HE STRATIGRAPHY AND SEDIMENTO OGY OF THE LATE PRECAMBRIAN ST. JOHN'S AND GIBBET HIU FORMATIONS
AND THE UPPER PART OF THE CONCEPTION GROUP IN THE TORBAY MAP-AREA, AVALON PENINSULA, N£WFOUNDI.AND
CENTRE FOR NEWFOUNDLAND STUDIES
TOTAL OF 10 PAGES ONLY MAY BE XEROXED
(Without Author's Permission)
f:UGEN Y. , H U
I
THE STRATIGRAPHY AND SEDIMENTOLOGY OF THE LATE PRECAMBRIAN ST. JOHN'S AND
GIBBETT HILL FORMATIONS AND THE UPPER PART OF THE CONCEPTION GROUP IN THE TORBAY MAP-AREA, AVALON PENINSULA,
NEWFOUNDLAND
by
~Eugene
Y,c.
HsuA thesis
submitted in partial fulfilment of the requirements for the degree of
Master of Science
Memorial University of Newfoundland August 1972
'
ABSTRACT
In the Torbay map-area, the St. John;s and Gibbett Hill Formations of the Cabot Group and the upper part of the Conception Group form a continuous and.:oonformable sequence of Late Hadrynian sedimentary rocks. The upper part of the
Conception Group consists of green-gray and variegated graywacke, siltstone, argillite, and volcanic tuff. The St. John~s Formation consists of six lithofacies and is divisible into two members;
namely, in ascending order, Middle Cove and Outer Cove Members.
Tne Middle Cove Member is represented by the laminated black shale and the Outer Cove Member by interbedded sandstone ~(or
siltstone) and black shale with locally developed volcanic tuff.
The Gibbett Hill Formation, overlying the St. John;s Formation, consists of green-gray arkosic sandstone, siltstone, argillite and volcanic tuffs. This formation is an equivalent of the lower member of the original Signal Hill Formation redefined in this thesis. The names ~Battery Member" and "Cuckold Member" are proposed for the middle and upper members of the original Signal Hill Formation.
The presence of volcanic tuffs in these units indicates intermittent volcanic activity during late Precambrian time.
Tentative correlation of the tuff beds in the Torbay map-area suggests a diachronous relationship of the boundary between the Gibbett Hill and Signal Hill Formations.
Aspidella terranovica Billings 1872 and associated surface markings in the Outer Cove Member of the St. John's Formation are considered to be inorganic sedimentary structures such as load casts and gas- or water-escape structure •.•
A model of the depositional environments of part of the Cabot Group and the upper part of the Conception Group is proposed.
The upper part of the Conception Group was formed as turbidites in deep marine environment. The Middle Cove Member of the St.
John's Formation was deposited in a prodelta and the Outer Cove Member in distal delta front. The Gibbett Hill Formation, transitional to subaerial deposition, was formed in a proximal delta front.
The source area for these units probably lies to the north of the Torbay map-area.
TABLE OF CONTENTS
ABSTRACT
...
CHAPTER 1: INTRODUCTION
...
Location and Access ••••••••••••••.••••••••••••••.•
Previous Work ...•...
Present Study Acknowledgment
• • • t • • t • • • • a • • o • t • • t • • t t • t , , , , , , ,. • ,-•
...
CHAPTER II: STRATIGRAPHY
...
...
,... .
Introduction
Harbour Main Group
...
Name
...
Distribution, Correlation, and Thickness .•••••
Boundary Relationships Holyrood Plutonic Series
Name and Distribution
... . . . .
... ... . . . .
Boundary Relationships and Age
...
Conception Group
...
Name •• •••••••••••••••••••••••••••••••••••••••
Distribution, Correlation, and Thickness ••••••
Boundary Relationships
...
St. John's Formation ••••••••••••••••••••••••••••.
Name •••••••••••••••••••••••••••••••••••••••••
Distribution, Correlation, and Thickness ••••••
Boundary Relationships
...
Subdivision of the St. John's Formation •••••••
Signal Hill Formation
...
Name •••••••••••••••••••••••••••••••••••••••••
Distribution, Correlation, and Thickness •.•
Boundary Relationships
...
Revision of Stratigraphic Boundary at
Ferry land
...
Redefinition of the Signal Hill Formation •••.•
Correlation of Volcanic Tuff •••••.•••••••.•
CHAPTER III: LITHOLOGICAL UNITS AND THEIR CHRACTERISTICS.
Introduction ... · · · Conception Group ... · · · • · · · Graywacke •••••••.••••.•••••.••.••••••••• • · • • • •
Mineralogical Composition .••...••••••. · • • Sedimentary Structures ••••.•.••••••••.••..
