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Canad~ ·
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QUOSlTIONAL. WI~ORV
OF·
MIDDLE ·CAMBRIAN TO LOWER ORDOVICIAN DEEP WATER SEDIMENTS, BAY OF IS~DS, WE~TERN NEWFOUNDL;.AND' t . . f
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~ Jac~.w .
Botsford, M.Sc.',,
A thesis submitted to the -school of 6raduate Studies in partial .fulfillment of the
requirements fpr the degree of Doctor of Philosophy·
Department of Earth· Sciences Memorial University of Newfoundland
'S_eptember '· 1987
St. John's . Newfoun<:Uand
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. AB5-TRACT'
The•Northern Head group is an upper ~dle Cambrian to Lower Ordovician hase-o~slope sediment apron! deposited ·downslope f~~m a
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shallow-water c~rbonate .platform, and now disposed in imbTicat~
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thrust slices within the Humber Arm Al~chthon, western
Newfoundland .. The group encompasses the upper Middle _Calnbrian to upper Tr~madoc Cooks Brook Formation and th~ upper Tremadoc to middle Arenig Middle Arm Point Formation. The discov~ry of nume~ous
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(ossil loc~liti~s has_facilitated the erection of a stratigraphic ·
. framework, embodying several cornHatable members. Thes.e ·,.
subdivisions reflect a natural change .in the depos'itional styl.e upward, from carbonate to shale-dominated.
The Cooks ·Brook is characterized by abundant platform-.derived, gravity-transported carbonate, and hemipe~agic·black sHale,
deposited in a. deep water, poorly-oxygenated environment. • Earliest sediments a~lated at the mou~hs of submarine canyons but were
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-buried by debris flow conglomerate sheets and carbonate sand
· turbidites from an active, upslope s~allow-water platform margin.
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Gravity transport of carbonate sharply diminished in earliest
·ordovician time but hemipelagic carbonate sedimentation p~rsisted
into late Tremadoc time.
The change to shale-dominate~ se.diments of the Middle Arm Point reflects a ne1oJ, low-relief margin upsl<;>pe. Hemipelagic shale wtts·
': accompanie~ by det~ital, wlndblown dolomite and bot~ were. _reworked b.y bottom currents. Diminished 1.nput of shelf and slope-derived orga!liC carbon, and more vigoro.us marine · circulat'ion, resulted in
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elevate~ Eh levels in rhe depos~t!onal enyironment which are ,c>
indicated by l j. a pro~ounced increase in bioturbation, and 2) a new
""suboxic" diagenetic regime, distinguished by widespread . precipitation of Mn-carbonate and barite, largely within the
stability field· of hematite. Condensed sedimentation characterizes· the ~iddle ~f. the Middle Arm Point, spanning th~ Tremadoc/Arenig b~undary. Shale. deposition contin~ed until t~e collapsing margin was
·buried' by sandstones of the overiylng Eagle Island forma'tion during·-·
middle Arenig.time.
The ·Northern Head group,and contemporaneous Cow Head Group were
both ·par~ ~!an active ca~bonate margin until the.Tremadoc. Their
depositional and paleoceanographic . c historie~ 0 diverged in late Tremadoc time, when a low-relief margin developed upslope from the '. Northern l{ead group while active carbonate sedimentation continued
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upslope ·from the Cow Hwad Group. This irregular carbonate margin morp"ology ls sugge.stive of a
ba~~ment-related
structural juncture---~---_,.
separating the two areas.
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··. _TABLE OF CONTENTS
Page
Abstra~t .. . . : . . · . . . ... . . . · .. ii
Acknowledgements .. , . .' .... . . ... ... . iv.
