Name:

point ann north outcrop (WS144)

County:

clayton

Company:

mcgregor, city of

IDALS Reg. #:

not applicable

IDOT Code #

not applicable

Loc. (Q's):

se se se

Sec.

22

T.

95n

R.

3w

Quad:

prairie du chien (E45)

Elevation:

630 ft. at road level (base of section)

Loc. Rmrks:

Outcrop on west side of road, at north end of the Point Ann ridge.

Descrip. By:

Robert M. McKay

Date(s):

5/11/1995&10/22/97

Descrip. Rmrks:

Section measured and numbered from base upwards. Section begins at road level approx. 200 feet south of grain elevator/barge loading facility. TFA = tangential foreset dip azimuth; TAA = trough axis dip azimuth; PFA = planar xs foreset azimuth

Previous Descrips. & Other Remarks:

Same location as WS144 outcrop description by W.S. Schuldt, (1940) University of Iowa M.S. thesis

Unit	Description	ft.	m.
	Units 1 through 8 appear from road level as one massive, very thick bedded unit.
1	Sandstone, f-c, minor vc as quartz and tan silty dolomitic lithoclasts, massive on outcrop, outcrop moderatly lichen covered, internally highly cross-stratified, abundant trough cross-strata, sets highly truncated and range in thickness from 10-60 cm; xs in lower 2 m, TFA=185, 186, 199; TAA=241, 259; from 2-4 m TFA=141, 113, 232, 170, 189, 196; small bedding break at 5 m.	16.4 ft	5.0 m
2	Sandstone, f-c, minor vc quartz, intraclastic, intraclasts are 1-3mm tan dolomitic siltstone, one thick bed with no discernible stratification	1.31 ft	0.4 m
3	Sandstone, f-c, trace vc, quartzose, faint small-scale cross-stratification	0.49 ft	0.15 m
4	Sandstone, f-vc, quartzose, highly intraclastic, intraclasts 1-3mm tan dolomitic siltstone clasts, one medium bed with no discernible stratification	0.89 ft	0.27 m
5	Sandstone, f-c, trace vc, quartzose, moderately intraclastic with majority of intraclasts similar to below but basal 5 cm contains 1 by 8 cm flat pebble intraclasts with internal horizontal-planar laminations, unit displays horizontal stratification in poorly defined sets up to 5 cm thick, at 65 cm above base is a 3 mm round quartz pebble	3.02 ft	0.92 m
6	Sandstone, similar to unit 5 but with minor tabular cross-sets in upper part, PFA=314	1.12 ft	0.34 m
7	Sandstone, f-c, quartzose, moderatly intraclastic, numerous sets 5-10 cm thick of horizontal to low-angle planar in lower part, and low angle troughs in upper part; upper 28 cm contains sandy siltstone flat pebble intraclasts to a maximum size of 1 by 6 cm. Top of unit marked a discontinous zone of vertical Skolithos burrows which extend down from a laterally discontinous 2 cm thick green silty, clayey sandstone	3.21 ft	0.98 m
	Offset measurements to the south approximately 30 m and up talus slope to continue the section
8	Sandstone, m-vc, quartzose, trace granules (quartzite) up to 4mm diameter, cross-stratified to horizontally stratified, sets up to 8 cm thick with low-angle foresets. Contains common dolomitic siltstone - very fine grained sandstone flat pebble intraclasts that are <1 cm to 7 cm in diameter by 0.5 cm thick.	0.98 ft	0.30 m
9	Sandstone, appears as a distinctive slightly recessive, thin bedded unit with distinct light tan color from unit below; dominantly silt & vf-f with approximately 30% m-c interstratified lenses & laminae, rippled & flasered-bedded with tan to light green laminated silty clay flasers and drapes to 1 cm thick, and discontinuous wavy to less well-developed silty/clayey/dolomitic flasers. Upper 10 cm tends to be horizontally to wavy laminated with same grain size distribution. Upper contact is very sharp and erosional.	2.07	0.63 m
10	Sandstone, m-c, vc, intraclastic; lower half is one tabular planar set up to 35 cm thick with erosionally scoured base with up to 10 cm relief, highly intraclastic in lower foresets with tan silty to vf sdy fpi to 8 cm; PFA= 22,15,75,35. Upper half consists of 2-3 sets 10-20 cm thick of planar to low angle tangential (probable truncated trough sets) xstrata; TFA=38,75,43 (dips of 27,13,25).	2.89 ft	0.88 m
11	Skiped in numbering
12	Sandstone, interbedded cross stratified lenses & bioturbated beds; maximum lense length is 2.0 m. 12a (10cm) vf, minor f-m, moderately bioturbated. 12b (10 cm) f-m, lense with planar cross strata, lenses pinchout and/or thin laterally to thin 1-2 cm thick sand zones; lenses are often but not always overlain or draped by 0-2 cm thick layers of well laminated silt-vf ss. 12c (10-15 cm) vf-f, minor scattered m-c, moderately bioturbated with Skolithos (sample PAN 12). 12d (4-5 cm) silt-vf, horizontal to wavy laminated over unit below. 12e (15-16 cm) vf-f, minor scattered m-c, moderately bioturbated with Skolithos. 12f (2-12 cm) f-m, minor c, lenticular planar xs with planar foreset consistently to se-sw, PFA=215,141,157,190; occasional silt-vf ss fpi in lenses. 12g (4-10 cm) thin interbeds of horizontally laminated silt-vf ss, bioturbated vf-f ss and 1-2cm thick lenses of f-m (minor c) xs. 12h (0-6 cm) f-m, lensatic.	2.43 ft	0.74 m
