Alluvial fan, braided river and shallow-marine turbidity current deposits in the Port Lazo and Roche Jagu formations, Northern Brittany: relationships to andesite emplacements and implications for age of the Plourivo-Plouézec Group

Author:

WENT DAVID J.

Abstract

AbstractFacies and stratigraphic analysis of the Port Lazo and Roche Jagu formations, together the lower part of the Plourivo-Plouézec Group, suggests deposition in three distinct depositional systems. The lower part of the Port Lazo Formation comprises red conglomerate, sandstone and shale of alluvial fan to alluvial plain origin. A conformable interval of grey sandstone and shale succeeds the lower Port Lazo red beds and records a period of subtidal sedimentation dominated by river-fed, shallow-water turbidity currents (hyperpycnites). The succeeding Roche Jagu Formation comprises red sandstones and shales of braided fluvial origin. It is intercalated with, and succeeded by, andesites. The andesites succeeding the fluvial strata overlie a prominent erosion surface and are lava flows, whereas those intercalated with the fluvial strata are intrusions. Rb–Sr radiometric dating of the andesites at 472+/−5 Ma is commonly used as evidence for the whole Plourivo-Plouézec Group being Early Ordovician in age. However, the stratigraphic relationships and patterns of sedimentation in the Port Lazo and Roche Jagu formations, together with the localized presence of Arumberia, suggest they are most likely of early Cambrian age and related to a phase of post-Cadomian rifting. The facies deposited show both similarities to and differences from neighbouring strata of equivalent age, and highlight the control exerted by sediment load on alluvial and nearshore processes on early Palaeozoic environments.

Publisher

Cambridge University Press (CUP)

Subject

Geology

Reference83 articles.

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3