s
i 1 tStone ... · · · Argillite ... · . · • · · · Tuff ....•......•... · · · • · · ·Page
1 1 1 2 4 5 5 5 5 5 7 7 7 8 8 8 8 9 9 9 9 10 10 10 10 11 11 12 12 15 17 17 18 18 18 23 25 25 26
St. John! s Formation •••••••••••••••••••••••••••••
Introduction , , .. , ... , . , , . " ~' .... , .. , , , , , ... , . , . , Facies A - Mudstone ••••••••••••••••••••••••••••
Sedimentary Structures •••••••••••••••••••••
Facies B- Laminated Black Shale •••••••••••••••
Mineralogical Composition ••••••••••••••••••
Sedimentary Structures ••••••••••••••••••••••
Facies C- Interbedded Sandstone and Shale ••••••
Sedimentary Structures •••••••••••••••••••••
Facies D- Medium-bedded Sandstone •••••••••••••
Mineralogical Composition ••••••••••••••••••
Sedimentary Structures •••••••••••••••••••••
Facies E- Channel Sandstone •••••••••••••••••••
Mineralogical Composition ••••••••••••••••••
Sedimentary Structures ••••••••••••••••••••
Facies F- Volcanic Tuff ••••••••••••••••••••••
Mineralogical Composition ••••••••••••••••••
Sedimentary Structures ••••••••••••••••••.••
Gibbett Hill Formation •••••••••••••••••••••••••••••
Introduction ... . Facies A -Conglomerate •••.•••••••••••••••••••
Sedigentary Structures •••••••••••••••••••••
Facies Bg- Green-gray Sandstone •••••••••••••••
Mineralogical Composition ••••••••••••••••••
Sedimentary Structures •••••••••••••••••••••
Facies C -Siltstone and Argillite •••••••••.••
Sedi~entary Structures ••••••••••••••••••.••
Facies Dq- Volcanic Tuff ••••••••••••••••••••••
Mineralogical Composition ••••••••••••••••••
Sedimentary Structures •••••••••••••••••••••
CHAPTER Iv·:· PROBLEMATIC MARKINGS •••••••••••••••• • •• • ••• • Previous work ... · Present Study ... · Occurrence and Mode of Preservation •••••••••.••
Preferred Orientation ••••••••••••••••••••.•••••
Morphology and Internal Structure ••••••••••••••
Type 1 •...••..•..•...•..•... · • • · · · · • • · · · Type 2 .•••..•••••••••••.•••••..•. • • · .• · • · · · Type 3 · •••••.•••.••••.••..•••••. • • · • · • · • • · · · Type 4 ••.•••••..••.•••...•.•••.. · · • • • · · • · · • Type 5 •.•••..•••.•.•.•.• · • • • · · · • • • · · · • · • · Type 6 •.•.•.•.••••.•.•.••••••. · • • · • • • · • · · • ·
Origin of Problematic Markings •••••••••••••••••
Conclusion ..... · · · · • · · · • · · · CHAPTER V: DISCUSSION ••••••••••• • •. • • • • • • • • • • • • • • • • • • • • • Introduction ... · • · • · · ·
Page 27 27 27 27 30 30 33 35 35 39 39 40 42 42 42 45 45 47 48 48 48 49 49
so
51 53 53 56 56 57 58 58 59 61 61 63 63 65 65 66 66 67 67 68 70 70
'
Depositional Environment ••••••••••••••••••••••••••
Conception Group •••••••••••••••••••••••••••
Deltaic Sequence •••••••••••••••••••••••••••••
....
....
St. John's Formation
...
Facies A Facies B
Facies C Facies D Facies E
Transition Zone ••••••••••••••••••
Prodelta ... . Distal Delta Front ••••••••••••••• Subtidal Flat ••••••.••••••••••••••
Tidal Channel •••••••••••••••••••• Gibbett Hill Formation •••••••••••••••••••••••••••
Flow Condition ... . Proximal Delta Front •••••••••••••••
. ... .
Provenance •••••••••••••••••••••••
. . . . . . . . . . . . . . . . . .
Volccmic Activity ... . Geological History ••••••••••••••••••••••••••••••••••••
REFERENCES
...
Page
72 72
73 73 73 7S 75 76 77 78 78 78 79 80 81 83
'
LIST OF ILLUSI'RATIOOS TABLES
Page Table l.. Table of Ebrna.tiCilS • • • . • . • . • • • . • • • • • . . . • . . . • • . . • • • • • 6 Table 2. Redefinition of the cabot Group • • • • • • • • • • • • • • • • • • • • • • • • • 14 Table 3. ltJdal. analysis of the sandstones of Conception
Group. St. Jolm 1 s Forna.tian, and Gibbett Hill
Ebnnatioo. . • • • . . . • . . • • . • • . . • . . . • . . • . . . 19 Table 4. S1:1marized characteristics of lithological facies
of tiE St. Jolul' s Ebnnation. . . . • . . • . . . • . . . 28 Table 5. Chemical analysis of black shale fran the Mi<Xlle
Cove Mellber, south shore of calvert Bay, Ferry land. • • • • • • • • • • 31 Table 6. Mineralogical CX~~p>Sition of black shale fmn
Mi.tHle OJve M3nber, south slx>re of calvert Bay. • • • • • • • • • • • • • • 32 Table 7. Slmnarized characteristics of lithological facies
of the Gibbett Hill FOrmation. ••••.•••••••.•••••••••••••••••• 48a Table 8. Stmnaiy of references to Aspidella terranovica
Billings 1972. ••••••••••••••••••••••••••••••••••••••••••••••• 60 Table 9. Depositialal envirorments of the lithofacies of
the St. John's E'oma.tion. . . . • . . . 7 4
FIGURES
Fig. 1-1. Geological map of central and eastern Avalon
Peninsula,~ ••••••••••••••••••••••••••••••••••••••
Fig. 2-1. Geological map of Ferry land area, Newfoundland •••••••••
Fig. 3-1. Detrital a:uposition of sandstones fran the St.
JO}m IS a00 Gibbett Hill Fonnations and the upper part
in pocket in iX)Cket
of tlle CDn<Eptim Grollp. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 22a Fig. 3-2. Stratigraphic distribution and tentative correlation
of the volcanic tuffs in the St. Jolm 1S and Gibbett Hill POnmatians in the Tbrbay map-area • .••••••••••..••.••••.••...•
Fig. 3-3. Stratigrcqily and lithofacies of the St. Jolm1S
Ebnnatioo.. • ..•... · · ·
in pocket in pocket
,. 1 •• l ,.r·.·
,.f. r.T
·•1'' .,.
