Holocene alluviation and transgressive dune activity in the lower Manawatu Valley, New Zealand
作者:
M.J. Shepherd,
C.M. Lees,
期刊:
New Zealand Journal of Geology and Geophysics
(Taylor Available online 1987)
卷期:
Volume 30,
issue 2
页码: 175-187
ISSN:0028-8306
年代: 1987
DOI:10.1080/00288306.1987.10422182
出版商: Taylor & Francis Group
关键词: Manawatu;estuaries;Holocene;shells;alluvial plains;accretion rates;sea level;dunes;Foxton Phase;eolian;radiocarbon dating;sand plains;palynology;grain-size analysis
数据来源: Taylor
摘要:
Location of an estuarine bed near Opiki enabled the approximate mid Holocene limit of the Manawatu River estuary to be determined. Since about 6000 years B.P., flood-plain accretion in that area has averaged 1.5 mm/year, although accretion rates may have diminished with time. Two riverbank sections near Rangiotu provide evidence for the initial encroachment of Foxton Phase dunes. Thin sand horizons overlying the former flood-plain surface are identified as eolian veneer deposits, preserved at the rear of former migrating dunes, which constructed sand plains. Radiocarbon dates obtained from interbedded organic material reveal that dunes first entered the area c. 2300 years B.P. with further episodic encroachment until c. 1600 years B.P. As the Foxton Phase dunes had migrated c. 16 km inland there is no absolute date for the commencement of the phase but study of contemporary rates of dun~ advance suggests that the Foxton Phase may have been initiated at the coast about 550~6oo0 calendar years ago.
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