Coggshall

Introduction

Figure 1:  (Wood 2016)  Basket to hole #12, looking back up to
 tee.  Rock  outcrops are mica rich schist of the
 Littleton Formation.

Coggshall is a relatively new course built in the woods of Coggshall Park if Fitchburg

Massachusetts.  Sometimes known for its very thick undergrowth and rugged topography, the course is still being shaped into its mature form.  Beyond its rough edges Coggshall has a strong and varied technical layout with large elevation changes and requiring a wide variety of shots.  Like nearby Devens, the underlying bedrock has a large impact on the layout and challenge of the course, helping to give the course its unique flow and feel. Coggshall might sometimes be frustrating at this point in its development but there is a lot of challenge, beauty and cool geology here. 

Figure 2:  (Wood 2016, Massachusetts Geological Survey) 

  Terrane map of Fitchburg area showing surface

 distribution of terranes.   

Tectonic Setting

Figure 3:  (from Sorota 2013).  Cross sections showing

 the area of deposition of sediments in the Merrimack 
Terrane (MT) during Silurian to Devonian time.  In 
Silurian time (A) sediments are derived from both
 Laurentia and Ganderia (block to right of picture).
  In Devonian time (B) Avalonia collides with 
Laurantia,subducting under the Merrimack Terrane,
 triggering formation of igneous intrusions (in red)
 and compressing the MT sediments, causing the
 metamorphism we now see in the sediments.  

Coggshall, like Devens is in what geologists call the Merrimack Belt.  The Merrimack Belt stretches in a northeast trending line from east-central Connecticut to southeastern Maine. Though the rocks of Coggshall are now hardened and heavily deformed by metamorphism they began their life as muds and sands that were deposited during Silurian time (420 MYA) in a basin between two portions of an exotic terrane called Ganderia.  An exotic terrane is a large region of bedrock that was originally formed in a location distant for the other rocks that surround it. In the case of Gandreria, it likely was formed off the coast of Amazonia (Now part of South America) or Africa. Though Ganderia is exotic, the sediments that were to eventually form the rocks of Coggshall likely formed later, when Ganderia had already moved to a location near the coast of Laurantia (North America).  The deposition of sediments in this basin had ended by or during the onset on the Acadian Orogeny (400-360 MYA), which was caused by the collision of the Avalon Terrane with the now enlarged Laurantia (with

Ganderia forming its “eastern” margin).  This event put the sediments of the basin under high pressure and temperature, changing them into metamorphic rocks called schists (originally mudstones and shales) and quartzites (originally sandstone).  The presence of the Fitchberg Complex (400 MYA), a set of Granites and Granodiorites that intruded the sediments, shows that subduction, melting and volcanism accompanied the metamorphism in this area. In addition this entire sequence of metamorphic and plutonic rocks were complexly folded and compressed.  Later deformational events such as the Alleghanian orogeny and Mesozoic rifting, seem not to be prevalent at Coggshall though these events can be easily be masked by the earlier deformation. For more info on the history of the Merrimack Terrane, look at the post on Devens.

Bedrock Geology

Figure 4:  (Pepper and Wilson 1978, Wood 2016)   Portion of Bedrock

 Geologic Map of Fitchberg Quadrangle.  Area with Horizontal Lines

 is the Littleton Formation, Unlined areas are the Fitchburg pluton.

   Symbols show NW trending foliation with a moderate SE dip. 

Approximate location of holes shown in red.   

At Coggshall the metamorphosed sediments of the Merrimack Terrane are grouped as part of the Littleton Formation.  At other locations in the park and in nearby Fitchberg, the Fitchburg Complex, a series of granites and granodirorites of Devonian age, makes up the majority of the bedrock outcrops.   The entire disc golf course at Coggshall appears to be underlain by the Littleton Formation. 

The Littleton Formation

Figure 5  (Wood 2016)  Mica rich schist near hole 8, bumps on rock are

 small garnet crystals and Andalusite pits.

The Littleton formation mainly consists of mica rich schist with garnet and andalusite crystals.  The garnet crystals are fairly small, but can easily be seen with the naked eye and have a somewhat ball-like appearance.  Garnets crystal form is dodecahedral (12 sided) and when looked at closely you might see some of their crystal faces.  Andalusite is a metamorphic mineral indicative of high temperature, moderate pressure environments and its presence here is likely due to the nearby location of the Fitchburg Pluton whose heat during its emplacement would have caused the crystal growth.  Most of the andalusite crystals have weathered out or have been replaced by chlorite or clay minerals, but there locations can still be seen as rectangular pits in the surface of the rock. 

