Fossils

Clam Shells in Shale (Chuckanut Formation, Fossil Creek, 50 Ma, 5 mi east of Glacier, WA on HWY 542)

WHAT ARE THEY?

  • Fossils are the remains or impressions of prehistoric organisms (usually at least 10,000 years old)

  • The patterns in some minerals have the appearance of fossils, but are not— these are known as Pseudofossils

  • The oldest fossils are found in chert.  The Apex Chert from Pilbara craton, Australia contains 3.4 billion year old Prokaryotes (single cell organisms that lack a membrane-bound nucleus)

FOSSILZATION PROCESSES

  • Perminalization — Preservation that occurs when minerals deposit in the spaces within organic tissue

  • External Mold — Formed when an organism decays leaving a void that contains an impression of the exterior of the organism

  • Cast — An External Mold that is later filled with minerals

  • Internal Mold — Formed when sediment or minerals fill the internal cavities of an organism

  • Authigenic Mineralization — A special form of cast/mold formation where mineralization occurs before significant decay

  • Replacement — Occurs when the original shell, bone, or tissue of an organism is replaced by minerals

  • Recrystallization — Occurs when the original compounds of the organism are different, but in a different crystal form (e.g. Calcite)

  • Compression — Contain films (carbon or other chemicals) formed from the reduction of organic substances by diagenesis. (diagenesis occurs when a sedimentary rock changes to a different type of sedimentary rock at temperatures & pressures too low for metamorphism)

  • Impression — A Compression fossil whose organic film was lost leaving an impression of the film

  • Adpression — A fossil containing Compression and Impression features (also named Compression-Impression)

  • Soft Tissue— Preserved original tissue usually containing high levels of collagen and iron (from hemoglobin)

  • Carbonization — Consists of thin carbon film silhouettes (called phytoleim) of organisms resulting from organic carbon compounds (a specialized form of Compression containing carbon)

  • Bioimmutation — Occurs when one organism overgrows another organism. A hard shelled organism may overgrow a soft tissue organism leaving a negative relief (external mold).

TYPES

  • Index - These are indicator or zone fossils that are used to identify geologic periods. The premise is that if the same fossil types are found in different sediments, then the sediments are of similar ages.

  • Trace— Formed by the activities of an organism. Examples include tracks, burrows, or feces (coprolites)

  • Transitional — Contain traits common to an ancestral group and a descendent group

  • Micro Fossils — Fossils that are less than 1mm in size

  • Resin — These are fossils that have been preserved in plant resin (polymers). Usually include bacteria, fungi, plants, and small invertebrates (such as insects and spiders). Vertebrate fossils are extremely rare.  Often contain preserved DNA fragments

  • Derived or Reworked — Fossils that found in rock that is more recent than when the organism died. Created by erosion & redepositon

  • Wood — Preserved wood that may or may not be petrified

  • Subfossil —Are partially fossilized (the fossilization process has not completed)

  • Chemical Fossils — Chemicals & fossil fuels (oil, coal, natural gas) that provide an organic signature for life

WHERE ARE THEY FOUND?

  • Fossils are common in sedimentary formations around the world.

  • Sedimentary deposits with exceptional levels of preservation , known as Lagerstatte, are less common (63 formations worldwide).

  • The Klondike Mountain Formation (Eocene, 49 MYA, near Republic, WA) is a Lagerstatte

  • Two Lagerstatte are found in British Columbia, Canada — the Burgess Shale (Cambrian, 508 MYA) and the McAbee Fossil Beds (Eocene, 63 MYA)

  • One Lagenstatte is found in Idaho. The Clarkia Fossil Beds (Miocene, 17 — 20 MYA)

  • A small cave on a hillside above Blue Lake, WA (north of Soap Lake) was formed when a rhinoceros was covered by a lava flow. The bones are stored in the Burke Museum in Seattle. (It is located on the west Side of a cove on the north end of the lake)

WHAT ARE FOSSILS USED FOR?

  • Collecting

  • Scientific research

  • Energy (oil, coal, natural gas)

  • Jewelry (e.g.  Ammonite earrings)

  • Diatomaceous earth (fossilized microscopic diatoms) is used to manufacture filters, ceramics, building materials, metal polishes, toothpaste, mechanical insecticides, livestock nutrition study agents (source of acid insoluble ash), anti-caking agents, absorbents, matting agents, reinforcing fillers for plastics, plastic film anti-block, support for chemical catalysts, cat Iitter, blood clotting activators, thermal insulators (used In fire resistant safes), dynamite stabilizing agents, and a growing medium for hydroponics and bonsai.

  • Tourism (e.g. Petrified Forest National Park in Arizona, Dinosaur National Monument in Utah, Florissant Fossil Beds In Colorado, John day Fossil Beds National Monument in Oregon, etc)