IMAGE EVALUATION TEST TARGET (MT-3) li /. {./ A I I Q- C/a fA 1.0 I.I 1.25 If: iia ■^ IIIIIM IIM IIIW 118 U llllli.6 d w/ Photograpliic Sciences Cornoration 23 WEST MAIN STREET WEBSTER, NY. 14580 (716) 872-4503 A ■17 ,\ iV \\ "% V *> *> ^. u ..■sis- * .«^ 7v \*^' /. ** ,ambrian or Potsdam horizo n UPPER CAMBRIAN = POTSDAM OR DICELLOCEPHALUS. MIDDLE CAMBRIAN Cer>tral horirnn of Middle Cambrian .= GEORGIA OR OLENELLUS LOWER CAMBRIAN = ST. JOHN SERIES. NEWFOUNDLAND AND BRAINTREE, MASS.. OR PARADOXIDES. Base of Cambriar< PRE- CAMBRIAN and ARCHEAN: 1 J- ca^ i\ovpnl'ifpd on the general section with in the diagram (fig. 1) aie piacea on "^"^ & ,, , Dj^^ello- relation to the stratigraphic position of Olenellus and uiceiio cephaluB, or Georgia and Potsdam faunas. C. D. Walcott — Cambrian Syatem of Worth AineHca. 141 >n la n- The first section (fiff. 2) to which I wish to direct your atten- tion is that of the Wasatch Mountains, in Utah, where the Cambrian is well shown in Big Cottonwood Caflon. The section is described in the reports f>f the Geologists of the .-l-s-go-^is with cello- .m o.S 5 ^ "^ o c g * c 2 ^ •=. s, i (^ '^ ■5 = >&^ 22. a KJ 9. O a >ar3 q I- a 41 X 5 ■s a • "a - S2 2^ CjS -cii ^ a a- m a fc- ~ c o t^ ^^ a o.s a o S:5 >,ji O <-i •^ .M .M ^ '— t^ ** ao S§2- .£ a . a [J- "^ ^— <:^ c a SB o o Sort •-— S ■" " V. 9,A 05 S a a, "- ■ — O _:- rj c3 CO „ - St. tj a o jS 'E P -c o c SsCC 01 CC i;HK)^C ii^ Fortieth Parallel Survey (Geol. Expl. 40tli Par., vol. i, p. 229 ; vol. ii, p. 366), but I had the opportunity of examining it more in detail during the summer of 1885, and through finding the U2 a D. Wah'ott—CamhHan Si/stem of Nortf, America. Olenellus or Middle Cambrian fauna, located its upper horizon and ascertained that the entire Upper Cambrian was absent by non-deposition, the Silurian resting eonformal.ly on strata of Mid- die Cambrian age. The section at the base resls on granite near Hl'^ £5^ . ^ o •- -f .2 "a '^ _. ^ 2 "^ " * » "p ^ ,3 ._-o o <^ * > = = Q » C ip ~ 3 O _ * -, ^^ • •- j^ O .r '"' m o al 0) - s ■> 5 5? S ta cs got a> r. S u. .-2! «r C - J "■ -=" S- 3 2 ■— o c, - _- © -o 5*2 a - P ■S rt a 5 Q . ^ " « 2 *s u •S: o S g S t> •:- ^ « - g _ 2 3 o ^ « . •- o o o ra 0 es S rr -t §r^'l|-i •r -e S^ CO .2 -3 « h ■■« : -«-- 5 CO a - ^ n o '-i 3 ~ 5 „ o a> -J i; P S ?^ a a a <^ tt; ~ fcN a y )r tz; ^^ _J^ a *. 2 £ ® .2 iJ a as K a o CO the mouth of Big Cott^ mwood Cafion, and the strata continue up tbe caSon in an unbroken, conformable series of siliceous rock snales, quartzites and sandstones, until 12,000 feet in thickness I * 1 oa. C. D. WuJcott—Cuinhrian Si/stcm of North Am erica. 143 rizon tit by Mid. near up ck, ess IS passed through. In the upper 250 feet of silieo-arcrillaceous shales that rest on a massive band of quartzite, 8,0n0 feet in thickness, the following fossils occur: Cmziana?, Linrfulella Ella, Kutorgina pannula, Ilyolithes BilUnr/si\ Leptrdltia Argenta, Oloiellus OUhertl, Plychoparia nuadrans and liath>i>inscus pro- duda. This fauna is also found at a similar horizon in several localities in Nevada; and the lithologic, stratigraphic and paleontologic evidence, as found in the Oquirrh and Tintic ranges of Utah and the House, Eureka and Highland ranges of Central Nevada, extends the same horizons throughout the western and southern portions of the Great Basin area. The entire absence of fossils in the lower portions of the Wasatch section may be owing to the character of tlie sedi- ments ; but an attempt is made further, to explain the absence of the Lower Cambrian fauna of the Atlantic area. The second section (fig. 3), that of the Eureka* District, by Mr. Arnold Hague, stratigraphically overlaps that of the Wasatch, the