USGS Professional Paper 1709-F - USGS Publications Warehouse

Studies by the U.S. Geological Survey in Alaska, 2004 U.S. Geological Survey Professional Paper 1709–F

Constraints on the Age and Provenance of the Chugach Accretionary Complex from Detrital Zircons in the Sitka Graywacke near Sitka, Alaska By Peter J. Haeussler, George E. Gehrels1, and Susan M. Karl

Abstract

Introduction

The Sitka Graywacke is the westernmost and youngest unit of the Chugach accretionary complex in southeastern Alaska. Using laser-ablation inductively coupled plasma mass spectroscopy, we obtained 492 detrital-zircon ages on seven typical samples of Sitka Graywacke turbidites, which were collected in a transect across much of the unit near Sitka, Alaska. Individual grains range in age from 66 to 1,802 m.y. The youngest peak ages on relative-probability plots of the western four samples (74, 72, 74, and 74 m.y., from west to east) are distinctly younger than the youngest peak ages of the eastern three samples (105, 103, and 97 m.y., from west to east). These youngest peak ages set maximum depositional ages for each sample. We suggest that these peak ages are not significantly older (within ∼5 m.y.) than the depositional age of the Sitka Graywacke because the deposits accumulated in a trench along a convergent margin, where magmatic sources likely continuously introduced juvenile zircons. The differences in the youngest cluster of detrital-zircon ages between the eastern and western sample localities is likely due to both a change in provenance and a fault. The similarity of the youngest peak ages in the Sitka Graywacke to fossil ages in the Valdez Group, in Prince William Sound, implies that the western part of the Sitka Graywacke is correlative with the Valdez Group, as previously inferred. However, the eastern part of the Sitka Graywacke has youngest detrital-zircon ages older than fossil ages in the Valdez Group and younger than fossil ages in the McHugh Complex, which in southcentral Alaska is the oldest part of the accretionary complex. The age distribution of zircons in the older, eastern sequence suggests sources along the British Columbia margin. The detrital-zircon ages in the younger, western sequence are similar to igneous ages from south-central Alaska to southern British Columbia. Rightlateral strike slip on various fault systems inboard of the Sitka Graywacke implies that it lay to the south when it was deposited and offscraped. Thus, although source areas as far north as the St. Elias Mountains and south-central Alaska are possible, they were most likely in coastal and interior British Columbia.

Graywacke turbidites are notoriously poor in fossils, and so dating turbidite sequences can be a great challenge. The Sitka Graywacke, which lies along the west coast of southeastern Alaska, is one such turbidite sequence (Berg and Hinckley, 1963; Loney and others, 1963; Decker and others, 1979; Decker, 1980). The unit is part of a Mesozoic through early Tertiary accretionary complex rimming southern Alaska (fig. 1; Plafker and others, 1977) that is commonly referred to as the Chugach terrane (for example, Plafker and others, 1994). Various workers (Nilsen and Moore, 1979; Nilsen and Zuffa, 1982; Plafker and others, 1994) have proposed that these accretionary-complex turbidites were deposited by northward-flowing trench-parallel turbidity currents derived from erosion of the Coast Mountains of southeastern Alaska and British Columbia. Regional correlations between the Sitka Graywacke and other units of the Chugach accretionary complex are hindered by the absence of fossils in the turbidites. Thus far, only two fossils have been identified from the Sitka Graywacke. Reifenstuhl (1986) obtained a gastropod with a nondiagnostic age ranging from Silurian to Eocene. Also, a small limestone pod, with sharp contacts, in graywacke (at the location of our sample 65, fig. 2) contained a poorly preserved cone-shaped nasselarian radiolarian of possible Jurassic age (C.D. Blome, written commun., 1994). Detrital-zircon ages can provide a maximum depositional age because the host sediment must have been laid down after the youngest detrital-zircon grain crystallized. In this study, we use the youngest ages from sandstone of the Sitka Greywacke to constrain depositional ages, subdivide the unit, and interpret the provenance of the detrital-zircon grains on the basis of a comparison with the ages of potential igneous source rocks along the northern Cordilleran margin.

Department of Geosciences, University of Arizonia, Tucson.

1

Methods We collected seven samples in an east-west-trending transect across much of the Sitka Graywacke near Sitka, Alaska (fig. 2; table 1). All samples were collected from normally

Constraints on the Age and Provenance of the Chugach Accretionary Complex, Alaska

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integrations with the laser firing, and a 30-s delay to purge the previous sample and prepare for the next analysis. Common Pb correction was made by using the measured 204Pb content and assuming an initial Pb composition from Stacey and Kramers (1975) (with uncertainties of ±1.0 for 206Pb/204Pb ratio and ±0.3 for 207Pb/204Pb ratio). Our 204Pb measurement is unaffected by the presence of 204Hg because backgrounds are measured on peaks (thereby subtracting any background 204Hg and 204Pb) and only trace Hg was present in the Ar gas. Interelement fractionation of Pb/U is generally 1.2 b.y. A total of 69 to 75 ages were determined for each of the seven samples. Age interpretations for the analyses are based largely on 206Pb/238U ages. 206Pb/207Pb ages for these relatively young zircons are much less reliable given the low 207Pb content. As a result, discordance on an individual-grain basis cannot be assessed for grains younger than 1.2 b.y. Thus, 206Pb/207Pb ages were used for a total of four grains older than 1.2 b.y. The U-Pb ages are plotted as histograms with a normalized relative-probability distribution in figure 3 (Ludwig, 2003), where the relative height of peaks corresponds to the significance of that age population.

in ages at this locality is much younger—74 m.y. This detritalzircon age helps constrain the loose fossil age. The youngest peak ages of the western four samples (74, 72, 74, and 74 m.y., from west to east) are distinctly younger 135°30' 57°05'

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We interpret the youngest cluster of detrital-zircon ages as setting a limiting depositional age for that sample. The youngest cluster is used, rather than the youngest individual grain, because isotopic disturbance by Pb loss can yield detrital-zircon ages that are significantly younger than the crystallization age but still analytically concordant. Because each zircon in a group of grains would almost certainly not lose exactly enough Pb to yield similar ages, we interpret the peak age of the youngest cluster (determined from the relativeprobability plots in fig. 3) as a robust indicator of the age of the youngest igneous source, accordingly setting a maximum depositional age for the host graywacke. The detrital-zircon ages indicate that the possible Jurassic nasselarian from the outcrop at sample locality 65, mentioned previously, is likely younger than Jurassic. The youngest peak

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Figure 2. Study area near Sitka, Alaska, showing regional geology simplified from Karl and others (in press). Squares, location of detrital zircon samples. Samples 62 and 65 are on small islands hidden beneath symbol. Irregular dashed line, inferred thrust fault (teeth on upper plate) between samples 65 and 66 that separates older, eastern samples from younger, western samples. Units: Jd, Jurassic diorite; Kjkk and Trsv, Jurassic through Cretaceous and Triassic parts of the Kelp Bay Group, respectively; Ks, Cretaceous Sitka Graywacke; Qu, Quaternary sedimentary rocks, undivided; Teg, Eocene granitic rocks. From U.S. Geological Survey Sitka A–4 and Port Alexander D–5 1:63,360-scale maps.


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Figure 3. Detrital-zircon histograms (gray bars) and relative-probability plots (solid curve) for samples 62 (A), 63 (B), 64 (C), 65 (D), 66 (E), 67 (F), and 69 (G). Left plot shows complete age range from 0 to 1,850 m.y., with a 50-m.y. bar width; right plot shows detailed area from 50 to 250 m.y., with a 5-m.y. bar width. All plots calculated with Isoplot software (Ludwig, 2003).

Results and Discussion

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than the youngest peak ages of the eastern three samples (105, 103, and 97 m.y., from west to east; figs. 2, 3; tables 1, 2). Interpretation of these limiting ages depends on the time interval between crystallization and deposition of the zircons, which would largely be influenced by the presence or absence of igneous sources, the rate of exhumation of source terrains, and the geometry and efficiency of depositional systems. We suggest that the youngest peak ages are close to the depositional age of the Sitka Graywacke. A subduction zone with associated arc magmatism was active along the western margin of North America during Late Cretaceous through early Tertiary time (for example, Miller, 1994; Moll-Stalcup and others, 1994; Plafker and others, 1994; Breitsprecher and Mortensen, 2004a, b), and so numerous sources of juvenile

zircons were present. Also occurring at that time was rapid uplift of the Coast Mountains of southeastern Alaska and British Columbia (for example, Hollister, 1982; Crawford and others, 2000; McClelland and Mattinson, 2000), which would have provided additional sources of young zircons. Moreover, because the Chugach terrane turbidites are considered to have been deposited by northward-flowing currents in the paleotrench (Nilsen and Moore, 1979; Nilsen and Zuffa, 1982; Plafker and others, 1994), little time intervened between deposition and accretion of the trench sediment. Taking these considerations together, we infer little time, possibly ≤5 m.y, between crystallization and deposition of the detrital zircons. Thus, these detritalzircon limiting ages would indicate a range in the maximum age of these Sitka Graywacke samples from ∼72 to ∼105 m.y.

Constraints on the Age and Provenance of the Chugach Accretionary Complex, Alaska The difference in the youngest peak ages between the eastern three and western four sample localities may be due to both a change in provenance and a fault. Histograms and relative-probability plots of detrital-zircon ages from the eastern and western samples differ (fig. 3), and so the two population groups are here considered separately. Because the two groups appear to be internally similar, we combined the data for the western four and eastern three samples (fig. 4). Because the patterns of the combined histograms and relative-probability plots differ for the two groups, the provenance must have changed. Is the difference between the two areas due only to a change in provenance? If so, then the entire sampling area would consist of a single stratigraphic section more than 15 km thick. Such a great thickness of a single panel in an accretionary complex would be extremely unusual. The overall westward-younging pattern of the youngest detrital-zircon ages is consistent with the standard model of accretionary prisms, which has trenchward-younging, fault-bounded panels of accreted sediment. Moreover, intraformational thrust faults are nearly ubiquitous in Chugach terrane turbidites (for example, Sample and Moore, 1987). Numerous faults occur within the

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Sitka Graywacke, most of which bound thrust panels and others of which are later-stage right-lateral strike-slip faults (Davis and others, 1998; Karl and others, in press). No previous fault was mapped between the western and eastern localities, and no obvious sedimentologic differences exist. We infer a fault, probably a thrust fault, in an uncertain location between the eastern three and western four sample localities (fig. 2). The detrital-zircon limiting ages for the Sitka Graywacke allow comparison and correlation to other parts of the Chugach accretionary complex in southern Alaska. The Valdez Group comprises the largest area of the Chugach terrane in southcentral Alaska (fig. 1). The western four samples of Sitka Graywacke have youngest peak ages of late Campanian (fig. 6) on the time scale of Gradstein and others (2005). Assuming that the detrital zircons were deposited within several million years of crystallization, they indicate that the western part of the Sitka Graywacke is correlative with the Valdez Group (fig. 6; Grant and Higgins, 1910; Tysdal and Plafker, 1978). All reliable fossil ages from the Valdez Group are Maastrichtian (65.5–70.6 m.y.; Tysdal and Plafker, 1978; Nelson and others, 1985), although two samples have questionable age calls

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Results and Discussion that are Campanian-Maastrichtian (65.5–83.5 m.y.; Tysdal and Plafker, 1978; Winkler, 1992). If less than 5 m.y. intervened between crystallization and deposition of the western Sitka Graywacke samples, they would be Maastrichtian. The younger part of the Sitka Graywacke also appears to be correlative with the upper part of the Yakutat Group of Tarr and Butler (1909). The Yakutat Group consists broadly of an eastern, or “lower,” melange facies and a western, or “upper,” flysch facies, both of which are considered correlative with the Chugach terrane (Plafker and others, 1977, 1994). The Yakutat Group is in the eastern part of the Yakutat terrane (fig. 1), which is presently accreting onto the southern Alaska margin (Plafker and others, 1978, 1994). The Yakutat terrane likely lay south of the Sitka Graywacke, off the coast of southern British Columbia, when it was offscraped (Plafker and others, 1994). Thus, on a large scale, the Yakutat Group was the now-dismembered part of the accretionary complex that lay to the south of the Sitka Graywacke. One Campanian fossil was obtained in outcrop from the upper part of the Yakutat Group (Jones and Clark, 1973), and Campanian and Maastrichtian foraminifers were recovered from an offshore borehole that penetrated the Yakutat Group (W.V. Sliter, in Rau and others, 1983). Flysch of the upper part of the Yakutat Group is more quartzofeldspathic and has a higher proportion of plutonic-rock fragments relative to the Sitka Graywacke and the Valdez Group (Nilsen, 1984). Nonetheless, the similarity of the youngest peak ages for the western four samples of Sitka Graywacke to the fossil ages for the Yakutat Group indicate that the rocks are approximately coeval, as previously considered (for example, Plafker and others, 1994), although they differ compositionally. The Sitka Graywacke is at least ∼30 m.y. older than the older part of the Chugach accretionary complex in southeastern Alaska (fig. 6). The Kelp Bay Group of Berg and Hinkley (1963), a melange containing fossils as young as Valanginian (Plafker and others, 1976; Decker, 1980), lies in fault contact with the Sitka Graywacke (see units KJkk and Trsv, fig. 2). The oldest detritalzircon limiting age for the Sitka Graywacke is 105 m.y. (sample 66), and so a substantial age gap of ∼30 m.y. exists on the time scale of Gradstein and others (2005). Of course, this age gap may be smaller if younger fossils are present in the Kelp Bay Group, or if older samples are present in the Sitka Graywacke. The youngest peak ages for the eastern three samples of Sitka Graywacke (fig. 2) corresponds to the youngest fossil ages for melange of the McHugh Complex in south-central Alaska (fig. 6; see Plafker and others, 1994, for an overview of ages), which are Albian (99.6–112.0 m.y.) or Cenomanian (99.6–93.5 m.y.; Winkler and others, 1980). The McHugh Complex has been correlated with the Kelp Bay Group (Plafker and others, 1977, 1994; Decker, 1980). The oldest two samples of Sitka Graywacke are Albian (99.6–112.0 m.y.), and the easternmost sample (69) is Cenomanian (93.5–99.6 m.y.). Radiolarians from one small stratigraphically and structurally enigmatic area in Prince William Sound are dated at Coniacian through Turonian (89.3–83.5 m.y.; Haeussler and Nelson, 1993; Nelson and others, 1999), between the ages of the

