Lothagam I

Lothagam, on the southwest border of Lake Turkana, is one of the most important Miocene fossil bearing sites in the Rift Valley. Rising like a paleontological oasis from the desert, Lothagam consists of a series of high ridges, ravines, and fault planes that expose geological formations dating from 10,000 to 14 million years ago.

Professor Craig Feibel is one of the leading experts on Lothagam’s complex geological history, and led students on a 2 day excursion to study the site and its relationship to the Turkana Basin. Today’s post will cover the first day of the trip.

You can also view this post in Google Earth/Maps.

Small canyons and ravines run like mazes through the Nawata formation beds at Lothagam. Here, iron oxidized sand and mudstones produce a deep red hue in the late afternoon light.

The mid day sun is almost overwhelmingly powerful in the Turkana region, and so TBI students set out for Lothagam early on Friday hoping to explore some of its features while temperatures were still cool.

Lothagam is south of the village of Kerio and its ephemeral river, which our lorry crossed en route to the site.

Passing the dry Kerio riverbed and with Lothagam in the distance, our lorry was intersected by a large herd of Camels.

Quan is both a capable and an intrepid photographer. When our lorry was forced to stop by herds of camels crossing the road, he leapt onto the ground and approached a number of them, capturing this image.

The Turkana Basin Institute Field School arrives at Lothagam.

A series of ephemeral rivers, including the Nawata, cut their way through the site of Lothagam and leave only sandy riverbeds for most of the year. Infamous for trapping jeeps and other vehicles, we avoided these beds as much as possible by camping on the outskirts of the site.

Priscilla sits on an ancient lakebed overlooking Lothagam’s western ridge.

Lothagam is formed by two major ridges, one to the east and the other to the west, between which extends a valley holding late Miocene and also Holocene deposits. We hiked up onto the western Ridge, a "horst" or uplift formed by tectonic activity, composed of volcanic rock as old as 14 million years.

Chelsea, Kasia and Peter walk around Lothagam’s northern border and into the desert.

Joseph stands atop Lothagam’s Nabwal Arangan’s volcanic, basal boulders.

Joseph is a Turkana local and geology field hand at TBI. While students come equipped with modern hiking gear and GPS units, experience with the landscape cannot be replaced by technology. On this trip Joseph’s mobility and understanding of the terrain proved invaluable in protecting students from the unpredictable and harsh environment.

Sand dunes encroach on the Nabwal Arangan horst uplift.

A great sea of sand, blown west across the desert and originating from the Kerio river delta, slowly tries to bury the middle Miocene Nabwal Arangan beds, which form the eastern border of Lothagam.

Desert and badlands extend as far as can be seen to the northeast.

Alec begins scaling the horst, an uplift caused by tectonic activity and the site of a tectonic fault.

The shearing of tectonic plates creates slick, smooth surfaces and striking cliffs on the Nabwal Arangan beds. Though much of Lothagam can be dated from 6 to 9 million years old, these ancient rocks, pushed up from deep in the earth, may be 14 million years old.

David rests while looking out over Lothagam’s badlands.

While heading back to camp, David found a series of lakebed deposits only 10,000 years old. Though most of these exposures are far older, they were recently covered by water when Lake Turkana extended almost 80 kilometers beyond its modern borders. It is striking to find a whole meter of small freshwater mollusc shells buried in the soil a desert.

Debbit pauses beneath the mudstone exposures of the lower Nawata formation.

Sometime after a great river system deposited these soils 7-9 million years ago, tectonic activity shifted the Nawata formation and gave it a westerly tilt.

Peter and Chelsea examine an interesting bed within the Nawata formation.

Professor Craig Feibel points out the remains of a crocodile as Luke, Kelly, Quan and Julian take notes.

Self portrait, overlooking Lothagam’s Nawata formation from the west.

Walking up a tributary of the Nawata during the dry season.

Oxidized iron in the clay paleosols, deposited by large floodplains during the late Miocene epoch, glow with a red hue as the light of the afternoon begins to fade.

Ben, Kasia, Mary, John and Anacoli stand on a boulder overlooking Lothagam.

Mary and Anacoli enjoying the view and each other’s company.

Sonia, with Lothagam badlands and desert to the north.

Sonia’s seat, overlooking Lothagam, was once the shore of Lake Turkana and the site of human activity.

Chelsea, Daniel, David, Ben, Alisha, Meadow and Craig at Lothagam.

Quan ducks down beneath a mudstone paleosol.

While quan is sitting in an alcove eroded from ancient river floodplain deposits, above his head lies a layer of volcanic ash, a critical feature of Lothagam that helps geologists determine its age.