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Lothagam-Upper Nawata Mb (Miocene to of Kenya)

Also known as ETE Locality 1065, Lothagam 1C, Lothagam 1, Lothagam, Lothagam-Upper Nawata

Where: Kenya (2.9° N, 36.1° E: paleocoordinates 2.5° N, 35.3° E)

• coordinate stated in text

• local area-level geographic resolution

When: Upper Nawata and Apak Member (Nawata or Nachukui Formation), Tortonian to Tortonian (11.6 - 2.6 Ma)

• K-Ar dating constrains the Upper Nawata Member to 6.54 +/- 0.04 Ma (Marker Tuff) and 4.22 +/- 0.03 Ma (pumice clasts from 35 m above the top of the Upper Nawata Purple Marker). Thus, top of the Upper Nawata is older than 4.2 Ma, and is estimated to be 5.0 Ma.

• member-level stratigraphic resolution

Environment/lithology: fluvial; poorly lithified, graded, sandy sandstone and poorly lithified, tuffaceous mudstone

• Upper Nawata strata indicated that subsidence rates decreased dramatically, allowing the fluvial system to rework overbank deposits- recycling mud into clay to produce the characteristic multistoried sandstones. Probably decrased chanel flow, perhaps to a seasonal state. Environmental conditions suggested to be generally drier than previous or subsequent times.
• The Upper Nawata is characterized by thick, multistoried sandstone bodies, with subsidiary mudstones, and by a paucity of altered distal tephra. The type section consists of some 75% sandstones, 21% mudstones, and 4% altered tephra. The basal unit of the member is a tephra complex termed the Marker Tuff. This complex consists of a thin-bedded, relatively homogeneous lower interval (interpreted as airfall tuff), overlain by a massive, poorly sorted sandy tuff. Sandstones of the upper Nawata are typically characterized by well-developed epsilon cross-stratification and trough cross-beds in the coarser units, grading into small-scale troughs and ripple marks in the overlying finer intervals, with abrupt transitions back to coarser sands. Mudstones are subordinate, but where present they show characteristics of paleosol development. (ref # 8636 p. 22-23).

Size classes: macrofossils, mesofossils

Collection methods: bulk, surface (in situ), mechanical, sieve,

• Held at the Kenya National Museums, Nairobi (KNM-LT-). Surface collection.

Primary reference: M. G. Leakey and J. M. Harris. 2003. Lothagam: the dawn of humanity in eastern Africa. Lothagam: the dawn of humanity in eastern Africa 678 [A. Behrensmeyer/R. Bobe/R. Bobe] more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 22242: authorized by Anna Behrensmeyer, entered by Anna Behrensmeyer on 30.06.1999, edited by Suzanne Cote and Philip Mannion

Creative Commons license: CC BY (attribution)