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Home , Animikie Group, Penokean orogeny, Sioux Quartzite

Provenance analysis of the Marquette Range Supergroup sedimentary rocks from northwestern and western using U-Pb isotope geochemistry on detrital zircons by LA-ICP-MS

Rebekah Lundquist, Carleton College Geology Dept. Senior Integrative Exercise March 10, 2006

Submitted in partial fulfillment of the requirements for a Bachelor of Arts degree from Carleton College, Northfield, . TABLE OF CONTENTS

Abstract Introduction…………………………………………………………………………………...1 Detrital Zircon Geochronology…………………………………………………………..2 Tectonic Setting…………………………………………………………………………….....4 Geologic Setting………………………………………………………………………………7 Chocolay Group………………………………………………………………………….8 Palms Formation………………………………………………………………………..12 Ironwood Formation……………………………………………………………….13 Tyler Formation…………………………………………………………………………13 Analytical Methods…………………………………………………………………………..14 Results………………………………………………………………………………………..16 Palms Formation………………………………………………………………………..16 Tyler Formation…………………………………………………………………………25 Discussion……………………………………………………………………………………26 Provenance Interpretation………………………………………………………………26 Tectonic Implications……………………………………………………………………29 Conclusion…………………………………………………………………………………...30 Acknowledgements…………………………………………………………………………..31 References……………………………………………………………………………………32 Appendices…………………………………………………………………………………...35 Provenance analysis of the Marquette Range Supergroup sedimentary rocks from northwestern Wisconsin and western Michigan using U-Pb isotope geochemistry on detrital zircons by LA-ICP-MS

Rebekah Lundquist, Carleton College Geology Dept. Senior Integrative Exercise March 10, 2006

Cameron Davidson, Advisor

ABSTRACT Recent advancements in high-resolution U-Pb dating of heavy mineral fractions in sedimentary rocks have been increasingly useful in provenance studies. New LA-ICP- MS (laser ablation inductively coupled plasma mass spectrometry) data have been obtained from detrital zircon populations within the Palms and Tyler Formations, sedimentary units of the Marquette Range Supergroup in northwestern Wisconsin and western Michigan. The zircons from the Palms Formation are dominated by Neoarchean 207Pb/206Pb ages between 2664 and 2830 Ma with the strongest concentration of ages at ca. 2706 Ma. A Mesoarchean 207Pb/206Pb age of ca. 3523 Ma is also present. These data correspond with known ages of rocks in the region. Thus, the Puritan monzonite (2735 ± 16 Ma) and related volcanic rocks and the gneisses of the Watersmeet Dome region (3410-3600 Ma) and intruding dikes (ca. 2600 Ma) probably represent the major source of the Palms Formation. The Tyler Formation records a strong 207Pb/206Pb age between 1818 and 1938 Ma, with the youngest ages at 1818 ± 15 Ma. A Neoarchean component is present with 207Pb/206Pb ages between 2525 and 2815 with an average age of ca. 2665 Ma, along with additional ages of 2949, 2023, 2402, and 3168. The Paleoproterozoic ages in the Tyler Formation are typical of ages in igeneous intrusive rocks (1860 to 1835 Ma) that were emplaced in the Wisconsin magmatic terranes during the Penokean . The Neoarchean age of 2665 Ma, along with the lesser input of 2949 and 3168 Ma grains, represent ages typical of the high-grade gneiss and rocks of the Marshfield terrane.

Keywords: Marquette Range Supergroup, Paleoproterozoic, Archean, LA-ICP-MS, U-Pb, zircon, provenance

1

INTRODUCTION

Precambrian rocks of the Lake Superior region have long been of interest, largely due to the presence of extremely old (3.6 Ga) rocks thought to represent remnants of

Earth’s earliest crust and because of the occurrences of major economic deposits of iron- formations. However, even with a long history of petrologic, structural, geochronological, and geochemical study of the terranes of the Lake

Superior region, much of the tectonic history of this area remains to be understood.

Sedimentary successions can provide important records of tectonic processes and orogenic cycles, but studies of sedimentary units in the Lake Superior region are complicated by incomplete preservation of Precambrian strata and a widespread blanket of Pleistocene glacial deposits that covers most of the region. A variety of recent advancements in the development of high-resolution U-Pb dating techniques of detrital zircon have allowed detailed studies of Precambrian sedimentary rocks (e.g. Van Wyck and Norman, 2004; Pufahl and Fralick, 2004; Medaris et al., 2005). Provenance studies utilizing these new dating methods can provide valuable insights into the depositional environments of these rocks which in turn help describe the tectonic evolution of the

Lake Superior region.

In this study, I use U-Pb isotope geochemistry from detrital zircons contained in the sedimentary record of the Palms and Tyler Formations of northwestern Wisconsin and western Michigan to determine the provenance of these sedimentary deposits. This project is part of a larger, collaborative geochronological study undertaken by the Keck

Geologic Consortium Minnesota Research Group, under the direction of Professors

Craddock, Davidson, and Wirth of Carleton College and Macalester College. In this 2

paper, I 1) present new U-Pb age dates from detrital zircons contained in the sedimentary

Palms and Tyler Formations of Wisconsin and Michigan, 2) correlate these ages with intrusive or thermotectonic events, and 3) attempt to constrain the provenance of these formations.

Detrital Zircon Geochronology

The analysis of heavy detrital mineral fractions in clastic sedimentary rocks is useful for interpreting the sediment source and depositional environment of ancient (Fedo et al., 2002). Detrital zircon (ZrSiO4) plays a particularly prominent role

in heavy-mineral fraction sediment provenance studies. A common accessory mineral in

most rocks, zircon occurs in nearly all sedimentary deposits and is often studied because

of its resistance to chemical weathering and physical breakdown during transport

(Pollock et al., 2002). Zircon is useful in geochronological studies due to its extremely

high U/Pb ratio at the time of formation and its ability to retain the daughter products of

U and Th during radioactive decay (Fig. 1). The fact that U-Pb dating involves two

different U isotopes decaying at different rates to two different Pb isotopes provides the

possibility to detect potential isotopic disturbances (Bourdon et al., 2003). In an

undisturbed system, both the 238U-206Pb and 235U-207Pb decay should have consistent

ratios yielding the same ages and plot on a concordia diagram. Isotopic disturbances,

generally caused by Pb loss, result in discordant ages.

Myriad studies utilizing detrital zircon in the past 20 years have been

increasingly successful in both discovering the maximum age of stratigraphic successions

and time gaps in the geologic record, in determining provenance characteristics such as age and composition, and in testing regional paleogeographic reconstructions via 3 !"#$%&' (#)%" #%* +, $), + - , %(. , / )+#$0 ! * + . ' * 4 $';1<;)1%5* 2!6 5 4 2!3 : * 9 % ,%1;%#(9* % $ ( > ) * ; 1 < 0 1 ; * ' / $ . * ) , /,'89#';%* % - / ' , . + 0 ; * 7$%* * # , ) ( 0 1 ' * 9 & 8 % ' $ , #$').9:* # / * " , % = ()' , ' +%#'8* + * $ ( 7$* ) !"#$%&' 2!2 - Th decay chains, from Bourdon et Th decay chains, from Bourdon Pb-decay should have consistent Pb-decay should have consistent 232 207 U- 235 U and 235 U, 238 Pb- and 206 U- 238 al., 2003. The grayscale reflects half-life, with darker greys for longer half-lives. In an The grayscale reflects half-life, al., 2003. undisturbed system, both the plotting directly on a concordia diagram. ratios, yielding the same ages and Figure 1. Schematic drawing of the Figure 1. Schematic drawing of 4

provenance analysis (e.g. Fedo et al., 2002 and references therein). This success can be contributed to the development of single grain and in situ dating methods, such as

SHRIMP (sensitive high resolution ion microprobe) and LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) dating. Compared to SHRIMP dating,

LA-ICP-MS is less precise but faster and much more cost-effective. Thus, LA-ICPMS dating is especially useful for provenance studies which require the measurement of up to

100 grains per sample in order to include all major sedimentary source components

(Bernet and Speigel, 2004). The main problems of LA-ICP-MS dating are an instrumental mass bias and a laser-induced elemental fractionation of U and Pb due to volatility differences (Chang et al., in press). These errors can be corrected externally by repeated measurements of a standard during sample collection.

Sediment provenance analysis is an extremely important application of detrital geochronology because sediment source areas show distinct patterns of U-Pb crystallization, especially in orogenic settings. Cooling ages derived from bedrock samples often cluster in certain age groups rather than a continuum of ages across an orogen (Bernet and Speigel, 2004). Thus, the single ages derived from detrital zircon analyses can be compared with the age patterns of potential source areas, leading to better understanding of the tectonic history of the studied region.

TECTONIC SETTING

When using detrital zircon fractions for sediment provenance studies, it is necessary to compare geochronological data with other detrital data or known provenances to interpret the origins of the zircon; this requires an understanding of the tectonic history and geologic setting of potential source regions. The generalized tectonic 5

framework of the Lake Superior Region is presented in Figure 2. Archean-aged gneiss and granite rocks (ca. 3500 Ma-3100 Ma) are exposed in the Minnesota River Valley

(southern MN), the Watersmeet Dome region (northern MI) and within the Marquette

Range region (WI/MI). While the best studied of these Mesoarchean rocks are those of the Minnesota River Valley on the southern margin of the Superior , the granite and gneiss rocks in Wisconsin and Michigan are approximately the same age and appear to have had similar subsequent histories (Bickford et al., 2006; Sims, 1980 and 1991;

Schneider et al., 2002). The presence of these ancient terranes on both the northern and southern margins of the suggest they are remnants of earlier, perhaps more extensive, continental crust that was involved in the formation of the Superior craton in the interval 3000-2700 Ma (Bickford et al., 2006). Indeed, the Mesoarchean granite-gneiss units are juxtaposed with predominately juvenile Neoarchean (ca. 2.7 Ga) granite-greenstone terranes. Morey and Sims (1976), Sims et al. (1989), and Sims (1991) recognized the boundary between the granite-greenstone terrane and the older gneiss- granite rocks on the basis of contrasts in their respective aeromagnetic and gravity anomalies and defined it as the Great Lakes Tectonic Zone (GLTZ). The GLTZ has been interpreted as a north-dipping (30-40o) paleosuture (thrust zone) that resulted from a

continent-continent collision in late Archean time (Ojakangas et al., 2001). The Archean

craton began to undergo extension at ca. 2700 Ma (Ojakangas et al. 2001). An ocean

basin, south of present-day Lake Superior, opened as a result of extension; this extension

resulted in localized in the form of graben/half graben basins. Sediment and

volcanic rocks removed by erosion from the craton margin accumulated and were

preserved in these basins. These sedimentary deposits now exist as the Chocolay Group 6

Figure 2. Generalized tectonic map of Precambrian rocks and structural elements of the Lake Superior region. Modified from Sims, 1993. 7

in Wisconsin and Michigan (LaBerge and Mudrey, 1979). The stage was terminated by actual crustal separation and sea-floor spreading and was followed by a phase of convergent tectonics that produced a volcanic island arc (LaBerge and Ojakangas, 1992).

