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Geological Society, London, Memoirs; 2008; v. 33; p. 93-96;
DOI: 10.1144/M33.App01
© 2008 Geological Society of London

Articles

Appendix 1

J. B. Dawson

University of Edinburgh (jbdawson{at}glg.ed.ac.uk)


Appendix 1A. Radiometric dates from Northern Tanzania

Sample Lithology and location Age (Ma) Refs
Lake Natron Area (see also unpublished dates below)
572 Phonolitic nephelinite, Shombole 1.96±0.07 3
580 Phonolitic nephelinite, Shombole 2.00±0.05 3
138 Nephelinite, south slopes of Gelai 0.96±0.03 6
Nephelinite, south slopes of Gelai 0.99±0.03 6
Biotite lava, Mosonik 3.18±0.08 1
KA 1757
NATM89-07 Nephelinite, Mosonik 3.53±0.06 2
S11/4 Nephelinite, flow from Mosonik 1.28±0.05 11
KA 1755 Basalt, Peninj Gorge 1.90±0.07 1
KA 1755R Basalt, Peninj Gorge 1.77±0.04 1
KA 2570 Basalt, Malambo Gorge 3.5±0.46 1
KA 1185 Basalt, underlying Peninj Group sediments 2.99±0.09 2
KA 1754 Basalt, Humbu Formation (Lower Peninj Group) 1.55±0.03 1
KA 1754R Basalt, Humbu Formation 2.27±0.06 1
KA 2382 Basalt, Humbu Formation 0.96±0.1 1
KA 2382R Basalt, Humbu Formation 1.21±0.36 1
KA 2578 Basalt, Humbu Formation 0.97±0.25 1
KA 2646 Basalt, Humbu Formation 1.21±0.1 1
Basal tuff, Humbu Formation 1.70±0.02* 2
KA 2410 Intra-Moinik basalt, Moinik Formation (U. Peninj Group) 1.33±0.05 1
KA 2589 Intra-Moinik basalt, Moinik Formation 1.38±0.09 1
KA 1186 Intra-Moinik basalt, Moinik Formation 1.41±0.04 2
KA 1187 Intra-Moinik basalt, Moinik Formation 1.13±0.06 2
S1 1/6 Nephelinite, interbedded with Upper Moinik Formation. 1.31±0.26 11
Bird Print Tuff, Moinik Formation 1.26±0.04* 2
3 Phlogopite, Kisetey crater tuff 0.57±0.15 5
Phlogopite, Kisetey crater tuff 0.14±0.15
891 Phlogopite, Loolmurwak crater tuff 0.53±0.1 5
Phlogopite, Loolmurwak crater tuff 0.41±0.1 5
105 Phlogopite, Loolmurwak crater tuff 0.19±0.08 5
Phlogopite, Loolmurwak crater tuff 0.14±0.12 5
Calcrete, on reworked tephra, 3–5 km south of Lake Natron 0.13 Ma 7
Calcrete, overlying black tuffs, Loolmurwak crater 0.35±0.01 7
11031 Phonolite, Oldonyo Lengai 0.15±0.02 4
Engaruka-Manyara Area
155 Olivine basalt, south slopes of Ketumbeine 1.54±0.1 6
Olivine basalt, south slopes of Ketumbeine 1.66±0.07 6
156 Olivine basalt, south slopes of Ketumbeine 1.73±0.08 6
Olivine basalt, south slopes of Ketumbeine 1.87±0.08 6
11255 Olivine melanephelinite, escarpment base, Engaruka 3.2±0.5 4
11245 Olivine basalt, escarpment top, Engaruka 1.4±0.5 4
11247 Trachyandesite, escarpment top, Engaruka 1.8±0.6 4
11 Olivine trachybasalt, flow, small crater, 1 mile south of Engaruka 1.15±0.04 5
Olivine trachybasalt, flow, small crater, 1 mile south of Engaruka 1.11±0.06 5
139 Olivine trachybasalt, Narabala top of scarp 1.2±0.04 5
Olivine trachybasalt, Narabala top of scarp 1.18±0.05 5