lower 1,500 feet of quartzite corresponding to the upper-half of the 3,000 feet of quartzite of the Wasatch sec- tion, and the Olenellus shales occurring at the same horizon on the summit of the quartzite; but here the Lower Silurian (Ordovician) strata do not rest on the siliceous Olenellus-bear- ing shales, but are separated by over 6,000 feet of limestone that carries a fauna uniting the Middle Cambrian fauna with the Upper Cambrian or Potsdam fauna, which begins in its characteristic forms 4,500 feet above the 01enellu°s horizon. One hundred miles south of Eureka, in the Highland Range, f found the Eureka section essentially repeated and identical spe- cies occurring at the same relative horizons in each section. The vertical range of the Eureka section embraces the corres- ponding strata of the Highland Range section and several sec- tions that occur in Nevada and Western Utah, Section No. 3, fig. 4, is unlike either of the first two sections ' in having the Upper Cambrian well developed, and the Middle and probably the Lower Silurian (Ordovician), entirely absent! This section is beautifully exposed in the deeper portions of the Grand CaSon of the Colorado, Arizona, and was first made known in a general way, througli the explorations of Major J W. Powell in 1875. During the winter of 1882-83, Major Powell instructed me to make a detailed section of the strata in the depths of the cafion, and fig. 4 is one of the results of tue work. The Upper Cambrian, or Tonto formation is 1,000 feet m thickness, composed of siliceous and calcareous strata and carries a fauna that unites it closely with that of the Upper Cambrian of Nevada, Texas and the Upper Mississippi Valley. Beneath the Tonto there is a great mass of strata, over 12,000 feet in thickness, that are unconformable to the horizontal Tonto U4 a D. Wahoti-Camh'ian Sudem of Sorih America. 1 ♦» « Ki.rVilv.inclinea (Huroninn?) strata beneath, strata above and the J^'K'h^ " "^^^^^^^^^ ■ ^ ^\,^ Cambriun I have hereto ore re; er d ^^^^^^^ J^" ,^ W scor.sin and LUuio 1.2 11111 _ O tn as 55 ' -, S ft tf. _! 5 ,2 B Zi j: -z --^ '" ^ 5 >. 3 >. 5 7 ® f.'TS O - *j £ O 3 s' « i y r-r = ii b M B ^ U = .C 3 -C — t ' J3 — -^ ■if-^^;: 2 2 *j c: ^ 'X3 r^ _ g P « 2 'S :S ■' a o "-^ * 1 ts X e 9 •« :; s ii -S - ^- _os®;S"5aJ„^ 5 2 c! "" c 3 3 ^ a 'S 2 5 2 2 ?, ^ " S( o I JO 2 ^ o K-< Or '- a - >, 2 ^ 2 o 5 '2 o S ^, ~ « o Mo jjji a g 5 o ^ I? S ?§ J "s -i I i ( << „„i AocTVPP with the Cambrian, pre-Cambrian and a system of equal ^^SJ^^/^^^'^^.e the strata Lwer Silurian (Ordovician), etc J^ JJ^^ ^^ ,,ith theHuro- below the Grand CaSon senes will be ^one\^l\^^^^^^^ ,^ .gain nian of the Wisconsm section, i his wu ' C \' h. in no 6 ! 2 i -» ibrian, 1 strata ! Huro- » again. C. I). Walcott^Camhnan Syatem of North Anurloa, 145 The Grand Canon section is typical and iticludos with it the Cambrian section of Central Texas and Northern Wisconsin (see figures 5, ♦»). Crossing to the eastern side of tlie Continent, our next sec- tioii (fig. 7, p. 148) of the Cambrian strata is taken in North- western Vermont, and its contained faunas icrvo to connect the distant Nevada sections and the group of Cambrian sections along the St. Lawrence, Champlain, and Hudson River Valleys. At the base of the section a massive belt of limestone, 1,000 feet in thickness, carries in its upper portions the Olenellus fauna which, in the argillaceous shales capping the limestonch, attains an extensive development. Continuing up in the sec' tion through the argillaceous shales, about 2,000 feet, masses ■ <^^^. Fig. 5.