Petrology and Sedimentation of the Upper Precambrian Sioux Quartzite
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PETROLOGY AND SEDIMENTATION OF THE UPPER PRECAMBRIAN SIOUX QUARTZITE MINNESOTA, SOUTH DAKOTA AND IOWA A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY RICHARD ELMO WEBER IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE MARCH 1,1981 Frontispiece--PALISADES OF SIOUX QUARTZITE SPLIT ROCK CREEK NEAR GAJ.(RETSON, SOUTH DAKOTA i ABSTRACT The Upper Precambrian Sioux Quartzite is exposed at several locations along an east-west trend 17 5 miles long and 30 miles wide between Mitchell, South Dakota and New Ulm, Minnesota. It rests unconformably on Lower Precambrian rocks and is overlain by Cretaceous strata and Pleistocene drift. A coarse basal con- glomerate is exposed near New Ulm a short distance from the underlying granite. but contains no granitic cl:1,3ts . Quartzite is gently folded. It is intruded by diabase at Corson, South Dakota. The formation consists of over 1600 meters of o:-thoquartzite sandstone with minor interbedded quartzose conglomerate and stone. Conglomeratic units are present in the lower two-thirds 0£ the section .:!nd minor th.in mudstone.s occur in the up;:ier third. The compositionally and texturally supermature orthoquartzite is composed almost exclusively of well rounded, well sorted 1 mcno- crystalline quartz. Detrital chert and iron formation grains are present in some samples. Polycrystalline quartz is abundant cnly near New Ulm, Minnesota, wher-e it was derived from the underlying granite. In all other parts of the Sioux it makes up only 2 small percent of the total detrital grains. No feldspar is present in any of th2 109 thin sections examined. The mean grain size of the samples studied ranged from fine sand to coarse sand but most were medium sand. The grains are coated with a thin film of iron oxide and cemented by quartz overgrowths. In a few samples the overgrowths are partially ii replaced by sericite. Multicycle grains with abraded quartz overgrowths beneath the present cement were found in 84 percent of the orthoquartzite thin sections. Rounded zircon and tourmaline are the only common nonopaque detrital heavy minerals. Two types of conglomeratic rocks are present, coarse basal conglomerate and conglomeratic orthoquartzi te. The basal con- glomerate consists of clasts, as much as 35 centi:n2ters in diameter of vein quartz, hematitic chert, iron formation and quartzite. Clasts of rhyolite were found in one outcrop of basal conglomerate. The conglomeratic orthoquartzi te consists of 1 to 10 centimeter layers of pebbles interbedded with cross-bedded coarse orthoquartzite. The m.udsr.ones within the Sioux are red to dark purple in color. Most are blocky but some show fissility. 