Published online by Cambridge University Press: 04 May 2010
Summary
A wide variety of sedimentary structures occur in modern jökulhlaup deposits and an important question arises when trying to identify jökulhlaup deposits in the sedimentary record: which sedimentary structures are distinctive of jökulhlaup deposition? A given sedimentary structure can be formed by more than one process, and in isolation cannot be used to distinguish a jökulhlaup deposit from those formed by other fluvial and flood processes. This chapter identifies those sedimentary structures that are thought to be unique or highly distinctive in jökulhlaups. Some structures are only formed by jökulhlaups in the proglacial environment, but can be found in other fluvial environments. Distinctive sedimentary features of jökulhlaup flows may include hyperconcentrated flow deposits, thick (greater than 5m) upwards coarsening units formed by accretion during the rising stage of a flood and large gravel cross-beds (indicating formation by large gravel dunes) and flood bar deposits. Additional, non-distinctive indicators of jökulhlaup deposition include reactivation surfaces in gravel bedforms, widespread erosion surfaces and consistent palaeoflow indicators. Ice-block and rip-up clast related sedimentary structures are also non-unique, given that they can be formed under non-flood conditions, but their size and numbers are many times greater when formed by a jökulhlaup. To illustrate the points made in the review, this chapter presents a case study using ground-penetrating radar data that describe the sediments of a flood bar deposited during the November 1996 jökulhlaup in Iceland.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.