The Upper Truckee River runs through the southern Lake Tahoe Basin and empties into Lake Tahoe. The document discusses the geological features formed by magmatic intrusion and glaciation in the area, including plutons, moraines, and erratics. It also describes some of the plant and animal species found along the Upper Truckee River, such as beavers, coyotes, northern chickadees, willow trees, and tamarack pines. Pollen from tamarack pines was noted to fill the air in spring, leading locals to call it the "spring orgy".

1. Upper Truckee River
FLORA, FAUNA AND FUN IN THE SOUTHERN TAHOE BASIN
Gizeh Ramirez
GEL-103

2. The Upper Truckee River runs through the southern Lake Tahoe Basin and empties into Lake Tahoe. The
Upper Truckee River valleys offers up a bountiful selection of geologic and hydrologic features, as well as
a healthy population of flora and fauna. Here we can find evidence of:
• Magmatic Intrusion
• Glacial scouring
• Glacial Deposition
• Erosion
• Varied Animal Life
• Spring Orgy
Unless otherwise noted, all material comes from study notes from Upper Truckee Hike 2016 or, my own
observations.
Photo credits are mine, unless otherwise noted.

3.  Due to the subduction of the ancient Farallon Plate by the North American Plate, an up welling of magma occurred
in the form of Plutons.
 As the magma came into contact with “country rock”, contact metamorphism occurred and roof pendants were
created.
 The many plutons of magma formed the Sierra Batholith (Collection of plutons).
 The magma plutons cooled slowly underground forming granodiorite “balloons”.
 The uplift of the Sierras increased the rate of erosion and eventually the granitic “balloons” were exposed.
 We see these plutons exposed today throughout the Lake Tahoe Basin.
(Post, 2016).

4.  The Tahoe Basin has been sculpted by several periods of glacier activity, mainly the Tioga and Tahoe glaciations.
 The Tioga Glaciation occurred approx. 25 ma.
 The Tahoe Glaciation occurred approx. 10 ma.
 Glaciers formed after the Sierran uplift occurred as the higher mountains attracted more moisture and cooler
temperatures.
 Cirques are evidence of places glaciers first formed.
 Moraines are the debris piles left behind marking a glacier’s passage and end.
 Erratics are boulders that were “plucked” by glaciers and left behind when the glaciers melted/retreated.
 Striations and polishing occur when a glacier moves across harder rock surfaces, leaving shallow grooves and in some
places polished or smooth surfaces.

5. Glacial Deposition
Erratics are boulders that were
“plucked” by glaciers and left behind
when the glaciers melted/retreated.
At left is a very large erratic we
encountered at the beginning of our
field expedition.
You can also see inclusionsnear the top.
Inclusons are bits of pre-existing native
rock that fell into rising magma that
cooled underground.
What did one erratic tell the other erratic? “It’s all good.”
Inclusions

6. Erosion
Erosion comes in two major forms in the
southern Tahoe Basin:
Aeolian Erosion: This is caused by the
wind. The wind picks up small particles of
dirt and rock and then can blast the face
of rock or a dirt bank, cutting away a new
surface
Water Erosion: Acts much the same way
as Aeolian, but with water.
It is important to note that there are three parts to
the erosion cycle:
Plucking: picking up material that has been abraided
by exogenic material;
Transportation: Moving material via air or water;
Deposition: Depositing or “unloading” material that
was transported.
We also have an excellent specimen for Relative Dating:
From bottom, Rock, Cobble, Gravel. Mud, then several layers of sand, followed by, dirt.
The Law of superposition is evident here as layers have been laid over previous layers. the Law of Original
Horizontality is also evident, This does not show deformations, intrusions or faulting.

7.  The southern Tahoe Basin is home to several interesting
species which might include:
 Beavers
 Coyotes
 Northern Chickadee

8. Beavers
 Beavers were native in the area until
trapping and hunting virtually
eliminated them, circa 1905.
 Beavers were reintroduced to the area
in 1923 and again in 1948.
 Beavers thrive along the Upper
Truckee River and several other larg
creeks and streams.
 Beaver dams are vital in helping to
return the clarity of Lake Tahoe to its
former grandeur.
 Beavers have long fossil history in the
Sierra Nevadas, as far back as the
Eocene, and many species of giant
beaver existed until quite recently,
such as Castoroides in North America.
(Mather)
Picture shows remaining dam behind Paradise Park on
the Upper Truckee. Most other dams were blown out by
the faux spring runoff.
Photo: John Post

9. Coyotes
The Coyotes in the Lake Tahoe Basin are usually seen near highways and are usually close by humans.
They weigh up to 20-25 lbs
Coyotes are part of the natural wildlife of the area and are highly adaptable.
Descended from a small civet-like mammal, they later developed into a larger animal, the Tomarctus and afthe megafauna event, became
smaller to today’s size, due, most likely, to some sort of change in food availability. (Mather)

10. Northern Chickadee
“Cheeseburger!”
The mountain chickadee is a small songbird, a passerine bird in the
tit family Paridae.
The mountain chickadees are known locally as the cheeseburger
birds, due to their call sounding like they are saying "cheeseburger"
The Mountain Chickadee is a native to the Basin and the western
United States.
The origin of birds refers to the initial stages in the evolution of
birds. The scientific consensus is that birds are a group of theropod
dinosaurs that evolved during the Mesozoic Era.
Tits have settled North America twice, probably at some time during
the Early-Mid Pliocene. The first were the ancestors of Baeolophus,
with chickadees arriving somewhat later. (Gill 2005)

11. Spring Orgy
One of the things we encountered on our expedition
every time the wind blew sheets of yellow pollen filled
the air. In fact the air was so full of pollen that it was all
over our clothing.
The pollen surrounded the entire area, therefore, many
locals call this the “spring orgy.”
 Tamarack, or Lodge Pole Pines (Pinus contorta murrayana) are
descendants of ancient gymnosperms.
 It is widely accepted that the gymnosperms originated in the late
Carboniferous period (Campbell & Reece, n.d.).
 This appears to have been the result of a whole genome duplication
event ~300 million years ago (jiao, 2011).
 Early characteristics of seed plants were evident in fossil
progymnosperms of the late Devonian period around 380 million years
ago (Jiao, 2011).
 This tree has many uses, such as shelter (tipis), medicinal (from the bark),
both internally and externally.

12. The Willow Tree
Its beaver food.
It stabilizes the bank of the river.
Where willow grows bears and
coyotes can raise their young.
Willows, along with junipers
were a favorite of Mammoths
and Mastodons as well as the
giant beavers of the Pleistocene.
The plant is hardy and has not
evolved very much since that
time. For, it’s environment, it is
the “perfect” shrubbery.

13. Rocks
Granodiorite
Tallac
Metasedime
ntary
Argonite
Andesite

14. Petrified Wood
This large boulder is a piece of
petrified wood and is NOT
normally found in this area.
This piece is thought to have
“migrated” into the basin from
the backside of Carson Pass. That
is a mere 18 miles in just 125
million years!

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