Millions of Years Ago, the Caribbean Flooded the Amazon Rain Forest—Twice

iStock
iStock

Long before the trees of today’s Amazon reached for the sky, scientists say, sharks weaved through salty waters there, and mantis shrimp rattled across the flooded forest floor. The researchers published their findings in the journal Science Advances.

Scientists have known for some time now that an area of the western Amazon basin was underwater millions of years ago. The exact source of that water has been the subject of some dispute. Some researchers have envisioned a wide river sweeping down from the Andes, while others say the inundation must have washed inland from the sea. But neither side had compelling evidence to support their ideas—until now.

The researchers studied two nearly-2000-foot-long sediment cores, one taken by an oil company in eastern Colombia, and the other taken across the border in northwestern Brazil by Brazilian Geological Survey. Each was packed with the natural detritus of millions of years of local life.

The bulk of each core told the story of a world on dry land, but within two thin slices—one from about 18 million years ago, another from about 12 million years ago—a glimmer of the sea appeared. The complete cores contained a total of 933 different types of pollen grains. The thin slices included types of pollen only found in salt water.

Bigger clues were yet to come: The researchers also found a fossilized shark tooth and the remains of a mantis shrimp. “It’s a lost ecosystem,” lead author Carlos Jaramillo, of the Smithsonian Tropical Research Institute, told Lizzie Wade in Science.

Carcharhiniformes indet. tooth from the Saltarin core, Carbonera C2 Formation, early Miocene flooding.Jorge Carillo

A modern Carcharhinus shark, similar to the fossil shark found in the early Miocene flooding.Gaby Carías Tucker and Alberto Blanco Dávila

Lasting a few hundred thousand to a few million years, each flood period was relatively brief from a geological perspective, Jaramillo says. But they weren't so brief that they didn’t completely alter the landscape.

“The life span of a single Amazonia canopy tree is about 200-400 years,” he tells Mental Floss. “Therefore, for thousands of generations, not a single tree could occupy Amazonia. In other words, the immense forest we see today is geologically young.”

The findings came as a surprise even to Jaramillo and his colleagues. He added, “I was of the opinion that there were no floodings, but it turned out I was mistaken!”

Save Up to 80 Percent on Furniture, Home Decor, and Appliances During Wayfair's Way Day 2020 Sale

Wayfair
Wayfair

From September 23 to September 24, customers can get as much as 80 percent off home decor, furniture, WFH essentials, kitchen appliances, and more during the Wayfair's Way Day 2020 sale. Additionally, when you buy a select Samsung appliance during the sale, you'll also get a $200 Wayfair gift card once the product ships. Make sure to see all that the Way Day 2020 sale has to offer. These prices won’t last long, so we've also compiled a list of the best deals for your home below.

Rugs

AllModern/Wayfair

- Mistana Hillsby Power Loom Beige Saffron/Teal Rug $49 (save $97)

- Wrought Studios Shuff Abstract Blue Area Rug $100 (save $105)

- All Modern Lydia Southwestern Cream/Charcoal Area Rug $49 (save $100)

- Union Rustic Gunter Power Loom Blue/Khaki Rug $22 (save $38)

- Willa Arlo Interiors Omri Oriental Light Gray/Ivory Area Rug $49 (save $149)

Furniture

Langley Street/Wayfair

- Alwyn Home 14-inch Medium Gel Memory Foam King Mattress $580 (save $1420)

- Andover Mills Pascal Upholstered King Bed Frame $318 (save $832)

- Sol 72 Outdoor 8-Piece Sectional Seating Group with Cushions $650 (save $1180)

- Langley Street Darren 68-Inch Tuxedo Arm Sofa $340 (save $1410)

- Three Posts Tyronza Coffee Table $147 (save $193)

Kitchen

NutriBullet/Wayfair

- Cuisinart 11-Piece Aluminum Non Stick Cookware Set $100 (save $200)

- Rachael Ray Cucina 10-Piece Non-Stick Bakeware Set $92 (save $108)

- NutriBullet Rx Smart 45-Ounce Personal Countertop Blender $124 (save $56)

- Henckels Graphite 13-Piece Knife Block Set $160 (save $340)

- DeLonghi ECP3220 15-Bar Pump Espresso Machine $120 (save $90)

Electronics

Samsung/Wayfair

- Samsung 36-Inch French Door Energy Smart Refrigerator $3600 (save $400)

- Cosmo 30-Inch Freestanding Electric Range Oven $1420 (save $1580)

- Whynter 19-Bottle Single Zone Built-In Wine Refrigerator $380 (save $232)

- bObsweep PetHair Robotic Vacuum Cleaner with Mop Attachment $226 (save $443)

- Rowenta Focus 1700 Iron with Burst of Steam $68 (save $47)

Work From Home Essentials

Foundery Select/Wayfair

- Techi Mobili Adjustable Laptop Cart $50 (save $20)

- Foundry Select Arsenault Farmhouse Desk $210 (save $190)

- Symple Stuff Clay Mesh Task Chair $128 (save $121)

- Three Posts Salina Standard Bookcase $183 (save $617)

- Lorell Hard Floor Chairmat $52 (save $39)

Sign Up Today: Get exclusive deals, product news, reviews, and more with the Mental Floss Smart Shopping newsletter!

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

100 Fascinating Facts About Earth

The best Spaceball.
The best Spaceball.
NASA

Did you know that there’s a place in the South Pacific Ocean called Point Nemo that’s farther from land than any other point on Earth? So far, in fact, that the closest humans are usually astronauts aboard the International Space Station. (And by the way: The map you’re about to look for Point Nemo on might not be entirely accurate; a certain amount of distortion occurs when trying to depict a 3D planet on a 2D surface.)

In this all-new episode of The List Show, Mental Floss editor-in-chief Erin McCarthy is journeying to the center of the Earth, and visiting its oceans, its atmosphere, and even space, in search of 100 facts about our endlessly fascinating planet.

The subjects that fall under the umbrella of “facts about Earth” are nearly as expansive as Earth itself. Geology, biology, astronomy, and cartography, are all fair game—and those are just a few of the many -ologies, -onomies, and -ographies you’ll learn about below. 

Press play to find out more Earth-shattering facts, and subscribe to the Mental Floss YouTube channel for more fact-filled videos here.