Valdez Group and the McHugh Complex. Thus, assuming that the detrital-zircon limiting ages are close to the depositional age of the Sitka Graywacke, the age range of the unit is at least ∼26–32 m.y.2, significantly longer than the age range of reliably dated turbidites of the Valdez Group. Considering all these turbidite sequences together suggests relatively continuous turbidite sedimentation between Albian and Maastrichtian time; however, the volume of sediment deposited varies, and clearly a large pulse was deposited in Maastrichtian time (for example, Plafker and others, 1994). The distribution of detrital-zircon ages for the Sitka Graywacke corresponds to that of magmatic ages from southcentral Alaska to British Columbia. The eastern three samples contain the largest number of zircons dated at 100–110 m.y. (particularly samples 66 and 67) and at 145–165 m.y. (figs. 3, 4). Histograms derived from a compilation of igneous-rock ages from British Columbia (Breitsprecher and Mortenson, 2004a) and Yukon Territory (Breitsprecher and Mortenson, 2004b) are shown in figure 5. Numerous plutons in the Coast Mountains of British Columbia and southeastern Alaska dated at 90–110 m.y. may be the source of these zircons. In southcentral Alaska, little magmatism has been reported. Numerous sources are possible, both near and far, for the older ages of 145–165 m.y. that may reflect (1) the Stikine terrane magmatic arc, which lies to the east and south of the study area (fig. 2; Van der Heyden, 1992); (2) plutons on the outer Queen Charlotte Islands in British Columbia (Butler and others, in press), (3) Middle to Late Jurassic plutons in southern British Columbia (for example, van der Heyden, 1992); (4) intrusions in the Saint Elias Mountains (Dodds and Campbell, 1988); or (5) younger phases of the Talkeetna and Chitina plutonic arcs in south-central Alaska (Plafker and others, 1989; Roeske and others, 2003; Trop and others, 2005). These detrital-zircon ages do not uniquely define the source terrain. The western four samples have ages that are consistent with igneous sources from south-central Alaska to southern British Columbia. All four samples contain zircons dated at ∼74 m.y. Plutons at the lower end of this age range occur in the western Alaska Range. Voluminous volcanism occurred in the Talkeetna Mountains of south-central Alaska between 80 and 70 m.y. Detrital zircons from the Cretaceous Matanuska Formation of south-central Alaska have a significant peak in ages of 75–80 m.y. (J.M. Trop, written commun., 2005). Numerous intrusions dated at 57–71 m.y. occur in the region between Juneau and Haines (Gehrels, 2000). A significant peak in detrital-zircon ages from 90–100 m.y. corresponds to a period of voluminous magmatism in southeastern Alaska and British Columbia (fig. 5), and so this peak age seems to reflect

2 The younger age comes from 100 m.y. (the youngest peak age for the eastern three samples, at loc. 69) minus 74 m.y. (the oldest peak age for the western four samples, at locs. 62, 64, and 65) equals 26 m.y., whereas the older age comes from 104 m.y. (the oldest peak age for the eastern three samples, at loc. 66) minus 72 m.y. (the youngest peak age for the western four samples, at loc. 63) equals 32 m.y.


A NUMBER OF DETERMINATIONS

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Figure 5. Histograms of 9,318 isotopic-age determinations from British Columbia and Yukon Territory, from compilations by Breitsprecher and Mortensen (2004a, b). A, All data. B, Data from 50 to 250 m.y., with a 5-m.y. bar width as in figures 3 and 4.

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southern interior British Columbia seem most likely. Although some ages are consistent with source regions in the St. Elias Mountains and in south-central Alaska, they are not demanded.

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indeterminate sources from this region. Moreover, the relatively small number of zircons dated at 80–90 m.y. is also consistent with the absence of plutons in that interval in southern southeastern Alaska and British Columbia. Interestingly, the only >1-b.y. zircons were obtained from the western, young group of samples: 1,686±6, 1,693±8, 1,813±32, and 1,407±96 m.y. (206Pb/207Pb ages). These old ages may reflect sources in the northern Cordilleran miogeocline (Gehrels, 2000) or in the Yukon-Tanana terrane of southeastern Alaska and British Columbia (Kapp and Gehrels, 1998; Gehrels, 2001). In conclusion, the detrital zircons in the samples of Sitka Graywacke do not uniquely identify a source region. Instead, possible source regions cover a vast area from south-central Alaska to southern British Columbia. However, all considerations of the regional tectonics of southeastern Alaska involve some amount of right-lateral strike slip eastward of the Sitka Graywacke. The Border Ranges Fault bounds the east side of the Chugach terrane, and speculations on the amount of right slip range from hundreds of kilometers to more than 1,000 km (Smart and others, 1996; Roeske and others, 2003). The slip must have occurred before 50 m.y., when a pluton intruded across the fault on Chichagof Island (Johnson and Karl, 1985, L.W. Snee, written commun., 1997). The Chatham Strait Fault has ∼150 km of right slip (see discussion in Hudson and others, 1982). The Tintina Fault in British Columbia has ∼420 km of right slip (Gabrielse, 1985) that likely occurred in early Tertiary time (Jackson and Mortensen, 2000). The eastern Denali Fault has ∼370 km of right-lateral offset (Lowey, 1998). Thus, significant margin-parallel right slip clearly occurred in the interval between deposition of the Sitka Graywacke and ∼50 m.y., after which major activity ceased on all these fault systems except the Chatham Strait Fault. Regardless of the uncertainties as to how much slip occurred on different faults at particular times, the Sitka Graywacke was situated south of its present position. Therefore, zircon sources in coastal and central to

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Figure 6. Age range for the Valdez Group (Tysdal and Plafker, 1978, Winkler, 1992; Plafker and others, 1994), younger part of the Kelp Bay Group (Plafker and others, 1976, Decker, 1980), and the McHugh Complex (Winkler, 1992; Plafker and others, 1994), fossiliferous rocks of central Prince William Sound (PWSSSA [Prince William Sound Special Study Area]; Nelson and others, 1999), “upper” flysch facies of the Yakutat Group (Jones and Clark, 1973, W.V. Sliter, in Rau and others, 1983), and detrital-zircon youngest peak ages for the Sitka Graywacke (this study). Time scale from Gradstein and others (2005).

References Cited

Acknowledgments Discussions with Jeff Trop and Dwight Bradley aided our interpretation of the provenance data; their reviews of the manuscript were also greatly appreciated, as were comments by Maria Luisa Crawford and Rich Goldfarb. Thanks also to Alex Pullen for his assistance in processing the U-Pb geochronologic samples. The U-Pb geochronology was supported by National Science Foundation grants EAR–9526263 and EAR–0309885.

References Cited Berg, H.C., and Hinckley, D.W., 1963, Reconnaissance geology of northern Baranof Island, Alaska, in Contributions to general geology, 1961: U.S. Geological Survey Bulletin 1141–O, p. O1–O24 [includes geologic map, scale 1:125,000]. Breitsprecher, Katrin, and Mortensen, J.K., 2004a, BCAge 2004A–1—a database of isotopic age determinations for rock units from British Columbia: British Columbia Geological Survey Open File 2004–3 [release 3.0]. Breitsprecher, Katrin, and Mortensen, J.K., 2004b, YukonAge 2004; a database of isotopic age determinations for rock units from Yukon Territory: Whitehorse, Yukon Territory, Canada, Yukon Geological Survey [CD–ROM]. Butler, R.F., Gehrels, G.E., Hart, William, Davidson, Cameron, and Crawford, M.L., in press, Paleomagnetism of Late Jurassic to mid-Cretaceous plutons near Prince Rupert, British Columbia, in Haggart, J.W., Enkin, R.J., and Monger, J.W.H., eds., Paleogeography of western North America; constraints on large-scale latitudinal displacements: Geological Association of Canada Special Paper. Crawford, M.L., Crawford, W.A., and Gehrels, G.E., 2000, Terrane assembly and structural relationships in the eastern Prince Rupert quadrangle, British Columbia, in Stowell, H.H., and McClelland, W.C., eds., Tectonics of the Coast Mountains, southern Alaska and British Columbia: Geological Society of America Special Paper 343, p. 1–21. Davis, S.J., Roeske, S.M., and Karl, S.M., 1998, Late Cretaceous to early Tertiary transtension and strain partitioning in the Chugach accretionary complex, SE Alaska: Journal of Structural Geology, v. 20, no. 5, p. 639–654. Decker, J.E., 1980, Geology of a Cretaceous subduction complex, western Chichagof Island, southeastern Alaska: Stanford, Calif., Stanford University, Ph.D. thesis, 135 p.

Decker, John, Nilson, T.H., and Karl, S.M., 1979, Turbidite facies of the Sitka Graywacke, southeastern Alaska, in Johnson, K.M., and Williams, J.R., eds., The United States Geological Survey in Alaska; accomplishments during 1978: U.S. Geological Survey Circular 804–B, p. B125–B129. Dodds, C.J., and Campbell, R.B., 1988, Potassium-argon ages of mainly intrusive rocks in the Saint Elias Mountains, Yukon and British Columbia: Geological Survey of Canada Paper 87–16, 43 p. Gabrielse, Hubert, 1985, Major dextral transcurrent displacements along the northern Rocky Mountain Trench and related lineaments in north-central British Columbia: Geological Society of America Bulletin, v. 96, no. 1, p. 1–14. Gehrels, G.E., 2000, Reconnaissance geology and U-Pb geochronology of the west flank of the Coast Mountains between Juneau and Skagway, southeastern Alaska, in Stowell, H.H., and McClelland, W.C., eds., Tectonics of the Coast Mountains, southern Alaska and British Columbia: Geological Society of America Special Paper 343, p. 213–233. Gehrels, G.E., 2001, Geology of the Chatham Sound region, Southeast Alaska and coastal British Columbia: Canadian Journal of Earth Sciences, v. 38, no. 11, p. 1579–1599. Gradstein, F.M., Ogg, J.G., and Smith, A.G., 2005, A geologic time scale 2004: London, Cambridge University Press, 610 p. Grant, U.S., and Higgins, D.F., 1910, Reconnaissance of the geology and mineral resources of Prince William Sound, Alaska: U.S. Geological Survey Bulletin 443, 89 p. [includes geologic map, scale 1:250,000]. Haeussler, P.J., and Nelson, S.W., 1993, Structural evolution of the Chugach-Prince William Terrane at the hinge of the orocline in Prince William Sound, and implications for ore deposits, in Dusel-Bacon, Cynthia, and Till, A.B., eds., Geologic studies in Alaska by the U.S. Geological Survey in 1992: U.S. Geological Survey Bulletin 2068, p. 143–162. Hollister, L.S., 1982, Metamorphic evidence for rapid (2 mm/yr) uplift of a portion of the Central Gneiss Complex, Coast Mountains, B.C.: Canadian Mineralogist, v. 20, no. 3, p. 319–332. Hudson, Travis, Plafker, George, and Dixon, Kirk, 1982, Horizontal offset history of the Chatham Strait fault, in Coonrad, W.L., ed., The United States Geological Survey in Alaska; accomplishments during 1980: U.S. Geological Survey Circular 844, p. 128–132. Jackson, L.E., Jr., and Mortensen, J.K., 2000, New constraints indicate mainly early Paleogene displacement on the Tintina fault zone in the northern Cordillera [abs.]: Geological Society of America Abstracts with Programs, v. 32, no. 6, p. 21.

10 Constraints on the Age and Provenance of the Chugach Accretionary Complex, Alaska Johnson, B.R., and Karl, S.M., 1985, Geologic map of western Chichagof and Yakobi Islands, southeastern Alaska: U.S. Geological Survey Miscellaneous Investigations Map I–1506, 15 p., scale 1:125,000.

Nelson, S.W., Dumoulin, J.A., and Miller, M.L., 1985, Geologic map of the Chugach National Forest, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF–1645–B, 16 p., scale 1:250,000.

Jones, D.L., and Clark, S.H.B., 1973, Upper Cretaceous (Maestrichtian) fossils from the Kenai-Chugach mountains, Kodiak and Shumagin Islands, southern Alaska: U.S. Geological Survey Journal of Research, v. 1, no. 2, p. 125–136.

Nelson, S.W., Miller, M.L., Haeussler, P.J., Snee, L.W., Phillips, P.J., and Huber, Carol, 1999, Preliminary geologic map of the Chugach National Forest special study area, Alaska: U.S. Geological Survey Open-File Report 99–362, scale 1:63,360 [http://wrgis.wr.usgs.gov/open-file/of99-362/].

