Newark Basin Field Trip for Petrology
Saturday, March 29th, 2008
Note: Before we leave each site, we'll measure the strike and dip, and collect
a sample.
Stop 1 Orange Mountain Basalt, outcrops near Seeley's Pond Parking Lot,
Berkeley Heights, NJ.
This flow is Early Jurassic. It is a ridge-former because it is resistant to
erosion compared to the adjacent Passaic (Brunswick) sediments.
Joint systems in this area influence stream flow directions.
Kari will talk about her Senior Thesis on this area.
Kari demonstrates use of Brunton compass
Stop 2 Chimney Rock, Bound Brook, New Jersey. A peek through the fence
reveals the flow heated red shales and siltstones of the uppermost Triassic
Passaic Formation. Along the stream, we'll examine the interface between
the two lowest of four flows.
Orange Mountain Basalt
Hornfels
Passaic Fm. = " Brunswick"
Stop 3. Diabase at Round Valley Reservoir, Lebanon, New Jersey.
Along the North Shore of Round Valley Reservoir, a Diabase that cooled
from the early Jurassic magma is exposed.
Chris, Kari, Anna, Melissa, Ryan at the Diabase
"Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine
grained to aphanitic chilled margins which may contain tachylite (dark mafic glass).
Diabase normally has a fine, but visible texture of euhedral lath shaped plagioclase
crystals (62%) set in a finer matrix of clinopyroxene, typically augite (20-29%), with
minor olivine (3% up to 12% in olivine diabase), magnetite (2%) and ilmenite (2%)."
http://en.wikipedia.org/wiki/Diabase
Rest Stop, Park Headquarters.
Travel via Rt. 31 to Flemington. Lunch in Flemington.
Lunch discussion of Newark Basin using Roy Schliche's slides
Then Rt. 12 to 523 South (Sergeantsville Road) to Stockton, NJ near the
base of the Late Triassic.
Photo of roads to 29N heading up-section
Stop 4. Stockton Formation, Raven Rock, NJ.
The Stockton is the basal sediment in the Newark Basin. Usually interpreted
as fluvial, it doesn't show the cyclicity of younger Lockatong and Passaic
(formerly Brunswick) Formations. Sand-size particles of Proterozoic
gneisses and granites, plus Paleozoic sandstones and carbonates, washed into
the newly forming rift valley. We'll see the typical form, sandstone redbeds.
Stop 5. Lockatong Formation. The middle unit of the Late Triassic is the
Lockatong Formation. It can be black (organic-rich persistent lake with
Semionotus fish) or gray (very shallow lakes with frequent drying and
mudcracks) or red (the last stop, see below). It shows strong Milankovitch
cyclicity. N 40o 26.850' W75o 03.900'
Stop 6. Perkasie Member of the Passaic ( Brunswick) Formation, Milford,
NJ.
This is the Pebble Bluff locality. The Passaic is the uppermost Triassic
sedimentary deposit in New Jersey. It contains typical redbeds that range
from mudstones and fine sandstones that are usually interpreted as playas
and pediments , to coarse cobble and boulder conglomerates that coarsen as
we approach the border fault: fanglomerates. The obvious cyclic
sedimentation includes shorter and less widespread gray lake deposits.
Fanglomerate layer near the border fault
All sandstones and siltstones further away
The pebbles, cobbles and boulders are all quartzites, presumably from the
Cambrian Hardyston Quartz that is still exposed along the border fault. They
grow larger and more angular as we approach the fault.
Stop 7. Holland, NJ. Near the border fault, we will examine a small
exposure of breccia containing carbonate blocks. These probably were
derived from the Cambrian Leithsville Dolomite, which lies above the
Hardyston is also exposed along the fault.
Return to Frenchtown and thence to Flemington via Rt. 12.
Stop 8. Lockatong Formation, Flemington, NJ. These exposures along route
12 are dark gray to black persistent lake (high-stand) and lake margin
deposits. I want to stop briefly to show you mudcracks and possible
burrows, and then asymmetrical ripple marks from two slabs that have been
moved to our side of the road.
Stop 9 (Final Stop) Mine Creek Park and Morales Nature Trails, Capner St.,
Flemington, NJ. Here is the red form (low-stand) of the Lockatong
Formation in contact with the Orange Mountain Basalt. The beds here dip
steeply enough that we can see the alteration zone. Anna will discuss her
work on this important geo-cache.
Hornfels
Return to Campus.
Chris and Anna sample the Explosion Breccia
Additional photos
Chris, Ryan Melissa Watchung
Anna, Chris, Kari GANJ Field Trip 2007
Vug in Basalt, former Watchung Quarry
Dan, Prof. Smart,
GANJ Field Trip 2007