geological history with a vast array of geological features,
from Archaean terranes to Proterozoic rock systems to
Phanerozoic stratigraphy, lithology, paleontology, mineralization, etc., representing a wide diversity of processes
and products developed under igneous, sedimentary,
metamorphic, pedogenic, metallogenic, hydrologic, and
diagenetic conditions. As such, Australia’s estuaries also
present exceptional geodiversity, reflecting the range of
their geologic, oceanographic, and climatic settings.
Therefore, to provide the framework for a category-based
inventory of sites of geoheritage significance, Brocx and
Semeniuk (2009, 2011) developed the geoheritage tool
kit, to systematically identify and categorize sites of
geoheritage significance. This method has been adapted
to determine the geoheritage values of estuaries. The
geoheritage tool kit uses six steps to identify geological
features across various geological regions and at various
scales, assign geological sites to various categories of
geoheritage, and assess their levels of significance, and case
studies are used here to illustrate the diversity of Australia’s
estuaries (Figure 1; Brocx and Semeniuk, 2009).
Step 1 identifies geological regions, providing a natural
boundary to the estuary being investigated in terms of
geological and geoheritage features, and an indication
of the types of geological features that may be expected.
It also ensures that comparisons in assessing significance are undertaken wholly within similar regions.
Figure 2, for instance, shows the main regions of estuaries in Australia.
Step 2 identifies the geological essentials of a region and
requires listing those geological features that characterize or are peculiar to a given natural region. For an estuary, it involves listing aspects such as the geological
setting, estuary type, effects of climate, oceanography,
and tidal range and interior features (such as flood-tidal
deltas, shoals, tidal flats, deltas, basin type) and
small-scale features (such as mineral precipitations,
bioturbation types, and unusual or distinct sedimentary
structures). The geological essentials of a region can
be identified by drawing on the literature, interviewing
scientists and, after identifying gaps in information,
systematically obtaining further information from fieldwork. The list is termed the “geoheritage essentials” of
an area.
Step 3 allocates each unit of the inventory to a category of
geoheritage, viz., a reference site, cultural site,
geohistorical site, or a modern active landscape, so that
comparisons in assessing significance are undertaken
within similar categories. In regard to reference sites
and/or type locations, once estuaries have been classified as to a type, the reference locations of
end-member type or best example of an estuary can be
identified and allocated as an international or national
heritage locality. In this context, for comparisons of
estuaries for geoheritage evaluation, it is important to
have a worldwide applicable estuarine classification
and nomenclature scheme that can be used systematically and comparatively to differentiate types based on
landform/coastal setting, climate, shape and size of
estuary, tidal and wave regime, sediment assemblages,
seawater/ freshwater mixing style, and biota.
A selection of estuaries that stand out globally as distinct and geomorphically significant because of either
their size, internal landforms, representativeness, or naturalness and that could be used as estuarine reference
sites and/or type locations are Lake St. Lucia (Natal,
South Africa), Solway Firth (Scotland), Gironde Estuary (France), the Elbe (Germany), the deltaic complex
of the Ganges-Brahmaputra (Sundarbans National
Park, India), Walpole-Nornalup Inlet Estuary (Western
Australia), Fitzroy River Estuary (Queensland), Gulf
of Saint Lawrence (Canada), Chesapeake Bay (North
America), and the Amazon Estuary (Brazil).
In regard to cultural or historical significance, estuaries
may function as highly significant systems or may carry
historical significance. The Camargue in the estuary of
the Rhone (France) is an example of the former, and Port
Hacking (Australia) and the Thames (the United Kingdom) are examples of the latter. Estuaries also can function
as geohistorical sites showing ancient sequences where
earth history can be determined. In regard to their stratigraphy and stranded geomorphology, they retain records
over the past 7,000 years when sea level stabilized to its
present position of coastal history and valley-fill history
(Roy et al., 1980). Estuarine sequences that record estuarine evolution in Australia and North America (Fisher,
1969; Roy et al., 1980; Semeniuk, 2000) provide examples of the geohistorical importance of estuaries and illustrate the variety of pathways an estuary may take in its
development. Estuaries also retain records of previous
estuarine history in their stratigraphy and older estuarine
geomorphology.
Estuaries illustrate modern landscapes and settings
where earth processes are still active. They represent an
environment where fluvial sedimentation interacts with
basin processes to mobilize and deposit sediments into
shoals, platforms, and basin-fill sheets. Flood and ebb
tides form flood and ebb tidal deltas, and a plethora of biological, geochemical, hydrochemical, and physical processes at the finest scale result in various sedimentary
deposits, biogenic deposits, sedimentary bedforms and
structures, and mineral precipitates.
Some estuaries may belong to more than one
geoheritage category. For instance, as a World Heritage
area, the estuary of the Ganges-Brahmaputra river system
serves as a reference site and as a location of modern landscapes and settings where estuarine and deltaic earth processes are still active in the largest tidal-dominated
system in the world.