.··.::.":.
11. • j . . . ,
·::!I 'i
·;-,
,.. , ··
'·····
1:•1
Fig. 3-4. Character of sltmp overfolds and sandstone relics in llalogranec>\lS slurrp l:JeCl. • • • • ••••••••••••••••••••••••• , •••••
Fig. 3-5. Scx:lur-and-fill structures in facies
c ... .
Fig. 3-6. Vertical profile of a sinple channel at Outer Cove.
. ...
Fig. 3-7. Vertical profile of channel-fill detx>sit at Bay
Bulls. . ...•...
Fig. 3-8. Graded l:JeCl of sandstone in the Gibbett Hill
Ebnna.tiOil. • . • • • • • • . . • • • . • • • . • • • • • . • • • • • • • . • . • • • • • • • • • . • . •.•••
Fig. 4-1. Preferred orientatioo of the elliptical markings and their relationship of the strike of sedinentaiy
Page 34 38 44 44 54
beds and Dold axis. ••••••.•••.••••.•••••••••.•••.•••••••••••• 62 Fig. 4-2. Teminology of the mtphological features of the
surfac::e narkin.gs. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 62 Fig. 4-3. Internal structure of the surface na.rkin.gs in the
St. John's For.matian • ••••••••••••••••••••••••••••••••••••••••
Fig. 5-l. lblel of the depositional envirorments in the upper part of the Conception Group and the cabot
GiolJI?. • ••••••••••••••••••••••••••••••••••••••••••••••••••••••
64
71
•'·.
· .
. 1:::11 . '
PrATES
Plate 3-1. Parallel-bedded sed:i.nentary rocks o:::· the Conception
Group
...
Plate 3-2. Repititive graded beds of the Conception Group
....
Plate 3-3. Close-up of Fig. 3-2 showing cross laminations
m
gz-aywac]{e • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • ••••••••••••••
Plate 3-4. Flute markings on the base of graywacke •••••••••••
Plate 3-5. Photanicrographic; biirodal distribution of the
detrital grains in graywaCke ···~~·~···
Plate 3-6. Photanicrograph of the tuffaceous graywacke of the Conc.=ptiOil Grol.lp • • • • • • • • • • • • • • • • • • • • ••••••••••• ' • • • • • • • • •
Plate 3-7. Photanicrograph of the putplish red graywacke of the Conceptioo Gro\.1!) • • • • • • • • • • • • • • • , • • • • , • • • • • • • • • • • • • • • • ••••
Plate 3-8.
Group
Plate 3-9.
Group Plate 3-10.
mation
Photomicrograph of graywacke of the Conception
...
Photanicrograph of volcanic tuff of the Conception
...
Graded beds in facies A of the St. John's For-
...
Plate 3-11. Facies B of the Middle Cove MaJtber of the St.
John. r s E'Oilllation •••••••.•••••••••••••••••••••••••••••••••
Plate 3-12. Facies C of the OUter Cove Mantler of the St.
John I s FOilllatiOil • • • • • • • . • • • • • • • • • • • • •••••••••••••••••••••
Plate 3-13. Solitaiy set of ripple-drift cross laminations in facies C of the St. John's Formation ••••••••••••••••••
Plate 3-14. Scour-and-fill structute in facies C of the St.
Jolm 1 s FonnatiOll . . . · · · • · · · • • · · · · • · · · Plate 3-15. Ripple marks
m
facies C of the St. John'sFonnation ...•...•... · · · Plate 3-16. Rippled sandstone and lenticular bedding in facies
c
of the St. John's Fbrmation ••••••••••••••••••••••••••••Page
87 87 88 88 89 89 90 90 91 91 92 92 93
93
94
94
Page Plate 3-17. Flow rolls, psellio-ncxlules and cross lamination
in facies C of the St. John's Formation ••••••••••••••••• 95 Plate 3-18. Facies D of the St. John's Formation • • • • • • • • • • • • 95 Plate 3-19. Cosets of ripple-drift cross l.cmdnations in facies
D of the St. John's Formation • • • • • • • • • • • • • • • • • • • • • • • • • • • 96 Plate 3-20. Interference ripple narks in facies D of the St.
Jclm' s Fonnation . . . . . . 96 Plate 3-21. Ribbon-like sandstone body in facies C of the.
St. Johrl's Forrna.tion •••••••••••••••••••••••••••••••••••• 97 Plate 3-22. Facies E of the St. John's Formation •••••••••••• 97 Plate 3-23. Large scale trough cross beddings in the channel
filling sandstone in the St. John's Formation • • • • • • • • • • • 98 Plate 3-24. Facies E of the St. John's Fomatiori ·••• • • • • • . • • • 98 Plate 3-25. Coset of large scale cross bedding in the channel-
filling sandstone in Fig. 3-24 •••••••••••••••••••••••••• 99 Plate 3-26. Photanicrograph of the typical very fine-grained
sandstone of the St. John's Formation • • • • • • • • • • • • • • • • • • 99 Plate 3-27. Photomicrograph; quartzitic texture of the coarse-
grained sandstone of facies E of the St. John's Formation. 100 Plate 3-28. Photanicrograph of volcanic tuff in facies C of
i:lle St. Jolm 's E'oiina.tion •••••••••••••••••••••••••••••••
Plate 3-29. Photanicrograph of tuffaceous sandstone in facies
c
of the St. John's Fonnation ••..••••••••••••••••••••••Plate 3-30. Photanicrograph of mi.crograded bedding in volcanic tuff of the St. John's Formation ••••••••••••••
Plate 3-31. Photomicrograph of the tuffaceous sa'ldstone in facies A of the St. John's Formation ••••••••••••••••.••
Plate 3-32. Photomicrograph of the tuffaceous sandstone in facies A of the St. John's Formation •••••••••••••••••••
Plate 3-33. Photomicrograph of the tuffaceous sandstone in facies A of the St. John's Formation •••••••••..••••••••
Plate 3-34. Conglonerate in the Gibbett Hill Formation •••••
100 101 101 102 102 103 103
d:t.f_':
,J,j;'.'
