The palaeobotany and stratigraphic sequence of the pleistocene Klondike "muck deposits".

The Klondike District of Central Yukon Territory around Dawson City is particularly advantageous for the study of the sequence of the Pleistocene epoch because it was never glaciated and therefore has never lost its fossiliferous superficial deposits. This paper presents a pollen diagram from a Sphagnum peat bed, which was the youngest deposit discovered, and pollen floras from different ages back to the Pliocene. The peat bed flora shows fairly steady climatic conditions little different from the present; the Pliocene flora shows a distinctly warmer climate; and all the others appear to show colder climates. The paper also presents a theory of correlation of geological events in the district with world-wide climatic variations: cutting of very broad creek valleys; climate warm - Earlier Tertiary - deposition of the oldest gravels; climate warm - Pliocene - deposition of oldest unweathered gravels; climate cold - Nebraskan Glaciation - rapid cutting of narrow lower creek valleys - Three Major Interglacial Ages - major interruptions of valley cutting; climate cold - Kansan and Illinoian Glaciation - deposition of thick valley - bottom muck; climate cold - Wisconsin Glaciation - erosion of valley - bottom muck; climate warmer than the present - Post-Glacial Climatic Optimum - deposition of Sphagnum peat bed; climate same as today - Recent Time [...