Kapp, P.A., and Gehrels, G.E., 1998, Detrital zircon constraints on the tectonic evolution of the Gravina Belt, Southeastern Alaska: Canadian Journal of Earth Sciences, v. 35, no. 3, p. 253–268. Karl, S.K., Haeussler, P.J., Himmelberg, Glenn, and Zumsteg, C.Z., in press, Geologic map of Baranof Island, Alaska: U.S. Geological Survey Scientific Investigations Map, scale 1:250,000. Loney, R.A., Berg, H.C., Pomeroy, J.S., and Brew, D.A., 1963, Reconnaissance geologic map of Chichagof Island and northwestern Baranof Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I–388, scale 1:250,000. Lowey, G.W., 1998, A new estimate of the amount of displacement on the Denali Fault system based on the occurrence of carbonate megaboulders in the Dezadeash Formation (JuraCretaceous), Yukon, and the Nutzotin Mountains Sequence (Jura-Cretaceous), Alaska: Bulletin of Canadian Petroleum Geology, v. 46, no. 3, p. 379–386. Ludwig, K.R., 2003, User’s manual for Isoplot 3.0: a geochronological toolkit for Microsoft Excel: Berkeley, Calif., Berkeley Geochronology Center Special Publication 4, 71 p. McClelland, W.C., and Mattinson, J.M., 2000, CretaceousTertiary evolution of the western Coast Mountains, central southeastern Alaska, in Stowell, H.H., and McClelland, W.C., eds., Tectonics of the Coast Mountains, southern Alaska and British Columbia: Geological Society of America Special Paper 343, p. 159–182. Miller, T.P., 1994, Pre-Cenozoic plutonic rocks in mainland Alaska, in Plafker, George, and Berg, H.C., eds., The geology of Alaska, v. G–1 of The geology of North America: Boulder, Colo., Geological Society of America, p. 535–554. Moll-Stalcup, E.J., Brew, D.A., and Vallier, T.L., 1994, Latest Cretaceous and Cenozoic magmatic rocks of Alaska, in Plafker, George, and Berg, H.C., eds., The geology of Alaska, v. G–1 of The geology of North America: Boulder, Colo., Geological Society of America, scale 1:2,500,000.

Nilsen, T.H., 1984, Trench-fill submarine-fan associations of the Upper Cretaceous Chugach terrane, southern Alaska: Geo-Marine Letters, v. 3, no. 2–4, p. 179–185. Nilsen, T.H., and Moore, G.W., 1979, Reconnaissance study of Upper Cretaceous to Miocene stratigraphic units and sedimentary facies, Kodiak and adjacent islands, Alaska: U.S. Geological Survey Professional Paper 1093, 34 p. Nilson, T.H., and Zuffa, G.G., 1982, The Chugach terrane, a Cretaceous trench-fill deposit southern Alaska, in Leggett, J.K., ed., Trench-forearc geology—sedimentation and tectonics on modern and ancient active plate margins: Geological Society of London, Special Publication 10, p. 213–227. Nokleberg, W.J., West, T.D., Dawson, K.M., Shpikerman, V.I., Bundtzen, T.K., Parfenov, L.M., Monger, J.W.H., Ratkin, V.V., Baranov, B.V., Byalobzhesky, S.G., Diggles, M.F., Eremin, R.A., Fugita, Kazuga, Gordey, S.P., Gorodinskiy, M.E., Goryachev, N.A., Feeney, T.D., Frolov, T.F., Grantz, Arthur, Khanchuk, A.I., Koch, R.D., Natalin, B.A., Natapov, L.M., Norton, I.O., Patton, W.W., Jr., Plafker, George, Pozdeev, A.I., Rozenblum, I.S., Scholl, D.W., Sokolov, S.D., Sosunov, G.M., Stone, D.B., Tabor, R.W., Tsukanov, N.V., and Vallier, T.L., 1998, Summary terrane, mineral deposit, and metallogenic belt maps of the Russian Far East, Alaska, and the Canadian Cordillera: U.S. Geological Survey Open-File Report 98–136, CD–ROM [http://wrgis. wr.usgs.gov/open-file/of98-136/]. Plafker, George, Hudson, Travis, Bruns, T.R., and Rubin, Meyer, 1978, Late Quaternary offsets along the Fairweather fault and crustal plate interactions in southern Alaska: Canadian Journal of Earth Sciences, v. 15, no. 5, p. 805–816. Plafker, George, Jones, D.L., Hudson, Travis, and Berg, H.C., 1976, The Border Ranges Fault system in the Saint Elias Mountains and Alexander Archipelago, in Cobb, E.H., ed., The United States Geological Survey in Alaska; accomplishments during 1975: U.S. Geological Survey Circular 733, p. 14–16.

References Cited 11 Plafker, George, Nokleberg, W.J., and Lull, J.S., 1989, Bedrock geology and tectonic evolution of the Wrangellia, Peninsular, and Chugach terranes along the Trans-Alaska Crustal Transect in the Chugach Mountains and southern Copper River basin, Alaska: Journal of Geophysical Research, v. 94, no. B4, p. 4255–4295. Plafker, George, Jones, D.L., and Pessagno, E.A., Jr., 1977, A Cretaceous accretionary flysch and mélange terrane along the Gulf of Alaska margin, in Blean, K.M., ed., The United States Geological Survey in Alaska—accomplishments during 1976: U.S. Geological Survey Circular 751–B, p. B41–B43. Plafker, George, Moore, J.C., and Winkler, G.R., 1994, Geology of the southern Alaska margin, in Plafker, George, and Berg, H.C., eds., The geology of Alaska, v. G–1 of The geology of North America: Boulder, Colo., Geological Society of America, p. 389–449. Rau, W.W., Plafker, George, and Winkler, G.R., 1983, Foraminiferal biostratigraphy and correlations in the Gulf of Alaska Tertiary province: U.S. Geological Survey Oil and Gas Investigations Chart 120, 11 p., 3 sheets. Reifenstuhl, R.R., 1986, Geology of the Goddard Hot Springs area, Baranof Island, southeastern Alaska: Alaska Division of Geological and Geophysical Surveys Public-Data File 86–2, 82 p. Roeske, S.M., Snee, L.W., and Pavlis, T.L., 2003, Dextral-slip reactivation of an arc-forearc boundary during Late Cretaceous-Early Eocene oblique convergence in the northern Cordillera, in Sisson, V.B., Roeske, S.M., and Pavlis, T.L., eds., Geology of a transpressional orogen developed during ridge-trench interaction along the North Pacific margin: Geological Society of America Special Paper 371, p. 141–169. Sample, J.C., and Moore, J.C., 1987, Structural style and kinematics of an underplated slate belt, Kodiak and adjacent islands, Alaska: Geological Society of America Bulletin, v. 19, no. 1, p. 7–20.

Smart, K.J., Pavlis, T.L., Sisson, V.B., Roeske, S.M., and Snee, L.W., 1996, The Border Ranges fault system in Glacier Bay National Park, Alaska; evidence for major early Cenozoic dextral strike-slip motion: Canadian Journal of Earth Sciences, v. 33, no. 9, p. 1268–1282. Stacey, J.S., and Kramers, J.D., 1975, Approximation of terrestrial lead isotope evolution by a two-stage model: Earth and Planetary Science Letters, v. 26, no. 2, p. 207–221. Tarr, R.S., and Butler, B.S., 1909, The Yakutat Bay region, Alaska: U.S. Geological Survey Professional Paper 64, 183 p. Trop, J.M., Szuch, D.A., Rioux, Matthew, and Blodgett, R.B., 2005, Sedimentology and provenance of the Upper Jurassic Naknek Formation, Talkeetna Mountains, Alaska; bearings on the accretionary tectonic history of the Wrangellia composite terrane: Geological Society of America Bulletin, v. 117, no. 5–6, p. 570–588. Tysdal, R.G., and Plafker, George, 1978, Age and continuity of the Valdez Group, southern Alaska, in Sohl, N.F., and Wright, W.B., eds., Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1977: U.S. Geological Survey Bulletin 1457–A, p. A120–A124. van der Heyden, Peter, 1992, A Middle Jurassic to early Tertiary Andean-Sierran arc model for the Coast Belt of British Columbia: Tectonics, v. 11, no. 1, p. 82–97. Winkler, G.R., 1992, Geologic map and summary geochronology of the Anchorage 1°×3° quadrangle, southern Alaska: U.S. Geological Survey Miscellaneous Investigations Map I–2283, scale 1:250,000. Winkler, G.R., Silberman, M.L., Grantz, Arthur, Miller, R.J., and MacKevett, E.M., Jr., 1980, Geologic map and summary geochronology of the Valdez quadrangle, southern Alaska: U. S. Geological Survey Open-File Report 80–892– A, 2 sheets, scale 1:250,000.

Table 2

[All analyses by laser-ablation inductively coupled plasma mass spectroscopy (ICPMS)]

Analysis

U content (ppm)

206

Pb/204Pb ratio

U/Th ratio

206

Pb/208Pb ratio

± (pct)

205

Pb/235U ratio

± (pct)

206

Pb/207Pb ratio

± (pct)

Error correlation

206

Pb/238U age (m.y.)

± (m.y.)

207

Pb/235U ± age (m.y.) (m.y.)

206

Pb/207Pb age (m.y.)

± (m.y.)

Sample 62

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

174 167 106 205 116 182 624 58 310 582 48 115 575 55 240 64 916 272 342 79 140 220 514 89 410 378 184 161 174 515 756 80 131 83 37 92 124 175 77 63 146 102 238 177 147 349

1,518 1,277 5,285 3,040 1,426 1,575 5,499 10,610 1,947 3,858 626 2,152 5,485 618 1,712 610 7,112 3,812 4,617 1,714 1,036 2,789 6,619 12,945 3,986 3,213 2,040 3,923 1,501 3,856 3,662 853 1,278 1,114 498 64,668 1,304 546 410 513 5,387 1,368 951 1,516 1,171 2,642

45 29 32 49 24 50 40 14 13 25 32 48 23 24 21 65 53 21 12 101 120 49 22 17 10 74 48 28 27 35 13 58 39 47 26 54 38 48 62 37 142 45 39 24 29 16

0.01036 0.01097 0.03082 0.01328 0.03218 0.01736 0.01156 0.26190 0.01388 0.01246 0.01187 0.01271 0.01105 0.01126 0.01544 0.01195 0.01207 0.01434 0.01512 0.02309 0.01220 0.01404 0.01091 0.27611 0.01359 0.01387 0.01233 0.02912 0.01535 0.01111 0.01062 0.01213 0.01219 0.01191 0.01153 0.01061 0.01492 0.01430 0.01124 0.01082 0.01342 0.01311 0.01135 0.01164 0.01183 0.01548

0.5 1.6 1.6 1.5 1.0 1.7 0.6 1.2 1.8 2.0 2.1 0.7 0.6 1.8 1.1 2.7 1.0 1.6 0.7 2.9 1.4 1.1 1.2 1.1 9.1 2.7 0.8 1.2 1.0 1.0 2.3 3.1 1.4 1.9 1.4 2.1 1.6 1.9 3.2 0.7 2.4 1.7 0.6 0.7 0.8 0.5

0.06271 0.07066 0.20209 0.08855 0.25335 0.11639 0.07674 3.73401 0.09780 0.09618 0.05028 0.08244 0.07384 0.04703 0.10393 0.05233 0.08152 0.08823 0.10298 0.14268 0.08865 0.09104 0.07533 3.95064 0.09969 0.10538 0.08421 0.20582 0.12429 0.07611 0.07743 0.07814 0.08371 0.10958 0.06054 0.10404 0.12926 0.10767 0.06565 0.04868 0.10595 0.09386 0.09435 0.07871 0.07098 0.11711

6.1 6.7 5.1 3.7 3.6 2.7 2.2 1.4 4.0 2.6 4.5 6.3 2.6 25.7 3.4 7.7 1.4 2.7 2.8 6.2 6.7 3.7 3.6 1.4 10.2 4.0 6.9 3.2 6.9 2.3 3.6 13.7 8.0 10.2 16.7 26.4 10.1 6.3 7.8 15.1 6.1 11.7 5.6 5.9 7.0 3.8

22.77 21.41 21.03 20.67 17.51 20.56 20.77 9.67 19.58 17.87 32.55 21.25 20.64 33.01 20.49 31.49 20.42 22.41 20.24 22.32 18.98 21.26 19.96 9.64 18.79 18.15 20.20 19.51 17.03 20.13 18.91 21.41 20.08 14.99 26.26 14.06 15.92 18.32 23.62 30.66 17.47 19.26 16.59 20.39 22.99 18.22

6.1 6.6 4.8 3.4 3.5 2.1 2.1 0.7 3.5 1.7 4.0 6.2 2.6 25.7 3.2 7.1 1.1 2.2 2.7 5.5 6.6 3.5 3.4 0.9 4.7 2.9 6.8 2.9 6.8 2.1 2.7 13.3 7.9 10.0 16.7 26.3 10.0 6.0 7.2 15.1 5.6 11.6 5.6 5.9 6.9 3.8

0.08 0.23 0.31 0.40 0.27 0.62 0.28 0.88 0.45 0.76 0.46 0.11 0.23 0.07 0.31 0.36 0.66 0.59 0.26 0.46 0.21 0.30 0.35 0.79 0.89 0.68 0.12 0.39 0.15 0.43 0.64 0.23 0.18 0.19 0.08 0.08 0.15 0.31 0.41 0.05 0.39 0.15 0.11 0.11 0.12 0.13

66.4 70.4 195.7 85.0 204.2 110.9 74.1 1,499.6 88.9 79.8 76.1 81.4 70.9 72.2 98.8 76.6 77.4 91.8 96.7 147.2 78.2 89.9 69.9 1,571.8 87.0 88.8 79.0 185.0 98.2 71.2 68.1 77.8 78.1 76.3 73.9 68.0 95.5 91.5 72.1 69.4 86.0 84.0 72.8 74.6 75.8 99.0

0.3 1.1 3.1 1.3 2.0 1.9 0.5 20.2 1.6 1.6 1.6 0.6 0.4 1.3 1.1 2.1 0.7 1.5 0.7 4.3 1.1 1.0 0.9 19.3 7.9 2.4 0.7 2.3 1.0 0.7 1.6 2.4 1.1 1.5 1.0 1.4 1.5 1.8 2.3 0.5 2.1 1.5 0.5 0.5 0.6 0.5

61.8 69.3 186.9 86.2 229.3 111.8 75.1 1,578.7 94.7 93.2 49.8 80.4 72.3 46.7 100.4 51.8 79.6 85.9 99.5 135.4 86.2 88.5 73.7 1,624.1 96.5 101.7 82.1 190.0 119.0 74.5 75.7 76.4 81.6 105.6 59.7 100.5 123.4 103.8 64.6 48.3 102.3 91.1 91.5 76.9 69.6 112.4