Table
of
Col\.tents ... ... ,, . . . ... vList of Fi'gures ... . . . ... . . . . ... :" ... . . . : . .... · xi
List of Tables . ,·, ... · ... : . . . ... · ... . . .... . . . .. x.iii List of ,Plates ... : . .. . . · ... ... .' ... . . xiv·
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Chapter 1: .niTRODUCTION .. .' . . . ... . . ... , . 11.·1 Introductory· remarks :·.-.-.•.. . . .... .- .. . . , .... '. 1
1. 2 Regional geologic setting . . . . ... . . .... . . • ... . . . . 2
1.3 Review of previous work: .. · .. . . .. : . . . ... . . ... 9
1.4 The study at::.ea ... · .... ... : . . . ... , 15
1. 5 Aims and scope of the study ... . . . \ ... ... •. ~ .... 16 Chapter 2: STRUCTURAL GEOLOGY.: ... ... . . . ... . 2. 1 Introduction , ... ... ~ ... . . . .... :-:-. 2. 2 Regional setting ... · ... ~ ... : . . . ... : . .. . 2. 3 Structural history ... . . ... . . . , ... . .... . '2.3_1 Synsedtmentary deformation ... ... .. . . . 2~3. 2 West-directed• structures ... . . . ... ·. Z.3.3 ·East-diretted foldf~g and thrustihg ... ~ ... . . 2.3.4 tate deformatio~: gentle warping and
18 18 19 19 19 22 26 near-vertical faulting ... ... . 2·. 3. 5 Structurally distinctive areas: the Rattler 28
· · Block ... : .... ' . . . : .... , .. . . , .. . 2. 4-Summary .... ... . . ... ... ~ ... . 2.5 Relationship with other structural elements . . . ... ... .
29 30 31 .
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'Chapter 3: STRATIGRAPHY . . . : . , .... , ... . . . ... .' .... . 3. 1 REGIONAL STRATIGRAPHIC NQHENCUTURE . .. ~ ·: ... .... . · .... . . . 3 .1.1 Introduction .. ; ... . . . ... . . ... ... . 3 .1.1. i Revision of the Curling Group ... . . .. . 3 .1.1-2 The Northern Head Group-... : ... : ... .
~ .1. 2 The Curling Group ... . . . ... . 3.1.2.1 Summerside Formation : ... . . . . ... .... .
• 3 .1. 2. 2 Irishtown Formation ... ! . ...... ... . 3. 1. 3 The .Northern Head Gr'<>up ... .' .... · ... . . . .' 3,. L·3 .1 Cooks Brook Format ton ... . . . . ... . 1 .1. 3. 2 Middle Arm ~oint For¥tion ... . . . ... · ... ..
3 .1. 4 Eagle Island Formation· . . . . : . . . . ... ... ... , 3. 2 SYSTEMATIC STRATIGRAPHY OF THE NORTHERN
33 33 33 38 40 43 43 45 48' 48 49 50
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HEAD GROUP ... · ... . . . : ... .. : . . . . 3. 2 .1 The lowermost Cooks Brook Formation . . . · ... .... . 3.2.2 The Halfway Point Member ... : . ... ; .... . 3. 2. 3 The Brakes Cove Member . . .... : . ... . 3.2.4 Upper Cambrian facies contrasts ... . . . .... . . . 3.2.5 DisC:ussion of the Cambrian ... . . . ... .
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54 58 62 65 68 '
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!~\LE OF CONTENTS (continued)
3.2.6 Lowenlost Ordovician conglomerate . . . : . . . ... 71
3.2. 7 Tremadoc ribbon 11me$tone interval . . . ... ... .' .. , 73
3. 2. '8 Woman Cove Member . . . , . . . . . . . . . . . . . . . 79
3. 2. 9 Parted .lime grainstone interval . . . .' . . . ·. 81
3. 2. 10 North
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Point Membet . . . . . . . . . . . . ... . . . . . . . . . . 823.2.11 UpperQost Mid~ Arm Point Member . . . ....... 84
3.2.12. The Eagle Island Formation . . . .' . . . 89
3. 3 PALEONTOLOGY AND BIOSTRATIGRAPHY . . . .' .. . . 93
3. 3. 1 Trilobites ........ : . . . ·. . . . . . . . . . . . . . . . . . . . . . 96
3. 3 .1..1 Cambrian trilobites . . . . . . , . . . 96
3.3.1.2 Ordovician·trilobites . . . 101
3.3.2'Grapt:olites .. : ....... , . . . . : . . . ..... .... 103
3. 3. 2. 1 Tremadoc ....... . . . .... . . :. . . . 103
. 3.3.2.2 Arenig ... .' . . . • ..... . . 109
3.4 SYSTEMATIC STRATIGRAPHY AND IHOSTRAT.IGRAPHY: ·• . DISCUSSION .... . ... ~ . . . : . . . 114
3.4.1 Cambrian . . . . .. . . • . . . 114
, !' 3.4.1.1 Contrast between the Halfway Pt. ~nd . Brakes Cove Members . . . ' .. 11~
3.4.1.2 Timing of conglomerate deposition . relative to the Cow Head Group . . . 115
3.4.2 Ordo'vician . . . .. . ........ : . . . .. 116
3.4.2.1 Biostratigraphic aspects .. . ...... . . 116
3.4.2.2 General stratigraphic aspects . . . 117
Chapter 4: SEDIMENTOLOGY Introduction ·and terminology . . . ...... . . . 4.1 SHALE .· . . . ...... . . . 121 123
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4~1.1 General description o( shale occurrence ..... . . . ... . 1244 .1.1. 1 Irishtown shale ..... . . . 124
4.1.1.2 Shales of the Cooks Brook Fro . . . .' ... . 124
4.1.1.3 Shales of the Middle Arm Poi~t Fm ...••..•••• 4.1.2 Shale-dominated lithologic associations . . . . 125 127 4.1.2.1 Interbedded black and green shale ..... . . . . 127 4.1.2.2 Red and green shale . . . .. . . · . . . ..
