are 



Keys to the Past 



By Natalie Eason Hampton 



To grasp a fossil in your hand is to hold a hey to the door of the past, 

 en unearthed from the sediments in which they were huried. fossils help scientists 

 reconstruct a picture of what life was like on this planet millions of years ago. 



Take dinosaur fossils, for instance 

 Information gleaned from these fossils 

 and surrounding sediments has allowed 

 researchers to accurately depict these 

 giants and their habitat. Throw in a little 

 Madison Avenue marketing to capture 

 the fancy of children, and there's hardly 

 a child in America that can't say Tyran- 

 nosaums. 



All fossils aren't as 

 glamorous or marketable 

 as those of the dinosaur. 

 But all are important to 

 scientists looking for 

 clues about weather 

 patterns, ocean levels, 

 species availability and 

 habitat during ancient 

 geologic periods. 



When it comes to 

 finding fossils, North 

 Carolina's Coastal Plain 

 offers dozens of sites 

 where professionals and 

 amateurs can dig for 

 fossils millions of years 

 old. You can dig alone or 

 join a fossil expedition 

 sponsored by a club or 

 museum (see story, page 18). 



Scientifically speaking, fossils are 

 remains, impressions or traces of ani- 

 mals or plants from former geologic 

 ages. Sometimes they are the hard parts 

 of organisms such as shells, bones and 

 teeth that have survived millions of 

 years. Other times, they can be impres- 

 sions or molds left behind by a plant or 

 animal long since decomposed. And yet 

 another kind of fossil, a cast, is a min- 



eral or sediment replica of the original 

 organism. 



Fossilization usually begins when 

 the hard parts of an organism become 

 embedded in mud or covered by sand 

 from a river, lake or ocean. These hard 

 parts may remain unchanged for mil- 

 lions of years, despite changes in the 



All photos by Scott D. Taylor. Courtesy of Kieth Sturgeon, North Carolina Maritime Museum 



surrounding sediments that compress to 

 form limestone or sandstone. 



However, most fossils are altered 

 through contact with groundwater. 

 Percolating groundwater may cause 

 fossils to lose their original color and 

 luster, become stained with minerals, 

 dissolve or be replaced with minerals 

 such as calcite, pyrite or quartz. 



Fossil tree trunks and branches may 

 become petrified when their pores are 



filled with minerals, a process called 

 permineralization. Some fossil wood 

 found in North Carolina is so thoroughly 

 permineralized that it can be cut with a 

 rock saw and polished to show its cellu- 

 lar structure. 



The ocean has advanced and re- 

 ceded across the Coastal Plain many 

 times during the state's 

 long history. Each time, 

 new layers of soft sands 

 and muds were laid and 

 sometimes eroded. These 

 soft substrates acted as a 

 time recorder, preserving 

 life-forms present during 

 geologic periods known 

 as epochs. Every epoch 

 is chronicled by a geo- 

 logically distinctive layer 

 of sediment. 



"Each bed (forma- 

 tion) is like a page in a 

 book on the geologic 

 history of the Coastal 

 Plain," says Stan Riggs, a 

 Sea Grant researcher and 

 geologist at East Carolina 

 University. "The entire 

 Coastal Plain (of North Carolina) is 

 made up of marine sediments stacked 

 like a deck of cards." 



Hundreds of species of fossil plants, 

 seashells, bones and teeth ranging from a 

 few thousand to 80 million years old can 

 be collected from Tar Heel riverbeds, 

 road cuts, beaches, quarries and mines. 

 Sometimes the fossil finds are remains 

 of marine creatures — sharks, whales, 



Continued 



COASTWATCH 1 1 



