It's unclear whether the 200,000 tons of meteoric ore in the valley were from a single large impact, or from a large number of smaller impacts at different times, although Hooper's comment "there are impact craters everywhere" might suggest the latter (unless the craters were from a bunch of fragments of a larger meteor that started to break up in the atmosphere). If it was from many smaller impacts at different times, then the total amount of meteoric ore across the entire world would probably be in the billions of tons, given that it seems unlikely meteors would hit one area far more frequently than other areas, and that the area cleared by the pyrosonic was probably at most a few hundred square kilometers (the exact blast radius wasn't given, but Hooper mentioned to Lucas as they were driving away that they needed to go another 3 kilometers before clearing the blast zone, so if we assume for example a blast radius of 10 kilometers, the circular blast zone would have an area of 314 kilometers squared), while the current area of all land on Earth (probably not too far from what it was in the world of Terra Nova) is around 150,000,000 square kilometers.
According to p. 87 of this book, over 100 million years the total mass of material deposited on Earth by meteors may be around 1,000,000 million tonnes, or 1 trillion tonnes (a "tonne" is a metric ton, with a mass of 1000 kg, while a U.S. "ton" is about 907 kg). However, the majority of that reaches the surface in the form of microscopic dust rather than larger fragments, as discussed on p. 77-78 of this book (also, p. 876 of this book mentions that outside of Antarctica, "meteorites are generally completely weathered away in 10^4 - 10^5 years", i.e. even a larger fragment would be ground to dust by natural processes in 100,000 years or less). If "meteoric ore" is taken to indicate larger rock-sized chunks rather than just dust in the soil (which is suggested by the image in the main article), 200,000 tons of such chunks in one area would be quite unprecedented by modern standards. As discussed here, the single impact that left the greatest mass of fragments was "El Chaco" in Argentina, with the fragments having a mass of just over 100 tonnes. And according to p. 260 of this book, the total mass of all iron meteorites recovered by humans is around 500 tons, vastly less than the amount of meteoric ore Hooper said could be found in a single valley.
The writers of Terra Nova might be working with the premise that meteor and asteroid impacts are simply far more common in the world of Terra Nova than in our modern world, an idea also suggested by the large meteor impact in "Nightfall". Perhaps the reasoning is that since the dinosaurs were likely driven to extinction by a large asteroid impact, it must have been a more dangerous time for impacts in general. However, if we assume the world of Terra Nova is supposed to be an alternate timeline that branched from our own during the dinosaur age, rather than a wholly separate parallel universe with only coincidental resemblance to our own past (see the discussion in The Probe/Science & Speculation), then this would be inaccurate: in fact, the rate of meteor impacts during the dinosaur age is not thought to have been higher than today, and may even have been somewhat lower (so the storyline of "Nightfall" would be just as unlikely an occurrence as a large meteor causing an EMP in a show set in the modern world, say "Law & Order"). For example, see this page which discusses a scientific paper that analyzed a large number of craters of various ages, with the results of the analysis being that "either that the Earth is as likely to suffer a major impact now as it was in the past, or that there has been a slight increase impact rate events over the past 250 million years." On the possibility that the rate of meteor impacts has actually increased over the last few hundred million years, the original paper says in the "Discussion" section on p. 14 that some other studies have also shown evidence of such a trend: "These results could be explained by a decreasing probability of preservation/discovery for older craters of size 5–35 km. However, studies of lunar cratering suggest that the cratering rate during the past 500Myr was about twice as high as the average over the past 3.3 Gyr (e.g. Shoemaker 1983). More immediately relevant is the study of McEwen et al. (1997), who concluded that the cratering rate has increased up to the present by a factor of two during the past 300Myr." (300Myr=300 million years, and 3.3 Gyr = 3.3 billion years)