Sequence Stratigraphy on the Shelf and Upper Slope in Response to the Latest Pleistocene—Holocene Sea-Level Changes off Sendai, Northeast Japan
- David I. M. Macdonald
Published Online: 14 APR 2009
Copyright © 1991 Blackwell Scientific
Sedimentation, Tectonics and Eustasy: Sea-Level Changes at Active Margins
How to Cite
Saito, Y. (1991) Sequence Stratigraphy on the Shelf and Upper Slope in Response to the Latest Pleistocene—Holocene Sea-Level Changes off Sendai, Northeast Japan, in Sedimentation, Tectonics and Eustasy: Sea-Level Changes at Active Margins (ed D. I. M. Macdonald), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303896.ch8
British Antarctic Survey, Cambridge, UK
- Published Online: 14 APR 2009
- Published Print: 13 JUN 1991
Print ISBN: 9780632030170
Online ISBN: 9781444303896
- sequence stratigraphy on shelf and upper slope in response to latest Pleistocene—Holocene sea-level changes off Sendai, northeast Japan;
- depositional sequence - fundamental unit for interpretation of palaeosea-level changes;
- physical oceanographic conditions and surrounding coastal geology;
- relict topography and depositional sequences;
- seaward edge of palaeo-strand plain - as surficial break in slope on middle shelf;
- topographic changes and ravinement surface
The relation of sequence stratigraphy to modern sedimentary environments on a shelf and upper slope is dealt with in this paper. A depositional sequence consisting of three depositional units on the shelf off Sendai, northeast Japan, formed in response to latest Pleistocene–Holocene sea-level changes: unit 1, a coastal sequence and fluvial channel-fills deposited during the fall and lowstand of sea level in the latest Pleistocene; unit 2, a transgressive sand sheet and an onlap sequence deposited from 14 to 6 ka; and unit 3, a modern coastal sequence that developed at present-day sea level during the last 6 ka. The boundary between units 1 and 2 forms a transgressive surface. The surface is sharp on the shelf, and is defined by an erosional ravinement surface. To characterize the transgressive surface, the shelf and upper slope areas can be divided into four regions: inner, middle and outer shelf, and upper slope.
The transgressive sand sheet that widely overlies the transgressive surface is commonly 0.5–1.5 m thick, and consists of very poorly sorted pebbly and muddy sand, bearing mixed-habitat molluscan shell fragments, glauconite, and volcanic grains. This sand sheet is diachronous across the shelf.
At present, the condensed layer, or submarine hiatus, which is recognized above the sand sheet, is generated in response to a very low sedimentation rate in this offshore area. The main part of the condensed section is correlative with the transgressive sand in the outer shelf to upper slope areas. The presence of scattered pebbles or faunal mixing horizons in the condensed section shows the characteristics of the transgressive sand sheet.