North Dakota Geological Survey Edward C. Murphy, State Geologist Geologic Investigations No. 59 Lynn D. Helms, Director Dept. of Mineral Reources Bakken Formation Map Series: Sheet 1 2008 Isopach of the Bakken Formation Julie A. LeFever

o 104 o o R 102 W R 100 W 103 o o 49 R 98 W R 96 W o o o 98 R 52 W o R 94 W R 92 W 102 99 R 58 W R 56 W R 54 W R 90 W R 88 W R 86 W 101 100 R 62 W R 60 W 49 R 84 W R 82 W R 78 W R 76 W R 74 W R 70 W R 68 W R 66 W 50

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0 100 INTRODUCTION T 162 N T 162 N A series of five regional maps have been constructed for the Bakken Formation 0 including an overall isopach of the Bakken Formation, individual isopachs for each of T 160 N T 160 N the three members, and a structure map on the top of the formation. These maps are based on 4,260 data points scattered throughout the North Dakota side of the Williston

5 0 0 basin. T 158 N T 158 N ISOPACH OF THE BAKKEN FORMATION

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T 156 N T 156 N The Bakken Formation is present only in the subsurface of the Williston basin and 5 1 0 0 extends over approximately two-thirds of the State of North Dakota (see Map). The 0

0 1 0 5

1 formation consists of three members, two black, fissile shales separated by a mixed 0 0

5 sequence of siliciclastics and carbonates (see Typical Log). The formation overlies the T 154 N T 154 N 0 Three Forks Formation (Devonian) and is overlain by the Lodgepole Formation 0 1 (Mississippian). o 48 o 48 The formation attains a maximum thickness of 160 ft (49 m) and has a well-defined depocenter just east of the Nesson Anticline (western Mountrail County). A smaller north-south trending sub-basin occurs on the eastern edge of the Bakken in Bottineau T 150 N T 150 N and McHenry counties. Anomalous formation thicknesses also occur in the area of the Lodgepole Dickinson mounds in Stark County. The southeastern extension of the formation is probably due in part to a shift in the depositional shoreline related to

T 148 N T 148 N movement along the Heart River and Antelope fault zones.

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T 146 N T 146 N

T 144 N T 144 N

T 142 N T 142 N

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o 47 47o 0 Contour T 140 N T 140 N Interval

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T 138 N T 138 N 10 20

30 0 40 T 136 N 0 T 136 N 50 60 70 T 134 N T 134 N 80

90 100

T 132 N T 132 N 110 120 130 140 T 130 N T 130 N 150 o 46 46o 160 Typical Log

o R 104 W R 102 W R 100 W R 48 W 104 R 96 W R 52 W o R 94 W R 92 W R 56 W R 54 W o R 88 W R 86 W R 60 W 103 o R 84 W R 80 W R 78 W R 76 W R 72 W R 70 W R 68 W R 64 W R 62 W o 97 102 o o o 101 100 99 98

Explanation Scale 1:1,000,000

0 20 40 60 80

Thickness of the Bakken Formation (in feet) Miles

Township Boundaries 0 20 40 60 80

County Boundaries Kilometers North American Datum 1927 Lambert Conformal Conic µ