Deltas:a new classification expanding Bates's concepts  

作　　者：Carlos Zavala Mariano Arcuri Mariano Di Meglio Agustin Zorzano German Otharan Ainara Irastorza Antonela Torresi 

机构地区：[1]Dpto.de Geologia,Universidad Nacional del Sur(UNS),Bahia Blanca,Argentina [2]GCS Argentina SRL,Molina Campos 150,8000 Bahia Blanca,Argentina [3]Consejo Nacional de Investigaciones Científicas y Tecnicas,(CONICET),Buenos Aires,Argentina

出　　处：《Journal of Palaeogeography》2021年第3期341-355,共15页古地理学报（英文版）

基　　金：the continuous support provided by the Departamento de Geologia de la Universidad Nacional del Sur and the CONICET (National Research Council from Argentina)。

摘　　要：Deltas constitute complex depositional systems formed when a land-derived gravity-flow(carrying water and sediments) discharges into a marine or lacustrine standing body of water. However, the complexity of deltaic sedimentary environments has been oversimplified by geoscientists over the years, considering just littoral deltas as the unique possible type of delta in natural systems. Nevertheless, a rational analysis suggests that deltas can be much more complex. In fact, the characteristics of deltaic deposits will depend on a complex interplay between the bulk density of the incoming flow and the salinity of the receiving water body. This paper explores the natural conditions of deltaic sedimentation according to different density contrasts. The rational analysis of deltaic systems allows to recognize three main fields for deltaic sedimentation, corresponding to(1) hypopycnal(2) homopycnal and(3) hyperpycnal delta settings. The hypopycnal delta field represents the situation when the bulk density of the incoming flow is lower than the density of the water in the basin. According to the salinity of the receiving water body, three different types of hypopycnal littoral deltas are recognized: hypersaline littoral deltas(HSLD), marine littoral deltas(MLD), and brackish littoral deltas(BLD). The basin salinity will determine the capacity of the delta for producing effective buoyant plumes, and consequently the characteristics and extension of prodelta deposits.Homopycnal littoral deltas(HOLD) form when the density of the incoming flow is roughly similar to the density of the water in the receiving basin. This situation is typical of clean bedload-dominated rivers entering freshwater lakes. Delta front deposits are dominated by sediment avalanches. Typical fallout prodelta deposits are absent or poorly developed since no buoyant plumes are generated. Hyperpycnal deltas form when the bulk density of the incoming flow is higher than the density of the water in the receiving basin. The interaction between flow type,flow

关 键 词：DELTAS Hyperpycnal flows Homopycnal flows Hypopycnal flows Hyperpycnites TURBIDITES Sediment gravity flows Gravity flows 

分 类 号：P343.5[天文地球—水文科学] P512.2[天文地球—地球物理学]