Geology Reference
In-Depth Information
purity of carbonate rocks. Beyond lithology, a second class
of karst geomorphology is recognized, dependent on the
zonal factors and external factors to classify six climatic-
geomorphologic
alternatively and secondly, that the high-mountain
(alpine) karst landform system with several thousand
meters height difference located within (altitudinally)
different climatic zones, is actually in the same com-
plete karst system geomorphologically, and therefore
within the same geomorphologic region.
According to the methods and criteria mentioned above,
karst landforms in China are divided into eight karst geo-
morphologic regions, i.e., humid tropical karst landform
region (I), humid tropical-subtropical karst landform region
(II), arid-humid subtropical-semihumid temperate karst
landform region (III), humid-semihumid temperate karst
landform region (IV), arid-semiarid temperate karst land-
form region (V), humid tropical-subtropical-humid-semihu-
mid plateau temperate karst landform region (VI), humid
subtropical-semiarid plateau temperate karst landform region
(VII) and plateau-high mountain karst
types
and
seven
karst
landforms,
respectively.
Whole karst landforms and semi-karst landforms can be
separated from non-karst areas by how much non-karst rocks
occur in the region. For example, a terrain is classi
ed into
whole karst area if the non-carbonate clastic rocks are less
than 20 %, otherwise it is classi
ed into semi-karst landform.
The geomorphological approach uses characteristics of
shape and dimensions, and lithologic characters and forma-
tion process of rocks as principal criteria for delineating karst
types. Twenty-three morphological types are thus classi
ed
(Table
1
). The development of the karst landform is com-
plex, inuenced by many factors, and has a variety of
combinations. The geomorphologic types can be vague,
unclear and overlap near the regional boundaries when
making geomorphologic regionalizations. Consequently, the
following methods are used.
(1) The maximum similarity and the minimum differences
of karst landforms are required within each landform
region; however, in different landform regions, the
minimum similarity and the maximum differences of
karst landforms are required.
(2) The combination of karst features and typical forma-
tions should be used to determine a regional boundary.
For example, if the combinations of karst landforms in
humid tropical regions are fengcong (cone karst) but
the typical ones are fenglin (tower karst), then the
regional boundary is designated by the distribution of
fenglin.
(3) Since karsts are widespread throughout China, and
karst landforms are mainly controlled by climatic fac-
tors (Qin et al.
1984
), regional boundaries are deter-
mined,
landform region
(VIII) (Fig.
1
).
3
The Main Features of Karst Landform
Regions
3.1
Humid Tropical Karst Landform Region (I)
This region is situated in the south of the line of Leizhou
Peninsula
Diaoyu and
Chiwei Islands. Its average annual temperature is >22
Penghu Islands
southern Taiwan
-
-
-
C and
its annual precipitation is >1,500 mm (EBPGC
1984
).
It belongs to the Caledonian fold zone of circum-Paci
°
c
tectonic domains in the north and South Sea platform in the
south (CAGS
1975
; Zhang
1983
). Few carbonate rocks were
discovered in southern counties of Hainan Province. They
are Middle-Upper Carboniferous limestone, and Cambrian,
Ordovician carbonate clastic rocks, about 560
930 m thick
(Chen et al.
1988
). They form a small area of fengcong, and
some karst hills.
The karst landform in this region is mainly distributed in
the South China sea area and is characterised by coral reefs
(Huang
1980
). Many coral islands occur within this region
and are widely distributed around the South China Sea
islands and near Taiwan. It is the only region in China which
contains biological (coral reef) karst topography; there is one
national karst geopark in this region.
-
rstly, by different climatic zones, such as
tropical, subtropical, temperate and plateau high-
mountain (alpine) zones, as well as humid, semihumid,
semiarid and arid zones, depending on the main cli-
matic index, as well as temperature, precipitation,
evaporation and dryness. For example, the coral reef
lithology that hosts karsts is distributed in tropical
regions; the tower karst is in the humid tropical-sub-
tropical zone. However, the karst landforms are also
in
uenced by non-climatic factors, such as geological
structure, lithology and topography. So, a comprehen-
sive analysis should be considered to set up the sub-
region boundary.
(4) Karst landforms may be grouped into the same geo-
morphologic regions if they manifest
3.2
Humid Tropical Subtropical Karst
Landform Region (II)
two important
The boundary of the humid tropical-subtropical karst land-
form region is the Qinling Mountains to the north, extending
from Qinling to Dabie mountain, the watershed of Yangtze
River and Huaihe River, and East China Sea to the east,
characteristics,
rstly, that the positive and negative
landforms have formed together and comprise a com-
plete topographical structure (Zhu et al.
1988
); and,
