Table 1 - Simplified Geologic History of the New York City Area

Geologic

Radiometric

Stratigraphic/

Original Rocks or Sediments

Geologic Event

Period

Age in m.y.

Rock Unit

 

 

Pleistocene

 

Glacial detritus

Till, sands, clay

Continental glaciation, leaving moraines and outwash plain

Cretaceous to Tertiary

Coastal Sediments

Sands, clay, and conglomerate

Shallow marine deposition on continental shelf

Jurassic

200

Newark Series,

Red sands, shales, and conglomerates

Rift-basin formation and basaltic volcanism related to

Triassic

 

Palisades diabase

basalt, diabase

extension; eventually, the opening of the Atlantic Ocean

 

 

Unconformity

 

100 million years of erosion

Devonian

380

Two-mica granites

 

Acadian orogeny, here expressed by intrusion of many small

 

(Stops 3, 4, 5)

 

 

two-mica tourmaline granites, shearing, and retrogressive

 

 

 

 

metamorphism at about 550 C and 20 km depth

 

 

 

 

Produced muscovite schist and tremolite marble

 

 

 

 

Uplift and erosion

Ordovician

~445

Anatectic granites

 

Late phase, Taconian orogeny: upright folding, intrusion of

 

(Stops 3,5)

 

 

granites, metamorphism at peak

 

 

 

 

temperatures (>850C) but reduced pressure (~26 km depth)

--------------------

(Stop 5)

Hartland formation,

Island Arc volcanic rocks and associated

Emplacement of ophiolite (serpentinite) and exotic Hartland

 

 

serpentinite

well-bedded shales, sands, and

island-arc terrane over (deformed) North America

 

 

 

minor limestone, and ultramafic rocks

 

 

~450

Anatectic granites

 

Early deformation, Taconian orogeny- Thrust faulting- Slices

 

 

 

 

of Neoproterozoic rock emplaced over younger Walloomsac;

 

 

 

 

high-pressure metamorphism (>40 km depth)

 

 

 

 

and granitic intrusion (due to melting of crust)

Ordovician

 

Walloomsac Schist

Sulfidic, carbonaceous shales, sands,

Deposition in a narrow basin, which deepend as the exotic

 

 

 

and minor limestones

Hartland volcanic arc terrane impinged on North America

 

 

Unconformity

 

 

Cambro-Ordovician (Stop 2)

Inwood Marble

Dolomite, limestone, minor siliceous beds

Shallow marine deposition, continental shelf (carbonate bank)

 

 

Unconformity

 

 

Late

(Stop 1)

Ned Mountain

Bimodal volcanic rocks; sands, limestone,

Rift-basin deposits and bimodal (mafic/felsic) igneous activity

 

 

formation

minor conglomerate, shale

record lithospheric extension, which prompted

Neoproterozoic

~560

(inc. Yonkers gneiss)

 

the birth of the Iapetus Ocean; deposits range from

 

 

 

terrestrial/shallow water (Yonkers gneiss member,

 

(Stop 3)

Manhattan Schist

Sands, shale, basalt

Ned Mountain fm.) to deeper water (Manhattan Schist)

 

 

& "Bronx Zoo-type"

 

 

 

 

strata

 

 

 

 

Unconformity

 

400 million years of erosion

Middle

1000 to 1200

Fordham Gneiss

Subduction-related volcanic and plutonic

Grenvillian orogeny; high-grade (granulite-facies)

Proterozoic

(Stop 4)

 

rocks with minor sediments; mafic bodies of varied origins

metamorphism, granitic intrusion, deformation; Volcanic arc activity