I 
Semeniuk & Semeniuk: Wetland sedimentary fill - particles, sediments, classification 
MARGINAL FACIES: 
peat intraclast gravel/sand 
carbonate intraclast gravel/sand 
diatomlte Intraclast gravel/sand 
muddy sand, and sand 
CENTRAL FACIES: 
accretionary peat, calcilutite, 
diatomite, phyllosilicate clay, 
shell beds, and their mixtures 
f 
MARGINAL FACIES: 
peat intraclast gravel/sand 
carbonate Intraelost gravel/sand 
diatomite intraclast gravel/sand 
muddy sand, and sand 
Figure 18. The major depositional environments of sedimentary particles and wetland sediments as central facies, marginal facies, and 
basal facies. The relevant sediment types within each facies is listed. 
induration along the margins may extend across the 
entire wetland basin. The term "basal deposits" is applied 
to the infiltrational deposits at the base of the wetland, 
and essentially are buried deposits formed at the time of 
the initiation of wetland sedimentation. 
Discussion and conclusions 
This is the first systematic and formal description of 
wetland sediments on the Swan Coastal Plain. As such it 
provides an inventory of wetland sediment particles, 
wetland sediment types, a standard set of descriptors to 
be included in documentation of wetland sediments, and 
a number of defined terms for future reference. In 
contrast to soil nomenclature systems that involve 
classification of combined (segregated) layers in the 
pedogenic profile, a simple and comprehensive system 
using sedimentary terms has been employed to describe 
and classify wetland sediments in this paper, and 
provide a picture of the internal features of wetland 
sedimentary deposits, i.e., their colour, structure, fabric, 
texture, and composition, that can be employed for 
individual layers in the stratigraphic profile. With 
descriptors such as intraformational, infiltrational, 
accretionary, intrabasinal and extrabasinal, information 
about the genesis of the sediments and nature of the 
processes of sedimentation can be included, thus further 
separating sediment types or sediment facies within 
wetland basins. The descriptive system is not aligned to 
any single objective, such as agricultural use, and this 
independence means it may be used as an adjunct in 
many types of surveys with a variety of purposes. 
In this paper, we emphasise that true soils, as 
pedogenic products on pre-existing parent material, 
should be distinguished from sedimentary products that 
are infiltrational and/or accretionary. In the geohistoric 
reconstruction of wetland development, this is an 
important factor, and will provide a means of 
determining the beginning of a wetland's history, in 
separating deposits that have accumulated as part of the 
wetland from those materials inherited from pre-wetland 
conditions (Semeniuk 2005). 
In terms of the sediments themselves, a wide range of 
mud-sized, sand-sized, and gravel-sized sedimentary 
particles contribute to sedimentary fill underlying 
wetlands, viz., organic mud particles, microcharcoal and 
charcoal, carbonate mud particles, quartz sand and silt, 
diatoms, sponge spicules, mud-sized phyllosilicate 
minerals (kaolin, montmorillonite), goethite mud, 
feldspar silt, heavy minerals, intraclasts, shells and 
fragments, and plant material (plant fibres, detritus, 
leaves, flowers, fruit, twigs, branches and trunks). 
Deposits of invertebrate faunal skeletal material, while 
forming layers and laminae in wetland sediments, do not 
contribute in a major way to the filling of wetland basins 
in the settings of the Spearwood Dunes, Bassendean 
Dunes, and Pinjarra Plain, but can form diagnostic and 
environmentally significant markers within the sediment 
suite. 
The end-member wetland sediments that are the 
dominant and/or key intrabasinal and autochthonous on 
the Swan Coastal Plain are peat, diatomite, and 
calcilutite. These end-member sediments similarly are 
recognised globally as being the predominant 
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