3.9 4.8 10.3 3.3 9.3 3.1 1.7 50.6 3.9 2.5 2.3 5.2 2.0 12.2 3.5 4.1 1.2 2.4 2.9 8.9 6.0 3.4 2.7 53.9 10.3 4.2 5.9 6.6 8.6 1.8 2.8 10.8 6.8 11.2 10.2 27.5 13.2 6.9 5.2 7.4 6.6 11.1 5.4 4.7 5.0 4.5

–115 34 77 118 495 130 106 1,686 245 451 –1,087 52 122 –1,129 139 –988 146 –76 167 –66 316 51 199 1,693 338 417 172 253 557 180 324 34 186 829 –479 961 702 396 –206 –909 501 282 614 150 –139 407

75 78 57 40 38 25 25 6 41 19 61 74 30 392 38 106 13 27 32 67 75 42 39 8 54 32 80 33 74 24 31 160 92 104 221 268 106 67 90 219 62 133 60 69 86 42

14 Constraints on the Age and Provenance of the Chugach Accretionary Complex, Alaska

Table 2. Analytical data on detrital zircons

Table 2. Analytical data on detrital zircons.—Continued [All analyses by laser-ablation inductively coupled plasma mass spectroscopy (ICPMS)]

Analysis

47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

U content (ppm) 244 344 315 135 133 119 108 45 1,139 453 160 267 186 199 187 319 421 324 180 337 220 164 437 252

206

Pb/204Pb ratio 8,934 3,790 3,063 1,401 1,689 1,630 728 689 4,694 2,568 899 2,332 1,509 896 1,285 4,204 2,707 2,778 1,060 1,929 970 1,344 1,811 2,273

U/Th ratio 65 23 32 25 34 32 63 41 29 20 35 43 41 51 46 20 40 33 26 20 41 40 –2 23

206

Pb/208Pb ratio

0.06705 0.01685 0.01545 0.01501 0.01554 0.02311 0.01455 0.01399 0.01146 0.01071 0.01525 0.01237 0.01330 0.01226 0.01390 0.01743 0.01114 0.01456 0.01052 0.01432 0.01173 0.01514 0.01085 0.01512

± (pct) 1.4 1.2 0.9 0.7 1.7 1.8 3.0 3.4 0.9 0.6 0.9 0.8 3.2 2.0 2.3 3.0 0.6 0.7 0.7 0.7 1.3 2.0 1.0 1.0

205

Pb/235U ratio

0.51139 0.12062 0.10319 0.08852 0.11988 0.15298 0.11625 0.12501 0.07642 0.06663 0.10584 0.08554 0.08058 0.06797 0.10999 0.12210 0.07046 0.09647 0.07889 0.10075 0.09427 0.10335 0.06058 0.10903

± (pct) 1.5 2.3 3.5 6.1 10.1 4.7 8.1 17.2 1.8 2.5 4.2 3.5 6.1 5.3 8.1 4.2 2.7 2.5 6.3 3.2 6.2 6.6 5.4 4.7

206

Pb/207Pb ratio

18.08 19.26 20.65 23.39 17.87 20.83 17.25 15.43 20.67 22.16 19.87 19.94 22.76 24.87 17.42 19.69 21.81 20.81 18.39 19.59 17.16 20.19 24.69 19.13

± (pct)

Error correlation

206

Pb/238U age (m.y.)

± (m.y.)

207

Pb/235U ± age (m.y.) (m.y.)

206

Pb/207Pb age (m.y.)

± (m.y.)

0.7 2.0 3.3 6.0 10.0 4.4 7.5 16.8 1.5 2.4 4.1 3.5 5.1 4.9 7.7 2.9 2.6 2.4 6.3 3.2 6.0 6.2 5.3 4.6

0.90 0.52 0.27 0.11 0.17 0.38 0.37 0.20 0.52 0.24 0.21 0.22 0.53 0.37 0.29 0.71 0.24 0.28 0.12 0.20 0.21 0.31 0.19 0.21

418.4 107.7 98.9 96.1 99.4 147.3 93.1 89.6 73.4 68.7 97.6 79.3 85.2 78.6 89.0 111.4 71.4 93.2 67.5 91.6 75.2 96.8 69.6 96.8

5.9 1.3 0.9 0.7 1.7 2.6 2.8 3.1 0.7 0.4 0.8 0.6 2.8 1.6 2.1 3.3 0.5 0.7 0.5 0.6 1.0 2.0 0.7 0.9

419.4 115.6 99.7 86.1 115.0 144.5 111.7 119.6 74.8 65.5 102.2 83.3 78.7 66.8 106.0 117.0 69.1 93.5 77.1 97.5 91.5 99.9 59.7 105.1

7.8 2.8 3.6 5.4 12.3 7.3 9.5 21.6 1.4 1.7 4.5 3.1 4.9 3.7 8.9 5.1 1.9 2.5 5.0 3.3 5.9 6.9 3.3 5.2

425 282 120 –182 451 99 528 768 118 –49 211 202 –115 –338 507 232 –10 102 386 243 540 173 –319 298

7 23 39 75 111 52 82 177 18 29 47 40 63 63 85 34 32 29 70 36 66 73 68 53

8.9 5.0 2.6 25.5 2.4 19.1 3.6 16.4 7.2 3.9 5.3 17.4 1.8 14.4 7.5 2.6 18.1 3.4 3.3 3.4 5.2

0.09 0.19 0.25 0.06 0.28 0.05 0.24 0.09 0.10 0.33 0.31 0.04 0.35 0.07 0.13 0.19 0.09 0.47 0.17 0.31 0.17

144.7 71.2 70.9 84.1 376.6 94.7 1,802.3 79.4 71.0 80.9 149.4 82.1 69.2 75.5 72.5 194.4 80.0 85.6 71.3 92.0 70.6

1.2 0.7 0.5 1.3 2.7 0.9 18.2 1.1 0.5 1.1 2.6 0.5 0.5 0.7 0.7 1.0 1.4 1.5 0.4 1.0 0.6

142.6 71.3 67.4 72.9 396.0 77.2 1,807.2 106.4 75.5 81.6 149.6 103.3 70.9 89.8 72.8 193.0 115.8 74.6 76.0 121.3 75.8

13.6 3.8 1.8 19.1 11.8 15.2 169.0 18.3 5.6 3.5 8.9 18.8 1.4 13.5 5.7 5.7 22.0 3.0 2.7 4.6 4.2

108 74 –55 –282 511 –438 1,813 763 219 102 154 625 128 488 84 175 933 –265 226 743 244

105 59 31 324 26 251 32 173 83 46 62 188 21 159 89 31 185 43 38 36 60

Sample 63

59 160 238 22 79 25 37 72 173 139 48 104 471 119 131 181 48 112 483 214 134

13,918 5,137 3,161 573 5,831 1,964 83,222 1,342 7,344 3,192 5,639 23,808 10,746 28,627 12,296 3,725 5,001 1,125 5,095 3,919 1,873

31 28 149 43 36 20 9 56 27 66 –149 37 25 31 31 29 103 58 22 139 37

0.02270 0.01111 0.01107 0.01313 0.06016 0.01481 0.32258 0.01240 0.01107 0.01263 0.02344 0.01282 0.01079 0.01178 0.01130 0.03062 0.01248 0.01337 0.01113 0.01438 0.01101

0.8 1.0 0.7 1.6 0.7 0.9 0.9 1.4 0.8 1.4 1.7 0.6 0.7 1.0 1.0 0.5 1.7 1.8 0.6 1.1 0.9

0.15078 0.07275 0.06868 0.07440 0.47700 0.07898 4.92856 0.11052 0.07715 0.08372 0.15879 0.10712 0.07227 0.09242 0.07432 0.20932 0.12078 0.07625 0.07776 0.12694 0.07754

9.0 5.1 2.7 25.5 2.5 19.1 3.7 16.5 7.2 4.2 5.6 17.4 1.9 14.5 7.6 2.7 18.2 3.8 3.4 3.6 5.3

20.76 21.05 22.21 24.34 17.39 25.85 9.02 15.46 19.79 20.81 20.35 16.50 20.59 17.57 20.97 20.17 14.25 24.18 19.73 15.62 19.58

Table 2 15

1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22


Analysis

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

U content (ppm) 177 51 294 263 33 111 78 83 78 105 135 144 90 165 69 604 285 121 83 40 172 82 473 58 90 50 123 66 90 108 120 190 38 155 109 42 25 125 140 56 135 50 83 79 94 227 72 66

206

Pb/204Pb ratio

8,126 4,372 7,446 8,458 1,099 104,314 3,743 2,866 1,113 16,364 1,304 15,149 1,311 7,645 778 3,928 4,345 3,609 2,687 3,714 4,776 1,327 7,172 2,165 7,619 2,388 1,114 5,583 5,745 1,193 49,185 837 1,119 18,802 896 2,803 399 28,732 3,849 2,725 6,664 1,876 1,582 3,213 9,235 8,155 1,239 1,449

U/Th ratio 29 25 47 72 51 33 29 25 36 29 –4 18 43 16 55 34 12 42 27 27 102 63 33 26 31 22 49 27 18 23 42 17 23 29 42 41 29 19 25 30 46 73 42 34 34 27 20 41

206

Pb/208Pb ratio

0.01192 0.01652 0.01150 0.01466 0.02267 0.01125 0.05339 0.01235 0.01086 0.01155 0.01208 0.05467 0.01139 0.01221 0.01411 0.01150 0.02867 0.01198 0.01118 0.02385 0.01479 0.01846 0.01129 0.01164 0.01207 0.01154 0.01061 0.03129 0.06100 0.01128 0.06153 0.01181 0.01232 0.03050 0.01132 0.02469 0.01263 0.02979 0.01190 0.02864 0.01332 0.01107 0.01147 0.02296 0.05254 0.01156 0.05653 0.01104

± (pct) 0.7 1.5 2.9 1.2 1.9 1.3 0.7 1.0 1.1 0.9 1.9 1.1 1.0 0.8 1.0 0.7 2.1 0.9 0.6 2.1 2.1 2.0 0.5 1.3 1.1 1.1 0.9 1.0 1.5 0.9 0.8 1.2 1.8 0.6 1.4 2.4 1.9 0.8 1.0 1.1 1.4 1.6 1.1 1.1 0.8 0.6 1.6 2.0

205

Pb/235U ratio

0.07867 0.11365 0.07741 0.09323 0.16385 0.08231 0.40188 0.08878 0.06350 0.07634 0.05835 0.40752 0.05916 0.08735 0.06097 0.07040 0.21587 0.14225 0.07305 0.14782 0.14146 0.10719 0.07470 0.06051 0.08245 0.07187 0.07244 0.19217 0.44518 0.05842 0.47921 0.08156 0.08867 0.20881 0.06251 0.15078 0.05939 0.21519 0.07418 0.18994 0.09034 0.07028 0.06950 0.15040 0.39639 0.07625 0.37073 0.06147

± (pct) 6.9 11.2 4.3 2.7 19.7 35.5 2.6 10.7 7.6 8.3 7.7 2.0 8.0 5.5 7.0 2.9 3.3 3.9 6.3 18.1 5.5 6.4 2.2 12.4 10.8 14.8 6.9 5.0 2.4 7.5 4.7 5.9 35.1 2.8 4.2 7.3 30.3 4.1 6.2 7.4 6.3 12.9 6.8 3.9 2.6 6.2 5.1 12.7

206

Pb/207Pb ratio

20.89 20.04 20.49 21.68 19.07 18.85 18.32 19.19 23.58 20.87 28.54 18.50 26.55 19.27 31.91 22.52 18.31 11.61 21.10 22.24 14.42 23.74 20.84 26.52 20.19 22.13 20.19 22.45 18.89 26.63 17.70 19.96 19.16 20.14 24.96 22.58 29.32 19.09 22.11 20.79 20.34 21.73 22.75 21.05 18.28 20.90 21.03 24.77

± (pct) 6.8 11.1 3.2 2.4 19.7 35.5 2.5 10.7 7.5 8.3 7.5 1.7 8.0 5.4 6.9 2.8 2.6 3.8 6.3 18.0 5.1 6.1 2.2 12.3 10.7 14.8 6.9 4.9 1.9 7.4 4.7 5.8 35.1 2.8 4.0 6.9 30.2 4.0 6.1 7.3 6.1 12.8 6.7 3.8 2.5 6.2 4.8 12.6

Error correlation 0.10 0.13 0.66 0.44 0.10 0.04 0.26 0.10 0.14 0.11 0.24 0.53 0.12 0.15 0.15 0.26 0.62 0.22 0.09 0.12 0.38 0.31 0.23 0.10 0.10 0.08 0.13 0.19 0.62 0.12 0.16 0.20 0.05 0.21 0.34 0.33 0.06 0.19 0.17 0.15 0.22 0.12 0.16 0.28 0.29 0.10 0.32 0.16

206

Pb/238U age (m.y.)

76.4 105.6 73.7 93.8 144.5 72.1 335.3 79.1 69.6 74.0 77.4 343.1 73.0 78.2 90.3 73.7 182.2 76.8 71.6 151.9 94.7 117.9 72.4 74.6 77.4 73.9 68.0 198.6 381.7 72.3 384.9 75.7 78.9 193.7 72.5 157.2 80.9 189.2 76.2 182.0 85.3 71.0 73.5 146.3 330.1 74.1 354.5 70.8

± (m.y.) 0.5 1.6 2.1 1.1 2.8 1.0 2.3 0.8 0.8 0.7 1.5 3.7 0.7 0.6 0.9 0.6 3.8 0.7 0.4 3.2 2.0 2.3 0.4 0.9 0.9 0.8 0.6 1.9 5.8 0.6 3.0 0.9 1.4 1.2 1.0 3.9 1.5 1.5 0.8 2.0 1.2 1.1 0.8 1.6 2.6 0.5 5.9 1.4

207

Pb/235U ± age (m.y.) (m.y.)