The island arc, preserved as the Wisconsin magmatic terranes, moved northward and collided with the southern margin of the Superior craton between 1895 and 1835 Ma in an event known as the (Sims et al., 1989). In Wisconsin and

Michigan, the Penokean can be divided into three different segments; from north to south, they are deformed and metamorphosed Paleoproterozoic sediment overlying Archean basement of the Superior craton, a central volcanic arc segment, and southern Archean crustal block (Van Wyck and Norman, 2004). In addition, LaBerge and Mudrey (1979) suggest that the accretion of the volcanic arc to the craton resulted in a fold-and-thrust belt with a to the north, where sediments of the Marquette Range and

Animikie Groups, composed of basal , iron-formations, and - sequences, were deposited. Following the termination of the Penokean orogeny, a period of widespread magmatic activity dominated by rhyolites and alkali occurred

(Van Wyck and Norman, 2004; Medaris et al., 2005). Around 1.1 Ga, a rift system, known as the , developed in central North America. The rift extends from what is now eastern Lake Superior to present-day Kansas (Craddock, 1979;

Ojakangas and Matsch, 1982). The rift system brought the Keweenawan Supergroup

Volcanic rocks to the Lake Superior region; these volcanics unconformably overlie the sedimentary deposits of the Marquette Range Supergroup and the .

GEOLOGIC SETTING

8

This study primarily focuses on the metasedimentary units of the Marquette

Range Supergroup (MRS) of the Gogebic and Marquette Ranges (Fig. 3). The MRS is a

Paleoproterozoic continental margin assemblage that lies unconformably upon the southern margin of the Archean Superior craton in northern Wisconsin and Michigan.

The MRS includes, from oldest to youngest, the Chocolay Group, a shelf marine facies, the Menominee Group, turbidites passing up into and the Baraga

Group, a sequence of and turbidites (Ojakangas et al., 2001). The sedimentary rocks in this area generally increase in thickness from north to south. In the Gogebic

Range (northwestern Wisconsin) the succession is about 2 km thick and increases to as much as 9 km thick in the Marquette Range along the Michigan-Wisconsin border

(Morey 1993, 1996).

Chocolay Group

Archean granitic and mafic volcanic rocks are unconformably overlain by the lowest units of the Chocolay Group of the MRS, Sunday and Bad River

Dolomite (Fig. 4). The basal unit of the MRS, Sunday Quartzite, is a prominently cross- bedded reddish quartzite containing layers of quartz and granite cobbles in the lower part of the formation (LaBerge and Ojakangas, 1992). The majority of the formation is a gray quartzite, punctuated with current ripple marks and cross-bedding.

The Sunday Quartzite grades upward into the Bad River Dolomite; the transition between the two is characterized by interbedded dolomite and quartzite (LaBerge and Mudrey,

1979). The dolomite is usually grey to buff colored and contains irregular, patchy beds of and stromatolitic layers (LaBerge and Mudrey, 1979). Quartzose beds are common in the upper part of the formation. In most locations, the Bad River Dolomite 9

Wgm Owr Wgd N Wsm Wgr Wgr Canada Owr Wgd Wmi 0 25 50 100 K Minnesota W E Wmv Wmm Wgr Kilometers Wgd Wms S

Xag Xai Yl Wsm Wst Wgd Yplv Wgd Wgr 05KP-4

Wmi Wms Wgm Ynv Wgm KP05-3 Wms Yc Ynv Wmv Wmv Wgd Wps Ydt Ybb Wmv Wmm KP05-10 Wmi Ynv Xai Wgr Yplv Yplv Wmi Wgd Ydt Wps Lake Superior Wgr KP05-1 Yj Wgr Ybb KP05-45 K Yc

Wmm Wmv Yn Ydt Ynv Ycv Ypr Yf Xm Wmv Xag Wv Yc K KP05-16 Wgr Duluth Yn Wga Ych Yj K Yk KP05-23 Ykr Ys Wmv Ydi Ypv Xvs Wmm Wgd Xmiv KP05-21 Yor Wgw Xag Ws KP05-42 Xe Xmn KP05-22 Xc Ys Wms K Xmq Xnr Yf Yfc Xm Agn Wps Yfl Ygr Xmd W Xi K Wgr Xmsa Ygp Wp Xmb Cm

isconsin Michigan Minnesota Agn Xh Xmu KP05-36 Ycv Wv Xam Xmv Wgd W isconsin Xch Wgd Xmsa KP05-40 KP05-32 KP05-30 Ygb Xb Wgr Yo Xt Agn Xpi Wd Yc Xpu Yhi Ycv Xbc Wmv Agn Xmv Agn Xsv Xdvg Xgr Xmi Agn Xgd KP05-21 Xag Xgg Xgrs K Wqz Xga Xgg Xba Ycv Xgg Xmg Xrhd K Xag Xlf Xqd Xgr Xgg Xmi Xdvg Agn Xgd Xmv Xgat Xpp Xbq Xq Xgd Xmv Xga Xmsa K Yhf Xgd Agn Ycv Xgt Cm K Xop Xtg Xmg Yh Yhp Xmv Cu Xgb Xgt Ywm Cu Xmi K Xgd Cu Xgb Xgb Xop Xf Op Wgn Xggn Ywa Ywb Xmv Op Wgr Xgd Agn Xgr Olu Xgp Xgn Xrg Ywg K Yss Oa K Omu Yws Xg Ywa Ywap Op Xgr KP05-2 Xgt Agn Xgc Ywn Xgp Xgr XAf St. Paul Xg Ywe Oa Xft Wmg Ywr Cu Olu Osi Ywg Xv Xggr Xmc Xgr Olu Omu Wmv K Xg Agn Op Osi Ywwg Wgr Olu Cu Wgn Xr K Agn Wt Omu K Op Om Wgr Olu Northfield Wif Cu Olu Xgr Xsq Omu Oum Su

Figure 3. Geologic map of Archean to rocks in the Lake Superior Region. Sample locations for all detrital zircon studies undertaken by the Keck Geo- logic Consortium Minnesota Research Group are labeled. Box outlines samples discussed in this study, KP05-42, Palms Formation, and KP05-40, Tyler Formation. Refer to the following page for map key. 10 Sedimentary and Medisedimentary Rocks Minnesota Wisconisin and U.P. Michigan Key describing rock formations of Figure 3. K sedimentary rocks Su Silurian undivided

Owr Winnipeg and Red River Fms. Om

Oum Upper & Middle sed. rocks Osi Sinnippee Group

Omu Middle Ordovician sedimentary rocks Oa Ancell Group

Olu Lower Ordovician sedimentary rocks Op Prairie du Chien Group

Cu undivided Cm Munising Fm Volcanic and Metavolcanic Rocks Plutonic and Metaplutonic Rocks Phanerozoic Cu Cambrian undivided Minnesota Wisconisin and U.P. Michigan Minnesota Wisconisin and U.P. Michigan

Yhi Hinkley Yj Yplv Portage Lake Volcanics Ys Siemens Creek Volcanics Ydt Ygp granophyre

Yfl Fond du Lac Formation Ych Chequamegon Sandstone Ynv North Shore Volcanic Group Yplr Portage Lake Vol-rhyolite Ybb Beaver Bay Complex Ygr granite

Ydi Devils Island Sandstone Ycv Chengwatana Volcanics Yplv Portage Lake Volcanics Yl Logan Intrusions Ygb

Yor Orienta sandstone Ypr Porcupine Volcanics-rhyolite Yo olivine gabbro

Yf Freda Sandstone Ypv Porcupine Volcanics Yhp Hager Quartz Porphyry

Yfc Yk Kallander Creek Volcanics Freda sandstone-cgl member Ywa WRB-anorthosite Ykr Kallander Creek-rhyolite Yn Nonesuch Formation Ywb WRB-Belognia Granite Yh Yc Copper Harbor Conglomerate Hager Rhyolite Ywm WRB-Peshtigo Mangerite Ycv Copper Harbor-volcanic member Ywr WRB-Red River Granite

Ycv Chengwatana Volcanics Ywwg WRB-Waupaca Granite Ywg WRB-Wolf River Granite

Yhf High Falls Granite

Ywap WP-aplite Ywe WP-Big Eau Pleine granite Ywn WP-Nine Mile Swamp granite

Yws WP-quartz syenite Yss WP-Stettin pluton

Xsq Sioux Quartzite Xbq Barron Quartzite Xmb metabasalt Xv volcanic rocks undivided Xgr late tectonic intrusions Xg granite

Xag Rove, Virginia, Thomson Xq quartzite Xr rhyolite Xgd syntectonic intrusions Xgr late tectonic intrusions Xrg rhyolite Xai Biwabik, Gunflint, Pokegama Xpu Paint River Group Xop post tectonic intrusions Xqd quartz diorite Xrhd rhyolite and dacite Xgp porphyritic granite Xmiv iron-formation Xc Copps Formation Xpp Peavy Pond Complex Xmv Michigamme-volcanic member Xmd metadiabase Xnr North Range Group Xt Tyler Formation Xmc Milladore Volcanics Xmg metagabbro Xlf Little Falls Formation Xpi Riverton Iron-Formation Xmv Xmi mafic metavolcanic Xggn granitic gneiss metasedimentary and metavolcanic Xmn Negaunee Iron-Formation Xh Hemlock Formation Xga granitic rocks Xmsa metasedimentary rocks Xi Ironwood Iron-Formation Xg granitic rocks undivided Xf felsic volcanic Xmq Trout Lake, Denham Xsv biotite schist Xtg felsic volcanics Xgg granite and tonalite Xm Michigamme Formation Xe Emperor Volcanic Complex Xgt granodiorite-tonalite Xvs volcanic-sedimentary unit Xgn Xdvg dacite and graywacke gneiss-amphibolite Xam magnetic unit Xggr gneissic granite

Xbc Blair Creek Formation Paleoproterozoic Xmmc Menominee and Chocolay Groups Xgb gabbro Xmv bimodal volcanics Xmsa Ajibik and Siamo Formations Xft foliated tonalite Xba basaltic breccia Xmu Menominee Group (Palms) Xgr alkali-fs granite Xb Badwater Greenstone Xch Chocolay Group Xgrs Spikehorn Creek Granite

Xgat Athelstane Quartz Monzonite

XAf mylonite Xgc Cherokee Granite

Wsm schist-rich migmatite Wif iron-formation Wqz rocks of magnetic quiet zone Wv volcanics undivided Wgd post-tectonic granitic rocks Wp Puritan Quartz Monzonite

Wms metasedimentary rocks Ws biotite schist Wmm mixed metavolcanic rocks Wt tuff breccia Wmi post-tectonic mafic intrusions Wmg metagabbro

Wps paragneiss Wgw graywacke Wmv mafic metavolcanic rocks Wd Dickinson Group Wst Saganaga Tonalite Wga gneiss and amphibolite Wgr syntectonic granitic rocks Wgn gneiss Archean Wgm granite-rich migmatite Agn gneiss