13	Sandstone, thin interbeds of vf-f and f-c, horizontally laminated in part and moderately bioturbated in part that grade laterally to cross-strata. 13a (27-30 cm) lower 12 cm is xs sandstone, m grn, minor coarse, one set of tangential xs that pinches out laterally TFA=115, intraclastic with common silt to f dolomitic ss fpi from 0.5-4 cm, and lessor fpi up to 1 cm thick and 50 cm long, gradational into the upper 18 cm which is moderately Skolithos bioturbated very sandy dolomite to dolomitic sandstone , laterally continous (sample). 13b (16-27 cm) Sandstone, f-c, minor vc and one felsite well-rounded pebble to 4.5 mm, dolomitic to very dolomitic, and intraclastic with dolomitic fpi tp 2 cm, displays faint trough xs with sets to 12 cm thick and up to 30 cm wide; locally 13b thickens to 27 cm and contains two cycles of fpg grading up to m-vc lenticular xs ss in troughs with set thickness 3-10 cm (sample). Laterally 13b becomes much less distinct and the overlying unit 13c appears to thicken to the south. 13c (13 cm) Sandstone f-c, minor vc, horizontal-wavy laminated with common and distinctive discontinuous tan silty laminae, laminae up to 1 mm thick and 10-15 cm in length, sparsely intraclastic in basal 5 cm.	2.0 ft	0.61 m
14	Dolomite, lower 25-30 cm is a dolomitic ss with common silty-sandy dolomite fpi and sand matrix of m-vc, displays discoidal vugs from intraclast weathering; grades upward to distinctive dolomite, vf xtln, vf-c sandy, quartzose, appears as slightly recessive, pink dolomite that is separated into 3 to 4 subbeds with the lowest subbed being the thickest, no visible primary sedimentary structures; sharp upper contact (sample).	1.97 ft	0.6 m
15	Sandstone, f-c, one thick unit but internally consists of sets 4-10 cm thick of small-scale (probable) trough xs, sets are discontinuous laterally, middle portion contains numerous light tan, thin-flake clay intraclasts 1-5 cm in length (channel sample grain size), TFA=43, 107, 119, 240.	3.48 ft	1.06 m
16	Sandstone, vf-m, minor c, intraclastic with siltstone to vf sandstone fpi up to 5 cm in diameter, stratification is horizontal-wavy and discontinuos	0.89 ft	0.27 m
	Additional Section
	This short section measured on 11/07/94. Was looking for contact between coarse-grained Van Oser facies and finer-grained facies above. The section begins about 1-2 m below top of telephone pole. Measured from bottom up.
1a	Sandstone, light grey on weathered surface, thick to very thick bedded appearance, fine-coarse, minor vc, rounded, very weakly cemented, white-brownish on fresh surface, very porous, vertical east -west joints, local dolomitic cemented zones. Upper 60 cm contains common dolomitic and silty sandstone intraclasts which are generally flat pebble and less than 1 cm to 7 cm in diameter by 0.5 cm thick. Followed by transition zone into overlying facies.
1b	Sandstone, fine-coarse, sm-sc-xs sets 0.5-1.0 cm sets, flasered with green clay flasers up to 1mm thick; very thin to thin bedded; unit is poorly sorted; sharp upper contact, recessive - generally covered.		0.08 m
2a	Sandstone, fine - medium, minor coarse, intraclastic with tan dolomitic siltstone flat pebble clasts 0.5 - 4.0 cm diameter. Also some tan dolomitic sandy siltstone matrix filling Skolithos burrows. This unit is the lower and poorly exposed half of one ledge-forming bed. Sample 2a (this sample has some green shale on the base from the underlying 1b interval).		0.14 m
2b	Dolomite, light grey, fine - coarse sandy, intraclastic with tan silty flat pebble clasts. This is the upper one half to two thirds of a ledge-forming unit which overall appears to vary in thickness between 30-33 cm. Sample 2b		0.15-0.20 m
2c	Dolomite, light grey, no internal fabric, vf-f xtln, silty to fine quartz sandy, rare m-c quartz sand, hard, well cemented. Sample 2c		0.08-0.10 m
2d	Sandstone, tan, vf-f, dolomitic, bioturbated. Sample 2d		0.05-0.06 m
2e	Dolomite, tan, silty to vf-f sandy, bioturbated		0.01 m
	Notes – examining section from a distance at road level it is apparent that there is a thinner bedded unit of approximately 2 meters that intervenes between the more massive bedded sandstones below and the base of unit 2. Unit 1 of the above section may be part of this thin bedded unit.