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Stratigraphy of the and Rocks of East-Central Alaska

GEOLOGICAL SURVEY PROFESSIONAL PAPER 559-A Stratigraphy of the Cambrian and Ordovician Rocks of East-Central Alaska

By EARL E. BRABB

LOWER AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 559-A

Descriptions of four newly named formations of Early Cambrian to Middle Ordovician age^ and their ecological implications; with a list of lower Paleozoic collections

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY William T. , Director

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 30 cents (paper cover) CONTENTS

Cambrian and Ordovician rocks Continued Page Abstract.. _ -___--______-_____ Al Unnamed chert, shale, and .______A19 Introduction. ______1 Paleotectonic implications.______19 rocks ______3 Facies and their ecological implications.______19 Tindir Group______3 Early Cambrian.______19 Cambrian rocks.______Middle Cambrian..______21 Funnel Creek Limestone. __ Late Cambrian and Early Ordovician ______21 Adams Argillite______7 Middle or Late Ordovician______23 Cambrian and Ordovician rocks. 9 Hillard Limestone. ______9 Summary. ______23 Jones Ridge Limestone. 15 Lower Paleozoic fossil collections from east-central Lower member. ______15 Alaska------._____.______---_---___-- 23 Upper member. ______18 References cited______--_--_-_-_---_--_____- 30

ILLUSTRATIONS

FIGURE 1. Map showing areas of Cambrian and Ordovician rocks in Alaska. ______------A2 2. Columnar sections-_-_-_-_---______-_-_____-_-_----_------4 3. Locality map______-_____--______-___-_____-_-_---__-__------_------_- 6 4-12. Photographs showing 4. Lower Paleozoic sequence along Tatonduk River.______-__-----__-_--___-----__ 8 5. Cambrian sequence at east end of Limestone Hogback.______-______-__--___---_------9 6. Hillard Limestone near Hillard Peak______--_-_-_--__------10 7. Location of measured sections in Adams Peak-Yukon River area.______------__-- 11 8. Hillard Limestone and Adams Argillite near Adams Peak____-_--____-_--_------_---__- 11 9. Hillard Limestone on ridge and flatiron southwest of Adams Peak______12 10. Limestone edgewise conglomerate- ______-___-___-______------12 11. Limestone boulder conglomerate ledge along Tatonduk River.______--__-___-__-_-----_ 13 12. Contact between Jones Ridge Limestone and Tindir Group______-_------_- 16 13. Stratigraphic columns of lower Paleozoic formations in east-central Alaska.______17 14. Photograph showing upper part of Jones Ridge Limestone....------18 15. Lithofacies maps, Early to Late Cambrian___-__-__-______-_-____-.---_----_------20 16. Lithofacies maps, Late Cambrian to Middle or Late Ordovician______--_-__-__-_--__---___-__ 22 in

LOWER PALEOZOIC PALEONTOLOGY AO STRATIGRAPHY OF EAST-CENTRAL ALASKA

STRATIGRAPHY OF THE CAMBRIAN AND ORDOVIGIAN ROCKS OF EAST-CENTRAL ALASKA

By EARL E. BRABB

ABSTRACT of Middle and Late Cambrian age are present. Cairnes Four new formational names are herein established for the did not map the Cambrian rocks separately but included westernmost known exposures of Cambrian sedimentary rocks them in an undivided limestone and dolomite unit of in . The Funnel Creek Limestone and Adams Cambrian to age. Mertie (1930) subdivided Argillite of Early Cambrian age and the Hillard Limestone of the rocks of Cambrian and possible Cambrian age into Early Cambrian to Early Ordovician age are key formations in determining the structure and stratigraphy of the Hillard four unnamed formations plus the Tindir Group, and Peak to Hard Luck Creek area, and the largely coeval Jones he (1933) proposed the following classification which Ridge Limestone of Early Cambrian to Middle or Late Ordo­ until now has served as a standard: vician age forms spectacular cliffs and jagged peaks in the Jones Ridge-Squaw Mountain area. Facies maps prepared from meas­ 1. Tindir Group of pre-Middle Cambrian age (probably ured sections of these formations and from fossil determinations Precambrian). suggest that the Jones Ridge-Squaw Mountain area was some 2. Lower plate of Middle Cambrian limestone. sort of shoal or during part of the early Paleozoic, and that 3. A thin formation of slate and , also of Mid­ the Hillard Peak-Hard Luck Creek area was a turbulent marine dle Cambrian age. shelf that received considerable terrigenous material from un­ known sources, and possibly some material from the Jones Ridge- 4. Upper plate of Middle Cambrian limestone. Squaw Mountain shoal. 5. Upper Cambrian limestone which grades upward The area was uplifted, very gently folded, and eroded during without any noticeable straitigraphic or lithologic late or Arenigian (Early Ordovician) time. The break into Ordovician limestone. fold axes apparently trended northeast. Deposition resumed in latest Arenigian or earliest Llanvirnian (Early Ordovician) On his geologic map, Mertie (1933, pi. 7) shows an time in part of the area, and in Caradocian or Ashgillian additional limestone unit of Late Cambrian age which, (Middle or Late Ordovician) time in the Jones Ridge-Squaw for purposes of discussion, is here designated unit 5A. Mountain area. The collected by Mertie were not referred to The rapid changes in facies, the possibility of reeflike sedi­ mentation, and the occurrence of bitumen and other organic his map units but rather to series of the Cambrian, so matter in the rocks make the lower Paleozoic rocks attractive the relative stratigraphic position of these collections for petroleum exploration. is difficult to determine. For example, some of the archaeocyathids reported by Mertie are considered by INTRODUCTION Okulitch (1956, p. 725) to be of Early, not Middle, Undoubted Cambrian fossils in Alaska have been Cambrian age, but the relation of the rocks containing found only in the vicinity of Eagle (fig. 1). The re­ the archaeocyathids to rocks containing definite Middle gional significance of the rocks containing these fossils Cambrian is uncertain. Moreover, there seems rests largely on their unique geographic position as the to be no lithologic means for distinguishing his units 2, westernmost known exposures of Cambrian sedimentary 4, 5, and 5A. For these reasons, a new set of formations rocks in North America. The Cambrian section of the is established here on the basis of mapping of litho- Eagle area provides a critical link between the Cam­ logically separable units containing stratigraphically brian in southern parts of the Cordilleran geosyncline oriented fossil collections. and that in various parts of Asia and the Arctic. The Cambrian rocks described in this report were Fossils of definite Cambrian age in Alaska were first first examined in 1960 as part of a project to prepare a discovered by Cairnes (1914a) along the international regional geologic map (1:250,000) of the area between boundary in the vicinity of Eagle. L. D. Burling iden­ the Yukon and Porcupine Kivers and the U.S.- tified the fossils for Cairnes and determined that border. Preliminary geologic maps of some of this area Al A2 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

EXPLANATION

Area of predominantly carbonate rocks of Ordovician age

Area of predominantly siliceous rocks of Ordovician age

Area of known Cambrian and Ordovician rocks

Oldhamia, localities where rocks are probably of Cambrian age

REFERENCES 1 Steidmann and Cathcart (1922) airbanks 2 Eakin (1918) 3 Brown (1926) L 4 Sainsbury (1965) Big Delta 5 Brooks (1911) 6 Mertie(1937) 7 Churkin and Brabb (1965b) 8 Churkin and Brabb (1965b) 9 Kindle (1908) o 10 Cairnes (1914a, and unpub. data) .. Nabesna 11 Churkin and Brabb (1965b) ^'"""ti.Copper Center ' 12 This report 13 Buddington and Chapin (1929)

GULF OF ALASKA

OCEAN

FIGURE 1. Index map showing areas of Cambrian and Ordovician rocks in Alaska. Prepared by Michael Churkin, Jr. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A3 have been released as open-file reports of the U.S. Geo­ PRECAMBRIAN ROCKS logical Survey (Brabb and Churkin, 1964,1965). Ap­ TINDIR GROUP proximately 4 days during the summer of 1960 and 6 days during 1961 were spent examining the Cambrian A 5,000- to 25,000-foot-thick succession of limestone, rocks and collecting fossils from them. E. N. Passero dolomite, quartzite, shale, and greenstone along the and H. J. Eoepke in 1960 and J. C. Melik and E. L. Alaska-Yukon Territory boundary between the Yukon Taylor in 1961 assisted in the geologic work. Michael and Porcupine Eivers was named the Tindir Group by Churkin, Jr., geologist, and A. J. Aadland, field assist­ Cairnes (1914a). Mertie (1933) subdivided the Tindir , joined the project in May, 1962. During the sum­ Group into seven informal units, and the youngest of mer of 1962 transportation was to have been mainly by these, termed unit A by Mertie, is the oldest formation helicopter, but because of two crashes and other mechan­ shown on the columnar sections (fig. 2). ical mishaps we spent only 3 days travelling by heli­ Cairnes (1914a, p. 56) thought that the Tindir Group copter and boat and examining rocks of Cambrian age. is either entirely of Precambriaii age, or that it is Pre- E. J. Eoss, Jr., and L. E. Mayo, of the U.S. Geological cambrian and Early Cambrian. Mertie (1933, p. 392) Survey, joined the field party for 11 days in July and thought that the Tindir Group is probably Precam- spent about 3 of them examining and collecting Cam­ brian. Inasmuch as the oldest fossils they found brian rocks near Jones Eidge. In July 1963, the author, stratigraphically above the Tindir Group were con­ Churkin, A. E. Palmer, and D. L. Giles, field assistant, sidered to be of Middle Cambrian age, all they could spent 5 days examining Cambrian rocks along the definitely state is that the Tindir Group is not younger Yukon and Tatonduk Eivers, using boat transportation, than Middle Cambrian. and about 6 days examining, measuring, and collecting The oldest fossils collected stratigraphically above Cambrian rocks at other localities, using a helicopter. the Tindir Group during the present investigation are In total, therefore, less than a month was spent exam­ of Early Cambrian age, according to A. E. Palmer. ining Cambrian rocks in an area of complex geology The Tindir Group, therefore, is not younger than Early covering more than 70 square miles. Most of the sec­ Cambrian. tions were rather hurriedly measured and described, The age of the Tindir Group is related to the world­ and the thickness of some was only visually estimated. wide Precambrian-Cambrian boundary problem. I The -stratigraphic classification is thought to be a agree with Okulitch (1956) that the beginning of Cam­ substantial refinement of Mertie's (1933, p. 392) orig­ brian time should, on paleontologic grounds, coincide inal contribution, but it has not been tested by ex­ with the appearance of olenellid trilobites and (or) tensive detailed mapping. archaeocyathids and should, on stratigraphic grounds, Geologists following in our footsteps may find an be placed at some important discontinuity in the apparent lack of fossils in rocks where we made several stratigraphic section. To compromise with the pale­ collections. Many of our collections were from small ontologic approach, such a discontinuity should be as lenses that we completely removed. In general, the close as possible to, and below, the lowest Cambrian fossils are in coarse-grained limestone, although several fossils. In this part of Alaska, the lowest Cambrian rich faunas are from fine-grained limestone. Hook- fossils, consisting of archaeocyathids, were found about 500 feet stratigraphically above the top of unit A, the shaped cross sections of trilobites, along weathered sur­ highest unit of the Tindir Group in the Jones Eidge- faces perpendicular to the bedding of the limestone, Squaw Mountain area. No definite discontinuity has frequently led to the discovery of richly fossiliferous been recognized below these fossils, but there is an beds. All fossils are from rock in place unless other­ abrupt lithologic change from the dark platy limestone wise noted. of unit A to the archaeocyathid-bearing white limestone All the ages of fossils and rocks in this report were and dolomite stratigraphically above the Tindir Group. determined by A. E. Palmer, unless otherwise noted. The top of the Tindir Group is, therefore, provisionally Color terms are from the color chart of Goddard and and arbitrarily considered the top of the Precambrian others (1948). in east-central Alaska. A4 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

3 4 YUKON ADAMS RIVER PEAK

FEET °~1

H i

400-

Worm(?) borings 500- in quartzite

600- Red and green shale and siltstone

700 EXPLANATION 800 -

900-

1000-

1100-

1200- Limestone edgewise conglomerate 1300-

1400- Limestone boulder conglomerate

1500- Bioclastic limestone

1600-

1700-

1800- Sandstone and siltstone 1900- m Argillite and shale 2000-

2100- Covered

4375-CO 2200- US Geological Survey fossil collection No. 2300- .63ABa3331 2400- US Geological Survey field locality No. 2500- Formation boundary 2600- Dashed where approximately located; queried where doubtful 2700-

Series boundary 2800- Queried where doubtful

2900-

3000-

FIGURE 2. Columnar sections of Cambrian and Ordovician STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A5

5 9 RIDGE JONES AND RIDGE Black chert and FLATIRON 7 1 mile HARD LUCK southwest TATONDUK RIDGE of Adams RIVER 5 miles northeast CREEK Peak of Montauk Bluff

4369-CO FEET Breccia v^w x x x x x x r° Estimated thickness 4379-CO .4370-CQ P.3717-CO, 3718-CO of missing section 4326-CO Upper Cambrian Fauife

.4302-00 Red and green shale -400 4299-CO Archaeocyathids Glauconitic and phosphatic Greenish-gray in matrix sandstone and siltstone shale and argillite, - 500 quartz a chert gritst in float -600

- 700

-800

- 900

63ABa3331 Partly silicified - 1000 Mainly dolomite. Minor phosphatic limestone - 1100

- 1200

- 1300

- 1400

- 1500 Abundant silicified oolites and pisolites - 1600 Dark-gray platy limestone - 1700

- 1800 Dark-gray platy limestone - 1900

-2000

- 2100

- 2200

4301-CO (projected from - 2300 locality 3 miles southwest of sec­ -2400 tion) Archaeo­ cyathids Extensively silicifiec -2500

-2600

- 2700

Brownish-black lam­ - 2800 inated and platy limestone - 2900

-3000 rocks of east-central Alaska. Locations are shown in figure 3.

