How to Screen Wash Project 23 Matrix

Over 2000 buckets of matrix produced from Project 23 thus far and what to do with them? Reduce! Our matrix contains a lot of non-asphaltic sediment that can be washed away. Over past months Excavators have been working on a new system for screen washing, with major organizing and tool/equipment building done by Karin.

First, we choose buckets that have a lot of fine non-asphaltic sediment and soak overnight:

We then scoop muddy squishy matrix from its bucket into a specialized bucket with a 20 mesh (size used for micro-fossil sorting) screen on the bottom (that Karin made) and swish and break

down the fine dirt that washes into tubs of water (that Karin made, sitting on a wooden platform that Karin made)

Between washings, the bottom is cleaned. It is a rather enjoyable process bringing us back

back to our mud pie making days.

The matrix dries on screens and then is bagged. Sometimes visible microfossils are "high graded" into a capsule within the bag. One rather large recent surprise was a Nothrotheriops shastensis patella in matrix from Box 1. It's the first Shasta ground sloth found in Project 23!

A five gallon size bucket of matrix reduces down to about a gallon size bag of matrix that will later be degreased, and then we re-use buckets - yay!



In other P23 news....

Box 14 had a bit of a make-over with our use of one of the fancy canopies from Media Day

Little Timmy's left lower mandible shows up near a disturbed part of the deposit


An herbivore (probably bison) maxilla is revealed in Box 1

And in the lab, Herb found two elements (occipital horns and maxilla) from a coastal horned lizard in Box 14 while sorting matrix from a block of asphaltic sand containing many small delicate bones. These are the first horned lizard bones found since 1929 in Pit A, and only the second individual ever identified at Rancho La Brea.