Paleofloristic assemblages through geological time in Korea

Abstract

Paleofloristic assemblages show various different characteristic features through geological time in Korea. In Korea, paleofloristic assemblages can be separated into the Carbopermian Pyeongan flora, Triassic-Jurassic Daedong flora, Upper Jurassic Myogok flora, Cretaceous Gyeongsang flora and Tertiary geoflora. The upper Paleozoic (Upper Carboniferous-Permian) Pyeongan flora is composed of six floral assemblages: (C 2 1 - C 3 1; C 3 2 - P 1 1; P 1 1; P 1 2; P 2 1 and P 2 2) according to floral compositions. The Triassic-Early Jurassic Daedong flora are characterized by their various gymno-spermous plant aspects. These assemblages indicate low/middle latitude with a swamp/lake lacustrine paleoenvironment according to composition. The Fililcinae is the most characteristic element in number of species and diversity. The ginkgoales and confierales are the sub-dominant elements. These plants are accompanied by non-marine Crustacea (Estheictes) and this aspect also indicate a shallow lake environment. The Upper Jurassic Myogok flora indicate the Tithonian (latest Jurassic) and probably earliest Cretaceous age by the palynomorphic character. These floral constituents are rather different from the lower Daedong and upper Gyengsang floras. The Cretaceous Gyeongsang flora represent the first appearance of the angiosperm plants in Korea. As mentioned, most of constitutants of the plant assemblages indicate lacustirne (swamp/lake) river deposits and a sub-tropical environment is suggested by some cycadeoides trunk fossils. During the Miocene, the eastern part of the Korean peninsular underwent local subsidence, and shallow non-marine sediments were deposited which contain warm/humid climatic plant fossils, coal-bearing formations and tuffaceous rocks. After the events, the marine environment invaded locally along the eastern coast of the peninsula up to the present.