Mark Wilson May 27th, 2011
MITZPE RAMON, ISRAEL–This morning Will and I finished our work with the Zihor/Menuha boundary cobbles. We drove to the southern side of Makhtesh Ramon (pictured above) to see the same units we examined 25 kilometers to the north in Wadi Aqrav yesterday. The scenery was spectacular — and the day so hot that the wind felt like a hair-dryer in the face.
The Zihor/Menuha cobbles in the southern sections. They look very much like those we studied in Wadi Aqrav. They certainly are more numerous here and easy to measure. Some have borings by bivalves (Gastrochaenolites) and worms (Trypanites). We found no encrusters here, but we did find oyster shell fragments.
A difference between these southern exposures and those to the north is that the Zihor Formation top surface here is very well exposed. We can see that it was probably lithified during the erosion that created the disconformity and the cobble lag. It is undulating and well polished. Note that it is also on the edge of oblivion.
The Zihor/Menuha boundary is very distinctive because of the erosional differences, so faults through it show up well. What kind of fault is this? (It is not a trick of perspective because the fault plane has eroded back a bit.)
This is the kind of shade we had in the field today — when we were lucky! It was 40°C by 1:00 p.m. Will is pressed up against an outcrop of the Menuha Formation, by the way, showing a sequence of carbonate nodules that may help explain the origin of the boundary cobbles.