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~i <br />zo <br />and western Great Basin where geologic records are more complete (Benedict <br />1973, Curry 1968, Porter 1971, Richmond 1972, h'right $ Frey 1965) it <br />is possible to propose a crude paleoclimatic sequence for the eastern plains <br />of hbntana and Wyoming for the Holocene. Retreat of the continental ice <br />margins from Montana was complete by 13,000 to 14,000 years ago but ice per- <br />sisted and advanced at times in the mountains feeding the rivers of the <br />great plains until about 9,000 years ago in the south and 6,000 to 8,000 <br />years ago in the north. Following this, a period of surmner temperatures as <br />high or higher than today occurred culminating about 6,000 years ago. Then <br />climatic deterioration ensued with periods of cooler temperatures and/or <br />increased winter precipitation occurring episodically through today but with <br />today's "climatic normals" reflecting the warmer and drier phase of conditions <br />that would have occurred during the last 4,000 years. lacking in this grossly <br />simplified summary is an understanding of variations in siumner precipitation. <br />Since temperatures are doubtless adequate for soil formation today for at <br />least several months, available soil moisture becomes the limiting factor for <br />acid high plains soil formation. If past climates were characterized by consider- <br />ably increased stmmuer precipitation and/or longer growing seasons, one would <br />expect discernable differences in rates of soil formation. One would also <br />expect differences in vegetation under those different climates. Some evidence <br />of past stormier precipitation variation in the form of relicts of juniper logs <br />far from reproducing junipers in the northern Green River Basin of Wyoming do <br />suggest wetter summers correlating with times of neoglacial advances in the <br />