80 ALASKAN MINERAL RESOURCES IN 1905. 
The igneous rocks consist mainly of (1) granitic masses intruded into the surrounding 
sediments, (2) aplitic dikes, (3) basic dikes, and (4) basic lava flows. These latter have 
been altered, sometimes rendered schistose, and are referred to as greenstones. They are 
the most abundant and the most characteristic igneous rocks of the region. Many of the 
flows consist in considerable part of irregular ellipsoidal masses 1 to 10 feet in diameter, 
closely resembling the ellipsoidal greenstones of the Lake Superior region. 
The sedimentary rocks and the lava flows have been completely, complexly, and usually 
closely folded, and a cleavage has been developed, especially in the finer sediments. The 
folding has been so close thai in most parts of the district the cleavage practically agrees 
with the bedding. The dips and strikes vary considerably. The former average above 45°, 
and frequenf ly are 60° to (H)°. About Port Valdez the direction of dip is consistently toward 
the north, the folds being overturned toward the south. Locally the strike is rather constant, 
mid often inns parallel with the physiographic features, as along the eastern stretch of Port 
Valdez, where the strike agrees with the axis of the bay, and also on Latouche Island, where 
the strike is parallel with the length of the island. 
The sedimentary rocks of Prince William Sound are separable into at least two uncon- 
formable series of nearly similar lithological characters. The older of these series, named by 
Schrader, the Yaldez,« is typically developed about the eastern part of Port Valdez. Its 
rocks are on the average a Little more metamorphosed, more schistose, and more closely 
folded than the rocks of the younger Orca series. a Interbedded lava flows are nearly or 
quite absent, though the presence of some greenish schists — probably altered fine-grained 
tuffs would indicate that volcanic activity was not entirely absent during the deposition of 
the Valdez rocks. The Orca series covers much more territory than the Valdez, and is the' 
chief formation of the district. It differs from the Valdez series in the points already men- 
tioned and also in the presence of ( 1 ) much black slate, (2) conglomerates, and (3) many inter- 
bedded lava flows. The black slate is usually soft and much jointed, is frequently fissile, 
and in places contains infolded fragments of the gravwackes. This slate is well developed 
in the vicinity of Ellamar. The conglomerates are found at a number of points, and are 
composed of well-rounded pebbles set in a graywackc or a slate matrix. The lava flows are 
of a basic nature, were originally mainly diabases and basalts, and have been altered so that 
they are now greenish in color and are here referred to as greenstones. Many of these flows 
are ellipsoidal in character, and they are especially common near the base of the Orca series. 
Associated with the flows are some dikes and probably also some sills, but the intrusive or 
extrusive nature of some of the greenstones is not always clear in the most folded areas. 
Characteristic exposures of these greenstones occur on the north side of the entrance to 
Galena Bay and also on Glacier Island. 
In the Orca series a few poorly preserved plant remains have been found, and also some 
worm tubes, which resemble forms called Terebellina palachei Ulrichb from Kodiak Island. 
The Orca series is probably of Mesozoic age. The age of the Valdez series is undetermined. 
MINERAL RESOURCES. 
COPPER DEPOSITS. 
The chief ore of the district is chalcopyrite (a sulphide of copper and iron). This is very 
generally associated with pyrrhotite (magnetic iron pyrites) and, to a less extent, with pyrite 
(yellow sulphide of iron) and marcasite (white iron pyrites); these iron sulphides probably 
carry small amounts of copper. Chalcocite was noted in one place, near Orca. Secondary 
carbonate of copper occurs as a green surface stain; this is usually malachite and rarely 
azurite. The alteration of the original copper sulphides to form these carbonates is a super- 
ficial phenomenon, and they occur at or very near the surface or along cracks within a few 
a Schrader, F. C, A reconnaissance of a part of Prince William Sound and the Copper River district , 
Alaska, in 1898: Twentieth Ann. Kept. U. S. Geol. Survey, pt. 7, 1900, pp. 404-409. See also footnote, 
p. 62 of this bulletin. 
b ("lrich, E. O., Fossils and age of the Yakutat formation: Harriman Alaska Expedition, vol. 1. New- 
York, 1904, pp. 125-144. 
