Studies on Connecticut lake sediments; Part 1, A postglacial climatic chronolgy for southern New England

Abstract

Eight profiles from 5 lakes and bogs in southern Connecticut were analyzed for fossil pollen. The resulting vegetational sequence is employed as a climatic chronology, and attempts are made to correlate the succession of events with other pollen chronologies in eastern North. America. Because of the chronologic uncertainties created by the irregular de-glaciation of Connecticut, the sequence can not be directly related to varved-clay chronologies, and it is suggested that all North American pollen profiles are probably incomplete, since they have been secured from kettles in which initial deposition did not coincide with the inception of deglacia-tion. The vegetational succession is divided into 6 periods Period A-l, spruce-fir (cool); period A-2, spruce-maximum (last oscillation of ice-border in New Haven region, cooler); period B-1, pine (warmer, dry); period C-1, oak-hemlock (warm, moist); period C-2, oak-hickory (warm, dry); period C-3 (at stations near the coast) oak-chestnut (warm, moist). During period C-3 a dichotomy is evident, in that the northernmost profile (near Middletown, ca. 30 miles inland) is characterized by spruce-hemlock (cool, moist). The evidence that local oscillations of the ice-border may be accompanied by climatic deterioration (period A-2) consists in part in a demonstration of comparable relations in Indiana, Wisconsin, and Illinois. Particularly close resemblances to the Connecticut sequence are found in eastern Canada (Auer) and Ohio (Sears). The hickory-maximum (C-2) during the mixed-deciduous forest period is tentatively correlated with the world-wide climatic op- timum. Subsequent changes of climate differed with latitude and continentality, so that moister conditions supervened at southern stations coastal Connecticut, Ohio, Illinois, etc., while cooling has taken place at more northern stations (eastern Canada, inland Connecticut, Wisconsin, Minnesota, etc.). In a deductive analysis of the relation between correlation and contemporaneity the climatic optimum is attributed to extraterrestrial causes, and regarded as contemporaneous in the absolute sense in all parts of the world. In this respect it is believed to differ from the earlier segment of the climatic chronology, in which events are determined by the proximity of a retreating glacier-terminus, and which is consequently considered as relative. The chronology established for southern Connecticut will be employed in later articles of the series, in which certain limnological questions, in particular biochemical and biological evidence for typological succession in lakes. will be treated by the author and others. Consequently preliminary results of structure-analysis of sediments are presented, and the terminology of organic lake deposits is briefly discussed. "Ooze" is proposed as a translation of the Swedish term gyttja," and "lake peat" for the Swedish "dy.".