Showing papers on "Varve published in 1973"

Varve Cycles in the Weeli Wolli Formation of the Precambrian Hamersley Group, Western Australia

Abstract: Chert and chert-matrix bands, internal striping, comparison with Dales Gorge Member of Brockman Iron Formation

Possible Syneresis Origin of Valleys on the Floor of Lake Superior

Abstract: RELIEF features occur on the floor of Lake Superior in distinct zones which are related to bottom type and water depth1 (Fig. 1). Zone A occurs in sand and gravel deposits to about 54 m depth. Deeper, the generalized sequence of sediments is bedrock, glacial till and sand deposits, red clay, red varved clay, and brown clay2–4. In zone B, a network of intersecting linear grooves of width 5 to 75 m having relief of 2 to 5 m and lengths of greater than 2 km occur in a till and red clay bottom at about 54 to 165 m depth. The grooves were probably formed by scouring by icebergs during an earlier lake stage when the continental ice sheet formed a border of the lake. In zone C, below about 165 m, the bottom consists of lacustrine clays, and a series of narrow, V-shaped valleys occur extensively on echograms1. In this study, the valleys were examined by side-scan sonar, high resolution sub-bottom profiling, echosounding, and bottom sampling (Fig. 1).

A special mechanism for varve formation in a glacial lake

Abstract: One of the major stratigraphic units in Lake Superior is a sequence of gray varved clays formed in late-glacial time. The sediment was carried into the lake by meltwater streams flowing from the region of gray calcareous tills in the northern part of the basin. During the summer when the sedimentation rate was high, the carbonates were rapidly buried and a highly calcareous layer preserved. During the winter the sedimentation rate was greatly reduced, the carbonates were partially dissolved by the cold lake water and a low-carbonate winter layer formed.

Organic Carbon in Sediments of Lake George, New York: Relation to Morphology of Lake Bottom, Grain Size of Sediments, and Man's Activities

Abstract: Lake George is in a rugged, densely wooded area in the eastern Adirondack Mountains of New York. Relict glacial sediment and modern sediment rich in organic matter floor the lake. The relict sediment includes Pleistocene varved lake clay containing iron-manganese nodules. Beneath a cover of modern organic-rich silty clay much of the lake is underlain by varved clay. A comparison of lake bottom morphology with both clay and organic matter content and sediment color shows that an interrelation exists between these variables. Sediment in the deeper parts of the lake is black, and clay and organic matter contents are generally high. In the shallower part of the lake sediment is brown in color, usually sandy, and low in organic matter. Tree bark, spore capsules, leaves, and needles compose much of the identifiable organic matter in the sandy near-shore bottom sediments. The organic material which enters the lake primarily in the fall is derived from vegetation in the drainage basin. The fabric of organic matter in the deeper parts of the lake cannot be identified because of advanced decomposition. The organic matter content of the bottom sediments of the southern basin of Lake George generally exceeds that of the northern basin, because pollution from permanent settlements along the shores of the southern basin accelerates accumulation of organic matter by enhancing phytoplankton productivity in the southern basin.