· .. · ..
'. . ; :i .!.'.
Plate 3-35. Parallel bedding and scour-and-fill structures with cross stratificatioo in the sandy conglarerates of the ~tt Hill Formation ••••••••••••••••••••••••••
Plate 3-36. Large scale tabular cross bedding in the coarse- grained sandstone of the Gibbett Hill Formation ••••••••
Plate 3-37. Cosets of small scale trough cross lamination in the sandstone of the Gibbett Hill Formation •••••••••
Plate 3-38. Cosets of ripple-drift cross lamination in the very fine-grained sandstone of the Gibbett Hill
Fbrmation
Plate 3-39. I.oad casts at the base of coarse-grained
sam-
stone of the Gibbett Hill Formation ••••••••••••••••••••
Plate 3-40. Convolute bedding in the sandstone of the
GiblJett Hill Fbnna:tion •••••••••••••••••••• " ••••••••••••
Plate 3-41. Oscillatory (sj1Imetrical) ripple marks in the very fine-grained sandstone of the Gibbett Hill For- nation I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
Plate 3-42. Mlli cracks in black shale of the GiblJett Hill
Fo~tion ••••••••••••••••••••••••••••••••••••••••••••••
Plate 3-43. Volcanic tuff of the Gibbett Hill Fbnnation, shc:Ming parallel lamination and cross lamination •••••••
Plate 3-44. Tabular cross lamination in volcanic tuff of the GiblJett Hill Formatioo •••••••••••••••••••••••••••••••••
Plate 3-45. Diagenetic white bands :in the volcanic tuff of the GiblJett Hill :Fonnatioo •••••••••••••••••••••••••••••
Plate 3-46. Photanicrograph of quartzitic texture :in sand- stone of the Gibbett Hill Fonnation ••••••••••••••••••••
Plate 3-47. Photanicrograph of laminated volcanic tuff of the Gibbett Hill Fbtmation •••••••••••••••••••••••••••••
Plate 3-48. Photomicrograph of negaccystals of diagenetic calcite (?) in the volcanic tuff of the Gibbett Hill Formation ••••••••••••••••••••••••••••••••••••••••••••••
Plate 3-49. Photomicrograph of glass shaJ:ds in the volcanic tuff of the Gibbett Hill Formation •••••••••••••••••••••
t
!Page
104
104
105
105
106
106
107
107
108
108
109
109
110
110 111
i .
l ,~ '
. i .. ··.
Page Plate 3-50. Photanicrograph of the tuffaceous sandstone of
the Gibbett Hill FOrmation ••••••••••••••••••••••••••••• 111 Plate 4-1. Type 1 and Type 5 narkings on the top surface of
black shale of the St. Jolm 's FOrmation •••••••••.••••••
Plate 4-2. Type 2 markings on the lCMer surface of sandstone and on the top surface of black shale of the St. John's
112
E'ormation. • • • • • • • • • • . • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 112 Plate 4-3. Type 3 narkings en the lCMer surface of sandstone
of the St. John's Formation •••••••••.•••••••••••••••••• 113 Plate 4-4. Type 3 markings on the looer surface of sandstone
of the St. John's Formation...... 113 Plate 4-5. Type 4 narkings on the lCMer surface of sandstone
of the St. John's FOrmation... 114 Plate 4-6. Type 4 markings on the top surface of black shale
of the St. John's FOrmation ••••••••••••••••••••.••••••• 114 Plate 4-7. Type 1 and Type 5 narkings on the l~r surface of
sandstone of the St. John's Formation • • • • • • • • • • • • • • • • • • 115 Plate 4-8. The largest Type 5 narking on the top surface of
black shale of the St. John's FOrmaticn • • • • • • • • • • • • • • • • 115 Plate 4-9. Type 5 narkings on the 1~r surface of sandstone
of the St. Jolm's Formation •••••••••••••••••••••••••••• 116 Plate 4-10. Type 6 narking on the top surface of black shale
of the St. John's Formation ••••••••••••••••••• ·• • • • • • • • • 116
'
- 1 -
CHAPTER I INTRODUCTION Location and Access
The thesis area centers around st. John's, Newfoundland and extends 48 miles southward to Ferryland, and 7 miles north- ward to Torbay (Fig.l·l). Most of the coastal exposures are easily accessible by paved highways, grz sl roads, and trails.
A boat was used in the examination of the coastal section between Middle Cove and Outer Cove. Inland exposures are poor and
traversing is difficult because of the dense bushes, bogs, and rough terrane.
Previous Work
The first report and map on the geology of Newfoundland was by J. B. Jukes (1843). In that report for the Newfoundland Government, the rocks of Avalon Peninsula were named and classified as follow:
a. Belle Isle shale and gritstone Upper Slate Formation
b. Variegated slates a. Signal Hill sandstones Lower Slate Formation
b. St. John's slate'
As a result of their field work from 1864 to 1880, Alexander Murray and J. P. Howley published a report and a detailed geolo- gical map of the Avalon Peninsula in 1881. In the report the rocks of the Avalon Peninsula were divided, in ascending order, into
II a, , c, d, e, f, an g b d II d' ' , ~v~s~ons.