232-493 O <6 2 A6 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OP EAST-CENTRAL ALASKA

CAMBRIAN ROCKS 3 for localities) has been variously treated. Cairnes (1914b) included it within his undifferentiated carbon­ FUNNEL CHEEK LIMESTONE ate unit of Cambrian to Devonian age. Mertie (1933, A massive carbonate formation exposed in the pi. 7) included the formation (1) within his Upper vicinity of the Alaska-Yukon boundary between Funnel Cambrian limestone (his unit 5A) about 1 mile east Creek and Hillard Peak and between the Tatonduk and northeast of Hillard Peak, (2) as limestone of Si­ Eiver, Hard Luck Creek, and Montauk Bluff (see fig. lurian age in the vicinity of Funnel Creek, (3) as his

EXPLANATION

Sedimentary rocks, undivided Includes some Cambrian rocks along Funnel Creek

Jones Ridge Limestone Cambrian to Middle or Upper Ordovidan

XX134 X (4341-CO J 4344-CO I 4345-CO Triangulation station

Boundary monument Approximate location of major fault 64°55' Map base from U.S. Geological Survey Geology by Earl E. Brabb, 1960-63 Charley River A-l and Eagle D-l and Michael Churkin, Jr., 1962-63 Measured section Generalized attitude quadrangles (1:63,360), 1956 editions

6 MILES

FIGURE 3. Map showing location of sections and distribution of Cambrian and Ordovician formations. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A7 lower plate or part of his lower plate of Middle Cam­ tals are 10 mm long. There are a few dark-gray chert brian limestone (his unit 4) from Limestone Hogback nodules and many oolites in the limestone. A black to the Tatonduk Eiver, and (4) within the Tindir Group bituminous(?) mineral j possibly anthraxolite, is com­ between Hard Luck Creek and Montauk Bluff. Green mon along fractures and in the matrix of the limestone. and Eoddick (1962) mapped it in Canada within an The uppermost 15 feet of the formation along the river unnamed limestone and dolomite formation (their unit is, a breccia consisting of angular grit and pebble-size 6a) of Early (?) Cambrian to Ordovician(?) and pos­ fragments of limestone, dolomite, chert, and phosphate. sibly of Precambrian age. Bra'bb and Churkin mapped North of the Tatonduk River area, the Funnel Creek it (1964) as an unnamed dolomite formation in the Limestone is mainly dolomite. Along the ridges north­ Charley River quadrangle (1:250,000) and (1965) as east of Montauk Bluff the dolomite is very pale orange unnamed limestone formation in the Eagle D-l quad­ (10T72 6/2) and has interbeds of dark-yellowish-brown rangle (1: 63,360). It is here named the Funnel Creek (10T72 4/2) fine-grained phosphate limestone. Near Limestone for exposures 1-3 miles south and southwest Hard Luck Creek the dolomite is yellowish gray (5Y of the mouth of Funnel Creek. 8/1). The Funnel Creek Limestone extends in a nearly con­ The thickness of the Funnel Creek Limestone in its tinuous band from Hillard Peak to Montauk Bluff. It type area is not less than 1,300 feet, which is a partial extends into the Yukon Territory for at least 10 miles thickness because the base of the f ormation is not ex­ and may be present but unrecognized in more northerly posed there. Along Limestone Hogback it seems much areas along the boundary of the Yukon Territory and thinner, about 500 feet, but 1,200 feet of section below Alaska. the lowest exposure of Funnel Creek Limestone and the The type area of the Funnel Creek Limestone in­ highest exposure of the Tindir Group is covered. Sim­ cludes the valley walls of three unnamed tributaries of ilarly, in the Tatonduk River, Montauk Bluff, and Hard the Tatonduk River from 1 mile southwest to 3 miles Luck Creek areas the Funnel Creek Limestone seems due south of the mouth of Funnel Creek, in sections 17, to be 50-200 feet thick, but most of the section in these 20,21,27, and 28, T. 2 N., R. 33 E., where the formation areas is covered. forms craggy cliffs and scenic gorges. Information No fossils have been found in the Funnel Creek Lime­ from the type area has been combined in the composite stone. stratigraphic column (fig. 2, column 1). The contact of the Funnel Creek Limestone with the The gross appearance of the Funnel Creek Limestone Tindir Group is only rarely exposed, but the units seem at a distance is massive, very light gray (/V8) carbonate accordant throughout their known extent. Although rock having relatively few widely spaced bedding-plane no gradation or intercalations of lithologies were ob­ joints or parting surfaces. On close examination, how­ served across the contact, there is no reason why the ever, some of the rock has pale-yellowish-brown (10T72 units cannot be conformable. 6/2) laminations. Some of the rock is also oolitic lime­ The Funnel Creek Limestone is overlain by a forma­ stone and edgewise conglomerate consisting of lami­ tion containing fossils of Early Cambrian age. Inas­ nated slabs of limestone about 1 inch thick and 10 inches much as the top of the Tindir Group lias been designated in maximum dimension, inclined at angles to the gen­ the top of the Precambrian, the Funnel Creek Lime­ eral bedding and cemented by . stone is herein considered to be of Early Cambrian age. Almost all the Funnel Creek Limestone is carbonate ADAMS ARGILLITE rock, but not enough of the section has been examined to determine the proportion of limestone to dolomite. Mertie (1933) recognized and mapped a "slate" and The formation seems to be predominantly limestone. quartzite formation (his unit 3) between Hillard Peak There are a few thin interbeds of dark-gray chert. and Adams Peak. The formation was extended in a Secondary quartz replacing pisolites and oolites, chal­ continuous belt to the Montauk Bluff area by Brabb cedony-lined vugs, and irregularly shaped siliceous and Churkin (1964) and has been recognized by them veins in the limestone are common. in isolated patches as far west as the headwaters of the On the north valley slope of the Tatonduk River Black River, about 80 miles northwest of Adams Peak, a about three-quarters of a mile downstream from the newly named mountain between the Tatonduk and Na­ mouth of Pass Creek, the Funnel Creek Limestone forms tion Rivers (fig. 3). The formation is here named the a prominent cliff (fig. 4). The rock there is predom­ Adams Argillite for exposures in the vicinity of Adams inantly massive light-gray (NT) medium-grained lime­ Peak. stone that has been extensively silicified, dolomitized, No complete section of the Adams Argillite has been and recrystallized. Some of the secondary calcite crys­ found, but parts of it can be observed along the north A8 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

FIGTJKE 4. Lower Paleozoic sequence in the Tatonduk River area showing prominent cliff of Funnel Creek Limestone in fore­ ground and less conspicuous outcrops of overlying formations in middle background. The beds from which collection 4353-CO was obtained are thought to be faulted out at river level. View is northwest. bank of the Yukon Eiver about 1 mile south of Adams A variety of rocks make up the rest of the Adams Peak; along a small north-trending ridge at the east Argillite. The argillaceous rocks include gray, green, end of Limestone Hogback, about 3 miles east-southeast and red argillate and shale. Light--gray (5Y 5/2) of Adams Peak; at scattered localities 1-2 miles north argillate and interbeds of laminated quartzite and silt- and east of Hillard Peak; and along the north bank of stone are characteristic of the formation between Hard the Tatonduk Eiver about 3 miles north of Adams Luck Creek and the Kandik River and may be the pre­ Peak. The section at the east end of Limestone Hog­ dominant lithology in its largely covered parts in the back (fig. 5) in the W% sec. 31, T. 2 N., R. 33 E. seems area between Hard Luck Creek and Hillard Peak. to be most complete and is designated the type section. More resistant beds of limestone and limestone boulder This section was not examined in detail and may be conglomerate crop out in the lower part of the Adams faulted. On figure 2, column 2, it is shown diagram- matically. near Hillard Peak, in the middle part of the formation The basal beds of the Adams Argillite are light-brown at the east end of Limestone Hogback, and in the upper quartzite. Most of the quartzite is massive, but along part of the formation along the Yukon and Tatonduk the Tatonduk Eiver it is thinly bedded and cross lam­ Rivers. Some of the limestone is quite sandy, and it inated and has interbeds of siltstone and grayish-green grades laterally and vertically into quartzite partly (10#r 5/2) chloritic shale. The quartzite is well- cemented by calcite. Oolitic limestone occurs in the sorted quartz arenite cemented by quartz and (or) car­ lower part of the formation about a mile northeast of bonate. Hillard Peak. All the limestone seems to be lenticular. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A9

Edwin Kirk: Archaeocyathw sp., Ethmophyllum sp., and Dorypyge ? sp. Kirk assigned these fossils a Mid­ dle Cambrian age apparently in the belief that they are associated with Middle Cambrian trilobites at a nearby locality. According to Okulitch and Greggs (1958, p. 622), Etlimophyllum characterizes the middle zone of the Lower Cambrian of the northern Cordil- leran region of North America. Archaeocyathids associated with trilobites were found in limestone thought to be in the upper part of Adams Argillite along the Yukon River (collns. 60ABa222, 60ABa222F, 60ABa222G and 60ABa222GA). The fos­ sils are of Early Cambrian age, according to A. R. Palmer. Tubes about 2 mm in diameter and 5-10 mm in length FIGUEE 5. Cambrian sequence at east end of Limestone Hog­ are common along bedding in quartzite within back. Apparent angular discordance between the Funnel the Adams Argillite. Presumably they are some type Creek Limestone and the Hillard Limestone may be caused of worm burrow. Sandstone in the tubes is finer grained by faulting or flexuring within the intervening Adams Argil- and has more calcite and clay than the surrounding lite. View is west from ridge extending north from Hillard quartzite. Most of the tubes are ovoid in cross section Peak. and straight. An isolated outcrop of greenstone occurs about 50 feet , a fan-shaped of probable Cam­ above the base of the Adams Argillite about l1/^ miles brian age, was found in the Adams Argillite between northeast of Hillard Peak. The greenstone has abun­ Hard Luck Creek and the Kandik River (fig. 1). A dance white calcite amygdules and a somewhat frag- similar Oldhamia in argillaceous rocks was found by mental texture. In thin section, abundant amphibole Mertie (1937) in the Mount Schwatka area, and by phenocrysts can be seen in a felted mass of plagioclase geologists of the BP Exploration Co. (Alaska), Inc., crystals. All the minerals are extensively or wholly in the Crazy Mountains of east-central Alaska. A replaced by calcite, chlorite, and other minerals. The description of these fossils and their stratigraphic sig­ texture and mineralogy of the rock suggest that it may nificance are given in a report by Churkin and Brabb be an altered hornblende andesite. (1965b). Greenstone also occurs in the Adams Argillite about In summary, the presence of archaeocyathids, trilo­ 3 miles northeast of the mouth of the Nation River bites, and Oldhamia, in the formation and a strati- (fig. 1). The stratigraphic position of this greenstone graphic position below a formation containing Early is uncertain, inasmuch as the rocks are extensively Cambrian fossils indicate that the Adams Argillite is folded and faulted. of Early Cambrian age. The Adams Argillite is about 600 feet thick in the The Adams Argillite rests accordantly on the Funnel Hillard Peak area. It seems to be about 300 feet thick Creek Limestone. No reworked limestone suggestive of an was found in the basal quartzite at the east end of Limestone Hogback, but part of the of the Adams Argillite near Hillard Peak and Lime­ formation may be faulted and missing there. Along stone Hogback, but because of the hasty examination the Tatonduk Eiver, it seems to be about 400 feet thick. it could have been overlooked. The chert and limestone Fossils in the Adams Argillite include archaeocya- breccia at the top of the Funnel Creek Limestone along thids, trilobites, worm(?) burrows, and Oldhamia, a the Tatonduk River could consist of reworked material trace fossil. The archaeocyathids occur in a boulder and be more properly included as the basal deposit of conglomerate near the base of the formation in the the Adams Argillite, but it seems to be conformable vicinity of Hillard Peak (see fig. 2, column 1, and with and a part of the Funnel Creek Limestone. p. A23 for locality data), in limestone in the middle part of the formation near Limestone Hogback (J. B. CAMBRIAN, AND ORDOVICIAN ROCKS Mertie, Jr., unpub. data), and in limestone in the upper HILLARD LIMESTONE part of the formation along the Tatonduk Eiver. The A resistant fossiliferous limestone that forms crags last locality is probably the same as 30AW62 (see and escarpments in the Eagle region is a key formation Mertie, 1933, p. 398), from which the following fossils in mapping the structure of the area. It is here named were collected by Aaron Waters and identified by the Hillard Limestone for exposures in the vicinity of A10 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

