I am not a scientist but a computer Systems Administrator but I have a theory as everyone else does.
I was watching a program on television called ‘Time Warp’, a great visual oriented program that slows down different events with a high-speed camera (up to 6000 fps). On that session they were photographing a drop of water falling into a pan of water. The water drop carves out a depression, and then the cornet comes up and then the pillar of water and finally the concentric rings emanating from the center of the event. This is also the basics functions of the Chicxulub impact though it did not replicate the actual size and environmental scaling of the actual event.
Time Warp also did other demonstrations and one was dropping a drop of water into very shallow water. The physics of the demonstration was the same as the first demonstration, until the pillar of water was to rise from the center which was not much higher than the coronet and then the concentric rings occurred.
The Scientist that was assisting the demonstration team also had a high speed camera and had been experimenting with variations of dropping water into water to study impacts. He made the statement that when the water was shallow (no mention about size of the object or the depth ratio) you would get the depression being carved out and then the cornet but because of the shallowness of the water the pillar of water never develop much higher than the coronet. Even though the exact same physics would not coincide with the physics of an Asteroid impact exactly but would still follow the same basic physics. If an object hits solid ground it will dig out a crater, Coronet then pillar, and finally the concentric ring but the harder the surface of the impact the shorter the pillar. Without the tall column of water and debris raising up from the Chicxulub event high into the atmosphere there would not be the world wide firestorm (probably more localized than world wide and the main portion of the sea was on one side of the impact event) that would have burned up everything (there has been no world wide charcoal layer, though there has been soot found at most KT Boundary sites, associated with the KT boundary or the Chicxulub Impact Event) which indicated no world wide firestorm or no world wide vegetation to burn. Also the acid rain which was supposed to have been world wide would have killed most of if not all of the frog, salamander and other amphibian species (which are extremely susceptible to acid/alkaline changes) that actually survived the extinction event as well as most of the fresh water species.
The iridium layer could have come from something more than the actual impact event, such as a portion of the asteroid being burned off as it blasted through the atmosphere (as well as from the burning up of sucker asteroids moving along with the main asteroid) and distributed across Pangaea. It could also be wind patterns from west to east which would have spread much of the dust from the actual impact since it occurred on the western end of the Continental group; there are also several other impacts other than the Chicxulub impacts that occurred which I will talk about later in this article. At this time the continents were grouped much closer together so that a smaller plume could have distributed the iridium deposits seemingly more wide spread. A group of small sucker asteroids (most large astral bodies have moons or sucker asteroids, collected along their trajectory) following the main asteroid might also account for the irregular distribution of iridium as each of their trajectories may have differed.
Plate tectonics, weather, erosion, volcanism, and other large natural disasters (including seas being created and/or destroyed) also caused iridium layers and spherules to have been displaced which can account for any discrepancies in the dating and the closeness of the continents would have allowed the dispersion to look larger than it would if looking at the present continent arrangement.
The Chicxulub impact was not in the same environment that is always displayed when they do an animation of the Chicxulub event. The Continents had not really separated (no Atlantic Ocean at this time but the shallow enclosed Tethys Sea) very much and the sea that the Chicxulub asteroid fell into was a shallow continental shelf sea in the far west of the continental group. The Chicxulub impact is actually on continental shelf and possibly did not even disturb the Methane Hydride layers. Maybe the Chicxulub event was not the whole cause of the dinosaur extinction or even a major effect at all.
If the scenario that is put forth where the Impact was in deep sea bed, which caused the Carbonate Layers to heat turning them into Carbon Dioxide and Carbon Monoxide (Which are heavier than air) which circled the earth and killed only the Dinosaurs and a few other plants, and some of the fish and animals picking and choosing who is to go extinct seems a little far fetched. This is like changing the extinction event to fit a theory rather than fitting the extinction event to the outcome of the event. If we look, at the Lakes in Africa that released Carbon Dioxide from reservoirs, dissolved in the cold deep-water layers, that event killed every animal in the area above and below ground, and just those that flew above the Carbon Dioxide levels lived. Following their premise the Chicxulub Impact Event would have killed everything but all plants and fish that were not in the inland sea where the impact occurred.
According to paleontologist the Dinosaurs had been in decline for at least 3 to 10 million years prior to the Chicxulub Impact Event when most of the animals and many plants and fish became extinct. At this time there are dramatic changes going on. These changes include lowering of sea levels which a new study correlates Sea Level Changes and Extinction Events. Even though there are sea level changes in relation to extinction events, I do not believe that these are the ultimate cause. When I look at the records there are extinction events with both ocean raising and lowering, but I think that this is all part of the real cause loss of food. Climatic change, such as the melting of the glaciers, the lowering Oxygen levels, changing weather patterns as well as growing and birthing cycles on land and in the sea initiates the extinction event. Some data point to an average rise in temperature of 8 °C (14 °F) in the last half million years before the impact at Chicxulub. In refering to a program that was presented on television (6 ° that could change the world) that 6 °C raise in temperature would cause the extinction of the human race what would 8 °C (14 °F) do compounded by lowered oxygen levels and climatic changes?