— Section in Llano County, Tcxns, sliowin^ W\v, rolationH of tlio Upper Cambriiin (Potsiiatn) and the pre-Cambrian Llano Series. of limestones are found interbedded in the shales, and in the limestone fossils that show tbe near approach of tl e Upper Canibrian or Potsdam fauna. The section gives the same suc- cession of fauna as the sections of Nevada, where we find posi- tive stratigraphic proof of the great difJ'erence in age of^ the Middle and Upper Cambrian faunas. The Georgia, Vermont, section includes, in its vertical range, the sections about and below Troy, N. Y., in the Hudson Rivet- Valley, and those of Northwestern Newfoundland and the Straits of Belle Isle. Directly east of the Adirondack Mountains of New York, t!ie ''otsdam sandstone is overlaid by a stratum of shaly arenaceous rock full of fucoidal, or annelid markings, and there the Chazy limestones appear resting on the latter.* Tracing the sandstones south, a fine exposure is seen at Ausable Chasm, and continuing south a limestone is found coming in on top of the sandstone that, in Saratoga County, contains a well-marked fauna of twelve species, four of which are identical with species in the upper beds of the Wisconsin Potsdam sandstone. The calcareous layers of the Potsdam also occur at Whitehall, and Professor Dwight has found them near Poughkeepsie. * The unconformity, by non-deposition, noticed by Sir William LoKfii:, is nowhere better illustrated than at this point, the Calcifcroua forinuti.)n beinir absent from the section. ■ 146 C. D. Wahott—Camlmcm System of Is^'oHh America. >, < \ Durincr the deposition of the Potsdam sand- stone the shore-line was close at hand, and the Adirondack area famished material for the formation. Out from the shore-lme the mud and sand were mixed, and stdl farther out, over the present area of the Georgia section the shales with interbedded limestones po; it to deeper, quieter waters. I have yet faiied to find in Vermont any Potsdam sandstone north of Burlington; and the evidence goes to prove that the ui)per portion of the Teor- cia section, with its shales and "lentiles of limestone, is equivalent to the Potsdam sandstone about the Adirondacks. We have now hastily reviewed the princ ■ pal sections of the Cambrian under which all the others now known can be groupea except those of Braintree, Massachusetts, bt. John New Brunswick and the southeastern Newfoundland sections. These are not con- nected paleontologically with the more west- ern section and we distinguish them as the Atlantic border sections, and mostly ot older date-- than the strata of all but tl^e lower ■ portions of the Wasatch, and perhaps the ien- i nessee sections. As the position of the At- i lantic border Paradoxides fauna is determined ^1 on paleontologic evidence, the discussion oi it "^ ? will be taken up later. •il In the following table, the writer expresses - II his view of the dassification of the various M^ formations that go to make up t^e Cam- s '; s brian system of North America. It is hub- Sitlject to revision in details, but the main t? 1 -= divisions are based on pa eontologic and ^-1 stratigraphic data, that I think w^"/'.^/'/ -I them of service in the permanent classihca- t § % tion of American Paleozoic rocks. 2 1^ It is not claimed that the arrangement of e ^ " the formations in the following table is orig- I -^1 inal with me, as, with some changes in nomen- 8 ^ -o clature, it is the same as that to be found I on page 40 of the Report of the Geological of the Cambrian ^^l^tem. fo'i^; ' - J'''l '^^^^^ predominates^, and the upper faunas -•^^^ '""; ^T'^^^^^Z^^W^^oC^^^^ Atlantic than to the interior Si,i:7uSi;^.-;'!x;::" l nnd a numher of species common to each. o \ C. D. Walcott— Cambrian System of North America. 