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4 .1'. 3 Red vs. green colouration in shale . . . .... . . . . 4 .1. 4 Relati6nship of lithologic associa't ions .> 11~2 146. within the Middle Arm Pt. Fm. • ... .' ... . 1574 .1. S Summary ... . .. . . • . . ... . . t . . . .. . . . 161
4. 2 CHERT . . . . ... . .. . . ... . . .
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2.1 Terminology . . . .... • . . . . 163 163 4. 2. 2 Bio~c componen_ts . . . / .. . . . 4. 2. 3 Principal types of chert ,•., . . . . 164 164 . 4. 2. 3.1 Silicified shale . . . . 1654.2.3.2 Siiicified·dolostone . . . . · . . . , . . . . 167
\ 4. 2.4 SUDlllary and .interpretation .... . . . . 168 4.3 CALCARENITE . . . ... . . , . . . ..... . . .... . 1731
4. 3.1 Composition . . . • . . . 173
4.3.2 Bedding style and l i thologic associations . . . . 175
4. 3. 2.1 Cooks Brook calcarenites . . . .. , . . . . 175 4.3.2.2 Middle Arm :Point calcarenites . . . . 177
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TABLE Q! CONTENTS (continued) •.
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· 4. 3. 3 Calcarenites: interpreted source and : . ..-.
~epositiona1 mechanisms . . . ..... : .. ·.· .... ~: ...• 177 4. 3. 3 .1 Postulated source ... , . .... ' ... • . . . ... .. · 177 . "' 4.3.3 .. 2 Depositiona·l mechanisms .... . . . ... 178 4. ~ LIME MUDSTONE
4. 4: 1· Introduc ti-op. and distribution . ·. :. · ...•... · .. : 181 4.4.2 Composition· .:: ............... : . ... ·- .. . . ... ;. 182' 4.4. 3 Possible odgin of li.De mudston·e units ... : .·.. 183 4. 5 DOLOMITE ... : ... : .... ·: ... ·.· •... 185. ·-·
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S. I' Dolom~te wit;hin the uppermost· Irish town ...• · ... 165 4.5.2 Dolomite.within c~lcarenites of the Cooks· Brook Formation ... . : ..... · ... : . . . ... 185 4 .·5. 3 'Middle .Arln Point: d.olomtte ... ... ....... -; . :. . . . . . .. . 186 ·,
,4.5.3:1 -W~man Cov~_Member ... . . · ... · ... ;···,· · 189 4.5.3.2 Upper.Hiddle Arm Point dolomites .. : ... 192 '··· 4. 5. 3, 3 Dolostone/limJ, mudstone coupl~ts .... .'. . . . . . 194 4.5:4 Dolomite:· Discussion] and Interpretation .. : .... .' .... '197
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4.5.4.1 Origin of thejdolomite .... : ... , ... 197 4. 5.4. 2 Po~t:ulated depositional mecnan~sms · . ·
of silty dolostone beds . : ... , . 199 4. 6 t:ONGLOMERATE .. ~· ... · ... .. I • • • • • • • : • • • • •• • • • ·• 201 4. 6.1 Conglomerates of the Halfway. Point Mbr. . ... ·. . . 201 4. 6. 2 Conglomerates· of the Brakes Cove Mbr. . ... .... .. ·. :. . 206 4. 6. 3 _,lJpper Cambrian conglomerates .. . . · .... . . ... . · ~ 10 .4.6.t..Basal Ordovician c'onglomerate ... . . . ... 210 4.6.5 Middle Arm Point F-ormation : ... .. 210 4. 6. 5.1 Lower c~nglomerates ·. ~ . . . ..... : ........ 211 4.6.6 .Granule conglomera~es of the Middle Arm Point ... 213 4.6.7 Int~rpreted.depositional mech~nisms ... ... -215 4. 6. ~ Further·. discussion of conglomerates: •
