Relive Important Archive Articles

Spring may have been when a roughly seven-mile-wide asteroid struck the Earth, immediately triggering the mass extinction that would wipe out 76 percent of known species. That key piece of timing doesn’t come from dinosaurs, but from the fish that swam in the waters dinosaurs drank from. By studying the fossil bones of these fish and comparing them to their modern counterparts, Vrije Universiteit Amsterdam paleontologist Melanie During and colleagues have come to the conclusion that the impact that ended the Age of Dinosaurs most likely occurred in the spring. Like their modern counterparts, ancient sturgeons and paddlefish of the Hell Creek Formation, found in the “Tanis” fossil site in North Dakota, grew in cycles. Those researchers proposed that this place contains critical clues about the first minutes and hours of what transpired after impact—including well-preserved fossil fish that contain asteroid impact debris in their gills. During warmer months when food was plentiful, the ancient fish grew and added more bone tissue just as their modern relatives do. During cooler, harsher months, however, their growth slowed and left a line—called a line of arrested growth, or LAG—in their bones. In addition, the bones of these fish contained signatures from oxygen and carbon isotopes. The geochemical signals in these isotopes were influenced by what the fish were eating and the waters they swam in, a natural phenomenon that has been used by paleontologists to study everything from when early whales took to the seas to what plants ancient herbivores ate. Details of the prehistoric sturgeon and paddlefish bones indicate that these fish had not yet hit the peak of their annual growth spurt, which would be expected during the warmest parts of the year. The carbon isotope ratios in the paddlefish bones also match up with this pattern. If these ancient fish lived according to a similar annual cycle as their living relatives, then the signatures in their bones hint that they perished in spring. The fact that tiny spherules thrown into the air during the impact were found in their gills places the time of death within minutes or hours of the end-Cretaceous impact. Together, these lines of evidence suggest that the impact took place while the Northern Hemisphere was in spring and the Southern Hemisphere was still in winter. Read more in the Smithsonian Magazine article by Riley Black that this was taken from, or a Science Alert article that also recaps the paper published in Nature.

As a city kid in the ‘60s my family occasionally visited my grandparents in the farm country of Washington State’s Waterville plateau. My grandfather and two uncles were wheat farmers near the small town of Withrow, the future site of which had been partly hedged in by the Okanagan lobe of the Cordilleran Ice Sheet many thousands of years ago. Sometimes my father and I would join my uncles on the dusty 15-minute drive “out in the hills” to the sagebrush-surrounded corral, well house and large cement watering trough that served the cattle herd pastured there. Overlooking the corral was a tall hill I would sometimes climb while the trough was refilling. Warned to beware of rattlesnakes, a tiring five- or ten-minute ascent would get me to the top. Astride a large boulder, I would survey the corral far below, the sound of the pump engine distantly laboring. Around me was a panorama of other hills, about whose origins it had never occurred to me to wonder. “My hill” was steep enough that even oblong rocks I tossed down its flank would often bounce and roll clear to the bottom. On occasion, this would elicit salty, muffled hollering from Dad to cease and desist. I’m a half-century older, now, but I wish I had then understood the remarkable history of my hill. How would it have felt at that young age to know that a vast ice sheet had blanketed this terrain some 12,000 years earlier and that the hill I stood on had been its progeny? That, as that glacier began to melt, streams and rivulets had formed on its immense surface? That small sinkholes and other weaknesses in the rotting ice had allowed those waters to sculpt caverns inside the glacier? That those waters carried copious quantities of sediment and rock debris captured as the glacier eroded its way hundreds of miles southward? That my hill, like an embryo within an icy womb, had begun to grow inside one of those expanding interior caverns, ultimately to be deposited on solid ground as a kame, a lasting testament to the retreating glacier? Would I have deduced that the glacier had been at least as thick upon the land as my kame was high above the corral below me? That the erratic boulder on which I sat had been deposited on that kame like a cherry atop a geological sundae? I formed an early affection for the Withrow country because of the many relatives who, not so long ago, had peopled that farmland. It’s strange to contemplate that they are mostly gone from this land now, making it seem somewhat alien to me for their absence. And yet that hill remains, a mute sentinel having witnessed the glacier that birthed it, the quiet passage of the millennia, grandpa’s construction of that watering trough in 1948, and the naive delight of a young city kid climbing its flanks in the 1960s. Dan Jordan – IAFI Wenatchee Erratics Chapter

New research reveals the ancient animals survived some 8,000 years later than previously thought Frozen soil samples collected around a decade ago are rewriting our understanding of iconic Ice Age animals like the woolly mammoth. The soil samples were pulled from Canada’s permafrost in the early 2010s, but no work on them had been published until recently. A new analysis of the DNA samples reveals that woolly mammoths, wild horses and steppe bison were around as recently as 5,000 years ago—some 8,000 years later than previously thought, according to a study published this week in Nature Communications. Scientists reconstructed the ancient ecosystem using radiocarbon dating of plant material trapped in the soil in combination with microscopic genomic sequences from animal species. Their results showed something unexpected: Large mammals like mammoths and horses were already on the decline before the climate warmed. The scientists found evidence of woolly mammoth and North American horse DNA as recently as 5,000 years ago, which means the animals held out until the mid-Holocene. Excerpted from the Smithsonian Magazine article by Corryn Wetzel

Archaeologists have long debated how and when people entered the Americas. Throughout the 20th century, the mainstream hypothesis was that the Clovis people were the first to pass into Alaska about 13,000 years ago.  Stemming from his excavations between 1977 and 1987 at the Bluefish Caves in northwestern Yukon, Jacques Cinq-Mars, a Canadian archaeologist, unearthed evidence that hunters were using the site some 24,000 years ago. Lauriane Bourgeon, a French archaeologist, has spent much of her career re-examining and dating the Bluefish Caves collection to clarify the history of the contentious site. Her research has shown that at least 15 bones from the Bluefish Caves were cut-marked by people as early as 23,500 years ago.