137a Olivine trachybasalt, Narabala, flow from fault 1.21±0.05 5
Olivine trachybasalt, Narabala, flow from fault 1.15±0.04 5
Olivine trachybasalt, Narabala, flow from fault 1.09±0.05 5
Olivine trachybasalt, Narabala, flow from fault 1.17±0.04 5
S13/2 Olivine basalt, Engaruka Basin escarpment 1.26±0.07 11
BD181 Olivine basalt, extruded from main rift fault, Kitete 1.13±0.16 5
Olivine basalt, extruded from main rift fault, Kitete 1.23±0.05 5
BD180 Olivine basalt, extruded from main rift fault, Kitete 0.95±0.08 5
Olivine basalt, extruded from main rift fault, Kitete 1.08±0.05 5
S13/3 Basalt, extruded from foot of Kitete escarpment 1.0±0.1 11
S14/4 Basalt, top of Kitete escarpment 0.8±0.4 11
S14/5 Basalt, foot of Kitete escarpment 1.2±0.06 11
11163 Picritic basalt, escarpment base, north of Lake Manyara 3.8±0.2 4
11170 Basaltic andesite, escarpment top, north of Lake Manyara 2.25±0.1 4
2a Basalt, interbedded with lacustrine sediments, base of main rift escarpment, Lake Manyara 4.86±0.24 11
7b Basalt, top of rift escarpment, Lake Manyara 1.5±0.1 11
Essimingor-Burko-Tarosero-Monduli
Melanephelinite, Essimingor 8.1±1.0 4
Melanephelinite, Essimingor 7.35±0.65 4
142 Nephelinite, gully on SE slopes, Essimingor 4.68±0.09 6
Nephelinite, gully on SE slopes, Essimingor 4.89±0.09 6
143 Nephelinite, gully on SE slopes, Essimingor 3.23±0.07 6
Nephelinite, gully on SE slopes, Essimingor 3.20±0.06 6
137b Nephelinite, gully on SE slopes, Burko 1.03±0.04 6
Nephelinite, gully on SE slopes, Burko 0.91±0.03 6
309 Olivine basalt, lower north slopes, Tarosero 2.4±0.62 5
305 Sodalite phonolite, faulted north slopes of Tarosero 2.25±0.06 5
306 Sodalite phonolite, faulted north slopes of Tarosero 2.2±0.06 5
510 Phonolite, lower NW slopes of Tarosero 2.21±0.1 5
490 Unfaulted trachyte, summit of Tarosero 2.16±0.06 5
Unfaulted trachyte, summit of Tarosero 2.04±0.04 5
488 Unfaulted trachyte, summit ridge, Tarosero 1.98±0.03 5
Unfaulted trachyte, summit ridge, Tarosero 1.90±0.04 5
304 Olivine basalt, highest flow on Matunginini fault escarpment 2.00±0.05 5
136 Olivine basalt, north slope of Monduli Mtn, near Tarosero escarpment 2.09±0.06 6
Olivine basalt, north slope of Monduli Mtn, near Tarosero escarpment 2.15±0.05 6
Kwaraha-Hanang
11068 Olivine melanephelinite, Kwaraha 1.5±1.0 4
11073 Olivine melilite, Kwaraha 1.05±0.15 4
11085 Olivine melanephelinite, Kwaraha 1.08±0.18 4
11088 Nephelinite, Kwaraha 0.7±0.0 4
11001 Nephelinite, Hanang 1.5±0.3 4
11030 Nephelinite, Hanang 0.9±0.2 4
Crater Highlands
Nephelinite, Sadiman 3.32±0.06 2
2238 Nephelinite, Sadiman 3.7 7
Tuff 8 Tephras, Upper Laetolil Beds, ?from Sadiman 3.46±0.12 8
11113 Nephelinite, Sadiman 4.5±0.4 4
NAT90-28 Ignimbrite, Ngorongoro 1.83±10.03 2
NAT90-30 Ignimbrite, Ngorongoro 1.98±0.032 2