d~positional ~setting and composi;ional r variation ... : .... • . .' ... .. '... . . . . . . . 21 ~ 4.6.8.1 Signific~nce of compositional
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'vari.ation ... · .. ... .... ·: 219
4.6.~.2 Postulated relationship of the
Halfway P6int and Brak~s Cove Members ... 221 4.7 EAGLE ISlAND FORMATION . ... ... 225 4. 7.1 ."slump and injection interval" ... ... 225 4. 7. 2 ?Tuffaceous channels within the· basal
interval ... : ... · ... ... .' .... 233 4,7.3 OVerlying bedded conglomerate, sandstone
and siltstone ... : . .... ... : .. ~. : . .. 234 4. 7. 3.1 General .aspect :. : . . . .... -~ ... 234 4. 7. 3. 2 Composition . , ... : ... . : . ... .. 238 4.7.~.4 ,aleocurrent directions ... . . . ... 239 4. 7.4 Summary and interpretation ... ... ... 239.
4.8 SEDIMENTOLOGY: SUMMARY AND INTERPRETATION ... 244 4.8.1 Carbonate margin-to-basin transitions:
geners.l discussion . . . . . . . . . . . . 244 4.8.2 Northern Head Group: General depositional ·
setting ... . . . ... 225
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TABLE OF CONT~S (continued)
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4.8.3 Temporal
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~hanges.in depositional setting . . . Chapter 5: TRACE.FOSSILS AND THEIR STRATIGRAPHIC,,, .•
I • DISTRIBUTION .. ... ... . 5.1 Lower Cooks Brook interval ... · ... · ...•
5. 2 Upper. Cooks Brook interval ... :· ..... : ... .'..
260 260 266 5.3 Lower Middle Arm Point interval ... ... . 5. 4 Upper. Middle. Arm Point· interval ... · ... ... · .•... · .. 5. 5 Eagle Island Formation ... ... ... :.
5.6 Discussion'and int~rpretation ...•. ,_,. pp, • • • ~··. ~ • • 5. 6.1 Nomenclature ... ... : . .. · •... · ... .
269 273
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·in bioturbation levels .. . : ... ... ... . . 283 28'·
5.6:4 fmplied levels of oxygen in the
depositional ·environment ... ·.· .... : ... -... .
Chapter 6: DIAGENESIS ·
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6.1 OVERALL·DIACENETIC SEQUENCE .. ... ... . 289'
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6.1.1 Cementation by calci~e ... .. : ... : ... . 289 6 .1.1.1 Calc.ite cementation in claS-ts.
within conglomerate ... .... : ... . 6.1.1:2 Cementation within granule 290
conglomerate and calcarenite ... ... . 291 6. 1. 2 Dolomite ... ... .
6 .. 1. 2. 1 Dol'omi.te as a cement ... · ... .. 295 295 6.1.2.2 Dolomite as a replacement of grains
and intraclasts ... .... ·. · ... ... .. . 296 6.1.2.3 Dolomite grain overgrowth ... : ... . 6.1.2.4 Dolomite populations within the
Middle Arm Point Formation . : . .. ... ... . 6.1.3 Silicification ... ... -..
297 298 299 6.1 Ji _Preservation of hematlte .. 'r" . . . ... . . . .. . .. .. . : . . .
6.1.5 Barite authigenesis ... ... , .... .. . 6.1.6 Precipitation of pyrite ... ... . ,~ .• ... 6.1.6.1 Pyrite replacement of carbonate ... . •· .... .
