ALGAL PILLARS—BROWN 
is wood—the upright, more or less de- 
cayed stems, trunks, stumps, and snags 
of trees or shrubs killed by drowning 
where they stood in an area recently 
flooded or ponded. The irregular 
contours with jagged lobes and odd 
angles of the boundary between the 
inner silica zone and the outer lime 
zone of many specimens indicate that 
most of the wood had already lost its 
bark and had undergone considerable 
decay and erosion before lime deposi- 
tion on it began. Such deterioration 
occurs when wood is submerged in 
shallow, circulating waters where bac- 
teria, fungi, and other destructive 
agents are free to act and are not in- 
hibited by antiseptic conditions like 
those prevailing in peat bogs and 
the stagnant bottoms of deep lakes. 
The tops of submerged stumps tend 
to become more or less ragged to 
blunt-pointed. Consequently the first 
layers of algal lime covering such tops 
appear somewhat disrupted or inco- 
herent. Eventually, however, the limy 
layers on the sides of the pillars became 
homogeneous with those covering the 
tops (pl. 2, fig. 3; pl. 3, fig. 2). The 
fact that the tops of the upright pillars 
are entire and continuous, without any 
evidence whatsoever of having had an 
orifice, is further proof that the pillars 
are not geyser cones. Furthermore, 
the laminae of the pillars viewed in 
lengthwise sections (pl. 3, fig. 2; pl. 8, 
fig. 2) are in effect cylinders within 
cylinders with rounded to conical 
caps, whereas the layers in true geyser 
pillars are parts of cones within cones 
like the cups in a stack of paper drink- 
ing cups (pl. 8, fig. 1). While these 
layers were being added one after 
another, worms and insect larvae, 
living in tubes or cases (pl. 2, fig. 3; 
pl. 3; pl. 7, fig. 2; pl. 8, fig. 3), infested 
the outside of the growing pillars, 
crawling over theni or attaching them- 
selves to the surface. After emergence 
of the adults, such as caddis flies or 
midges, the cases and tubes were 
abandoned, and these became new 
centers for algal deposits. Most of the 
empty cases and tubes filled with cal- 
281 
careous sand and ostracodes (pl. 8, 
fig. 3), or, if left empty, with calcite or 
chalcedony as a result of later min- 
eralization. 
As the tree stumps and snags, sub- 
merged in the ponds and lakes, were 
rooted in bottom mud and sand, no 
algal deposits could form over the 
buried portions. Therefore, the roots 
and those parts above the mud-line, 
now encased in algal lime, would con- 
tinue to decay until, in most instances, 
all the wood was destroyed. More- 
over, no algae could deposit lime in 
the water-filled spaces where the 
wood had been because algae, requir- 
ing sunlight, could not live in those 
dark chambers, Also, it seems that 
neither sand nor mud could seep into 
those cavities. 
Eventually the ponded condition of 
prehistoric Whisky Basin changed. 
The ponds and lakes disappeared by 
being filled with sediments, thus end- 
ing the algal phase of deposition, if it 
had not already ceased, and burying 
the algal pillars. Several hundreds of 
feet of Bridger strata, which in neigh- 
boring areas yield many fossil animal 
remains, finally covered the site of the 
algal deposits, approximately 40 mil- 
lion years ago. Then subterranean, 
circulating waters, percolating through 
the Bridger strata, which contain much 
volcanic ash, a rich source of silica, 
leached out some of the silica and per- 
meated the buried, porous, limy, algal 
pillars, filling all holes and crevices 
with the silicifying solutions. In time 
the pillars and any remaining wood 
became silicified, but in many in- 
stances the silicification was incom- 
plete, leaving hollow centers in the 
pillars studded with quartz or calcite 
crystals. I shall not pretend to explain 
the chemistry of this process. 
I have seen only a few specimens 
from Whisky Basin with remnants of 
wood left but, unfortunately, have no 
illustrations of them. Most of the 
specimens here illustrated (pl. 5, fig. 1; 
pl. 7, fig. 2; pl. 8, fig. 2) are from the 
Esmeralda formation (Late Tertiary) 
about 4 miles west of Tonopah, Nev. 