.,.1
• I
- 2 -
Walcott (1899) proposed the name "Avalon Terrane" to
include the formations lying between the basal beds of the Cambrian System and the Archean gneisses of Newfoundland, and used the
names Signal Hill, Momable, Conception, and Torbay for these formations.
Rnse (1952) completed mapping of the Torbay map-area for the Geological Survey of Canada and proposed four main rock groups
(Table 1) •
In 1968, Singh undertook the first detailed petrological study of the Signal Hill and the Blackhead Formations. He concluded that the Signal Hill and Blackhead Formations are derived from a similiar source area and represent shallow marine, fluvial, and alluvial plain sediments (Singh, 1969).
Brueckner (1969) summarized the geology of the Avalon Peninsula. He concluded that the Cabot Group represents a sequence of deltaic sediments in which the St. John's Formation formed the bottomset beds, the Signal Hill Formation the foreset beds, and the Blackhead Formation the topset beds.
Present Study
This thesis was originally intended as a study of the problematic fossils known as Aspidella terranovica Billings 1872, exposed in the St. John's Formation.
During the preliminary field work at Ferryland in the summer of 1967, the author discovered volcanic tuffs in the St.
John's and Signal Hill Formations. The contact between the Con-
- 3 -
ception Group and St. John's Formation was found to be transi- tional rather than disconformable as reported by Rose in 1952.
In order to ascertain the distribution of volcanic tuffs and the geometry of the St. John's Formation, the author decided to extend the study area.
The major part of the field program was carried out in the summer of 1970. Air photos at a scale of one inch to 1,420 feet and topographic map at a scale of 1: 50,000 were used to record field data. The geological map by Rose (1952) was the chief source of reference.
Areas selected for detailed study were Outer Cove to Middle Cove, Bay Bulls, Mobile Bay, Calvert Bay, and Ferryland.
Aerial photographs were used in estimating the stratigraphic thickness of the St. John's Formation as measurements in the
field were hampered by discontinuous exposures and by the presence of small scale folds and faults.
Nineteen thin sections of sandstone and siltstone were selected for modal analysis of the mineralogical composition and about 700 to 1,000 grains in each thin section were counted with a Swift Point Counter.
The qualitative mineralogical composition of the volcanic tuffs and black shale was determined by x-ray diffraction. Chemical analysis of the major inorganic elements in one black shale specimen wae carried out.by the Geochemistry Laboratory of the Geological Survey of Canada.
The present study is essentially a description and an
- 4 -
interpretation of lithofacies and depositional environments of the upper part of the Conception Group, the St. John's Formation, and the lower member of the Signal Hill Formation. A relationship between time and lithostratigraphic boundaries using volcanic tuffs as key beds is proposed.
Acknowledgments
The author wishes to express his sincere thanks to Dr.
A.F. King, under whose supervision the thesis was written.
Financial assistance for this work was supplied by grants from the Geological Survey of Canada to Dr. R. D. Hughes, National Research Council of Canada to Dr. W. D. Brueckner (grant No.
A-884) and Dr. A. F. King (grant No. A-7052), and a Fellowship from the Memorial University of Newfoundland.
The author is particularly grateful to Dr. E. R. W.
Neale and Dr.
v. s.
Papezik for their encouragement.Thanks are due to Dr.
w.
D. Brueckner and Prof. M. M.Anderson for their valuable discussions. The author is also indebted to Messrs. G.
s.
Bartlett, C. C. K. Fong, and J. M.Fleming who read the manuscript and made helpful comments. The assistance of Mr. K. Burne in drafting, Mr. F. Thornhill in the preparation of thin sections, and Mr.
w.
Marsh in photography are gratefully acknowledged •. . '
'~~i-i Thanks are also extended to the Geochemistry Laboratory
. ::'~'?~.
::[;;~
of the Geological Survey of Canada for the chemical analysis of:·•o::·::.
';:··:~
s
black shale •.. ,;.
- 5 -
CHAPTER II STRATIGRAPHY Introduction
The eastern part of the Avalon Peninsula is underlain by four main rock units of presumed Hadrynian age. They are, in ascending order, Harbour Main Group, Holyrood Plutonic Series, Conception Group, and Cabot Group. Table I illustrates the strati- graphic sequences in the eastern Avalon Peninsula and their pre- sumed stratigraphic equivalents in the Whitbourne map-area. The general stratigraphic nomenclature of Rose (1952) and McCartney
(1967) was used in the field but a relevent revision of the Cabot Group is proposed.
Harbour Main Group Name
The Harbour Main Group is the oldest exposed unit in the map-area and is composed of mainly basic and acidic volcanic rocks and intercalated sedimentary rocks.
These rocks correspond to map units "a and b" of Murray and Howley (1881-b) and were first named "Avondale Volcanics" by Buddington (1919) after their type locality. Howell (1925) renamed them "Harbour Main Volcanics" as the name "Avondale" had previously been used elsewhere. Rose (1952) renamed them "Harbour Main Group".
Distribution, Correlation, and Thickness
The Harbour Main Group is distributed around the Holyrood Granite, and together they form the core of the Avalon PGninsula.
Table 1. Table of Formations •
. ,
Era, Period, Whitbourne Map-area Tor bay Map-area
or Epoch McCartney, 1967 Rose, 1952 Hsu, 1972
Hodgewater Group Cabot Group Cabot Group
Snows Pond Formation Blackhead Formation Blackhead Forma tic:..'l Whiteway Formation Signal Hill Formation Signal Hill Formation
Upper Member Cuckold Member
Middle Member Battery Member
Halls Town Formation Lower Member Gibbett Hi11 Formation
J:: ItS Carbonear
·r-1 Formation St. John's Formation St. John's Formation
~ J-1 ItS
Outer Cove Member
0 Middle Cove Member
Q)
p.. J-1
Transition Disconformity Transition
Conception Group Conception Group Conception Group Intrusive Contact
i.