302 302 303 304 6. l. 7 Minor authigenic phase: feldspar ... · .. .' '·-· .. . 6 .1.8 Overall dlagenet;.c sequence: summary ... .. . EVIDENCE FOR CONTRASTING DIAGENETIC STYLES UITHIN .
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THE NORTHERN HEAD ~ROUP ... .... ... . 313 6. 2 .1 ~tratigraphic variation of Mn ... ... . · .. · ... . 6.2.2 Nature of'Mn occurrence within the Middle
'313 Arm Point Formation ... . 313 6. 2. 2.1 ··Disseminated Mn ·carbonate within
shale ... : ... 316 6.2.2.2 Diagenetic Mn·carbonate horizons
within shale ... ...•.. · .... 6.? . . . . . . . . • 316 /6.2.2.3 Carbonate overgrowth within silty
dolostones ...... ... ... 322
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TABLE GF CONTENTS (continued)
6.2.3 Diagenetic precipitation:.of Mn/Fe-carbonates . . in the Northern Head Group: Interpretation .· . . . . ... 337"
6.2.4 Contrasting diagenetic settings within the
Northern .Head Group· . . . ~-... ; . . . . . . . . . 340
6. 2. 4·. 1 Coo}<s Brook "anoxic" diagenetic . setting . : . . . :· . . . 343
·6.2.4·.2 Middle Arr.:Point "suboxic" · diagenetic setting · .. . . ...... .' . . . .'. : . . . . 344
6. 2.4 :·'f Recent analogues of Mn-carbonate . · · precipitation ... . . ... . . ...•.. 345
6.2.5 Precipitation of Mn-carbonate in the '
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... : Middle Arm Point Formation.; . . . 3476.2.6 Potential preservation of early-precipitated diagenetic horizons . . . : . • . . . · . . . ... . 6 :'2. 7 .Distribution and significance of barite . . . ·. 6. 2. 7. 1 Origin pf b.ari te · . . . ' .. ..... . . <' .. 351 3'52 353 6.2.7.2 Postulated significance of barite distr.ibution . : . . . _ . . . . .. · .... , . . . . 6.2.8 Evidence froni pyrite precipitation ..... ......... . 6.2.9 tarly diagenesis of the Northern Head · 35.3 ·' 357 Group: Summary.:.······.· · · . · · · · " '··· 358
Chapter 7: SHALE GEOCHEMiSTRY 7. 1 Introduction .. : . . . . . . . . . . . . . . . ... . . . . . . . . . . . ..•. . . . 360
7. 2 Approach ·· . . . ..... · . . . . .... . . .. ..... . . · 361
7. 3 Major and trace element variation in the Northern Head Grou·p .. . . · . . . ..• . . . · ." .... ·. . . . . . 362
7.4 Elements associated with detrital silicate · minerals and clay mineratogy . . . . • . . . · .. .. 363
7.4 .1 Common mineralogical occurrefi'ce . . . -.-. . . ~ 363
~/ ... · 7 .4 .. 2 Matur~ty indices . . . ." . . . ......... : .· ..... : · .. 366
7. 4. 3 Cl:ay mineralogy · . . . .. -. ·: . . . . . . . . . . . . . . . 36 7 7.4.4 Stratigraphic variation . . . 367
7.4 .4.1 IriShtown shales . . . ,. . . ~ . 372
7.4.4.2 Group "A~ shales of the Northern . ,. Head Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 7 3 7.4.4.3 Gr~up "B" .shales ... · ... . . : . . . 373
7.4.4.4 Discussion . . . ... . . : ~75
/ ~ Trace elements ·associated with detr~tal heavy . minerals . . . ·. . . . . . . . . . . . . . . . . . . . . . . . . . . 380
7.5.-l'Discussion .. · ...... . . ...... . . .. .... 383
7.5.2 Summary . . . ... . . .... . . 385
~:6 Elements controlled by ~ulphide occurrence .... .... : . . . 385
7.7 Overall summary and interp~etation . . . .. .......... 339
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Chapter 8: SUMMARY_AND DISCUSSION 8.1 Depositional history of the Northern Head Group . . . 394a
.1.1 Cooks BrQOk Fnt. •(late Middle Cambrian to late Tre~doc) . . . .. . 3958.1.2 Middle Arm Point Formation (late Tre~adoc . ·.to Aren~g) . . . : .... . . 397
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• TA:BLE OF' CONTENTS ( cont;.inueI .d)
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. .Comparison-with the Cow Head Group ... ....... . ; .... ..... 400 8. 2. 1 Summar:t of the Cow Head Group . ; ........... , ... .. , .., 40$
8.2.2 Depositional hi~tory of the platform.arid ·
, eustatic events ........ ..... ... . ... : . : . ............ . 404 Contrast between the Northern Head'and Cow Head .