Agn gneiss and granite East-central Minnesota NW Wisconsin NW Wisconsin and N Michigan Gunflint Range Central MN W. E. Gogebic Range W. Marquette Range E. Marquette Range

Michigamme Rove Virginia Thomson Tyler Michigamme

(KP05-03) (KP05-23) (KP05-40) Copps Goodrich Quartzite Group Baraga Baraga Goodrich Quartzite

Emperor Volcanic Gunflint Biwabik Rabbit Lake Ironwood Complex Negaunee Negaunee Iron-Formtion Iron-Formtion Formation Iron-Formtion Blair Creek Iron-Formtion Iron-Formtion Formation Pokegama basal North Range Palms Palms Siamo Slate Siamo Slate Quartzite congomerate Group (KP05-42) (KP05-42) Ajibik Quartzite Ajibik Quartzite

ANIMIKIE GROUP ANIMIKIE (KP05-01) Menominee Group Menominee Chocolay Bad River Archean Archean Archean Archean Archean Dolomite Group Basement Basement Basement Archean Basement Basement Sunday Basement

ARCHEAN - PALEOPROTEROZOIC - ARCHEAN Quartzite MARQUETTE RANGE SOUPERGROUP RANGE MARQUETTE Chocolay Gp

Figure 4. Stratigraphic correlations of Archean and Paleoproterozoic stratified rocks of the Lake Superior region. Modified from Hemming et al.,1995, and Ojakangas et al., 2001. Formations with sample numbers represent units which have been undertaken by participants in the Keck Geologic Consortium Minnesota Research Group for detrital zircon geochronological studies. Detrital zircon data presented in this study are from the Palms Formation and the Tyler Formation, highlighted in red. 11 12

has been metamorphosed to a tremolitic siliceous marble. Following the deposition of the Chocolay Group rocks, a period of erosion occurred which removed the Sunday

Quartzite and Bad River Dolomite from all but the western end of the Gogebic range and the eastern end of the Marquette Range.

Palms Formation

The Palms Formation comprises the basal detrital unit of the Menominee Group of the MRS; it correlates lithologically with the Pokegama formation of Minnesota, the basal detrital unit of the Animikie Group (Fig. 4) (LaBerge and Ojakangas, 1992).

Approximately 140 meters thick in Wisconsin, the formation thickens to about 230 meters east of Wakefield, Michigan (LaBerge and Murdrey, 1979). The Palms

Formation is composed of three mapable units: (1) a basal conglomerate unconformably overlying Lower Precambrian greenstone and granite (in the central part of the range) or

Bad River Dolomite and Sunday Quartzite (on the east and west ends of the range); (2) a thin- to medium-bedded buff-pink quartzite with thin interbeds of argillite or greywacke; and (3) a buff to pink, medium- to thick-bedded quartzite (LaBerge and Mudrey 1979).

The dominant framework of the quartzite member is composed of well-rounded quartz and feldspar grains with a minor component of chert grains (LaBerge and Ojakangas,

1992). At the top of the Palms Formation, thin beds of granular iron-formation are interbedded with quartzite with the abundance and thickness of beds of iron-formation increasing upward with a corresponding decrease in detrital beds. This transition marks the conformable contact between the Palms Formation and the overlying Ironwood Iron-

Formation and signals a major change from detrital to chemical sedimentation

(Ojakangas et al., 2001). 13

Ironwood Iron Formation

The Ironwood Iron Formation consists of silica and iron-bearing minerals which have been divided into two facies types, slaty and cherty. The slate is a chemical consisting of fine layers of Fe-oxide and chert. The chert is a grainstone composed of rounded, sand-sized intraclasts of chert, Fe-oxide, Fe-carbonate, and/or Fe- silicate (Pufahl and Fralick, 2004). The iron-formation contains little detrital material, even though it is 600 to 900 meters thick in places (Aldrich 1929, LaBerge and Mudrey,

1979). While the iron-formation has a simple composition of chert and iron materials, it is extremely varied in appearance and has thus been divided into five members based on the dominant texture and bedding characteristics (LaBerge and Ojakangas, 1992).

Throughout the Lake Superior Region, iron-formations are overlain both conformably and unconformably by thick slate-greywacke sequences and intercalated with volcanic rocks (Fig. 4). This signals a change back to detrital sedimentation along with volcanic activity (LaBerge and Mudrey, 1979).

Tyler Formation

In the Gogebic Range, the Tyler formation conformably overlies the Ironwood

Iron-Formation (Fig. 4) (LaBerge and Mudrey, 1979). The Tyler is lithologically comparable to the Copps Formation at the eastern end of the range, the Michigamme

Formation to the east, and the Rove, Thomson, Rabbit Lake, and Virginia Formations of

Minnesota and Ontario (Ojakangas et al., 2001). The formation is composed of a thick sequence (approximately 2500 m) of interbedded greywacke/siltstone and argillite/slate.

The typical Tyler greywacke framework contains quartz (73%), rock fragments (17%) and feldspar (10%), suggesting a granitic quartz-diorite provenance (Alwin, 1979). 14

Although the majority of the beds are structureless, some of the greywacke and siltstones show signs of turbidity current deposition, such as graded bedding, rip-up clasts, and

Bouma sequences. Paleocurrent indicators, marked by sole marks and small-scale cross- bedding, show movement toward west-northwest and have little stratigraphic variation, suggesting a single source area for all of the Tyler Formation (LaBerge and Mudrey,

1979).

ANALYTICAL METHODS

Detrital zircon samples were processed at Macalester College using conventional mineral separation techniques (crushing, disc mill, Wilfley table, magnetic free-fall) followed by heavy liquid separation in methylene iodide (specific gravity 3.32) and further magnetic separations with a Barrier Frantz isodynamic separator. From the separated portion, approximately 100 grains per sedimentary unit were selected randomly in an attempt to include the complete range of colors and morphological types in order to analyze zircons that would reflect all of the possible source terranes. The selected zircons were mounted, along with the laboratory standards Peixe and FC-1 (564 ± 4 Ma and 1100 Ma, respectively; Chang et al., in press), with epoxy in 1-inch diameter grain mounts and polished to expose flat surfaces at the cores of the grains for analysis.

Cathodoluminescence (CL) images of the zircons were collected at the University of

Idaho and backscattered electron (BSE) images were collected at Carleton College, both with a JEOL 5600 scanning electron microscope (SEM), in order to identify growth rims and inclusions within the zircons and to provide a base map for recording laser spot locations. An attempt was made to sample both cores and rims of the zircons, especially 15

when obvious growth rims were apparent. However, due to the small size of the grains in this study, analyses were generally limited to the core of the zircon.

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) analyses were performed in the GeoAnalytical Lab at Washington State University under the direction of Jeff Vervoort, Cameron Davidson, Karl Wirth and John Craddock, along with KECK 2005 student participants. Laboratory procedures for collection of the U-Pb data are described by Change et al. (in press). All work was performed using a

ThermoFinnigan Element2 single collector double focusing magnetic sector ICP-MS coupled with a New Wave UP-213 laser ablation system operating with a wavelength of

213 nm. Zircons were ablated using a laser frequency of 10 Hz and a laser density of approximately 10J/cm2. The laser beam was focused on the sample surface and ablation

pit sizes ranged from 30 to 40 µm in diameter.

The ablated material was carried to the ICP-MS by He and Ar gas. Each analysis

consisted of a 6 second warm-up, an 8 second delay to enable the sample to reach the

plasma, and 35 seconds (300 sweeps) of rapid scanning in the e-scan (electric scan) mode.

Data were acquired in pulse counting detector mode with 3 points measured per peak to

obtain the masses of 202Hg, 204(Pb + Hg), 206Pb, 207Pb, 208Pb, and 235U, while analog mode

was used to obtain the masses of 232Th and 238U. Quadrupole settling time was 1 ms for

all masses and the sample time was 4 ms. The Element2 was tuned before each session

using the NIST 612 glass standard and the zircon standard Peixe was analyzed until

fractionation was stable and the variance in measured 206Pb/238U and 207Pb/206Pb ratios

were at or near 1% (1 sigma standard deviation). A gas blank was collected in counting

mode before each analysis with the plasma on but laser not firing. All operating 16

parameters, including ICP-MS and laser settings, were held constant for standards and unknowns to minimize any potential bias between samples and standards.

Data reduction was performed following the method described by Chang et al. (in press). The raw data were corrected for fractionation and downloaded to a computer for off-line processing using an Excel program supplemented with Visual Basic macros.

Final ages, concordia diagrams and probability density distribution-histogram plots were produced using the Isoplot/Ex macro (Ludwig, 2003).

RESULTS

I obtained LA-ICP-MS age data for zircons from the Palms and Tyler formations in northwestern Wisconsin and western Michigan. Sample locations are shown on Figure

3 and analytical data are summarized in Table 1. Complete analytical data are given in

Appendices 1 and 2.

Palms Formation

I collected approximately 10-kg of medium-grained quartzite of the Palms

Formation (KP05-42) from an outcrop near Radio Tower Hill in Wakefield, MI, off of

Highway 2 (Fig. 3). The rock at this locality consists of interbedded argillite, siltstone, and sandstone transitioning to massive feldspathic quartzite (Fig. 5A). Most beds are continuous across the outcrop with lenticular beds of cross-bedded sandstone.

Measurements of cross-bedding show a strong paleocurrent trend to the west with a weaker trend to the east. At this location, the Palms formation dips steeply 80º to the north.