Holyrood Plut~nic Series Holyrood Batholith Holyrood Plutonic Series Unconformity
Harbour Main Group Harbour Main Group Harbour Main Group
- 7 -
The base of this unit is unexposed and the stratigraphic thickness is at least 6,000 feet (McCartney, 1967). Volcanic rocks in the Burin Peninsula may be stratigraphic equivalents (McCartney, 1967).
Boundary Relationships
Rose (1952) stated that the Harbour Main Group in the Torbay map-area is unconformably overlain by the Conception Group at several localities. However, beds similar in lithology to the Conception Group occur with the Harbour Main Group and the time interval represented by the contact between the two groups is of minor significance. Brueckner (1969, p. 133) states that a confor- mable relationship exists between the Harbour Main and Conception Groups in the eastern Avalon Peninsula but an unconformable one in the western Avalon Peninsula.
Such ambiguous relationships, together with other evidence, lead Hughes (1970) and Hughes and Brueckner (1971) to propose
that the Harbour Main and Conception Groups were actually penecon- temporaneous facies.
The Harbour Main Group is intruded by granite of the
Holyrood Plutonic Series; it is unconformably overlain by Cambrian sediments at the southeastern shore of Conception Bay.
Holyrood Plutonic Series Name and Distribution
Granite and marginal facies of quartz monzonite and quartz diorite occurring in central Avalon Peninsula were named "Holy-
'
. '•
·~ '
. )
. !
- 8 -
rood Batholith" by Rose (1952) and "Holyrood Plutonic Series"
by McCartney (1967).
Boundary Relationships and Age
The Holyrood Granite intrudes the Harbour Main Group.
Although Rose (1952) reported that the Holyrood granite intruded the lower part of the Concept~on Group, field relationships of the granite with the upper part of the Conception Group are not entirely clear. McCartney (1967) stated that in the Whitbourne map-area the intrusive relationship is uncertain.
The granite has been dated by the rubidium/strontium isochron as 574
±
11 million year old (McCartney, et al., 1966).Both the granite and the Harbour Main Group are uncon- formably overlain by the Cambrian sediments.
Conception Group Name
The rocks in this unit correspond to the map units ~'b and c" of Murray and Howley (1881-a and 1881-b). Walcott (1899) used the name 11Conception Slate" for the predominantly green and greenish gray rocks and "Torbay Slate" for the variegated beds. Both
"Torbay Slate" and "Conception Slate" were included in the
"Conception Group" named by Rose (1952) •
Distribution, Correlation, and Thickness
The extent of the Conception Group is shown in Fig. 1-1.
This group was correlated by Hayes (1948) and Christie (1950) with the Connecting Point Group in the Bonavista area and by McCartney
(1967) with the Conception Group in the Wh.itbourne map-area. It
.,.
I
l
- 9 -
has an exposed thickness of some 8,000 feet in the Torbay map- area (Rose, 1952).
Boundary Relationships
The Conception Group lies unconformably on the Harbour Main Group in the western part of the Avalon Peninsula. A conformable relationship exists between these two groups in the eastern part of the Avalon Peninsula (Brueckner, 1969).
The present study indicates a transitional relationship between the St. John~s Formation and the underlying Conception Group rather than a disconformity as reported by Rose (1952).
St. John's Formation Name
This unit was originally named by Jukes (1843) as "St.
John's Slate" which was renamed "Aspidella Slates" by Murray and Howley (1881-a). Walcott (1899) used the name "Momable Slates", later renamed "St. John's Formation" by Rose (1952).
Distribution, Correlation and Thickness
The distribution of the St. John's Formation (Fig. 1-1) is very extensive: it extends southerly from Torbay to Aquaforte Harbour, on the north shore of Trepassey Bay (Misra, 1969; Koh, 1969), and on the east shore of St. Mary's Bay (Brueckner, personal communication, 1969). The st. John's Formation was coDrelated by McCartney (1967) with the Carbonear Formation in the Whitbourne map-area.
- 10 -
The thickness of the St. John's Formation varies from 2,000 feet in the Middle Cove - Outer Cove section to about 4,000 feet in the Ferryland area.
Boundary Relationships
A transitional contact exists between the St. John's
Formation and Conception Group; it is about 150 feet thick at Middle Cove and attains maximum development of 250 feet in the Ferryland area.
Subdivision of the St. John's Formation
Studies of lithofacies have shown that the St. John's Formation is divisible into two members. They are best exposed in the Middle Cove - Outer Cove area and it is proposed that the lower member be named "Middle Cove Member" and the upper member
"Outer Cove Member" (see Table 1). The Middle Cove Member consists of two facies; mudstone facies (facies A) and laminated black shale facies (facies B) • The Outer Cove Member is mainly characterized by an interbedded sandstone and shale facies (facies C) with locally developed medium-bedded sandstone facies (facies D) , channel
-· sandstone facies (facies E), and volcanic facies (facies F) ('rable ~2).
In all investigated sections the two members have transitional boundaries.
Signal Hill Formation Name
The name "Signal Hill Formation" was proposed by Rose
(1952) for the rocks which correspond to the ~Signal Hill Sandstone"
'-
- 11 -
of Jukes (1843) and "Signal Hill Series" of Buddington (1929).
