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debate (see review in Petty, 2019a), with Formation. Most “false Bakken” designa- (Meissner, 1978; Webster, 1984). Onlap is
66% of studies (61 out of 93) supporting tions refer to the basinal facies of the lower best displayed on the eastern to southern
deep-water Bakken deposition versus 34% Virden subinterval, which lies a few meters basin-flank (Fig. 1) where stable cratonic
of studies (32 out of 93) supporting shallow- above the top-Bakken in the basin-center, conditions persisted. Bakken deposition
water Bakken deposition. The debate contin- and this unit will be the focus of the was followed by a major sea-level rise that
ues, with Hart and Hofmann (2020) and Lodgepole study. To date, all studies (seven formed the 2nd-order maximum flooding
Egenhoff and Fishman (2020) advocating total) that offer an opinion on the origin of surface (Fig. 2) and flooded western North
for deep-water Bakken black shale deposi- the organic-rich facies of the lower Virden America, resulting in widespread epeiric
tion and Petty (2019a, 2021) advocating for conclude that it formed in a deep-water set- conditions during early highstand deposi-
shallow-water Bakken black shale deposi- ting. As discussed below, this unit displays tion of lower Lodgepole sediments (Petty,
tion. Although paleontology, geochemistry, a dramatically different stratigraphic geom- 2019a, 2019b).
and worldwide-event studies contribute to etry from the Bakken Formation, and this
this discussion, the essence of the argument contrast may offer evidence in the deep- LITHOSTRATIGRAPHIC UNITS
is a sedimentology versus stratigraphy water versus shallow-water debate. Bakken lithostratigraphic descriptions
debate, with conventional sedimentology are from wells in Figures 3 and 4, with min-
interpretations (e.g., fine grain size, clay con- STRATIGRAPHIC SETTING eralogy from Petty (2019a, table 1). The
tent, laminations) suggesting deep-water The Madison 2nd-order sequence within formation and member nomenclature of
deposition while stratigraphic observations the Williston basin was defined by Petty LeFever et al. (2011) is used for Bakken
(e.g., onlap onto subaerial unconformity and (2006), who placed the Bakken Formation Formation units (Fig. 2). The gamma-ray
lack of landward-equivalent shallow-water in the transgressive systems tract and the character for lithostratigraphic units is illus-
strata) indicate shallow-water deposition. Lodgepole Formation in the highstand sys- trated with type logs in Figure 5. Pronghorn
Recent studies suggest that sedimentology tems tract (Fig. 2). Bakken strata lie on the Member sediments were deposited on the
attributes are not unequivocal indicators of Acadian unconformity (Fig. 2), which is Acadian unconformity in local depocenters
deep-water mud deposition (Schieber, 2016); characterized by sub-unconformity weath- with compositions reflecting erosion from
thus, the stratigraphic geometry may be the ering near the basin-center (Bottjer et al., local sources. Above the Pronghorn, all
ultimate arbitrator. 2011) and extensive stratal truncation with Bakken lithostratigraphic units can be corre-
Although the Bakken Formation has been deep sub-unconformity, paleokarst diagen- lated from the basin-center to the landward
intensely studied, overlying stratigraphic esis in basin-margin areas (Petty, 2017, Bakken limit (Fig. 3). The Lower Member
units have received less attention. The term 2019a). The lower, middle, and upper mem- consists dominantly of black, faintly lami-
“false Bakken” has been applied to lower bers of the Bakken Formation display a nated to massive, organic-rich (7%–25%
Lodgepole stratigraphic units or lithologies regional onlap pattern defined by younger TOC from LeFever, 2008), high gamma-ray
that superficially resemble organic-rich stratal units extending progressively farther (250–1200 American Petroleum Institute
shale units in the underlying Bakken landward than underlying stratal units [API] units), argillaceous (35% clay minerals),

Figure 2. Stratigraphic column for the Bakken Formation and basal portion of the Lodgepole Formation. Arg.—argillaceous;
Dol.—dolostone; Ls.—limestone; Sst.—sandstone; Sltst.—siltstone; HST—highstand systems tract; TST—transgressive systems tract.

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