If the Methane Hydride layer at the bottom of the ocean was release (methane is lighter than air) it could have left a layer of good or better air close to the surface. An infusion of a massive quantity of Methane could leave indications geologically that could be construed as an oxygen decline. Bubbling up out of the oceans, along with an ocean temperature rise, it might not have killed but weakened the environment and resources. Ocean species that lived in areas of the ocean that did not release the Methane Hydride or no Methane Hydride occurred (where water still had a cooler temperature) or fresh water. Though many fresh water species also went extinct, these might linked to other causes. As a side note various fish species that go to sea then return to fresh clean water to spawn maybe caused by Methane Hydride residual in the seawater. The extinction occurred to about 60% of terrestrial life, up to 90% of Ocean life. Many insect species even went extinct. The release of methane into the atmosphere does not mean that it poisoned and killed any dinosaurs but it at least weakened their environmental and resource systems.
Events are like a tree where many previous events support the following events. The large amount of carrion that would have been occurring in the ocean and on land would have poisoned many a drying water hole or diminishing streams and rivers purity. Some species that are fresh water can also exist in salt water and could have brought into the fresh water environment, bacteria that could harm or kill other species.
If enough of the Methane Hydride is released combining with the high moisture level in the atmosphere, a heavy cloud layer of Methane and water which would have dramatically increased the global warming that had been occurring for the last 10 million years. Most of the animals that lived close to the surface or below would have been better able to survive the environmental changes (temperature and diminished oxygen levels would have less effect directly as apposed to environmental changes and those that could not adapt to them) and diminished resources. While the ocean fish and plants, land plants and animals that were large and/or in the areas where the methane hydride had higher concentrations, the effects of diminishing resources in their environment if not poisoning would cause the most damage. Even when the methane hydride washed out of the air (Methane can stay in the atmosphere up to 11 years), it would have left various weakened species as well as accelerated the climate change that had been occurring for the last10 million years.
There is also the fact that for some distance below the K-T Boundary there are no fossils. This in itself would lend anyone to believe that the extinction event occurred prior to the Impact event. Except for The Signor-Lipps Effect states that evidence of extinction my come before the actual extinction but how long before the event would the effect take place? If there were an instant mass extinction by an impact event there should be some evidence (i.e. massive amounts of dead carcasses all together or even by themselves are not found). Why do we find dinosaur fossils prior to the impact event but not at the impact (the Chicxulub event killed and then destroyed all the dinosaurs and their evidence) layers?
If plants, animals and ocean species go extinct by this impact event, why no interruption in some of the insect and frog species, that would have been affected more by a worldwide asteroid impact event and acid rain.
The fact that, many other large object impacts events have occurred on earth without an extinction event occurring with them, makes this event suspect. The fact that Impact events occurred near the same time as an extinction event occurred does not necessarily link it. The likely hood of an impact event that caused the mass extinction (of only a select 60% percent of the species on land, in the sea and air) even the size of the Chicxulub (110 mi) event seems not very likely or at least not with fire raining, acid raining event that has been described. I feel that it is very unlikely the killer was the Impact Event. There are several other, larger impacts events occurring about the same time as the Chicxulub event among these are the Boltysh crater, a 24 kilometers (15 mi) diameter impact crater in Ukraine (65.17 ± 0.64 Ma), and the Silverpit crater, a 20 kilometers (12 mi) diameter suspected impact crater in the North Sea (60–65 Ma). Other craters that may have formed in the Tethys Ocean have been obscured by tectonic events, like the relentless northward drift of Africa and India. Maybe the impacts turned the climate changes around allowing the cooling of the environment; so rather than being a killer event it could be a seed of life.
The heating up of the atmosphere had many causes. The Caribbean large igneous province flood Basalt eruption from 139 to 69 million years ago with a total volume, which has been estimated approximately 4 x 106 km³. The Brito-Arctic province, the first occurred ~61 million years ago with 2 x 106 km³ in total volume. Then the Deccan Trapps right at the 65 million year mark with a present volume of directly observable lava flows estimated to be around 512,000 km³. The estimated are the original lava flows were as large as 1.5 million km², approximately half the size of modern India. These events caused massive amounts of gases to be vented into the atmosphere as well as the heat being vented raising the temperature. No Flood Basalt Events are Antipode to the Chicxulub Event there for probably not antipodally related but occurred at the same time range as the extinction and Chicxulub event occurred.
