•
Appalachian Highlands Division •
Piedmont Province •
Gettysburg-Newark Lowland Section •
Leithsville Formation • Brunswick Formation • Allentown Formation •
Lockatong Formation At Mill Creek's headwaters, at the confluence of Lahaska Creek and Watson Creek, is the Allentown Formation, a
sedimentary layer of rock deposited during the
Cambrian.
Mineralogy includes
dolomite,
limestone,
chert,
siltstone,
oolite,
stromatolites, and sharpstone
conglomerate. After a very short distance, it flows into the
Leithsville Formation, a sedimentary layer also deposited during the
Cambrian.
Mineralogy includes dolomite, some containing
sand or
shale,
calcareous shale, and chert. It then flows into the
Brunswick Formation, a sedimentary layer laid down during the
Jurassic and
Triassic. Mineralogy includes shale,
mudstone,
siltstone, green and brown shale. Shortly before it reaches the Neshaminy, it flows into the
Lockatong Formation, another formation of sedimentary rock. Mineralogy includes a dark-gray to black
argillite, some zones of black shale, and some limestone and calcareous shale. ==Named Tributaries==