Speleogenesis of the Mount Elgon elephant caves, Kenya

Abstract

The eastern flanks of Mount Elgon, an early Miocene stratovolcano, host caves (~150 m long, ~60 m wide, ~10 m high) of debatable origin. Many animals, primarily elephants, "mine" the pyroclastic bedrock for sodium-rich salts. Speleogenesis has been argued to be primarily zoogeomorphic, or primarily dissolutional with only minor zoogeomorphic modification. This report provides the first detailed mapping and geomorphological study of the caves. Speleogenesis is polygenetic and strongly related to lithology. Geological units are, from the top down, ~2 m of dense pyroclastic agglomerate cap rock over which water falls, ~10 m of more permeable agglomerate, up to ~0.2 m of discontinuous impermeable lava, ~2 m of very soft and permeable agglomerate, and >2 m of impermeable swelling-clay tuff. Caves develop behind waterfalls under surface stream valleys by sapping of the incompetent agglomerate above the clay, and failure of the clay (aquiclude and base level for speleogenesis), followed by collapse of harder agglomerate layers above. The dominant passage shape is breakdown dome, with abundant fresh collapse. Geophagy by elephants and other species, and human mining significantly modify and enlarge the caves and remove collapse debris. These activities, focused on accessible and salt-rich units, create quasi-horizontal undercuts (up to ~4 m tall and deep), the loci of which move upward as collapse raises the floor. Significant erosion also occurs by incongruent dissolution, corrosion, pressure release, efflorescence flaking, and biogeochemical activity from huge bat colonies. No evidence was found of channeled flow, or of phreatic or vadose activity. These caves are probably no older than Holocene.

Paleoethologic Significance of Bioglyphs: Fingerprints of the Subterraneans

“…In fact, the ichnospecies name derives from the Greek for rodent tooth. Lundberg and McFarlane (2006) documented the spectacular bioglyphs made by forest elephants (Loxodonta africana) and other large mammals in caves in the Holocene volcano Mount Elgon in western Kenya. These caves apparently were excavated primarily, if not entirely, by the tusks of elephants that gnawed on the volcano walls to ingest sodium salts from the pyroclastic bedrock.…”

Sedimentary Dosimetry for the Saradj-Chuko Grotto: A Cave in a Lava Tube in the North-Central Caucasus, Russia

“…In Africa, several caves in granite, ash beds, or lava tubes have yielded hominin fossils or tool assemblages, especially those near the East African Rift. These caves include Kitum [11], Leviathan [12], the Mau Mau Caves, and Makubike [13]. Again, however, many more important multi-layered sites yielding hominins, their artefacts, or Quaternary or Pliocene vertebrates have occurred in karst caves within Africa.…”

Description of two new genera and ten new species of Metarbelidae (Lepidoptera: Cossoidea) from western, north-central and eastern Africa with notes on habitats and biogeography /

“…The cave was occupied by humans for shelter until about 90 years ago. The walls and ceiling show lots of soot and rock paintings (Lundberg & McFarlane 2006). Hence, it can be surmised that the forests surrounding the cave were modified by humans.…”