76.9 109.3 75.7 90.5 154.1 80.3 343.0 86.4 62.5 74.7 57.6 347.1 58.4 85.0 60.1 69.1 198.5 135.0 71.6 140.0 134.3 103.4 73.1 59.7 80.4 70.5 71.0 178.5 373.9 57.7 397.5 79.6 86.3 192.6 61.6 142.6 58.6 197.9 72.7 176.6 87.8 69.0 68.2 142.3 339.0 74.6 320.2 60.6

5.5 12.8 3.4 2.5 32.3 29.2 10.4 9.6 4.9 6.4 4.6 8.3 4.8 4.9 4.3 2.0 7.3 5.6 4.7 26.8 7.9 7.0 1.7 7.6 9.0 10.7 5.1 9.8 10.7 4.4 22.8 4.9 31.1 6.0 2.7 11.2 18.1 8.9 4.6 14.1 5.7 9.1 4.8 6.0 10.6 4.8 18.9 7.9

206

Pb/207Pb age (m.y.)

92 191 139 4 304 331 396 291 –203 96 –706 374 –508 281 –1027 –88 396 1,341 69 –58 909 –220 99 –505 173 –46 173 –80 326 –517 472 200 294 179 –347 –95 –781 303 –43 105 156 –1 –113 75 401 92 78 –327

± (m.y.) 81 129 38 29 224 402 28 122 94 98 104 19 106 62 102 34 29 36 75 219 52 77 26 164 125 179 80 60 21 99 52 67 401 32 51 85 427 46 74 86 72 154 82 45 28 73 57 161


Table 2. Analytical data on detrital zircons.—Continued


Analysis

U content (ppm)

206

Pb/204Pb ratio

U/Th ratio

206

Pb/208Pb ratio

± (pct)

205

Pb/235U ratio

± (pct)

206

Pb/207Pb ratio

± (pct)

Error correlation

9.5 8.4 4.2 5.5 7.1 6.8 3.6 3.0 3.9 4.7 6.0 1.6 2.9 3.9 2.1 11.8 3.4 4.4 1.8 4.4 5.7 10.6 7.7 3.8 3.6 1.5 2.6 8.0 3.0 7.5 1.9 3.6 2.0 5.7 5.0 5.0 5.5 4.8 10.3 2.4 15.6 12.6 3.8 2.9 9.7 1.5

0.14 0.16 0.16 0.21 0.15 0.21 0.26 0.23 0.24 0.26 0.45 0.41 0.29 0.19 0.27 0.30 0.26 0.51 0.63 0.20 0.11 0.25 0.19 0.25 0.22 0.36 0.31 0.29 0.43 0.11 0.56 0.27 0.71 0.56 0.15 0.13 0.18 0.25 0.15 0.28 0.34 0.23 0.21 0.34 0.09 0.43

206

Pb/238U age (m.y.)

± (m.y.)

207

Pb/235U ± age (m.y.) (m.y.)

206

Pb/207Pb age (m.y.)

± (m.y.)

Sample 64

107 82 218 124 121 188 191 381 281 204 316 101 260 170 139 77 165 249 672 198 282 80 66 172 250 111 513 174 258 182 267 383 519 125 202 171 333 261 61 63 64 30 367 460 133 507

753 1,669 3,857 2,154 1,671 2,703 1,847 5,374 6,578 1,007 388 5,068 4,869 1,545 1,697 1,930 2,164 2,812 16,092 5,005 5,660 1,490 320 1,308 3,314 11,325 4,975 1,128 3,501 2,851 721 5,018 5,740 1,486 3,799 1,317 1,783 6,149 1,182 6,499 1,397 1,061 1,745 1,983 1,769 7,605

38 22 39 11 41 25 43 21 18 31 84 19 24 39 272 22 22 32 38 27 15 42 116 63 51 31 29 66 41 36 84 23 14 28 35 38 33 27 27 20 24 76 71 89 28 35

0.01186 0.01441 0.01150 0.01384 0.01121 0.01480 0.01212 0.01188 0.01159 0.01172 0.01178 0.05417 0.01409 0.01402 0.01685 0.01619 0.01458 0.01157 0.01238 0.01471 0.01079 0.01564 0.01256 0.01193 0.01203 0.06624 0.01172 0.01146 0.01231 0.01114 0.01280 0.01473 0.01111 0.01784 0.01321 0.01492 0.01134 0.01151 0.01435 0.05982 0.01415 0.01614 0.01188 0.01197 0.01117 0.01138

1.3 1.4 0.7 1.2 1.0 1.4 1.0 0.7 1.0 1.3 3.0 0.7 0.9 0.8 0.6 3.7 0.9 2.6 1.4 0.9 0.6 2.8 1.5 1.0 0.8 0.6 0.8 2.5 1.4 0.8 1.3 1.0 2.0 3.9 0.8 0.7 1.0 1.3 1.6 0.7 5.6 3.0 0.8 1.1 0.9 0.7

0.10486 0.08538 0.06840 0.09876 0.06446 0.08951 0.07342 0.08194 0.07854 0.06537 0.08824 0.42835 0.09759 0.09165 0.11463 0.09738 0.09668 0.07574 0.08429 0.10503 0.07704 0.10123 0.08840 0.07652 0.07588 0.52233 0.08892 0.07198 0.07956 0.07597 0.07264 0.10927 0.07778 0.12643 0.09898 0.14103 0.07609 0.08247 0.07682 0.44407 0.10351 0.09616 0.11124 0.10668 0.06173 0.07780

9.6 8.5 4.3 5.6 7.2 7.0 3.8 3.1 4.0 4.9 6.8 1.7 3.1 4.0 2.2 12.3 3.6 5.1 2.3 4.5 5.7 10.9 7.9 3.9 3.7 1.6 2.7 8.4 3.3 7.5 2.3 3.7 2.8 6.9 5.1 5.1 5.6 5.0 10.4 2.5 16.5 12.9 3.9 3.1 9.7 1.7

15.60 23.27 23.17 19.32 23.98 22.80 22.76 19.98 20.34 24.73 18.41 17.44 19.91 21.09 20.26 22.93 20.79 21.06 20.25 19.31 19.32 21.30 19.60 21.49 21.86 17.49 18.18 21.95 21.33 20.22 24.29 18.59 19.69 19.45 18.40 14.59 20.54 19.25 25.75 18.57 18.85 23.15 14.73 15.48 24.95 20.18

76.0 92.2 73.7 88.6 71.9 94.7 77.7 76.1 74.3 75.1 75.5 340.1 90.2 89.7 107.7 103.6 93.3 74.2 79.3 94.2 69.2 100.0 80.5 76.4 77.1 413.4 75.1 73.5 78.9 71.4 82.0 94.3 71.2 114.0 84.6 95.5 72.7 73.8 91.8 374.5 90.6 103.2 76.1 76.7 71.6 73.0

1.0 1.3 0.5 1.1 0.8 1.4 0.8 0.5 0.7 0.9 2.3 2.5 0.8 0.7 0.7 3.8 0.9 1.9 1.1 0.9 0.4 2.8 1.2 0.7 0.6 2.4 0.6 1.8 1.1 0.6 1.0 0.9 1.4 4.4 0.7 0.6 0.7 0.9 1.5 2.6 5.1 3.1 0.6 0.8 0.7 0.5

101.3 83.2 67.2 95.6 63.4 87.0 71.9 80.0 76.8 64.3 85.9 362.0 94.6 89.0 110.2 94.4 93.7 74.1 82.2 101.4 75.4 97.9 86.0 74.9 74.3 426.7 86.5 70.6 77.7 74.3 71.2 105.3 76.1 120.9 95.8 134.0 74.5 80.5 75.2 373.1 100.0 93.2 107.1 102.9 60.8 76.1

10.2 7.3 3.0 5.6 4.7 6.3 2.8 2.5 3.2 3.2 6.0 7.5 3.0 3.7 2.6 12.1 3.5 3.9 1.9 4.7 4.5 11.2 7.0 3.1 2.8 8.3 2.5 6.1 2.7 5.8 1.7 4.1 2.2 8.8 5.1 7.2 4.3 4.2 8.1 11.1 17.2 12.5 4.4 3.3 6.1 1.3

745 –169 –159 275 –245 –118 –114 197 156 –323 384 505 206 71 164 –132 104 73 166 275 275 46 242 25 –16 499 413 –26 43 169 –277 363 231 259 385 886 133 283 –428 365 331 –156 866 762 –345 174

101 104 52 63 90 84 45 34 45 61 68 17 34 47 25 146 41 52 21 50 65 126 89 46 43 16 29 97 36 87 24 40 23 66 56 52 65 55 135 27 176 156 40 30 124 18

Table 2 17

1 2 3 4 5 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Analysis

48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

U content (ppm) 144 302 502 120 155 620 108 179 121 106 62 295 728 113 32 124 58 178 201 113 128 65 340

206

Pb/204Pb ratio

1,684 4,056 6,319 1,781 1,032 5,940 6,800 897 1,675 2,235 1,056 7,277 2,344 289 829 1,680 980 14,786 2,001 1,571 2,117 1,367 3,209

U/Th ratio 41 16 19 110 43 49 27 40 30 33 33 28 79 37 –9 51 144 23 22 116 34 72 38

206

Pb/208Pb ratio

0.01219 0.01147 0.01138 0.01806 0.01232 0.01239 0.05529 0.01275 0.01206 0.01665 0.01095 0.01377 0.01136 0.01589 0.01544 0.01203 0.01507 0.07129 0.01316 0.01716 0.01630 0.01598 0.01143

± (pct) 5.7 0.8 0.7 4.2 2.0 0.9 2.2 0.8 0.9 1.5 2.1 0.8 1.0 3.9 1.0 2.5 3.0 0.9 4.2 3.1 1.6 1.3 0.7

205

Pb/235U ratio

0.09822 0.07815 0.07697 0.14720 0.08832 0.08836 0.40141 0.07716 0.07180 0.11979 0.05000 0.09199 0.07874 0.12301 0.09741 0.07329 0.10731 0.56185 0.10535 0.12758 0.10415 0.10477 0.08013

± (pct) 7.4 4.1 2.0 7.8 5.9 1.7 2.8 6.8 7.1 6.9 16.7 2.2 1.9 7.2 4.6 10.2 30.7 1.2 6.1 7.7 9.9 15.7 2.7

206

Pb/207Pb ratio

17.11 20.23 20.39 16.91 19.23 19.34 18.99 22.79 23.17 19.17 30.20 20.63 19.89 17.81 21.86 22.64 19.37 17.50 17.23 18.55 21.58 21.03 19.66

± (pct)

Error correlation

4.8 4.0 1.9 6.6 5.5 1.5 1.7 6.8 7.1 6.7 16.6 2.0 1.6 6.1 4.5 9.9 30.6 0.8 4.4 7.1 9.7 15.7 2.6

0.77 0.18 0.34 0.54 0.34 0.52 0.80 0.12 0.13 0.22 0.13 0.39 0.54 0.54 0.21 0.25 0.10 0.76 0.69 0.40 0.16 0.08 0.27

78.1 73.5 73.0 115.4 78.9 79.4 346.9 81.7 77.3 106.5 70.2 88.1 72.8 101.6 98.8 77.1 96.5 443.9 84.3 109.7 104.2 102.2 73.2

4.4 0.6 0.5 4.9 1.6 0.7 8.0 0.7 0.7 1.6 1.5 0.7 0.7 3.9 0.9 1.9 2.9 4.0 3.6 3.4 1.7 1.3 0.5

95.1 76.4 75.3 139.4 85.9 86.0 342.7 75.5 70.4 114.9 49.5 89.4 77.0 117.8 94.4 71.8 103.5 452.7 101.7 121.9 100.6 101.2 78.3

7.3 3.2 1.6 11.7 5.3 1.6 11.4 5.3 5.2 8.3 8.5 2.0 1.5 8.9 4.6 7.6 32.9 6.6 6.5 10.0 10.4 16.6 2.2

546 169 150 572 286 273 314 –117 –158 293 –865 122 208 459 –16 –101 269 498 532 368 15 77 234

52 47 22 72 63 17 19 83 88 76 239 23 18 67 55 122 350 8 49 80 117 186 30

3.8 3.5 3.4 1.7 5.7 2.9 8.1 2.2 8.6 2.3 2.0 3.3 12.4 2.5 15.3 7.4 5.5 1.7 2.9 4.2 34.9 5.9

0.12 0.09 0.15 0.39 0.17 0.19 0.11 0.31 0.10 0.18 0.20 0.16 0.04 0.30 0.12 0.19 0.22 0.43 0.54 0.25 0.06 0.16

98.7 96.8 98.5 70.0 76.8 104.5 122.6 100.0 84.9 89.9 91.7 71.2 75.4 96.5 76.4 71.9 73.0 78.6 113.3 79.0 85.4 74.2

0.5 0.3 0.5 0.5 0.8 0.6 1.1 0.7 0.7 0.4 0.4 0.4 0.4 0.8 1.4 1.0 0.9 0.6 2.1 0.9 1.7 0.7

154.1 97.2 97.3 60.8 105.9 105.6 110.1 87.2 87.8 84.7 90.4 82.0 68.3 104.3 61.6 71.3 92.5 81.5 112.7 105.1 81.5 89.5

6.3 3.5 3.5 1.2 6.5 3.3 9.4 2.1 7.9 2.0 1.9 2.9 8.7 2.9 9.7 5.6 5.5 1.6 4.1 4.8 29.3 5.6

1,123 107 68 –289 823 133 –153 –250 166 –59 56 411 –174 286 –480 53 632 166 100 747 –31 519

38 41 40 22 60 34 100 28 100 27 24 37 155 29 203 89 59 20 34 45 423 65

206

Pb/238U age (m.y.)

± (m.y.)

207

Pb/235U ± age (m.y.) (m.y.)

206

Pb/207Pb age (m.y.)

± (m.y.)

