This limestone formed during the late Ordovician Period, 443-460 million years ago, when Richmond, Indiana was covered by a warm, shallow sea. In this ancient sea, calcium-rich organisms such a scoral thrived. When these organisms died, they left behind their hard body parts and, after millions of years, the remains accumulated forming a very thick layer on the ocean floor. In succeeding millennia this calcium carbonate layer was buried, compacted, and transformed into limestone. Fortunately, parts of many organisms that lived in this sea, such as brachiopods, bryozoan, crinoids, and trilobites, have been preserved as fossils within this limestone.
During more recent times, the Whitewater River has exposed this impressive, fossiliferous, limestone formation, allowing us to take a look back at this point in Richmond’s history. Feel free to hunt for fossils in the fossil pile.
Where to Look for Fossils
The Gorge Park sites have produced many very nice specimens.
Look for the best and cleanest specimens in rubble piles near the bottoms of slopes along roads and creeks where nature and time have gently washed them from the hard rock. Excellent, delicate specimens can be found firmly attached to small collectible slabs in these rubble piles. It is never a good idea to hunt fossils too near roads, on steep banks or to crawl or hunt on or below cliffs.
Fossil hunters must be careful of automobile traffic and should always obtain permission before exploring private property. Fossils may be collected from rubble piles in Whitewater Valley Gorge Park.
There were many kinds of animals living in Richmond's ancient ocean. Some fossils, like clams, snails, and corals, are familiar to us because they are common animals in modern oceans. Other types, like the water filtering brachiopods and twig-like or sheet-like colonies of tiny bryozoan individuals, are not so familiar to us because they are not obvious animals in modern seas. Still others, such as the bug-like trilobites, have become extinct, and it is hard for us to understanding what they were like or what they did in ancient seas. No fossil of a backboned animal has yet been found in the Whitewater Formation.
Common Gorge Fossils
Corals
Were common, but there were not very many kinds. Most were large, horn-shaped shells, but some lived in Colonial, encrusting sheets, like bryozoa. Colonial corals have star-shaped pores which are much larger than those of bryozoa. Fossil corals, like modern ones, did not move around, but captured larger food particles from moving seawater.
Brachiopods (Brack/-ee-oh-pods)
Many kinds are found in the Gorge's Whitewater formation. Fossils have two, hinged shells and many specimens show a small round or triangular hole in the shell near the hinge. A stalk protruded through this hole and fastened an individual to something on the sea floor where it filtered food particles from the water.
Snails
Like bivalves, most had shells that dissolved soon after burial. Fossils are mostly shell fillings or impressions. Cyclonema was one local snail which had a preservable shell. Fossil snails, like their modern cousins, crawled around the bottom scraping algae and other small food particles from rocks and plants.
Trilobites (Try/-low-bites)
Were mostly small, bug or crab-like scavengers that found food on and in the bottom muds. Sometimes trilobite tracks and burrow fillings are found. Like modern insects and crabs, trilobites shed many jointed skins as they grew, but these fragile skeletons were easily broken apart by wave action. Usually only pieces are found.
Bivalves (By/-valves)
Or Clams, most of which wandered around filtering food from water, were very common. There were many kinds. Most did not have an easily preservable shell; thus most fossils are impression on the bottoms of bryozoan colonies which grew over them, or mud filings which hardened after seeping into a shell that was not quite closed at burial.
Bryozoa (Bry-oh-zoh/-ah)
Are related to and fed like brachiopods, but individuals were much smaller and lived in tiny, pin-sized pores which can sometimes be seen in the smooth, ridged, or bumpy surfaces of the best twig-like or sheet-like fossil colonies.
Ordovician System
Type Locality, description, and correlation: The Whitewater Formation was named by Nickles (1903) for exposures of bluish-gray rubbly limestone and interbedded calcareous shale along the Whitewater River at Richmond, Wayne County, Ind. As now recognized, the Whitewater includes at its base a dolomitic unit, the Saluda Member, and in its uppermost part shale and limestone formerly placed in the Elkhorn Formation. The Whitewater Formation contains a somewhat higher proportion of limestone than does the underlying Dillsboro Formation, but this alone is not distinctive it is the Saluda Member at its base that best distinguishes the Whitewater.
The Whitewater Formation conformably overlies the Dillsboro Formation (except as noted below) and is disconformably overlain by the Brassfield Limestone (Silurian) except in a few places in Clark, Jefferson, Ripley, and Decatur Counties, where the Brassfield is absent and the Osgood Member of the Salamonie Dolomite directly overlies the formation. The disconformable nature of this contact is emphasized by reworked Ordovician fossils in the basal part of the Brassfield Limestone.
Traditionally, the Whitewater Formation is recognized in Indiana only in the classic Cincinnatian outcrop area in the southeastern part of the state and in the near subsurface. Within this area the formation thins southward from about 100 feet (30 m) near Richmond to about 60 feet (18 m) near Madison, where the formation is reduced to its basal Saluda Member. At the top of the Maquoketa Group in northeastern Indiana, however, Gray identified an informal working unit as much as 160 feet (50 m) thick that is stratigraphically equivalent to the Whitewater and that, because it is dominantly limestone, is here assigned to the Whitewater Formation rather than to the laterally equivalent Brainard Shale. Thus extended, the Whitewater of northeastern Indiana rests, probably conformably, on the Fort Atkinson Limestone.
Near the top of the Whitewater in northeastern Indiana, especially in areas where the formation is thickest, are zones containing ferruginous reddish-brown ooids, beds of sedimentary iron ore, and limestone with hematitic cement. These have not been observed elsewhere in the Maquoketa in Indiana, but similar materials are found in the presumably correlative Neda Formation, which is at the top of the Maquoketa Group in northern Illinois. The Whitewater is the uppermost formation in the type Richmondian Stage, but its subsurface extension, where thickest, probably includes Ordovician rocks that are somewhat younger than any that are exposed in the Richmond area.
Whitewater Formation - Skeletal limestone and calcareous shale; dolomitic mudstone (S, Saluda Member) at base.
REQUIREMENTS:
- What are the Primary and Secondary rock type found in the Whitewater Formation?
- What is mudstone?
- Name three Richmond fossils found in the Gorge's Whitewater formation.
- Find a fossil in the nearby fossil pile and identify it. Optional: Post a picture of your fossil.
- Once you are at the coordinates observe the area, looking at the rock wall, describe what you see at the top of the wall and at the bottom of the wall. Explain what is happening and why. Estimate the height?
- The Whitewater Formation was named by who and in what year?