Zircons separated from the Palms Formation are strikingly similar, consisting of small and primarily subhedral grains (Figs. 6 and 7). LA-ICP-MS analysis yielded the Table 1. SUMMARY OF DETRITAL-ZIRCON AGES, MARQUETTE RANGE SUPERGROUP, LAKE SUPERIOR REGION, U.S.A. (modified from Goodge et al., 2002)

Stratigraphic Unit/Area Sample Number Major Zircon Age Populations (Ma)§ Youngest zircon grains (Ma)† Maximum depositional age‡

Palms 05KP-42 2706, 3523, 2594 2594 ± 12 (1) Paleoproterozoic/Neoarchean Wakefield, MI*

Tyler 05KP-40 1850, 2665, 2949, 2023, 2042, 3168 1818 ± 15 (10) Paleoproteroizic Hurely, WI*

*Detrital zircon sample locations. (Palms: UTM Zone 16T, Easting 275471, Northing 5151275. Tyler: UTM Zone 15T, Easting 715350, Northing 5149709. NAD27 Conus Datum). § Age populations to nearest m.y. listed in order ot decreasing relative abundance. † 207Pb/206Pb ages and errors; number of grains in parentheses. ‡ Depositional age constrained by youngest discrete zircon age population. 17 18

A

B

Figure 5. (A) Outcrop features of the Palms Formation, KP05-42, showing interbed- ded argillite, siltstone, sandstone, and quartzite. (Compass width 6.5 cm). (B) Outcrop picture of greywacke-slate of the Tyler Formation, KP05-40. Note the rip-up clasts. (Pen height 15 cm). 19

250 µm AAAAA

250 µm B

Figure 6. (A) Cathodoluminescence images of zircons from sample KP05-42, Palms Formation. (B) Back-scattered electron image of zircons from sample KP05-40, Tyler Formation. KP05-42 (Palms Formation) KP05-40 (Tyler Formation)

A A

B B

Figure 7. Detrital zircon analyses from the Palms Formation (KP05-42) and the Tyler Formation (KP05-40) produced by NIH ImajeJ image processing program (Rasband, 2006). (A) Histogram representing the area of all zircons analyzed by LA-ICP-MS. (B) Histo- grams showing the circularity of the analyzed zircons. A value of 1.0 indicates a perfect circle. As the value approaches 0.0, it indi- 20 cates increasingly elongated zircon grains. data-point error ellipses are 2V

0.75 KP05-42 Palms Formation n=111 3400

0.65

3000 206Pb 2706 238U 0.55

2600

0.45

2200 (2594) 3523

2500 2700 2900 3100 3300 3500 3700 0.35 6 10 14 18 22 26 30 34

207Pb/235U

Figure 8. Concordia diagram for detrital zircons from sample KP05-42, Palms Formation; n = number of individual grains analyzed. Errors for individual analyses are <10% discordant (see Appendix 1). Inset shows relative probability distributions for the zircons ages (in Ma), from Figure 9. Ages assigned to peaks derived from Unmix Ages modeling (Ludwig, 2001); ages in parentheses calculated as simple mean of discrete peaks. 21 50 KP05-42 Palms Formation n=111

40 probability Relative

30 Number 20

10

0 2500 2700 2900 3100 3300 3500 3700 Age (Ma)

Figure 9. Probability density distribution-histogram plot showing distribution of 207Pb/206Pb ages from sample KP05-42. 22 0.7 data-point error ellipses are 2V KP05-40 Tyler Formation n= 100 0.6 3000

0.5 2600

206Pb 238 1850 U 2200 0.4

1800 0.3

2665 1400 (2949) (2023) (2402) (3168) 0.2 1700 1900 2100 2300 2500 2700 2900 3100 3300 0 4 8 12 16 20 24

207Pb/235U

Figure 10. Concordia diagram for detrital zircons from sample KP05-40, Tyler Formation; n = number of individual grains analyzed. Errors for individual analyses are <10% discordant (see Appendix 2). Inset shows relative probability distributions for the zircons ages (in Ma), from Figure 11. Ages assigned to peaks derived from Unmix Ages modeling (Ludwig, 2001); ages in parentheses calculated as simple mean of discrete peaks. 23 40

35 KP05-40 Tyler Formation n=100 30 Relative probability Relative

25

20 Number 15

10

5

0 1700 1900 2100 2300 2500 2700 2900 3100 3300 Age (Ma)

Figure 11. Probability density distribution-histogram plot showing distribution of 207Pb/206Pb ages from sample KP05-40. 24 25

data summarized in Table 1 and plotted in Figures 8 and 9. The 111 concordant grains analyzed from the sample are split into three groups that are well separated in frequency and age. The histogram in Figure 9 shows one major cluster of analyses (108 out of 111) of Neoarchean 207Pb/206Pb ages between 2664 and 2830 Ma. These zircons varied from 1

to almost 10 percent discordant and show a concentration of ages at ca. 2706 Ma.

Although represented by only 2 grains, a Mesoarchean 207Pb/206Pb age of ca. 3523 Ma is

present. One grain yielded a three percent discordant 207Pb/206Pb age of 2594 ±12 Ma,

the youngest age represented in this data set.

Tyler Formation

I collected approximately 10-kg of medium- to coarse-grained sample of the Tyler

Formation (KP05-40) from a road cut at the junction of U.S. Highways 51 and 2, north of

Hurley, WI (Fig. 3). The sample is a greywacke-slate sequence; the greywacke beds

contain Bouma sequences, rip-up clasts, and small-scale cross-bedding (Fig. 5B). The

beds at this locality strike east-northwest and dip 60º-75 º northwest.

The Tyler Formation contains abundant prismatic zircons of a broad size and

shape range (Figs. 6 and 7). LA-ICPMS analytical data (Table 1, Figs. 10 and 11)

yielded 100 grains of less than ten percent discordance and suggest that the ages of the

sample contain several populations of detrital zircons. Most of the zircons (76 out of 100

concordant grains) have Paleoproterozoic 207Pb/206Pb ages between 1818 and 1938 Ma

with the youngest ages at 1818 ± 15 Ma. The well-defined peaks of the histogram in

Figure 11 show the strongest concentration at ca. 1850 Ma. A second cluster of ages is

represented by 18 grains with 207Pb/206Pb ages between 2525 and 2815 Ma with an

average Neoarchean age of 2665 Ma. The analyses in this range tend to fall either on 26

concordia or slightly below. The data show additional 207Pb/206Pb ages of 2949 (2

analyses), and 2023, 2402, and 3168 Ma, each represented by one analysis that falls

slightly below concordia.

DISCUSSION

Provenance Interpretation

Palms Formation

U-Pb data from detrital zircons of the Palms Formation indicate that the age

spectra within these rocks are dominated by Neoarchean zircons with a minor

Mesoarchean input. The majority of analyzed grains within the Palms Formation have an

age of ca. 2706 Ma. The youngest zircon yields an age of 2594 ± 12 Ma which indicates

a maximum age of deposition to be between Neoarchean and Paleoproterozoic. These

detrital zircon ages for the most part match what is known about the age of Archean

basement rocks in the Superior Province (Fig. 12). Specifically, the cluster of 207Pb/206Pb ages between 2664 and 2830 Ma present in the Palms Formation have been similarly recorded in studies by Sims et al. (1980), revealing an age of 2735 ±16 Ma for the Puritan quartz monzonite, a pluton that intrudes the Ramsay Formation (mafic and felsic metavolcanic rocks), outcropping just south of the site of sample KP05-42. Thus, the

Archean Puritan quartz monzonite and related intrusions probably represent a major component in the sediment source to the Palms Formation.

The Palms also contains a Mesoarchean age signature represented by two analyses of 3523 Ma. These ages correspond with geochronological data from tonalitic gneiss protoliths exposed in the Watersmeet Dome in northern Michigan which indicate that this rock is between 3410 Ma and 3600 Ma (Bickford et al., 2006). Leucogranite 27

Lake Superior

KP05-42 Superior Province KP05-40 Watersmeet Dome region

Wisconsin magmatic terranes (Pembine-Wausau terrane)

north (Marshfield terrane) Figure Location

50 km USA

Figure 12. Generalized geologic map of the Wisconsin magmatic terranes in northern Wisconsin and Michigan, modified from Van Wyck and Johnson (1997) in relation to sampled locations of the Palms (KP05-42) and Tyler (KP05-40) Formations. 1-Archean basement of the Superior Province. 1a-Puritan Quartz Monzonite and the Northern Complex, 2735 ±16 Ma (Sims et al., 1980). 1b-High-grade gneiss basement (Watersmeet-type), 3400-3600 Ma (Bickford et al., 2006). 2-Marshfield terrane. 2a- Archean basement of the Marshfield terrane, 2550, 2680, 3000-3200 Ma (Van Wyck and Norman, 2004). 2b-Cover rocks of the Marshfield terrane, age uncertain. Both 2a and 2b are intruded by numerous Penokean synorogenic plutons (not shown), 1860 to 1835 Ma by Sims (1996). 3-Marquette Range Supergroup sedimentary deposits. 4-Gneiss domes developed south of the Niagara within the Pembine-Wausau terrane. 5-Volanic and lesser sedimentary rocks of the Pembine-Wausau terrane, intruded by numerous Penokean synorogenic plutons (not shown). 6-Alkali-granite and 1760 Ma granites (undifferentiated). 7-Wolf River batholith (1.5 Ga). 8-Cover younger than 1.5 Ga. 28

dikes intruding the Watersmeet Dome gneiss reveal ages of ca. 2600 Ma (Van Wyck and

Norman, 2004), which can explain the presence of the 2594 ± 12 Ma analysis.

Tyler Formation

The detrital zircon data contained in the Tyler Formation is dominated by

Paleoproterozoic grains of ca. 1850 Ma. This age is typical of igneous intrusive rocks that were emplaced in the Wisconsin magmatic terranes during the Penokean orogeny

(Van Wyck and Johnson, 1997). In Wisconsin, the orogen has been divided into two terranes, a northern Pembine-Wausau terrane and a southern Marshfield terrane, both of which contain numerous Penokean synorgenic plutons (Fig. 9). Of these, the Marshfield terrane contains calc-alkaline plutons of granitic composition with age components ranging from 1860 to 1835 Ma (Sims et al., 1989, 1993). Therefore, these Penokean volcanics in the Wisconsin magmatic terranes represent the major component in the sediment source to the Tyler Formation. The maximum age of deposition for the Tyler

Formation is the age of the youngest recorded zircons: Paleoproterozoic grains of 1818 ±

12 Ma. This age could potentially push the boundary of rocks considered to be Penokean in age, usually thought to end ca. 1835 Ma (Bickford et al., 2006).

The Tyler Formation also records a Neoarchean U-Pb age range of 2525 and 2815

Ma with an average age of 2665 Ma, along with lesser input of 2949 and 3168 Ma grains.

The source of these grains is most likely the high-grade gneiss and granite rocks of the

Marshfield terrane, which Van Wyck and Norman (2004) showed to contain zircons of

2550, 2680, and 3000 to 3200 Ma (Fig. 12).

Samples in the Tyler Formation show contributions of ages from 2023 and 2402

Ma sources. These ages are significant yet problematic because there is no evidence for 29

local derivation of these grains, since gneisses of these ages are unknown in the

Wisconsin/Michigan region (Van Wyck and Norman, 2004). There are two interpretations for the provenance of these detrital data: either crustal rocks of this age do occur locally and are buried or have yet to be identified through high-resolution dating techniques, or these grains were introduced to the Tyler Formation from terranes outside the Lake Superior region. In a study of LA-ICP-MS geochronology detrital zircon ages of early quartzites in Wisconsin, Van Wyck and Norman (2004) posit the possibility that the source of 1.9-2.3 Ga zircons contained within their sampled Baraboo quartzite could be explained by recent geophysical studies that indicate the southern limit of the Marshfield terrane is marked by an east-west lineament called the Trempealeau discontinuity (Cannon et al., 1999). The Trempealeau discontinuity could possibly separate the Marshfield terrane from distinct Pre-Penokean crust south of the discontinuity, which may well be the source of the 2023 and 2402 Ma grains within the

Tyler.

Tectonic Implications

The tectonic setting of the Lake Superior region during the Paleoproterozoic remains controversial. Primarily based on sedimentological and stratigraphic data,

Hoffman (1987) and Barovich et al. (1989) proposed that the Paleoproterozoic sequences were deposited in a migrating foreland basin that formed in response to crustal loading during the Penokean Orogeny. The foreland basin model was modified by Morey and

Southwick (1995) and developed further by Ojakangas et al. (2001); these studies ascribed the deposition of the Marquette Range and Animikie Groups to continental rifting during early, pre-collisional phases of the Penokean orogenic cycle. Conversely, 30

Schneider et al. (2002), Pufahl and Fralick et al. (2004) and others suggest that the MRS sequences were deposited on an intermittently active, southward-sloping continental margin, with subsidence being driven by back-arc extension, as put forth by Hemming et al. (1995).

