United States Geological Survey YearbookThe Survey, 1987 - Forest reserves |
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Results 1-5 of 90
Page i
... Rocks Undifferentiated Cretaceous - Jurassic Sedimentary Rocks Cretaceous Augen Gneiss Permian - Devonian Sedimentary Rocks Cambrian Sedimentary Rocks Cambrian - Proterozoic Rocks Precambrian Undifferentiated Belt Supergroup ...
... Rocks Undifferentiated Cretaceous - Jurassic Sedimentary Rocks Cretaceous Augen Gneiss Permian - Devonian Sedimentary Rocks Cambrian Sedimentary Rocks Cambrian - Proterozoic Rocks Precambrian Undifferentiated Belt Supergroup ...
Page 2
... rocks EARLY PROTEROZOIC ( 2500-1600 m.y. ago ) Southern Province ARCHEAN ( before 2500 m.y. ago ) Superior Province ... rock bodies that have contrasting acoustic properties , and these " echoes " are recorded on a series of hydrophones ...
... rocks EARLY PROTEROZOIC ( 2500-1600 m.y. ago ) Southern Province ARCHEAN ( before 2500 m.y. ago ) Superior Province ... rock bodies that have contrasting acoustic properties , and these " echoes " are recorded on a series of hydrophones ...
Page 3
... rock layers in the sub- surface and transmit the signals to recording equipment onboard . B , The seismic- reflection surveying system in operation on Lake Superior . Air guns in four arrays marked by the orange floats are towed be ...
... rock layers in the sub- surface and transmit the signals to recording equipment onboard . B , The seismic- reflection surveying system in operation on Lake Superior . Air guns in four arrays marked by the orange floats are towed be ...
Page 4
... rocks in the subsurface , is colored so that areas of strong- est attraction are shown in warm colors and areas of pro- gressively lower attraction are shown by progressively cooler colors ( see explanation on fac- ing page ; in ...
... rocks in the subsurface , is colored so that areas of strong- est attraction are shown in warm colors and areas of pro- gressively lower attraction are shown by progressively cooler colors ( see explanation on fac- ing page ; in ...
Page 5
... rock units were detected to depths as great as 18 miles . Projection of these rock units onto land shows that they are volcanic flows of basalt alternating with layers of sedimentary rocks . Study of these units on land indi- cates they ...
... rock units were detected to depths as great as 18 miles . Projection of these rock units onto land shows that they are volcanic flows of basalt alternating with layers of sedimentary rocks . Study of these units on land indi- cates they ...
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