?

?

?

?

? ? ? ?

?

?

? ?

?

Figure 3. Lacunae (lined pattern) in Upper 

Cretaceous formations in eastern Wyoming, 

central Colorado, and northeastern New Mexico 

with informal fossil zone numbers and radiometric 

ages. m.y., millions of years.

Greenhorn 

Limestone

UPPER CRETACEOUS

Turonian

SERIES

Stages

Informal substages

Radiometric 

ages (m.y.)

Santonian Coniacian

Lower Upper Middle Lower Upper Middle

Informal zone nos.

33

31

29

28

44

43

39

38

42

41

37

36

35

34

32

30

27

Lower

26

25

24

23

Upper

Cenomanian 

22

21

20

19

18

17

16

15

14

13

12

11 

10 

 9

Middle

90.60

0.39

0.59

0.46

93.19 0.42

93.99 0.57

40

Lower

 (Gap in 

biostratigraphic 

 record)

 8

 7

 6

93.82 0.30

99.6 0.9 

98.88 

 0.35 

1

2

3

4

5

45

Middle Upper

46

47

48

0.34 49

50

Campanian

Lower

51

0.36 52

Middle

53

54

55

 80.58 0.55 56

57

58

59

60

61

62

 75.77 0.34 63

64

65

66

67

 73.52 0.39 

 71.98 0.31 

68

69

70

71

72

73

 70.00 0.45 74

Upper

Maastrichtian

Lower Upper

 69.59 0.36 75

76

77

78

65.50 0.10

 74.74 0.23

 75.05 0.32

 75.95 0.41

 81.86 

 NW 

Black 

 Hills

 Fox Hills 

Sandstone

?

 Lance 

Formation

Pierre Shale

 (part)

Pierre Shale

 (part)

Pierre Shale

 (part)

 Niobrara 

Formation

?

?

Carlile 

Shale 

(part)

Carlile 

Shale 

(part)

Greenhorn 

Formation

 Belle 

Fourche 

 Shale

Mowry 

 Shale 

?

Red Bird

?

 Lance 

Formation

 Fox Hills 

Sandstone

?

Pierre Shale

 (part)

Pierre Shale

 (part)

Pierre Shale

 (part)

 Niobrara 

Formation

Greenhorn 

Formation

 (part)

Carlile 

Shale 

(part)

Carlile Shale 

(part)

Greenhorn 

Formation 

 (part)

?

Mowry 

 Shale 

 Belle 

Fourche 

 Shale

Rock River

?

 Fox Hills 

Sandstone

 Medicine 

 Bow 

Formation

Lewis Shale

Pine Ridge 

Sandstone

Rock River 

Formation

Steele 

Shale

?

 Niobrara 

Formation

Sage Breaks 

 Shale 

 Frontier 

Formation 

 (part)

?

 Frontier 

Formation 

 (part)

Mowry 

 Shale 

Buckeye

?

 Fox Hills 

Sandstone

Pierre 

Shale

(part)

?

 Niobrara 

Formation

Pierre Shale

 (part)

Greenhorn 

Limestone

 (part)

Greenhorn 

Limestone

 (part)

?

Mowry 

 Shale 

Graneros 

 Shale 

 Kassler/

Littleton 

 area

?

Dakota 

 Group 

?

?

 Fox Hills 

Sandstone

 Laramie 

Formation

Pierre 

Shale

 Niobrara 

Formation

Carlile Shale 

 (part)

Graneros 

 Shale 

Pueblo 

 area

?

?

 Fox Hills 

Sandstone

 Laramie 

Formation

Pierre 

Shale

 Niobrara 

Formation 

 (part)

Carlile Shale 

 (part)

Carlile Shale 

 (part)

Greenhorn 

Limestone

?

 Dakota 

Sandstone 

Springer 

 area

?

?

 Trinidad 

Sandstone

 Raton

Formation

(part) and

 Vermejo 

Formation,

undivided 

Pierre 

Shale

 Greenhorn 

 Limestone

 (part)

Carlile Shale 

 (part)

Carlile Shale 

 (part)

Greenhorn 

Limestone

 (part)

?

Graneros 

 Shale 

Graneros 

 Shale 

 Dakota 

Sandstone 

Informal zone nos.

33

31

29

28

44

43

39

38

42

41

37

36

35

34

32

30

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11 

10 

 9

40

 8

 7

 6

1

2

3

4

5

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

?

Carlile Shale 

?

95.73 0.51

94.96 0.50

94.71 0.49

92.46 0.58

93.48 0.58

?

Trinidad/

 Aguilar 

 area 

 Dakota 

Sandstone 

?

Graneros 

 Shale 

Greenhorn 

Limestone

 (part)

Greenhorn 

Limestone

 (part)

Carlile Shale 

 (part)

Carlile Shale 

 (part)

?

 Niobrara 

Formation

Pierre Shale

 (part)

Pierre Shale

 (part)

?

?

 Trinidad 

Sandstone

 Raton Fm.

 (part) and

Vermejo Fm.,

 undivided 

 Niobrara 

Formation 

 (part)

 Nb. Fm. (part)

 Niobrara 

Formation 

 (part)

 Niobrara 

Formation 

 (part)

K-T boundary =

93.32 0.38

Carlile Shale 

 (part)