Recent geochronological studies using U-Pb dating of detrital zircons support the back-arc model of deposition (Van Wyck and Johnson, 1997; Schneider et al., 2002;

Pufahl and Fralick, 2004, Van Wyck). Similarly, this study finds that the strong presence of Penokean grains within the Tyler Formation suggest that its deposition was contemporaneous with the arc-related volcanic rocks now preserved as the Wisconsin magmatic terranes. This can best be explained by the back-arc model which, based on

SHRIMP U-Pb data from units within the MRS, was outlined by Schneider et al. (2002).

This model, built around several geological constraints, envisions oblique Penokean subduction driven by back-arc extension. An important constraint in the derivation of this model involved the correlation of lithostratigraphic units, specifically iron-formations, throughout the region. Surely, further studies comparing the LA-ICP-MS U-Pb age results for the Palms and Tyler Formations of this study with their correlative units in

Minnesota will help to further develop the tectonic framework of the back-arc model of deposition for the Paleoproterozoic sedimentary units of the Lake Superior region.

CONCLUSION

LA-ICP-MS 207Pb/206Pb ages of detrital zircons from the Palms Formation

indicate that this sedimentary unit was derived from the Neoarchean basement rocks

consisting of the Puritan quartz monzonite and its correlative rocks with a Mesoarchean

input from the high-grade gneiss rocks of the Watersmeet Dome region. Detrital zircons 31

within the Tyler Formation contain a major population of Penokean grains of ca. 1850

Ma, suggesting a provenance of Penokean synorgenic plutons emplaced in the Marshfield magmatic terranes of Wisconsin. The Neoarchean U-Pb age of 2665 Ma, along with lesser input of 2949 and 3168 Ma grains, are from the high-grade gneiss and granite rocks of the Marshfield terrane.

This study proves the effectiveness of using LA-ICP-MS for detrital zircon geochronology. Although less precise that SHRIMP analysis, this method provides an efficient and cost effective technique, offering the potential to analyze the large number of zircon grains necessary for an effective provenance study. Continuing U-Pb dating of detrital zircons contained within the stratigraphic record of the Lake Superior region will strengthen the stratigraphic and temporal relationships of Precambrian sedimentary units for the entire Lake Superior region as well as contribute to new interpretations of

Precambrian tectonic history.

ACKNOWLEDGMENTS

I thank Cameron Davidson, Karl Wirth, and John Craddock for advising and assistance. In gratitude I acknowledge Jeff Vervoort for help with the U-Pb dating and for access to the GeoAnalytical Lab at Washington State University. I thank MN Keck participants for help with sample collection and processing, and Geology Seniors of 2006.

32

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Van Wyck, N. and Norman, M., 2004, Detrital Zircon Ages from Early Proterozoic Quartzites, Wisconsin, Support Rapid Weathering and Deposition of Mature Quartz Arenites: The Journal of Geology, v. 112, p. 305-315.

Appendix 1. Laser ablation U-Pb data and calculated ages for detrital zircons from the Palms Formation. <10% Discordant Ratios Ages 207 235 206 238 207 206 207 235 206 238 207 206 Spot # Session Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ

05KP42_001a 1 11.39270 0.57964 0.47553 0.02299 0.17376 0.00127 2555.8 46.4 2507.8 99.7 2594.2 12.1 05KP42_002a 1 12.95528 0.66235 0.51023 0.02482 0.18416 0.00132 2676.4 47.1 2657.6 105.1 2690.7 11.8 05KP42_003a 1 12.70337 0.65606 0.49616 0.02435 0.18570 0.00139 2657.9 47.5 2597.3 104.1 2704.5 12.3 05KP42_004a 1 12.74002 0.64461 0.49883 0.02398 0.18524 0.00134 2660.6 46.6 2608.8 102.3 2700.3 11.9 05KP42_005a 1 13.28749 0.68159 0.51302 0.02501 0.18786 0.00138 2700.3 47.3 2669.5 105.7 2723.5 12.1 05KP42_006a 1 12.18195 0.36873 0.47518 0.01389 0.18593 0.00077 2618.5 28.0 2506.3 60.4 2706.5 6.8 05KP42_007a 1 13.17143 0.38416 0.51594 0.01444 0.18515 0.00081 2692.0 27.2 2681.9 61.1 2699.6 7.2 05KP42_008a 1 13.24370 0.45339 0.51860 0.01711 0.18521 0.00094 2697.2 31.8 2693.3 72.2 2700.1 8.4 05KP42_009a 1 12.11039 0.37086 0.48298 0.01420 0.18185 0.00085 2613.0 28.3 2540.2 61.4 2669.9 7.8 05KP42_010a 1 12.95534 0.38586 0.51068 0.01461 0.18399 0.00082 2676.4 27.7 2659.5 62.1 2689.2 7.3 05KP42_011a 1 13.04422 0.38563 0.51445 0.01461 0.18390 0.00081 2682.9 27.5 2675.6 61.9 2688.3 7.3 05KP42_012a 1 12.56843 0.37067 0.49124 0.01388 0.18556 0.00085 2647.9 27.4 2576.0 59.7 2703.2 7.5 05KP42_013a 1 12.56782 0.36888 0.50033 0.01416 0.18218 0.00074 2647.8 27.2 2615.2 60.5 2672.8 6.7 05KP42_014a 1 13.37866 0.38735 0.52250 0.01456 0.18570 0.00077 2706.8 27.0 2709.8 61.3 2704.5 6.8 05KP42_015a 1 13.32378 0.41407 0.51486 0.01534 0.18768 0.00092 2702.9 28.9 2677.4 64.9 2722.0 8.0 05KP42_016a 1 12.51577 0.28603 0.49478 0.01035 0.18346 0.00097 2643.9 21.3 2591.3 44.5 2684.4 8.7 05KP42_017a 1 13.24918 0.22055 0.51811 0.00758 0.18547 0.00080 2697.6 15.6 2691.2 32.1 2702.4 7.1 05KP42_018a 1 14.77531 0.23576 0.54004 0.00757 0.19843 0.00080 2800.9 15.1 2783.6 31.6 2813.3 6.6 05KP42_019a 1 13.33625 0.29755 0.51499 0.01049 0.18782 0.00098 2703.8 20.9 2677.9 44.5 2723.1 8.5 05KP42_020a 1 13.46892 0.26408 0.51731 0.00913 0.18883 0.00090 2713.1 18.4 2687.8 38.7 2732.0 7.8 05KP42_021a 1 12.90641 0.32893 0.49858 0.01178 0.18774 0.00104 2672.8 23.7 2607.7 50.5 2722.5 9.1 05KP42_023a 1 12.74406 0.22009 0.50660 0.00777 0.18245 0.00078 2660.9 16.1 2642.1 33.2 2675.2 7.1 05KP42_024a 1 13.06952 0.30543 0.50703 0.01092 0.18695 0.00097 2684.7 21.8 2643.9 46.5 2715.5 8.5 05KP42_025a 1 12.71149 0.24550 0.50382 0.00869 0.18299 0.00090 2658.5 18.0 2630.2 37.1 2680.1 8.1 05KP42_026a 1 12.74649 0.40818 0.50130 0.01519 0.18441 0.00104 2661.1 29.7 2619.4 64.9 2693.0 9.2 05KP42_027a 1 13.37302 0.43663 0.50925 0.01581 0.19046 0.00103 2706.4 30.4 2653.4 67.2 2746.1 8.8 05KP42_028a 1 13.09991 0.41746 0.51089 0.01546 0.18597 0.00098 2686.9 29.6 2660.4 65.6 2706.8 8.7 05KP42_029a 1 12.87510 0.44399 0.50555 0.01658 0.18471 0.00108 2670.6 32.0 2637.6 70.6 2695.6 9.6 05KP42_030a 1 13.17713 0.40745 0.51772 0.01521 0.18460 0.00092 2692.4 28.8 2689.5 64.3 2694.6 8.3 05KP42_031a 1 12.34028 0.40812 0.49373 0.01548 0.18127 0.00104 2630.6 30.6 2586.8 66.5 2664.6 9.5 05KP42_032a 1 12.96138 0.41000 0.51208 0.01541 0.18357 0.00094 2676.8 29.4 2665.5 65.4 2685.4 8.4 05KP42_033a 1 12.14019 0.37524 0.47984 0.01407 0.18350 0.00094 2615.3 28.6 2526.5 61.0 2684.7 8.4 05KP42_034a 1 12.85142 0.44792 0.50056 0.01662 0.18621 0.00108 2668.8 32.3 2616.2 71.0 2708.9 9.6 05KP42_035a 1 13.04911 0.43992 0.51559 0.01646 0.18356 0.00110 2683.2 31.3 2680.5 69.6 2685.3 9.9 05KP42_036a 1 12.84269 0.39628 0.50258 0.01475 0.18533 0.00091 2668.2 28.7 2624.9 63.0 2701.2 8.1 05KP42_037a 1 12.23939 0.37585 0.48290 0.01407 0.18382 0.00093 2622.9 28.4 2539.9 60.9 2687.7 8.3 05KP42_038a 1 13.19496 0.36408 0.51140 0.01268 0.18713 0.00124 2693.7 25.7 2662.6 53.8 2717.1 10.9 05KP42_039a 1 30.32611 0.77368 0.71578 0.01643 0.30728 0.00177 3497.4 24.8 3480.2 61.4 3507.3 8.9 05KP42_039b 1 28.10176 0.66719 0.64940 0.01366 0.31384 0.00183 3422.7 23.0 3225.9 53.2 3539.9 8.9 05KP42_040a 1 13.27093 0.36048 0.51295 0.01258 0.18764 0.00117 2699.1 25.3 2669.2 53.4 2721.6 10.3