G'roup~ .. .' . ........ . . .. · ...... · ....... ...... .......... ·. . . . . . 406 Discussion and conclusions ... .......... ....... .... · . ..... 412 Additional evidence ... · ...... : ... · .... ...... ,. · ......... ... • ... 417· Specula-tion on ·implications. of. the model ........... · . ..... · 41S 8.6.1 Tec~nic implications ...... . . : ........•....... 418 8.6.2 Paleoceanographic implications ..... J ......... . .. . .... 423
8. 6. 2 .1 Further contra.sting aspects of the
Northern Head and Cow Head Groups .. , ... ,: ..... 423 8. 6. 2. 2 Discussion .............. ............ ..... . · 424 REFERENCES CITED .............. ....... .... \ .... ............ 433 Appendix
A:
Measu~ed seciioris (~ oversize sheets)Appendix. B: Discussion of measured sectiQfls .... .... ·: ... ....•.. 456 Appendix C: Fossil localities. and faunal assembl ages ... .. : . .. 465 Appendix D: Shale geochemical data ............. . · .. : .... · ·: .... .' . · 4 7 8 Appe:ndlx, E: Analytical- techniques . ...... , .... ... .' .... · ........... 495 Appendix F: Geological map(s) . (2 oversize sheets)
~Appendix G: Changing Eh under progressive shallow
burial conditions: a review· . · . ........ ..........
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LIST OF FIGURES
1-1 Regional geologic setting of the Northern Head Page Group ... : ..... . ...... .... ... ... .. . . . ...... . 1-2 Tee tono-strat.igraph ic setting .of the Northern Head 4 .
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Group ......... . . . ..... . . ..... . . . .. .. :· ... . ... : . . . 8
?--1 Structural aspects of the Bay of Islands study area .......... · .. ...... ....... , ... · . . . . 21
3-. 1 ~:~:;:!!~;d.~~~~~~~~~~~~.~~.~~~. ~~~tt~~- ... : . . ... :.
3-la Legend of lithologic symbols ...... . . . ... . . .. 3-2 sa'y of Islands: Northern Head Group (and adjacent • units), Generalized geology and location of 35 37•
sections . . . : ..... . . ..... . . .... . 3-3 .Northern Head Group: composite stratigraphic section . . . • . . . ..... 3-4 Type section: lowermost Cooks Brook Formation and 42 56 Ha 1 fway Point Membe-r . . . . 3-5 Type section: Brakes Cove Me111ber . . . . 3 · 6 Northern Head Gro\.lp: Corrc lation of the Cambrian 60 64. interval • • • • • • • • • • • • • • • • • • • • • • • • • • • •• 0 0 0 • • • • • 0 0 0 0 . . . . 3-7 Northern Head Group: CorrE>lation of the Ordovician ·intE>rval ....... . . . ...... . . ......... . . . . . . .. . . . ... 753-8 Type section: Woman Cove, North Arm Point Members . . . 78
3-9 Section illustrating uppermost Middle Arm Point 70 3-10 3-11 3-12 3-13 3-l4 Formation ......... . . . ............ . . . ..... ..... 87
Type section: E<~gle Island Formation · ... . . . ....... . . . . .... 91
Stratigraphic extent of measured sections .. . . . . .. ..... . 95'
Cambrian trilobite zonation scheme . . . . ...... . . . ..... 99
Tremadoc graptolite zonation scheme .·• :·.") . . . ... . . ..... 105
Arenig graptolite zon~tlon scheme ... , . . . ..... 111
4-1 4-2 cycles within interbedded black at)d green shale ... . . .... 140
Characteristic XRD reflection of hematite in red 4-3 4~4 '·- 5 '•- 6 '•- 7 shale ........... . . . ...... . . • . . . . ..... 153
Sedimentologic and diagenetic features associated with increasing Eh; Cape Split section .. . . . . . ..... 160
P'ostulated relationship of Halfway Point and Brakes Cove Members .... : . .. ... , .. . . . · .... . . . .. , . , 223
SUIIU'Dary of paleocurrent directions, Eagle Island Sandstone . . . .. . ....... . . .... . . 241
NQrthern Head Group:. Schematic summary of CambriAn deposltiona't setting ... :' . . . . 252
Northern Head Group: Schematic summary of Ordovician depositional setting ... , . . ... . . 258
S-1 Trace' fossil intel"{als and levels pf bioturbation through the Northern 1:iead Group . . . . .. ..... . . . .... 262
xi
·usr
uF FIGURES 1.. con_tinued) 6-16-2 6-3 6-4 6-5
Diagenetic sequences of the Northern Head Group,
schematic sUIMiary .... . . .... . . . Stratigraphic distribution .of Mn in shales of the
Northern Head Croup : . . .... ~ .. . . . ......... . . . Compositional variation in dolomite grain from
the \loman Cove Member . . . :. , ..