Sample 65

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 17 18 19 20 21 22

351 428 262 17 40 60 15 20 90 118 94 23 101 99 74 25 152 95 100 140 131 80

4,928 6,085 7,204 1,514 749 6,396 1,298 2,186 6,466 2,122 3,016 2,534 2,768 4,467 3,807 3,560 4,936 3,877 3,015 3,559 6,891 15,088

454 822 148 1,297 131 51 91 618 37 673 65 811 43 35 60 645 1,878 409 186 255 979 1,008

0.01542 0.01512 0.01539 0.01092 0.01198 0.01634 0.01920 0.01563 0.01326 0.01404 0.01432 0.01110 0.01177 0.01509 0.01191 0.01121 0.01138 0.01227 0.01773 0.01233 0.01334 0.01158

0.5 0.3 0.5 0.7 1.0 0.6 0.9 0.7 0.9 0.4 0.4 0.5 0.5 0.8 1.8 1.4 1.2 0.8 1.8 1.1 2.0 1.0

0.16388 0.10041 0.10055 0.06172 0.10992 0.10965 0.11448 0.08967 0.09029 0.08698 0.09308 0.08416 0.06960 0.10817 0.06255 0.07280 0.09541 0.08354 0.11738 0.10911 0.08362 0.09213

3.8 3.5 3.4 1.9 5.8 3.0 8.1 2.3 8.6 2.3 2.1 3.4 12.4 2.7 15.4 7.6 5.7 1.9 3.4 4.4 35.0 6.0

12.98 20.77 21.11 24.40 15.03 20.54 23.12 24.04 20.25 22.25 21.21 18.19 23.32 19.23 26.26 21.24 16.45 20.25 20.83 15.58 21.99 17.33




Analysis

75 174 49 64 491 173 86 195 83 252 86 134 67 250 156 200 144 112 189 144 84 80 95 96 149 120 140 83 63 136 127 176 236 72 87 134 152 29 123 169 75 54 84 116 75 159 79 162

206

Pb/204Pb ratio

15,568 4,918 14,056 7,449 5,047 7,064 13,376 8,857 5,270 2,185 328,263 359,267 57,499 6,817 3,704 5,147 12,849 6,683 4,857 8,257 27,516 59,155 3,013 13,330 84,074 5,575 7,197 56,074 68,167 13,640 9,398 10,779 13,057 37,851 91,888 10,571 3,420 8,657 26,665 7,583 35,515 6,482 30,396 7,549 17,178 14,525 38,454 6,862

U/Th ratio 571 1,316 749 283 819 599 538 2,247 578 487 323 2,303 459 263 418 1,450 2,775 1,007 319 867 523 477 1,230 560 865 200 1,113 792 980 3,058 784 228 318 489 386 1,512 628 223 1,002 471 847 418 222 85 940 2,852 438 1,664

206

Pb/208Pb ratio

0.02322 0.01420 0.01454 0.02294 0.01469 0.02460 0.01500 0.01295 0.02238 0.01441 0.01515 0.01135 0.02283 0.01425 0.01532 0.01122 0.01846 0.02289 0.01491 0.01588 0.02301 0.01458 0.01444 0.01402 0.01441 0.02786 0.01351 0.01154 0.01132 0.01550 0.01475 0.03180 0.03206 0.02344 0.01176 0.01451 0.01225 0.02196 0.02195 0.01080 0.01650 0.01147 0.02982 0.22531 0.01452 0.01267 0.01176 0.01099

± (pct) 0.7 0.9 0.7 1.0 0.6 1.1 1.0 1.5 1.0 0.8 0.4 0.7 1.8 0.9 0.8 0.6 1.1 0.5 1.3 0.7 0.6 0.5 0.7 0.6 0.3 0.9 0.5 0.4 0.8 0.7 0.7 0.9 1.1 0.5 0.7 0.5 0.7 1.3 1.4 0.9 1.1 0.6 0.7 1.2 0.3 0.5 1.4 1.1

205

Pb/235U ratio

0.16247 0.08991 0.09044 0.15267 0.10814 0.20774 0.10303 0.10464 0.14596 0.08657 0.11246 0.07815 0.21820 0.09991 0.10791 0.06267 0.13672 0.15432 0.11339 0.11072 0.17372 0.11505 0.09387 0.09031 0.10482 0.19307 0.09292 0.08626 0.08583 0.10353 0.09983 0.28310 0.23295 0.14014 0.08861 0.09262 0.07430 0.16703 0.15348 0.09186 0.10980 0.07191 0.21322 2.76964 0.10509 0.09377 0.09035 0.08471

± (pct) 3.0 12.0 4.9 13.2 2.3 6.6 26.6 16.7 7.2 28.4 2.5 5.7 7.4 4.4 25.5 10.1 4.6 36.8 6.2 16.8 6.4 3.0 64.5 89.8 36.2 16.5 110.1 1.9 3.9 6.4 15.1 18.3 2.8 10.0 6.7 16.0 29.8 6.9 7.6 10.4 9.8 18.7 1.6 10.1 5.0 8.6 10.6 18.5

206

Pb/207Pb ratio

19.70 21.77 22.16 20.72 18.73 16.33 20.08 17.07 21.14 22.95 18.57 20.02 14.43 19.66 19.57 24.69 18.62 20.46 18.13 19.77 18.26 17.47 21.21 21.41 18.95 19.90 20.05 18.44 18.18 20.64 20.37 15.49 18.97 23.07 18.30 21.60 22.73 18.13 19.72 16.22 20.72 22.00 19.28 11.22 19.05 18.63 17.94 17.90

± (pct) 2.9 12.0 4.8 13.1 2.2 6.5 26.6 16.6 7.1 28.3 2.5 5.7 7.2 4.3 25.5 10.1 4.4 36.8 6.0 16.8 6.4 2.9 64.5 89.8 36.2 16.5 110.1 1.8 3.9 6.4 15.1 18.3 2.6 10.0 6.7 16.0 29.8 6.8 7.5 10.3 9.7 18.6 1.4 10.0 5.0 8.6 10.5 18.4

Error correlation 0.23 0.08 0.14 0.07 0.25 0.16 0.04 0.09 0.14 0.03 0.16 0.12 0.25 0.21 0.03 0.06 0.24 0.01 0.21 0.04 0.10 0.18 0.01 0.01 0.01 0.06 0.00 0.19 0.20 0.11 0.05 0.05 0.38 0.05 0.10 0.03 0.02 0.19 0.19 0.08 0.11 0.03 0.44 0.12 0.06 0.05 0.13 0.06

206

Pb/238U age (m.y.)

148.0 90.9 93.0 146.2 94.0 156.7 96.0 83.0 142.7 92.2 96.9 72.7 145.5 91.2 98.0 71.9 117.9 145.9 95.4 101.6 146.6 93.3 92.4 89.8 92.2 177.2 86.5 74.0 72.6 99.1 94.4 201.8 203.4 149.4 75.4 92.8 78.5 140.1 139.9 69.3 105.5 73.5 189.4 1,309.9 92.9 81.2 75.4 70.5

± (m.y.) 1.0 0.8 0.6 1.4 0.5 1.7 0.9 1.2 1.5 0.7 0.4 0.5 2.7 0.9 0.8 0.4 1.3 0.8 1.2 0.8 0.9 0.5 0.6 0.6 0.3 1.6 0.4 0.3 0.6 0.7 0.7 1.9 2.2 0.8 0.5 0.5 0.6 1.8 2.0 0.6 1.2 0.5 1.3 17.4 0.3 0.4 1.1 0.8

207

Pb/235U ± age (m.y.) (m.y.)

152.9 87.4 87.9 144.3 104.3 191.7 99.6 101.1 138.3 84.3 108.2 76.4 200.4 96.7 104.1 61.7 130.1 145.7 109.1 106.6 162.6 110.6 91.1 87.8 101.2 179.2 90.2 84.0 83.6 100.0 96.6 253.1 212.6 133.2 86.2 89.9 72.8 156.8 145.0 89.2 105.8 70.5 196.3 1,347.4 101.5 91.0 87.8 82.6

4.9 10.9 4.5 20.2 2.5 13.7 27.5 17.6 10.6 24.6 2.9 4.5 16.2 4.5 27.6 6.4 6.3 56.1 7.1 18.7 11.3 3.4 59.7 79.2 37.8 31.9 98.9 1.6 3.4 6.7 15.2 51.3 6.7 14.1 6.0 14.9 22.2 11.7 11.8 9.6 10.8 13.5 3.4 250.1 5.3 8.2 9.7 15.8

206

Pb/207Pb age (m.y.)

230 –6 –49 113 346 648 186 552 64 –135 365 193 908 234 245 –318 359 142 419 221 402 501 56 35 319 207 189 380 412 121 152 761 316 –147 398 14 –111 418 228 662 112 –31 279 1,407 308 358 442 448

± (m.y.) 33 145 59 155 25 69 310 182 85 351 28 66 74 50 294 130 50 432 67 194 71 32 769 1,076 411 191 1,281 21 43 75 177 193 30 124 75 192 366 76 87 111 115 226 16 96 57 97 117 205

Table 2 19

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

U content (ppm)


Analysis

U content (ppm)

206

Pb/204Pb ratio

U/Th ratio

206

Pb/208Pb ratio

± (pct)

205

Pb/235U ratio

± (pct)

206

Pb/207Pb ratio

± (pct)

Error correlation

206

Pb/238U age (m.y.)

± (m.y.)

207

Pb/235U ± age (m.y.) (m.y.)

206

Pb/207Pb age (m.y.)

± (m.y.)

–65 –615 185 110 359 566 74 108 –5 153 –180 –313 –128 103 –142 –57 –485 –15 139 348 359 102 601 390 398 –22 –408 141 –563 60 –49 281 –56 –93 –152 –38 –34 –52 433 –188 583 –521 –127 –275 157 285

63 473 129 170 252 147 39 99 161 46 109 121 100 44 121 45 152 45 78 165 123 118 103 23 113 123 213 145 118 69 107 83 80 171 194 308 60 122 14 106 130 179 200 160 106 145

Sample 66

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

136 49 57 124 43 68 176 102 97 309 67 72 67 191 84 200 55 199 135 83 87 82 74 118 108 62 105 53 41 77 181 124 157 87 57 35 156 67 692 73 95 71 39 57 80 59

1,409 1,124 1,371 1,621 838 571 3,182 2,019 1,765 2,455 1,057 1,088 1,142 1,602 1,304 1,651 1,226 2,367 2,082 2,412 2,277 1,378 2,119 5,593 1,542 1,229 1,818 1,574 1,277 1,569 943 1,511 2,551 1,780 1,352 2,015 4,133 3,413 18,764 2,193 1,589 1,869 1,109 1,392 1,886 1,023

33 38 24 58 26 19 22 24 30 20 23 57 66 19 32 20 17 25 32 22 32 27 19 21 22 19 20 25 21 40 19 26 18 31 15 30 28 18 14 22 62 24 33 16 23 30

0.03093 0.01673 0.02531 0.01765 0.02652 0.01961 0.02363 0.02484 0.01687 0.01627 0.01970 0.01660 0.02296 0.01609 0.01717 0.01618 0.02506 0.01629 0.01660 0.01802 0.02389 0.02507 0.02667 0.05711 0.01939 0.02405 0.01638 0.02400 0.02514 0.02551 0.01578 0.01618 0.01652 0.01806 0.02418 0.02549 0.02444 0.02427 0.03556 0.03373 0.03730 0.02470 0.02519 0.02364 0.01693 0.01930

1.6 1.5 0.9 36.2 1.7 1.4 2.3 2.2 1.0 1.5 2.5 2.8 3.2 1.6 1.9 2.2 1.1 1.8 0.9 2.2 2.2 2.0 1.6 1.4 1.2 1.9 1.7 1.1 1.1 1.7 2.0 1.2 1.5 2.6 1.6 2.1 1.6 1.2 2.3 4.2 5.1 1.8 1.8 1.8 1.5 2.8

0.19120 0.08353 0.17375 0.11735 0.19644 0.15948 0.15470 0.16502 0.10689 0.11017 0.11622 0.09292 0.13832 0.10667 0.10284 0.10037 0.13134 0.10275 0.11173 0.13285 0.17692 0.16606 0.22040 0.42880 0.14609 0.15134 0.08838 0.16165 0.12795 0.16608 0.09816 0.11573 0.10246 0.11037 0.14425 0.15932 0.15304 0.15077 0.27225 0.19837 0.30566 0.12768 0.15179 0.13432 0.11483 0.13833

5.4 34.7 11.2 39.0 22.4 13.6 4.0 8.7 13.4 4.2 9.1 9.9 8.7 4.0 10.0 4.3 11.5 4.1 6.7 14.8 11.1 10.2 9.6 2.5 10.2 10.4 16.4 12.4 8.9 6.1 9.1 7.4 6.7 14.2 15.7 25.5 5.2 10.1 2.6 9.5 13.0 13.5 16.3 12.7 9.2 13.0

22.31 27.62 20.09 20.74 18.62 16.96 21.06 20.75 21.76 20.36 23.37 24.63 22.89 20.80 23.02 22.23 26.31 21.86 20.49 18.71 18.62 20.81 16.69 18.36 18.30 21.92 25.56 20.47 27.09 21.18 22.16 19.27 22.23 22.56 23.11 22.06 22.02 22.19 18.01 23.45 16.83 26.67 22.88 24.27 20.33 19.23

5.2 34.7 11.1 14.4 22.4 13.5 3.3 8.4 13.3 3.9 8.8 9.5 8.1 3.7 9.8 3.7 11.5 3.7 6.6 14.6 10.9 10.0 9.5 2.1 10.1 10.2 16.3 12.4 8.8 5.8 8.8 7.3 6.5 13.9 15.6 25.4 5.0 10.0 1.3 8.5 12.0 13.4 16.2 12.6 9.1 12.7

0.29 0.04 0.08 0.93 0.07 0.10 0.57 0.25 0.08 0.35 0.28 0.29 0.37 0.39 0.19 0.50 0.10 0.44 0.14 0.15 0.20 0.19 0.17 0.57 0.12 0.19 0.11 0.09 0.12 0.28 0.23 0.17 0.22 0.19 0.10 0.08 0.31 0.12 0.87 0.44 0.39 0.13 0.11 0.14 0.16 0.22