The three members of the Signal Hill Formation are equivalent to the "e, f, and g" divisions of Murray and Howley (1881-b).
Distribution, Correlation, and Thickness
The Signal Hill Formation extends in a continuous exposure from Red Head in the north to Mobile and reappears at Cape Broyle and Ferryland. The lower member was correlated with the Halls.'Town Formation and the middle and upper members with the Whiteway For- mation in the Whitbourne map-area (McCartney, 1967).
The stratigraphic thichness of this formation is 7,800 feet at Signal Hill, the type locality (Rose, 1952). This formation thins along the strike both northerly and southerly.
Boundary Relationships
The Signal Hill Formation is transitional with the under- lying St. John's Formation through a zone of green-gray sandstone, argillite, and black shale, and is overlain conformably by the Blackhead Formation.
The three members of the Signal Hill Formation are transi- tiona!. The green-gray sandstone of the lower member passes upwards into the red sandstone through a zone of interbedded red sandstone and green-gray sandstone. The boundary, taken at the first appear- ance of red beds, is nevertheless very sharp because of the contrast in color. The middle member is transitional in turn with the red conglomerate.
I .
i . I .
! r
- 12 -
Revision of Stratigraphic Boundary at Ferryland
In the Torbay map-area, three lithological criteria were used to define the boundary between the Gibbett Hill and St. John's Formations. The first two criteria were emphasized by the author in addition to the third one by Rose (1952).
(1) The St. John's Formation is characterized by alternating laminae and very thin beds of gray sandstone or siltstone and black shale (facies C of the Outer Cove Member).
(2) Green-gray argillite is typical of the Gibbett Hill Formation, while black shale is the representative rock type of the St. John's Formation.
(3) Predominance of green-gray, medium- to thick-bedded sandstone over argillite and black shale in the Gibbett Hill Formation.
These criteria support the placement of the boundaries established by Rose (1952) with a principal exception in the Ferryland area and the proposed revision is shown in Fig. 2-1.
Redefinition of the Signal Hill Formation
In a paper now under preparation by King, Hsu and Singh on the Cabot Group, Avalon Peninsula, it is proposed that the Signal Hill Formation be redefined for the following reasons:
(1) The three members of this Formation are mappable units (see geological map by Rose, 1952).
(2) The upper and middle members consist mainly of red beds and the middle member has a sharp boundary with the green-gray beds of the lower member because of the contrast in color. The red beds in the Torbay map-area can be easily correlated.
- 13 -
(3) The lower member of the Signal Hill Formation has been
correlated with the Halls Town Formation and the red beds of the middle and upper members with the Whiteway Formation in the Whitbourne map-area.
Therefore, retention of the name "Signal Hill Formation"
for only the red beds will be more natural and useful, particularly in regional correlation of rocks in the Avalon Peninsula.
The Signal Hill Formation can be redefined, as shown in
Table 2. Either (1) Make the present lower member of the Signal (, Hill Formatio~, the upper member of the St. John's Formation or
(2) Raise the rank of the lower member to establish a new formation and retain the name "Signal Hill Formation" for the red beds of the upper and middle members.
Although the first alternative is not restricted by the Code of Stratigraphic Nomenclature, correlation of a member of the Signal Hill Formation with the Halls Town Formation is certainly undesirable because of the same reason given above.
The second alternative, though enabling correlation of stratigraphic units of the same rank, is seriously hampered by the Stratigraphic Code. Article 14 of the Code states that:
"When a unit is divided into two or more of the same
rank as the original, the original name should not be employed for any of the divisions •••• For these reasons it should be normal practice to raise the rank of a unit when it becomes everywhere subdivisible into mappable units".
Consequently, it is not only necessary to abolish the name
"Signal Hill" but also necessary to raise the rank of the original formation to a higher status as a group. Abolition of the name
"Signal Hill" is unsatisfactory for it is well established type
I
1:. I
I
•,, ."· :c.-,• · · ' ' . ' , ' ' ' · . -•·:·.r~·-:.'.·•,~7!'.' "'",., ·' . ; :·-o:;--·;•·,~.--,, ., .,'~._y.,.,·,?,;•.', · ''""··--;·:· ... ~•: .. ilJ:"··~. -\ ····.;•>:-··:.:.:-'<.1"~:.:.:~¥-f'';;::'·: ;:"·~,'..; ~· /," ~--~·-, . . , ... , . . ·'''.
. . . . .
Tahl·e 2 • Redefinition of the Cabot Group.
STRATIGRAPHY BY ROSE, 1952 MAIN ROCK TYPE BLACKHEAD FORMATION Red sandstone SIGNAL HILL FORMATION
Upper member
Middle member
Lower member
ST. JOHN'S FORMATION
-
~·· . - - _ . ,
Red conglomerate
Red sandstone
Green-gray sand- stone
Gray sandstone, siltstone and black shal.e Black shale
FIRST ALTERNATIVE BLACKHEAD FORMATION SIGNAL HILL FORMATION
Cuckold Member
Battery Member ST. JOHN'S FORMATION
Gibbett Hill Member
Outer Cove Member
Middle Cove Member
SECOND ALTERNATIVE BLACKHEAD FORMATION SIGNAL HILL FORMATION
Cuckold Member
Battery Member
GIBBETT HILL FORMATION
ST. JOHN'S FORMATION Outer Cove Member
Middle Cove Member
·----=
Vl
- 15 -
locality for the red beds. Raising the rank of the Signal Hill Formation would also mean raising the rank of "Cabot Group" to a supergroup and although in keeping with the Code would cause confusion rather than clarification.