147 Classip'catiou of North American Cambrian Rocks. Lower Calcifer- ous. ri'CKR CAMBHIAN-. Lower portion of the Calciferoua ibrnintiou of New York and CannJa. Lower Magnesiaii _oMVisoonsin, Missouri, etc. Potsdam of New York, Canada, Wisconsin, Texas, Wyoming. Montana and Xpvada : Tonto of Arizona : Kno.x Slialos of Ten- nessee, Georgia and Aialiama. The Ala- bama section may extend down into the Middle Cambrian. Georgia formation of Vermont, Canada and New York. Minni-K CAMiiRi.w.^'-'^"'^'^ '^" ^°"P- Limestones of L'Anse an Loup, Labrador. Lower part of Caiiil)rian section of J'hireka, and Highland Range, Nevada. Upper Por- tion of Wasatch Cambrian section, Utah. Paradoxides beds of BraintreeTMassTTsr. John. New Brunswick. St. John's area of Newfoundland. Lower portion of Wasatch section, Utah. The Ocoeo conglomerate and slates of East Tennessee a re doubtfully included. LOWER C.VMIiKI.V.N'. Prospect. 8t. John. Braintree, Newfoundland. Wasatch. Tennessee. Survey of Newfoundland for 18^hVi^re't'he%r.r-^^ the two systems. At present it is to a large extent wanting 6nf»i fawjia^.-Tha the stratigraphic position of the Mh die of the Potsdam fauna is shown by the Eureka and Hicrhi.nd monf '^n'^ '' d" ^'"^'^' "^^ '''' ^^<^'-«-^ section i'°''C mont. In Nevada, in two sections unbroken by faulting or o e'hLlr'r ^nd'^^trVT^'^^'-^ a geographi; dTsi^nc^e o 9nnn f innn'r ,^"enty-five miles, the fauna ranaes from 2,000 to 4 000 feet below strata carrying a typical UpSer Cam b nan, or Potsdam fauna. But threi species, Voto^Ca % " estrata, Acrotreta gemma and Stenotheca elougata !4eTnown o Fss up to the Upper Cambrian or Potll m horizoT I,i the Georgia, Vermont, section, one of the sj^ecies P/^coVa 150 6'. D. Walcott—Camhr'um System of North America. \,h,,„,i -.nnears to pass ui) into the Potsdam horizon of the ; Son ;E",e\lna is ^more like that of the Potsclan^ and of the other species, Orthishm Orientahs is niuch ike 0. Fepom of the Potsdam sandstone of AV^seonsin : b^^^the fauna a. a whole IS so clearly distinct from the typical Potsdam of ^ew Yo?10Visconsin, 'Tennessee, Alabama, Texas, An.ona Nevada and Montana that, even without any section to show their rela- tions to each other, I should not think of correlating them as contemporaneous faunas. ,,.,■,, /->, • c v^ The stratigraphic relations of the Middle Cambnan fauna to the Paradoxkles fauna of St. John Braintree and Newfound- and are not so clearly proven as for the Middle, and Lpper Cambrian faunas. Tlie only locality known - -- jhe two faunas are in the same geographic area is about Concep tion Bav Newfoundland. At Topsail Head abou UHJ_ teet ot Sstone is exposed, overlaid by dark shale. AH stratigra,^iic connection with other sections in the vicinity is broken. The fossils in the umestone are not numerous, but Mr. Bdbngs pio- nou need them Potsdam (Geol. Newfoundland p. lob, repnn o^Tport for 1868), and identilied Saltereda Cr«;ua (prolmbly Kutoljma) Lahvadoriccu and I found, m the col ection of the Geological Survey of Canada, SceneVa reliculata, ^^tenoth^ rugosa, Iphidea bella and Protypus senectus ^^%.^f ^/f "^j;^;^^^^ gives six species that are also known from the Middle 0am b 'an horizon of L' Anse au Loup.^ Special stress is placed by the writer on the occurrence of these fossils at Topsail Head as it is in the midst of the Paradoxides basin. Mr. Alexande Murray correlated the Topsail Head limestone w i h that of ot er localities, and places it beneath the Paradoxides-bearing shales of St. Mary's Bay (on the page cited above), but without p'deontologic or stratigra, c evidence that can authorize him to ^ay more than that a supposed connection is indicated. Not having stratigraphic evidence o the relation of tlie Geoi-ia or Middle Cambrian fauna and the Paradoxides or Lower Cambrian (Ordovician) fauna