Sedimentology and micromorphology of drumlin sediments at Chimney Bluffs State Park, New York, United States of America

The drumlin sediments at Chimney Bluffs, New York appear to represent a block-inmatrix style glacial melange. This melange comprises sand stringers, lenses and intraclasts juxtaposed in an apparently massive diamicton. Thin section examination of these glacigenic deposits has revealed microstructures indicative of autokinetic subglacial defonnation which are consistent with a deformable bed origin for the diamicton. These features include banding and. necking of matrix grains, oriented plasma fabrics and the formation of pressure shadows at the long axis ends of elongate clasts. Preservation of primary stratification within the sand intraclasts appears to suggest that these features were pre-existing up-ice deposits that were frozen, entrained, then deposited as part of a defonning till layer beneath an advancing ice sheet. Multi-directional micro-shearing within the sand blocks is thought to reflect the frozen nature of the sand units in such a high strain environment. It is also contended that dewatering of the sediment pile leading to the eventual immobilisation of the defonning till layer was responsible for opening sub-horizontal fissures within the diamicton. These features were subsequently infilled with mass flow poorly sorted sands and silts which were subjected to ductile defonnation during the waning stages of an actively deforming till layer. Microstructures indicative of the dewatering processes in the sand units include patches of fine-grained particles within a coarser-grained matrix and the presence of concentrated zones of translocated clays. However, these units were probably confined within an impermeable diamicton casing that prevented massive pore water influxes from the deforming till layer~ Hence, these microstructures probably reflect localised dewatering of the sand intraclasts. A layered subglacial shear zone model is proposed for the various features exhibited by the drumlin sediments. The complexity of these structures is explained in terms of ii superposing deformation styles in response to changing pore water pressures. Constructional glaciotectonics, as implied by the occurrence of sub-horizontal fissuring, is suggested as the mechanism for the stacking of the sand intraclast units within the diamicton. The usefulness of micromorphology in complimenting the traditional sedimentology of glacigenic deposits is emphasised by the current study. An otherwise massive diamicton was shown to contain microstructures indicative of the very high strain rates expected in a complexly deforming till layer. . It is quite obvious from this investigation that the classification of diamictons needs to be re-examined for evidence of microstructures that could lead to the re-interpretation of diamicton forming processes. RESUME Le pacquet de sediments drumlinaire de Chimney Bluffs, New York, represent un "bloc-en-matrice" genre de melange glaciale. Des structures microscopique comprennent l'evidence pour la defonnation intrinseque attribuee a l'origine lit non resistant du drumlin. PreselVation des structures primaires au coeur des blocs arenaces suggere que ceux sont des depots preexistant qui furent geles, entraines et par la suite sedimentes au milieu d'une couche de debris sous-glaciaires en voie de deformation. Des failles microscopiques a l'interieur des blocs arenaces appuient aussi l'idee d'un bloc cohesif (c'est-a-dire gele) au centre d'un till non resistant. Des implications significatives s'emergent de cette etude pour les conditions sous-glaciaire et les processus de la formation des drumlin.

Colum C. Chapman, Chicago, Illinois

Cabinet card photographic portrait of Colum C. Chapman in his National Guard uniform, Chicago, Illinois, ca. 1890.

Charles C. Chapman and Ethel Chapman Wickett at a birthday picnic for Charles C. Chapman at Orange County Park, California, July 2, 1937

Charles C. Chapman and Ethel Chapman Wickett at a birthday picnic for Charles C. Chapman at Orange County Park, California, July 2, 1937. [Copy an excerpt of CCCF27]

Charles C. Chapman, Ethel Chapman Wickett and Stanley Chapman at Orange County Park, 1937

Charles C. Chapman, Ethel Chapman Wickett and Stanley Chapman at birthday picnic for Charles C. Chapman at Orange County Park, California, July 2, 1937.

Frank M. Chapman, Jr. son of Frank M. and Wilhelmina Chapman, Chicago, Illinois, ca. 1891.

Studio portrait of Frank M. Chapman, Jr. son of Frank M. and Wilhelmina Chapman, Chicago, Illinois, ca. 1891.

Frank C. Chapman, Chicago, Illinois, ca. 1890

Studio portrait of Frank C. Chapman, Chicago, Illinois, ca. 1890.

Label, "Clarke & Chapman, Packers and Jobbers of Green Apples, Macomb, Illinois

Label on card stock for "Clarke & Chapman, Packers and Jobbers of Green Apples, Macomb, Illinois, 1870-1878"

Wilhelmina Zillen Chapman, Chicago, Illinois, 1892

Cabinet card portrait of Wilhelmina Zillen Chapman, mother of Grant Chapman and grandmother of Joyce Chapman, taken by G. D. Morse, Chicago, Illinois, July, 1892.

Charles C. and Lizzie Chapman with daughter Ethel, Chicago, Illinois

Charles C. Chapman and his wife, Lizzie Pearson Chapman, with baby daughter Ethel in a hammock, Chicago, Illinois, ca. 1885.

Mrs. Heppenstall, a member of the Chapman family, Abington, Illinois

Cabinet card photographic portrait of Nancy Wallace Pearson Heppenstall [1834-1916], taken in the studio of William Johnston, Abington, Illinois. She was the mother of Lizzie Pearson Chapman, wife of Charles Clarke Chapman.

E. Joe Clarke, Monmouth, Illinois

Cabinet card photographic portrait of E. Joe Clarke, taken in the Root studio, Monmouth, Illinois.

Unidentified member of the Chapman family, Hattoon, Illinois

Unidentified studio portrait of a member of the Chapman family, taken in the Teitzell Studio, Hattoon, Illinois.

Residence, Sterling, Illinois

Residence [written over photograph: "Home 1916-1919"], possibly Sterling, Illinois, ca. 1919.