The composition of Permian seawater

Juske Horita, Thomas J. Friedman, Boaz Lazar, Heinrich D. Holland

Research output: Contribution to journalArticlepeer-review

87 Scopus citations

Abstract

Forty-nine brine inclusions in marine halite from the Ochoan Salado Formation in the Delaware Basin and fifteen inclusions in halite from the Leonardian Wellington Formation in the Kansas Basin were extracted, and their chemical compositions were determined. The brines are of the Na-K-Mg-Cl-SO4 type; their compositions resemble those of evaporated modern seawater. The values of (mCl- - mNa+) mBr- and (mMg2+ + mCa2+ - mSO42- - 1 2 mmHCO3-) mBr- of the inclusion brine from the two formations are equal to or slightly higher than those of modern seawater. The original mNa+ mBr- and mCl- Mbr- ratios of the inclusion brines were probably equal to or slightly larger than those of modern seawater. The values of mMg2+ mBr- of the inclusion brines from the Salado Formation are very close to that of modern seawater; the ratios of inclusion brines from the Wellington Formation are slightly lower, probably due to the formation of dolomite/magnesite. The mMg2+ mBr- ratio in the initial seawater was probably close to the parent seawater of the Salado brines. The values of (mSO42- - mCa2++ 1 2mHCO3-) mBr- of the inclusion brines appear to be reduced by the formation of dolomite/magnesite, and the value of this ratio in Permian seawater was probably similar to that of modern seawater. The mK+ Mbr- ratios of the inclusion brines are variable, but the original ratios are probably close to or slightly larger than that of modern seawater. If the Br- concentration of Permian seawater was equal to that of modern seawater, the composition of Permian seawater can be narrowly constrained; in mmol/kg H2O, 460 ≤ mNa + < 630, 550 ≤ mCl- < 730, mMg2+ = 54 ± 6, mK+ ∼- 11, ( mSO2-4 - mCa2+ + 1 2mmHCO3-) ≥ 17, 20 < mSO42- < 45, 5 < mCa2+ < 20, and 0.15 < mHco3- < 5. The composition of Permian seawater was therefore quite similar to that of modern seawater.

Original languageEnglish
Pages (from-to)417-432
Number of pages16
JournalGeochimica et Cosmochimica Acta
Volume55
Issue number2
DOIs
StatePublished - Feb 1991

Fingerprint Dive into the research topics of 'The composition of Permian seawater'. Together they form a unique fingerprint.

Cite this