http://www.geosociety.org/gsatoday/archive/24/6/abstract/i1052-5173-24-6-4.htm

Patricia L. Corcoran, Charles J. Moore, Kelly Jazvac
An anthropogenic marker horizon in the future rock record
GSA Today, v. 24, no. 6, doi: 10.1130/GSAT-G198A.1

ABSTRACT
Recognition of increasing plastic debris pollution over the last several
decades has led to investigations of the imminent dangers posed to
marine organisms and their ecosystems, but very little is known about
the preservation potential of plastics in the rock record. As
anthropogenically derived materials, plastics are astonishingly abundant
in oceans, seas, and lakes, where they accumulate at or near the water
surface, on lake and ocean bottoms, and along shorelines. The burial
potential of plastic debris is chiefly dependent on the material?s
density and abundance, in addition to the depositional environment.
Here, we report the appearance of a new ?stone? formed through
intermingling of melted plastic, beach sediment, basaltic lava
fragments, and organic debris from Kamilo Beach on the island of Hawaii.
The material, herein referred to as ?plastiglomerate,? is divided into
in situ and clastic types that were distributed over all areas of the
beach. Agglutination of natural sediments to melted plastic during
campfire burning has increased the overall density of plastiglomerate,
which inhibits transport by wind or water, thereby increasing the
potential for burial and subsequent preservation. Our results indicate
that this anthropogenically influenced material has great potential to
form a marker horizon of human pollution, signaling the occurrence of
the informal Anthropocene epoch.

http://www.geosociety.org/gsatoday/archive/24/6/pdf/i1052-5173-24-6-4.pdf