Prior to the publication of the present map, five colored geologic maps of Taiwan have been published,
the first one in 1898. In addition, one map was published in black and white. The three earliest maps were
accompanied by explanatory texts but the last two maps had no accompanying texts. An historical interest
arises from study of the maps published in past years. These maps illustrate the progress and trends of
geologic study and research and the influence of prevailing hypotheses on the geologic interpretation of
Taiwan with the passage of time. They also indicate the increasing detailed geologic knowledge resulting
from extensive mapping carried out in different parts of this island. This is shown by the expansion of a
legend of six divisions on the 1898 map to 26 units on the 1953 map. This new map has 37 separate map units.
The first general geologic map of Taiwan was compiled by Y. Ishii and published in 1898, only three
years after the island was occupied by the Japanese. The map is titled "A Map of Geology and Mineral
Resources of the Island of Taiwan", and was published at a scale of 1:800,000. An explanatory text appeared
in the same year. No single copy of this oldest geologic map of this island exists today. According to L.S.
Chang (1966), the map legend is subdivided into six subdivisions, using lithologic terms and European systems.
The six units are: gneisses, schists, crystalline limestones, slates, Tertiary system, and Quaternary system.
Rock ages were assigned mostly by comparison with rocks of similar lithology exposed on the islands of Japan.
There inevitably were mistakes in attempting to correlate rock formations over widely separated regions on
the basis of lithology alone. Nevertheless this earliest map still provides a much generalized outline of the
geology of Taiwan as known at that time.
After the outbreak of the war between Japan and Russia in 1904, much attention was paid by the
Japanese government to the coal resources in northern Taiwan and to the indications of oil in central and
southern Taiwan. An island-wide investigation of these fossil fuel resources was undertaken and expanded
geologic surveys in various fields were carried out. During that time, a revised geologic map of Taiwan was
prepared by K. Fukutome and his colleagues to accompany the exhibits displayed at the Anglo-Japanese
Exhibition held in London in 1910. The scale of the map is 1:200,000. This map exists only as a single
colored copy and has never been published. However, the map was later printed in a tricolor edition at a
much reduced scale for general distribution. A short summary entitled "Brief Explanation of the Geological
Formations and Mineral Resources of the Island of Formosa" accompanied the map. In 1911 the second general
geologic map of Taiwan was formally published and was accompanied by a more detailed explanatory text.
This map was compiled by Y. Deguchi and G. Hosoya on a scale of 1:300,000 and included a geologic
cross section. Both geology and mineral resources were shown on the map. This map seems to be an enlarged
version of the earlier tricolor map prepared for the London Exhibition, and is more elaborate than the 1898
map. The legend shows 14 units compared to six in 1898. Six units of igneous rocks, one coralline limestone
unit, and one alluvium unit were added to this map. The geologic age of most of these units was not given
due to lack of adequate data.
After the First World War, the third colored geologic map of Taiwan was published in 1926 under the'
title "Geological Map of Taiwan showing Mineral Distribution". This map was compiled by Y. Ichikawa, a
geologist, and H. Takahashi, a mining engineer. The scale of the map is 1:300,000. The map was accompanied
by three east-west cross sections and by a volume of explanatory text in which the geology was summarized by
Ichikawa and the mineral resources by Takahashi. The legend is subdivided into four groups: Quaternary,
Tertiary, pre-Tertiary, and eruptive rocks. These four groups are further subdivided into 19 units. The age
of most of the igneous rocks was not determined. All the metamorphic and submetamorphic rocks (argillites
and slates) in Taiwan were ascribed to pre-Tertiary age.
The fourth general geologic map of Taiwan was published in 1935. The chief compiler is Y. Ichikawa
and the map scale is 1:500,000. The age groups were the same as those of the 1926 map. However, the legend
is subdivided into 22 units which were designated by formational and series names with a lithologic
description for each. The igneous rocks are divided into an old stage and a young stage. Based on
paleontologic evidence, the slate series in the Central Range was assigned to the Tertiary instead of the
pre-Tertiary. The distribution of mineral resources was also shown on the map. No explanatory text was
prepared to accompany this map.
Since the Restitution of Taiwan at the end of World War II, only one colored geologic map of Taiwan
has been published. This map was published in 1953 by the Geological Survey of Taiwan and was compiled by
L.S. Chang on a scale of 1:300,000. Before the present map was compiled, this was the only available general
geologic map of Taiwan other than the older Japanese maps. This map is without an explanatory text. The
legend is subdivided into 26 units, showing lithologic information for each unit. A detailed subdivision of
the Tertiary into Eocene, Oligocene, Miocene, and Pliocene appears for the first time on this map. The
pre-Tertiary rocks are subdivided into Cretaceous, Mesozoic, and Paleozoic ages. All the major fault lines
were shown so that the general structural features of Taiwan can be outlined. However, many structural lines
were still obscure or dubiously located due to lack of detailed mapping.
In addition to the five published colored geologic maps of Taiwan, another geologic map of Taiwan was
printed in black and white and released in 1971 by the Geological Survey of Taiwan but without a map name.
The map was compiled by T.P. Yen and the original scale is 1:250,000, but the published scale was reduced to
1:1,000,000. The legend shows only 18 units, and the fault lines are also-greatly reduced in number. A broad
grouping of the stratigraphic units into five major age categories is made: Upper Paleozoic, Paleogene,
Miocene, Pliocene, and Quaternary. In addition, four igneous rock types are distinguished: andesite. basalt.
diorite, and gabbro. Formational names are given without lithologic description. No explanatory text is
issued with the map.
The geologic map of Taiwan presented in this text is the most recent map published. The first edition
of this map was published in 1974 at two different scales, 1:250,000 and 1:500,000. The first edition of the
explanatory text of the map was published in December, 1975, entitled "An introduction to the geology of
Taiwan." The second edition of the 1:500,000 geologic map of Taiwan was revised and published in 1986. The
present text is the second edition to explain and discuss the significant geological features shown in the
second edition of the 1:500,000 map.