05KP42_041a 1 12.92067 0.35306 0.51197 0.01258 0.18304 0.00119 2673.9 25.4 2665.0 53.4 2680.6 10.7 35 Appendix 1 (continued). LA-ICP-MS data and calculated ages. 05KP42_042a 1 12.72705 0.36312 0.50410 0.01297 0.18311 0.00125 2659.7 26.5 2631.4 55.4 2681.2 11.2 05KP42_043a 1 12.93529 0.34346 0.51292 0.01221 0.18290 0.00116 2674.9 24.7 2669.1 51.8 2679.4 10.4 05KP42_044a 1 12.30685 0.38043 0.48814 0.01385 0.18285 0.00123 2628.1 28.6 2562.6 59.7 2678.9 11.1 05KP42_045a 1 12.99011 0.39365 0.51432 0.01423 0.18318 0.00125 2678.9 28.2 2675.0 60.3 2681.9 11.3 05KP42_046a 1 13.02201 0.35703 0.51432 0.01266 0.18363 0.00121 2681.2 25.5 2675.0 53.7 2685.9 10.9 05KP42_047a 1 13.43190 0.36061 0.51212 0.01235 0.19022 0.00121 2710.5 25.1 2665.7 52.4 2744.1 10.4 05KP42_049a 1 12.31331 0.26807 0.49117 0.00926 0.18181 0.00104 2628.6 20.2 2575.8 39.9 2669.5 9.4 05KP42_050a 1 13.49354 0.30500 0.51775 0.01018 0.18902 0.00113 2714.8 21.1 2689.6 43.1 2733.6 9.8 05KP42_051a 1 12.75044 0.33612 0.49943 0.01185 0.18516 0.00116 2661.4 24.5 2611.3 50.7 2699.6 10.3 05KP42_052a 1 12.92071 0.29696 0.50995 0.01025 0.18376 0.00110 2673.9 21.4 2656.4 43.6 2687.1 9.8 05KP42_053a 1 13.12126 0.39112 0.51481 0.01394 0.18485 0.00130 2688.4 27.7 2677.1 59.1 2696.9 11.6 05KP42_054a 1 12.99594 0.30122 0.50747 0.01027 0.18573 0.00113 2679.4 21.6 2645.8 43.8 2704.7 10.0 05KP42_055a 1 12.75456 0.30289 0.50409 0.01053 0.18351 0.00112 2661.7 22.1 2631.3 45.0 2684.8 10.0 05KP42_056a 1 14.60227 0.36860 0.52833 0.01181 0.20045 0.00130 2789.7 23.7 2734.4 49.6 2829.9 10.5 05KP42_057a 1 13.21915 0.31163 0.51021 0.01046 0.18791 0.00120 2695.4 22.0 2657.5 44.5 2723.9 10.5 05KP42_058a 1 12.97164 0.50736 0.51121 0.01853 0.18403 0.00163 2677.6 36.2 2661.8 78.5 2689.5 14.5 05KP42_060a 1 13.06301 0.47440 0.51293 0.01810 0.18470 0.00092 2684.2 33.7 2669.1 76.6 2695.6 8.2 05KP42_061a 1 13.30525 0.49997 0.51349 0.01872 0.18792 0.00102 2701.6 34.9 2671.5 79.2 2724.1 8.9 05KP42_063a 1 13.19854 0.50358 0.50970 0.01889 0.18780 0.00101 2694.0 35.4 2655.3 80.2 2723.0 8.8 05KP42_064a 1 13.06392 0.48505 0.51474 0.01860 0.18406 0.00091 2684.3 34.4 2676.8 78.7 2689.8 8.1 05KP42_065a 1 13.37663 0.49487 0.51334 0.01841 0.18898 0.00101 2706.6 34.4 2670.9 78.0 2733.3 8.8 05KP42_067a 1 13.40975 0.53380 0.52044 0.02008 0.18687 0.00112 2708.9 36.9 2701.0 84.6 2714.8 9.8 05KP42_068a 1 12.86658 0.61853 0.50076 0.02339 0.18635 0.00136 2669.9 44.3 2617.1 99.7 2710.2 12.0 05KP42_069a 1 13.54311 0.50114 0.51635 0.01853 0.19022 0.00101 2718.3 34.4 2683.7 78.3 2744.1 8.7 05KP42_070a 1 12.34667 0.45823 0.48530 0.01747 0.18451 0.00098 2631.1 34.3 2550.3 75.4 2693.9 8.8 05KP42_071a 1 12.52544 0.49135 0.49507 0.01885 0.18349 0.00104 2644.6 36.2 2592.6 80.8 2684.7 9.4 05KP42_073a 1 13.18092 0.35851 0.51061 0.01261 0.18722 0.00126 2692.7 25.4 2659.2 53.6 2717.9 11.0 05KP42_074a 1 13.61142 0.35857 0.51616 0.01235 0.19125 0.00122 2723.1 24.6 2682.9 52.3 2753.0 10.4 05KP42_075a 1 13.27143 0.33404 0.51764 0.01178 0.18594 0.00114 2699.2 23.5 2689.2 49.9 2706.6 10.0 05KP42_076a 1 13.13413 0.32888 0.51031 0.01156 0.18666 0.00113 2689.3 23.4 2657.9 49.2 2713.0 9.9 05KP42_078a 1 13.25210 0.35677 0.50367 0.01230 0.19082 0.00127 2697.8 25.1 2629.6 52.5 2749.2 10.9 05KP42_079a 1 13.59529 0.40801 0.51928 0.01442 0.18988 0.00128 2721.9 28.0 2696.1 60.9 2741.1 11.0 05KP42_080a 1 13.09030 0.33631 0.51473 0.01198 0.18444 0.00115 2686.2 24.0 2676.8 50.8 2693.2 10.3 05KP42_081a 1 12.48194 0.30983 0.49819 0.01116 0.18171 0.00110 2641.4 23.1 2606.0 47.9 2668.5 10.0 05KP42_082a 1 13.08383 0.39379 0.51799 0.01426 0.18319 0.00136 2685.7 28.0 2690.6 60.3 2682.0 12.2 05KP42_083a 1 13.28042 0.40968 0.52402 0.01327 0.18380 0.00174 2699.8 28.7 2716.2 55.9 2687.5 15.6 05KP42_084a 1 13.21633 0.46405 0.50511 0.01525 0.18976 0.00186 2695.2 32.6 2635.7 65.0 2740.1 16.0 05KP42_085a 1 13.59884 0.41909 0.53147 0.01349 0.18557 0.00173 2722.2 28.7 2747.6 56.5 2703.3 15.3 05KP42_086a 1 13.67893 0.75705 0.51320 0.02660 0.19331 0.00216 2727.7 51.1 2670.3 112.3 2770.5 18.3 05KP42_088a 1 13.18855 0.40647 0.51410 0.01308 0.18605 0.00172 2693.2 28.7 2674.1 55.4 2707.6 15.2 05KP42_089a 1 12.99641 0.42585 0.50514 0.01385 0.18659 0.00183 2679.4 30.4 2635.9 59.0 2712.4 16.1 05KP42_090a 1 13.28117 0.42819 0.51887 0.01397 0.18564 0.00178 2699.8 30.0 2694.4 59.0 2703.9 15.7 05KP42_091a 1 13.81985 0.47036 0.52949 0.01534 0.18929 0.00184 2737.4 31.7 2739.3 64.3 2736.0 15.9 05KP42_092a 1 12.74757 0.43736 0.50284 0.01471 0.18386 0.00180 2661.2 31.8 2626.0 62.8 2688.0 16.1 36 Appendix 1 (continued). LA-ICP-MS data and calculated ages. 05KP42_093a 1 13.45418 0.44187 0.52787 0.01460 0.18485 0.00177 2712.1 30.6 2732.5 61.3 2696.9 15.7 05KP42_094a 1 12.93597 0.40862 0.50326 0.01319 0.18642 0.00177 2675.0 29.3 2627.8 56.3 2710.8 15.5 05KP42_095a 1 12.82820 0.45702 0.50472 0.01294 0.18434 0.00239 2667.1 33.0 2634.1 55.2 2692.3 21.3 05KP42_096a 1 12.79773 0.42348 0.50056 0.01104 0.18543 0.00239 2664.9 30.7 2616.2 47.3 2702.0 21.1 05KP42_097a 1 14.04841 0.47868 0.53314 0.01252 0.19111 0.00247 2753.0 31.8 2754.7 52.4 2751.8 21.1 05KP42_098a 1 13.44044 0.46867 0.51987 0.01277 0.18751 0.00244 2711.1 32.4 2698.6 53.9 2720.4 21.3 05KP42_099a 1 13.13888 0.45759 0.51265 0.01264 0.18588 0.00239 2689.7 32.3 2667.9 53.6 2706.1 21.1 05KP42_100a 1 13.64631 0.45239 0.52834 0.01169 0.18733 0.00242 2725.5 30.9 2734.4 49.1 2718.9 21.2 05KP42_101a 1 14.83973 0.55849 0.53729 0.01516 0.20032 0.00264 2805.0 35.2 2772.1 63.3 2828.8 21.3 05KP42_102a 1 12.99430 0.42943 0.50868 0.01125 0.18527 0.00237 2679.2 30.7 2651.0 47.9 2700.7 21.0 05KP42_103a 1 13.17966 0.43934 0.51579 0.01160 0.18532 0.00238 2692.6 31.0 2681.3 49.1 2701.1 21.1 05KP42_104a 1 12.86707 0.43205 0.49955 0.01141 0.18681 0.00240 2670.0 31.2 2611.9 48.8 2714.3 21.1 05KP42_105a 1 12.88129 0.43222 0.50234 0.01146 0.18598 0.00239 2671.0 31.1 2623.9 49.0 2706.9 21.1 05KP42_106a 1 12.35103 0.41384 0.48735 0.01106 0.18381 0.00237 2631.5 31.0 2559.2 47.8 2687.5 21.2 05KP42_107a 1 13.34037 0.47102 0.51462 0.01293 0.18801 0.00245 2704.0 32.8 2676.3 54.8 2724.8 21.3 05KP42_109a 1 13.76219 0.68192 0.52504 0.02055 0.19008 0.00303 2733.5 45.9 2720.5 86.3 2742.9 26.0 05KP42_110a 1 13.05987 0.64648 0.51381 0.02005 0.18432 0.00295 2684.0 45.6 2672.9 84.8 2692.1 26.2 05KP42_111a 1 13.55763 0.64077 0.50544 0.01837 0.19451 0.00305 2719.3 43.7 2637.1 78.2 2780.7 25.5 05KP42_112a 1 14.29155 0.69006 0.52467 0.01970 0.19753 0.00313 2769.3 44.8 2719.0 82.8 2805.9 25.7 05KP42_113a 1 13.07585 0.62440 0.50622 0.01875 0.18731 0.00293 2685.1 44.1 2640.5 79.8 2718.7 25.5 05KP42_115a 1 12.68639 0.62372 0.49514 0.01914 0.18580 0.00296 2656.7 45.2 2592.9 82.0 2705.3 26.0 05KP42_116a 1 13.05351 0.68708 0.50264 0.02162 0.18833 0.00301 2683.5 48.5 2625.1 92.1 2727.6 26.1 05KP42_117a 1 13.26815 0.63069 0.51051 0.01873 0.18847 0.00296 2698.9 43.9 2658.8 79.4 2728.9 25.6 05KP42_118a 1 13.29074 0.66236 0.51115 0.02017 0.18856 0.00301 2700.5 46.0 2661.5 85.5 2729.6 26.1 05KP42_119a 1 14.17779 0.72035 0.53501 0.02180 0.19217 0.00306 2761.7 47.1 2762.5 90.9 2760.8 25.9 05KP42_120a 1 12.99544 0.66561 0.50106 0.02055 0.18808 0.00306 2679.3 47.2 2618.3 87.6 2725.4 26.5 > 10% discordant Ratios Ages 207 235 206 238 207 206 207 235 206 238 207 206 Spot # Session Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ 05KP42_022a 1 10.140660 0.177014 0.399133 0.005803 0.184265 0.001039 2447.7 16.0 2165.0 26.7 2691.6 9.3 05KP42_048a 1 10.083448 0.232156 0.394703 0.007893 0.185280 0.001148 2442.5 21.0 2144.6 36.4 2700.7 10.2 05KP42_062a 2 8.779221 0.490175 0.340355 0.018768 0.187072 0.000992 2315.3 49.7 1888.4 89.6 2716.6 8.7 05KP42_066a 1 10.524384 0.416304 0.407648 0.015563 0.187240 0.001207 2482.1 36.0 2204.2 70.9 2718.1 10.6 05KP42_072a 1 11.174119 0.284665 0.429405 0.009887 0.188725 0.001181 2537.8 23.5 2303.0 44.4 2731.1 10.3 05KP42_072b 1 9.946176 0.261265 0.390345 0.009300 0.184796 0.001185 2429.8 24.0 2124.4 43.0 2696.4 10.5 05KP42_077a 1 11.923848 0.305884 0.454103 0.010555 0.190434 0.001184 2598.4 23.8 2413.5 46.6 2745.9 10.2 05KP42_087a 1 11.657765 0.380156 0.451871 0.012387 0.187105 0.001780 2577.3 30.0 2403.6 54.8 2716.9 15.6 05KP42_108a 1 10.064828 0.477218 0.402492 0.014722 0.181337 0.002839 2440.7 42.9 2180.5 67.3 2665.1 25.7 05KP42_114a 1 10.106288 0.495808 0.392457 0.015153 0.186740 0.002949 2444.5 44.3 2134.2 69.8 2713.7 25.8 37 Appendix 2. Laser ablation U-Pb data and calculated ages for detrital zircons from the Tyler Formation (KP05-40). < 10% Discordant Ratios Ages 207 235 206 238 207 206 207 235 206 238 207 206 Spot # Session Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ 05KP40_002 1 12.70683 0.22197 0.49694 0.00666 0.18677 0.00157 2658.2 16.3 2600.6 28.6 2714.0 13.8 05KP40_003 1 5.24677 0.09112 0.34473 0.00456 0.11117 0.00094 1860.2 14.7 1909.4 21.8 1818.7 15.3 05KP40_004 1 5.23664 0.09044 0.33875 0.00442 0.11291 0.00097 1858.6 14.6 1880.7 21.2 1846.8 15.5 05KP40_005 1 5.23308 0.10105 0.33743 0.00519 0.11328 0.00103 1858.0 16.3 1874.3 24.9 1852.7 16.3 05KP40_007 1 12.52343 0.23290 0.50695 0.00748 0.18044 0.00154 2644.5 17.3 2643.6 31.9 2656.9 14.1 05KP40_008 1 16.03968 0.29061 0.54350 0.00766 0.21557 0.00186 2879.2 17.2 2798.1 31.9 2947.9 13.9 05KP40_009 1 5.12805 0.09275 0.33589 0.00467 0.11151 0.00099 1840.8 15.3 1866.9 22.5 1824.2 16.1 05KP40_010 1 5.21343 0.09480 0.33746 0.00475 0.11284 0.00099 1854.8 15.4 1874.4 22.9 1845.7 15.8 05KP40_011a 1 5.17331 0.10855 0.33336 0.00680 0.11255 0.00046 1848.2 17.7 1854.6 32.8 1841.1 7.4 05KP40_013a 1 16.63081 0.34264 0.55818 0.01120 0.21610 0.00080 2913.8 19.5 2859.1 46.2 2951.8 6.0 05KP40_014a 1 4.87216 0.10305 0.30922 0.00638 0.11428 0.00043 1797.5 17.7 1736.9 31.3 1868.5 6.8 05KP40_016a 1 5.02381 0.10948 0.31998 0.00673 0.11387 0.00058 1823.3 18.3 1789.6 32.8 1862.1 9.2 05KP40_017a 1 11.95688 0.24047 0.46293 0.00902 0.18733 0.00080 2601.0 18.7 2452.5 39.6 2718.9 7.0 05KP40_019a 1 5.21239 0.10856 0.33741 0.00683 0.11204 0.00046 1854.6 17.6 1874.2 32.8 1832.8 7.5 05KP40_020a 1 5.15351 0.10855 0.31311 0.00638 0.11937 0.00055 1845.0 17.8 1756.0 31.3 1946.9 8.2 05KP40_021a 1 12.87565 0.26053 0.48013 0.00951 0.19449 0.00072 2670.6 18.9 2527.8 41.3 2780.5 6.0 05KP40_023 1 5.16018 0.08694 0.32600 0.00530 0.11480 0.00047 1846.1 14.2 1818.9 25.7 1876.8 7.3 05KP40_024 1 12.69808 0.21297 0.50896 0.00828 0.18094 0.00066 2657.5 15.7 2652.2 35.3 2661.5 6.1 05KP40_026 1 5.35719 0.08520 0.33884 0.00521 0.11467 0.00042 1878.0 13.5 1881.1 25.0 1874.7 6.6 05KP40_027 1 5.37156 0.08944 0.34525 0.00553 0.11284 0.00048 1880.3 14.2 1911.9 26.4 1845.6 7.7 05KP40_028 1 12.84812 0.22373 0.50441 0.00850 0.18473 0.00076 2668.6 16.3 2632.7 36.3 2695.8 6.7 05KP40_029 1 12.06887 0.19514 0.49773 0.00781 0.17586 0.00061 2609.8 15.0 2604.0 33.5 2614.2 5.7 05KP40_030 1 5.12580 0.08555 0.32958 0.00530 0.11280 0.00047 1840.4 14.1 1836.3 25.6 1845.0 7.6 05KP40_031a 1 13.44816 0.19053 0.52894 0.00730 0.18439 0.00053 2711.6 13.3 2737.0 30.7 2692.8 4.7 05KP40_032a 1 5.31967 0.08206 0.32487 0.00481 0.11876 0.00052 1872.0 13.1 1813.5 23.3 1937.6 7.8 05KP40_033a 1 5.16985 0.07656 0.32880 0.00468 0.11404 0.00046 1847.7 12.5 1832.6 22.7 1864.7 7.3 05KP40_034a 1 11.94348 0.16652 0.50230 0.00680 0.17245 0.00054 2600.0 13.0 2623.7 29.1 2581.5 5.2 05KP40_035a 1 5.17661 0.07517 0.32994 0.00459 0.11379 0.00048 1848.8 12.3 1838.1 22.2 1860.8 7.6 05KP40_036a 1 5.06211 0.07208 0.33014 0.00453 0.11121 0.00041 1829.8 12.0 1839.0 21.9 1819.2 6.7 05KP40_038a 1 5.28677 0.07235 0.33912 0.00451 0.11306 0.00034 1866.7 11.6 1882.4 21.7 1849.2 5.4 05KP40_039a 1 5.21331 0.07319 0.32818 0.00448 0.11521 0.00034 1854.8 11.9 1829.5 21.7 1883.2 5.4 05KP40_040a 1 5.31044 0.07944 0.33170 0.00477 0.11611 0.00047 1870.5 12.7 1846.6 23.1 1897.2 7.2 05KP40_041a 1 5.16987 0.09591 0.32654 0.00587 0.11482 0.00050 1847.7 15.7 1821.6 28.4 1877.1 7.9 05KP40_042a 1 11.92962 0.21413 0.49308 0.00867 0.17547 0.00054 2598.9 16.7 2584.0 37.3 2610.5 5.1 05KP40_043a 1 5.13096 0.09122 0.32942 0.00571 0.11296 0.00040 1841.2 15.0 1835.6 27.6 1847.6 6.4 05KP40_044a 1 5.38655 0.10038 0.33728 0.00611 0.11583 0.00047 1882.7 15.8 1873.6 29.4 1892.8 7.2 05KP40_045a 1 5.15707 0.09653 0.33032 0.00603 0.11323 0.00043 1845.6 15.8 1839.9 29.1 1851.9 6.8 05KP40_046a 1 4.96497 0.09398 0.32298 0.00595 0.11149 0.00045 1813.4 15.9 1804.3 28.9 1823.8 7.3 05KP40_047a 1 5.00848 0.09257 0.31894 0.00575 0.11389 0.00041 1820.8 15.5 1784.6 28.1 1862.4 6.4 05KP40_048a 1 5.03336 0.09608 0.32208 0.00599 0.11334 0.00044 1825.0 16.0 1799.9 29.2 1853.6 7.0 05KP40_049a 1 5.02906 0.09446 0.32582 0.00598 0.11194 0.00039 1824.2 15.8 1818.1 29.0 1831.2 6.3

