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The Dakota Sandstone: a transgressive shallow marine system of the San Rafael Swell region, Utah, U.S.A.

Authors:
The Dakota Sandstone: a transgressive shallow
marine system of the San Rafael Swell region,
Utah, U.S.A.
Stephen Phillips, John Howell, Adrian Hartley – University of
Aberdeen
Outline






Motivation
 
Parcularly dal ones in a basin scale transgression
!"

The Dakota Sandstone has been interpreted as a uvially dominated incised valley-ll (Kirschbaum and Schenk,
2010)
We show that it is actually dominated by dal deposits
Transgressive systems are important subsurface reservoirs!
#$$!$%
"&&'&(
)! !(
Field Area – San Rafael Swell, Utah, USA
#&*
+

&

Dakota Sandstone Facies Associations – Tidally In%uenced Fluvial Channel
 ,$!
!
#!
' ,!-./
!!0..12%3
' ,4

5

 !"
# !$%%
 !$%%
Dakota Sandstone Facies Associations – Tidal Channel: Sigmoidal Barform
5 
6-78
 ,
& ,
' ,$
#
!
'!
!
&'()
"*
 !$%%
+
 !$%%
&'()
,-
*+$!.
$**
Dakota Sandstone Facies Associations – Tidal Channel: Compound Dune Barform
 ,
! ,
!

#

/
0/
 !
Dakota Sandstone Facies Associations – Mud and Sand Flat
!

&
!!!
'
#

!
!!)&
 12 +. 
+)
Dakota Sandstone Facies Associations – Tidal Point Bar and Marine Shoreface
.3%
#4+3%



Dakota Sandstone Facies Associations – Tidal Point Bar
#4+3%
,
9

'!!
!!


$
&


:

+) +) /
Dakota Sandstone Facies Associations – Marine Shoreface
.3%
,;
Henry Mountains Basin
Mussentuchit Wash
6 ,


Shell material is always disarculated and fragmented
5!
Sandstones are commonly both fossiliferous and
bioturbated
Ophiomorpha and diplocraterion
<" ,

# !$%% /+5 )+) &
Dakota Sandstone Facies Associations – Coastal Plain
5!
'
!!!

 ,

:2=


!! % 
!!!
Dakota Sandstone Facies Associations – Transgressive
Ravinement
*
!64
;
Only shells in a mudstone matrix
...or a mix of shells and pebbles in a mudstone or
sandstone matrix
...or only pebbles in a mudstone matrix
"
>$
!


 !
!. 0$#
73 **

6
Architecture – Henry Mountains Basin
" #6
"8
Architecture – Western San Rafael Swell
" #6
"8
Architecture – Western San Rafael Swell
Depositional Model
>

0!$?7-@3
!4 +. !/+.
# 
6
#4+
.
!7 13
Depositional Model
9!::-
&
:$6&
5"!>&
&
:%
">
%
+!
!

Pre-Laramide
Forebulge
&'&;
Tidally dominated
Tidal deposits as a whole are
very laterally connuous, but
sand bodies are very
heterolithic
Average 9m thick
)5;
Fluvial-dal-shoreface
Very laterally extensive
shoreface sandstone
Up to 40m thick (Ana and
Fielding, 2011)
;
;
;<# 5 &2
Conclusions
"&)5&'&

!!!!
!;
Transgressive ravinement
Shoreface
Tidal point bar, mud/sand ats, and mire/peat swamp
Tidal channel
Tidally inuenced uvial
""&
!$
!$

"&
 $
"!
References
$A.$$.'.$?7--$&9 ;
<6"&$)$6;
+:$5.B/$.C-D CC@.
!!$#..$$E..$$..$!$A..$-BBC$&
6&$$..$+$A..$F"$G.A.$F
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