A STUDY OF THE SURFACE EMERGING PALAEOCHANNELS ON THE SOUTH COAST PLAIN OF LAIZHOU BAY

By employing many methods including distinguishing the land maps, interpreting the aerophotoes and Satellite photographes, consulting historical documents, investigating ancient cultural relics, making investigations in the field, analysing the names and features of the place, and analysing the characteristics of the deposit, etc., a systematic study of the surface emerging palaeochannels on the South Coast Plain of Laizhou Bay has been made. Twenty five surface emerging palaeochannels were discovered and verified. According to the formation age, these palaeochannels were divided into two stages: six palaeochannels were formed in the Early and Middle Holocene, and nineteen palaeochannels were formed in the Late Holocene(the historical period). According to the landform features, the palaeochannels are divided into four categories: upland palaeochannel belts, strip shaped upland palaeochannels, trough shaped depression palaeochannels and ancient riverbeds. Among the four categories, the strip shaped upland palaeochannels are the main types. The swinging and movement of the channels helped the alluvial plains expand and cause the coastal ancient lakes to vanish in succession.

Study on sea water intrusion into palaeochannels on south coastal plain of the Laizhou Bay by the Bohai Sea

The palaeochannel evolution in the study region is divided into four stages by such methods as 14C dating. Sea water intrusion through palaeochannels has been studied as a focal point. Palaeochannels are the main passageways through which the sea water intrudes at a higher speed, through many means and in a changeable dynamic state.

Palaeohydrological reconstructions achieved from palaeoclimatic conditions and palaeochannel morphology for southern Hebei,the North China Plain

Palaeorunoff regimes were reconstructed using the equations relating annual runoff to climatic parameters and palaeoclimatic information acquired mainly by pollen analysis and peat investigation for southem Hebei (114~117°E, 36~38°N) during the last 70 000 years. With the morphological data of palaeochannels preserved in the same region, discharge estimates were calculated with the equations relating discharge to morphological parameters of channel for the palaeorivers acting during the last 25 000 years. For the last 25 000 years, the reconstructed palaeorunoff regimes were compared to the corresponding palaeodischarge ones. This comparison indicates the same trend of hydrological changes occurring in southern Hebei during the last 25 000 years. During 8 000~25 000 or 7 500~25 000 a B.P, the quantity of surface water was rather small and probably just 46 or 60 percent of the one for the interval of 3 000~8 000 or 2 500~7 500 a B.P The surface water was the least during 0~3 000 or 0~2 500 a B.P, being 34 or 33 percent of the one occurring during 3 000~8 000 or 2 500~7 500 a B.P The maximum surface water occurred during 3 000~8 000 or 2 500~7 500 a B.P. when the runoff ranged 147.6~398.0 mm and discharge 210-324 m3/s.

Extraction of palaeochannel information from remote sensing imagery in the east of Chaohu Lake, China

Palaeochannels are deposits of unconsolidated sediments or semi-consolidated sedimentary rocks depos- ited in ancient, currently inactive river and stream channel systems. It is distinct from the overbank deposits of currently active river channels, including ephemeral water courses which do not regularly flow. We have introduced a spectral characteristics-based palaeochannel information extraction model from SPOT-5 imagery with special time phase, which has been built by virtue of an analysis of remote sensing mechanism and spectral characteristics of the palaeochannel, combined with its distinction from the spatial distribution and spectral features of currently active river channels, also with the establishment of remote sensing judging features of the palaeochannel in remote sensing image. This model follows the process of supervised classification → farmland masking and primary component analysis→ underground palaeochan- nel information extraction → information combination→ palaeochannel system image. The Zhegao River Valley in the east of Chaohu Lake was selected as a study area, and SPOT-5 imagery was used as a source of data. The result was satisfactory when this method has been successfully applied to extract the palaeochannel informa- tion, which can provide good reference for regional remote sensing archeology and neotectonic research. However, the applicability of this method needs to be tested further in other areas as the spatial characteristics and spectral response of palaeochannel might be different.

Study of the marine (saltwater) transgression in the palaeo-channels on the south coast plain of Laizhou Bay

The palaeochannels in the studied region are divided into four stages by such methods as 14C dating. Marine (saltwater) transgression in the palaeochannels has been studied as a focal point. Palaeochannels are the main passageway through which the seawater (saltwater) transgresses. The seawater (saltwater) transgresses at a high speed, by many means and in a changeable dynamic state.