Geochemical delineation of the Cretaceous/Tertiary boundary in some New Zealand rock sequences

Abstract

Calcium carbonate and other constituents of Upper Cretaceous and lower Tertiary rocks were determined at three localities in New Zealand where the Cretaceous/Tertiary boundary was believed to occur. The boundaries could be delineated by chemical means alone, thus reducing the time expenditure needed for the more usual paleontological techniques. This method might also be useful in locating the boundary where paleontological evidence is missing or inconclusive. Diagnostic elements were: arsenic, calcium, chromium, cobalt, iron, magnesium, manganese, nickel, phosphorus, and sulphur. In lacustrine sediments near Rewanui, a possible location of the K/T boundary was indicated by anomalous levels of calcium, iron; magnesium, and manganese. The principles enumerated should be of general application elsewhere in the world where searches continue for K/T boundary material.

Keywords:

• Cretaceous/Tertiary boundary
• Te Uri
• Waipara
• Woodside Creek
• calcium carbonate
• arsenic
• nickel
• chromium
• cobalt
• iron
• manganese
• phosphorus
• sulphur