The Chicxulub impact was bad news. Chicxulub impact - YouTube
Let's say it was between a tenth and a hundredth the size. A lot less-bad, for the larger saurians. But it didn't leave the playing field quite so clear for mammals...Shift from the location of today's Yucatan (which we wouldn't recognize), to that of Romania (which we REALLY wouldn't recognize). At the time, Europe was an archipelago, including an interesting chip of land referred to (now) as Hateg Island. Let me apologize for skipping the interesting Romanian orthography.... Back then, it was known as Ssn'sfft't'knthssinsis. Approximately. Can we just use "Hateg" for now? If I hiss and spit as much as the Variraptor-related locals I'll probably short out my keyboard.
THe actual historical impact caused tsunamis as high as 50 meters or so, not to mention the smothering five-year-winter clouds of former seafloor and former ocean and smoke (surely there had to be firestorms SoMeHoW or other!) My smaller impact still would have set up some fierce wave action, and a noticeable dimming of sunlight. Incidentally, did you know they aren't even calling it the K-T boundary any more? Something about "Triassic" being an improper term for what followed the Cretacious. Tsk, tsk. Pluto not a planet, meteoric irridium no longer being called K-T, what next, the earth not being the center of the universe? Sheesh. Footnote if you've seen the movie "Up".... SQUIRREL!!!!!!!!
Anyway, the wonderful paleogeography at the CP Geosystems site show Hateg being pretty well sheltered from direct tsunami effect by what would eventually become the Iberian peninsula. But not all. And therein lies a tale.
Chix-Minus still nuked the burgeoning pre-iron saurian civilization of today's Texas/ Oklahoma/ Nebraska. The retreating Western Interior Seaway had left that low land first swampy, then fertile plains - the locals for some unknown reason had a species that developed both brainpower and opposable digits (octoits, actually) and buried somewhere in the coal and oil of that former seafloor were a scattered few copper and bronze implements, and scads of pottery shards. Really arrogant, to think we would notice the remains of a few thousand years of almost ANY kind of civilization, some 65 million years later.
No, THOSE were not the subject of my map. They were the subject of a science fiction /fantasy story I read maybe 35 years ago that I frustratingly have not been able to recall or recover, dangit, but not this map. Steamboat-carried coexisting human & saurian sophonts, if I recall, but that's water under the bridge. No, this Hateg map has to do with folks in a more stable and simultaneously more variable situation an ocean away. Hateg island was the scene of a notable period of island dwarfism. Theory goes, species trapped a long time on a too-small landmass tend to shift to smaller sizes. (And tiny ones gradually morph to be huge). Cute lil' mammoths the size of ponies, and such. Not the mimmoths of Foglio fame but pretty small. In particular there was this group we like to call Variraptors that were somewhat smaller than human adults. That's part of the real fossil record. What the (real) Baron Nopcsa (I could NOT make up a character like him!) missed was their milder cousins we'll call the Notvery Raptors. Being less mean, less taloned, and taller but weaker than their cousins, these folks like their distant proto-Texan relatives, developed skulls full of neurons and paws full of thumb-claws. And juuuuuust when that blamed rock hit proto-Yucatan, they were getting to where they could reliably string eight words together in sentences and use nugget-copper for tools and ornaments. Boom. (And I mean a literal boom, by the way - that impact was heard in the European Archipelago!)
Iberia Island was kinda flat. Very solidly jungled, and flat. The tsunami may have been "only" twenty meters high when it hit there, but that denuded a million hectares of trees (and ferns, and fauna too). Much of which wound up in a thick floating mat bridging Hateg with lands to the NW and SE. In our timeline, the island stayed isolated for tens of millions of years, goes the theory (remember all these paleo-pronouncements of the experts are theories - nobody was there to report on events). The Variraptors and Notvery Raptors though were subjected to a mass migration of normal (!) sized 'saurs whose proto-Brit, proto-Franco, and proto-Germanic homes were suddenly waaaaay less hospitable. "So much junk in the water you could walk across an ocean", indeed. The mat was breaking up in less than ten years, but the invaders were already present in obnoxious numbers. Notvery Raptor did not curl up and die though, they cooperated, innovated, and prevailed. The brief incident - most larger threats were gone in two hundred years - had sparked enough of an uptick in intelligence that before long (well, 1800 years later) there were stone temples, roads with wagons, and a thriving cowboy culture. See, not ALL the big critters were wiped out; the big herbivores made nice meat-herds.
