CORRECTION: (If L4 would be correct place for UCLA-Bul-7 stromatolite ?)
2788 Ma < age of the Bul-7 stromatolite < 2803 Ma ?
>
> Best Regards,
> Hannu Poropudas, Kolamäentie 9E, 90900 Kiiminki / Oulu, Finland.
I took more close look about historical names in stratigraphy of Zimbabwe:
Macgregor 1947, 1951:
Upper Series, Shamvaian System clastic deposits
Lower Series, Bulawayan System mafic-felsic
Magnesian System, Sebakwian System
Stagman 1978:
Great Dyke
Shamvaian Group (this is same as Upper Series Shamvaian System clastic deposits )
Bulawayan Group = Upper Bulawayan + Fault ? + Lower Bulawayan ( = this is same as Lower Series, Bulawayan System mafic-felsic)
Sebakwian Group (this is same as Magnesian System, Sebakwian System)
Wilson 1979:
Great Dyke
Shamvaian Group (this is same as Upper Series Shamvaian System clastic deposits )
Upper Greenstones + Fault (Manjeri marker) + Lower Greenstones (= this is same as Lower Series, Bulawayan System mafic-felsic)
(Upper Greenstones = (Maliyami) + Cheshire + Zeederbers + Reliance + Manjeri )
(Lower Greenstones = Koodoovale + Fault (K marker) + Bend + Fault (B marker) + Hokonui )
Sebakwian Group (this is same as Magnesian System, Sebakwian System)
Foster 1979:
Great Dyke
Shamvaian Group (this is same as Upper Series Shamvaian System clastic deposits )
Bulawayan Group = Upper Greenstones + Fault (Manjeri marker) + Lower Greenstones
(Upper Greenstones = Calcalkaline + Bimodal Mixed + Basaltic + Komatic + Sedimentary )
Sebakwian Group (this is same as Magnesian System, Sebakwian System)
Wilson et al 1995:
Great Dyke
Shamvaian Supergroup = Upper Shamvaian Group + Lower Shamvaian Group ( = this is same as Upper Series Shamvaian System clastic deposits )
(Lower Shamvaian Group = H + Fault (H marker) + U6 (?) )
Bulawayan Supergroup + Fault (K marker) + Belingwean Supergroup ( = this is same as Lower Series, Bulawayan System mafic-felsic)
(Bulawayan Supergroup (?) = Upper Bulawayan Group + Fault (M marker) + Lower Bulawayan Group)
(Upper Bulawayan Group = U5 + U4W/U4E + U3 + U2 + U1 + Fault (M marker))
(Lower Bulawayan Group = Fault (M marker) + L4)
(Belingwean Supergroup = Upper Belingwean Group + Fault (B marker) + Lower Belingwean Group)
(Upper Belingwean Group = L3 + Fault (B marker))
(Lower Belingwean Group = Fault (B marker) + L2 + L1)
Sebakwian Group (this is same as Magnesian System, Sebakwian System)
Informal:
-
Shamvaian Supergroup ( = this is same as Upper Series Shamvaian System clastic deposits )
Ngezi Group (?) = Bulawayan Supergroup (?)
Fault (K marker)
Mtsingwe Group = Belingwean Supergroup
Sebakwian Group (this is same as Magnesian System, Sebakwian System)
Geochronology (Wilson et al 1995):
Great Dyke: 2574+-2 Ma, East Dyke: 2574+-2 Ma, Umvimeela (West) Dyke: 2577+-2 Ma
Upper Shamvaian Group: >2645 Ma
H: Passaford Fm: 2643 Ma (2700 Ma?)
?U6: Lake Kyle vent: 2661 Ma, Porphyries: 2677-2666 Ma
U5: Maliyami Fm: 2702 Ma
U4W/U4E: What Cheer Fm: 2683 Ma, Avalon Fm: 2696 Ma, Maparu Fm: 2697 Ma
U3: Surprise Fm: 2698 Ma, Zeederberg Fm: 2698 Ma
U2: Reliance Fm: 2745 Ma, Sills: 2740-2733 Ma (Phurombuzi, Shangani)
U1: Iron Mask Formation: 2715 Ma, Manjeri Fm: > 2745 Ma
L4: Koodoovale Fm: 2803 - 2788 Ma, Arizona Fm: 2805 Ma
L4 Fault (K marker): Eldorado Fm: 2799-2788 Ma
L3: Brooklands Fm, Buchwa quartzite
L2: Mafic Fm: 2880- 2870 Ma, Hokonui Fm: 2904 Ma
L1: Manica felsic volcanics: 2990 Ma
Sebakwian Group: > 3375 Ma.