Ignimbrite, Ngorongoro 2.02±0.02* 2
20 Trachyte, Ngorongoro 2.45±0.15 9
Plagioclase (tuff), Ngorongoro 2.23±0.1 9
Plagioclase (tuff), Ngorongoro 2.28±0.14 9
Plagioclase (tuff), Ngorongoro 2.45±0.15 9
Plagioclase (tuff), Ngorongoro 2.25±0.15 9
Plagioclase (tuff), Ngorongoro 2.81±0.11 9
11147 Olivine basalt, Ngorongoro 3.7±0.8 4
11124 Phonolite, north of Lemagrut 5.5±0.1 4
11130 Basaltic andesite, Lemagrut 4.3±1.05 4
11115 Silicic andesite, Lemagrut 2.7±0.2 4
7c Ankaramite, Lemagrut 3.1±0.3 11
Naibadad beds, Laetoli 2.26±0.06 8
Vogesite lava flow remnant, Ogol lavas, Laetoli area 2.41±0.12 8
Biotite in tuff, upper Laetoli Beds 3.49±0.12 8
Biotite in tuff, lower Laetoli Beds (age mean of 2) 3.76±0.03 8
LMGT89-02 Ignimbrite, Lemagrut 1.92±0.04 2
LMGT89-03 Ignimbrite, Lemagrut 1.82±0.03 2
Ignimbrite, Lemagrut 1.97±0.01* 2
NATM89-13 Trachytic lava, Olmoti 1.65±0.03 2
NATM89-13A Trachytic lava, Olmoti 1.11±0.09 2
NATM89-11A Ignimbrite, Olmoti 1.23±0.04 2
NATM89-08 Phonolitic tephrite, Olmoti 1.07±0.05 2
OGMW89-54 Trachyandesite flow, Olduvai, from Olmoti? 1.09±0.03 2
MW89-17 Nephelinite, Embagai 0.5±0.4 2
MW89-15A Nephelinite, Embagai 1.05±0.02 2
MW89-14A Nephelinite, Embagai 1.52±0.03 2
Tephras, Embagai c. 0.6* 2
Olduvai Gorge
Naabi ignimbrite below base of Bed I 2.029±0.005* 13
Coarse feldspar crystal tuff (CFCT) above Naabi ignimbrite 2.018±0.019*14 13
Basalt immediately above CFCT, Bed I (?derived from Olmoti (Hay, 1976) 1.96 12
Basalt immediately above CFCT, Bed I 1.865±0.02 13
Tuff IB, above basalt, Bed I 1.798±0.004* 13
Tuff IB, above basalt, Bed I 1.786 12
Tuff IF top of Bed 1 1.749±0.009* 13
Tuff IIA base of Bed II 1.71 12
Ndutu Beds (calcretes and Limicolaria shells) 30-22 Ka BP 7
Naisiusiu Beds (calcretes, collagen and egg-shell) 20-9 Ka BP 7
Calcretes overlying Naisiusiu Beds) 6.6-4 Ka BP 7
Meru Area
135 Alkali basalt block, collapsed east wall of caldera, Meru 0.09±0.02 6
Alkali basalt block, collapsed east wall of caldera, Meru 0.115±0.007 6
141 Nephelinite block, collapsed east wall of caldera, Meru 0.099±0.005 6
Nephelinite block, collapsed east wall of caldera, Meru 0.097±0.004 6
3221 Pumice from mantling ash, Oldonyo Sambu scoria cone <0.55 10
Pumice from mantling ash, Oldonyo Sambu scoria cone < 0.10 10
3403 Nephelinite, Meru summit 0.059±0.010 10
Nephelinite, Meru summit 0.067±0.008 10
3655 Nephelinite, SW of Meru West (3885 m) 0.08±0.005 10
Nephelinite, SW of Meru West (3885 m) 0.08±0.005 10
3930 Phonolitic nephelinite, summit group, Meru West (2395 m) 0.079±0.004 10
Phonolitic nephelinite, summit group, Meru West (2395 m) 0.09±0.004 10
3114 Phonolitic tephrite, Main Cone group, behind Ash Cone 0.107±0.006 10
Phonolitic tephrite, Main Cone group, behind Ash Cone 0.102±0.005 10
