No, Samatha alone can't reach Nirvana; even Vipassana can't; neither Nirvana necessarily produced by any Dhyana. Although recorded in the Vinaya Uppalavanna was entering the 9th Dhyana when staying in the Dark Forest where 500 robbers happened also tracked there, she was not entering Nirvana, she arose from the Dhyana the next morning. The 9th Dhyana called the "extinguishing" meditation (滅盡定) was the Buddha's unique discovery, he had learnt the 8 Dhyanas from his teachers that were known and practiced by the heretics at his time.
I read from my sources Samatha (止) and Vipassana (觀) are always going together in Dhyana, they can't happen on its own, like a hand with the palm and back. Samatha is taking a passive approach, when thoughts arise, abandon that thoughts, closely observes any thought arose abandoned immediately - present of mind (not absent of mind, think of what is absent-minded, the opposite); Vipassana is taking the active approach, focus and work on the chosen meditation object, alert and patiently waiting for revelation.
I've not heard that the three characteristics are to be considered as the rule to be obeyed in all meditation practices. They are the truth Buddha obtained in his own Prajna quest, he just told you that are the correct answers. But to learn, you have to work out the same answer. As a student working out the equation by doing computing, using calculator to output an answer or copying from your classmate doesn't mean you know the answer, you must be able to do the calculation on your own, then you obtain the answer - the Dharma, else they are just terms, vocabularies. So, you may choose one of the characteristics as your object to work your Vipassana on it. Personally I found that a visual object is easier to work Vipassana on, rather than concept. Maybe I'm just a beginner not knowing the sophistication of meditation yet. Samatha can't derive Prajna, it is just a background building for Vipassana to set on working, Prajna obtained by Vipassana. Even the Anapana meditation included Samatha and Vipassana, Samatha as setting mind to the breathe, the breath is also the object in Vipassana.