A Walk on the Beach at Garvies Point Preserve EarthCache
A Walk on the Beach at Garvies Point Preserve
-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
Garvies Point Museum and Preserve is a center for research on Long Island geology and a valued resource in the study of the Island's Native American archaeology.
The beach at Garvies Point Preserve offers the visitor a place to observe a number of unique geological features that are not found together in such a limited area elsewhere on Long Island. Walk along the beach and you may discover plant fossils, lignite and pyrite nodules washed out from Cretaceous clay, shale, and sandstone that were deposited here at the end of the Age of Dinosaurs 70 million years ago. The sharp-eyed observer will encounter "Indian Paint Pots", the concretions for which Garvies Point is famous.
The natural, unaltered North Shore boulder beach follows the base of bluffs that are made up of Ice Age deposits. Excellent examples of a variety of erosion, deposition and weathering features are available to see, as are the fresh water springs that surface along the bluffs. Note the three granite erratics along the shoreline as well. This is an ideal photographic location.
Concretions of Garvies Point
The concretions found on the beach at Garvies Point Preserve are commonly referred to as "Indian Paint Pots" or "Rattle Stones". These are composed of a combination of iron oxides which include hematite, limonite and goethite. Were they made by Native Americans? No, they are formed naturally. Were they used by them? Why not? These concretions are an excellent source for coloring pigments of red and yellow ocher and there were no hardware stores or Home Depot available at this time.
"Paint Pots" are a product of physical and chemical
weathering of pyrite nodules associated with the 70 million years old Cretaceous clay deposits exposed along the shore. Metallic crystal cubes of pyrite (iron sulfide) nodules are found on lignite, an early form of coal, formed from carbonized Cretaceous plant debris that is imbedded in the clay. When pyrite is washed into the surf and exposed to the atmosphere, two processes take place that transform a pyrite nodule into an "Indian Paint Pot". First, iron sulfide is changed to iron oxide chemically through oxidation. Second, the nodule becomes smoother and rounder by abrasion. The end product is a round, reddish concretion.
"Rattle Stones", on the other hand, are produced by subsurface precipitation of iron oxides around a sediment core, typically a lump of clay. When this mass dries and solidifies, the clay inside will shrink and become loose creating a "rattle" when the concretion is shaken. Both types of concretions have the ability to incorporate sediment in their outer wall during colloidal stages of oxidation and precipitation. In this way most concretions found have an "armor" containing sand, pebbles, etc.
A detailed exhibit on The Concretions of Garvies Point can be seen at Garvies Point Museum, 50 Barry Drive, Glen Cove, NY 11542. The museum is open from 10am to 4pm Tuesday through Sunday. The preserve is open from dawn to dusk daily.
Written by: George Allgaier, Curator of Geology; 2003
Garvies Point Museum & Preserve
Reprinted in this earthcache activity with written permission of the author.
To log this earthcache: post photos, log the find, and email answers to CO:
1. Take and post a photo which includes yourself and/or your GPSr at one of the several sites where cretaceous clay deposits are found along the bluffs. Describe the feel and texture of the clay.
2. Notice the areas where the clay has washed down to the rocky beach, and is intermingling with the rocks. What colors do you see in the usually-white clay? Why?
3. If you have children with you, pick up any two reddish rocks. Rub them together briskly for a few seconds. Dab a drop or two of water on the powder that is released and use this residue to "paint" a line or two on your hand. Post the photo of their "artwork" with your log. What is the substance that created the reddish "paint?"
4. If you are fortunate enough to notice a "paint pot" or segment of a concretion, take a photo of it and post it with your log.
DO NOT COLLECT ANYTHING FROM THIS PRESERVE . TAKE ONLY PHOTOGRAPHS; LEAVE ONLY FOOTPRINTS!
Additional Hints
(No hints available.)