Fossil Record & Geologic Time Lab

Question 1

Unaltered remains (Unaltered remains)

Answer 1

When hard parts of a fossil remain unchanged due to their resilience

Question 2

Desiccation (Unaltered remains)

Answer 2

Freezing/mummification

Question 3

Embedding (Unaltered remains)

Answer 3

In wax or amber

Question 4

Recrystallization (Altered Remains)

Answer 4

Old minerals rearrange, usually involving an increase in crystal size. In shells, this destroys the original, internal reflective structures, making them appear dull

Question 5

Replacement (Altered Remains)

Answer 5

Old minerals are replaced with new ones

Question 6

Permineralization (Altered Remains)

Answer 6

Pores or empty body chambers of organisms are filled with a mineral

Question 7

Petrification (Altered Remains)

Answer 7

The tissue of a fossil is replaced by a new mineral, for example, silicified, or petrified (pores within the woody tissue are permineralized)

Question 8

Carbonization (Altered Remains)

Answer 8

Volatile such as water are removed through heat and compaction, leaving a thin carbon film

Question 9

Molds (Indirect Preservation)

Answer 9

If the organism is stamped into the sediment and the sediment and the sediment is subsequently lithified, an external mold is produced (Trackways are external molds of feet)
If the interior of an organism such as a shell dissolves away, an internal mold is produced

Question 10

Cast (indirect Preservation)

Answer 10

If an external mold later becomes filled with sediment/minerals, an exact replica, or cast, of the original fossil is made. Molds are negatives and casts are positives

Question 11

Burrows and Borings

Answer 11

Many animals excavate burrows in soft sediment. Some bore holes into solid rock, wood, or shells. These structures are often tubular and horizontal (for deposit feeding or dwelling)

Question 12

Resting traces

Answer 12

When an animal stops moving for a short while (either for rest or protection), they produce a shallow impression or mold on the sediment surface that may record their shape or morphology

Question 13

Trackways, Trails, and Footprints

Answer 13

Many animals travel across soft sediment surfaces. Evidence of their passage is often preserved as molds on top of beds or as casts on the bottoms of overlying beds. Many trails are formed by organisms that are surface feeding or grazing

Question 14

Coprolites (Fossil Excrement) and Gastroliths (Gut area of Skeleton)

Answer 14

Coprolite is a term applied to fossil excrement. Gasthroliths are only positively identifiable if they are found in the gut area of a skeleton; they are rounded stomach stones used for grinding down food after it is swallowed