other than that they occur Tn the same area and are not in the same stratum of rock, we turn to the faunas to aid us in the settlement of the question. Of the thirty-two genera of the American Paradoxides hori- 7on fifteen pass up into the Olenellus horizon, viz: Arenico- mes, Ssi^ongia,^rch.eocyathns?, Eocv-stites ? ?, Linguel o, Ac otreta, Acroihele, Kutorgina, Orthis, Stenotheca, Ilyolithes Aonostus Microdiscus, Solenopleura, and Piychopar.a. Of these, eleven, Arenicolites, Protospongia, Lingulella, kutorgnia, A^otreta, Orthis, Hyolithes,. Stenotheca,. AgnostusM^^^^^^^^ cus? and Ptychoparia, continue on up into the I otsdam oi * \[r BiUines ealkMl all the Mi(Mle Ca.ubrmn fauna - Lower I'oisclam/ explains his rcfernng the Topsail Head fossils to the Potsdam. which \ C. 1). Walcott—Camlrian System of North Amerim. 151 Ui.l)er Cambrian honpcon, leaving but four genera that are alone common to the Middle and Lower horizons. One genus Dendrograptus, is doubtfully identified in the ParadSxides lon^ion ot New Brunswick thai occurs in the Upper Cam- brian, and is, as yet, unknown in the Middle Cambrian The genus Agraulos IS also found in the Lower and Upper, but not in the Middle Cambrian. Of species, not one of the 76 . ^ ^r"\®!','^"^ ^°'''^'' Cambrian fauna are known to occur 111 the Middle Cambrian fauna, which, with its 107 species stands out clearly from the older fauna and also from the more recent Potsdam fauna, as but three of its species, Protosponaia /enestraia, Stenotheca elongata and Acrotrela qemma, are known to occur in the Upper Cambrian, and l(i of the genera in the Middle Cambrian are not known to pass up into the Upper Cambrian or into the Lower Silurian (Ordovician) faunas Not one species is known to be common to the Lower and Umer Cambrian horizons. Having studied the Middle Cambrian fauna more thoroucrhly thiin that of the lower and upper horizons, I will speak of it on that account and, also, from the fact that its character and geographic distribution is not as well known as the other two As a whole, we notice that it combines the characters of the Lower Cambrian and Upper Cambrian faunas and yet is dis- tmct from each of them. There does not appear to be an equivalent fauna in the Cambrian system of Europe either in Jiohemia the Scandinavian area, or in Wales; but from the Island of Sardinia, Dr. Bornemann has described a groui^ of sponge-like bodies closely related, if not identical with Ethmo- phtjUumiiwd ArchcBocyathus of the American Middle Cambrian fauna; be also names Kuiorgina cingulata which is found at this horizon both in Vermont and Labrador. A species of tnlobite IS referred to Olenellus, but I have not seen any illus- tration of it. Tlie conditions that developed the Middle Cambrian fauna ai^pear to have been largely peculiar to the American continent. i)unng the depo.sition of the St. John's series of the Lower Cambrian, or the Paradoxides strata, we learn from the Euro- pean and Eastern American sections, that the fauna was essen- tially of the same type over the entire basin (Atlantic), and from evidence known to date, that the fauna did not extend west of a line passing northeast through f:astern Massachusetts to A'ew Brunswick and Newfoundland. That there were deposits of sediment to preserve the fauna, if it extended westward, is shown by the thousands of feet of sediments below the Middle Cambrian faunas of Utah and Nevada. From the data we now have, I think that during the exist- 152 C. D. Walcott — Caiabrian System of North Amerioa. ence of the greater portion of the Lower Cambrian (Parudox- ides) fauna, a barrier existed that prevented its extension west- ward of the line mentioned ; that towards the close of