4231 Phonolitic tephrite, Main Cone group, behind Ash Cone 0.107±0.007 10
Phonolitic tephrite, Main Cone group, behind Ash Cone 0.111±0.007 10
4191 Nephelinite, Main Cone group, NW flanks of Meru 0.163±0.013 10
Nephelinite, Main Cone group, NW flanks of Meru 0.148±0.010 10
3203 Sanidine phonolite, Naigonesoit tholoid, north Meru 0.168±0.009 10
Sanidine phonolite, Naigonesoit tholoid, north Meru 0.158±0.010 10
Sanidine phonolite, Naigonesoit tholoid, north Meru 0.179±0.010 10
3193 Trachytoid phonolite, north of Naigonesoit, north Meru 0.384±0.009 10
Trachytoid phonolite, north of Naigonesoit, north Meru 0.377±0.009 10
3127 Phonolitic nephelinite clast from breccia, Little Meru 0.273±0.006 10
Phonolitic nephelinite clast from breccia, Little Meru 0.281±0.005 10
3912 Phonolite, Oldonyo Sambu (parasitic cone) 0.311±0.011 10
Phonolite, Oldonyo Sambu (parasitic cone) 0.3±0.011 10
3303 Phonolitic nephelinite, Oldonyo Sambu 0.313±0.009 10
Phonolitic nephelinite, Oldonyo Sambu 0.299±0.010 10
Phonolitic nephelinite, Oldonyo Sambu 0.303±0.010 10
3436 Phonolitic nephelinite, Meru West scarp 1.53±0.03 10
Phonolitic nephelinite, Meru West scarp 1.49±0.03 10
4056 Ankaramitic basalt from Cinderella Cone, Oljoro valley 1.56±0.05 10
Ankaramitic basalt from Cinderella Cone, Oljoro valley 1.62±0.05 10
4054 Amphibole-rich ankaramitic basalt from Cinderella Cone, Loljoro valley 1.77±0.04 10
Amphibole-rich ankaramitic basalt from Cinderella Cone, Loljoro valley 1.67±0.04 10
Amphibole-rich ankaramitic basalt from Cinderella Cone, Loljoro valley 1.93±0.04 10
3435 Sanidine phonolite clast from breccia, Meru West scarp 2.03±0.04 10
Sanidine phonolite clast from breccia, Meru West scarp 1.99±0.04 10
3706 Mugearite, Flood lava group, Oljoro valley 2.3±0.06 10
Mugearite, Flood lava group, Oljoro valley 2.25±0.04 10
3705 Alkali basalt, Flood lava group, Oljoro valley 2.44±0.06 10
Alkali basalt, Flood lava group, Oljoro valley 2.49±0.06 10
Kilimanjaro
Lower olivine basalts, Naiperra, Amboseli 0.85±20% 14
Lower olivine basalts, Naiperra, Amboseli 1.10±15% 14
Lower olivine basalts, Ngong Naro, Amboseli 0.420±15% 14
KA940 Trachybasalt, Mawenzi 0.514 15,16
KA947 Basalt, Lava Tower series, Shira 0.463 15,16
KA937 Obsidian, Rhomb Porphyry Series 0.365 15,16
134 Trachyte, Lent Group, Shira Plateau 0.27±0.02 6
Trachyte, Lent Group, Shira Plateau 0.23±0.03 6
Trachyte, Lent Group, Shira Plateau 0.23±0.02 6
200 Anorthoclase phenocryst (blocky habit), caldera rim, Kibo 0.22±0.01 10
246 Anorthoclase phenocryst (blocky habit), caldera rim, Kibo 0.19±0.01 10
Anorthoclase phenocryst (blocky habit), caldera rim, Kibo 0.17±0.01 10
223 Anorthoclase phenocryst (rhombic habit), caldera rim, Kibo 0.23±0.03 10
Anorthoclase phenocryst (rhombic habit), caldera rim, Kibo 0.26±0.03 10