Figure 6:  (Wood 2016)  Mica rich schist near tee hole 8, The
 reflective sheen of the rock is due to the mica mineral grains that
 are the dominate mineral in the rock.  Mica grains are all aligned
 to form the dominate foliation.  Rippled appearance of the rock is due
 to one or more secondary deformation events.  Black dots
 on rock are tiny garnets.

Upper 9

Figure  7:  (Wood 2016) Hole #6 Basket in background.  Layering in

 southeast facing hillside due to foliation of Mica Rich Schist.

Southeast facing slopes tend to cut sharply across the foliation,

 highlighting the wavy, layered texture of the rock.  

Good exposures of the mica rich schist can be seen on the upper part of the course (holes 4-12), both in lose rocks littering the ground and in outcrops that form NW trending linear ridges that guide many of the holes (4,5,7,12).   Throughout the area the schist contain a strong NW trending, SE dipping foliation, developed through alignment of mica grains and banding of layers with differing composition.  The schist presents itself differently depending on the direction the terrain is sloping.  NE facing sloped tend to fall parallel to the foliation and has a smooth shiny texture while southwest facing slope cut across the foliation, forming cliffs and clearly showing the layering in the rocks. Some of these layers are more resistant to erosion forming linear ridges while less resistant ones form flat areas or valleys. On Hole 5, the tee shots moves up a valley that follows the trend of this foliation.  On hole 6 you drive across this same valley, starting and hopefully landing on the resistant ridges on each side. Well exposed bedrock outcrops of the schist occur on the fairway of hole 10 where small garnets can be clearly seen and the foliation dips steeply into the ground.  The basket for Hole 11 is placed in an old rock quarry, and the outcrops on the periphery of the quarry clearly show the foliation and fracture tends in the rock.

Figure 8:  (Wood 2016)  Hole 9 fairway. The foliation of the Littleton formation

 has a wavy appearance, showing secondary deformation.

Figure  9  (Wood 2016)  Hole #12, Old rock quarry with excellent exposures of
mica rich schist showing foliation and preferred fracture directions.

Lower 9

Figure  10:  (Wood 2016)  Looking back to Basket of #3.  NNW

 striking ridges dominate the landscape on holes 3,13,14,15.

  These ridges tend to be short (50-100 ft long) where one

 ends the next one usually rises 10-30 feet to theleft.

  Notice ridge below the camera position ends just before basket.

  Next ridge rises just after basket to the left.  This effect is 

likely caused by a series of small faults that occupy the valley.

The lower 9 holes of the course (1-3, 13-18), lie below and to the Northeast of the upper nine.  Here the Littleton formation is more varied, containing a mica rich schist that with linear bands of quartzite that are stretched out in the direction of foliation.  These quartzite rich bands form ridges that stand a few feet above the surrounding terrain.  These ridges are often not very long (< 200 ft) and when one stops there is usually a new ridge that pops up 10-30 feet to the left.  This cutting and consistent displacement of the ridges might suggest a lot of small faults and fractures in the valley, which is probably the reason for the location of the valley as fractured rock in more easily eroded.  This step like nature to the ridges is best seen on hole #3,

where left side of the fairway follows a series of these ridges. This same ridge likely continues on the left side of 13 where some massive concentrations of quartz can be found.  Holes 14-15 go back and forth, paralleling the trend of the ridges.  At the top of the steep hill where the 16 basket and 17 tee are placed, the Littleton formation again changes its nature, becoming much more dull and lacking in quartzite layers.  Possibly because of this compositional change, there are much fewer bedrock outcrops on this hill, making it difficult to determine the exact nature of the unit.

Figure 11:  (Wood 2016)  NE facing slope of ridge just behind

 basket #3. NE facing slopes tend to cut directly across the

 foliation, showing the layered alignment of mica grains

 and slight compositional differences between layers.  Larger

 and more resistant quartz rich block in lower part of image

appear  to have also been rotated during metamorphism.

Figure 12: (Wood 2016).  Quartzite Layers in Mica Schist,
 near #3 Basket.

Figure 13:   (Wood 2016)  Hole #13 fairway.  Large block of
quartz. During metamorphism, quartz can dissolve in high
 temperature water and be recrystallized in large masses.  

I hope this write up on Coggshall has been interesting and will encourage you to check out this course if you haven’t done so yet.  Up next for me is most likely going to be Borderlands, home to a giant glacial erratic, Deadham Granite and many, many, many, stone walls.