The second alternative, although apparently invalid could clarify the stratigraphy of both the Tobay map-area and the region- al stratigraphy of the Avalon Peninsula. Therefore, although
normal practice to raise the rank of a unit, the author intends to appeal to the Commission on Stratigraphic Nomenclature that the name "Gibbett Hill Formation" be used for the lower member and the names "Battery Member" and "Cuckold Member" for the middle and upper members of the original Signal Hill Formation. These proposed and revised names will be used throughout the thesis.
Correlation of Volcanic Tuff
The stratigraphic distribution of tuff beds in the Torbay map-area is shown in Fig. 3,;.2. A tentative correlation of some of
the tuff beds is attempted.
On the north shore of Calvert Bay, a 7-foot thick tuff bed is characterized by yellowish green color and irregular white and dark bands of diagenetic origin. A tuff bed, identical in color and mineralogical composition with diagenetic bands occurs on the
north shore of Mobile Bay, about 18 miles to the north of Calvert Bay.
An 8-foot thick tuff bed on the north shore of Bay Bulls occurs as an intercalation in the red beds of the Gibbett Hill Formation. It is yellowish green in color and contains tiny white spheres of diagenetic origin; at the base of the tuff bed are
'
- 16 -
concentrations of coarse detrital grains consisting mainly of pink feldspars. An identical tuff bed was also found in the White Hills, about 20 miles to the north of Bay Bulls, in the red beds at the base of the Battery Member of the Signal Hill Formation.
The striking resemblance of these tuff beds,traceable for a distance of up to 20 miles, suggests that they may be used as key beds to correlate rock units in the Cabot Group, not only in terms of lithology but on the basis of contemporaneity of origin (Fig. 3-2). The validity of these correlations can only be verified when the absolute ages of the tuff beds are determined;
if the correlation is correct, the litho-stratigraphic boundary between the Gil/)ett Hill and the Signal Hill Formations is diachronous.
- 17 -
CHAPTER III
LITHOLOGICAL UNITS AND THEIR CHARACTERISTICS Introduction
In the thesis area, the upper part of the Conception Group underlying the St. John's Formation is composed of green-gray and purplish red graywacke, siltstone, argillite, and volcanic tuffs.
Common sedimentary structures include parallel bedding, graded bedding, flute markings and load casts. These beds are turbidites and volcanic ash deposits. Ripple marks and cross laminations are very rare.
The St. John's Formation overlies the Conception Group and consists mainly of black shale in the Middle Cove Member and approximately equal amount of gray sandstone-siltstone and black shale in the Outer Cove Member. The sedimentary structures in the Middle Cove Member are mainly parallel laminations indicative of sedimentation in quiet water bodies, and slump folding suggestive of the presence of a paleoslope. The Outer Cove Member shows sedimentary structures such as cross laminations, ripple marks, scour-and-fill, and channeling.
The Gibbett Hill Formation consists mainly of green-gray sandstone with less green-gray siltstone,argillite and black shale.
Volcanic tuff beds become more abundant towards Ferryland. Sedi- mentary structures include both large and small scale cross bedding and ripple marks. Mud cracks were observed at Calvert Bay and
I
~
- 18 -
Ferryland, indicating subaerial exposure of sediments during deposition.
Conception Group
In the Ferryland area, the upper part of the Conception Group consists of parallel-bedded (Pl. 3-1), green-gray, and variegated graywacke, siltstone, argillite, and yellowish green or green-gray tuffs. The bed thickness ranges from fractions of an inch up to 5 feet, but in general less than 2 feet thick.
Graywacke
There are two structurally different types of graywacke:
(1) Graded graywacke: graywacke of this type is generally coarse- grained and mainly occurs as graded beds or as the basal part of a graded bed. The graywacke is green-gray or purplish red in color. (2) Laminated graywacke: graywacke of this type is very fine- to medium-grained and green-gray in color.
Mineralogical Composition
In thin section, the bimodal distribution of the detrital grains is the distinguishing feature of the graywacke (Pl. 3-5).
The poorly sorted, angular to well rounded detrital grains have very poor grain-to-grain contacts and appear as isolated particles in the groundrnass. The detrital grains are composed of quartz
(12-20 per cent), feldspar (19-40 per cent), and less than 10 per cent rock fragments. The modal analysis of graywacke is given in Table 2.
._,.__
- 19 -
Table J. Modal analysis of the sandstones of. Conception Group, St. John's Formation and Gibbett Hill Formation •
~
I Conception Group1 2 3 4 5
Quartz .. 17 12 15 12 20
Plagioclase 27
K-feldspar 2
Total feldspar 29 37 39 19 32
Meta-quartzite
- - -
Tr TrQuartzite
- - - - -
Ill Chert 1 4 2 1 3
+I s::
Argillite Tr
Q) 4 Tr
- -
liS
~
Rhyolite 2).I 1 1 5
-
~
~ t) Basic volcanics 1 Tr Tr
- -
ll:: 0 Granite & granophyre 1 Tr
- - -
- Total rock fragments 9 ·5 3 6 3
Matrix 45 36 36 60 30
Biotite
-
Tr Tr- -
Hematite
-
5 1-
6>t Epidote
- - -
Tr-
).!Ill Or-1
Tr Tr Tr
Ill liS Sphene
- -
Ill).!
Q) Q)
t) !:: Apatite
- - - - -
tJ•rl
<~
Zircon
- - -
Tr-
Chlorite
-
2 6 Tr 13u 3
·rl +I Ill Calcite
-
2- -
Q)+l
s:: u
Epidote 2
-
4-
Q) ::s
-
"'ro
IISO
·rl Olll ).I Authigenic quartz
- - - - -
:
. I
I
I(
,, I
