Skip to Main Content
GEOREF RECORD

Foraminiferal paleobathymetry and mid-cycle architecture of mid-Pleistocene depositional sequences, Wanganui Basin, New Zealand

Stephen T. Abbott
Foraminiferal paleobathymetry and mid-cycle architecture of mid-Pleistocene depositional sequences, Wanganui Basin, New Zealand
Palaios (June 1997) 12 (3): 267-281

Abstract

Mid-Pleistocene strata in the Castlecliff section of New Zealand show a cyclic alternation of shoreline to shelf lithofacies. A typical cycle is bounded by erosional disconformities, and shows a threefold subdivision. The lower unit is characterized by a basal cross-bedded shell-rich gravel, which is overlain by shoreline-nearshore siltstones, and/or sandstones. The middle unit is disconformity bounded, and is characterized by condensed shellbed facies deposited in terrigenous, sediment starved, inner-shelf settings. The upper unit comprises relatively thick and monotonous successions of shelf siltstone. Castlecliff cycles are interpreted as depositional sequences, driven by glacio-eustatic sea-level fluctuation. The component facies successions represent transgressive systems tracts (TST), mid-cycle condensed shellbeds (MCS), and highstand systems tracts (HST), respectively. Six Castlecliffian foraminiferal associations have been defined, and their paleodepth significance determined by uniformitarian comparison with modern New Zealand faunas. The shallowest (shoreface-innermost shelf) faunas are confined to TST successions, while the deepest faunas (outer inner-shelf) are confined to HST successions. The stratigraphic position of maximum paleodepth, and therefore the position of the conceptual maximum flooding surface (MFS), varies. Sequences in which the maximum paleodepth occurs within the mid-cycle condensed shellbed closely correspond to ideal sequence models, in which conditions of maximum sediment starvation coincide with maximum paleodepth. Sequences showing maximum paleodepths in HST shelf siltstones indicate that the MFS may not necessarily be coincident with mid-cycle condensed facies or their associated disconformities. Sequences with maximum foraminiferal paleodepths spanning some or all of MCS-JST successions indicate that the MFS may be represented as an interval rather than a specific disconformity or stratal surface. These results suggest that the MFS concept, as a means to separate TST from HST strata, may be of little use in shoreline inner-shelf paleogeographic settings.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 12
Serial Issue: 3
Title: Foraminiferal paleobathymetry and mid-cycle architecture of mid-Pleistocene depositional sequences, Wanganui Basin, New Zealand
Author(s): Abbott, Stephen T.
Affiliation: James Cook University of North Queensland, Department of Earth Sciences, Townsville, Queensl., Australia
Pages: 267-281
Published: 199706
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 35
Accession Number: 1997-061630
Categories: Quaternary geologyInvertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., strat. cols., 3 tables, sketch maps
S41°37'00" - S39°00'00", E174°28'60" - E176°31'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by Institute of Geological and Nuclear Sciences Limited (GNS Science), Lower Hutt, New Zealand
Update Code: 199720
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal