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 (>850°C) 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 |