“Exploring an Ancient Ocean in Northern California” by Jim Livingston

In the spring of 1975, I drove to the Bald Hills, on the west side of the Upper Sacramento Valley, east of Redding, California. The area was aptly named, as few trees grew amid the golden grass-covered rolling hills and dry arroyos. It was here that I hoped to find evidence of an ancient ocean.

I was looking for fossil ammonites to support the theory. Ammonites left a variety of snail-shaped shells but are related to squids and octopi. I’d already found a few on previous excursions, but I was looking for impressive specimens, worthy of display.

I was also looking for belemnite fossils. They’re an extinct relative of the squid, similar to today’s cuttlefish with the addition of a longer end opposite the tentacles and a single, cigar-shaped bone.

The heat was already in the mid-nineties, and we’d been promised a low triple-digit high by mid-afternoon. Still, I was eager to explore. Slinging my pack, I headed for the gate in the old corral fence. One step through it and I found myself on an ancient ocean bed.

Walking along the arroyo, something white, sixteen feet up a steep bank caught my eye. It was an object made of alabaster. A band of hard slate, several feet thick, cut through the middle of the crumbly gray shale cliff and below the alabaster object. I climbed and soon reached the slate.

Peering into a horizontal crevasse, I was startled by movement. A living fossil? No. Staring back at me was a diamondback rattlesnake. Its forked tongue flicked out as if to say, “Hi there.’”

Since it appeared unbothered, I left it alone, backed away, returned to the gully bottom, and began cracking open roundish cobbles—ball-shaped concretions that tended to form around fossils. Over time, the shale would erode, and the concretions would pop out. The rounder the concretion, the greater the likelihood of finding a fossil. With my rock hammer, I broke open one the size of a softball and found a well-preserved ammonite (Fig. 1).

Figure 1. Late Cretaceous Ammonite, Horsetown Formation, Shasta County, California.

As I continued along the bottom, I came across several smaller ammonites, none in good condition. But one odd-looking rock buried in the soil caught my eye (Fig. 2). Using my rock hammer, I pried it out and was rewarded with a rare piece of petrified wood riddled with boring clam burrows from the land of dinosaurs. This wood indicated that an island had probably lain nearby in ancient days. The wood had evidently floated down a stream and into the sea, where the clams colonized it. The wood eventually became waterlogged and sank to the bottom.

Figure 2. Petrified Wood with boring clam burrows.

I stashed this find then continued my way. A bit later, I broke open a larger concretion. The ammonite fossil inside shattered (Figs. 3 and 4). Its internal chambers were filled with calcite crystals. This was puzzling. On one side, the shell’s fragments were dislocated but still attached to the main structure. How could this happen?

–Figures 3 and 4. Late Cretaceous Ammonite, Horsetown Formation, Shasta County, California.

I imagined an event: back in the day, a mosasaur or even an ichthyosaur had crushed the shell with its powerful jaws, devouring the ammonite’s soft tissues. But enough membrane remained to tie the fragments together, and then they sank to the ocean floor. And so, I acquired another sample of marine life.

Further down the arroyo, I recovered some of the belemnites lying among the cobbles.  The larger one measured six inches long (Fig. 5). My stash was growing.

Figure 5. Belemnite, Late Cretaceous, Horsetown Formation, Shasta County, California.

Figure 6. Crustacean, Late Cretaceous, Horsetown Formation, Shasta County, California.

Finally, it was time to head home. I had some good finds, but not the large ammonite I was seeking. I trudged back up the arroyo with my heavy pack and sweat-soaked hatband and T-shirt, giving the rocks around me one last look.

Then, as if waiting for me, a large flattish boulder caught my eye. Along its edge teased the unmistakable ribbing of an ammonite. Excited, I wrestled it free from the ground then carefully chipped the encasing rock away. Fifteen minutes later, I gazed at a beautiful ammonite thirteen inches across (Fig. 7). And now, I carried my treasures back to the car. It had been a great day.

That afternoon, pondering my snapshot of life in the deep ocean seventy million years ago, I was left humbled and amazed.

Figure 7. Late Cretaceous Ammonite, Horsetown Formation, Shasta County, California.