Explanation chart
5.3 Spatial and temporal facies characteristics: 3-dimensional facies correlation correlation
5.3 Spatial and temporal facies characteristics: 3-dimensional facies
It is obvious, from the 2-dimensional transections and facies maps that each sedimentary cycle is characterized by an individual distribution of facies types, lithology and thickness pattern. A persisting facies domain and paleotectonic element is the Williston Basin in all sedimentary cycles.
The sedimentary cycle C I is basinwide traceable and correlative (see Figure 5-16). The spatial extent and stratal preservation are strongly controlled by the bounding J-2 unconformity. The facies distribution and facies models for the sedimentary cycle C I describe shallow subtidal to peritidal depositional environments. A homogenous supratidal to peritidal red bed facies is unconformably interrupted by thin, but widespread peritidal to shallow subtidal carbonate beds that indicate repeated advance of marine conditions into the depositional settings. Depositional settings are described by toward each other oriented homoclinal ramps as schematically shown in Figure 5-16. In marginal and poorly exposed portions of the “Sundance Basin” the facies of the First Marine Cycle (C I) is labeled as undivided.
The facies distribution and facies model for the sedimentary cycle C II reveal sedimentation of peritidal red beds and shallow subtidal carbonate beds of the Piper Formation in the Williston Basin and northwestern Wyoming. The spatial extent and stratal preservation of the sedimentary cycle are strongly controlled by the J-2a unconformity and the stratal onlap onto paleotopographic elements like the “Black Mountain High” in Wyoming (see Figure 5-17). Like in the preceding cycle C I a homogenous supratidal to peritidal red bed facies in northwestern Wyoming is unconformably interrupted by thin, but widespread peritidal to shallow subtidal carbonate beds that indicate repeated advance of marine conditions into the depositional settings. These facies shifts occur frequently in the Piper Formation, while facies contrasts in the Sawtooth Formation are slight in Montana.
Depositional settings of the sedimentary cycle C II in southwestern Wyoming and eastern Idaho are described by a ramp morphology with distally steepened gradients toward the
“Utah-Idaho trough” as schematically shown in Figure 5-17. With onset of the Second Marine Cycle (C II) the facies domain of the “Utah-Idaho trough” evolved and shallow to normal marine carbonates of the Twin Creek Limestone were deposited. The spatial facies relations are recorded by wide, more or less east-west oriented and north-south trending facies belts that range from supratidal distally into subtidal environments.
During deposition of the sedimentary cycle C III (see Figure 5-18), particular facies domains like the carbonate facies realm of the “Utah-Idaho trough”, the mixed carbonate-siliciclastic facies of the “Belt Island Complex”, the fine clastic sediments of the Williston Basin, and the mixed carbonate-siliciclastic facies realm of the “Wyoming shelf” were constituted. The facies distribution and facies model for the cycle C III reveal a differentiation between shallow and normal marine siliciclastic and mixed carbonate-siliciclastic facies types of the Sundance Formation in the eastern “Sundance Basin” and marine carbonate facies types of the Twin Creek Limestone in the “Utah-Idaho trough”
and the Rierdon Formation on the south flank of the “Belt Island Complex” (see Figure 5-18). In the distal portion of a steepened ramp shallow to normal marine
carbonates of the Twin Creek Limestone were deposited. Carbonate sedimentation in the
“Utah-Idaho trough” was finally surpressed with the progradation of thick red bed successions of the Preuss Formation during the Third Marine Cycle (C III). Deposition of the siliciclastic dominated Sundance Formation occurred in the proximal portion.
cro ss-bed
ded , eo
lian Page
Sa nd
stone
~ 50m
distally steepened ramp
Rampmorphology
Approximate extend of
“Sundance Basin” according to paleogeographic maps of IMLAY (1980)
emerged area emerged area
position of transections emerged area
bounding J-2 unconformity
Figure 5-17: 3-dimensional facies correlation for the Second Marine Cycle (C II). For color code of facies types see Figure 5-1. For full names and position of sections see Figures 1-1 and 1-2.
The facies distribution and the facies model for the cycle C IV describe depositional environments of a homoclinal ramp and normal marine to intertidal sedimentation of glauconitic fine- to coarse-grained successions (see Figure 5-19). The stratal preservation is strongly controlled by the bounding unconformities J-4a and J-5. The spatial distribution
and the evolution of facies types is monotonous. Facies shifts are very minor. Distinct facies domains like the “Utah-Idaho trough” can no longer be identified in contrast to conditions found in the preceding sedimentary cycles. In addition, the “Sundance Basin”
regained its symmetric geometry. As also shown in the facies maps for this interval only the Williston Basin presents a facies domain in which fine siliciclastic material was
~50 m AR
MIN SPC
SWC
HU TR
#BAR SBC HR
FH HY
#CD HE
RL LW
BE
FG SR
SC
TF LB
V THI
?
intertidal &
supratidal Preuss facies II
prodeltaic Preuss facies I
prodeltaic Preuss facies I intertidal &
supratidal Preuss facies II
distally steepened ramp
Ramp morphologyposition of transections position of transections
emerged area
Approximate extend of
“Sundance Basin” according to paleogeographic maps of IMLAY (1980)
emerged area
position of bounding unconformities
SRC
SAP RC
W
Figure 5-18: 3-dimensional facies correlation for the Third Marine Cycle (C III). The “unnamed cycle” is not displayed. For color code of facies types see Figure 5-1. For full names and position of sections see Figures 1-1 and 1-2.
deposited. The most obvious facies shifts are recorded where coarse-grained sandstones are transported via the bordering Alberta and Saskatchewan shelfs into the basin. The glauconitic sandstones grade toward the Williston Basin into glauconitic siltstones and shales.
RC
AR
MIN
SPC SWC
GR HU
#BBD HY
HR
FH CD
HE
V
#DR
homoclinal ramp
homoclinal ramp Ramp
morphology emerged area
Approximate extend of
“Sundance Basin” according to paleogeographic maps of IMLAY (1980)
emerged area
position of transections position of transections
position of bounding unconformities clastic transport
SR SRC
LW
SAP
BE
FG
~50 m
Figure 5-19: 3-dimensional facies correlation for the Fourth Marine Cycle (C IV). For color code of facies types see Figure 5-1. For full names and position of sections see Figures 1-1 and 1-2.