Saratoga Geology II

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Saratoga Geology II

• ES 105

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Last Lecture

• Geologic timing and history of Saratoga area
• Geologic Processes (convergence, divergence)
• Today we will talk about the rocks of Saratoga
• Recent geologic history (last few million years)

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Q.O.D.

• From last lecture, how many times did continents
  crash into NA?

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What are the rocks of Saratoga

• Gneiss and schists metamorphic from high heat
  and pressure
• Grenville Rocks (ADK) form deep in Earth (25 km
  down) How old are these rocks? metamorphic
  rocks high in Fe, Al, SiO2

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What are the rocks of Saratoga

• Next oldest - Sandstones Potsdam sandstone
  (Upper Cambrian)
• Grain size is sand where do you find sand?
• High energy - Beach environment
• Mostly SiO2

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What are the rocks of Saratoga

• Next - Limestones and Dolostones carbonate
  rocks formed in shallow, warm water (Hoyt
  Limestone, Gailor Dolostone)
• Ages range from Cambrian to Ordovician time (400
  to 500 million years old) once covered ADKS,
  now eroded
• Sedimentary rocks high in Ca, Mg, and CO3

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What are the rocks of Saratoga

• Next Shale Canojaharie Shale now eroded
  away from west side, underlies sediments on east
  side of Broadway
• Made up of muds
• Where are muds deposited?
• Age is Middle Ordovician

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Last piece of Saratoga Geology glacial deposits

• Glaciers have covered Saratoga region several
  times over the last 2 my
• We are in an Ice Age but are in an interglacial
  Ice will come back!
• Climate started to cool 10 mybp know from
  fossils and pollen
• Eventually it was cool enough where all snow did
  not melt in summer time

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Lets talk glaciers

• How do glaciers form?

Snow Cloud cool winds drop snow
Big mass and sqeeze out
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Lets talk glaciers

• How do glaciers form?

Snow Cloud cool winds drop snow
Big mass and sqeeze out
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Glacial Coverage 20,000 years ago
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New York State Coverage
22,000 ypb
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What do glaciers take away?

• Glaciers are good eroding agents
• The ice can take away most soil and strip down to
  bedrock
• Rock clasts in ice tools can scratch and
  erode bedrock form fine grained sediment
  glacial flour - clay
• Big chunkies erratics size of house or larger
  can be picked up and transported by glaciers

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What do glaciers leave behind?

• Everything they take away but leave them in a
  different place like little kids or big kids
• Lets look how glaciers melt and what types of
  deposits we can find

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Long Island
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Glacial Melting

• Melt from margins
• Thinnest melts to open islands (ADK)
• Thickest melts last (valleys Hudson Valley)
• Water collects in valleys and if block forms
  glacial lake
• North flowing rivers blocked by ice
• South flowing river blocked by terminal moraine
  or by ice chunkies

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Glacier melting processes
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Glacial deposits and where do they come from?

• Till clay to boulders deposited everywhere
  come from base of glacier or end of glacier
  (deepest unit in ground)
• Lake clays deposited in glacial lakes
• Beach sands and delta deposits deposited at
  edge of lake or at mouth of river entering the
  lake (shallowest - near surface)

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Glacier
Till
Outwash Sand
Glacier
Till
Glacier
Clays
Till
Bedrock
Clays
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Where do glacial deposits come from?
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Saratoga Stratigraphy
Beach Sand
Lake Clay
Outwash sand
Till
Erosion
Deep Ocean
Shale
Warm, shallow, tropical ocean
Limestone
Dolostone
Old Beach
Sandstone
Old mountains
Erosion
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