196.4 107.0 161.2 112.8 168.8 125.2 150.5 158.2 107.8 104.1 125.7 106.1 146.3 102.9 109.7 103.5 159.6 104.2 106.1 115.2 152.2 159.6 169.7 358.0 123.8 153.2 104.7 152.9 160.1 162.4 100.9 103.4 105.6 115.4 154.0 162.3 155.7 154.6 225.3 213.9 236.1 157.3 160.4 150.6 108.2 123.2

3.1 1.6 1.5 41.1 2.9 1.7 3.5 3.5 1.1 1.5 3.2 3.0 4.7 1.6 2.1 2.3 1.8 1.9 1.0 2.5 3.4 3.1 2.8 5.2 1.5 3.0 1.8 1.7 1.8 2.8 2.1 1.3 1.6 3.1 2.5 3.5 2.6 1.8 5.2 9.1 12.2 2.8 3.0 2.7 1.6 3.5

177.7 81.5 162.7 112.7 182.1 150.2 146.1 155.1 103.1 106.1 111.6 90.2 131.5 102.9 99.4 97.1 125.3 99.3 107.6 126.7 165.4 156.0 202.2 362.3 138.5 143.1 86.0 152.1 122.3 156.0 95.1 111.2 99.0 106.3 136.8 150.1 144.6 142.6 244.5 183.7 270.8 122.0 143.5 128.0 110.4 131.6

10.4 29.0 19.5 45.4 43.8 21.7 6.3 14.5 14.4 4.7 10.7 9.3 12.1 4.3 10.4 4.4 15.3 4.3 7.6 19.8 19.8 17.0 21.3 10.8 15.0 15.8 14.6 20.2 11.4 10.2 9.0 8.6 6.9 15.8 22.8 40.4 8.1 15.3 7.2 18.9 39.5 17.4 24.9 17.1 10.6 18.0




Analysis

47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

U content (ppm) 89 68 83 104 78 62 161 108 97 111 90 37 47 670 72 57 57 144 51 60 73 88 67 60

206

Pb/204Pb ratio

646 1,578 2,033 3,325 1,201 1,838 2,911 1,742 1,993 2,437 1,562 301 1,181 10,910 846 1,547 3,359 2,468 1,631 1,327 1,711 1,397 925 1,405

U/Th ratio

51 32 75 42 32 22 21 56 24 23 63 33 33 12 35 43 55 33 120 30 29 23 57 42

206

Pb/208Pb ratio

0.02134 0.02341 0.01885 0.02513 0.02468 0.02624 0.02518 0.01740 0.01630 0.01608 0.01706 0.01702 0.02343 0.01594 0.01640 0.02472 0.05664 0.01649 0.02400 0.02368 0.02584 0.01622 0.01816 0.01491

± (pct)

1.5 1.7 2.3 1.1 1.0 2.4 2.0 2.7 1.7 2.5 2.1 3.5 1.3 1.5 1.7 2.8 4.2 1.9 5.6 3.4 1.2 2.3 1.4 3.5

205

Pb/235U ratio

0.16572 0.14529 0.10998 0.16130 0.18417 0.20637 0.16737 0.11020 0.10475 0.11789 0.13934 0.08843 0.13513 0.10848 0.10256 0.18774 0.43978 0.12716 0.15258 0.13297 0.21168 0.10255 0.11657 0.09236

± (pct)

6.8 4.8 16.2 6.3 7.5 10.6 4.5 8.0 6.4 12.1 12.6 20.8 12.0 2.6 18.9 13.9 6.2 7.5 6.3 15.8 13.7 15.5 28.0 48.0

206

Pb/207Pb ratio

17.76 22.21 23.64 21.48 18.48 17.53 20.74 21.77 21.46 18.81 16.88 26.54 23.90 20.27 22.05 18.16 17.76 17.88 21.69 24.56 16.83 21.81 21.49 22.26

± (pct)

Error correlation

206

Pb/238U age (m.y.)

± (m.y.)

207

Pb/235U ± age (m.y.) (m.y.)

206

Pb/207Pb ± age (m.y.) (m.y.)

6.6 4.5 16.1 6.2 7.4 10.4 4.0 7.5 6.1 11.9 12.4 20.5 11.9 2.2 18.8 13.6 4.6 7.3 3.0 15.4 13.6 15.3 28.0 47.9

0.22 0.35 0.14 0.18 0.13 0.22 0.44 0.34 0.27 0.21 0.17 0.17 0.11 0.56 0.09 0.20 0.68 0.25 0.88 0.22 0.09 0.15 0.05 0.07

136.1 149.2 120.4 160.0 157.2 167.0 160.3 111.2 104.3 102.9 109.1 108.8 149.3 102.0 104.9 157.4 355.2 105.5 152.9 150.9 164.5 103.7 116.0 95.4

2.0 2.5 2.8 1.8 1.5 4.0 3.2 3.1 1.8 2.6 2.3 3.8 2.0 1.5 1.7 4.5 15.2 2.0 8.6 5.2 2.0 2.4 1.6 3.4

155.7 137.7 105.9 151.8 171.6 190.5 157.1 106.1 101.2 113.2 132.5 86.0 128.7 104.6 99.1 174.7 370.1 121.5 144.2 126.8 195.0 99.1 112.0 89.7

11.3 7.1 18.0 10.2 13.9 22.0 7.6 8.9 6.7 14.4 17.7 18.5 16.3 2.9 19.5 26.1 27.2 9.7 9.8 21.0 29.0 16.0 32.6 44.0

465 –55 –208 26 376 493 109 –5 29 336 576 –508 –236 164 –37 415 465 449 3 –305 582 –10 26 –59

73 55 202 74 83 114 48 90 73 134 135 274 150 25 229 152 50 81 37 197 148 185 335 583

1.9 3.5 6.2 9.8 14.5 30.7 10.3 4.4 4.7 7.5 3.2 3.1 5.7 2.3 21.3 12.7 2.2 1.1 21.8 68.9 1.8

0.43 0.23 0.05 0.09 0.09 0.05 0.15 0.18 0.14 0.14 0.23 0.36 0.18 0.22 0.05 0.09 0.26 0.53 0.05 0.03 0.30

101.1 148.4 168.3 107.1 144.1 106.0 227.9 166.4 115.5 108.5 170.3 151.2 156.1 107.6 99.3 104.9 110.6 217.3 101.4 106.2 152.2

0.9 1.2 0.6 0.9 1.9 1.5 3.6 1.4 0.8 1.1 1.3 1.9 1.7 0.6 1.0 1.1 0.7 1.5 1.0 2.1 0.9

95.8 203.4 214.5 88.1 119.2 76.8 226.6 159.3 118.8 95.5 172.9 142.4 157.8 111.3 89.4 96.3 153.8 213.6 96.2 73.5 157.9

2.2 8.1 14.7 9.0 18.2 24.2 26.0 7.7 5.9 7.5 6.2 5.1 9.9 2.8 19.7 12.8 3.7 3.1 21.8 51.2 3.3

–35 901 757 –399 –354 –760 213 55 186 –218 209 –2 185 192 –166 –110 884 173 –29 –895 246

24 36 65 128 187 431 119 53 54 94 37 38 67 27 265 156 22 13 264 999 21

Sample 67

351 428 262 17 40 60 15 20 90 118 94 23 101 99 74 25 152 95 100 140 131

9,857 12,170 14,409 3,028 1,499 1,279 2,597 4,372 12,933 4,243 6,032 5,068 5,537 8,935 7,615 7,121 9,871 7,753 6,031 712 13,782

332 413 69 696 60 47 46 351 26 527 33 361 19 30 44 420 1,178 140 199 181 524

0.01581 0.02329 0.02645 0.01675 0.02261 0.01658 0.03599 0.02615 0.01808 0.01697 0.02677 0.02373 0.02451 0.01683 0.01640 0.01552 0.01731 0.03429 0.01585 0.01661 0.02388

0.9 0.8 0.3 0.9 1.3 1.4 1.5 0.8 0.7 1.0 0.8 1.2 1.1 0.5 1.0 1.1 0.6 0.7 1.0 2.0 0.6

0.09892 0.22182 0.23517 0.09069 0.12452 0.07857 0.25001 0.16989 0.12414 0.09861 0.18569 0.15052 0.16819 0.11587 0.09205 0.09951 0.16349 0.23412 0.09940 0.07504 0.16830

2.2 3.6 6.2 9.9 14.5 30.7 10.4 4.5 4.7 7.6 3.3 3.4 5.8 2.4 21.3 12.7 2.2 1.3 21.8 69.0 1.9

22.04 14.48 15.51 25.47 25.03 29.10 19.85 21.22 20.08 23.73 19.88 21.74 20.09 20.03 23.25 22.73 14.60 20.19 21.98 30.51 19.57

Table 2 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21


Analysis

22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72

U content (ppm) 80 75 174 49 64 491 173 86 195 83 252 86 134 67 250 156 200 144 112 189 144 84 80 95 149 120 140 83 63 136 127 176 236 72 87 134 152 29 123 169 75 54 84 116 75 159 79 162 351 428

206

Pb/204Pb ratio

30,177 31,137 9,836 14,056 7,449 5,047 7,064 13,376 8,857 5,270 2,185 328,263 359,267 57,499 6,817 3,704 5,147 12,849 6,683 4,857 8,257 27,516 59,155 3,013 3,109 5,575 7,197 56,074 68,167 13,640 9,398 10,779 13,057 37,851 91,888 10,571 3,420 8,657 26,665 7,583 35,515 6,482 30,396 7,549 17,178 14,525 38,454 6,862 4,928 6,085

U/Th ratio 310 761 1,071 613 353 699 874 473 1,709 772 276 273 1,017 642 141 375 600 2,884 1,391 289 829 717 270 496 395 325 930 579 589 1,307 450 433 598 651 281 1,342 313 296 885 302 559 195 400 1,033 840 2,129 208 1,124 340 588

Pb/208Pb ratio

± (pct)

0.03622 0.01661 0.01671 0.01702 0.01757 0.01651 0.01613 0.01640 0.01638 0.01608 0.02455 0.01727 0.02486 0.01571 0.02578 0.01649 0.02637 0.01717 0.01599 0.01596 0.01610 0.01624 0.02505 0.03504 0.03086 0.01664 0.01576 0.01541 0.01842 0.03566 0.02522 0.01634 0.01659 0.01722 0.01582 0.01604 0.02427 0.01627 0.02446 0.01661 0.02469 0.02436 0.01623 0.01718 0.01607 0.01680 0.02458 0.01613 0.01622 0.01721

0.8 0.5 0.7 1.0 0.8 0.7 0.8 1.6 0.9 0.8 1.5 0.6 0.7 0.8 1.0 0.3 1.3 0.8 0.4 0.5 0.5 0.6 1.5 0.8 1.7 0.7 1.0 0.8 1.8 1.0 0.7 0.8 0.9 0.4 0.6 0.7 0.7 0.7 0.6 0.4 0.5 0.9 0.7 0.7 0.4 0.5 1.0 0.5 0.6 1.2

206

205

Pb/235U ratio

0.27452 0.12607 0.10260 0.11321 0.10713 0.10751 0.10658 0.13475 0.11190 0.09930 0.14990 0.12217 0.18770 0.11247 0.17314 0.11106 0.18161 0.12969 0.11096 0.10463 0.14396 0.11178 0.19207 0.22701 0.18757 0.15150 0.10425 0.13274 0.15256 0.24874 0.17441 0.12017 0.11286 0.11072 0.10011 0.11428 0.17284 0.09600 0.16215 0.11163 0.16793 0.16369 0.10086 0.11840 0.11113 0.11023 0.17568 0.10965 0.09962 0.16509

± (pct) 1.5 4.9 18.1 10.3 35.3 4.2 3.7 6.1 13.8 6.6 55.8 6.4 4.8 3.8 19.1 4.8 32.3 6.4 13.1 27.6 4.6 5.0 2.3 38.0 4.2 5.0 4.9 8.4 6.0 5.4 16.3 3.0 9.8 2.7 5.7 5.1 5.3 6.3 3.0 2.5 0.7 5.3 8.0 2.2 3.3 2.8 4.2 7.4 25.9 7.4

Pb/207Pb ratio

± (pct)

Error correlation

18.19 18.17 22.46 20.73 22.61 21.18 20.87 16.78 20.18 22.33 22.58 19.49 18.26 19.26 20.53 20.48 20.02 18.26 19.87 21.03 15.42 20.03 17.99 21.28 22.69 15.15 20.84 16.00 16.65 19.77 19.94 18.75 20.27 21.44 21.80 19.35 19.36 23.36 20.80 20.51 20.27 20.52 22.18 20.00 19.93 21.02 19.29 20.29 22.45 14.38

1.3 4.9 18.1 10.2 35.3 4.1 3.6 5.9 13.7 6.6 55.8 6.3 4.8 3.7 19.0 4.8 32.3 6.3 13.1 27.6 4.6 4.9 1.7 38.0 3.9 5.0 4.8 8.3 5.7 5.3 16.3 2.9 9.7 2.7 5.6 5.0 5.2 6.3 2.9 2.4 0.5 5.3 8.0 2.1 3.3 2.8 4.1 7.4 25.9 7.3

0.52 0.09 0.04 0.10 0.02 0.17 0.22 0.26 0.06 0.12 0.03 0.10 0.14 0.20 0.05 0.06 0.04 0.12 0.03 0.02 0.11 0.11 0.65 0.02 0.41 0.15 0.20 0.10 0.30 0.19 0.04 0.27 0.10 0.14 0.10 0.14 0.14 0.10 0.19 0.18 0.69 0.16 0.09 0.33 0.11 0.16 0.24 0.07 0.02 0.16

206

206

Pb/238U age (m.y.)