Hillard Peak, a newly named mountain between Mc- sec. 3, T. 1 N., R. 33 E. The top and a 500-f oot-thick Cann Hill and the Yukon Kiver (fig. 3). Hillard Peak section of the formation ure exposed there, but the base is triangulation station "Chief" on Mertie's (1933, pi. Y) is concealed. A supplementary section (fig. 6) on a map and is BM 4085 on the Eagle D-l quadrangle map cliff about 1.3 miles north-northeast of Hillard Peak (1: 63,360), 1956 edition. The Hillard Limestone ex­ has the top of the Hillard Limestone and a 250-foot- tends westward from Hillard Peak to the Adams Peak thick section exposed. Another section, about one-half area, and it extends northward from Adams Peak in mile east-northeast of Hillard Peak, contains abundant a continuous band to the Tatonduk Eiver and Montauk fossils in the uppermost 75 feet of the formation. The Bluff areas. It has also been mapped by Brabb and three sections are combined in figure 2, column 1. Churkin (1964) in structurally isolated localities near The characteristic lithology of the Hillard Limestone Hard Luck Creek, near the lower part of the Nation in its type area is fine-grained pale-yellowish-brown River, and along the U.S.-Oanada boundary between (\QYR 6/2) limestone in beds from a fraction of an Tindir Creek and the Nation River. The Hillard Lime­ inch to several feet thick. The lenticular character of stone has also been traced on aerial photographs from some of the beds is shown by figure 6. Limestone edge­ its type locality to an area in Canada about 5 miles wise conglomerate is common, and oolitic limestone was southeast of Hillard Peak, beyond which area photo­ found at one locality. Some of the limestone has been graphic coverage was unavailable. replaced by chert and chalcedony, and in some places The type section for the Hillard Limestone is on it has a few interbeds and nodules of laminated pale- cliffsr about 1.6 miles east of Hillard Peak in the NEV4 brown (5YR 5/2) and grayish-black (-A^2) chert.

FIGUEE 6. Upper part of the Hillard Limestone on cliffs 1.3 miles north-northeast of Hillard Peak. Numbers indicate fossil collection localities. Note the lenticular character of the bedding. Rounded hills along top of ridge have outcrops of Ordovician graptolitic shale and chert of the Road River Formation (Ordovician and ). Limestone Hogback in middle background is formed of the Funnel Creek Limestone. View is west toward Yukon River. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS All

The Adams Peak-Yukon River area (fig. 7) has fairly well exposed fossiliferous, easily accessible outcrops of Hillard Limestone, but structural complications make this area less suitable than the Hillard Peak area for a type section. Three partial sections were measured, one along the Yukon River (fig. 7, section 3), another near Adams Peak (fig. 7, section 4), and the third on a ridge southwest of Adams Peak (fig. 7, section 5). The sec­ tion near Adams Peak (fig. 8) is complicated by what seems to be a large slump block on the southwest side of the mountain. The section across a north-trending ridge (fig. 9) and east-trending flatiron about a mile southwest of Adams Peak is complicated by faults(?) and by lateral changes in resistance to of the Hillard Limestone. The top bed of the formation does FIGURE 7. View north across Yukon River towards Adams Peak not strike along the crest of the ridge and flatiron, as showing location of measured sections shown on figure 2, columns 3-5. Low wooded island in foreground obscures the one might expect from a study of aerial photographs or upper part of section 3. from a distant view of the area. Instead, the upper

FIGURE 8. Cambrian rocks just west of Adams Peak. Fossil collections, indicated by numbers on the photograph, are from the Hillard Limestone. Red beds of Adams Argillite are exposed in the lower left foreground. Talus in the vicinity of collection 4351-CO and 4352-CO is mainly chert and shale from the Road River Formation overlying the Hillard Lime­ stone. The block of limestone in the lower center of the photograph is apparently a slump block. View is north. A12 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

the clasts in the conglomerate; this similarity suggests that the clasts are derived from nearly contemporaneous material. The boulder conglomerate seems to grade upward into oolitic limestone, fine-grained and thin-bedded limestone, and limestone edgewise conglomerate. These beds in turn are overlain along the Yukon River by dark (N3) and grayish-black (A"2) organic shale, siltstone, and laminated limestone. Nearly all of these dark beds are concealed or missing along the ridge southwest of Adams Peak, but the uppermost beds crop out at the base of the cliff in the middle part of the ridge. The dark beds do not occur in the section near Adams Peak. The rest (upper part) of the Hillard Limestone in the Adams Peak-Yukon River area is predominantly edgewise conglomerate. This conglomerate (fig. 10)

FIGURE 9. Exposures of the Hillard Limestone on ridge and flatiron about a mile southwest of Adams Peak. Numbers show fossil localities. Red beds of Adams Argillite in the upper right-hand corner of the photograph are the same ones shown on figure 8. View is northwest.

part of the formation (Iocs. 4350-CO, 4349-CO, 3Y14- CO, 3Y1Y-CO, and 3Y18-CO, fig. 9) forms only the southern part of the ridge crest. The middle part of the formation forms, the middle part of the ridge crest (Iocs. 434Y-CO and 4348-CO) and the prominent flatiron (Iocs. 3832-CO and 4332-CO). The lower part of the Hillard Limestone is exposed only along the northern part of the ridge crest (Iocs. 4333-CO, 4334r- CO and 4335-CO). The section along the Yukon Eiver is complicated by a fault between outcrops of Hillard FIGURE 10. Limestone edgewise conglomerate characteristic of Limestone and a limestone apparently within the upper part of the Hillard Limestone along the Yukon River. Adams Argillite. The lowest beds of the Hillard Limestone exposed in consists of small flat pieces of pale-yellowish-brown the Adams Peak-Yukon Kiver area are limestone-boul­ (lOTT? 6/2) fine-grained limestone, moderately to der conglomerate. Some of the boulders are 3 feet in steeply inclined to the bedding. Most of the limestone maximum dimension. The boulders consist of pale-yel­ pieces are less than 6 inches long, and a few are from 6 lowish-brown (10T7? 6/2) oolitic limestone and fine­ to 12 inches long. The pieces are in a matrix of slightly grained limestone in a matrix of sand-size detrital lime­ coarser grained limestone that weathers very pale stone grains. Phosphate, in the form of chips, pellets, orange (10T7? 8/2) in contrast to the medmm-light- and finely disseminated material in the matrix, is com­ gray (N6) color of the weathered clasts. mon in the conglomerate. The chips are grayish black Phosphate similar to that in the basal (?) boulder and are easily mistaken for the chert fragments that also conglomerate was discovered in most of the formic acid occur in the limestone. The pellets are the same color as the limestone, pale yellowish brown (lOTT? 6/2), and residues of samples from the upper part of the Hillard are easily overlooked. Most of the phosphate in the Limestone in the Adams Peak-Yukon River area. The matrix is collophane that may be derived in part from sample richest in phosphate is from the basal part of -shell material and in part from the associ­ the limestone edgewise conglomerate in the central part ated pellets and chips of phosphatic material. of the ridge southwest of Adams Peak, near collection Within the conglomerate are beds of oolitic lime­ 3Y1Y-CO (fig. 9). X-ray analysis by B. M. Madsen of stone and fine-grained limestone similar in lithology to the U.S. Geological Survey indicates that nearly all the STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A13 phosphate from that sample is apatite having about 2 black (517? 2/1) phosphate chips as much as 30 mm percent CO2. Crandallite may also be present in trace long occurs in the middle of the limestone section. amounts. Three beds of grayish-black (N2) chert from 1 to 12 The Hillard Limestone exposed along the Tatonduk inches thick occur near the top of the formation. Kiver is more thinly bedded, has many more interbeds Sedimentary structures are common in the upper 275 of shale and siltstone, and has much less edgewise con­ feet of the Hillard Limestone along the Tatonduk River glomerate than the Hillard in the Adams Peak-Yukon where crossbeds, graded beds, flute casts, and cone-in- River area. Near the base of the formation two boulder cone structures were observed. conglomerate beds are separated by shale; each bed The Hillard Limestone in the area about 4 miles projects into the Tatonduk River and forms ledges that northeast of Mbntauk Bluff was not carefully ex­ are hazards to boats. The basal boulder conglomerate amined, but it appears here to be mainly massive lime­ is shown in figure 11. Most of the limestone strati- stone. Limestone boulder conglomerate occurs in float near the base of the section. The uppermost part of the formation is thinly bedded, very fine grained, pale- yellowish-brown (1017? 6/2) limestone. Along Hard Luck Creek, the Hillard is most similar in gross appearance to its exposures along the Tatonduk River, except that it has more shale. It consists mainly of alternate sets of limestone and shale. Most of the sets are 6 inches to 1 foot thick, and each set contains numerous laminae and (or) graded beds. The lime­ stone sets are more resistant to erosion than the shale interbeds and protrude on weathered surfaces. In summary, the Hillard Limestone is predominantly fine-grained pale-yellowish-brown limestone in beds a fraction of an inch to several feet thick. Limestone edgewise conglomerate is common in the formation, and shale and limestone boulder conglomerate occur FIGUKE 11. View northeast up the Tatonduk River showing locally. ledge of boulder conglomerate at the base of the Hillard Lime­ Near Adams Peak (fig. 2, column 4), Hillard Peak stone (left foreground) and exposures of the Adams Argillite (fig. 2, column 1) and Limestone Hogback (fig. 2, and Funnel Creek Limestone on the north valley slope. The column 2), well-bedded Hillard Limestone is directly beds dip toward the lower left-hand corner of the photograph. overlain by well-bedded chert of the Road River Formation of Ordovician and Silurian age. Along the graphically above the conglomerate contains some chert Tatonduk River (fig. 2, column 6), the ridge 1 mile and quartz sand and grit grains, and a few sandy lime­ southwest of Adams Peak (fig. 2, column 5), and Hard stone beds grade into limy sandstone. Thin sections Luck Creek (fig. 2, column 8), however, the basal or indicate that most of the carbonate in the sandy lime­ lower beds of the Road River Formation are a breccia stone is clastic and that the rock is calcarenite. A few consisting of angular and rounded pebble- to boulder- thin graded limestone beds consists mostly of echino- size clasts of limestone, shale, dolomite, and black chert, derm fragments. all cemented by calcite. The breccia is overlain by Pyrite is common in nearly all of the rocks. Most graptolite-bearing chert and shale more characteristic of it is finely disseminated but some occurs in veinlike of the Road River. In all localities, the change from structures. In one thin section of a limestone, pyrite the Hillard Limestone to chert, shale, and breccia of the occurs around the rim of what appear to be recrystal- lized oolites. Road River Formation is abrupt. Some of the Hillard Limestone along the Tatonduk Faults and incomplete exposures make it difficult to River is dolomitic and weathers grayish orange (1017? determine the exact thickness of Hillard Limestone, but 7/4). On the other hand, some of the limestone con­ the formation seems to reach a maximum thickness of tains so much organic material that it is grayish black about 500 feet in the Hillard Peak area. The Hillard (N2) . A bituminous substance that dissolves in carbon Limestone is about 400 feet thick along the Tatonduk disulfide and colors it black occurs in fractures in this River, about 200 feet thick in the vicinity of Adams limestone. Most of the limestone contains phosphatic Peak and Montauk Bluff, and about 100 feet thick along material; one 2-inch bed consisting mainly of brownish- Hard Luck Creek. 232-493 O -66 3 A14 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