Intrusions (not copied here due this copy would be too long):
-
REFERENCE 1:
Jelsma Hielke, 2019.
Macgregor memorial lecture.
15-17 May 2019, 61 pages. Page 30 (Current Understanding).
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About location of the UCLA-Bul-7 stromatolite:
REFERENCE 2:
Bond, G., Wilson, J. F., Winnall, N. J., 1973. Age of the Huntsman Limestone (Bulawayan) Stromatolites).
Nature Vol. 244, August 3 1973. pp. 275-276.
"The Huntsman limestone was included without question in the lower part of
the "Zwankendaba Group" of the Lower Series of the Volcanic Greenstone System, which
later became the Bulawayan System (now Group)."
"The succession in descending order is:
Greenstone
(dolerite sill) (intrusive)
Greenstone
Upper limestone
Banded ironstone
Lower limestone (with stromatolites)
Quartz sericite schist."
"From Fig. 1 (Field relations, Huntsman quarries, geologic map made by Winnall, N., J.):
Zwankendaba Memember = ( Upper limestone and banded ironstone + Quartz-sericite schist +
+ Lower limestone and banded ironstone + Quartz-sericite schist)
Lower Formation = Greenstone + Zwankendabe Member
Bulawayan Group = Greenstone + Zwankendabe Member."
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Stromatolite samples are collected from one TAILINGS of PILE and from two MINE DUMPS
by K. V. Kvenvolden. TEXT-Fig. 1 - Map of Huntsman Limestone Quarries, southwestern Rhodesia (now Zimbabwe),
showing sample localities. p. 479, REFERENCE 3.
These all are located in Lower limestone (except possible one MINE DUMP is at fault between
Lower limestone and Upper limestone?).
REFERENCE 3.
Schopf, J., W., Oehler, D., Z., Horodyski, R., J., and Kvenvolden, K., A., 1971.
Biogenicity and significance of the oldest known stromatolites.
Journal of Paleontology, v. 45, No. 3, p. 477-485, PL. 56, 2 Text-Figs., May 1971.
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This Huntsman quarries in located in the Bubi Greenstone Belt, southwest Zimbabwe:
REFERENCE 4.
MhlangA Gilbert, (Master of Science Thesis), 2002.
Data driveb predictive modelling for Archean lode gold potential,
Bubi greenstone belt, southwestern Zimbabwe.
International Institute for Geo-Information Science and Earth Observation.
Enschede, The Netherlands.
95 pages.
Stratigraphy is on page 14, Figure 2.3: Lithological map of the Bubi greenstone belt., pp. 13-15.
[ Other symbols on the map,
c: Post Archean cover
F: Felsite and quartz porphyry
D: *Dolerite*
H: Gabro
G: massive granitoids
S: Serpentinite and talc schist
yi: *Banded iron Fm*
yl: *Crystalline limestone*
x: Ndutshana Formation (greywacke and arkose)
xc: Ndutshana Formation (Conglomerate) ]
Upper Bulawayan Group,
y14: Dagmar Fm
y13: Ednovean Fm
y12: Dollar Block Fm
y11: Courtleigh volcanic Fm
Middle Bulawayan Group,
y10a: Lonely Mine Fm (sedimentary unit)
y10: Lonely Mine Fm (volcanic unit)
y9: Esinangeni Fm
y8: Ventnor Fm
y7a: Mbembesi river Fm (volcanoclastic unit)
y7: Mbembesi river Fm (volcanic unit)
y6: *Zwangendaba Fm*
y5: Sweetwater Fm
y4: Inyati Fm
Lower Bulawayan Group,
y3: Bubi source Fm
y2: Goodwood Fm
y1: Kenilworth Fm
[ Lowest,
Gm: Migmatites and gneissic granitoids]
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At the end my question concerning the UCLA-Bul-7 stromatolite:
Where in stratigraphy of Zimbabwe geology does (Bond G. et al 1973) *Lower limestone (with stromatolites)* belong?
and what is the age estimation for Lower limestone (with stromatolites) ?
Best Regards,
Hannu Poropudas