Disclaimer: I’m not an archaeologist, so this is an answer written from a general perspective of an academic.
It’s certainly “plausible” for you to do a PhD if you are highly motivated and have clear goals. But you need to understand that there isn’t such a thing as a “ticket to the PhD”. The only kind of ticket is hard work, and writing a thoughtful application that convinces the people in the program that you have high potential to succeed in, and bring value to, their program.
Assuming that any particular skill or set of skills that you have will be your “ticket” in would be a serious mistake in my opinion. First, the skills that you say you have are far from uncommon, and not particularly difficult to acquire (unless we’re talking seriously technical stuff like trimix diving, which I suppose may be useful in some specialized branches of marine archaeology). Second, I’m concerned that you are more focused on the PhD involving outdoor skills and activities than on what the PhD is actually about. Imagine an archaeologist reading your personal statement where you say you want to do research in archaeology “or maybe some other discipline where outdoor skills are strongly required”. Well, you could be the world’s best outdoorsman but if you don’t show a passion for the specific discipline you are applying to, I doubt your application will rank very highly (and even if you don’t write a sentence like this one that explicitly gives away your lack of attachment to the specific discipline, it will likely show in other more subtle ways). Besides, if you lack that kind of passion, I think you might want to reconsider the whole idea of a PhD. A PhD is hard enough to do for those who do have the passion for the topic they are working on — it is that passion that will get them through the hundreds or thousands of hours of boring grunt work, sitting in offices and seminar rooms, data analysis etc, that a PhD involves in addition to the “fun” field trips. If all you want are opportunities to do some fun science outdoors, you will likely be disappointed.
With regards to the age issue, another issue of possible concern to me is that you say “I'm aware I'm about to take place of someone younger”. This suggests to me that you potentially view yourself as unworthy of a spot in the PhD program, possibly due to your age. That’s not a helpful mindset to have. If you have the passion and think you have something unique to contribute, then you should apply. But you should not be thinking of yourself as “taking the place” of anyone — that’s another sign to me that you may lack real drive and passion for the journey that is the PhD. Your age is what it is, and gives you a perspective on life and abilities that are different from those of someone younger, for better and for worse. The people reviewing your application will surely have their own ideas about what it means and how it factors into the context of a PhD program in their area. There’s nothing you can do to eliminate this factor, but from your end I’d encourage you to at least not sabotage yourself by explicitly making age an issue where it may not be one at all.
Hope this gives you some things to think about, and good luck!