Fossils are fairly common in the Hillard Limestone faunas are all the same age, according to Palmer, the (see fig. 2 for position of fossil collections in the sections boulders at that locality were apparently derived from measured). Fossils collected from beds a few inches the reworking of nearly contemporaneous material. apart and put in the same collection, however, may be­ Fossils of early Middle Cambrian age, according to come a mixed representing different stages, series, Palmer, were collected (4341-CO) from bedded lime­ or systems. Such difficulties evidently led Kirk (see stone about 40 feet above the base of the exposed section Mertie, 1933, p. 398) to conclude erronously that of the Hillard Limestone in the vicinity of Hillard Peak archaeocyathids in the Adams Peak area must be Mid­ (fig. 2, column 1). Similar faunas were obtained from dle Cambrian because they are associated with Middle 10 to 20 feet above the basal (?) boulder conglomerate Cambrian trilobites. Still another difficulty in col­ in the Yukon River-Adams Peak area (4330-CO, 4348- lecting fossils and determining their stratigraphic posi­ CO), from the lowest exposures of the formation north­ tion in this formation is that incomplete exposures east of Montauk Bluff (4346-CO), and from limestone make it difficult to locate the top and bottom of the interbedded with boulder conglomerate in the lower formation. The problem in locating the top of the part of the formation along the Tatonduk River (4303- Hillard Limestone along the ridge and flatiron south­ CO, 4339-CO, and 4340-CO). Fossils of younger Mid­ west of Adams Peak has already been mentioned. It is dle Cambrian age were collected from 400 (4345-CO) also difficult to locate the base of the formation in the to 430 (4344-CO) feet below the top of the Hillard Hillard Peak area because the break in slope from cliff Limestone in the Hillard Peak area, and about 100 feet exposures to rounded hills does not exactly mark the below the top of the formation, near Adams Peak contact between the Hillard Limestone and underlying (4337-CO), along the ridge and flatiron southwest of Adams Argillite, as one would expect. Some of the Adams Peak (4347-CO and 3832-CO), and along the rounded hills are vegetation-covered talus piles that Tatonduk River (4310-CO). conceal different parts of the Hillard Limestone at dif­ Fossils of early Late Cambrian () age, ferent localities. according to Palmer, were collected about 250 feet below In spite of these difficulties, the faunal succession the top of the Hillard Limestone in the Hillard Peak within the Hillard Limestone is thought to be reason­ area (4360-CO) and from 70 to 100 feet below the top ably well established. A. R. Palmer (written commun., of the formation along the ridge southwest of Adams 1965) furnished the information for the following brief Peak (3717-CO and 3718-CO), along the Tatonduk discussion. River (4326-CO), and along Hard Luck Creek (4376- The oldest fossil, an archaeocyathid of Early Cam­ CO). Fossils of middle Late Cambrian () brian age, was observed by Palmer in what appeared age were collected from 1 to 200 feet below the top of to be the matrix of boulder conglomerate in the lower the Hillard near Hillard Peak (4359-CO, 4358-CO, (basal ?) part of the Hillard Limestone along the Yukon 4357-CO, 4356-CO, 4355-CO, and 3709-CO), about 30 River. The specimen could not be collected. Arch­ feet below the top of the formation near Limestone Hog­ aeocyathids were also observed by Palmer in boulders back (3710-CO), a^nd about 10 feet below the apparent within limestone boulder conglomerate float near the top of the formation near Montauk Bluff 4379-CO). base (?) of the Hillard Limestone northeast of Montauk Fossils of late Late Cambrian (Trempeleauan) age, Bluff and were collected (4338-CO) from boulders in according to Palmer, were collected from 1 to 30 feet the lower (basal?) part of the formation near Adams below the top of the Hillard Limestone near Adams Peak. The archaeocyathids in these boulders are ob­ viously reworked, but whether the reworked boulders Peak (4351-CO, 4352-CO). Collections 4349-CO and are virtually contemporaneous or considerably older 3714-CO from the ridge southwest of Adams Peak may could not be determined. Trilobites of Early Cambrian be the same age. A fauna of early Early Ordovician age (colln. 4302-CO) were obtained from a boulder in age was collected (4353-CO) from the uppermost beds the basal bed of the Hillard Limestone along the Taton- of the Hillard Limestone about 800 feet above the duk River. Tatonduk River on its north valley slope (fig. 4). This Three collections of trilobites and other fossils of collection is not shown on figure 2 because the beds slightly younger Early Cambrian age were obtained appear to be faulted out at river level where the section from the uppermost part of the boulder conglomerate was measured. along the ridge southwest of Adams Peak. Two col­ In summary, fossils indicate that the Hillard Lime­ lections (4333-CO and 4334-CO) are from limestone in- stone ranges in age from Early Cambrian to Early terbedded with the boulder conglomerate, and 4335-CO Ordovician. At all but one locality the formation is is from one of the limestone boulders. Inasmuch as the not younger than Late Cambrian. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A15

The Eoad Eiver Formation, which unconformably member is predominantly fine-grained limestone, where­ overlies the Hillard Limestone, ranges in age from mid­ as the upper member is predominantly medium- to dle or late Early Ordovician (Arenigian or Llanvir- coarse-grained bioclastic limestone. The lateral con­ nian) to Late Silurian (Ludlovian), according to Chur- tinuity of these members is not as yet well established. kin and Brabb (1965a, fig. 3). The Eoad Eiver For­ mation evidently rests on beds of the Hillard Limestone LOWER MEMBER possibly as old as early Late Cambrian (Dresbachian) The lower 2,000 feet of the lower member consists along Hard Luck Creek, and middle Late Cambrian primarily of very light gray (NS) massive limestone (Franconian) near Hillard Peak, Limestone Hogback, and dolomite. Some of the limestone is oolitic and piso- and Montauk Bluff. The indicated stratigraphic hiatus litic. The irregular distribution of the dolomite sug­ is as much as four or five stages (part of the Dresbach­ gests that it is secondary and that the rock was origin­ ian, all the Franconian, Trempeleauan, and Tremado- ally entire limestone. The rock is extensively silicified, cian, and most or all of the Arenigian) along Hard particularly in the basal 500 feet of the member. Luck Creek, and as little as one or two stages (parts of The limestone and dolomite grade upward into ap­ the Tremadocian and Arenigian or Llanvirnian) along proximately 940 feet of light-olive-gray (5Z 6/1) and the Tatonduk Eiver. pale-yellowish-brown (\$YR 6/2) very fine grained, thin- to thick-bedded limestone. Some of the limestone JONES RIDGE LIMESTONE is silicified and some is oolitic. No other lithologic vari­ A previously unnamed limestone formation is exposed ations were noted along the measured section, but a thin in magnificient and spectacular cliffs and jagged peaks bed of sandy limestone containing glauconite and (or) in the horseshoe-shaped series of ridges and peaks from chlorite was found near the base of this interval along Jones Eidge to triangulation station Hi-yu (BM 4839) the upper part of Hard Luck Creek. and to Squaw Mountain. This formation was mapped The lower member of the Jones Eidge Limestone is as an undifferentiated limestone of Cambrian to De­ about 2,940 feet thick. vonian age by Cairnes (1914b), and it furnished most No fossils were found in the lower 2,300 feet of the of his Upper Cambrian fossil collections (see p. A29). lower member of the Jones Eidge Limestone at its type Mertie (1933) supplemented the collections of Cairnes section, but these rocks were not extensively examined. and found new faunas of Early and Middle Ordovician Archaeocyathids were collected (4301-CO) about 500 and "Middle" (now considered Early) Cambrian age in feet above the base of the member about 3 miles south­ this limestone. On his geologic map, Mertie dif­ west of Jones Eidge (fig. 12) and about 3,500 feet north­ ferentiated this limestone from all the other formations west of triangulation station Hi-yu. Additional speci­ of Cambrian and Ordovician age in the Eagle region. mens of excellently preserved archaeocyathids were The formation is here named the Jones Eidge Lime­ collected (4301-CO) about 2,000 feet south of Hi-yu. stone for exposures in the vicinity of Jones Eidge. Waters (in Mertie, 1933, p. 398, colln. 30AW58-59) The Jones Eidge Limestone seems to be limited in found archaeocythids about 3,000 feet west of Hi-yu, areal extent to the Jones Eidge-Hi-yu-Squaw Moun­ but the stratigraphic position of these collections is un­ tain area and to a small adjoining area in Canada. certain because the rocks are faulted. The type section of the Jones Eidge Limestone (fig. 2, At the type section of the Jones Eidge Limestone, the column 9) is designated as the central part of sec. 3, T. lowest fossils (4361-CO) from the lower member are 3 N"., E. 33 E., where the base of the formation is ex­ of early Late Cambrian (Dresbachian) age, according posed, then across the crest of Jones Eidge to the north­ to A. E. Palmer. Fossils 43T4-CO and 43T1-CO, of western part of section 10, at an altitude of about 3,300 late Late Cambrian (Trempeleauan) age, according to feet. The top of the formation is at the base of a 60- Palmer, were found from 2,630 to 2,7*0 feet above the foot largely covered interval, which presumably con­ base of the member. The highest collections (4367-CO, tains shale, chert, and limestone. The type section of 4368-CO, and 4369-CO) from the lower member are the Jones Eidge Limestone is completely exposed, ac­ of Early Ordovician age, according to E. J. Eoss, Jr. cessible, and quite fossiliferous, at least in its upper In summary, the lower member of the Jones Eidge part. The section from collection 4361-CO to 4365-CO Limestone may range in age from Early Cambrian to was measured by tape, and I estimated the thickness of Early Ordovician. No fossils of Middle Cambrian and the section from 4361-CO to the base of the formation. middle Late Cambrian (Franconian) age were found, The Jones Eidge Limestone is provisionally and in­ but the part of the section where the fossils would occur formally subdivided into two members. The lower has not been carefully examined. A16 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA The lower member rests accordantly and probably did not recognize unit A in the Jones Ridge-Squaw conformably on a 300-foot-thick formation consisting of Mountain area, but outcrops of the formation there are grayish-black "platy" limestone, carbonaceous shale, small and discontinuous and easily overlooked. and quartz-rich sandstone and siltstone. This forma­ Fossils and stratigraphic sequence (fig. 13) indicate tion is most similar in lithology to Mertie's (1933) that the lower member of the Jones Ridge Limestone is unit A of the Tindir Group which he described but did correlative with the Funnel Creek Limestone, Adams not map in the vicinity of the Tatonduk River. Mertie Argillite, and Hillard Limestone.

FIGURE 12. Contact between unit A of the Tindir Group and the lower member of the Jones Ridge Limestone about 0.8 mile northwest of triangulation station Hi-yu. Archaeocyathids were collected at locality 4301-CO. View is east. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A17 s< Area from Hillard Peak Area from Jones Ridge £% SERIES £

Unnamed chert, shale, Ashgillian and limestone Upper

Lower part of Upper member ORDOVICIAN Caradocian Road River Formation Middle

Llandeilan

Llanvirnian

Lower Arenigian

Tremadocian r~^ r-s Upper Franconian JonesRidgeLimestone

Dresbachian

Middle Hillard Limestone CAMBRIAN Lower member

Adams Argillite

Lower

Funnel Creek Limestone

PRECAMBRIAN Tindir Group- unit A of Mertie (1933)

FIGUEE 13. Stratigraphic columns of lower Paleozoic formations of east-central Alaska and their correlation. A18 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

TIPPER MEMBER Collection 4366-CO: The upper member consists chiefly of about 60 feet Illaenusl sp. Asaphid pygidium of pale-yellowish-brown (WYR 6/2) medium- to Streptelasmatoid coarse-grained, thickly bedded bioclastic limestone. A Ostracodes, undet. representative view of the upper member and the upper Eoss believes that these faunas are probably of late part of the lower member is shown on figure 14. Some Middle or early Late Ordovician (Caradocian) age and are possibly as young as late Late Ordovician (Ashgil- lian). W. A. Oliver, Jr., examined the coral from 4366-CO and determined that it is not older than Middle Ordovician. Ostracodes from 4364-CO and 4365-CO were examined by J. M. Berdan, who identi­ fied the following :

Collection 4364-CO: Eurychilina'i sp. Acronotellal sp. Steusloffina sp. cf. S. ulrichi Teichert Smooth ostracodes, undet. Collection 4365-CO: Aparchitesl sp. HesperideHa"} sp. Platybolbinal sp. Eohollina, sp. Steusloffina sp. cf. S. ulrichi Teichert Smooth ostracodes, undet. These fossils, according to Berdan, are either of Middle FIGUEE 14. Upper part of Jones Ridge Limestone on south slope or Late Ordovician age. of Jones Ridge. Rounded bare slopes in middle background R. J. Ross, Jr., collected a fauna (D1072-CO) similar have exposures of McCann Hill Chert of Middle and Late Devonian age. View is south. to that in collections 4364-CO, 4365-CO, and 4366-CO from limestone and chert about 1 mile west and along the strike from the Jones Ridge section (fig. 3). Pre­ very fine grained limestone similar to that characteristic sumably it is from the upper member of Jones Ridge of the lower member is interbedded with the coarser Limestone. The following fossils in the collection were grained limestone. Most of the coarser grained lime­ identified by Ross and Dutro (1966) : stone consists of probable pelmatozoan fragments and lesser amounts of and brachiopod fragments. Collection D1072-CO: The following fossils from the upper member were Ptychopleurella cf. P. lapworthi (Davidson) identified by E. J. Boss, Jr.: jonesridgensis Ross and Dutro Camerellal sp. Collection 4364-CO: Rhyncliotrema^ sp. Diambonia sp. Cyclospira cf. C. glansfagea Cooper and Kindle Cyclospira sp. Cyclospira^ sp. Ptychoglyptus sp. Catazyga homeospiroides Ross and Dutro Sowerbyellid? brachiopod WMtfteldella^ sp. Xenambonitesl sp. Anoptambonites cf. A. grayae (Davidson) Paraharpes? sp. Diambonia, cf. D. anatoli Spjeldnaes Remopletvrides sp. Diambonia, sp. 1 ! sp. Diambonia sp. 2 Ostracodes Xenambonites cf. X. revelatus Williams Collection 4365^CO: Ptychoglyptus ? cf. P.? pauciradiatus Reed Cyclospira sp. sp. Catazygal sp. Diamboniat sp. Ross believes that this collection, like 4364-CO, Soioerbyella? sp. 4365-CO, and 4366-CO, is probably of early Late Ordo­ Ptychopleurellal sp. vician (Caradocian) age and possibly as young as late Dalmanellid? brachiopod Late Ordovician (Ashgillian). Dutro believes, how­ Odontopleurid trilobite Illaenid trilobite ever, that this collection is late Late Ordovician Abundant ostracodes (Ashgillian). STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A19

