Geology 380 Field Trip

April 25, 2009

Rachel Grove

 

STOP #1: LAKE BLOOMINGTON SPILLWAY





 


Examining the till deposited by glaciers.  We could determine that there was limestone present because acid reacted vigorously with the till.

 


Unsorted sediment from the last two glacial advances.

 


Limestone cobble with flat sides and striations due to glacial movement.


Delicious.

 







 



 



 

STOP #2: MATTHIESSEN STATE PARK


Bottom of the canyon

 



 


At the waterfall.  The walls of the canyon are approximately 165 feet of pure St. Peter’s sandstone.  This sandstone is extremely pure and contains almost pure quartz.  This particular sandstone is unusual because of its wide geographical occurrence (about 225,000 square miles).

 


One of the recesses in the canyon walls.  The sandstone that makes up the canyon walls is prone to erosion from the swirling water. 

 


Looking at the sand formed from weathered St. Peter’s sandstone (about 480 million years old).

 


Lots of layering in the canyon walls.

 


Vertical jointing in the sides of the canyon.  They are widely spaced and some extend all the way up while some don’t.

 


Iron oxides stain the walls. 

 


The whole group!

 

 

STOP #2B: OUTCROP ALONG THE VERMILION RIVER


Don’t do it Tony!!!!!!!

 



 


Sloping layering.  We are on the axis of the LaSalle monocline, the largest geologic structure and one of the few examples of folding in Illinois.  The rock is dolomitic limestone of the Platteville group and is full of marine fossils. 

 



STOP #3: VERMILION RIVER


This surface represents an unconformity of approximately 150 million years.  The eroded strata that you can’t see in this picture are due to the uplift of the LaSalle monocline.

 

STOP #4: STARVED ROCK STATE PARK

Starved Rock is about 125 feet tall and is made of St. Peter’s sandstone.  This picture overlooks the Illinois River Valley.  The valley originated from catastrophic floods 15,000 to 10,500 years ago.  When lakes broke through moraines, water filled the channel.

 



 



 

STOP #5A: BUFFALO ROCK STATE PARK

From 1934 to 1942, a 22” coal seam was mined by the Buffalo Rock Coal Company, creating spoil piles, acid mine drainage, and soil erosion.  In 1985, the land was reclaimed and reseeded with native plants.

 



 

STOP #5B: BUFFALO ROCK STATE PARK—ABANDONED SILICA SAND QUARRY


Quarrying St. Peter’s Sandstone is an important local industry.  Annual production is about 4.9 million tons, valued at about $300 million.  Sandstone is so friable that it is mined with high-power hoses.

 


Ottawa is the silica sand capital of the world and is home to the largest silica sand producing plant in North America.