'I'h·2 muds tones range from almost pure claystones to silty rnudstone and are composed of sericite, quartz, he1rlatite and ill:f.te. Trough cross-bedding, symmetrical ripple marks, current ripple marks and mudcracks are the major sedimentary structures. Less common struc tu.res include sand waves, planar cross-·bedding, load casts, mud clasts, parting lineation and climbing ripp• 1... e lamination. The cross-bedding consists predominantly of narrow troughs 60 to 140 centimeters wide and 15 to 30 centimeters thick. Symmetrical ripple m.?.rks with wave lengths of 2 to 4 centimet2rs and of 4 centimeters are present throughout the forme- tion. Asymmetrical current ripples are the most common ripple type. They have an average length of 8.2 centimeters and an amplitude of 2.5 centimeters. Herringbone cross bedding and iii reactivation surfaces, sedimentary strucrures charact eristic of tidal sedimentations are found only in the upper third of the section. Measurements of 1156 cross-beds with a vector mean of 162 degrees show a paleocurrent direction to the southeast. No major vertical or lateral changes in trends were observed. The analysis of 491 ripple marks also indicate a southeast paleoslope. Paleocurrent patterns are unimodal throughout most of the unit but some bipolar patterns occ.ur in the upper part of the formation. The Sioux is a multi-cycle sediment derived f rom a highly weathered low relief source area in which quartz sands tone and iron formations were the dominant lithologies. The upper third of the formation is interpreted as having been deposited in a shallow marine intertidal environment. The lower two-thirds of the section may have been deposited in e i ther braided fluvial environment or a hig h energy shallow marine environment. TABLE OF CONTENTS ABSTRACT ..... i TABLE OF CONTENTS iv TABLES. vi FIGURES . vii INTRODUCTION •. Acknowledgements • 3 AREAS OF OUTCROPS . 4 New Ulm, Minnesota Area. 6 Jeffers, Minnesota Area. • . ... 6 Southwest Minnesota and Eastern S0uth Dakota 6 AGE AND CORRELATIONS. 8 METHODS OF 13 Field Work ., ".) Laboratory Work •. ..L_i REGIONAL GEOLOGY. • 15 PREVIOUS WORK 18 STRUCTURE • • Bedding Attitudes .• 23 Initial Dip. 23 Faulting 28 Joints . 29 Jeffers, Minnesota Area. 30 Southwest Minnesota, . .- . 33 South Dakota and Iowa. • 34 Dell Rapids and Split Rock Creek 35 New Ulm, Minnesota 36 Summary. 36 LITHOLOGY .AND STRATIGR..A.PHY. 38 Lithology ....• 38 Qu.a:::-tzite •• 39 Conglome:rates 39 Hudstones • 41 Int!:"usives •• 1.- 1 v Stratigraphy . • . , 48 New Ulm, Minnesota Column 48 Jeffers Column. 50 Jasper Colum1"1. • so Garretson Column. 51 Correlation of Generalized Colum..J.s :J_-? SEDIMENTARY STRUCTURES. 53 Bedding. 53 Trough . Cross-Bedding . 56 Tabular Cross-Bedding. 63 Herringbone Cross-Bedding. 66 Ripple Harks . • • • • • • 66 Climbing-Ripple Lamination • 79 Parting Lineation •• 79 Mudcracks .••.• 79 Mud Chips. • . 80 Load Structures. 84 Summary. 84 PALEOCURRENTS 87 Sampling and Data Reduction. 87 Symmetrical Ripples .. 90 Asymmetrical Ripples . • . 94 Cross-Eedding. • • . • • • % Other Paleocurrenc Indications 102 Summary of Paleocurrent Indicators . J.04 PETROLOGY ., j_Q/ Orthoq•Jartzites. J.07 Heavy Mine;.-als 1_..:_.;, q..., Conglomerates. 124 Hudstones .•. 130 Weathering and Alteration. 133 Conclusions. 135 SEDIMENTATION . • • 1 -.-1 Environment of Deposition. 137 Source Area. 142 Tectonics. 143 CONCLUSIONS J.46 147 REFERENCES CITED .• 150 vi TABLES Table 1 SUMMARY OF ISOTOPIC DATING RELEVANT TO THE POSSIBLE CORRELATIONS OF THE SIOUX QUARTZITE • . • • . • . 10 2 MINERP.L CONPOSITIONS OF UPPER PRECAl1BRIAN QUARTZITES IN THE LA..T<E SUPERIOR REGION. 