In summary, fossils indicate that the upper member PALEOTECTONIC IMPLICATIONS of the Jones Ridge Limestone is either of Middle or The Jones Ridge Limestone is nearly surrounded Late Ordovician age. laterally by contemporaneous rocks of different lithol­ The fossil evidence suggests that part of the Lower ogy. A facies map by Douglas and others (1963, fig. 4) and part or all of the Middle Ordovician are missing indicates that in Canada from 80 to 250 miles east and at the contact between the lower and upper members. northeast of Jones Ridge contemporanous rocks are No other evidence for an unconformity was observed. predominantly siltstone, sandstone red beds, salt, and Inasmuch as the members seem to be accordant, the anhydrite. Contemporaneous rocks northwest, west, indicated break is evidently a disconformity. southwest, and south of Jones Ridge include clastic The tentative correlation of the upper member is rocks of the Adams Argillite, shale and chert of the shown on figure 13. The upper member is correlative Road River Formation, and limestone containing with the lower part of the Road River Formation of boulder and edgewise conglomerate. The only nearby Ordovician and Silurian age. area that seems to have carbonate sequences equivalent In summary, the Jones Ridge Limestone is of Cam­ to the Jones Ridge Limestone is in Canada from 30 to brian to Middle or Late Ordovician age. There seems 200 miles east-southeast of Jones Ridge (Green and Rod- to be at least one disconformity within the formation. dick, 1962), but the age of the Cambrian and Ordo­ UNNAMED CHERT, SHALE, AND LIMESTONE vician rocks in that area is not yet well established, so it is not possible to determine if the rocks are coeval. Approximately 30 feet of section stratigraphically Large-scale thrust faulting is one explanation for the above the top of the Jones Ridge Limestone at the type "island" of Cambrian and Ordovician limestone in the locality is covered. Float in this 30-foot interval is Jones Ridge-Squaw Mountain area. The rocks are predominantly grayish-black chert and shale. A 5-f oot- structurally isolated by major faults from those in the thick bioclastic limestone, similar in lithology to Hillard Peak-Hard Luck Creek area (fig. 3), and a limestone of the upper member of the Jones Ridge tectonic map of northern Canade by Douglas and others Limestone, crops out about 30 feet above the top of the (1963, fig. 2) indicates that what appears to be the member. About 25 feet of section above this 5-foot- eastern boundary of rocks in the Jones Ridge-Squaw thick limestone is covered, but chert and shale were Mountain area is a thrust fault dipping beneath the found in float in this interval. The base of a 300-foot- "island." The Jones Ridge Limestone and adjoining thick limestone, referred to by Churkin and Brabb formations, therefore, may be entirely allochthonous. (1965a) as the basal limestone member of the McCann A structural explanation for the "island" of carbonate Hill Chert of Middle and Late Devonian age, crops out rock does not, however, appear to be warranted. The 60 feet above the top of the upper member of the Jones faults separating the Jones Ridge Limestone from the Ridge Limestone. Hillard Limestone, Adams Argillite, Funnel Creek from the 5-foot-thick limestone 30 feet above the top of the upper member of the Jones Ridge Lime­ Limestone, and other formations seem to be high-angle stone were identified by W. A. Oliver, Jr.: faults rather than low-angle thrusts. A few formations, such as the McCann Hill Chert and unit A of the Tindir Collection 4387-CO Calapoecia sp. Group, occur in both the "allochthonous" and "autoch­ Manipord sp. thonous" blocks. GrewngJcia sp. Horn corals, undet. FACIES AND THEIR ECOLOGICAL IMPLICATIONS These corals are of Late Ordovician age, according to Rapid lateral changes in lithology seem to explain Oliver. They indicate that at least part of the 60-foot adequately the "island" of carbonate rock in the Jones largely covered interval between the top of the Jones Ridge-Squaw Mountain area. The facies and their Ridge Limestone and the basal limestone member of ecological implications are discussed in chronological the McCann Hill Chert is correlative with part of the order, from Early Cambrian to Middle or Late Road River Formation of Ordovician and Silurian age. Ordovician. If the chert and shale found in float in the 60-foot largely covered interval are more representative of the EARLY CAMBRIAN lithology than the 5-foot-thick limestone bed that crops out and if this chert and shale represent a mappable During the desposition of the Funnel Creek Limestone formation, then the Road River Formation can be ex­ and the lower part of the lower member of the Jones tended to include these beds in the Jones Ridge-Squaw Ridge Limestone in early Early Cambrian time (fig. Mountain area. 15A), the area from the Tatonduk River to the Nation A20 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

141

Quiet and shallow ;:/marine.shelf marine shelf ir^r^r O7 " 7 "Si *"" River ~ rr r~. T EXPLANATION rn~p Lenticular limestone

Bedded limestone

Shale and argillite

Sandstone, siltstone, and quartzite

I \1 I 1 I

I I I T\ I sfRiverver I I,T I,n nI, iI, l>r\ I T

I I I II I I I I I I I I I

T.E^^K ---TE-- y _ _ __ ' ^1 T I A|

FIGURE 15. Lithofacies maps of the Hillard Peak-Nation River area from Early to Late Cambrian. A, early Early Cambrian; B, middle and late Early Cambrian; C, Middle Cambrian; D, early Late Cambrian (Dresbachian). A, arebaeocyathids; E, edgewise conglomerate; G, greenstone; O, oolites; P, pisolites; R, red 'beds; S, secondary silica; T, trilobites and other fossils; W, wonn(?) borings; X, crossbeds; *, Oldhamia localities. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A21

River appears to have been a relatively quiet shallow lithology of the lower part of the Hillard Limestone marine shelf, as indicated by the uniform lithology and and the middle part of the lower member of the Jones laminated character of the rocks and by archaeocyathids Ridge Limestone (fig. 160). Edgewise and boulder which, according to Okulitch (1955, p. E2), indicate conglomerates and oolitic limestone indicate inter­ shallow clear seas. If limestone was the dominant de­ mittent turbulent conditions in the western and south­ posit throughout the area, then most of it in the northern ern part of the area. Limestone and shale were de­ part and some in the southern, part was dolomitized. posited locally in the Tatonduk River area and along The prevalence of irregularly shaped siliceous veins and the Yukon River south of Adams Peak. The abundant vugs in the limestone and dolomite suggests that dolo- organic material and pyrite in both the shale and mitization, if it did occur, was accompanied by silicifica- associated limestone suggest that reducing conditions tion. Pisolites and oolites and, more locally, edgewise prevailed in these area. conglomerate in the rocks are suggestive of periods of high-energy deposition, but these conditions were not LATE CAMBRIAN AND EARLY ORDOVICIAN predominant. The limestone and dolomite are thickest in the area Conditions during the deposition of the middle and south of the Tatonduk River and thinnest northwest of upper part of the Hillard Limestone and the lower the Nation River, but fossil control is not sufficient to member of the Jones Ridge Limestone during the early show that deposition was more rapid in the former Late Cambrian (fig. 15Z>), middle Late Cambrian (fig. area. 16J.), late Late Cambrian (fig. 165), and early Ordovi- Conditions changed radically in middle and late cian (fig. IG^) were somewhat similar to those during Early Cambrian time (fig. 15B) during deposition of the Middle Cambrian. Limestone was the predomi­ the Adams Argillite and the middle part of the lower nant deposit. Considerable shale was deposited in the member of the Jones Ridge Limestone, except in the Tatonduk River and Hard Luck Creek areas and near Jones Ridge-Squaw Mountain area where deposition of the Yukon River south of Adams Peak. Edgewise con­ limestone continued in shallow clear water. Sand, silt, and clay were washed into the rest of the area from un­ glomerate, suggestive of turbulent conditions, was de­ known sources. Red beds, cross laminations, worm (?) posited in the western and southern part of the area. burrows, oolites, trilobites, and other fossils collectively The conglomerate could have been derived from the indicate that the water was marine, well oxygenated, contemporaneous erosion of a shoal or reef in the east­ shallow, and turbulent. ern part of the area, near Jones Ridge. The paucity of terrigenous material in the lower During the Early Ordovician, deposition of limestone member of the Jones Ridge Limestone and the limited was interrupted and the area was differentially uplifted and somewhat circular areal extent of this limestone and eroded. The Hard Luck Creek area was evidently suggest that there may have been a reef in the Jones uplifted the most, the Hillard Peak area somewhat less, Ridge-Squaw Mountain area during the Early Cam­ and the Tatonduk River to Jones Ridge area the least; brian. No skeletal framework suggestive of reef these uplifts suggest that fold axes during the Early structure was found, however. Perhaps the term lime­ Ordovician were oriented approximately northeast- stone shoal is more appropriate. southwest. Some of the sandy, oolitic, and conglomeratic lime­ Deposition resumed in latest Arenigian or earliest stone in the Adams Argillite may have been reworked Llanvirnian time (Early Ordovician) in the Hillard from the limestone shoal in the Jones Ridge-Squaw Mountain area, and some may have been precipitated on Peak to Hard Luck Creek area (Churkiii and Brabb, local shoals. 1965a). The basal deposits of the Road River Forma­ The extrusive character of greenstone in the Adams tion are chert, chert grit, and a chert and limestone Argillite has not been proved, but volcanism could have breccia, and the succeeding deposits are chert and shale occurred during the Early Cambrian. The chlorite containing graptolites and other fossils. The Jones and iron in the sediments could have been derived from Ridge-Squaw Mountain area was either being eroded the greenstone. during this time or was not receiving sediments. The occurrence of limestone boulders well above the base of MIDDLE CAMBRIAN the Road River Formation (Churkin and Brabb, 1965a, A return to predominantly carbonate deposition oc­ fig. 4, column 3) suggests that the area was being curred during the Middle Cambrian, as reflected by the eroded. A22 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA 141°

65° -

FIGURE 16. Lithofacies maps of the Hillard Peak-Nation River area from Late Cambrian to Middle or Late Ordovician time. A, middle Late Cambrian (Franconian) ; B, late Late Cambrian (Trempeleauan) ; C, Early Ordovician (Tremadocian) ; D, Middle or Late Ordovician (Caradocian or Ashgillian) ; E, edgewise con­ glomerate; G, graptolites and other fossils; T, trilobites and other fossils. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A23

MIDDLE OB LATE ORDOVICIAN Hillard Peak area [Eagle D-l quadrangle (1:63,360), 1956 edition. Easily accessible by helicopter. Can also be reached by foot from Yukon Elver. Best route is from north end of Deposition did not resume in the Jones Ridge-Squaw Pickerel Slough to Limestone Hogback to Hillard Peak (BM 4085)] Mountain area until Middle or Late Ordovician Geological Survey Field locality Collector, of collection; description (Caradocian or Ashgillian) time (fig. 16Z>) when the collection of locality; stratigraphic assignment; age bioclastic limestone of the upper member of the Jones 3709-CO____ 61ABal383___- E. E. Brabb, 1961; 64°57.4' N., 141°02.4' W.; 1-5 ft Ridge Limestone was deposited. As in the limestone below top of Hillard of the Lower Cambrian, no skeletal framework sug­ Limestone; Late Cambrian (Franconian). gestive of reef structure was found, but the limited and 37ll-CO__-_ 61AMc74. J. C. Melik, 1961; 64°56.3' somewhat circular extent of this limestone, its prolific N., 141°00' W.; 1-30 ft below top of Hillard fauna, and the paucity of terrestrial material in the Limestone; Late Cambrian. limestone suggest that the Jones Ridge-Squaw Moun­ 3712-CO____ 61AMc51 _ J. C. Melik, 1961; 64°57.5' N., 141°02.3' W.; about 40 tain area was the site of a shoal or reef during the Mid­ ft below top of Hillard dle or Late Ordovician. Limestone; Late Cambrian. 3713-CO.___ 6lABal341__. E. E. Brabb, 1961: 64°58.3' N., 141°02.2' W.; Hillard SUMMARY Limestone; Late Cambrian. 4341-CO__._ 63ABa3294B. A. R. Palmer and E. E. Four new formations of Early Cambrian to Middle Brabb, 1963; 64°56.9' N., Ordovician age have been mapped in the Eagle region. 141°00.3' W.; about 40 ft above lowest exposure of Three of the formations, the Funnel Creek Limestone Hillard Limestone and and Adams Argillite of Early Cambrian age and the about 460 ft below top of Hillard Limestone; Middle Hillard Limestone of Early Cambrian to Early Ordovi­ Cambrian. cian age, are thought to have been deposited in a pre­ 4344-CO_ _ . _ 63ABa3294C. . _ A. R. Palmer and E. E. Brabb, 1963; about 30 ft dominantly turbulent marine basin, and the fourth, the above 63ABa3294B, in a Jones Ridge Limestone of Early Cambrian to Middle or laminated limestone marker bed in Hillard limestone; Late Ordovician age, is thought to have been deposited Middle Cambrian. on a shoal or reef. 4345-CO _ _ _ _ 63ABa3294D _ _ A. R. Palmer and E. E. Brabb, 1963; about 30 ft The rapid changes in f acies, the possibility of reef like above 63ABa3294C and sedimentation, and the occurrence of bitumen and other about 400 ft below top of Hillard Limestone, in edge­ organic matter in the rocks make the lower Paleozoic wise conglomerate; Middle sequence attractive for petroleum exploration. Large Cambrian. 4355-CO____ 61ABal383A___ A. R. Palmer and E. E. anticlines nearby (Brabb and Churkin, 1964) could Brabb, 1963; 64°57.4' N., contain these sequences at moderate depth, capped by 141°02.4' W.; about 45 ft below top of Hillard Lime­ relatively impermeable rocks. Inasmuch as none of stone, in platy, cherty these structural features have been tested, their petro­ limestone; Late Cambrian (Franconian). leum potential is unknown. 4356-CO____ 61ABal383B.__ A. R. Palmer and E. E. Brabb, 1963; about 20 ft LOWER PALEOZOIC FOSSIL COLLECTIONS FROM below 61ABal383A, in laty, cherty limestone; EAST-CENTRAL ALASKA Eate Cambrian (Franconian). Known Cambrian and Lower Ordovician fossil col­ 4357-CO- _ _ _ 63ABa3281A___ A. R. Palmer and E. E. lections from east-central Alaska are listed below, Brabb, 1963; 64°58.3' N., 141°02.2' W.; about 100 ft. except those collected by L. D. Burling in 1913. Precise below apparent top of coordinates for collections listed in previously pub­ Hillard Limestone, in lished reports are given here for the first time. Collec­ laminated limestone; Late Cambrian (Franconian). tions in the Eagle D-l quadrangle and adjoining area 4358-CO. 63ABa3281B_- A. R. Palmer and E. E. in Canada are shown on a map by Brabb and Churkin Brabb, 1963; limestone float about 50 ft below (1965). Age determinations are by A. R. Palmer, un­ 63ABa3281A; Late less otherwise noted. Cambrian. A24 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