05KP40_051a 1 14.47960 0.24413 0.52858 0.00842 0.19868 0.00095 2781.7 15.9 2735.5 35.4 2815.4 7.8 38 Appendix 2 (continued). LA-ICP-MS data and calculated ages. 05KP40_052a 1 4.87302 0.08238 0.31305 0.00501 0.11290 0.00052 1797.6 14.1 1755.7 24.6 1846.6 8.3 05KP40_053a 1 4.69490 0.08070 0.29805 0.00485 0.11425 0.00054 1766.3 14.3 1681.6 24.1 1868.0 8.5 05KP40_054a 1 5.17614 0.09001 0.32282 0.00526 0.11629 0.00064 1848.7 14.7 1803.5 25.6 1900.0 9.9 05KP40_055a 1 5.09196 0.08541 0.32353 0.00511 0.11415 0.00056 1834.8 14.1 1807.0 24.8 1866.5 8.9 05KP40_060a 1 10.76718 0.18718 0.46813 0.00772 0.16681 0.00078 2503.2 16.0 2475.4 33.8 2525.9 7.8 05KP40_061a 1 5.17514 0.07067 0.33328 0.00392 0.11262 0.00067 1848.5 11.6 1854.2 18.9 1842.1 10.7 05KP40_062a 1 5.00890 0.07002 0.32336 0.00387 0.11234 0.00072 1820.8 11.8 1806.1 18.8 1837.6 11.5 05KP40_063a 1 4.95037 0.06805 0.32148 0.00378 0.11168 0.00069 1810.9 11.5 1797.0 18.4 1826.9 11.2 05KP40_064a 1 4.88464 0.06411 0.31551 0.00356 0.11228 0.00063 1799.6 11.0 1767.8 17.4 1836.7 10.2 05KP40_065a 1 5.08199 0.07245 0.32668 0.00399 0.11282 0.00074 1833.1 12.0 1822.3 19.4 1845.4 11.7 05KP40_066a 1 5.19566 0.07361 0.32164 0.00389 0.11715 0.00077 1851.9 12.0 1797.7 18.9 1913.3 11.8 05KP40_067a 1 4.96639 0.06708 0.31983 0.00372 0.11262 0.00065 1813.6 11.4 1788.9 18.2 1842.1 10.5 05KP40_068a 1 5.00443 0.06390 0.32334 0.00349 0.11225 0.00065 1820.1 10.7 1806.0 17.0 1836.1 10.5 05KP40_069a 1 5.07497 0.06955 0.32230 0.00381 0.11420 0.00068 1831.9 11.6 1800.9 18.6 1867.3 10.7 05KP40_072a 1 5.05905 0.08512 0.32321 0.00484 0.11352 0.00083 1829.3 14.2 1805.4 23.5 1856.5 13.1 05KP40_073a 1 5.05149 0.07259 0.32391 0.00416 0.11310 0.00063 1828.0 12.1 1808.8 20.2 1849.9 10.1 05KP40_075a 1 5.06866 0.07455 0.32208 0.00425 0.11414 0.00065 1830.9 12.4 1799.9 20.7 1866.3 10.2 05KP40_076a 1 11.80071 0.17688 0.48191 0.00656 0.17760 0.00095 2588.7 13.9 2535.6 28.5 2630.5 8.8 05KP40_077a 1 5.02898 0.07012 0.32425 0.00405 0.11248 0.00059 1824.2 11.7 1810.4 19.7 1839.9 9.5 05KP40_078a 1 13.22173 0.20743 0.50893 0.00728 0.18841 0.00105 2695.6 14.7 2652.1 31.0 2728.4 9.2 05KP40_079a 1 4.93638 0.07729 0.31978 0.00449 0.11196 0.00070 1808.5 13.1 1788.6 21.9 1831.4 11.4 05KP40_080a 1 5.03154 0.09205 0.32309 0.00541 0.11294 0.00077 1824.6 15.4 1804.8 26.3 1847.3 12.3 05KP40_080b 1 5.32460 0.09965 0.33313 0.00563 0.11592 0.00090 1872.8 15.9 1853.5 27.2 1894.2 13.9 05KP40_081a 1 5.05250 0.06996 0.32548 0.00421 0.11258 0.00050 1828.2 11.7 1816.4 20.5 1841.5 8.0 05KP40_082a 1 4.88549 0.07067 0.31414 0.00427 0.11279 0.00050 1799.8 12.1 1761.1 20.9 1844.8 8.0 05KP40_083a 1 5.05713 0.07284 0.32305 0.00437 0.11353 0.00051 1828.9 12.1 1804.6 21.2 1856.7 8.2 05KP40_084a 1 4.81098 0.06944 0.30867 0.00417 0.11304 0.00052 1786.8 12.1 1734.2 20.5 1848.8 8.3 05KP40_085a 1 5.05382 0.07157 0.32086 0.00424 0.11423 0.00054 1828.4 11.9 1793.9 20.6 1867.8 8.5 05KP40_086a 1 4.88052 0.07049 0.31503 0.00429 0.11236 0.00048 1798.9 12.1 1765.4 21.0 1837.9 7.8 05KP40_087a 1 5.22821 0.07674 0.33517 0.00460 0.11313 0.00054 1857.2 12.4 1863.4 22.2 1850.3 8.6 05KP40_089a 1 20.93041 0.34808 0.61360 0.00969 0.24739 0.00119 3135.4 16.0 3084.4 38.6 3168.1 7.6 05KP40_090a 1 8.63880 0.15518 0.40408 0.00685 0.15505 0.00089 2300.7 16.2 2187.8 31.4 2402.4 9.7 05KP40_091a 1 5.07882 0.06528 0.32746 0.00366 0.11249 0.00062 1832.6 10.8 1826.1 17.8 1840.0 10.0 05KP40_092a 1 5.09611 0.06803 0.33172 0.00388 0.11142 0.00063 1835.5 11.3 1846.7 18.8 1822.7 10.2 05KP40_094a 1 4.88120 0.06670 0.31760 0.00377 0.11147 0.00069 1799.0 11.5 1778.0 18.4 1823.5 11.1 05KP40_096a 1 5.35843 0.06872 0.33419 0.00375 0.11629 0.00062 1878.2 10.9 1858.7 18.1 1900.0 9.5 05KP40_097a 1 5.05363 0.06381 0.32384 0.00354 0.11318 0.00062 1828.4 10.6 1808.4 17.2 1851.1 9.9 05KP40_098a 1 4.92435 0.06341 0.31637 0.00352 0.11289 0.00065 1806.4 10.8 1772.0 17.2 1846.4 10.4 05KP40_099a 1 11.52983 0.15075 0.47958 0.00548 0.17437 0.00097 2567.0 12.1 2525.4 23.8 2600.0 9.2 05KP40_100b 1 13.11024 0.19407 0.50958 0.00674 0.18659 0.00110 2687.6 13.9 2654.9 28.7 2712.4 9.7 05KP40_101a 1 5.20950 0.22555 0.33345 0.01423 0.11332 0.00070 1854.2 36.2 1855.1 68.4 1853.3 11.1 05KP40_103a 1 5.24494 0.22019 0.33394 0.01389 0.11392 0.00042 1860.0 35.2 1857.5 66.8 1862.9 6.6 05KP40_105a 1 4.95527 0.20781 0.31935 0.01326 0.11255 0.00045 1811.7 34.8 1786.6 64.5 1840.9 7.2