the time of the Paradoxides fauna that barrier was removed to the northeast, in the vicinity of Newfoundland, and the descend- ants from the Paradoxides fauna entered the westward seas and spread to tiie eastern and western ])asius and formed the Middle Cambrian fauna. What route was taken by the Middle Cam- brian fauna after passing to the western side of the outer barrier is not yet traced, but I think from the indications we now have of a continental area, during Lower and Middle Cambrian time, in the central portion of the continent, that the fauna passed to the south around the southern end ot the then existing land, and thence north along the west shore. In the Atlantic basin, the Paradoxides fauna persisted to a greater or less extent and mingled with the types of the Upper Cambrian fauna as in the Upper Lingula Flags of Wales. If this is a correct interpretation of the evidence now known, we may look in vain in the central interior basin for the Para- doxides fauna of the Atlantic basin. That there was life in the older Cambrian or pre-Cambrian seas of the central interior basin, there is no doubt, as we have found traces of it in the Grand Canon section of Arizona ; and the development of that fauna which from the stratigraphy is pre-Cambrian, is one of the problems awaiting solution. During the Upper Cambrian (Potsdam of America; Upper Lingula Flags ot Wales), the Atlantic and Pacific basins ai)pear to have had free communication with each other, and the faunas now have a facies of the same general character. The above views are, to a certain extent, theoretical, but the facts demand an explanation other than that the faunas of the Lower, Middle and Upper Cambrian were contemporaneous but in different geographic areas. That the upper and middle faunas were separated by a great interval, is shown by the sec- tions in Nevada and Vermont; and that the middle and lower faunas were not contemporaneous is shown by the biologic evidence and the indirect evidence of the absence of the lower fauna in association with the middle fauna in the Newfound- land area, where they are now found in different strata, but a short distance from each other. A diagram illustrating the Cambrian sections of America and Lurope would show, in the former, that the sequence of life is divided more sharply into three great groups that, in the latter, are more or less broken up. First: by the nearly entire absence of the middle group, and secondly, by the commingling of the upper and lower groups in the European strata and pos- sibly in the Atlantic border sections of New Brunswick and a D. Walcott- Camhrian System of NoHh America. 153 Newfoundland This subject will be treated in detail after the con^leuon ot the study of the Upper Cambrian faunas now in a..tfrl 'p''^:''^"^^^^, mentioned, I have heretofore included the Grand Oauon and Llano series as, in part, of Cambrian -ure and correlated them with the Keweenaw series (Bull YI Phfl'soo I"e'm?f b'e'nWed''''.^- '" ^'^P'^"^' ^'^ vieV't^it'alfo'f cnese may be placed under a system of preCaml)rian ipp t tlnnk there ,s good reason for ft in the pWnce o the Irkt s" en *Tn f 'th^ ero^on, between the strala of the KeweeTaw ^e^of tt utt r' T'^' ^^^t^overlaid^VthTh'^rfzSS Grand C.LnTV ^^.7'"' ^"'^ '" the Keweenaw, and the separated ?rom h.'T'' r' ^^f '^[^'^ °^ ^'^'^^^ ^^ i» ^"rn nT Srand r.Hn" ^ ^'^°'" V "" ""conformity that, o?.o i " °'^"' .^.