Relict red-weathered regolith at Wellington

Abstract

Geological problems concerning red-weathered regolith developed on pre-Cretaceous greywacke and argillite bedrock, and on Pleistocene gravel and bouldery gravel cornposed almost entirely of greywacke and argillite pebbles, cobbles, and boulders, on certain clays, and on some periglacial, soliflual deposits are discussed. The red weathering is considered to have taken place in a seasonally humid climate with a hot, dry period, with a mean annual temperature above 60° F and an annual rainfall of more than 40 in. In the Wellington district, during the Pleistocene, there have been three or more periods of red weathering, the oldest of which has been deeply developed and is the most intense. The age of the red weathering is uncertain; the oldest phase is probably of interglacial age. In the absence of diagnostic fossils for age determination and because correlation with present schemes of Pleistocene glacial chronology in New Zealand is very doubtful, it is tentatively suggested that the oldest phase is perhaps Mindel-Riss or Riss-Würm.