Hillard Peak area Continued Yukon River area Continued Geological Survey Field locality Collector, year of collection; description Geological Survey Field locality Collector, year of collection; description collection of locality; stratigraphic assignment; age collection of locality; stratigraphic assignment; age 4359-CO____ 63ABa3281C___ A. R. Palmer and E. E. 4298-CO.____ 60ABa222F,___ Michael Churkin, Jr., and Brabb, 1963; about 50 ft E. E. Brabb, 1963; same below 63ABa3281B and locality as 60ABa222 but about 200 ft below top of about 100 ft above river; Hillard Limestone, in apparently the same bed coarse-grained limestone as 60ABa222, but possibly lenses; Late Cambrian as much as 20 ft strati- (Franconian). graphically below, in 4360-CO____ 63ABa3281D__ A. R. Palmer and E. E. limestone edgewise Brabb, 1963; about 50 ft conglomerate; Early below 63ABa3281C, 250 ft Cambrian. below top of Hillard lime­ 4298-CO.____ 60ABa222G_ E. E. Brabb, 1963; same stone, and at lowest locality as 60ABa222F, exposures of Hillard Lime­ about 5 ft above stone; Late Cambrian 60ABa222F, in richly (Dresbachian). fossiliferous limestone; 4641-CO__._ 61ABal322__._ E. E. Brabb, 1961; 64°58.2' Early Cambrian. N., 141°01.7' W.; sandy 4296-CO.____ 60ABa222GA__ Michael Churkin, Jr., and limestone about 100 ft A. R. Palmer, 1963; near above base of Adams 60ABa222, in boulder Argillite; Early Cambrian. float that probably came 28AMt262. P. S. Smith, 1928; 64°55.8' from 60ABa222G; Early N., 141°01.1' W.; Hillard Cambrian. Limestone; Late Cambrian Not collected. 60ABa222H _ _ _ A. R. Palmer, 1963; 64°57.4' according to Edwin Kirk N., 141°11' W.; resistant (in Mertie, 1933, p. 400). oolitic limestone boulder ______XXj32______D. D. Cairnes or a member conglomerate knob on of his party, 1912; about north bank of Yukon River, 64°56.9' N., 141°00.3' W.; Hillard Limestone, about Hillard Limestone; Late 25 ft below top of oolitic Cambrian, according to limestone and limestone L. D. Burling (in Cairnes boulder conglomerate unit; 1914a, p. 64). trilobites and Limestone Hogback area observed in boulders; archaeocyathid observed in [Eagle D-l quadrangle. For accessibility, see Hillard Peak area] what appeared to be 3710-CO___ 61ABal396.___ E. E. Brabb, 1961; 64°57.4' oolitic limestone matrix; N., 141°05. 4' W.; about 30 Early Cambrian. ft below top of Hillard 4330-CO____ 60ABa222J____ A. R. Palmer, 1963; about 50 Limestone; Late Cambrian. ft downstream from Kirk No. 30AMt77_ J. B. Mertie, Jr., 1930; 60ABa222H, about 5 ft 2535 64°57.5' N., 141°07.35'W.; below top of oolitic lime­ in saddle; limestone in stone unit within Hillard middle part of Adams Limestone; Middle Cam­ Argillite; Early Cambrian. brian. Not collected. 63ABa3151B_ E. E. Brabb, 1963; about 25 Yukon River area ft above 60ABa222J, in [Eagle D-l quadrangle. Not easily accessible by helicopter. Can be reached from dark-gray laminated lime­ heliport near Adams Peak. Easily accessible by boat] stone and shale unit within 4295-CO_____ 60ABa222. E. E. Brabb, 1960; 64°57.5' Hillard Limestone; Cam­ N., 141°10.8' W.; north brian^). bank of Yukon River at base of resistant limestone Adams Peak area boulder conglomerate rib, [Eagle D-l quadrangle. Heliport at top of limessone slump(?) block, about 2,000 ft probably a limestone bed south of Adams Peak (BM 2814). Can also be reached by foot from Yukon River] within Adams Argillite but 477-CO_____ 38AMt29______J. B. Mertie, Jr., 1938; about possibly Hillard Lime­ 64°58' N., 141°11' W.; stone; Early Cambrian. altitude about 2,635 ft, in Locality recollected in 1963 fine-grained limestone; by A. R. Palmer and Hillard Limestone; Late E. E. Brabb. Cambrian. 28AMt263. J. B. Mertie, Jr., 1928; 478-CO _____ 38AMt30_ J. B. Mertie, Jr., 1938; about probably the same locality 64°58' N., 141°11' W., as 60ABa222; Middle altitude about 2,515 ft, in Cambrian, according to limestone (edgewise?) con­ Edwin Kirk (in Mertie, glomerate; Hillard Lime­ 1933, p. 398) but contains stone; Middle or Late archaeocyathids that may Cambrian. be Early Cambrian. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A25

Adams Peak area Continued Ridge and flatiron southwest of Adams Peak Continued Geological Survey Field locality Collector, year of collection; description Geological Survey Field locality Collector, year of collection; description collection of locality; stratigraphic assignment; age collection of locality; stratigraphic assignment; age 4424-CO 25AMtl48___ J. B. Mertie, Jr., 1925; abou* 3718-CO____ 61AMc941A___ J. C. Melik, 1961; about 100 = Kirk 64°58.2' N., 141°11.1' W.; ft north and uphill from No. 2062 altitude about 2,200 ft, 61AMc941, and evidently = USNM limestone (edgewise?) con­ a few feet stratigraphically 22B glomerate float in talus lower; fine-grained mottled pile, possibly a composite gray limestone lens; Hil­ collection, probably Hil- lard Limestone; Middle lard Limestone; Middle Cambrian. Cambrian. 3832-CO____ 62ABa2801___. E. E. Brabb, 1962; 64°57.6' Kirk No. 30AW13. A. E. Waters, Jr., 1930; same N., 141°11.7' W.; in cen­ 2537 talus pile as 25AMU48, tral part of flatiron, upper­ but fossils from oolitic most exposures of lime­ limestone, possibly a com­ stone; Hillard Limestone; posite collection; probably Middle Cambrian. Hillard Limestone; Early 4332-CO____ 61ABa2053____ A. R. Palmer and E. E. Brabb, Cambrian. 1963; 64°57.6' N., 141°11.7' 3715-CO____ 61AMc911. J. C. Melik, 1961; 64°58.2' N., W.; at east edge of flat- 141°11.7' W.; about 2,000 iron; uppermost exposures ft southwest of Adams Peak of limestone conglomerate (BM 2814), a few feet and oolitic limestone; stratigraphically above a Hillard Limestone; Middle boulder conglomerate; Hil­ Cambrian. lard Limestone; Middle 4333-CO_.__ 63ABa317l_.__ A. R. Palmer and E. E. Cambrian. Brabb, 1963; 64°58.1' N., 3716-CO____ 61AMc931. J. C. Melik, 1961; 64°58' N., 141°12.2' W.; about 35ft 141°11' W.; limestone below top of limestone float; Hillard Limestone; cliff, from continuous bed Middle or Late Cambrian. of limestone within a lime­ 4337-CO---. 63ABa3191____ A. R. Palmer and E. E. stone boulder conglomer­ Brabb, 1963; 64°58.2' N., ate unit; Hillard Lime­ 141°11.5' W.; at east edge stone; Early Cambrian. of cliff, near base, bedded 4334-CO____ 63ABa3171A._. A. R. Palmer, 1963; in limestone about 20 ft above bedded limestone about boulder conglomerate; Hil­ 20 ft stratigraphically lard Limestone; Middle above 63ABa3171; Hillard Cambrian. Limestone; Early Cam­ 4338-CO____ 63ABa3191A___ A. R. Palmer and E. E. brian. Brabb, 1963; about 100 ft 4335-CO_._. 63ABa3171B___ A. R. Palmer, 1963; in west of 70 ft stratigraphi­ boulder within limestone cally below 63ABa3191, boulder conglomerate a from boulders within a few inches below boulder conglomerate; Hil­ 63ABa3171; Hillard Lime­ lard Limestone; Early stone; Early Cambrian. Cambrian. 4347-CO. _ . _ 63ABa3172A___ A. R. Palmer, 1963; a few 4351-CO____ 63ABa3181____ A. R. Palmer and E. E. feet stratigraphically Brabb, 1963; 64°58.2' N., below 63ABa3172. 141°11.2' W.; about 10ft 4348-CO__._ 63ABa3172____ A. R. Palmer, 1963; 64°57.9' below top of limestone N., 141°12.2' W.; at base cliff and top of Hillard of limestone cliff, a few Limestone; Late Cam­ inches below a pisolitic brian. limestone bed, in slabby 4352-CO____ 63ABa3181C___ A. R. Palmer, 1963; about 30 limestone; Hillard Lime­ ft below 63ABa3181; stone; Middle Cambrian. Hillard Limestone; Late 4349-CO____ 63ABa3161--__ A. R. Palmer and E. E. Cambrian. Brabb, 1963; same Ridge and flatiron southwest of Adams Peak locality as 61AMc891, from a continuous bed of [Eagle D-l quadrangle. For accessibility, see Adams Peak area] platy limestone; Hillard 3714-CO____ 61AMc891. J. C. Melik, 1961; 64°57.7' Limestone; Late Cam­ N., 141°12' W.; about 6 ft brian. below crest of ridge and 4350-CO____ 63ABa3161A.__ E. E. Brabb, 1963; about 15 approximately 25 ft strati­ ft stratigraphically above graphically below the ap­ 63ABa3161 and 10 ft parent top of Hillard Lime­ below apparent top of stone; Late Cambrian. Hillard Limestone, in 3717-CO____ 61AMc941. J. C. Melik, 1961;64°57.8' limestone edgewise con­ N., 141°12.1' W.; at base glomerate; Late 50-ft cliff, lens within a Cambrian. thinly bedded dark-gray limestone; Hillard Lime­ stone; Middle Cambrian. A26 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