^ ''^'■^ g''®^*' and in the Lake Suoerior area sufhc.ent to indicate an orographic movement Sous sec 'oL rf r\' n''' """"^"f %«• ^^^ three'^^JZ sections (tigs. 4, 5, b) agree in the evidence of an extended orographic movement and a great period of erosion at the close of deposition of tlie Keweenaw series; and I am now of the opinion that the Keweenaw system should be considered as pi^-Cambnan. The correspondence in the position of the pr^ Grand Canon strata, separated from the Grand CaSon series Tv a grea unconformity, to the Huronian as described ^^0^ IS so striking that more than calling attention to it is LneceS The presence of organic remains does not necessarilv implv Uiat the strata are of Cambrian age except they show amLXd Cambrian facies; and unless this is the case I shouTd "orcon tend for a moment against well-proved stratigraphic evidence of greater age and marked structural breaks in the stiati" aphic succession. It may be asking too much for the period ifem to say that 12,000 feet of mechanical sediments and 4 000 fee of limestone accumulated in the Utah-Nevada basin while this erosion was taking place: but, if we look higher up n the ?00"ee?ofsir''^'"' 'ri'^^' "^ ^^"^'-^l ^^^^^''^' ^-- fin " tha? 200 .eet of Silurian and Devonian strata in the former is repre- TotJS^ Keweenaw system is here used to include the Keweenaw series of thp Lake Superior region, the Llauo series of Texas and the Chnnr «nH r! ^ n * 154 v. D. Walcott—Camhrlan System of North America. sentative of the 13,000 feet of limestone of the same formations in Nevada, and no unconformity, by any extensive erosion, is indicated ; and, again, the 9,000 feet of limestone of the Upper Cambrian and Lower Silurian (Ordovician) of the Central Nevada section is unrepresented in the Wasatch section of L, tah. 1 hese facts readily prepare us to believe that the hiatus between the Keweenaw and lJi)per Cambrian is fully equiva- lent to the period of the Lower and Middle Cambrian Another reason is that from the extended orographic move- ment preceding the erosion of the Cambrian, we should expect to hnd evidence of that erosion in the Cambrian of Utah and iNevada, but, as vet, none such is known Thus far the question of the existence of the Keweenaw sys- tem has been treated from a purely structural basis,* but in the course of my study of the distribution of the Cambrian faunas I have met with some facts that require an explanation and the most plausible one demands the existence of an ex- tended orographic movement, prior to the deposition of the Cambrian strata of the western side of the Continent, that raised a land area over the central portion of the Continent which T^\t p V° l^' PT^^ °^. *^^" beginning of the deposition of t P wS nf T """^ ^°™f ons, when it was depressed beneath o^er^ortionsof r '"' ^^^ ^PP- ^-brian strata deposited The facts demanding explanation are: 1st. The entire ab- sence as far as known to drite, of the Lower Cambrian or Para- H?;^Mn li"n '1'' ""^ ^'^^.^tlantic border: 2d. The absence of by the formations of the Keweenaw system • If we accept the view that the Keweenaw, Grand Canon, and Llano strata are outcrops of a system of strata of pre-Camhrian age that extended, in connection with the Huronian and Lau- rnHv'nf r'f >\^»^, P'-oJecting up through it, from the great body of Archean land on the north, southward over the area now occupied by the central portions of the Continent, or the Mississippi Ya ley and westward to the area occupied bv sedi- ments accumulated on the western side of the Keweenaw svs- tem of strata when the latter formed a land area, then the ex- planation asked is given. The pre-Keweenaw portion of this tZTl r^- """'i have been extensive as, in the Missouri aiea at fet. Lou,s and the Ozark Mountains, the Arcnean ap- pears beneath the Upper Cambrian ; and all ihe eastern slopes =»rir'*!?f •*^'" ^; C- pli'-J'^'jerlain gives a most excellent summary of the Keweenaw series and its strat.graphic position in vol. i, of the Geology of WisconsTn la the ection, on page 65, it is placed as a distinct system, Sting unconfora^ibly fornitv C'r" T'"^""'-'" turn, is separated from the L^urenti^n by 4 mS J j f V. D. Walcott-CunMun iiystan „f North America. 