetland sedimentary material. 
Where quartz sand comprises sedimentary fill as an 
accretionary sedimentary deposit, it is referred to as 
"quartz sand". Where quartz sand comprises the 
Pleistocene basement substrate under the wetland fill 
sequence, it is referred to as quartz sand basement. 
Sediment types, this paper 
Ten main end-member sediment types occur in 
wetlands on the Swan Coastal Plain; they are: 1. peat, 2. 
peat intraclast gravel and sand, 3. calcilutite (carbonate 
mud), 4. carbonate skeletal gravel and sand, 5. carbonate 
intraclast gravel and sand, 6. diatomite, 7. diatomite 
intraclast gravel and sand, 8. kaolinitic mud, 9. quartz 
sand, and 10. quartz silt. Mixtures of these end-member 
sediment types also occur, as will be described later. 
While sponge spicules are a common component of 
wetland sediments, occurring within peat and 
diatomites, generally they do not form "spongolites". 
Usually, where they occur, sponge spicules and 
fragments may constitute up to 10% of a wetland 
sediment, and in this context, the term "spongolitic" 'is 
used as a descriptor to the main wetland sediment name. 
The main sediments that are spicule-bearing are peats 
and diatomites, hence there are "spongolitic peat" and 
Table 3 
Description of the various types of sedimentary structures 
Structure Description/definition 
layered 
laminated 
wispy laminated 
homogeneous or 
structureless 
fibrous 
root-structured 
burrow-structured 
burrow-mottled 
bioturbated 
texture-mottled 
colour-mottled 
fenestral 
vesicular 
brecciated 
sediment with conspicuous layering evident on > 1 cm scale; often sediment is lithologically interlayered 
sediment with conspicuous lamination evident on < 1 cm, and usually < 1 mm scale; lamination can vary from 
regular and even, to wavey and uneven 
sediment with discontinuous lamination, with individual laminae occurring as thin wisps; often the lamination is 
accentuated by compositional differences 
sediment shows no structure and appears texturally and compositionally massive 
prominent structure imparted by random orientation to vertical orientation of plant fibres, roots, and (decayed) 
stems 
prominent structure imparted by ramifying roots 
prominent structure imparted by vertical burrows, where individual burrows are discernible 
prominent structure imparted by burrows, where individual burrows, though overlapping, are still discernible 
and impart a colour or texture mottled appearance to the sediment 
where abundant, and overprinting earlier phases of biological imprints, root-structuring, or burrowing has 
proceeded to the extent that individual root-structures and burrow-structures are not discernible, or only vaguely 
discernible, and there is an overall mottled appearance in the sediment 
where mottling is distinguished by textural differences, eg., sand mottles in mud 
where mottling is distinguished by colour differences 
small flattened cavities, usually parallel to layering, and developed in cemented carbonate intraclast sediment; 
fenestrae are c. 1 mm up to 1 cm in size (cf. Tebbutt et al, 1965; Jackson 1997) 
small open structures produced by bubbles of air or other gases; usually a few millimetres up to 1 cm in size 
sediment exhibiting a fragmented structure, formed by desiccation and cracking at centimetre to metre scale 
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