Tatonduk River area Tatonduk River area Continued [Charley River A-l quadrangle (1:63,360), 1956 edition. Not easily accessible by Geological Survey Field locality Collector, year of collection; description helicopter. Marginal heliport established on ridge about 1 mile northeast of collection of locality; stratigraphic assignment; age mouth of Thicket Creek. Best access is by boat 2-3 days after a heavy rain. Boat charter service available at Eagle. Tatonduk River may not be accessible when 4309-CO____ 60ABal31FB__ A. R. Palmer and E. E. water is low] Brabb, 1963; about 5 ft Geological Survey Field locality Collector, year of collection; description above 60ABal31FA; same collection of locality; stratigraphic assignment; age lithology; Middle Cam­ 4299-CO____ 61ABa2033___. E. E. Brabb, 1961; 65°01.4' brian. N., 141° 12' W.; north 4310-CO____ 60ABal31H___ A. R. Palmer and E. E. valley slope of Tatonduk Brabb, 1963; about 30 ft River, about 75 ft above above 60ABal31FB and 225 river level; massive gray ft above base of Hillard limestone about 10 ft Limestone; from graded thick; Adams Argillite; limestone bed; Middle Early Cambrian. Cambrian. Kirk No. 30AW62. A. E. Waters, Jr., 1930; 4325-CO____ 60ABal31JA___ A. R. Palmer and E. E. 2941 same locality as Brabb, 1963; about 55 ft 61ABa2033; Early above 60ABal31H, from Cambrian. thinly bedded limestone; Kirk No. 30AW60. A. E. Waters, Jr., 1930; Hillard Limestone; Middle 2539 about 65°01.8' N., Cambrian. 141°12' W.; altitude about 4326-CO_.__ 60ABal31JB___ A. R. Palmer and E. E. 2,000 ft, on small knoll, Brabb, 1963; about 2 ft float pieces of limestone; above 60ABal31JA; probably Adams Argillite; Hillard Limestone; Middle Early Cambrian. Cambrian. 30AW61. A. E. Waters, Jr., 1930; 4327-CO____ 60ABal3lK___ A. R. Palmer and E. E. float collection near Brabb, 1963; about 12 ft 30AW60; Late Cambrian, above 60ABal31JB and according to Edwin Kirk 295 ft above base of (in Mertie, 1933, p. 400). Hillard Limestone; from Kirk No. 30Mt77_ J. B. Mertie, Jr., 1930; pos­ thin-bedded limestone 2535. sibly the same locality as interbedded with black 61ABa2033; Early Cam­ chert; Middle or Late brian. Cambrian. 4302-CO____ 60ABal31B____ A. R. Palmer and E. E. Not collected. 60ABal31LB. A. R. Palmer and E. E. Brabb, 1963; 65°01.3' N., Brabb, 1963; about 50 ft 141°12.2' W.; north bank above 60ABal31K and 15 of Tatonduk River, in ft below the faulted (?) basal bed of Hillard Lime­ contact between Hillard stone; fossils from lime­ Limestone and limestone- stone boulder at base of chert breccia of Road limestone boulder con­ River Formation; brachio- glomerate; conglomerate is pods from thin shale bed resistant and forms ledge interbedded with limestone that protrudes into Taton­ at north edge of Tatonduk duk River; Early Cam­ River; age uncertain. brian. 4339-CO-- 63AGsl3. D. L. Giles, 1963; 65°01.3' 4303-CO____ 60ABal31A___. A. R. Palmer and E. E. N., 141° 12.2' W., north Brabb, 1963; about 90 ft valley slope of Tatonduk stratigraphically above River, about 300 ft above 60ABal31B and at the river, along strike of beds base of a second boulder at 61ABal31A; fossils conglomerate that also from bedded limestone protrudes into the Taton­ about 90 ft above base of duk River; fossils appar­ Hillard Limestone; Middle ently were in matrix of Cambrian. conglomerate; Hillard 4340-CO---- 63ACnl492-__- Michael Churkin, Jr., 1963; Limestone; Middle Cam­ same locality as 63AGsl3, brian. a few feet stratigraphically 4304-CO____ 60ABal31EA__ A. R. Palmer and E. E. higher, from matrix of Brabb, 1963; about 65 ft limestone boulder con­ above 60ABal3lA and 155 glomerate; Hillard Lime­ ft above base of Hillard stone; Middle Cambrian. Limestone; from bedded, 4353-CO- 63ACnl506_._- Michael Churkin, Jr., 1963; sandy limestone; Middle 65°01.5' N., 141°12.1' W.; Cambrian. north valley slope of 4308-CO____ 60ABal31FA_ A. R. Palmer and E. E. Tatonduk-River, about 800 Brabb, 1963; about 35 ft ft above river level, at top above 60ABal3lEA and of 100-ft limestone cliff; 190 ft above base of fossils from uppermost bed Hillard Limestone; fossils of Hillard Limestone; from calcareous concre­ Early Ordovician. tions in shale; Middle Cambrian. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN ROCKS A27

Montauk Bluff area Jones Ridge-Squaw Mountain area Continued [Charley River A-l quadrangle. Easily accessible by helicopter. Can also be reached Geological Survey Field locality Collector, year of collection; description by a difficult hike from Yukon River up unnamed creek from NWJ.4 sec. 11, T. 3 N., collection of locality; stratigraphic assignment; age R. 31 E., to center of sec. 35, T. 4 N., R. 31 E., and then east along ridge to NWJ.4 sec. 31, T. 4 N., R. 32 E.] D1072-CO RJR5-62____ R. J. Ross, Jr., 1962; Geological Survey Field locality Collector, year of collection; description 65°06.0' N., 141°02.5' W.; collection of locality; stratigraphic assignment; age coarse-grained bioclastic limestone talus, appar­ 4346-CO _ _ _ _ 63ABa3373_. _ _ A. R. Palmer and E. E. ently near base of upper Brabb, 1963; 65°08.1' N., member of Jones Ridge 141° 19.4' W.; near base of Limestone; Middle or north-facing limestone Late Ordovician, accord­ cliff, about 20 ft strati- ing to Ross. graphically above the D-1077-CO__ 62ABa2812____ E. E. Brabb, 1962; 65°04.3' lowest exposure of Hillard N., 141°02.7' W.; form Limestone; fossils from extensively sheared and bed of medium-grained faulted Jones Ridge limestone; Middle Limestone; Early Ordo­ Cambrian. vician, according to Ross. 4379-CO---- 63ABa3373A-_ A. R. Palmer and E. E. 2536-SD_..__ 30AMtl45. J. B. Mertie, Jr., 1930; about Brabb, 1963; about 200 ft 65°06' N., 141°02.5' W.; above 63ABa3373, at top from talus on northeast of cliff, in uppermost valley slope of Hard Luck exposures of Hillard Lime­ Creek; some fossils are stone; from platy, fine­ apparently from lower mem­ grained limestone; Late ber of Jones Ridge Lime­ Cambrian. stone and some evidently Hard Luck Creek area from upper member; fauna mixed, according to Ross, [Charley River A-l quadrangle. Easily accessible by helicopter. Could also be re­ ached by a long, arduous foot traverse from Yukon River. Hard Luck Creek and contains fossils of Early cannot be traversed after heavy rain] and Middle or Late Ordo­ vician age. 4376-CO____ 63ABa3611.-._ E. E. Brabb and Michael 3833-CO____ RJR7-62. R. J. Ross, Jr., 1962; 65°06.1' Churkin, Jr., 1963; N., 141°02.8' W.; along 65°11.6' N., 141°19.4' W.; upper part of Hard Luck small outcrop on west Creek; fine-grained lime­ bank of Hard Luck Creek, stone, lower member of across from cliff expo­ Jones Ridge Limestone; sures of Hillard Limestone, Late Cambrain (Trempel- about 100 ft below top eauan). of Hillard Limestone; 3834-CO _ _ _ _ RJR8-62. R. J. Ross, Jr., 1962; about fossils from bed of coarse­ 20 ft stratigraphically be­ grained limestone; Late low RJR7-62; from fine- to Cambrian (Dresbachian). medium-grained limestone, 4378-CO__._ 63ACnl751.___ Michael Churkin, Jr., 1963; lower member of Jones 65°11.9' N., 141°21' W.; Ridge Limestone; Late on spur of ridge about Cambrain (Trempeleauan). 1,500 ft west of Hard 3835-CO____ RJR9-62. R. J. Ross, Jr., 1962; 65°06.2' Luck Creek; fossils from N., 141°02.8' W.; north­ thick-bedded, oolitic, east slope of Hard Luck and partly conglomeratic Creek; very fine grained Hillard Limestone; about limestone float, probably 75 ft of the formation is from lower member of Jones exposed; Middle Cam­ Ridge Limestone; Late brian. Cambrain (Trempeleauan). 4382-CO____ 63ACnl932..._ Michael Churkin, Jr., 1963; 3836-CO---- RJR10-62. R. J. Ross, Jr., 1962; 65°06.3' 65°11.8' N., 141°25.5' W.; N., 141°02.9' W.; from on resistant limestone massive limestone cliff on knoll; fossils from medium- northeast side of Hard bedded, oolitic, and partly Luck Creek; some fossils conglomeratic Hillard also from talus; medium- Limestone; about 200 ft grained limestone, probably of the formation is ex­ lower member of Jones posed; structure complex Ridge Limestone, 500-1,500 in this area and at ft below top of member; 63ACnl751; Middle Late(?) Cambrain. Cambrian. 3837-CO, RJR6-62. R. J. Ross, Jr., 1962; 65°06' Jones Ridge-Squaw Mountain area D1073-CO. N., 141°02.7' W.; from [Charley River A-l quadrangle. Easily accessible by helicopter. Can also be very fine grained limestone, reached by a long, arduous foot traverse from Tatonduk River] probably lower member of Jones Ridge Limestone: D1071-CO___ RJR4-62______R. J. Ross, Jr., 1962; Late Cambrian (Trempel­ 65°06.2' N., 141°02.1' W.; eauan) . coarse-grained bioclastic 4300-CO---- 63ABa3352_-._ A. R. Palmer and E. E. limestone at base of cliff; Brabb, 1963; 65°04.6' N., evidently the uppermost 141°06.4' W.; ridge crest; exposure of the upper stratigraphic relation to member of the Jones 63ABa3351 uncertain; lower Ridge Limestone; Middle member of Jones Ridge or Late Ordovician, Limestone; Early Cam­ according to Ross. brian. A28 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

Jones Ridge-Squaw Mountain area Continued Jones Ridge-Squaw Mountain area Continued Geological Survey Field locality Collector, year of collection; description Geological Survey Field locality Collector, year of collection; description collection of locality; stratigraphic assignment; age collection of locality; stratigraphic assignment; age 4301-CO_--_ 63ABa3381___- E. E. Brabb, 1963; 65°05.3' 4370-CO_»_-_ 63ABa3333G_ E. E. Brabb and Michael N., 141°07.3' W.; about Churkin, Jr., 1963; about 500 ft above base of lower 70 ft below 63ABa3333F member of Jones Ridge and 215 ft below top of Limestone; Early Cam­ lower member of Jones brian. Ridge Limestone; Late 4361-CO---- 63ABa3332___. A. R. Palmer and E. E. Cambrian (Trempeleauan). Brabb, 1963; 65°06.5' N., 4371-CO_-__ 63ABa3333H__ E. E. Brabb and Michael 141°01' W.; south slope of Churkin, Jr., 1963; about Jones Ridge, altitude about 7 ft below 63ABa3333G; 4,000 ft; from massive, very Late Cambrian fine grained limestone, (Trempeleauan). about 600 ft below top of 4373-CO-.._ 63ABa3333J___ E. E. Brabb and Michael lower member of Jones Churkin, Jr., 1963; about Ridge Limestone; Late 30 ft below 63ABa3333H Cambrian (Dresbachian). and 250 ft below top of 4362-CO _ _ _ _ 63ABa3332 A_ _ _ A. R. Palmer and E..JE. lower member of Jones Brabb, 1963; about 100 ft Ridge Limestone; Late stratigraphically above Cambrian (Trempeleauan). 63ABa3332; Late Cam­ 4374-CO_--_ 63ABa3333K._ E. E. Brabb and Michael brian (Trempeleauan). Churkin, Jr., 1965; about 4363-CO _ _ _ . 63 ABa3332B_ _ _ A. R. Palmer and E. E. 75 ft below 63ABa3333J Brabb, 1963; about 200 ft and 325 ft below top of above 63ABa3332A; Late lower member of Jones Cambrian (Trempeleauan). Ridge Limestone; Late 4364-CO_--_ 63ABa3333.--- A. R. Palmer and E. E. Cambrian (Trempeleauan). Brabb, 1963; 65°06.3' N., 4375-CO..__ 63ABa3333L___ E. E. Brabb and Michael 141°01' W.; altitude about Churkin, Jr., 1963; about 3,300 ft, south slope of 80 ft below 63ABa3333K Jones Ridge; from coarse­ and about 405 ft below grained bioclastic limestone top of lower member of 35-50 ft below top of upper Jones Ridge Limestone; member of Jones Ridge Late Cambrian. Limestone; Middle or Late 4380-CO _ _ _ . 63 ABa3362A. _ _ A. R. Palmer and E. E. Ordovician (Caradocian), Brabb, 1963; 65°04.2' N., according to R. J. Ross, Jr. 141°07.0' W.; along crest 4365-CO _ _ _ _ 63ABa3333 A_ _ _ E. E. Brabb and Michael of ridge; limestone at this Churkin, Jr., 1963; same locality is extensively locality as 63ABa3333 but deformed and contorted, 12 ft below top of upper presumably by folding member of Jones Ridge and faulting but possibly Limestone; probably same by deformation contem­ age as 63ABa3333, accord­ poraneous with deposition; ing to R. J. Ross, Jr. Late Cambrian 4366-CO _ _ _ _ 63ABa3333B_ _ _ E. E. Brabb and Michael (Dresbachian). Churkin, Jr., 1963; about 4381-CO__._ 63Aab3351..___ A. R. Palmer and E. E. 30 ft below 63ABa3333A Brabb, 1963; 65°04.8' N., and about 13 ft above base 141°06.2' W.; on ridge of upper member of Jones crest about 1,000 ft south Ridge Limestone; probably of triangulation station Middle Ordovician, accord­ Hi-yu (BM 4839); from ing to R. J. Ross, Jr. massive limestone, lower 4367-CO _ - _ _ 63ABa3333D _ _ E. E. Brabb and Michael member of Jones Ridge Churkin, Jr., 1963; about Limestone; Late Cambrian 70 ft below 63ABa3333D (Dresbachian). and 50 ft below top of lower 4387-CO-_._ 63ABa3333M__ E. E. Brabb and Michael member of Jones Ridge Churkin, Jr., 1963; Limestone; Early Ordovi­ 65°06.3' N., 141°01' W.; cian, according to R. J. altitude about 3,200 ft, Ross, Jr. south slope of Jones Ridge; 4368-CO _ _ _ _ 63ABa3333E_ _ _ E. E. Brabb and Michael from thin ledge of crinoidal Churkin, Jr., 1963; about 7 limestone within unnamed ft below 63ABa3333D and chert and shale unit; about 57 ft below top of Late Ordovician, according lower member of Jones to W. A. Oliver, Jr. Ridge Limestone; Early Kirk No. 2533 30AW58. A. E. Waters, Jr., 1930; Ordovician, according to about 65°05' N., 141°07.5' R. J. Ross, Jr. W.; from limestone talus 4369-CO _ _ _ _ 63 ABa3333F_ E. E. Brabb and Michael along crest of ridge; Churkin, Jr., 1963; about stratigraphic position 85 ft below 63ABa3333E uncertain; probably lower and 145 ft below the top of member of Jones Ridge lower member of Jones Limestone; Early Ridge Limestone; Early Cambrian. Ordovician, according to R. J. Ross, Jr. STRATIGRAPHY, CAMBRIAN AND ORDOVICIAN BOOKS A29

