UNIT 12 The history of the Earth Biology and Geology 4. Secondary Education TYPES OF STRATIGRAPHIC DISCONTINUITIES

UNIT 3 Biology and Geology 4. Secondary Education UNIT 12 Types of stratigraphic discontinuities Stratigraphic discontinuity is the absence of the stratigraphic record for a specific period. There is a geologic time interval in the Earth's history, between two sequences separated by a discontinuity, that is not represented by sediments. There are many types of discontinuities:

UNIT 3 Biology and Geology 4. Secondary Education UNIT 12 Types of stratigraphic discontinuities ANGULAR UNCONFORMITY Discontinuity between an older stratigraphic series which folded and eroded when the strata were exposed to the weather and a more recent stratigraphic series. Young horizontal series Old folded series

UNIT 3 Biology and Geology 4. Secondary Education UNIT 12 Types of stratigraphic discontinuities DISCONFORMITY Discontinuity between an old stratigraphic series which underwent a period of erosion and the more recent stratigraphic series which was deposited after that process. Series deposited after the erosion of the previous series

UNIT 3 Biology and Geology 4. Secondary Education UNIT 12 Types of stratigraphic discontinuities NONCONFORMITY Discontinuity between an old series consisting of eroded rocks (e.g., granite) and the more recent sedimentary strata. Young sedimented series Old eroded granite

UNIT 3 Biology and Geology 4. Secondary Education UNIT 12 Types of stratigraphic discontinuities PARACONFORMITY Discontinuity between an old series deposited many millions of years ago, after which there was an interruption in sedimentation over millions of years, and the more recent stratigraphic series. Recently deposited young series Interruption in sedimentation over several million years Old series deposited millions of years ago.