Beach ridges, foredunes or transgressive dunefields? Definitions and an examination of the Torres to Tramandaí barrier system, Southern Brazil

Patrick A Hesp,Nelson L.S Gruber,Elirio E Toldo-Jr,Ricardo N Ayup-Zouain,Luiz J Tomazelli,Luciana S Esteves,Luiz C.P Clerot,Eduardo G Barboza,Luiz L.C De A Tabajara,Sergio R Dillenburg

doi:10.1590/s0001-37652005000300010

Abstract

Many prograded barriers and some dunefields in theworld have been termed 'beach ridge' plains, but the actual genesis of the 'ridges' is often unknown. Use of the terms, berms, beach ridges and foredunes is also confusing in the literature because their definitions are highly variable and are commonly used interchangeably. Thus, the formation and definition of sand berms, beach ridges and foredunes is briefly reviewed. Beach ridges are re-defined as entirely wave formed deposits which are most commonly formed during high wave conditions and/or elevated water levels (e.g. storm surges). Foredunes are formed by aeolian sand deposition in vegetation on the backshore. Some dunefields in Brazil have been called beach ridge plains when they are, in fact, foredune plains, transgressive dunefields, or complex barriers (i.e. barriers comprising two types of dunes). The Holocene barrier extending from Torres to Tramandaí in southern Brazil has been regarded as a beach ridge plain. The landforms of this Holocene barrier comprise wide, relatively linear, widely spaced (400-600m), shore parallel ridges on the landward half, and more closely spaced (80-400m), lobate and crescentic, discrete ridges on the seaward half. Low, rolling dunefields, sand sheets, nebkha fields and deflation plains occur between the ridges. The barrier is re-interpreted as a prograded, transgressive dunefield barrier.

Highlights

In Australia, the USA, Brazil, UK and many other countries, the term ‘beach ridge’ has often been usedPATRICK A
In southern Brazil, the landforms on barriers extending along the coast south of Torres have been termed beach ridges (e.g. Delaney 1963, Godolphim 1983, Villwock 1984)
Beach ridges are here re-defined as swash aligned, swash and storm wave built deposits or ridges formed primarily of sand, pebbles, cobbles or boulders, or a combination of these sediments (Hesp 1999)

Summary

Introduction

In Australia, the USA, Brazil, UK and many other countries, the term ‘beach ridge’ has often been usedPATRICK A. In the Australian and north American literature, the term ‘beach ridge’ was generally, and, in many cases, still is utilized to describe a relict foredune, and beach ridges to describe a foredune plain (i.e. a suite of two or more sand ridges formed originally as foredunes; see Hesp 1983, 1999, 2000 for reviews). The beach ridge is formed at high water levels during storms and higher wave energy events by swash and is generally persistent.

Results

Conclusion