229.4 106.2 106.8 108.8 112.3 105.6 103.2 104.9 104.7 102.8 156.4 110.4 158.3 100.5 164.1 105.5 167.8 109.7 102.3 102.0 102.9 103.8 159.5 222.0 196.0 106.4 100.8 98.6 117.7 225.9 160.6 104.5 106.1 110.0 101.2 102.6 154.6 104.0 155.8 106.2 157.2 155.2 103.8 109.8 102.7 107.4 156.6 103.2 103.7 110.0

± (m.y.) 1.9 0.5 0.7 1.1 0.9 0.7 0.9 1.7 0.9 0.8 2.4 0.7 1.1 0.8 1.6 0.3 2.2 0.9 0.4 0.5 0.5 0.6 2.4 1.8 3.4 0.8 1.0 0.8 2.1 2.3 1.1 0.9 1.0 0.4 0.6 0.7 1.1 0.7 0.9 0.5 0.8 1.3 0.7 0.8 0.4 0.5 1.6 0.5 0.6 1.3

207

Pb/235U ± age (m.y.) (m.y.)

246.3 120.6 99.2 108.9 103.3 103.7 102.8 128.4 107.7 96.1 141.8 117.0 174.7 108.2 162.1 106.9 169.4 123.8 106.8 101.0 136.6 107.6 178.4 207.7 174.6 143.2 100.7 126.6 144.2 225.6 163.2 115.2 108.6 106.6 96.9 109.9 161.9 93.1 152.6 107.5 157.6 153.9 97.6 113.6 107.0 106.2 164.3 105.6 96.4 155.1

4.3 6.3 18.7 11.8 37.7 4.5 4.0 8.4 15.5 6.6 81.6 7.8 9.1 4.3 33.0 5.4 57.8 8.3 14.6 28.9 6.7 5.6 4.5 84.0 8.0 7.7 5.2 11.2 9.2 13.4 28.5 3.7 11.1 3.1 5.7 5.9 9.2 6.2 4.9 2.8 1.3 8.8 8.2 2.7 3.7 3.2 7.4 8.2 25.9 12.3

206

Pb/207Pb age (m.y.) 411 414 –81 111 –98 61 95 589 174 –67 –95 255 402 283 134 140 193 403 210 78 770 191 436 48 –106 807 98 691 606 222 202 343 164 31 –9 271 270 –179 103 136 163 135 –52 195 203 79 278 162 –80 915

± (m.y.) 15 55 221 121 434 49 43 64 160 80 685 73 53 43 224 56 375 71 152 327 48 57 19 454 47 52 57 89 61 61 189 33 114 32 68 57 60 79 34 29 6 62 97 24 38 33 46 86 317 75




Analysis

73 74 75

U content (ppm) 262 17 40

206

Pb/204Pb ratio 7,204 4,542 2,248

U/Th ratio 79 515 65

Pb/208Pb ratio

± (pct)

0.02433 0.02390 0.02192

0.7 0.5 0.7

206

205

Pb/235U ratio

0.15004 0.15570 0.14052

± (pct) 3.7 4.5 24.4

Pb/207Pb ratio

± (pct)

Error correlation

22.36 21.17 21.51

3.7 4.4 24.4

0.18 0.12 0.03

155.0 152.3 139.8

1.0 0.8 1.0

142.0 146.9 133.5

5.6 7.0 34.3

–70 62 23

45 53 293

26.1 32.3 7.5 3.5 4.4 4.8 2.1 2.7 38.5 10.0 12.2 12.5 10.7 11.5 11.9 4.5 4.5 5.3 12.9 4.8 20.9 31.2 12.8 11.1 15.9 7.8 6.0 3.8 15.8 9.7 16.9 0.6 4.1 8.7 9.1 2.5 4.1 4.8 8.5 10.4 4.1 8.6

0.03 0.04 0.13 0.22 0.18 0.24 0.43 0.34 0.07 0.12 0.30 0.06 0.09 0.17 0.11 0.16 0.10 0.13 0.09 0.17 0.07 0.08 0.11 0.09 0.21 0.14 0.23 0.23 0.06 0.10 0.09 0.87 0.32 0.10 0.27 0.31 0.20 0.43 0.23 0.28 0.22 0.25

145.7 99.3 97.1 382.6 151.8 89.6 164.9 263.2 117.2 147.7 176.8 142.6 143.6 103.2 144.1 87.2 93.9 91.1 145.0 95.7 137.3 169.4 145.3 97.8 108.4 96.7 145.8 132.1 91.7 144.5 93.5 203.1 97.6 95.6 147.3 211.8 99.8 104.2 155.5 153.9 151.7 168.0

1.3 1.3 0.9 3.2 1.2 1.1 1.6 2.6 3.4 1.8 7.0 1.1 1.3 2.0 1.9 0.6 0.4 0.6 1.7 0.8 2.2 4.5 2.0 1.0 3.6 1.1 2.1 1.2 0.9 1.4 1.5 2.1 1.4 0.8 3.8 1.8 0.8 2.4 3.2 4.6 1.4 3.7

99.8 70.7 77.3 368.7 131.3 86.5 166.7 249.1 98.2 130.4 162.6 119.6 133.4 93.8 128.3 75.4 95.8 84.0 114.1 95.0 114.1 237.1 118.5 108.0 110.5 95.7 133.3 138.7 75.5 105.7 57.9 210.4 85.6 96.3 107.2 200.5 95.5 94.5 140.2 145.5 145.5 163.7

27.0 23.4 6.0 16.0 6.3 4.4 4.2 8.0 39.0 13.9 22.3 15.8 15.1 11.4 16.3 3.5 4.5 4.7 15.5 4.8 25.0 80.4 16.0 12.6 18.8 7.9 8.8 5.8 12.3 10.8 10.0 2.8 3.9 8.8 10.7 5.8 4.2 5.3 13.0 16.7 6.5 15.7

–896 –817 –501 282 –225 1 192 118 –342 –174 –40 –316 –45 –139 –156 –285 142 –111 –490 78 –345 976 –391 339 156 72 –84 252 –410 –700 –1253 293 –239 114 –713 70 –9 –143 –112 12 44 102

378 460 99 40 56 58 24 32 496 125 148 161 129 143 148 57 53 65 171 57 270 318 166 125 186 93 74 44 206 134 265 7 52 103 127 30 50 60 105 124 48 102

206

206

Pb/238U age (m.y.)

± (m.y.)

207

Pb/235U ± age (m.y.) (m.y.)

206

Pb/207Pb ± age (m.y.) (m.y.)

Sample 69

25 45 103 53 81 179 201 100 47 59 73 61 89 71 37 119 249 137 66 200 40 22 43 104 63 132 73 74 68 48 41 1,341 242 114 61 120 173 124 65 60 134 70

842 1,015 1,379 3,941 1,903 2,316 5,794 4,728 1,924 1,659 1,770 2,065 4,392 677 1,265 2,020 5,577 2,654 3,275 6,985 1,358 561 1,243 4,837 996 6,975 2,150 3,609 1,088 1,170 648 45,289 3,240 2,683 1,836 4,992 3,576 2,362 1,851 1,462 4,246 1,949

40 43 33 61 64 47 43 42 57 20 55 59 19 36 25 53 35 20 24 25 31 250 18 65 76 29 26 17 24 21 68 10 52 23 38 26 19 29 21 46 15 35

0.02287 0.01553 0.01518 0.06115 0.02382 0.01400 0.02591 0.04168 0.01835 0.02317 0.02781 0.02236 0.02252 0.01614 0.02261 0.01362 0.01468 0.01422 0.02275 0.01496 0.02152 0.02662 0.02280 0.01529 0.01696 0.01511 0.02288 0.02071 0.01433 0.02267 0.01462 0.03200 0.01526 0.01494 0.02312 0.03340 0.01559 0.01629 0.02442 0.02416 0.02381 0.02641

0.9 1.3 0.9 0.8 0.8 1.2 1.0 1.0 2.9 1.2 3.9 0.8 0.9 1.9 1.3 0.7 0.5 0.7 1.2 0.8 1.6 2.6 1.4 1.1 3.3 1.1 1.4 0.9 1.0 1.0 1.6 1.0 1.4 0.9 2.5 0.8 0.9 2.3 2.0 3.0 0.9 2.2

0.10330 0.07209 0.07907 0.43786 0.13803 0.08890 0.17838 0.27805 0.10152 0.13700 0.17364 0.12505 0.14038 0.09680 0.13465 0.07704 0.09890 0.08627 0.11896 0.09813 0.11897 0.26297 0.12379 0.11228 0.11500 0.09885 0.14034 0.14631 0.07724 0.10972 0.05866 0.23019 0.08797 0.09948 0.11138 0.21836 0.09863 0.09755 0.14806 0.15412 0.15401 0.17493

26.1 32.3 7.5 3.6 4.5 4.9 2.3 2.9 38.6 10.1 12.8 12.6 10.7 11.7 12.0 4.5 4.5 5.4 12.9 4.9 21.0 31.4 12.9 11.1 16.3 7.9 6.2 3.9 15.8 9.7 16.9 1.2 4.4 8.7 9.5 2.6 4.2 5.4 8.7 10.8 4.2 8.9

30.52 29.70 26.47 19.26 23.80 21.71 20.03 20.67 24.92 23.32 22.08 24.66 22.12 22.99 23.15 24.37 20.46 22.73 26.36 21.02 24.95 13.96 25.39 18.78 20.34 21.07 22.48 19.51 25.58 28.48 34.36 19.17 23.92 20.70 28.62 21.09 21.80 23.03 22.74 21.61 21.32 20.81

Table 2 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42


Analysis

43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

U content (ppm) 68 137 79 112 83 305 229 133 267 68 471 137 179 295 69 69 105 194 77 745 106 90 198 77 67 86 163 135

206

Pb/204Pb ratio

2,025 3,031 2,484 2,152 2,526 6,703 5,653 3,874 3,995 1,714 5,846 2,823 4,260 6,890 2,487 1,265 3,750 5,028 1,922 5,856 1,852 955 2,938 1,443 1,261 1,120 2,549 2,362

U/Th ratio 28 22 54 24 44 14 40 73 52 79 47 71 38 22 25 30 53 14 31 43 101 70 55 61 56 28 21 28

206

Pb/208Pb ratio

0.02839 0.02255 0.03677 0.02173 0.02592 0.02118 0.03472 0.02510 0.01966 0.02576 0.01612 0.01984 0.02394 0.02318 0.02776 0.02553 0.02343 0.03107 0.02295 0.02696 0.02113 0.02381 0.01595 0.02278 0.02467 0.01566 0.02237 0.01571

± (pct) 3.2 0.9 0.5 0.6 1.0 1.3 0.6 2.6 3.7 1.5 1.5 2.0 1.4 0.8 2.6 2.2 1.9 0.9 1.6 1.5 2.6 1.3 1.5 1.0 4.5 1.4 0.9 0.7

205

Pb/235U ratio

0.16739 0.14658 0.24964 0.13592 0.17981 0.14224 0.25251 0.17077 0.13103 0.19141 0.10415 0.13186 0.15326 0.15826 0.19558 0.13430 0.16386 0.21431 0.14263 0.18534 0.13920 0.14263 0.10277 0.11866 0.15255 0.08348 0.16881 0.11183

± (pct) 8.3 3.6 6.3 7.4 3.5 2.7 1.8 5.2 5.0 8.3 1.9 5.2 4.5 2.0 8.2 4.6 4.8 2.0 5.8 2.2 14.1 5.6 4.2 10.6 9.5 9.0 6.4 7.7

206

Pb/207Pb ratio

23.39 21.22 20.31 22.04 19.88 20.53 18.96 20.27 20.69 18.56 21.34 20.75 21.53 20.20 19.57 26.21 19.71 19.99 22.19 20.06 20.93 23.01 21.40 26.46 22.30 25.86 18.28 19.37

± (pct) 7.7 3.4 6.2 7.4 3.4 2.3 1.7 4.5 3.4 8.2 1.3 4.8 4.3 1.9 7.8 4.1 4.4 1.8 5.6 1.6 13.8 5.5 3.9 10.5 8.4 8.9 6.3 7.7

Error correlation 0.38 0.25 0.08 0.08 0.28 0.49 0.35 0.50 0.74 0.18 0.76 0.38 0.30 0.39 0.32 0.46 0.39 0.46 0.28 0.68 0.19 0.22 0.36 0.09 0.47 0.15 0.14 0.09

206

Pb/238U age (m.y.)

180.5 143.8 232.8 138.6 165.0 135.1 220.0 159.8 125.5 164.0 103.1 126.7 152.5 147.7 176.5 162.5 149.3 197.3 146.3 171.5 134.8 151.7 102.0 145.2 157.1 100.1 142.6 100.5

± (m.y.) 5.8 1.3 1.1 0.9 1.7 1.8 1.4 4.2 4.7 2.5 1.5 2.5 2.1 1.2 4.6 3.5 2.8 1.8 2.4 2.6 3.6 1.9 1.6 1.5 7.2 1.4 1.3 0.7

207

Pb/235U ± age (m.y.) (m.y.)

157.1 138.9 226.3 129.4 167.9 135.0 228.6 160.1 125.0 177.8 100.6 125.8 144.8 149.2 181.4 128.0 154.1 197.2 135.4 172.6 132.3 135.4 99.3 113.9 144.2 81.4 158.4 107.6

14.0 5.3 15.7 10.2 6.4 3.9 4.6 9.0 6.6 16.0 2.0 6.9 7.0 3.2 16.2 6.3 7.9 4.3 8.4 4.1 19.7 8.1 4.4 12.7 14.6 7.6 10.9 8.7

206

Pb/207Pb age (m.y.)

–182 56 159 –36 209 134 318 164 115 367 43 109 21 172 245 –474 228 196 –52 188 88 –142 35 –500 –64 –439 401 269

± (m.y.) 96 41 73 90 39 28 19 53 40 92 15 57 52 22 90 54 51 21 68 19 164 68 47 140 102 117 71 88


Table 2. Analytical data on detrital zircons.