The Flood Basalt Eruptions did not cause the extinction event but the heating of the atmosphere was their part in the extinction event. Due to the flood basalt eruptions just prior to and during the extinction event (all having occurred at least in part within 5 million years of the extinction event) would be releasing large quantities of fresh water, locked up in ice caps and glaciers into the Ocean. This would slow then stop the Ocean Conveyor. This would allow the deep-sea water to heat enough to release the Methane Hydride layers. No matter what the methane layers would have released because of the temperature rise in the Ocean. The temperature of the atmosphere would have trapped a large amount of water in vapor and clouds.
There is also evidence indicating a lowering of the ocean levels (here is a real curiosity the glaciers and ice caps are melting but geologic evidence seems to indicate the ocean levels were lowered. This might be due to the mass loss of the Methane Hydride layers, lowering the level of the ocean floor (water levels depend on the amount of water available and the size of the collection bowl the liquid is held in) and levels of moister in the atmosphere (a heavy cloud layer). Life that was not affected did not exist at this time everything was affected, but only a few made it through the changes.
What probably occurred is that the environment changed so dramatically that those that could not adapt died out while others were weakened and/or overcome by climatic changes and became prey or carrion. Dinosaurs having adapted over millions of years became specialized in what they ate and how they acted. Like what we have today, there are certain creatures that only eat a specific food (i.e. The Koala Bear). The Koala Bear is a perfect example. They can only eat from certain eucalyptus tree not just any eucalyptus tree.
Over millions of years prior to the extinction, the climate was changing. As with any climate changes the environment changes, bringing on a change in the biodiversity. Certain plants start to die out, found in smaller and smaller quantities or only in small pockets. No matter which way each of the lower plant and animal species were changing the larger dinosaurs were not. The longer a species is able to maintain a status quo in their environment, food source, and way of life the longer it takes them to modify and change these parameters. The world was changing faster than the dinosaurs could change. As the lower plant and animals were able to modify themselves to the changing environment the dinosaurs were real laggers. Those that could adapt or the environmental changes did not effect their environment or resources survived. The food chains for many creatures broke, changed or at least diminished as well as their environments were changing, though the interior was still arid lush forests, swamps and savannas along the coast the environment gave way to a dryer more arid climate. Plants, animals and ocean creatures needed to adapt to their new environment. A small band of life was able to make it through, omnivores, insectivores and carrion-eaters, on land those that ate anything and everything and those that ate carrion, weighting under 50 lbs., are the winners and survived the extinction event.
The ocean is different only those creatures that were deep-water creatures or interacted with them went extinct. If you cannot evolve then you go extinct and the environment was changing so much that many creatures were unable to adapt to their new environment or resources. With the Ocean Conveyor and Methane Hydride release, the Oceans are the first to see the changes certain species of lower organisms are devastated by the changes in the Ocean temperature as well as the atmospheric climate. The start of the extinction starts on a microscopic level and starts to spread. Everything links together in a great symphony of life but is stacked like rows of dominos. As the lower life, starts to change or die the creatures in the next level up start losing their food supply and the dominos start to fall. Because the extinction event in the ocean had been going on longer than on land is the reason that more extinctions occurred in the ocean than on land.
When a species starts to be weaken by environmental changes they become susceptible to disease and plagues, which they cannot then defend against. Those species that are dependant on these creatures for food then have to start to change their food supply or die. If the species cannot change then they start to weaken and as the changes progress they start in spiraling down towards extinction. Diseases, which could have been around for millions of years, (generally they were able to fight off these infestations until their environmental system weakened them) could now disseminate their population.
To put the extinction event pivoting on a single event that did not sanitize the earth but just picked and chose the creatures to go extinct without explanation is not a good working hypothesis. The release of the Methane Hydride Layer, Sea Level changes, Climatic changes, Asteroid Impacts, Flood Basalt eruptions all pull together to change the environment. These changes had been taking place over the last 10 million years prior to the extinction event and near the end it reached a tipping point where all the changes would pickup momentum and the extinction would have accelerated. The event is a culmination of numerous events (some probably will never be know until we get a time machine to go back in time and see for ourselves) but the ultimate cause is environment.
The fact that almost everything over 50 lbs. went extinct lets one see the real issue, FOOD. Omnivores, insectivores and carrion-eaters are the creatures that survive. This show that only those that could eat everything and anything or rotting flesh lived. Major environmental changes caused plant and animal species to die off and birthing and flowering cycles to disrupt there by causing a FOOD shortage so the dinosaurs starved to death and nothing else.
If everything else is ruled out, no matter how improbable what is left is the answer. Nothing occurred that did not have a preceding or interconnecting event that initiate and/or helped the next or concurrent event along. To try to associate a global event to a single event shows a myopic view of the world and science. I am not saying that this or any impact event does not have any effect on the environment but that they are only part of the event and not the whole event.
If anything, the Impact event actually marked the end of the extinction event, and may have been a major fact in the recovery of life.
I think you're right. The asteroid theory indeed is the one most acceptable till now 
