Geochemical correlation in deltaic successions: a reality check

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Whole-rock geochemical analysis can aid the stratigraphic correlation of faunally barren successions. Compared to petrographic techniques or heavy-mineral separations, such analysis is quick and objective, yet rarely has the reliability of the method been tested against unequivocal correlations. We have applied it to the Kenilworth Member of the Upper Cretaceous Blackhawk Formation, a well-exposed and easily correlated 100-m-thick unit in the deltaic successions of the Book Cliffs, Utah, United States. This is the first evaluation of geochemical analysis as an aid to sequence stratigraphic interpretation at the parasequence scale.

From the geochemistry alone, it is not possible with statistical confidence to separate individual parasequences or systems tracts nor the fluvial incised valley from the marine shoreface units. The magnitude of geochemical variation in a single sandstone bed over a 30 m lateral traverse is as great as vertically through an entire parasequence. Y, Nb, Rb, and Ti abundances are inversely correlated with grain size. Thus geochemical signatures follow sedimentological trends, and distal parts of a parasequence appear distinct from proximal parts. Y ratios compensate for this grain size effect but introduce confusing distortions for elements such as Zr that are not correlated with grain size. Contrary to some predictions, Zr is as common in the finest-grained units as the coarsest, and Sr is not correlated with Ca. In some sections Sr is also inversely correlated to grain size and cannot be used as an indicator for cement abundance.

Original languageEnglish
Pages (from-to)620-632
Number of pages12
JournalGeological Society of America Bulletin
Volume117
Issue number5/6
DOIs
Publication statusPublished - May 2005

Keywords

  • correlation
  • geochemistry
  • deltas
  • sequence stratigraphy
  • Cretaceous
  • Book Cliffs
  • rare-earth elements
  • book-cliffs
  • Kenilworth member
  • Western interior
  • Utah-Colorado
  • sandstones
  • field
  • rock
  • diagenesis

Cite this

Geochemical correlation in deltaic successions : a reality check. / North, Colin Peter; Hole, Malcolm John; Jones, D. G.

In: Geological Society of America Bulletin, Vol. 117, No. 5/6, 05.2005, p. 620-632.

Research output: Contribution to journalArticle

@article{b6593f5a0e4e472898038c69b0a17e92,
title = "Geochemical correlation in deltaic successions: a reality check",
abstract = "Whole-rock geochemical analysis can aid the stratigraphic correlation of faunally barren successions. Compared to petrographic techniques or heavy-mineral separations, such analysis is quick and objective, yet rarely has the reliability of the method been tested against unequivocal correlations. We have applied it to the Kenilworth Member of the Upper Cretaceous Blackhawk Formation, a well-exposed and easily correlated 100-m-thick unit in the deltaic successions of the Book Cliffs, Utah, United States. This is the first evaluation of geochemical analysis as an aid to sequence stratigraphic interpretation at the parasequence scale.From the geochemistry alone, it is not possible with statistical confidence to separate individual parasequences or systems tracts nor the fluvial incised valley from the marine shoreface units. The magnitude of geochemical variation in a single sandstone bed over a 30 m lateral traverse is as great as vertically through an entire parasequence. Y, Nb, Rb, and Ti abundances are inversely correlated with grain size. Thus geochemical signatures follow sedimentological trends, and distal parts of a parasequence appear distinct from proximal parts. Y ratios compensate for this grain size effect but introduce confusing distortions for elements such as Zr that are not correlated with grain size. Contrary to some predictions, Zr is as common in the finest-grained units as the coarsest, and Sr is not correlated with Ca. In some sections Sr is also inversely correlated to grain size and cannot be used as an indicator for cement abundance.",
keywords = "correlation, geochemistry, deltas, sequence stratigraphy, Cretaceous, Book Cliffs, rare-earth elements, book-cliffs, Kenilworth member, Western interior, Utah-Colorado, sandstones, field, rock, diagenesis",
author = "North, {Colin Peter} and Hole, {Malcolm John} and Jones, {D. G.}",
year = "2005",
month = "5",
doi = "10.1130/B25436.1",
language = "English",
volume = "117",
pages = "620--632",
journal = "Geological Society of America Bulletin",
issn = "0016-7606",
publisher = "Geological Society of America",
number = "5/6",

}

TY - JOUR

T1 - Geochemical correlation in deltaic successions

T2 - a reality check

AU - North, Colin Peter

AU - Hole, Malcolm John

AU - Jones, D. G.