05KP40_106a 1 5.11106 0.21427 0.32683 0.01357 0.11343 0.00046 1837.9 35.0 1823.0 65.6 1855.1 7.3 39 Appendix 2 (continued). LA-ICP-MS data and calculated ages. 05KP40_107a 1 10.11981 0.42434 0.43423 0.01804 0.16904 0.00063 2445.8 38.0 2324.7 80.6 2548.2 6.3 05KP40_108a 1 5.11557 0.21416 0.32898 0.01365 0.11279 0.00040 1838.7 34.9 1833.4 65.9 1844.8 6.3 05KP40_109a 1 5.14587 0.21625 0.32985 0.01372 0.11316 0.00047 1843.7 35.1 1837.6 66.2 1850.7 7.5 05KP40_110a 1 5.17621 0.22052 0.32067 0.01350 0.11708 0.00060 1848.7 35.6 1793.0 65.6 1912.1 9.2 05KP40_111a 1 6.10005 0.08071 0.35513 0.00426 0.12458 0.00070 1990.3 11.5 1959.1 20.2 2022.8 9.9 05KP40_112a 1 4.76079 0.04926 0.30512 0.00287 0.11316 0.00044 1778.0 8.6 1716.6 14.2 1850.8 7.1 05KP40_113a 1 5.15994 0.05587 0.32774 0.00323 0.11419 0.00048 1846.0 9.2 1827.4 15.6 1867.1 7.5 05KP40_114a 1 5.05879 0.05480 0.32279 0.00314 0.11367 0.00052 1829.2 9.1 1803.3 15.3 1858.8 8.2 05KP40_115a 1 5.04032 0.04994 0.32004 0.00282 0.11423 0.00048 1826.1 8.4 1789.9 13.7 1867.7 7.6 05KP40_116a 1 5.09800 0.04890 0.32686 0.00282 0.11312 0.00043 1835.8 8.1 1823.1 13.7 1850.1 6.8 05KP40_117a 1 5.22667 0.05865 0.33632 0.00340 0.11271 0.00053 1857.0 9.5 1868.9 16.4 1843.6 8.5 05KP40_118a 1 5.02115 0.05065 0.32363 0.00294 0.11253 0.00046 1822.9 8.5 1807.4 14.3 1840.6 7.3 05KP40_119a 1 5.28538 0.05099 0.33522 0.00291 0.11435 0.00043 1866.5 8.2 1863.7 14.1 1869.7 6.7 05KP40_120a 1 12.67185 0.12360 0.50207 0.00442 0.18305 0.00069 2655.6 9.1 2622.7 18.9 2680.7 6.3 > 10% discordant Ratios Ages 207 235 206 238 207 206 207 235 206 238 207 206 Spot # Session Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ 05KP40_001 1 14.584534 0.255710 0.497235 0.006658 0.214246 0.001836 2788.5 16.5 2601.9 28.6 2937.9 13.8 05KP40_006 1 4.523117 0.105841 0.234809 0.004664 0.140703 0.001389 1735.2 19.3 1359.7 24.3 2235.9 17.0 05KP40_012a 1 4.434616 0.096050 0.285790 0.005995 0.112542 0.000526 1718.8 17.8 1620.5 30.0 1840.9 8.4 05KP40_015a 1 4.752484 0.102777 0.283913 0.005979 0.121406 0.000491 1776.5 18.0 1611.0 30.0 1977.0 7.2 05KP40_018a 1 4.685317 0.099290 0.294791 0.006069 0.115274 0.000485 1764.6 17.6 1665.4 30.1 1884.2 7.6 05KP40_022 2 10.156958 0.196980 0.415018 0.007874 0.177496 0.000620 2449.2 17.8 2237.8 35.8 2629.6 5.8 05KP40_025 1 4.319595 0.087561 0.283334 0.005617 0.110570 0.000414 1697.1 16.6 1608.1 28.2 1808.8 6.8 05KP40_059a 1 8.553007 0.159239 0.311170 0.005363 0.199352 0.001345 2291.6 16.8 1746.5 26.3 2820.9 11.0 05KP40_070a 1 4.211209 0.057027 0.280276 0.003278 0.108970 0.000630 1676.2 11.1 1592.8 16.5 1782.3 10.5 05KP40_071a 1 4.505377 0.087597 0.289186 0.005114 0.112990 0.000882 1732.0 16.0 1637.5 25.5 1848.1 14.1 05KP40_102a 1 11.314318 0.482308 0.422487 0.017795 0.194244 0.000994 2549.4 39.0 2271.8 80.1 2778.4 8.4 05KP40_104a 1 4.782050 0.201308 0.299273 0.012458 0.115899 0.000545 1781.8 34.8 1687.7 61.5 1893.9 8.4 Culled Ratios Ages 207 235 206 238 207 206 207 235 206 238 207 206 Spot # Session Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ Pb/ U ± 2 σ Pb/ U ± 2 σ Pb/ Pb ± 2 σ 05KP40_037a 4 14.325896 0.542738 0.429215 0.010811 0.242069 0.007587 2771.5 35.3 2302.2 48.6 3133.6 49.0 05KP40_050a 4 7.014132 0.166128 0.344053 0.007225 0.147855 0.001741 2113.2 20.8 1906.1 34.6 2321.3 20.1 05KP40_056a 4 3.590635 0.077636 0.184118 0.003532 0.141441 0.001457 1547.5 17.0 1089.4 19.2 2244.9 17.7 05KP40_057a 4 4.619420 0.078816 0.292317 0.004719 0.114613 0.000543 1752.8 14.1 1653.1 23.5 1873.8 8.5 05KP40_058a 4 13.064812 0.239154 0.502672 0.008746 0.188503 0.000930 2684.3 17.1 2625.3 37.4 2729.1 8.1 05KP40_074a 4 4.618056 0.089336 0.246352 0.004411 0.135953 0.000921 1752.5 16.0 1419.6 22.8 2176.3 11.8 05KP40_088a 4 10.286856 0.235026 0.315960 0.004264 0.236124 0.004845 2460.9 20.9 1770.0 20.9 3094.0 32.4 05KP40_093a 4 6.599680 0.116519 0.323682 0.005067 0.147877 0.001185 2059.3 15.4 1807.7 24.6 2321.5 13.7 40