Newark Basin Field Trip for Petrology
Sunday, March 7th, 2010
Note: Before we leave each site, we'll determine Latitude and Longitude,
and collect a sample.
Stop 1 Preakness Basalt, The Second Watchung, outcrops near Rt. 78,
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.
Stop 2 Watchung Town Garage. Here two very different basalt flows are
present. we will examine the flows, suggest origins for both, and tests for
our ideas.
Alternate 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.
The quarry is operated by
Stavola.
Stop 3. Diabase Ring Dike at Round Valley Reservoir, Lebanon, NJa
Along the North Shore of Round Valley Reservoir, a Diabase that cooled
from the early Jurassic magma is exposed.
"Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine
grained to aphanitic chilled margins which may contain 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%)."
The amazing 22-31 cloverleaf "design" at Clinton.
Travel via Rt. 31 to Flemington. Lunch in Flemington, where we will go
through the Powerpoint printouts.
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. Highlands gneisses, sandstones and
carbonates weathered to laterites; arkoses derived from them washed into the
newly forming rift valley. Here is 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.
Stop 6. Perkasie Member of the Passaic 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 cobble and boulder conglomerates that coarsen as we
approach the border fault. The cyclic sedimentation includes shorter and less
widespread gray lake deposits.
At this locality the pebbles, cobbles and boulders are manly quartzites,
presumably from the Cambrian Hardyston Quartz that is still exposed along
the border fault today. USE EXTREME CAUTION HERE.
Stop 7. Holland, NJ. near the border fault, we will examine a small exposure
of breccia containing mostly 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. Has been removed by the highway department.
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 a flow that is chemically similar to Orange
Mountain Basalt. The beds here dip steeply enough that we can see the
alteration zone. Across the stream are explosion breccias where the basalt hit
wet sediment. If the water levels are low we may be able to collect
mudcracks on bars and copper mineralization at the contact; otherwise we
will return to the road and approach the contacts along the other shore.
Return to Campus.