Jones Ridge-Squaw Mountain area Continued Extension of Hillard Peak area, in Canada Continued Geological Survey Field locality Collector, year of collection; description Geological Survey Field locality Collector, year of collection; description collection of locality; stratigraphic assignment; age collection of locality; stratigraphic assignment; age 30AMtl46_._ J. B. Mertie, Jr., 1930; about 3505-CO__-_ 60ABa71. E. E. Brabb and H. J. 65°06' N., 141°02.7' W.; Roepke, 1960; 64°59.4' northeast side of Hard N., 140°59.1' W.; south Luck Creek; from very bank of Tatonduk River; fine grained limestone, from upper part of probably lower member of Hillard Limestone; Late Jones Ridge Limestone; Cambrian. Late Cambrian according to Edwin Kirk (in Mertie, Miscellaneous localities 1933, p. 400). 5156-CO_.__ 60ABal84A__ H. J. Roepke, R. N. 30AMtl47. J. B. Mertie, Jr., 1930; about Passero, and E. E. Brabb, 65°06.2' N., 141 002.8' W.; 1960; Charley River A-l stratigraphically below quadrangle, 65°00.3' N., 30AMU46, probably lower 141°02.2' W.; south bank member of Jones Ridge of Tatonduk River, about Limestone; Late Cambrian, 200 ft downstream from according to Edwin Kirk mouth of unnamed creek; (in Mertie, 1933, p. 400). fossils from limestone; GSC-273____ XIXp20_ D. D. Cairnes, 1912; about stratigraphic position 65°04.3' N., 141°02.7' W.; uncertain; Early probably from Jones Ridge Cambrian. Limestone; Early Ordovi- 5158-CO____ 60ABa203. E. E. Brabb, 1960; Charley cian. River A-l quadrangle, Extension of Jones Ridge-Squaw Mountain area in Canada 65°02.1' N., 141°03.8' W.; [Localities plotted from sheet 19 of the International Boundary Commission (1:62,500), east bank of Funnel 1914 ed., and from unpub. data] Creek, extensively de­ GSC-264____ XIXj9______F. J. Barlow, 1912; about formed grayish-black 65°01.8' N., 140°59.8' W.; bioclastic limestone; from limestone; Late Cam­ Early Cambrian. brian. 5159-CO____ 60ABa204. E. E. Brabb, 1960; Charley ---_____-_-_ XIXJ17, 18__._ F. J. Barlow, 1912; about River A-l quadrangle, 65°03.6' N., 140°59.8' W.; 65°02.2' N., 141°03.7' W.; altitude about 4,400 ft, along Funnel Creek, from fine-grained lime­ grayish-black limestone; stone, presumably Jones Early Cambrian. Ridge Limestone; Late 5157-CO____ 60ABa206. R. N. Passero and E. E. « Cambrian, according to Brabb, 1960; Charley L. D. Burling (in Cairnes, River A-l quadrangle, 1914a, p. 63). 65°00.9' N., 141°02.9'W.; GSC-266_.-_ XIXJ31.______W. S. McCann, 1912; about from limestone along 65°06.6' N., 140°59.8' W.; Funnel Creek; Early altitude about 3,600 ft; Cambrian. Jones Ridge Limestone; Kirk No. 30AMtl36. J. B. Mertie, Jr., 1930; Late Cambrian. 2528. probably same locality as GSC-267_.__ XIXJ32.______W. S. McCann, 1912; about 60ABa206; Early 65°06.8' N., 140°59.8' W.; Cambrian. altitude about 4,500 ft, Kirk No. 30AMt214_ J. B. Mertie, Jr., 1930; presumably from the upper 2532. Charley River A-l part of Jones Ridge Lime­ quadrangle, about 65°04.1' stone, Middle Ordovician. N., 141°08.5' W.;from limestone float; Early Extension of Hillard Peak area, in Canada Cambrian(?). [Localities plotted from sheet 18 of International Boundary Commission (1:62,500, 4377-CO____ 63ABa3523____ E. E. Brabb, 1963-in 1914 ed., and from unpub. data] Canada east of Charley XXe39. F. J. Barlow, 1912; about River B-l quadrangle, 64°59.4' N., 140°57' W.; 65°23.3' N., 140°59.5' W.; probably on south valley from uppermost bed of slope of Tatonduk River, 30-ft-thick limestone from thick-bedded lime­ underlying and presum­ stone, probably Hillard ably in fault contact with Limestone; Late Cam­ limestone of Devonian brian according to L. D. age and overlying dolomite Burling (in Cairnes, 1914a, of unknown age; Late p. 65). Cambrian (Franconian). GSC-278.___ XXc29. F. J. Barlow, 1912; about Occurrences of Oldhamia in Alaska 64°56.1' N., 140656.8' W.; altitude about 2,900 ft, [Age determinations by Churkin and Brabb (19656)] from limestone, probably M1024-CO__ 62ACn851._ _ Michael Churkin, Jr., 1962; Hillard Limestone; Late Charley River B-2 quad­ Cambrian. rangle, 65°20.2' N., GSC-282_.__ XXi34. F. J. Barlow, 1912; about 141°46.0' W.; Adams 64°57.1' N., 140°59.1' W.; Argillite; probably Cam­ altitude about 3,000 ft, brian. from limestone dipping 70° NE., probably Hillard Limestone; Middle Cambrian. A30 LOWER PALEOZOIC PALEONTOLOGY AND STRATIGRAPHY OF EAST-CENTRAL ALASKA

Occurrences of Oldhamia in Alaska Continued Cairnes, D. D., 1914a, The Yukon-Alaska international bound­ Geological Survey Field locality Cottector, year of collection; description ary, between Porcupine and Yukon Rivers: Canada Geol. collection of locality; stratigraphic assignment; age Survey Mem. 67, 161 p., 16 pis. M1025-CO__ 62ACn891._- Michael Churkin, Jr., 1962; Charley River B-2 quad­ 1914b, Geological section along the Yukon-Alaska bound­ rangle, 65°20.0' N., ary line between Yukon and Porcupine Rivers: Geol. Soc. 141°45.7' W.; Adams America Bull., v. 25, p. 179-204. Argillite; probably Cam­ brian. Churkin, Michael, Jr., and Brabb, E. E., 1965a, Ordovician, M1026-CO__ 62ACnl081____ Michael Churkin, Jr., 1962; Silurian and Devonian of east-central Charley River B-2 quad­ Alaska: Am. Assoc. Petroleum Geologists Bull., v. 49, no. rangle, 65°19.4' N., 2, p. 172-185. 141°5p.3' W.; Adams Argillite; probably Cam­ 1965b, Occurrence and stratigraphic significance of Old­ brian. hamia, a Cambrian trace fossil in east-central Alaska in M1027-CO _ _ 63ACn2091_ _ _ _ Michael Churkin, Jr., 1963; Geological Survey research 1965: U.S. Geol. Survey Prof. same locality as 62ACn- 1081; probably Cambrian. Paper 525-D, p. D120-D124. M1028-CO _ _ 63ACn2126_ _ _ _ Michael Churkin, Jr., 1963; Douglas, R. J. W., and others, 1963, Geology and petroleum Charley River B-2 quad­ potentialities of northern Canada: Canada Geol. Survey rangle, 65° 19.7' N., Paper 63-31, 28 p. 141°43.4' W.; Adams Argillite; probably Cam- Eakin, H. M., 1918, The Cosna-Nowitna region, Alaska: U.S. brian. Geol. Survey Bull. 667, 54 p. M1029-CO__ 63ACn2212_._. Michael Churkin, Jr., 1963; Goddard, E. N., chm., and others, 1948, Rock-color chart: Wash­ Charley River A-2 quad­ rangle, 65° 13.4' N., ington, Natl. Research Council (repub. by Geol. Soc. Amer­ 141°37.0' W.; Adams ica, 1951), 6 p. Argillite; probably Cam­ Green, L. H., and Roddick, J. A., 1962, Dawson, Larsen Creek, brian. M1030-CO _ _ 63AGs344B___. D. L. Giles, 1963; Charley and Nash Creek map-areas, Yukon Territory: Canada Geol. River A-2 quadrangle, Survey Paper 62-7,20 p. 65°14.7' N., 141°37.6' W.; Kindle, E. M., 1908, Geologic reconnaissance of the Porcupine Adams Argillite; probably Cambrian. valley, Alaska: Geol. Soc. America Bull., v. 19, p. 315-338. ______21AMtl52_____ J. B. Mertie, Jr., 1921; Mertie, J. B., Jr., 1930, Geology of the Eagle-Circle district, Livengood D-2 quad­ Alaska: U.S. Geol. Survey Bull. 816, 168 p. rangle, about 65°54' N., 147°44' W.; altitude 3,000 1933, The Tatonduk-Nation district: U.S. Geol. Survey ft, unnamed formation; Bull. 836-E. p. 347-^43. probably Cambrian. 1937, The Yukon-Tanana region, Alaska: U.S. Geol. Sur­ KP0245. BP Exploration Co. (Alaska) Inc., 1962; Circle C-3 vey Bull. 872, 276 p. quadrangle, 65°43' N., Okulitch, V. J., 1955, , in Moore, R. C., ed., Treatise 145°04.3' W.; from un­ on invertebrate paleontology. Part E, Archaeocyatha and named argillite and quart- Porifera: New York and Lawrence, Kans., Geol. Soc. Amer­ zite formation; probably Cambrian. ica and Univ. Kansas Press, p. E1-E20. 1956, The Lower Cambrian of western Canada and Alaska, REFERENCES CITED in Rodgers, John ed., El Sistema Cambrico, su paleogeo- grafia y el problema de su base symposium, pt. 2: Internat. Brabb, E. E., and Churkin, Michael, Jr., 1964, Preliminary Geol. Gong., 20th, Mexico City, 1956, p. 701-734. geologic map of the Charley River quadrangle (1: 250,000), Okulitch, V. J., and Greggs, R. G., 1958, Archaeocyathid localities east-central Alaska: U.S. Geol. Survey open-file report. in Washington, British Columbia and Yukon Territory: 1965, Preliminary geologic map of the Eagle D-l quad­ Jour. Paleontology, v. 32, no. 3, p. 617-623. rangle (1:63,360), east-central Alaska: U.S. Geol. Survey Ross, R. J., Jr., and Dutro, J. T., Jr., 1966, Silicified Ordovician open-file report. Brooks, A. H., 1911, The Mount McKinley region, Alaska: U.S. brachiopods from east-central Alaska: Smithsonian Misc. Geol. Survey Prof. Paper 70, 234 p. Collns., v. 149, no. 7, 22 p., 3 pis. Brown, J. S., 1926, The Nixon Fork country and silver-lead Sainsbury, C. L., Previously undescribed Middle (?) Ordovician, prospects near Ruby: U.S. Geol. Survey Bull. 783-D, p. Devonian (?), and rocks, White Mountain area, 97-150. near MeGrath, Alaska, in Geological Survey research 1965: Buddington, A. F., and Chapin, Theodore, 1929, Geology and U.S. Geol. Survey Prof. Paper 525-C, p. C91-C95. mineral deposits of southeastern Alaska: U.S. Geol. Survey Steidtmann, Edward, and Cathcart, S. H., 1922, Geology of the Bull. 800, 398 p. York tin deposits, Alaska : U.S. Geol Survey Bull. 733,130 p.

U.S. GOVERNMENT PRINTING OFFICE: 1967 O 232-493