The Lake Natron Footprint Tuff (northern Tanzania): volcanic source, depositional processes and age constraints from field relations

Abstract

The Engare Sero Footprint Site, situated on the southern shore of Lake Natron in northern Tanzania, has been reported to host one of the best preserved sets of fossilized hominid footprints in the world. However, until now there has been no detailed characterization and age determination of the footprint‐bearing strata (the Footprint Tuff). Here, we combine field observations with geochemical and mineralogical analyses and measurements of the anisotropy of magnetic susceptibility to constrain depositional processes, the role of reworking and the volcanic source for the Footprint Tuff. We find that the footprint‐bearing horizon consists of volcanic ash‐fall that has been slightly reworked by water, and that this was produced during a voluminous eruption of the Oldoinyo Lengai volcano. The unit, which covered the footprints and helped to preserve them, consists of the wind‐blown material from the same eruption, mixed together with locally derived detrital material. We can constrain the ash horizon to be of Holocene age, based on: (i) the location of the Footprint Tuff within the regional stratigraphy, (ii) previous age determination of an ash layer that can be correlated with the Footprint Tuff and (iii) the regional climatological history of the area. The ash horizon was probably deposited around 11000‐10500 years ago, but could potentially be even younger than this.

Radioisotopic age, formation, and preservation of Late Pleistocene human footprints at Engare Sero, Tanzania

“…Based on the radioisotopic dating results, we infer that the footprint level is therefore older than 5760 ± 30 yrs BP and, if the MRL was deposited soon after the footprints were emplaced as discussed below, the prints are younger than 19.1 ± 3.1 ka. These constraints are, in part, consistent with a recent paper by Balashova et al (2016) who suggest a Holocene age for the footprints based on stratigraphic relationships, but differ by permitting an age into the latest Pleistocene.…”

Large mammal tracks in 1.8-million-year-old volcanic ash (Tuff IF, Bed I) at Olduvai Gorge, Tanzania

“…Tracks are typically preserved in palaeolake margin settings or ancient volcanic ash. Known sites include a single hominin track at the Sandai Plain site at Lake Bogoria, Kenya and the Engare Sero site at Lake Natron, Tanzania (Balashova et al, 2016;Hatala et al, 2020;Liutkus-Pierce et al, 2016;Scott et al, 2008;Zimmer et al, 2018). The Engare Sero site yielded over 400 human footprints attributed to a (predominantly female) group of 16 individuals, providing insight into early human group composition and dynamics (Hatala et al, 2020).…”

“…Additional late Pleistocene human track sites from the region include Nahoon (~124 ka) in Eastern Cape Province, and Brenton-on-Sea (~90 ka) and Langbaan Lagoon (~117 ka), both in Western Cape Province (Berger & Hilton-Barber, 2000;Jacobs & Roberts, 2009;Roberts, 2008;Roberts & Berger, 1997). Numerous fossil animal tracks and trackway sites preserved in aeolianites (i.e., from Witsand to Robberg Nature Reserve) that represent contemporary animal genera were also discovered along the Cape south coast (Helm, Cawthra, Combrink, et al, 2020;Helm, Cawthra, Cowling, et al, 2020;Helm, Cawthra, de Vynck, et al, 2019;Helm, Cawthra, Hattingh, et al, 2019;Helm et al, 2017;Roberts, 2008 (Altamura et al, 2018); 3 -Koobi Fora (~1.5 Ma), Ileret (~1.52 Ma), and GaJi10 sites (~1.43 Ma) (okote Member, Koobi Fora Formation), Lake Turkana, Kenya (Behrensmeyer & Laporte, 1981;Bennett et al, 2009;2014;Brown et al, 2006;hatala et al, 2017;Roach et al, 2016); 4 -sandai Plain (Loboi silts), Lake Bogoria, Kenya (Late Pleistocene) (scott et al, 2008); 5 -Engare sero, Lake natron, Tanzania (5760 ± 30 to 19.1 ± 3.1 ka) (Balashova et al, 2016;hatala et al, 2020;Liutkus-Pierce et al, 2016;Zimmer et al, 2018); 6 -Laetoli, Tanzania (~3.6 Ma) (Day & Wickens, 1980;Leakey, 1978b;Raichlen et al, 2010); 7 -nahoon site, Eastern cape Province, south Africa (~124 ka) (Jacobs & Roberts, 2009;Roberts, 2008); 8 -Brenton-on-sea, Western cape Province, south Africa (~90 ka) ; 9 -still Bay, Western cape Province, south Africa (~90 ka) (helm, cawthra, de Vynck, et al, 2019;Roberts et al, 2008); 10 -Langbaan Lagoon, Western cape Province, south Africa (~117 ka)…”

“…African Plio-Pleistocene and holocene records of hominin and large animal fossil track sites. 1 -Danakil Desert, Eritrea (~800 ka) (Archaeology news network, 2016); 2 -Melka Kunture (Upper Awash Valley), Ethiopia (~700 ka)(Altamura et al, 2018); 3 -Koobi Fora (~1.5 Ma), Ileret (~1.52 Ma), and GaJi10 sites (~1.43 Ma) (okote Member, Koobi Fora Formation), Lake Turkana, Kenya(Behrensmeyer & Laporte, 1981;Bennett et al, 2009;2014;Brown et al, 2006;hatala et al, 2017;Roach et al, 2016); 4 -sandai Plain (Loboi silts), Lake Bogoria, Kenya (Late Pleistocene)(scott et al, 2008); 5 -Engare sero, Lake natron, Tanzania (5760 ± 30 to 19.1 ± 3.1 ka)(Balashova et al, 2016;hatala et al, 2020;Liutkus-Pierce et al, 2016;Zimmer et al, 2018); 6 -Laetoli, Tanzania (~3.6 Ma)(Day & Wickens, 1980;Leakey, 1978b;Raichlen et al, 2010); 7 -nahoon site, Eastern cape Province, south Africa (~124 ka)(Jacobs & Roberts, 2009;Roberts, 2008); 8 -Brenton-on-sea, Western cape Province, south Africa (~90 ka); 9 -still Bay, Western cape Province, south Africa (~90 ka)(helm, cawthra, de Vynck, et al, 2019;Roberts et al, 2008); 10 -Langbaan Lagoon, Western cape Province, south Africa (~117 ka)(Berger & hilton-Barber, 2000;Roberts & Berger, 1997); 11 -namib sand sea, Walvis Bay, namibia (late holocene)(Morse et al, 2013); 12 -cape south coast sites, south Africa (Late Pleistocene)(helm, cawthra, combrink, et al, 2020;helm, cawthra, cowling, et al, 2020;helm, cawthra, de Vynck, et al, 2019;helm et al, 2017;helm et al, cawthra, hattingh, 2019;Roberts, 2008;Roberts et al, 2008).…”

Inferences from Footprints: Archaeological Best Practice

“…To give a flavour of the recent discoveries, in 2016 we saw the publication (Masao et al 2016) of additional footprints at the famous 3.66-million-year-old footprint site at Laetoli in northern Tanzania first reported in 1979 by Leakey and Hay (1979). Not far from Laetoli, a Late Pleistocene site on the shores of Lake Natron was reported with hundreds of visible tracks (Balashova et al 2016;Liutkus-Pierce et al 2016;Zimmer et al 2018). In 2018 the publication of children's footprints in association with butchered hippo carcasses was reported from Ethiopia (Altamura et al 2018), and there are reports of human tracks in association with giant ground sloth in North America (Bustos et al 2018).…”