PY - 2005/5

Y1 - 2005/5

N2 - Whole-rock geochemical analysis can aid the stratigraphic correlation of faunally barren successions. Compared to petrographic techniques or heavy-mineral separations, such analysis is quick and objective, yet rarely has the reliability of the method been tested against unequivocal correlations. We have applied it to the Kenilworth Member of the Upper Cretaceous Blackhawk Formation, a well-exposed and easily correlated 100-m-thick unit in the deltaic successions of the Book Cliffs, Utah, United States. This is the first evaluation of geochemical analysis as an aid to sequence stratigraphic interpretation at the parasequence scale.From the geochemistry alone, it is not possible with statistical confidence to separate individual parasequences or systems tracts nor the fluvial incised valley from the marine shoreface units. The magnitude of geochemical variation in a single sandstone bed over a 30 m lateral traverse is as great as vertically through an entire parasequence. Y, Nb, Rb, and Ti abundances are inversely correlated with grain size. Thus geochemical signatures follow sedimentological trends, and distal parts of a parasequence appear distinct from proximal parts. Y ratios compensate for this grain size effect but introduce confusing distortions for elements such as Zr that are not correlated with grain size. Contrary to some predictions, Zr is as common in the finest-grained units as the coarsest, and Sr is not correlated with Ca. In some sections Sr is also inversely correlated to grain size and cannot be used as an indicator for cement abundance.

AB - Whole-rock geochemical analysis can aid the stratigraphic correlation of faunally barren successions. Compared to petrographic techniques or heavy-mineral separations, such analysis is quick and objective, yet rarely has the reliability of the method been tested against unequivocal correlations. We have applied it to the Kenilworth Member of the Upper Cretaceous Blackhawk Formation, a well-exposed and easily correlated 100-m-thick unit in the deltaic successions of the Book Cliffs, Utah, United States. This is the first evaluation of geochemical analysis as an aid to sequence stratigraphic interpretation at the parasequence scale.From the geochemistry alone, it is not possible with statistical confidence to separate individual parasequences or systems tracts nor the fluvial incised valley from the marine shoreface units. The magnitude of geochemical variation in a single sandstone bed over a 30 m lateral traverse is as great as vertically through an entire parasequence. Y, Nb, Rb, and Ti abundances are inversely correlated with grain size. Thus geochemical signatures follow sedimentological trends, and distal parts of a parasequence appear distinct from proximal parts. Y ratios compensate for this grain size effect but introduce confusing distortions for elements such as Zr that are not correlated with grain size. Contrary to some predictions, Zr is as common in the finest-grained units as the coarsest, and Sr is not correlated with Ca. In some sections Sr is also inversely correlated to grain size and cannot be used as an indicator for cement abundance.

KW - correlation

KW - geochemistry

KW - deltas

KW - sequence stratigraphy

KW - Cretaceous

KW - Book Cliffs

KW - rare-earth elements

KW - book-cliffs

KW - Kenilworth member

KW - Western interior

KW - Utah-Colorado

KW - sandstones

KW - field

KW - rock

KW - diagenesis

U2 - 10.1130/B25436.1

DO - 10.1130/B25436.1

M3 - Article

VL - 117

SP - 620

EP - 632

JO - Geological Society of America Bulletin

JF - Geological Society of America Bulletin

SN - 0016-7606

IS - 5/6

ER -