12 3 OCCURRENCE OF SEDIMENTARY STRUCTURES IN THE SIOUX QUARTZITE . 55 4 GRAPHICAL TEST OF SIGNIFICAl.1"CE .• 89 5 CHEMICAL COMPOSITIONS OF HUDSTONE . 134 6 MODAL ANALYSES OF ORTHOQUARTZITES Vii Figure Frontispiece PALISADES OF THE SIOUX QUARTZITE ALONG SPLIT ROCK CREEK NEAR GARRETSON, SOUTH DAKOTA 1 UPPER QUARTZITES OF THE LAKE SUPERIOR REGION 2 2 OUTCROP AREA LOCATION MAP OF THE SIOUX QUARTZITE . • . • . 5 3 DIPPING BEDS OBSERVED IN THE SIOUX QUARTZITE . 24 4 GENTLY DIPPING BEDS OF ORTHOQUARTZITE ALONG SPLIT ROCK CREEK. 25 5 STRUCTURAL MAPS OF THE NEW ULM .AND JEFFERS AREAS . 26 6 STRUCTURAL MAP OF SOUTHWEST MINNESOTA EASTERN SOUTH DAKOTA. 27 7 CLOSELY SPACED JOINTS IN A FLAT-LYING BSD OF ORTHOQUARTZITE. • . 31 3 LENS OF PEBBLES ON BEDDHlG PLANE. 40 9 BASAL CONGLOMERATE OF THE SIOUX EXPOSED NEAR NEW ULH, MINNESOTA. 42 10 CONGL011"cRATIC ORTHOQUA ..-q_TzITE. 42 11 BLOCKY MUDSTONE 43 12 SILTY HUDSTONE. 44 lJ LOCATION HAP OF GENERALIZED COLUHNS L;6 14 GENERALIZED COLUMNS . 47 15 BASE OF THE SIOUX QUARTZITE NEAR NEW ULM. 49 16 HORIZONTAL BEDDING AND CROSS-BEDDING EXPOSED IN WEATHERED ORTHOQUARTZITE . 54 17 LIESEGANG BANDING IN ORTHOQUARTZITE 57 18 TROUGH CROSS-BEDDING EXPOSED IN THREE DIMENSIONS ......... 58 Figure 40 PLOTS OF VECTOR MEANS OF CURRENT RIPPLES BY TOWNSHIPS. 95 41 STRATIGRAPHIC PLOTS OF CURRENT RIPPLE VECTOR MEANS 97 42 PLOTS OF VECTOR MEANS OF CROSS-BEDDING BY TOWNSHIPS ......... 99 43 DISTRIBUTIONS OF CROSS-BEDDING BY TOWNSHIPS 100 44 MOVING AVERAGE OF CROSS-BEDDING BY TOWNSHIPS. 101 45 STRATIGRAPHIC PLOTS OF CROSS-BEDDING VECTOR MEANS •........... 103 46 PALEOCURRENT TRENDS IN UPPER PRECA!v.!BRIAN QUARTZITES OF THE LAKE SUPERIOR REGION . 106 47 PHOTOMICROGRAPH OF -TYPICAL . 108 48 GRAIN SIZE DISTRIBUTIONS FOR ORTHGQUARTZITES. 111 PHOTOMICROGRAPH OF ORTHOQUARTZITE SHOWING DEFORl1ATION LA..""1ELLAE IN QUARTZ GRAINS • 112 so PHOTOMICROGRl1.PH OF COARSE ORTHOQUARTZITE SHOWING MINOR FR.A.11EWORK CONSTITUENTS (STRETCHED YillTAQUARTZ AND CHERT) . • . LL4 51 PHOTOMICROGRAPH OF QUARTZ GRAIN W:TH SECONDAK{ OVERGROWTH. HEM.A.TI TE COATING BO'lrI BOUNDARIES J.l6 52 PHOTONICROGRAPH OF A MULTICYCLE GRAIN WITH ABRADED SECONDARY OVERGROWTH. 116 SJ PHOTOMICROGRAPH OF ORTHOQUARTZITE SHOWING GOOD AUTHI GENI C OVERGROW'THS. 118 54 PHOTOMICROGR.J\.PH OF AUTHIGENIC DIASPORE .. 120 55 PHOTOMICROGRAPH OF ORTHOQUARTZITE SHOWING SERICITE REPLACING A QUARTZ GRAIN. .. 122 56 PHOTOMICROGRAPH OF WELL ROUNDED, ZONED ZIRCON IN ORTHOQUARTZITE . 125 57 PHOTOI1ICROGRAPH OF MUDSTONE FROM PIPESTONE, MH1""NESOTA 132 1 INTRODUCTION The upper Precambrian Sioux Quartzite is a thick, gently dipping sequence of sedimentary orthoquartzite with minor inter- bedded siliceous conglomerate and muds tone. Cross-bedding and ripple marks are the common sedimentary structures. The Sioux is exposed at several localities in southwestern Minnesota and adjacent areas of South Dak cta and Iowa and is present in the subsurface over a much larger area (Figure 1). White named the Sioux Quartzite for outcrops along the Big Sioux River in South Dakota and Iowa in 1870, but a type section has never been estab- lished. The Sioux is the most widespread and the westernmost quartzite of a number of similar-appearing