Dates are by the standard K–Ar, except those asterisked for which the method was single crystal laser fusion on feldspars, and some radiocarbon dates (Ref. 7)

References: 1, Isaac & Curtis 1974; 2, Manega 1993; 3, Fairhead et al. 1972; 4, Bagdasaryan et al. 1973; 5, MacIntyre et al. 1974; 6, Evans et al. 1971; 7, Hay 1976; 8, Drake & Curtis 1987; 9, Grommé et al. 1970; 10, Wilkinson et al. 1986; 11, Foster et al. 1997; 12, Curtis & Hay 1972; 13, Walter et al. 1991; 14, Williams 1969; 15, Evernden & Curtis 1965; 16, Downie et al. 1956.


Appendix 1B. Unpublished K–Ar dates on olivine basalts in Lake Natron area

Sample Location Age
DD1248 Foot of main escarpment, north end of L. Natron, 2°4'37'S 35°57'37''E. Early Oldoinyo Sambu activity; overlies Usagaran quartzite. 7.7±0.7
DD1258 Top of main escarpment, 3 km south of summit of Old. Sambu 2°9'47''S 35°56'32''E. Latest Old. Sambu lava: maximum age of the Natron boundary fault 2.5±0.15
DD1298 Top of main escarpment, north of Peninj delta. 2°16'01''S 35°56'21''E. Minimum age of Humbu formation 2.1±1.2
DD1306 West slopes of Peninj valley. 2°16'48''S 35°54'57''E. Maximum age of the Humbu Formation 1.93±0.8
DD1385 East side of Moinik valley. 2°28'33''S 35°52'23''E. Maximum age of the Moinik Formation 0.73±0.3

Samples collected by D.Dundas; analysed by N.J.Snelling. These data, together with the unpublished map (mapped 1966) and report by D. Dundas of Quarter Degree sheets 16 and 27, Loliondo, were made available by courtesy of the Tanzania Department of Mineral Resources in 1966.


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Bagdasaryan, G. P., Gerasimovskiy, V. I. Polyakov, A. I. Gukasyan, R. K. & Vernadskiy, V. I. 1973. Age of volcanic rocks in the rift zones of East Africa. Geochemistry International, 10, 66–71.[GeoRef]

Bishop, W. W., Miller, J. A. & Fitch, F. H. 1969. New potassium-argon age determinations relevant to the Miocene fossil mammal occurrences in East Africa. American Journal of Science, 267, 669–699.[Abstract/Free Full Text][Web of Science][GeoRef]

Curtis, G. H. & Hay, R. L. 1972. Further geological studies and K-Ar dating at Olduvai Gorge and Ngorongoro crater. In: Bishop, W. W. & Miller, J. W. (eds) Calibration of Hominoid Evolution. Scottish Academic Press, Edinburgh, 107–134.

Drake, P. & Curtis, G. H. 1987. K-Ar geochronology of the Laetoli fossil localities. In: Leakey, M. D. & Harris, J. M. (eds) Laetoli, a Pliocene site in northern Tanzania. Clarendon Press, Oxford, 48–52.

Downie, C., Humphries, D. W. Wilcockson, W. H. & Wilkinson, P. 1956. Geology of Kilimanjaro. Nature, 178, 828–830.

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Fairhead, J. D., Mitchell, J. G. & Williams, L. A. J. 1972. New K/Ar determinations on Rift volcanics of S. Kenya and their bearing on the age of Rift faulting. Nature, 238, 66–69.

Foster, A., Ebinger, C. Mbede, E. & Rex, D. 1997. Tectonic development of the northern sector of the East African Rift System. Journal of the Geological Society, London, 154, 689–700.[Abstract/Free Full Text][CrossRef][Web of Science][GeoRef]

Grommé, C. S., Reilly, T. A. Mussett, A. E. & Hay, R. L. 1970. Palaeomagnetism and potassium-argon ages of volcanic rocks of Ngorongoro caldera, Tanzania. Geophysical Journal of the Royal Astronomical Society, 22, 101–115.[Web of Science]

Hay, R. L. 1976. Geology of the Olduvai Gorge. University of California Press, Berkeley.

Isaac, G. L. & Curtis, G. H. 1974. Age of the Acheulian industries from the Peninj Group, Tanzania. Nature, 249, 624–627.

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