from Interior Alaska
ABSTRACT. Polished and rounded grains of quartz, secondary quartz and chert have been found in loess and peat in interior Alaska. The intermediate diameter of these polished and rounded grains is between 35 and 0.07 mm., with grains of 0.7 mm., 2 to 4 mm. and perhaps 10 to 20 mm. being most abundant...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.575.8693 http://pubs.aina.ucalgary.ca/arctic/Arctic23-1-14.pdf |
| Summary: | ABSTRACT. Polished and rounded grains of quartz, secondary quartz and chert have been found in loess and peat in interior Alaska. The intermediate diameter of these polished and rounded grains is between 35 and 0.07 mm., with grains of 0.7 mm., 2 to 4 mm. and perhaps 10 to 20 mm. being most abundant. Polish on these grains has been produced by abrasion in bird gizzards. Gizzard-bearing birds are living in interior Alaska today and produce glossy polish on their gastroliths comparable to the polish on gastroliths from the Holocene and Pleistocene deposits. The polish and roundness of Recent bird gastroliths vary, being more pronounced in those of living birds in late winter. Some of the Holocene and Pleistocene polished gastroliths are believed to have been produced by species of birds not now living in interior Alaska, because modal size classes of these ancient gastroliths do not coincide with modal size classes of polished gastroliths from birds living there today. R&SUMB: Gastrolithes d'oiseaux pléistoc&nes, holoc8nes et récents de l'Alaska inté-rieur. On trouve dans le loess et la tourbe de l'Alaska intérieur des grains polis et arrondis de quartz, de quartz secondaire et de chert. Le diamètre intermédiaire de ces grains se situe entre 35 et 0.07 mm, les plus abondants mesurant 0.07 mm, de 2 21 4 mm et peut4tre, de 10 B 20 mm. Le poli de ces grains est le produit de l'abrasion dans des ghiers d'oiseaux. Les oiseaux il gésier qui vivent aujourd'hui dans l'Alaska intérieur produisent sur leurs gastrolithes un fini poli comparable B celui des gastrolithes des dépbts holocènes et pléistoches. Sur les gastrolithes d'oiseaux récents, le poli et l'arrondi varient directement, atteignant un maximum pour les oiseaux vivants B la iïn de l'hiver. On peut croire que certaines gastrolithes polies de l'Holodne et du Pléistocène ont été produites par des oiseaux qui ne vivent plus aujourd'hui dans l'Alaska intérieur, car les classes dimensionnelles de ces gastrolithes anciennes ne coïncident plus avec celles des ... |
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