Progressive Fe-enrichment in~dolomi~es of the
uppermost Middle Arm Point . . . ..... . . . Variable overgrowth within dolostone bed,
310 ' 315 331 3 )l~
6-6 6-7.
6-8
6-9
uppermost Middle A:rm Point . . . . Schematic oxidation path of an anoxic water mass . . . . Contrasting diagenetic settings of the Northern
Head Croup ........... · . . . ......... . . ' ... . . . .. . Variation in dfssolved Mn within pore water of . modern pelagic sediments ... . . . ....... . Stratigraphic distribution of Ba within shnlcs
336 339 31•2 349 of the Northerrt Head Croup . . . .. ... . 3S_'J
7-1 Stratigraphic distribution of elements assoc!atPd 7-2
r 7-3
7-4
~
with detr·ital silicate and clay mineralogy . . . . Stratigraphic variation in "maturity indices"
through the Northern Head Grov.p . .' ..... . . .. .. . . . . Stratigraphic variation in clay mineralogy
through the Northern Head Group . ...... . . . .... ..... . Comparison of var-iation in "maturity index: Ml"-
between Northern Head Gr'oup and Lower Paleozoic
365 369 371
. .
7-5
,?
7-6I } -7
;
sequence of the Oslo region ... , ....... . . . ...... : . . . Stratigraphic variation of Cr, Zr, Y and V .. . . .... ... .. . Stratigraphic distribution of Zn, Pb, Cu and Ni ..... ... . Schematic summary of distinctive shale groups . . . . ..... . .
178
11l2 11l7 )<)1
I 8-1 Comparison of composite stratigraphic sections:
8-2 Northern Head and Cow Head Groups ........ . . . . . .
"'postulated depositional relationship of the
'·11·
.I/.. •·'-...,. .8-3 8-4 8-5
Northern Head and Cow Head Groups . . . . ..... .. . Cont!rasting regional structural style of the
Northern Head and Cow Head Groups ... , . . . .. .... . Deposition and resedlmentation of organic carbon-
rich mud in the slope setting .. . . . .... ... . Possible paleoceanographic implications of an
irregular margin morphology .. . . ... . . . . . . . .... .
/.[6
'· 22 t, ?8 /.))
G-1 Stages o.f organic matter oxidation ln anoxic
sediments ......... . ... · ... . . ..... . . . G-2 Schematic variation in dissolved species wllt:h
depth, in pe'lagic sediments . . . ....... . . . ... · . . . . )Qt,
)08
..
·. xULIST OF TABLES
· Page
• ~-- 1·2 · Evolution of stratigraphic interpretation and
nomenclature within the Bay of Islands area .......... . . 11 4-1 Organic carbon content;. of selectep black/green
sha~e couplets . . . 135
/ /
=~';:~·~~:';;~.~,~~. :::·~~.~~.~~,~~~~d.p~i'' ... . ... . 154
Eagle Island Sandstone: Paleocurrent directions ..... ... . 242 4-2
4-3
6-1 Dolomite: Summary of microprobe data 327 7-1 Comparison of major element composition of
Group "A" and "B" shales of the Middle Arm Point
and Eagle Island Formations ... '· . . ...... . . ....... ...... . 374 E-1 Precision and accuracy of major element
·analyses . . . .......... . . . .... .. . 496 E-2 Preci~ ion ~f trace· element analyses .... . . ....... : .. .. . 496 E-3 Precision of microprobe analyses .. . . . ... . . _ ..... . . 498 E-4 Precision of organic,carbon determination 499
.