Step 4 allocates the geologic features to a scale, so that
comparative assessments of levels of significance can
be undertaken within a similar scale. The various scales
DETERMINING GEOHERITAGE VALUES
189
from Archaean terranes to Proterozoic rock systems to
Phanerozoic stratigraphy, lithology, paleontology, mineralization, etc., representing a wide diversity of processes
and products developed under igneous, sedimentary,
metamorphic, pedogenic, metallogenic, hydrologic, and
diagenetic conditions. As such, Australia’s estuaries also
present exceptional geodiversity, reflecting the range of
their geologic, oceanographic, and climatic settings.
Therefore, to provide the framework for a category-based
inventory of sites of geoheritage significance, Brocx and
Semeniuk (2009, 2011) developed the geoheritage tool
kit, to systematically identify and categorize sites of
geoheritage significance. This method has been adapted
to determine the geoheritage values of estuaries. The
geoheritage tool kit uses six steps to identify geological
features across various geological regions and at various
scales, assign geological sites to various categories of
geoheritage, and assess their levels of significance, and case
studies are used here to illustrate the diversity of Australia’s
estuaries (Figure 1; Brocx and Semeniuk, 2009).
Step 1 identifies geological regions, providing a natural
boundary to the estuary being investigated in terms of
geological and geoheritage features, and an indication
of the types of geological features that may be expected.
It also ensures that comparisons in assessing significance are undertaken wholly within similar regions.
Figure 2, for instance, shows the main regions of estuaries in Australia.
Step 2 identifies the geological essentials of a region and
requires listing those geological features that characterize or are peculiar to a given natural region. For an estuary, it involves listing aspects such as the geological
setting, estuary type, effects of climate, oceanography,
and tidal range and interior features (such as flood-tidal
deltas, shoals, tidal flats, deltas, basin type) and
small-scale features (such as mineral precipitations,
bioturbation types, and unusual or distinct sedimentary
structures). The geological essentials of a region can
be identified by drawing on the literature, interviewing
scientists and, after identifying gaps in information,
systematically obtaining further information from fieldwork. The list is termed the “geoheritage essentials” of
an area.
Step 3 allocates each unit of the inventory to a category of
geoheritage, viz., a reference site, cultural site,
geohistorical site, or a modern active landscape, so that
comparisons in assessing significance are undertaken
within similar categories. In regard to reference sites
and/or type locations, once estuaries have been classified as to a type, the reference locations of
end-member type or best example of an estuary can be
identified and allocated as an international or national
heritage locality. In this context, for comparisons of
estuaries for geoheritage evaluation, it is important to
have a worldwide applicable estuarine classification
and nomenclature scheme that can be used systematically and comparatively to differentiate types based on
landform/coastal setting, climate, shape and size of
estuary, tidal and wave regime, sediment assemblages,
seawater/ freshwater mixing style, and biota.
A selection of estuaries that stand out globally as distinct and geomorphically significant because of either
their size, internal landforms, representativeness, or naturalness and that could be used as estuarine reference
sites and/or type locations are Lake St. Lucia (Natal,
South Africa), Solway Firth (Scotland), Gironde Estuary (France), the Elbe (Germany), the deltaic complex
of the Ganges-Brahmaputra (Sundarbans National
Park, India), Walpole-Nornalup Inlet Estuary (Western
Australia), Fitzroy River Estuary (Queensland), Gulf
of Saint Lawrence (Canada), Chesapeake Bay (North
America), and the Amazon Estuary (Brazil).
In regard to cultural or historical significance, estuaries
may function as highly significant systems or may carry
historical significance. The Camargue in the estuary of
the Rhone (France) is an example of the former, and Port
Hacking (Australia) and the Thames (the United Kingdom) are examples of the latter. Estuaries also can function
as geohistorical sites showing ancient sequences where
earth history can be determined. In regard to their stratigraphy and stranded geomorphology, they retain records
over the past 7,000 years when sea level stabilized to its
present position of coastal history and valley-fill history
(Roy et al., 1980). Estuarine sequences that record estuarine evolution in Australia and North America (Fisher,
1969; Roy et al., 1980; Semeniuk, 2000) provide examples of the geohistorical importance of estuaries and illustrate the variety of pathways an estuary may take in its
development. Estuaries also retain records of previous
estuarine history in their stratigraphy and older estuarine
geomorphology.
Estuaries illustrate modern landscapes and settings
where earth processes are still active. They represent an
environment where fluvial sedimentation interacts with
basin processes to mobilize and deposit sediments into
shoals, platforms, and basin-fill sheets. Flood and ebb
tides form flood and ebb tidal deltas, and a plethora of biological, geochemical, hydrochemical, and physical processes at the finest scale result in various sedimentary
deposits, biogenic deposits, sedimentary bedforms and
structures, and mineral precipitates.
Some estuaries may belong to more than one
geoheritage category. For instance, as a World Heritage
area, the estuary of the Ganges-Brahmaputra river system
serves as a reference site and as a location of modern landscapes and settings where estuarine and deltaic earth processes are still active in the largest tidal-dominated
system in the world.
Step 4 allocates the geologic features to a scale, so that
comparative assessments of levels of significance can
be undertaken within a similar scale. The various scales
DETERMINING GEOHERITAGE VALUES
189