155 »ame i, tme in ti.e Black Uilis:;""T„^l"„f^;;S;. ™%t s &. 5i;i!!'iiiiiiii!!iiii^:: s ■■ , eastern belt is strongly imlcSibv the' J^po^ 1. ' ' •^"•'*' P'"^'^"^'' "^ "^^ faunas. L, Laurentia'n and ot Ir Vr LTu S ' b^^^ "' *^ ^^^'^^'^^ formation; C, Grand Canon formatio V v v ' Keweenaw; T, Llano land surface but now oonee'SeS b^tl^Vd^^po.^ts ' ''"'' "''^^'''^ *° '^'^^'^ '^^^^ existence Of these Archean areas with the U", -r Cumbrian deposits proves the early date of their elevation, .d tL^t the? 15(5 C. D. Wdlroft — CtDnh'lan System of Xorth AtneHca. were the shore line of the pre-Canibrian Keweenaw sea. What the eastern boundaries of this sea were, we do not now know, but the inference, from what is known of the Archean of the Appalachian system, is that portions of the latter were above the ocean during the depo- sition of the Keweenaw system. The traces we now have of this Ke- weenaw land point to its exteiision from the Lake Superior region soutii to Central Texas and westward to Central Northern Arizona. A glance at the map (fig. S) shows how far apart the relatively small exposures are; but, the great similarity of the sections and their position in relation to the Upner Cambrian that rests on the eroded surface of each visible area, points to a wide spread orographic movement that raised the entire cen- tral portion of the Continent and again depressed it at the termination of the period of erosion preceding the deposi- tion of the Upper Cambrian or Pots- dam sediments of the Upper Missis- sippi Valley, Central Texas and Ari- zona. The existence of such a land over the area mentioned, is shown by the sections we now know; and I think that, when the areas of Cambrian and Archean rocks in Missouri and also along the Southern Appalachian chain come to be studied with the view that such a land existed during the period of the deposition of the earlier deposits ■^ a g J . of the Cambrian system, evidence will •|l^g be forthcoming to show its former ^■i^Z presence over a large area. On the -i'lJs;^ "orth it probably joined the Archean |2|§.a continent and thus gave a greater ex- ^ j.3bc| tension of the pre-Cambrian continent ^ti|lf *^ ^^® south that, during the early '*'"'' I i [history of the Cambrian period, fur- '^-^ ished more or less of the sediments of the strata of the Lower and Middle Cambrian. The Archean boundaries of the Keweenaw sea continued after the elevation ^ 'i i at? =s ^i a K ^ " a 4> C " -2 3 M 2 j; y (' J). Wolroff~(',ti,ih,-;,ni St/Mfr7n of Novih A nwnco. ir.7 ./ o( I.Im« Iscvv.'ennvv liin.l. When Kowccnjiw land is spoken of I n'l.i- to that fonnwl of the strata of tlio Kciwoonavv systiim and t ic Ar(rli(>!in n.cks with vvliicli it was associatcid. He. ore tlio K(nv(u>naw hmd was dnprcsscd the MiddU; Cam- hnan fauna passed through or around the barriers hotween the Ath.ntic and western seas, and, as tl)e Keweenaw land was dia- !'PI"'-i]'"'M hen.'ath the waters, the Ui)per Cainhria!. fauna spread .)ver the area oeeuj.ied by it and l(>ft its record to aid lis 'u fixing the geologic date of the sui)niergen(!e < f the Kevvej-naw land and to ex|)]ain the absence of the l'ara(h)xides or Atlantic laiina in the earlv ( 'ambrian strata of the western sule of the Continent. In ti.e diiigrainatie section (fi<^ !>) J hnvo eiideayore.1 to show the relations of the Potsdam 'or Upper Carnbriaii to the Keweenaw land. 'I'he evidence of tli(! existcM.ce of the Keweenaw land i.s both alratigraphic a.nd paieontologie. ^IMiat life existe