.
-
0
xiii
LIST
· or
PLATES...
' Pllgf'l
4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10
4-11 4-12 4-13
Black _and black/green shales .... . . .. . . .. .... . . . Blaclc/green shales ... . ........... · .. . . .. . . . .... . . .... . Sha1e fi.thologies: blacl(/green, red and gr<'eD .. .... .' .. . Red and green shales_ •. ........... . . .•.. . .' .. .. : . .... . . . Chert, calcareni re lithologies · ................ . . ...... . Dolostone litholostes ... ._ ... .. ... . Dolostone li.tholC'0 ies (contd.) .. .... . . . . . . . . ....... . Dolostone lithologies (contd.) . . . .. ..... . .... . Conglomerate lithologies: Halfway Pt .. Mbr. . ·-·~ ...... . Conglomerate lithologies: Brakes Cove Mbr. ,
granule conglomerate . .. ......... . . . .... . . . . .. , ..... · ... . Eagle Island Sandstone: Features of the slump
and injection interval ..... . . .. . . .... . . ... . ...... . Features of the Eagle Island ~andstone . . . .... ....... : ..
Eagle Island Formation lithologies . . . . . . .. ....... . 130 133
1'·'·
148 170· 188 1.91 196 205 208
227 232 236
s :1 ·
5-2 5-3 5-4 5-5 5-6
Traces of the Lower Cook's Brook interval • • • • • • • • • • • 0 • • •
Traces of the Upper Cooks Brook 1nt€'rval 0 • • • 0 0 • • • • •• 0 • •
Traces of the Upper Cooks Bk. interval (contd) • • • 0 • • • 0 . Traces of the Middle Arm Point interval • • • 0 . 0 • • • • • ' • • • •
Traces of the Middle Arm Pt. interval (contd) ...
Traces of the Eagle Island Sandstone 0 • • • • • • • • • • • • •• • • • •
265 268 271 275 2J9 782
~-1
6-2 6-3 6-r, 6-5
Calcite and dolomite cement, dolomite £rains . . . . Dolomite (contd)-; silica; hE'matite; barite ... . . .... . Aspects of pyrite authisenesis . . . .... . · .. ... . Aspect' of diagenetic Mn-carbonate . . . .... . . . . . . ... . Asp.ects of diagenf'tic ~rbonate overgrowth . . . ....... .
./
?911 301
)()(,
3l'J
);){,
' "
4
xiv
CHAPTER
.!
• INTRODUCTION I' .
1.1 Introductory remarks
This is a geological investigation of an allochthonous, upper Middle Cambrian to Lower Ordoyic~an deep-water carbonate sequence, the Northern Head group, situated in the Bay of Islands area,
..
western Newfoundland.
Well-documented Lower Paleozoic deep-water carbonate sequences are relatively few. A long history of research.has focussed on one such s.equence in western Newfoundland, the Lower Paleozo~c Cow Head Group. This has yielded consider~ble insight into the internal
'
.stra~igraphy and depositional history, including styles of sedimentation, inferred relationship with the upslop~ carbonate platform, and changing paleoceanographic conditions.
Presumed equivalents to the south, in the Bay of Islands area, have been largely unstudied until now, but reflect a depositional history displaying similarities and important differences wi~h the Cow Head Group. This equivalent carbonate and shale-dominated interval in the Bay of Islands comprises the Cooks Brook and Middle Al~ Point Formations (Stevens, 196S),_which together are informally
termed i.ereln the. Northern Head group. Convention<ll wisdom has regarded che Northern Head group as the "distal· equivalent" of the Cow Head Group, but because of difficulty of access and relative structural complexity, this interpretation has not been seriously
. .
investigated prior to this study. An alternative model, of lateral equivalence And contrasting depositional history is presented here.
1