Did our kind have a part in this world? Funny you should ask. I mentioned the floating bridges also connecting to the southeast. That land was Cimmeria, well documented by the Hyborean historian :-) Robert Howard. (I kid you not, real paleo-designation for that chunk of land is Cimmeria - I can't pass up THAT tie-in!) There was a particularly successful strain of mammal there that would pass for human. They must've been pretty mean, and/or pretty smart, because they had stripped that area of its full-size saurians, except for the aerial sort of course (dragons = pterosaurs, anybody?) Adventurous (meaning desperate) tribes of these folk also migrated to Hateg, where they caused all KINDS of trouble. Partly because these Conan-types already had steel.
So this map is either a snapshot or a time-sequence of that conflict. I started to extract outlines from one of those CP Geosystems maps - this one. But I'm not going to directly swipe the delightfully detailed and highly plausible topography built by Ron Blakey number one because they aren't mine, and this is a contest, but number two they aren't free. But because they ARE plausible I am going to mimic the general outline he shows for Hateg. Actually, Hateg might be the less interesting blob to the NE of the land I am mapping, but phooey on that; it's boring.
Another caveat, while I'm being honest, is that the K-T transition map of ~65 million years ago where Hateg is noted is nowhere near the same as the somewhat higher resolution late-Cambrian ones from maybe 100 million years ago. A) this Hateg Island was theorized to be isolated for as much as 35 million years B) the t-100MA map has a much more interesting island about there, and C) Who's to say my Chix-minus wasn't millions of years earlier than the real Chicxulub impact - alternate is alternate!
I like to rationalize everything, and I can't get by mind off of things like HOW one gets a satellite view of a prehistoric geography... so I'll extend my story to include a point of view. It's all fantasy anyway, so why should we balk at :
Researcher Construct TC-411.08 kept meticulous orbital observations of this Yellow-2 Solid-plus-waterskin nitroxy atmo planet, watching always for the various sapient species that sprout, bloom, and wither on most such stellar bodies. Built for septuple-redundance to ward against data deterioration, even its considerable memory bulk needed data compression to retain the billion-and-a-half years of records before it returned to its origin. Here is an example of the level of detail kept, and of the sort of observations made.
Record translation to a language of the second orbit-capable civilization, nineteenth sapient species, of events subsequent to an asteroidal impact which encouraged both the sixth and seventh sapient species, and extinguished the fifth.
Time index 65.544 million orbital periods prior to the said 19th species' rise.
A nickel-iron bolide of 4.65km diameter impacted the planet with release of 12 zettajoules of energy. Unlike earlier incidents, this was not enough to cause a mass planetary extinction, nonetheless the quarter-hemisphere impacted was negatively affected. Debris fall, ocean inundation, and firestorms deleted the entirety of sapient species five, whose territory was at no point over two thousand two hundred kilometers from the impact. The two continents nearest the impact lost 35 and 48 percent of their biological diversity, opening plentiful niches for subsequent exploitation by development of other species.
This impact was entirely in ocean of some 0.6 km average depth - surrounding landmasses both constrained the tsunami effect and locally worsened it. Aerosols caused a dimming-winter of two seasons, insufficient to delete most biota. For the subject species, numbers six and seven, the devastation triggered increased competition, accentuating both their existing sapient characteristics. The accompanying graphical representations focus upon the period three to six thousand orbital periods post-impact.
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The chunkiness is just that billion-year data compression in action :-)
I know, I know - part of the fun of alternate history is the mental comparison with known history. Spotting the differences, of you will. <shrug> Can I help it if post-Pangea geography isn't a major part of our mental map?