EVIDENCE FROM THE CITIFIELD STADIUM SITE, QUEENS, NEW YORK CITY, NY OF GLACIAL READVANCES DURING RECESSION FROM THE LAST GLACIAL MAXIMUM

Stanford (2010) lines up the NYC recessional moraines formed during retreat from the LGM with the EZ and M1 positions mapped in NJ. He states that in NJ there is evidence of multiple short readvances particularly along these 2 lines. Geotechnical investigations from locations in NYC, including the Citifield Stadium site situated at the northern end of Flushing Meadows in Queens, NY, also indicate that there were readvances along these recessional moraines, along with a change in sediment source (and direction of glacial flow) associated with the last major stand/readvance in the city.

Below Flushing Meadows an ancient shift in Hudson River flow cut a now 300+’ deep channel through Cretaceous soils down to the underlying bedrock. During the Pleistocene an Illinoian and 2 Wisconsinan (earlier Ronkonkoma, then LGM Harbor Hill) age glacial advances over the region filled the valley with assorted glacial deposits.

Directly beneath Citifield the Cretaceous Raritan Clay is overlain by extremely dense till and outwash sand (possibly from the Ronkonkoma advance). These soils were glacially loaded and scoured out to approximately El. -190’ by overriding ice (likely from the LGM advance). To the south, the Harbor Hill terminal moraine formed a dam across the channel at the southern tip of Flushing Meadows, allowing a glacial lake to develop in the valley as the ice receded. At the southern end of the Citifield site the valley filled in with varved silt and clay. Heading northward, layers of outwash start to appear, eventually becoming the dominant soil type. Much denser soil below major strata breaks (at roughly El. -150’, -120’ and -85’) indicates the outwash is associated with glacial readvances, likely at least 3 below Citifield, during the overall retreat.

At the far northern end of Citifield the last readvance is also marked by a change in the color of the soil and is associated with the nearby kame deposit shown just to the NE on the Merrill & Others (1902) NYC Folio. The same yellow brown color is seen in the ablation till over transported basal Cretaceous clay found in the minor readvance that flowed down the East River along western Queens and Brooklyn (Moss 2011 & 2012). By the time this last stand and readvance took place the glacial flow and sediment source had shifted away from the previously dominant northwest to a more northeasterly direction.