Big Brook Park: Fossil Hunting in Monmouth County, New Jersey

Plan your visit

Generally open to casual rockhounding

County

Monmouth County

State

New Jersey

Nearest road

Boundary Road

Postcode

07746

Coordinates

40.30600, -74.25600

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

Land & collecting status

Generally open to casual rockhounding

Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig.

Access note: Free public collecting under Monmouth County Park System rules. Use the Boundary Road parking lot in Marlboro: the Hillsdale Road entrance in Colts Neck closed in 2025. Limit of five fossils per person per day, trowel blades no longer than six inches, and collect only from within the stream water line. Digging the banks is prohibited, and groups of 15 or more need a permit.

Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.

Best time to visit Big Brook Park

Comfortable months (45 to 90°F highs)

Best months: March to December. Typical highs run 87°F in midsummer and 42°F in midwinter, with winter lows near 23°F.

Climate normals: NOAA 1991-2020 monthlies, FREEHOLD-MARLBORO station (1 mi away).

Geology at Big Brook Park

This spot sits on Navesink Formation, mapped as sand that formed roughly 72 to 66 million years ago. Reworked sediments like these can carry fossils eroded from older beds upstream, typically as rolled bone fragments, teeth, and shell material.

Mapped unit

Navesink Formation

Age

72–66 Ma (Late Cretaceous)

Rock types

sand

Elevation

180 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Sources & verification

Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.

• New Jersey Geological and Water Survey
• Monmouth County Park System, fossil collecting rules
• Sterling Hill Mining Museum
• Community submissions reviewed against published agency rules