I was interested to see that the Valdes Peninsula has been suggested as a connection for Magellan - "Visited 1520". Having been there I was surprised to see this as I hadn't come across it before and no local memorial/mention etc that I know of exists of him having done so!
I have checked on Google and found this account of the voyage in that area at http://www.fordham.edu/halsall/mod/1519magellan.html
"This source of this account is a transcription from the paper-book of a Genoese pilot," who came in the said ship, who wrote all the voyage as it is here. He went to Portugal in the year 1524 with Dom Amriqui de Menezes. ..........They sailed from this Rio de Janeiro on the 26th December, and navigated along the coast to make the Cape of St. Mary, which is in thirty-four degrees and two-thirds; as soon as they sighted it, they made their course west-northwest, thinking they would find a passage for their voyage, and they found that they had got into a great river of fresh water, to which they gave the name of river of St. Christopher, and it is in thirty-four degrees, and they remained in it till the 2nd of February, 1520."
Presumably the great freshwater river of St Christopher at around 34 degrees of latitude is the Plata (and they would indeed have needed to go south to c34 degrees and two thirds round Montevideo before going back north into the true river)?
It continues ".....and further on to the south they discovered a point which is in the same river more to the south, to which they gave the name of Point St. Antony; it is in thirty-six degrees, hence they ran to the south-west, a matter of twenty-five leagues, and made another cape which they named Cape St. Apelonia, which is in thirty-six degrees; thence they navigated to the west-south-west to some shoals, which they named Shoals of the Currents, which are in thirty-nine degrees; and thence they navigated out to sea, and lost sight of land for a matter of two or three days, when they again made for the land, and they came to a bay, which they entered, and ran within it the whole day, thinking that there was an outlet for Maluco, and when night came they found that it was quite closed up, and in the same night they again stood out by the way which they had come in. This bay is in forty-four degrees; they named it the island of St. Matthew"
The "outlet to Maluco"
which they hoped to find refers to the Moluccas which they were hoping to reach by going west"Thence they navigated along the said coast, and arrived on the last day of March of the year 1520 at the Port of St. Julian, which is in forty-nine and one-third degrees, and here they wintered, and found the day a little more or less than seven hours.
" On 24 August they resumed their voyage south.
St Julian still exists and its latitude is indeed 49.3 degrees south! (Good for Magellan's navigation skills - but we wouldn't have expected anything less I guess!)
Now the latitude of Peninsula Valdes is between 42 and 43 degrees south. The above description states that the ship went "out to sea"
and "lost sight of land for a matter of 2 or 3 days"
between the "Shoals of the Currents" at 39 degrees and a "closed bay" at 44 degrees which they named "The Island of St Matthew". 44 degrees south is at around Punta Tombo which is today the site of a well touristed penguin colony a 2-3 hour drive south of Puerto Madryn and the southernmost parts of Valdes Peninsula.
So, the question is :- Given Magellan's very accurate siting of Puerto San Julian (and indeed other locations which are recognisable today such as the Plate) is he likely to be wrong about the point at which he returned to land after going out to sea at 39 degrees.
A "worrying" aspect however is that he found a large bay with no exit ("was quite closed up
") and there is no obvious large closed bay at Pta Tombo or anywhere around 44 degrees south. There is today the "Golfo San Matias" between 41 and 42 degrees south and just north of Peninsula Valdes! Could that be the same place as the island of St Matthew albeit at a more northern latitude than Magellan's records?
I would be very interested to hear of any direct evidence that Magellan visited/saw Peninsula Valdes and/or its immediate seas.