Preliminary report on the geology and ground-water resources of the Matanuska Valley agricultural area, Alaska

Abstract

This report describes the geology and ground-water resources of an area of present and potential agricultural development iii south-central Alaska. The agricultural area lies on a wide valley floor, most of which is formed by glacial deposits. Nonglacial unconsolidated deposits include windblown material distributed generally over the agricultural area and slope deposits along the valley walls. Small bodies of perennially frozen ground (permafrost) are present in some bogs. Till ("hardpan"), possibly of late "Wisconsin (Mankato) age, occurs at the" surface or beneath surficial outwash gravel deposits in a large part of the valley floor. In several widely separated localities th.e till is known to be underlain by older glacial gravel, and the presence of an older till beneath this gravel is suspected. Several types of outwash deposits, most of them formed during glacial recession in this area, are differentiated on the geologic map which accompanies the report. Associated with glaclofluvial deposits of existing streams are estuarine deposits of glacial silt. The topography developed on the unconsolidated deposits is due chiefly to glacial deposition, large-scale stagnation of ice, and trenching of glacial deposits by outwash streams.Most wells in the agricultural area obtain water from gravel. Supplies sufficient for domestic and farm use are generally available wherever the gravel is saturated. Only a little is known of the quantities of water available. Till in this area is relatively imp^rHie_abl_ej_mosjL> wells in till obtain water from included thirtor gravel layers. Bedrock here appears to be^a relatively poor water-bearing material.The area is divided into six physiographic units to facilitate description of the occurrence of ground water.Recharge of ground water is chiefly from precipitation, but parts of the area receive drainage from adjacent mountain slopes. Fluctuations of the water table as much as several feet were observed during the period 1949-51.Chemical analyses show that the ground water ranges from moderately hard to very hard but is suitable for general domestic and farm uses.A table giving records of 333 wells is included in this report. The locations of the wells are shown on the geologic map.

Quaternary geology of the Kenai Lowland and glacial history of the Cook Inlet region, Alaska

“…In this regard the present work has been greatly facilitated by informa tion, both published and unpublished, in previous re ports about the Cook Inlet region. Particularly help ful have been reports by Capps (1931;1935), Martin, Grant, and Johnson (1915), and more recent work by Trainer (1953Trainer ( , 1955 on the ground-water geology of the lower Matanuska Valley; by Dobrovolny and Mil ler (1950) and Miller and Dobrovolny (1959) on the engineering geology of the Anchorage area; by BjOrn Andersen (written communication, 1955) on the Pleistocene geology of the southwestern part of the Talkeetna Mountains ; by Gordon Gastil (written com munication, 1955) on the Pleistocene geology of the lower Matanuska Valley ; and by Cobb (1951) on the Tertiary bedrock of the southwestern part of the Kenai Lowland. The author was fortunate in being able to to confer and discuss mutual field problems with BjOrn Andersen, Gordon Gastil, Robert Miller, and Ernest Dobrovolny during the course of their own field map ping in the upper Cook Inlet region.…”

Eolian deposits of the Matanuska Valley agricultural area, Alaska

“…These deposits of silt and sand have been discussed by Tuck (1938), Eockie (1946), Black (1951), Trainer (1953), , Stump, Handy, Davidson, Roy, and Thomas (1956), and . Tuck gives a concise statement of their eolian origin.…”

Ground-water resources of the Palmer area, Alaska

“…25-26 T. 18 N., R. 1 E., on the east by the Matanuska River and Clark-Wolverine Road, and on the west by Trunk Road. Trainer (1953Trainer ( , 1960 provided early discussions of the geology and ground-water resources of the agricultural area in the Matanuska Valley, including the Palmer area. His work provided much of the historical data referenced here.…”