Abstract
During the Late Pleistocene and Holocene (125 ka B.P. to present) a Type 1, 4th-order, depositional sequence, comprising regressive, lowstand, transgressive and highstand system tracts, formed worldwide. The Holocene (10 ka B.P. to present) part of this contains the latest and present highstand systems tract (HST). Within this and the underlying transgressive systems tract (TST) of the Ebro delta, in northeastern Spain, higher-frequency, 5th- to 6th-order, sea-level fluctuations are recognised. These form retrogradational and progradational high-frequency depositional sequence sets within the TST and HST, respectively. Each high-frequency sequence comprises: (1) a basal, highly reflective, shell lag, associated with an erosional (transgressive) surface; (2) aggradational deposits which seawards consist of a wedge of marine clays with transparent seismic facies, but inland are represented by thick peats; (3) progradational deposits, composed of sandy delta-front facies, displaying slope clinoforms; these pass seawards into prodeltaic grey silts, and landwards, into red silts and pebbly sands of delta-plain facies. The progradational deposits downlap towards their bases. The aggradational deposits formed in response to a period of rising sea-level and a rapid increase in accommodation space. Progradation began when sediment supply to the delta exceeded accommodation space as a result of relative sea-level fall. The relative sea-level curve for the delta has a stepped character, caused by the punctuation of the 4th-order sea-level trend by higher-frequency eustatic fluctuations as well as by high subsidence rates, of about 1.75 mm per year. The TST comprises retrogradational parasequences that onlap the underlying Pleistocene gravels. The maximum flooding surface separating the TST from the HST, was formed about 6900 yrs B.P. on the basis of 14C dating of peats. The HST comprises progradational deltaic and aggradational units, stacked as progradational high-frequency parasequence sets. The HST of the Ebro delta is compared with other deltaic sequences around the world, in particular with that of the Mississippi delta. A tentative chronology of the high-frequency climatic and eustatic oscillations influencing deltaic sedimentation globally over the last 7000 years is presented.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
