FACIES ANALYSIS IN THE LOWER GREENSAND USING GROUND-PENETRATING RADAR

被引:33
作者
BRISTOW, C
机构
关键词
CRETACEOUS; SEDIMENTARY ROCKS; INTERTIDAL ENVIRONMENT; GROUND-PENETRATING RADAR;
D O I
10.1144/gsjgs.152.4.0591
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
This paper presents the results of a ground-penetrating radar survey in the Woburn Sands Formation, Lower Greensand Group near Leighton Buzzard. A total of almost 4 km of survey has been acquired to investigate the internal structure of the sands. The radar survey achieved a resolution on the order of tens of centimetres with penetration up to 10 m and revealed a variety of horizontal, dipping and curved reflectors. The reflections are interpreted using seismic interpretation methodology. Two scales of unconformity-defined radar sequences are described. First-order radar sequence boundaries can be identified at the termination of primary reflectors. Second-order radar sequence boundaries can be identified at the terminations of both primary reflectors and first-order surfaces. First-order radar sequence boundaries are interpreted as reactivation surfaces within bedforms which are produced by changes in bedform geometry in response to a change in hydraulic regime or superimposed bedforms. Second-order surfaces are interpreted as the product of bedform migration. Reflection character and geometry are described and form the basis of a ground-penetrating radar facies analysis. Nine different radar facies have been identified. These are interpreted as large sets of planar cross-stratification sets of trough cross-stratification, cosets of cross-stratification tidal bundles, clay drapes, diagenetic concretions and possibly bioturbated sands. A reconstruction of the bedforms suggests that they were formed by very large curved crested dunes. These interpretations are checked against outcrop as the sands are excavated in working sand pits.
引用
收藏
页码:591 / 598
页数:8
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